Mobility platform for autonomous navigation in the workplace

Abstract

The mobility platform is configured to perform one or more tasks at a work site including a first passive landmark and a second passive landmark. The mobility platform may include a chassis, a drive system supporting the chassis, a first laser range finder disposed on the chassis at a first location, a second laser range finder disposed on the chassis at a second location, and at least one processor. The at least one processor may be configured to determine a position and attitude of the chassis based on a first distance measured by the first laser range finder between the first location and a first known landmark position, a second distance measured by the second laser range finder between the second location and a second known landmark position, and yaw angle information from at least one of the first laser range finder and the second laser range finder.

Description

[Technical Field]

[0001] Field FIELD OF THE INVENTION

[0001] The disclosed embodiments relate to mobility platforms configured to perform one or more tasks at a work site and related methods of use. [Background technology]

[0002] background

[0002] Several attempts have been made to deploy service areas for autonomous or semi-autonomous systems capable of performing area coverage tasks. These conventional systems typically employ beacon navigation systems that require powered navigation equipment external to the autonomous or semi-autonomous system to be placed at known locations on the work site. Alternatively, conventional systems require the use of external positioning sensors, such as a Global Navigation Satellite System (GNSS), e.g., a Global Positioning System (GPS). Summary of the Invention [Means for solving the problem]

[0003] overview

[0003] In some aspects, the techniques described herein relate to a mobility platform configured to perform one or more tasks at a work site including a first passive landmark located at a first known landmark location and a second passive landmark located at a second known landmark location, the mobility platform including a chassis and a drive system supporting the chassis, the drive system including at least two wheels and configured to move the mobility platform within the work site, a first laser rangefinder disposed on the chassis at the first location, and a second passive landmark located at a second location different from the first location. and at least one processor configured to acquire a first passive landmark with the first laser range finder, acquire a second passive landmark with the second laser range finder, determine a first position of the chassis based on a first distance measured by the first laser range finder between the first position and the first known landmark position and a second distance measured by the second laser range finder between the second position and the second known landmark position, and determine a first attitude of the mobility platform based on first yaw angle information from at least one of the first laser range finder and the second laser range finder.

[0004]

[0004] In some aspects, techniques described herein relate to a method for operating a mobility platform at a work site, the mobility platform including a chassis, a first laser rangefinder positioned at a first position on the chassis, a second laser rangefinder positioned at a second position on the chassis, and a drive system, the method including acquiring a first passive landmark positioned at a first known landmark position with the first laser rangefinder, acquiring a second passive landmark positioned at a second known landmark position with the second laser rangefinder, determining a first position of the chassis based on a first distance measured by the first laser rangefinder between the first position and the first known landmark position and a second distance measured by the second laser rangefinder between the second position and the second known landmark position, and determining a first attitude of the mobility platform based on first yaw angle information from at least one of the first laser rangefinder and the second laser rangefinder.

[0005] In some aspects, a method for placing landmarks within a work site includes acquiring obstacle information within the work site, calculating, with at least one processor, a drive path for a mobility platform through the work site based on one or more tasks performed within the work site at one or more task locations, calculating a first landmark location for a first passive landmark within the work site, calculating a second landmark location for a second passive landmark within the work site, calculating, for each location on the drive path, a line of sight between the mobility platform and the first passive landmark at the first landmark location and a line of sight between the mobility platform and the second passive landmark at the second landmark location, calculating whether there is a portion of the drive path with line of sight to both the first passive landmark and the second passive landmark, and upon determining that there is a portion of the drive path with line of sight to both the first passive landmark and the second passive landmark, calculating a third landmark location for a third passive landmark at the work site. The method may also include informing a user of the first landmark location, the second landmark location, and the third landmark location.

[0006]

[0006] In some aspects, techniques described herein relate to a method for operating a mobility platform at a work site, the mobility platform including a chassis, a first laser rangefinder disposed on the chassis, and a drive system including at least one wheel, the method including acquiring a first passive landmark with the first laser rangefinder, moving the mobility platform along a drive path with the drive system, altering a first rangefinder pitch of the first laser rangefinder to maintain the first laser rangefinder in a first target altitude range on the first passive landmark as the mobility platform moves along the drive path, determining a chassis pitch of the mobility platform for each position of the mobility platform along the drive path based on the alteration of the first rangefinder pitch of the first laser rangefinder, and determining an altitude of the work site at at least one wheel based on the chassis pitch for each position of the mobility platform along the drive path.

[0007]

[0007] In some aspects, the techniques described herein relate to at least one non-transitory computer-readable medium comprising instructions thereon that, when executed by at least one processor, perform the methods described in accordance with the illustrative embodiments of the present specification.

[0008]

[0008] It should be understood that the foregoing concepts and additional concepts discussed below may be arranged in any suitable combination, as the present disclosure is not limited in this respect. Furthermore, other advantages and novel features of the present disclosure will become apparent from the following detailed description of various non-limiting embodiments when considered in conjunction with the accompanying drawings.

[0009] BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component shown in various figures may be represented by a like numeral. For clarity, not every component is labeled in every drawing. [Brief explanation of the drawings]

[0010] [Figure 1]

[0010] FIG. 1 is a schematic diagram of an exemplary embodiment of a construction support system having a mobility platform for navigation at a work site. [Figure 2]

[0011] 1 is a top schematic view of an exemplary embodiment of a mobility platform chassis in a first state. FIG. [Figure 3]

[0012] 3 is a schematic top view of the mobility platform of FIG. 2 in a second state. [Figure 4]

[0013] FIG. 3 is a schematic top view of the mobility platform of FIG. 2 in a third state. [Figure 5]

[0014] FIG. 1 is a perspective view of an exemplary embodiment of a mobility platform. [Figure 6]

[0015] FIG. 6 is a side view of the mobility platform of FIG. 5. [Figure 7]

[0016] 1 is a side schematic view of an exemplary embodiment of a laser range finder of a mobility platform in a first position. [Figure 8]

[0017] 9 is a schematic side view of the laser range finder of FIG. 8 in a second position. [Figure 9]

[0018] 9 is a schematic side view of the laser range finder of FIG. 8 in a third position. [Figure 10]

[0019] FIG. 1 is a top view schematic diagram of an exemplary embodiment of a mobility platform and a plurality of passive landmarks. [Figure 11]

[0020] FIG. 1 is a top view schematic diagram of an exemplary embodiment of a mobility platform and a plurality of passive landmarks. [Figure 12]

[0021] FIG. 1 is a top schematic view of an exemplary embodiment of a mobility platform, a work site, and a number of passive landmarks in a first position. [Figure 13]

[0022] 13 is a top schematic view of the mobility platform, work site, and multiple passive landmarks of FIG. 12, with the mobility platform in a second position. [Figure 14]

[0023] FIG. 1 is a block diagram of an exemplary embodiment of a method for operating a mobility platform. [Figure 15]

[0024] FIG. 1 is a block diagram of an example embodiment for planning the operation of a mobility platform. [Figure 16]

[0025] 1 is a top schematic view of an exemplary embodiment of a mobility platform and an obstacle in a first position and attitude; [Figure 17]

[0026] 17 is a top schematic view of the mobility platform and obstacle of FIG. 16, with the mobility platform in a second position. [Figure 18]

[0027] 17 is a top schematic view of the mobility platform and obstacle of FIG. 16, with the mobility platform in a third position. [Figure 19]

[0028] 17 is a top schematic view of the mobility platform and obstacle of FIG. 16, with the mobility platform in a third attitude and a second position. [Figure 20]

[0029] FIG. 1 is a block diagram of an exemplary embodiment of a method for operating a mobility platform. [Figure 21]

[0030] 1 is a schematic diagram illustrating an exemplary embodiment, a driving path and lines of sight to two landmarks. [Figure 22]

[0031] FIG. 22 is a schematic diagram showing the drive path and lines of sight to the three landmarks of FIG. 21. [Figure 23]

[0032] FIG. 1 is a block diagram of an example embodiment for planning the operation of a mobility platform. [Figure 24]

[0033] FIG. 1 is a side schematic view of an exemplary embodiment of a mobility platform and landmark having a first chassis pitch. [Figure 25]

[0034] FIG. 25 is a side schematic view of the mobility platform of FIG. 24 having a second chassis pitch. [Figure 26]

[0035] FIG. 1 is a block diagram of an exemplary embodiment of a method for operating a mobility platform. [Figure 27]

[0036] FIG. 1 is a block diagram of an exemplary embodiment for operating a construction support system. DETAILED DESCRIPTION OF THE INVENTION

[0011] Detailed Description

[0037] Construction productivity, measured by value created per labor hour, has been steadily declining in the United States. This low productivity, coupled with a shortage of artisan labor and rising labor costs, has significantly impacted the construction industry. While some efforts have been made to automate or semi-automate tasks on worksites (e.g., construction sites, buildings, rooms, etc.), these traditional systems require constant human supervision, are susceptible to navigation errors, and have limited maneuverability in tight spaces, all of which limit the ability of such traditional systems to perform useful tasks on the worksite. Additionally, many traditional systems require the placement of active, powered devices or beacons (e.g., RF-emitting beacons) to aid in navigation on the worksite, complicating the rapid, large-scale adoption of automation platforms. One task that is time-consuming and prone to inconsistency is marking the layout on the worksite floor.

[0012]

[0038] In view of the above, the inventors have recognized techniques for the design and operation of a mobility platform capable of supporting a wide variety of tools and capable of accurately and repeatedly navigating within a workspace to enable automated tasks to be performed using the tools. A system using a mobility platform to autonomously position tools within a construction worksite using one or more of the techniques described herein can improve construction productivity by overcoming one or more of the disadvantages of prior efforts to automate construction tasks. In particular, a mobility platform can be configured to navigate by using passive landmarks identifiable by the mobility platform that can simply be placed within the workspace. Such passive landmarks may lack communication equipment, making them inexpensive and easy for end users to place and configure. As discussed further herein, the mobility platform can navigate by monitoring its position relative to the placed passive landmarks. A mobility platform according to exemplary embodiments herein may include a marking device such that a layout can be marked on the worksite floor with high precision and accuracy.

[0013]

[0039] According to one aspect, a mobility platform can employ multiple sensors used to identify the location of similar objects located within a work site. The inventors have appreciated the benefits of a mobility platform employing laser range finders and odometry (e.g., from one or more odometry sensors) to determine a highly accurate and precise position of the mobility platform for performing one or more tasks within a work site at one or more task locations. In some embodiments, the mobility platform can include a first laser range finder and a second laser range finder. The first laser range finder and the second laser range finder can be configured to collect distance information between the respective range finders and passive landmarks located within the workspace. In some embodiments, distance information from the first laser range finder and the second laser range finder can be provided to at least one processor (e.g., a controller) of the mobility platform. The first laser range finder can be located at a first location on the mobility platform chassis. The second laser range finder can be located at a second location on the mobility platform chassis, the first location and the second location being different from each other. The mobility platform may be configured to determine a first distance between the passive landmark and a first location based on distance information from a first laser range finder and a second distance between the passive landmark and a second location based on distance information from a second laser range finder. Using the first and second distances, the mobility platform may determine an attitude of the chassis in a plane of the work site. In some embodiments, odometry may be used to determine predicted positions of the first and second locations and a predicted attitude of the chassis. The odometry may be based on odometry information obtained from one or more odometry sensors, including, but not limited to, one or more wheel odometers and an inertial measurement unit. The predicted positions and attitudes may be employed to track the one or more passive landmarks with the first and second laser range finders.As discussed further herein, range information from the first laser range finder and the second laser range finder may be employed to confirm, correct, or calibrate the expected position and attitude.

[0014]

[0040] According to another aspect, the mobility platform can acquire passive landmarks with a laser range finder to obtain useful distance information from the laser range finder. In some embodiments, acquiring a passive landmark refers to orienting the laser range finder relative to the passive landmark so that the laser range finder can make accurate distance measurements relative to the passive landmark. In some embodiments, the laser range finder can emit infrared and / or visible light toward the passive landmark (e.g., a laser). The light emitted toward the passive landmark can be reflected back to the laser range finder. The range finder can determine the distance to the passive landmark based on the travel time of the light emitted toward the passive landmark. Thus, the distance determination is based on precisely aiming the passive landmark so that the passive landmark, and not another object in the work site, reflects the light. In some embodiments, the mobility platform can be configured to sweep the work site with the laser range finder to collect sweep information. As used herein, "sweep" can be the angular movement of the laser range finder in the plane of the work site over a range of angles. In some embodiments, the angular range may be 45 degrees, 90 degrees, 180 degrees, 270 degrees, 360 degrees, or another suitable angle. The sweep information may include multiple distances measured over the angular range. In some embodiments, the mobility system may acquire passive landmarks and detect the shape of the landmark in the sweep information. For example, in some embodiments, the passive landmarks may be cylindrical, and the sweep information may include distance measurements corresponding to the cylindrical passive landmark's shape in succession. As another example, in some embodiments, the passive landmarks may have a rectangular prism shape, which may also be detectable based on the successive distance measurements in the sweep information. In other embodiments, any shape of the passive landmark may be employed, as the disclosure is not so limited. In some embodiments, detecting the passive landmark may include detecting a reflectance of the passive landmark greater than a reflectance threshold.For example, a passive landmark may be more reflective than the surrounding work site for a certain frequency of light, such that an increase in signal strength detected by a laser range finder may indicate that a signal is reflecting from the passive landmark. In some embodiments, detecting the passive landmark may include detecting a color of the passive landmark. For example, a passive landmark of a certain color may change the signal strength of the reflected light signal such that an increase or decrease in signal strength detected by a laser range finder may indicate a signal reflecting from the passive landmark. Once the passive landmark is acquired, the mobility platform may determine the location of the passive landmark and / or the distance between the location of the laser range finder on the mobility platform and the location of the passive landmark at the work site.

[0015]

[0041] According to yet another aspect, mobility platforms according to exemplary embodiments herein can employ passive landmarks for position tracking, verification, and calibration within a work site. In some embodiments, placement of passive landmarks at known points within a work site can be planned prior to operation of the mobility platform. The mobility platform can operate autonomously according to a drive path, which may include changes in position and / or attitude to enable the mobility platform to accomplish one or more tasks at one or more corresponding task locations within the work site. As discussed further herein, the drive path may be based on task efficiency and / or several alternative factors, including, but not limited to, progressive completion of a task field (e.g., tasks across a work site), consistent readability of markings (e.g., orienting text in the same direction), and reduced movement between tasks. In some embodiments, once the drive path is determined, a method for planning operation of a mobility platform can include determining landmark positions for multiple passive landmarks. In some embodiments, the passive landmarks can be positioned to maximize or increase line of sight between the passive landmarks and portions of the drive path. In this way, fewer landmarks can be employed to provide complete navigation coverage of a particular driving path. In some embodiments, the first and second passive landmarks can be located at predetermined locations (e.g., a corner adjacent to a periphery of the driving path, respectively) within the work site (e.g., a first landmark location and a second landmark location). The method can include, for each projected position of the mobility platform on the driving path, determining a line of sight between the mobility platform and the first passive landmark at the first landmark location and the second passive landmark at the second landmark location.If there is a portion of the drive path with line of sight to less than both the first and second landmarks (e.g., one of the first and second landmarks, or neither the first nor second landmarks), a third landmark may be placed within the work site at a third landmark location. The third landmark location may be configured to have line of sight to portions of the drive path that do not have line of sight to both the first and second landmarks. In some embodiments, this process may be repeated to ensure that enough passive landmarks are placed within the work site to ensure line of sight to at least two passive landmarks for any position and / or orientation on the drive path.

[0016]

[0042] According to yet another aspect, a mobility platform according to example embodiments described herein may be employed to determine (and optionally map) the altitude of a work site. In some embodiments, the laser range finder may be configured to change pitch to maintain the laser range finder at a desired altitude range above the acquired passive landmarks. As the mobility platform moves along the drive path, changes in the pitch of the laser range finder may correspond to changes in chassis pitch of the mobility platform. Thus, in some embodiments, a method may include determining chassis pitch for each position of the mobility platform along the drive path. From the chassis pitch, an altitude of the work site at the wheels of the mobility platform may be determined. In some embodiments, where the mobility platform includes four wheels, four altitudes corresponding to the respective positions of the four wheels may be determined. In some embodiments, a second laser range finder may be employed to determine chassis roll for each position of the mobility platform along the drive path. In this manner, the altitude of each wheel of the mobility platform may be determined based on the roll and pitch of the chassis at each position along the drive path. In some embodiments, the altitude information may be employed to generate a diagrammatic map of the work site.

[0017]

[0043] According to yet another aspect, a mobility platform can include a holonomic drive system for the platform to navigate a work site. The holonomic drive system can enable the mobility platform to move in three degrees of freedom (e.g., translation in a plane and rotation in a plane) so that a tool mounted on the mobility platform can reach the edge of the work site to perform one or more tasks. In some embodiments, the holonomic drive can enable the mobility platform to move omnidirectionally in three degrees of freedom. In one embodiment, the holonomic drive system includes four independently actuable and independently pivoting wheels to enable the mobility platform to translate in a plane, rotate about a central axis, or a combination of the two (e.g., three degrees of freedom). In some embodiments, the drive system of the mobility platform can include four wheel assemblies, each including a wheel configured to rotate about a wheel axis, a first actuator (e.g., a first motor) configured to rotate the wheel about the wheel axis, and a second actuator (e.g., a second motor) configured to rotate the wheel about a pivot axis perpendicular to the wheel axis. The first actuator and the second actuator may be independently controllable such that, when operated in correspondence with the other wheel assemblies, the wheel assemblies can move the mobility platform in any of three degrees of freedom. In other embodiments, more or less than four wheel assemblies may be employed, as the disclosure is not so limited. In some embodiments, each wheel of the mobility platform may include a wheel odometer configured to measure the distance traveled by the wheel. In some embodiments, the wheel odometer may be a rotary encoder. In another embodiment, wheel odometry may be based on the use of stepper motors to drive the wheels, and the rotational position and position change of the stepper motors may be determined.In some embodiments, the wheel assemblies may also include rotation sensors (e.g., rotary encoders, potentiometers, stepper motors, etc.) configured to provide information regarding the rotation of the wheels about their pivot axes. In combination, the rotation sensors and wheel odometers may provide information that allows the position and attitude of the wheels to be estimated as the mobility platform moves throughout a work site. Correspondingly, the position and attitude of the mobility platform itself may be estimated based on the information from the rotation sensors and wheel odometers.

[0018]

[0044] According to some embodiments, the construction assistance system can include a mobility platform and one or more communication devices. For example, the construction assistance system can include a mobility platform, a remote server, a local device, and / or a mobile device. The construction assistance system can include one or more processors that can generate task commands for controlling the mobility platform. These processors can be programmed to implement design file processing tools that generate relevant navigation information for the mobility platform from standardized computer-aided design (CAD) files of a worksite used in the construction industry, including, but not limited to, .csv, .dwg, .dxf, .dwg, .rvt, .nwd, and .ifc. The design files can be processed for existing or expected features at the worksite, such as survey control points, survey control lines, structural elements, or other structural features, which can be identified as one or more features or obstacles to be used during drive path generation and passive landmark placement. For example, in some cases, an "obstacle" may relate to a structural element of a building (e.g., a load-bearing wall, a column, a stairwell, an elevator shaft, etc.) that interferes with the movement of the mobility platform and / or the line of sight between the mobility platform and one or more passive landmarks located within the work site. Control points or control lines may be marked points within the work site (e.g., on the work site floor) and are conventionally used by surveyors as known points for relative measurements between other items placed or constructed at the work site. In some embodiments, passive landmarks may be configured to be located on control points or control lines. Design file processing tools may be implemented on the mobility platform, on a remote server in communication with the mobility platform, or both. In some embodiments, the server may be accessible via the Internet or other network to users who can upload CAD files and provide other input related to tasks performed autonomously.

[0019]

[0045] According to some embodiments, the construction assistance system may include a human-operated workstation located at the worksite to improve route optimization, calibrate the navigation controller, verify placement of passive landmarks, verify, add, or remove obstacles, modify the drive path in response to changes in the worksite, and / or potentially enable manual control. The workstation may communicate with the mobility platform and / or a remote server. Once the drive path is generated by the remote server and / or the mobility platform, it may be transmitted to a graphical user interface on the workstation for review by a human user. The user may reject the drive path and have the mobility platform and / or the remote server recalculate the drive path, manually modify the drive path, or accept the path. Upon initial or final acceptance of the drive path, the mobility platform may autonomously navigate along the drive path and perform its assigned task(s) at one or more task locations within the worksite. Such an arrangement may enable a human user to review the mobility platform's drive path before moving or completing any task and to fine-tune the path for changing conditions within the worksite.

[0020]

[0046] As used herein, a "passive landmark" refers to a landmark that lacks equipment that provides a navigation signal to a mobility platform. In some embodiments, a "passive landmark" can reflect a signal (e.g., visible and / or infrared light, such as a laser) originating onboard the mobility platform. In some embodiments, a passive landmark can be completely powerless, such that a passive landmark is a physical object without a power source. In some embodiments, a passive landmark can include an illumination source (e.g., one or more lights). The illumination source can be configured to illuminate the landmark to improve the reliability of identification by the mobility platform (e.g., by providing a consistently colored landmark for visual processing). In some embodiments, light from the illumination source can be received by the mobility platform to track the passive landmark or to identify the passive landmark relative to other objects in the work site. However, light from a passive landmark's illumination source need not be a navigation signal employed to determine the mobility platform's position relative to the passive landmark. In this way, since the navigation hardware resides only on the mobility platform and the navigation signals sensed by the mobility platform can be emitted on the mobility platform, the passive landmarks can remain relatively simple and inexpensive compared to the complex RF beacons or surveying equipment employed in conventional systems.

[0021]

[0047] The mobility platform of the example embodiments described herein may be capable of performing various tasks and services without a human user through the transportation, positioning, and operation of automated tools. Tasks that may be performed include translating a digital design into a real-world layout (e.g., accurately marking the location of certain architectural / engineering features on a site), material management (transporting materials and equipment to the appropriate locations), performing portions of an installation task (e.g., marking mounting locations, drilling holes, attaching hangers, fabricating materials, preparing equipment, etc.), and / or installing various building systems (e.g., wall systems, mechanical systems, electrical systems, plumbing systems, sprinkler systems, telephone / data systems, etc.). The mobility platform may be fitted with one or more tools, including, but not limited to, marking devices (e.g., printers, brushes, markers, etc.), material management and manipulation systems (e.g., arms, grapples, grippers, etc.), rotary tools (e.g., drills, impact wrenches, saws, grinders, etc.), reciprocating tools (e.g., saws, files, etc.), orbital tools (e.g., sanders, cutters, etc.), impact tools (e.g., hammers, chipping tools, nailers, etc.), and the equipment required to support them (e.g., compressors, pumps, solenoids, actuators, presses, etc.).

[0022]

[0048] The following embodiments describe various systems (e.g., mobility platforms) and portions of systems in terms of their state in three-dimensional space. As used herein, the term "position" refers to the location of an object or portion of an object in three-dimensional space (e.g., three translational degrees of freedom along Cartesian x, y, and z coordinates). As used herein, the term "attitude" refers to the rotational configuration (three rotational degrees of freedom—e.g., roll, pitch, and yaw) of an object or portion of an object.

[0023]

[0049] Returning to the drawings, certain non-limiting embodiments will now be described in further detail. It should be understood that the present disclosure is not limited to only the particular embodiments described herein, and that the various systems, components, features, and methods described in connection with these embodiments can be used individually and / or in any desired combination.

[0024]

[0050] FIG. 1 is a schematic diagram of one embodiment of a construction support system including a mobility platform 110 for navigation at a worksite. As shown in FIG. 1, the system may include one or more computer processors that interpret various types of data. The computer processors may be programmed to implement functions such as extracting information about the worksite from design files, receiving input specifying one or more tasks to be performed at one or more task locations, determining or executing a path for the mobility platform to traverse to perform the tasks, determining landmark locations for one or more landmarks, and generating commands for the mobility platform to perform the tasks to be performed. The processors may be co-located or distributed across multiple locations. In some embodiments, some processors may be on the mobility platform 110, while other processors may be in one or more remote devices that may be connected to the Internet or other wired and / or wireless communication networks.

[0025]

[0051] As shown in Figure 1, the mobility platform can navigate and operate autonomously or semi-autonomously and can communicate with one or more remote or local devices. In the embodiment of Figure 1, the mobility platform includes various controllers and sensors mounted on a chassis 112 that enable high-precision navigation within a work site based on passive landmarks located within the work site. In some embodiments as shown in Figure 1, the mobility platform 110 of Figure 1 includes a controller 130 having a motion control unit 132 and a tool control unit 134.

[0026]

[0052] The motion control unit 132 is configured to control a drive system including at least a first wheel 120A driven by a first actuator and a second wheel 120B driven by a second actuator (see, e.g., FIGS. 2-4). In some embodiments, the drive system is a holonomic drive system, which in the illustrated embodiment allows the mobility platform to move omnidirectionally in three degrees of freedom, as discussed further with respect to FIGS.

[0027]

[0053] The tool control unit 134 is configured to control the activation and / or movement of one or more tools mounted on the mobility platform 110. The tool control unit can issue one or more commands to an associated tool to perform one or more tasks. In the configuration shown in FIG. 1 , the mobility platform includes a marking device 140 mounted on a carriage 142 that allows the marker to reach the edge of the mobility platform chassis 112. The tool control unit is configured to control the movement of the marking device on the carriage and deposit ink, powder, or other effective marking material to lay out the work site according to a design file. The marking device can mark features within the work site, such as walls and floors, columns, and ceilings, in response to commands from the tool control unit. The carriage can position the marking device at the appropriate task location in response to instructions from the tool control unit. Other commands from the tool control unit can control marking parameters, such as line thickness, color, and material. In some embodiments, the carriage can move the marking device to allow it to reach a desired position relative to the chassis 112. In some embodiments, the carriage may be stationary and the marking device may not move. In some embodiments, the marking device 140 may be a printer configured to make multiple marks at once. An exemplary marking device 140 is further discussed with reference to FIG. 6.

[0028]

[0054] As shown in FIG. 1 , mobility platform 110 includes multiple sensors configured to acquire and / or output information about the mobility platform's surroundings so that the mobility platform can navigate autonomously using passive landmarks located or pre-existing within the work site. According to the illustrated embodiment, the mobility platform includes a first wheel odometer 146A, a second wheel odometer 146B, a first laser range finder 150A, and a second laser range finder 150B. As discussed further below, the information acquired and / or output by each of the sensors may be fused by controller 130 as the mobility platform moves through the work site. In some embodiments, information from first wheel odometer 146A and second wheel odometer 146B may be used for real-time navigation within the work site, including determining an estimated position and attitude of the mobility platform. In some embodiments, information from first laser range finder 150A and second laser range finder 150B may be used to ascertain the position and attitude of the mobility platform within the work site. In some embodiments, information from the first laser range finder 150A and the second laser range finder 150B may be employed to reset errors in the estimated position or attitude and may be employed to calibrate position and attitude estimates based on information from the first wheel odometer 146A and the second wheel odometer 146B. In some embodiments, an independent local position and attitude may be determined by integrating information from the first wheel odometer 146A and the second wheel odometer 146B, while a global position is generated by passive landmark measurements by the first laser range finder 150A and the second laser range finder 150B. In some embodiments, the independent local position may be based on odometry information, including measurements from sensors other than the wheel odometers, such as inertial measurement units.Comparison of independently generated local and global positions may allow the mobility platform to self-test its position accuracy and recalibrate one or more parameters used in local position determination as it navigates the work site. Any suitable number or type of sensors may be employed and their data fused, combined, or compared to improve the precision and / or accuracy of autonomous navigation at the work site, as the disclosure is not so limited. For example, an inertial measurement unit 144 may be employed in addition to or instead of wheel odometers. In such an embodiment, acceleration information may be integrated over time to determine changes in the mobility platform's position and / or attitude. Such calculations may be prone to errors, such as drift, which may be corrected by information from the first laser rangefinder 150A and the second laser rangefinder 150B.

[0029]

[0055] While a particular combination of odometry sensors is shown and described with respect to the embodiment of FIG. 1 (e.g., wheel odometers and an inertial measurement unit), other odometry sensors may be employed alone or in combination in some embodiments. Odometry sensors employed to obtain odometry information used in determining an estimated position and / or attitude in accordance with the methods herein may include, but are not limited to, one or more wheel odometers (e.g., rotary encoders, stepper motors, potentiometers, etc.), inertial measurement units, accelerometers, and optical flow sensors. In some embodiments, a single odometer sensor or sensor type may be employed. For example, in some embodiments, odometry information may be provided solely from one or more wheel odometers. As another example, in some embodiments, odometry information may be obtained solely from an inertial measurement unit. In other embodiments, multiple odometry sensors of different types may be employed and fused to provide odometry information.

[0030]

[0056] 1, mobility platform 110 also includes additional external devices that cooperate with controller 130 to enable the mobility platform to autonomously navigate and perform tasks at a work site. For example, the mobility platform includes storage 136, such as a hard drive, solid state drive, or other memory for storing instructions or other data, as well as radio 138, which communicates wirelessly with various local or remote devices via any suitable communication protocol (e.g., satellite, cellular, Wi-Fi, 802.15.4, etc.). Although the mobility platform of FIG. 1 communicates wirelessly, any suitable wired communication interface, such as a wired serial port, an Ethernet port, etc., may also be employed. The combination of storage and wireless communication allows the mobility platform to send, receive, and store data from one or more external devices, such as a remote server 200 (i.e., a cloud server), a remote computer 230, a mobile device 240, or a local workstation 210 (e.g., a portable or handheld device such as a laptop, tablet, or cell phone, a desktop computer, or any other suitable device within wireless or wired range of the mobility platform and / or a network access point such that the workstation can communicate with or control the mobility platform from the work site). Such a configuration may allow files provided from the remote server to be analyzed by one or more of the remote server, remote computer, mobile device, or local workstation to generate paths, tasks, task locations, landmark locations, and other relevant information that the mobility platform 110 can use to autonomously or semi-autonomously perform tasks at the work site.

[0031]

[0057] As described above, mobility platform 110 of FIG. 1 is configured to communicate with multiple external devices to simplify autonomously navigating and performing one or more tasks. External devices that communicate directly or indirectly with the mobility platform include remote server 200, workstation 210, router 220, remote computer 230, and mobile device 240. In some embodiments, a remote server, which may be located in a data center as part of a cloud computing service, is employed to manage files used by the mobility platform to navigate and perform tasks. That is, the remote server can coordinate file management, route generation, route correction, task planning, and any other desired functionality. In some embodiments, route corrections can be coordinated on-board mobility platform 110. The remote server allows designers, such as contractors, consultants, engineers, and architects, to provide design files and task information that can be employed by the mobility platform. In some embodiments, the remote server can automatically generate driving routes for performing tasks at various locations within a worksite by extracting information from design files, such as 2D or 3D drawings or CAD files. An engineer, architect, or other remote worker can interface with the remote server from an industry-standard file management platform or by a web interface to which files are uploaded, either of which may be on a mobile device 240 or a remote computer 230. A graphical user interface 242 on the mobile device or a graphical user interface 232 on the remote computer can be used to transmit or download files from the remote server and modify the files using a CAD or Building Information Management (BIM) software platform. The file management system employed on the remote server can include a database for storing drawings, plans, and related data, and may also be suitable for providing users with a modification history of the files it stores.The remote server may also enable contractors, tradespeople, or other workers on-site at the work site to provide feedback on the route, task locations, landmark locations, or control parameters. In particular, the remote server may communicate with a workstation 210 having a graphical user interface 212. The graphical user interface 212 may allow a user on-site to review, modify, or reject the navigation and task plan generated by the remote server before the mobility platform begins operating autonomously. In some cases, the workstation may also be used to manually override or manually control the mobility platform. According to the embodiment of FIG. 1, router 220 may be configured as a modem, satellite, cellular tower, or other suitable interface suitable for coordinating data transmission between the remote server, the mobility platform, and / or the workstation.

[0032]

[0058] It should be noted that although a remote server 200 is shown and described with reference to FIG. 1, the disclosure is not so limited and any suitable server or processor may be used, including servers and processors located locally (e.g., onboard a mobility platform) or in close proximity to a work site.

[0033]

[0059] FIG. 2 is a top-view schematic diagram of one embodiment of a mobility platform 110 including a holonomic drive system that allows the mobility platform to move in three degrees of freedom and reach the edge of a work site. The holonomic drive system allows the mobility platform to position a tool mounted thereon within areas flush with the edge of a work site, such as around corners or obstacles that might otherwise require multiple movements to reach or might be inaccessible. The holonomic drive system allows the mobility platform 110 to translate in any direction within a plane and rotate within that plane to change the mobility platform's position and / or attitude. The drive system of the mobility platform 110 includes four wheel assemblies 118A, 118B, 118C, and 118D coupled to the mobility platform chassis 112. Each wheel assembly includes individual wheels 120A, 120B, 120C, and 120D coupled to individual supports 122A, 122B, 122C, and 122D. Wheels 120A, 120B, 120C, and 120D are coupled to first actuators 124A, 124B, 124C, and 124D, respectively, configured to rotate the wheels about wheel axes to move mobility platform 110. According to the embodiment of FIG. 2, each of wheel assemblies 118A, 118B, 118C, and 118D includes a respective pivot 126A, 126B, 126C, and 126D. Each of the four wheels rotates independently about its respective pivot, allowing the wheels to bend at any angle (e.g., from 0 degrees to 360 degrees) relative to mobility platform chassis 112. The wheel assemblies also include axial actuators 128A, 128B, 128C, and 128D, respectively, configured to rotate the respective wheels about their respective pivot axes. In some embodiments, the axial actuators may be servo motors. The axis actuators allow the wheel axis of each wheel to be adjusted (eg, pivoted) independently, allowing the mobility platform to move freely in three degrees of freedom.This configuration provides complete movement flexibility in a 2D planar environment (e.g., along a planar workplace floor), enabling the execution of complex movement patterns to accomplish certain tasks. As discussed further below, one such advantage is the ability to mark continuous curves on the workplace floor. While independently rotatable wheels are shown in FIG. 2, in other embodiments any suitable holonomic drive system, such as omnidirectional wheels, may be employed. In other embodiments, non-holonomic drive systems may be employed, as the disclosure is not so limited.

[0034]

[0060] According to the embodiment of Figure 2, mobility platform 110 includes a chassis 112 for mounting various tools or payloads. Chassis 112 is coupled to wheel assemblies 118A, 118B, 118C, 118D that support and move the chassis. The chassis may have multiple hard mounting locations that allow for modular mounting of tools or payloads to the mobility platform. An exemplary chassis is shown and further described with respect to Figures 5-6.

[0035]

[0061] Figure 2 is a schematic top view of mobility platform 110 in a first state, Figure 3 is a schematic top view of the mobility platform in a second state, and Figure 4 is a schematic top view of the mobility platform in a third state illustrating the degrees of freedom provided by a holonomic drive system including wheel assemblies 118A, 118B, 118C, and 118D. As shown in Figure 2, four wheels 120A, 120B, 120C, and 120D have parallel wheel axes. Thus, by rotating the four wheels with actuators 124A, 124B, 124C, and 124D, the mobility platform can move in the +X direction or the -X direction, as shown in Figure 2.

[0036]

[0062] As shown in FIG. 3 , the wheels are rotated to facilitate movement of the mobility platform along the +Y or −Y direction. That is, each of the wheel's rotational axes is driven by an individual axis actuator, so that the wheel axes are parallel to one another and rotated approximately 90 degrees relative to the state shown in FIG. 2 . Thus, the mobility platform can move in the +Y or −Y direction as shown in FIG. 3 by rotating the four wheels with actuators 124A, 124B, 124C, and 124D. To reach the state shown in FIG. 3 , the drive path may include commands specifying which wheel axis to rotate and the desired magnitude of rotation. Alternatively, the mobility platform's controller (e.g., motion control unit) may generate corresponding commands for each of the wheel and axis actuators to control the mobility platform to that position. In some embodiments, a server, motion control unit, or any other suitable processor or controller may control the mobility platform's movement using any suitable task commands, including combinations of the task commands described above, as the disclosure is not so limited. Thus, the mobility platform can easily move along either the ±X or ±Y directions.

[0037]

[0063] As shown in FIG. 4, the holonomic drive system is in a third state, in which the wheel rotation axes of the first wheel 120A and the third wheel 120C are aligned, and the wheel rotation axes of the second wheel 120B and the fourth wheel 120D are aligned and perpendicular to the axes of the first wheel and the third wheel. In the configuration shown in FIG. 2, the mobility platform can move in three degrees of freedom by changing the rotational direction of the wheels about their various rotational axes. Additionally, the state shown in FIG. 4 allows the wheels to be driven to rotate the mobility platform in a plane in either the +θ or −θ direction. Thus, the holonomic drive system can move the mobility platform along a first axis (±X), a second axis (±Y) perpendicular to the first axis, and can also change the orientation of the mobility platform about a third axis (±θ). The wheel axes can be adjusted without moving the mobility platform itself from its initial position, allowing the mobility platform to move in any of the three degrees of freedom from its initial position. For example, one or more axis actuators may adjust the axis of a wheel in response to commands from a motion control unit. Additionally, the attitude of the mobility platform may be changed without changing the position of the mobility platform, which may be expressed as a mean position (e.g., geographic center, center of mass) or other point position.

[0038]

[0064] According to the embodiment of Figures 2-4, the holonomic drive system may enable the mobility platform to move in any of the three degrees of freedom described above simultaneously. For example, the drive system may enable the mobility platform to move in the +X direction and the +θ direction simultaneously. Any combination of movement in any of the three degrees of freedom may be provided by the holonomic drive systems of Figures 2-4, as the disclosure is not so limited.

[0039]

[0065] FIG. 5 is a perspective view of an exemplary embodiment of mobility platform 110, and FIG. 6 is a side view thereof. As shown in FIGS. 5-6 , mobility platform 110 includes a chassis 112. Chassis 112 is supported by a drive system including multiple wheel assemblies 118A, 118B, 118C, and 118D. The wheel assemblies each include wheels 120, supports 122, wheel actuators 124, pivots 126, and swing actuators 128. The drive systems of FIGS. 5-6 are holonomic, allowing chassis 112 to move in any direction within a plane, as described above with respect to FIGS. 2-4 . The wheel assemblies may each include a wheel odometer configured to measure the distance traveled by the wheels.

[0040]

[0066] As shown in FIGS. 5-6 , mobility platform 110 includes controller 130 mounted on chassis 112 within controller housing 178. Controller 130 may include one or more processors configured to execute computer-readable instructions for performing example methods described herein. Controller 130 may include antenna 139, which may be used by radio 138 to enable the controller to wirelessly communicate with other external devices. In some embodiments, laser range finder 150 may include one or more processors. In some embodiments, the methods described herein, or portions of the methods described herein, may be performed by firmware on laser range finder 150.

[0041]

[0067] The mobility platform 110 of FIGS. 5-6 also includes a power source. The power source of FIGS. 5-6 includes a plurality of batteries 170. The batteries 170 may be modular, such that one or more batteries may be selectively coupled to the chassis 112 to power various components of the mobility platform 110. In the embodiment of FIGS. 5-6, the chassis 112 may be configured to accommodate up to eight batteries. Non-modular batteries may be employed in other embodiments, as the disclosure is not so limited. A wired power source may be employed in some embodiments, as the disclosure is not so limited. As shown in FIGS. 5-6, in some embodiments, the mobility platform may include one or more switches 176 that may be used by a user to selectively power the mobility platform.

[0042]

[0068] As shown in FIGS. 5-6 , the mobility platform 110 includes a marking device 140. The marking device 140 is located at the rear of the chassis 112. The marking device is mounted to a rail 143 of the chassis by a carriage 142. In the embodiment of FIGS. 5-6 , the marking device 140 does not move; the carriage, once set, forms a stationary connection between the marking device 140 and the chassis 112. In some embodiments, the carriage is configured to move up and down along the rail 143 to allow a user to adjust the height of the marking device 140. As shown in FIGS. 5-6 , a first marking device cable 172 and a second marking device cable 174 can be used to connect the marking device to the controller 130 and / or the battery 170 (or another power source). In some embodiments, the first marking device cable 172 may be used only for power. In some embodiments, the second marking device cable 174 may be used only for data transmission.

[0043]

[0069] In some embodiments, the marking device 140 includes at least one reservoir, at least one air compressor or pump, an electronic control system (ECS), and at least one printhead, all appropriately interconnected by tubes, hoses, pipes, valves, connectors, wiring, switches, etc. The reservoir can hold a sufficient amount of marking fluid for the printing toolkit to operate for a desired working period. The reservoir can be connected both upstream and downstream to the rest of the printing system to deliver the marking fluid to the next component necessary to control and execute the desired mark. In some embodiments, the reservoir holds the marking fluid, such as a pigmented ink, in a tank that is open to the atmosphere and can be manually filled from a bulk container of marking fluid, but can be pressurized when closed if desired. In some embodiments, the top of the reservoir can be connected by a tube, hose, or pipe to an air compressor or air pump, which pressurizes the headspace at the top of the reservoir above the marking fluid, thereby creating a positive pressure on the marking fluid and allowing it to be supplied through an ink supply tube, hose, or pipe that connects the bottom of the reservoir to one or more of the printheads. In some embodiments, the reservoir can remain open to the atmosphere, with the bottom tube, hose, or pipe connected to a pump that can suck fluid from the reservoir and supply it downstream to the printheads via the ink supply tube, hose, or pipe.

[0044]

[0070] In some embodiments, each printhead of the marking device 140 is configured to deposit marking fluid onto a printing surface. In some embodiments, the printhead may be formed with ink supply tubes connecting to a reservoir or pump, a manifold that distributes the marking fluid to key components within the printhead, and at least one piezoelectric pump that, when activated, displaces the marking fluid in small droplets. The piezoelectric pump may utilize a disk that is normally flat but that deforms into one of two positions upon activation: a draw position or a push position. In the draw position, positive pressure from the fluid in the ink supply tubes and manifold urges the marking fluid into the piezoelectric chambers. In the push position, droplets are forced out of the piezoelectric chambers and deposited on the floor. In some embodiments, an array of piezoelectric pumps is used, allowing droplets to be simultaneously deposited in columns, rows, columns, diagonals, or any combination thereof. Such an array enables the marking of complex shapes and patterns, including text.

[0045]

[0071] In some embodiments, the marking device 140 may also include an electronic control system having a processor configured to execute computer-readable instructions stored in memory. The electronic control system may be configured to command multiple printheads and at least one pump to deposit droplets of marking fluid in columns, rows, matrices, horizontal lines, vertical lines, diagonal lines, or any combination thereof. The electronic control system may also communicate with the controller 130 (e.g., tool control unit 134) of the mobility platform 110 to receive position and velocity information for coordinating the deposition of marking fluid. In some embodiments, the mobility platform and printing system may enable marking of text or other complex shapes or patterns. In some embodiments, the marking fluid is deposited while the mobility platform is moving. The electronic control system may interface with the mobility platform's task control unit to receive triggers that activate specific actions necessary to place precise markings on the floor. Additionally, the marking device may provide feedback to the mobility platform through the same interface to provide real-time information about the printer's performance and status. In this way, the marking device can be a self-contained system that automates the process of releasing marking fluid based on some external input related to timing, position, or other signals of the mobility platform.

[0046]

[0072] According to the embodiment of FIG. 1 , the printing capabilities provided by the marking device 140, and specifically the ability to print text, enable the marking device 140 to provide digitally replicated, unique information on the unfinished floor of a job site. When deployed on the mobility platform 110 of the exemplary embodiment described herein, the marking device can mark the intended locations of various building systems, components, and equipment, allowing contractors to accurately install their individual materials. While installation locations are currently marked manually using dots and lines, the marking device can have complex marking capabilities, including the ability to print text, which can be used to distinguish between contractors, communicate non-intuitive installation instructions (e.g., indicating material size, identifying specific parts or equipment, detailing configurations or orientations, and specifying installation heights above the floor), and identify prefabricated part numbers. The ability to communicate prefabricated part numbers may be desirable as prefabricated building techniques become more prevalent. Thus, the marking device of FIG. 1 works in conjunction with the mobility platform of the exemplary embodiments described herein to provide the ability to communicate exact installation location, exact part number, and exact installation attitude and configuration, enabling contractors to quickly and correctly install components in their intended locations.

[0047]

[0073] According to the embodiment of FIGS. 5-6, the mobility platform 110 includes two laser range finders 150. The first laser range finder is located at a first location 151A on the chassis. The second laser range finder is located at a second location 151B on the chassis spaced apart from the first location. The laser range finders are configured to measure distances from the first location 151A and the second location 151B to passive landmarks located within the work site. As discussed further herein, using two laser range finders at separate locations on the chassis enables the attitude of the chassis to be determined based on the distance and yaw angle measurements provided by the laser range finders. In the illustrated embodiment, the laser range finder 150 includes an emitter / receiver 152 configured to emit light through a lens 153 and receive reflected light from objects (e.g., passive landmarks) within the work site. The emitter / receiver is supported by a bracket 154. The bracket includes a base 158 configured to couple the emitter / receiver to the chassis 112. In some embodiments, such as that shown in FIG. 5, the laser range finder may be capable of movement in one or more degrees of freedom. As shown in FIG. 5, the laser range finder includes a pitch actuator 156 configured to rotate the emitter / receiver about a pitch axis. Additionally, the laser range finder includes a yaw actuator 160 configured to rotate the emitter / receiver about a yaw axis. The yaw actuator 160 may be configured to rotate the emitter / receiver in a plane parallel to the plane of the work site. In some embodiments, the pitch axis may be optional. In such embodiments, the emitter / receiver 152 may be capable of movement relative to the chassis 112 about only the yaw axis. Movement of the laser range finder and associated exemplary methods are further described herein with respect to FIGS. 10-14 and 24-25. The emitter / receiver 152 may be connected to the controller 130 via a power connection and / or a data connection 162.

[0048]

[0074] FIG. 7 is a schematic side view of an exemplary embodiment of a laser range finder 150 for a mobility platform in a first pose, FIG. 8 is a schematic side view of the laser range finder in a second pose, and FIG. 9 is a schematic side view of the laser range finder in a third pose. As shown in FIGS. 7-9, the laser range finder includes an emitter / receiver 152. The emitter / receiver 152 is configured to emit light through a lens 153 and receive reflected light from objects (e.g., passive landmarks) within the work site. The laser range finder can determine distance based on the time it takes for the emitted light to be received again at the emitter / receiver. The emitter / receiver is supported by a bracket 154. The bracket is coupled to a base 158 configured to couple the emitter / receiver to the chassis of the mobility platform. The laser range finders of FIGS. 7-9 are capable of movement with two degrees of freedom. As shown in FIGS. 8-9 , the laser range finder includes a pitch actuator 156 disposed within a pitch actuator housing 159 configured to rotate the emitter / receiver about a pitch axis. In particular, the pitch actuator 156 can rotate the bracket 154. Additionally, the laser range finder includes a yaw actuator 160 configured to rotate the emitter / receiver about a yaw axis. The yaw actuator 160 is configured to rotate the base 158 about the yaw axis. As shown in FIGS. 7-9 , the yaw actuator 160 can be disposed within a yaw actuator housing 161. In some embodiments, the pitch actuator 156 and the yaw actuator 160 can provide feedback information to at least one processor of the mobility platform related to the attitude of the emitter / receiver about one or more of the pitch and yaw axes. In some embodiments, the laser range finder can include one or more sensors (e.g., potentiometers, rotary encoders, accelerometers, etc.) that provide information regarding the attitude of the laser range finder relative to a chassis or worksite frame of reference.

[0049]

[0075] As shown in FIG. 7 , the emitter / receiver 152 is configured to change its orientation about the pitch and yaw axes based on forces applied to the emitter / receiver by the pitch actuator 156 and the yaw actuator 160. In the state shown in FIG. 7 , the pitch axis is parallel to the y axis and can always be parallel to the xy plane. Therefore, the pitch actuator 156 can adjust the angle of the emitter / receiver about the pitch axis in the +p or −p direction. In the state shown in FIG. 7 , the yaw axis is parallel to the z axis and can always be perpendicular to the xy plane. Therefore, the yaw actuator 160 can adjust the angle of the emitter / receiver about the pitch axis in the +θ or −θ direction. FIG. 8 shows the emitter / receiver 152 whose orientation has been changed in the +p direction relative to the state shown in FIG. 7 so that the emitter / receiver is tilted relative to the horizontal plane. FIG. 8 also shows the emitter / receiver 152 whose orientation has been changed in the +θ direction relative to the state shown in FIG. 7 so that the emitter / receiver is facing in a direction different from the xy plane.

[0050]

[0076] In some embodiments, such as those shown in FIGS. 7-9 , the laser rangefinder may include a camera 166. The camera may collect visual information about the work site. Information from the camera 166 may be provided to at least one processor of the mobility platform, which may use the information to identify passive landmarks for landmark acquisition. To identify passive landmarks, various image processing techniques may be applied to the information. For example, shape recognition, machine vision, or machine learning may be applied to the information obtained by the camera to recognize and identify passive landmarks. In some embodiments, the passive landmarks may be a color that may be distinguishable in the information provided by the camera. In some embodiments, the illumination source of the passive landmark may emit light that may be distinguishable in the information provided by the camera. In some embodiments, the reflectivity of the passive landmark may be distinguishable in the information provided by the camera. Because the camera 166 is mounted on the emitter / receiver 152, information regarding the frame of reference for the images obtained by the camera may be known based on the attitude information of the emitter / receiver. Similarly, the position of the camera may be known based on the position information of the associated mobility device. Thus, processing images obtained by a camera whose pose and position are known may enable at least one processor to estimate the positions of passive landmarks contained within the images.

[0051]

[0077] In some embodiments, the camera 166 may be used to “target” the emitter / receiver. For example, images from the camera 166 may be processed so that passive landmarks are identified in the image. Once the passive landmarks are identified, the emitter / receiver may be reoriented to center the passive landmark in the image or to position the passive landmark at a desired location in the image. Once the passive landmark is within a desired portion of the image, the emitter / receiver may be pointed toward the passive landmark. In some embodiments, the correct orientation of the emitter / receiver relative to the passive landmark may be confirmed with distance measurements from a laser range finder. In some embodiments, a camera may be located on another portion of the mobility platform, as the disclosure is not so limited. In some embodiments, the mobility platform may not include a camera or may not employ image processing to identify landmarks, as the disclosure is not so limited.

[0052]

[0078] FIG. 10 is a top schematic view of an exemplary embodiment of a mobility platform 110 and a plurality of passive landmarks 300A, 300B. As shown in FIG. 10, the mobility platform includes a chassis 112. The chassis includes a first side 114, a second side 115, a third side 116, and a fourth side 117. The orientation of the sides of the chassis may represent an attitude of the chassis 112. The chassis 112 may be supported by a drive system (see, e.g., FIGS. 5-6), which is omitted from FIG. 10 for clarity. The chassis may also support a marking device 140 configured to mark a work site floor.

[0053]

[0079] According to the embodiment of FIG. 10 , the mobility platform includes a first laser range finder 150A and a second laser range finder 150B. The first laser range finder is disposed at a first position R1 on the chassis 112 and configured to measure the distance between the first position R1 and an object within the work site. The second laser range finder is disposed at a second position R2 on the chassis 112 and configured to measure the distance between the second position R2 and an object within the work site. As shown in FIG. 10 , a first passive landmark 300A and a second passive landmark 300B are disposed at the work site. The first laser range finder 150A is pointed at the first passive landmark 300A, and the second laser range finder 150B is pointed at the second passive landmark 300B. Thus, the first laser range finder 150A is configured to measure a distance L1, indicated by the dashed line, between the first passive landmark and the first position R1. Similarly, the second laser rangefinder 150B is configured to measure a distance L2 between a second passive landmark, also shown by a dashed line, and a second position R2.

[0054]

[0080] The distances L1 and L2 can be used to determine the positions of the first position R1 and the second position R2 within a plane (e.g., the x-y plane) of the work site. As shown in FIG. 10 , information regarding the yaw angle θ of the first laser range finder 150A and the second laser range finder 150B can be measured (e.g., by one or more yaw angle sensors) relative to a reference yaw direction. In the embodiment shown in FIG. 10 , the reference direction can be parallel to the x-axis. This disclosure is not so limited; any suitable direction within the x-y plane can be employed in other embodiments. As shown in FIG. 10 , the first laser range finder 150A is positioned at an angle θ1 relative to the reference direction, and the first laser range finder 150B is positioned at an angle θ2 relative to the reference direction. Based on the angle θ1 and the distance L1, the x-y coordinates of the first landmark 300A can be determined using trigonometry. For example, the distance Y1, shown by the dashed line in the y-direction, can be determined as Y1 = sin(θ1) * L1. As another example, the distance X1 shown by the dashed-dotted line in the x-direction may be determined as X1 = cos(θ1) * L1. Thus, at least one processor of the mobility platform may receive the distance L1 and the angle θ1 and may be able to determine the location of the first position R1 in the x-y plane relative to the first landmark 300A. If the location of the first landmark 300A is known, the first position R1 may be determined. Similar to the first position, the location of the second position R2 may be determined based on the distance L2 and the yaw angle θ2. For example, the distance Y2 shown by the dashed-dotted line in the y-direction may be determined as Y2 = sin(θ2) * L2. As another example, the distance X2 shown by the dashed-dotted line in the x-direction may be determined as X2 = cos(θ2) * L2. Thus, at least one processor of the mobility platform may receive the distance L2 and the angle θ2 and may be able to determine the location of the second position R2 in the x-y plane relative to the second landmark 300B. If the location of the second landmark 300B is known, then a second location R2 can be determined. The same process can be completed to determine the location of any landmark whose laser rangefinder and location are known.With two locations on the chassis 112 fixed in place, the attitude of the chassis 112 can be determined as long as the two locations are uniquely identified and are not the same location (eg, spaced apart from one another).

[0055]

[0081] In particular, the distances L1 and L2 measured by the first and second laser range finders 150A and 150B are relative to the outer surfaces of the first and second passive landmarks 300A and 300B. In some embodiments, it may be desirable to measure the position relative to the point (e.g., control point) represented by each landmark. In some embodiments, such a point may be located at the center of the passive landmark. In the embodiment of FIG. 10, the first and second landmarks 300A and 300B are cylindrical, and therefore the center of each landmark is equidistant from the outer surface of the landmark from which the light measured by the laser range finders reflects. Thus, in some embodiments, the radius of the cylindrical landmark can be added to the measured distance L1 for use in determining the positions of the first and second positions R1 and R2. Such addition may be appropriate when the distances L1 and L2 are measured from the surface of the cylindrical landmark closest to the positions R1 and R2. However, there are situations in which such addition is inappropriate depending on the yaw angle of the laser range finders.

[0056]

[0082] As shown in the graph in Figure 10, the distance measured by a laser rangefinder can vary depending on the yaw angle of the laser rangefinder and the specific passive landmark. For example, if the yaw angle is not set properly, the measured distance may increase relative to the true distance between the landmark and the laser rangefinder. As shown in Figure 10, the distance d A is minimized when the first laser rangefinder 150A is aimed at the center of the first landmark 300A so that the outer surface of the first landmark is closest to the first position R1. AIn this case, when light from the laser range finder is no longer reflected from the first landmark 300A, the measured distance increases until a discontinuity occurs. In the graph of the first landmark 300A shown in FIG. 10, such discontinuity is represented as a gradual increase to infinite distance, but such an increase could be to another object in the work site or the range limit of the first laser range finder 150A. The graph shown in FIG. 10 for the first landmark 300A can represent sweep information. As shown in FIG. 10, the yaw angle θ B The distance d measured for the change B A similar graph can be shown for distance d, which represents the sweep information. B is minimized when the second laser rangefinder 150B is aimed at the center of the second landmark 300B so that the outer surface of the second landmark is closest to the second position R2. B Now, when the light from the laser range finder stops reflecting off the second landmark 300B, the measured distance increases until it becomes discontinuous.

[0057]

[0083] In some embodiments, during the landmark acquisition process, the processor can instruct the laser range finder to "sweep" the work site within a predetermined angle range while the mobility platform is stationary. The processor can obtain distance information similar to the graph of measured distance versus yaw angle shown in FIG. 10, which can be used to determine the appropriate yaw angle for the laser range finder. In some embodiments, to determine the location of a position on the chassis, the processor can orient the laser range finder to minimize the distance measured from a cylindrical landmark. At the minimized distance, the processor can add the radius of the cylindrical landmark to determine the distance to the center of the landmark. In some embodiments, the processor can identify the shape of the passive landmark in the distance measurement. For example, a partial elliptical shape, such as the one shown in the graph in FIG. 10, may correspond to a cylindrical landmark. The center of the landmark can be determined based on the specific shape. Other shapes of landmarks may also be identifiable, including prismatic, truncated, or curved passive landmark shapes. In some embodiments, successful acquisition may result in the laser range finder being pointed at the geometric center of the passive landmark in the x-y plane (or another point used as a known reference point for determining the location of the position on the chassis 112). In some embodiments, the landmark acquisition process may be completed before moving the mobility platform 110 (e.g., as part of a startup procedure). In some embodiments, the landmark acquisition process may be performed before the mobility platform performs any task at the task location. Such a configuration may be beneficial to ensure that the mobility platform is in the appropriate task location and in the correct attitude before performing a task. In some embodiments, the landmark acquisition process may be performed to calibrate and / or correct errors in position estimates from other sensor sources (e.g., acceleration integral, odometry, etc.). As discussed above, in some embodiments, a camera 166 associated with each laser range finder may be employed to perform the landmark acquisition process.The use of camera 166 can be an alternative to or in addition to other processes described herein (e.g., a "sweeping" process). In some embodiments, "sweeping" can be employed while the mobility platform is moving to ensure that landmarks remain acquired throughout the duration of the mobility platform's movement. In some embodiments, camera 166 can be employed to control a laser rangefinder to maintain acquisition of individual landmarks while the mobility platform is moving.

[0058]

[0084] In some embodiments, as the mobility platform 110 moves or changes orientation, the first laser range finder 150A and the second laser range finder 150B can track the first landmark 300A and the second landmark 300B, respectively. In some embodiments, the first laser range finder and the second laser range finder can be driven to track their respective landmarks based on feedback provided by other sensors on the mobility platform. For example, odometry information from at least one wheel odometer, an inertial measurement unit, an accelerometer, other sensors, or any combination thereof can be used to drive the laser range finders to track their acquired landmarks. In some such embodiments, the laser range finders may not provide internal feedback information, and therefore tracking may be subject to errors from other sources of position and orientation information. Thus, in some embodiments, the laser range finders can reacquire passive landmarks at fixed distances or time intervals while the mobility platform is moving (e.g., by stopping the mobility platform and performing a “sweep”). In some embodiments, the laser range finder reacquires passive landmarks at each task location to confirm its position and can make position or attitude corrections as needed to accomplish the task. In some embodiments, a camera 166 can be employed for feedback control of the laser range finder. In such embodiments, feedback from the camera 166 can be used to maintain landmark acquisition to ensure reliability of distance measurements. In some such embodiments, no reacquisition process or fewer reacquisition processes are performed compared to methods that include reacquisition at each task location or at fixed time or distance intervals.

[0059]

[0085] In some embodiments, "reacquire" or "re-acquisition" may refer to a method for ensuring that the laser rangefinder is properly oriented relative to the passive landmark for valid distance measurements. In some embodiments, re-acquisition may include re-locating the passive landmark according to methods described herein (e.g., sweeping, camera feedback, etc.). For example, during re-acquisition of a passive landmark, the acquisition process may be independently repeated, even if previously completed, to ensure that the laser rangefinder is correctly targeting the passive landmark.

[0060]

[0086] In some embodiments, the at least one processor may detect a discontinuity in the laser range finder's distance measurements (e.g., information from the laser range finder) while the mobility platform is moving, which may trigger reacquisition of a passive landmark (e.g., passive landmarks 300A, 300B). In some embodiments, the discontinuity may be represented by a gradual increase or decrease in the measured distance. In some embodiments, the discontinuity may be determined by a gradual increase in the measured distance beyond a distance change threshold (e.g., 5 cm, 10 cm, 15 cm, 50 cm, 100 cm, etc.), which may be based on the particular work site and the size and shape of the passive landmark. In some embodiments, the discontinuity may be based on the loss of line of sight from the laser range finder to the passive landmark. In such cases, as further discussed with respect to FIGS. 22-23 , in some embodiments, the laser range finder may acquire another passive landmark that is within the line of sight of the laser range finder.

[0061]

[0087] In some embodiments, if the mobility platform changes its position and / or attitude and no discontinuities are detected in the information from the laser range finder, the mobility platform may still reacquire landmarks at the task location before performing the task to confirm the mobility platform's global position and attitude and make any appropriate corrections to the position or attitude before performing the task (e.g., marking the worksite floor). In some such embodiments, reacquisition of passive landmarks to confirm a discontinuity-free position may employ a "sweep" through a reacquisition angular range that is smaller than the angular range for the initial acquisition sweep. For example, the initial acquisition sweep may be approximately 180 degrees, while the reacquisition angular range may be approximately 30 degrees. Such an arrangement may increase the speed of reacquisition compared to the initial acquisition, which may increase the overall speed of task completion by the mobility platform. In some embodiments, the reacquisition angular range may be based on detecting discontinuities in the ranging information from the laser range finder. For example, if a discontinuity is detected, the laser range finder may not move further in the direction of the discontinuity. Such a configuration can ensure that the laser range finder is not pointed in a direction where no passive landmarks are present, avoiding the collection of information not relevant to determining position and / or attitude and further speeding up the localization process. In some embodiments, the reacquisition angle range may be based on an estimated distance to the passive landmark, with a larger estimated distance resulting in a smaller reacquisition angle range. Conversely, a shorter estimated distance may result in a larger reacquisition angle range. In some embodiments, the reacquisition angle range may be approximately 5 degrees, 10 degrees, 15 degrees, 30 degrees, 45 degrees, or another suitable angle. In some embodiments, reacquisition may be performed based on information from a camera associated with the laser range finder.

[0062]

[0088] In some embodiments, the mobility platform 110 may be configured to determine the position of a third passive landmark 300C, which may be located anywhere within the work site. In some such embodiments, the mobility platform may be configured to determine the position of at least one of a first position R1 and a second position R2. While the mobility platform remains stationary, laser range finders associated with the established positions (e.g., the first laser range finder 150A at the first position R1 and the second laser range finder 150B at the second position R2) may acquire the third passive landmark 300C using the method described above. The distance measured from the established point and the third passive landmark may be used to determine the position of the third passive landmark 300C within the x-y plane of the work site. In some embodiments, if the third passive landmark is cylindrical, the radius of the third passive landmark 300C may be added to the measured distance to determine the geometric center point of the third passive landmark. In this manner, additional passive landmarks may be placed within the work site at unknown landmark locations, and the mobility platform may be configured to establish a landmark location (e.g., at a center point of the passive landmark) based on measurements for at least one passive landmark at a known landmark location. In some embodiments, to further ensure the accuracy of the third landmark location, the locations of both the first position R1 and the second position R2 may be determined before determining the third landmark location.

[0063]

[0089] In some embodiments, the distances L1 and L2 measured by the first laser range finder 150A and the second laser range finder 150B may be employed to determine a distance to a geometric center R3 of the mobility platform 110. The distance between the first position R1 and the geometric center R3 may be known based on the configuration of the chassis 112 and the location of the first position R1. Similarly, the distance between the second position R2 and the geometric center R3 may be known based on the configuration of the chassis 112 and the location of the second position R2. In some embodiments, the known distances between the first position R1 and the geometric center R3 and the known distances between the second position R2 and the geometric center R3 may be added to the measured distances L1 and L2, respectively. Such addition may reduce the distances measured by the laser range finders to a single known point on the mobility platform (e.g., the geometric center R3). While the geometric center is employed in some embodiments, the disclosure is not so limited; in other embodiments, any point representing the location of the mobility platform 110 may be employed. For example, such a point may be the center of mass or geometric center of the marking device 140.

[0064]

[0090] In some embodiments, the position and / or orientation of the mobility platform may be performed according to an alternative process to that described with respect to Figure 10. Figure 11 shows a mobility platform 110 positioned within a work site. As shown in Figure 11, the mobility platform includes a chassis 112. The chassis includes a first side 114, a second side 115, a third side 116, and a fourth side 117. The orientation of the sides of the chassis may represent the orientation of the chassis 112. The chassis 112 may be supported by a drive system (see, e.g., Figures 5-6), which is omitted from Figure 11 for clarity. The chassis may also support a marking device 140 configured to mark the floor of the work site.

[0065]

[0091] According to the embodiment of FIG. 11 , the mobility platform includes a first laser range finder 150A and a second laser range finder 150B. The first laser range finder is disposed at a first position R1 on the chassis 112 and configured to measure the distance between the first position R1 and an object within the work site. The second laser range finder is disposed at a second position R2 on the chassis 112 and configured to measure the distance between the second position R2 and an object within the work site. As shown in FIG. 10 , a first passive landmark 300A and a second passive landmark 300B are disposed at the work site. The first laser range finder 150A is pointed at the first passive landmark 300A, and the second laser range finder 150B is pointed at the second passive landmark 300B. Thus, the first laser range finder 150A is configured to measure a distance L1, indicated by the dashed line, between the first passive landmark and the first position R1. Similarly, the second laser rangefinder 150B is configured to measure a distance L2 between a second passive landmark, also shown by a dashed line, and a second position R2.

[0066]

[0092] In some embodiments, as discussed with respect to FIG. 10 , distances L1 and L2 measured by first laser range finder 150A and second laser range finder 150B can be employed to determine a distance to geometric center R3 of mobility platform 110 or another point representing the mobility platform's location. In some embodiments, such as that shown in FIG. 10 , the corrected distances can be employed to determine a circle of possible positions based on the corrected distance measurements. For example, as shown in FIG. 11 , a first circle 310A is centered on first landmark 300A and represents all possible positions of the mobility platform's geometric center R3 based on distance measurements from first laser range finder 150A. Additionally, as shown in FIG. 11 , a second circle 310B is centered on second landmark 300B and represents all possible positions of the mobility platform's geometric center R3 based on distance measurements from second laser range finder 150B.

[0067]

[0093] In some embodiments, initially determining the position of the mobility platform 110 based on the distances measured by the first laser range finder 150A and the second laser range finder 150B may include independently generating possible positions of the mobility platform based on the measured positions. For example, a first set of possible positions may be generated based on the distances measured by the first laser range finder 150A (e.g., a first circle 310A). In addition, a second set of possible positions may be generated based on the distances measured by the second laser range finder 150B (e.g., a second circle 310B). In some embodiments, one or more intersection points between the first set of possible positions and the second set of possible positions. In the embodiment of FIG. 11, because there are two laser range finders, there will be two intersection points between the first set of possible positions and the second set of possible positions. One of the two intersection points will be the actual position of the mobility platform (e.g., the geometric center R3). The other of the two intersection points will be an alternative position R4 that is not the actual position of the mobility platform. Thus, in some embodiments, the location of the mobility platform can be narrowed down to one of two positions within the workspace using only distance information from the laser rangefinder.

[0068]

[0094] In some embodiments, yaw angle information from at least one laser range finder, measured relative to a reference direction, may be used to resolve a true position between two intersection points determined based on distance measurements from the first laser range finder 150A and the second laser range finder 150B. For example, the yaw angle θ1 of the first laser range finder 150A may be employed to distinguish the geometric center R3 of the first of the two intersection points from the second intersection point at the alternate position R4. The yaw angle may be measured relative to a reference direction, which may be a Cartesian direction in some embodiments (such as the positive x-direction in FIG. 11 ). Alternatively, the yaw angle θ2 of the second laser range finder 150B may be used to distinguish the geometric center R3 of the first of the two intersection points from the second intersection point at the alternate position R4. In some embodiments, only the yaw angle of one laser range finder may be employed to resolve an ambiguity between two possible positions of the mobility platform 110. In some embodiments, both the yaw angles from the first laser range finder 150A and the second laser range finder 150B may be employed to determine the position of the mobility platform. Additionally, in some embodiments, the yaw angles of the first laser range finder 150A and the second laser range finder 150B may be employed to determine the attitude of the mobility platform 110 within the work site.

[0069]

[0095] According to example embodiments herein, "information" from a laser range finder may refer to one or more sensor outputs from the laser range finder itself or an associated sensor configured to measure one or more conditions of the laser range finder. For example, information from a laser range finder may include measured distance information. As another example, a yaw angle sensor may measure the yaw angle of the laser range finder within the plane of the work site, and the yaw angle so measured may be included in information from the laser range finder used in determining position and / or attitude or other processes or methods described herein. As yet another example, a pitch angle sensor may measure the pitch angle of the laser range finder about an axis parallel to the plane of the work site, and the pitch angle so measured may be included in information from the laser range finder used in determining position and / or attitude or other processes or methods described herein.

[0070]

[0096] FIG. 12 is a top-view schematic diagram of an exemplary embodiment of a mobility platform 110 in a first position, a work site, and multiple passive landmarks 300A, 300B. The mobility platform 110 includes a chassis 112. The mobility platform 110 also includes a drive system including four wheel assemblies 118A, 118B, 118C, and 118D configured to move and orient the chassis 112 within the work site. The drive system of the mobility platform of FIG. 12 may be holonomic and may operate similarly to the drive systems described with respect to FIGS. 2-4. The wheel assemblies below the chassis 112 are shown with dashed lines to clarify the orientation of the wheel assemblies. The mobility platform also includes a first laser range finder 150A and a second laser range finder 150B mounted on the chassis 112. The first laser range finder 150A and the second laser range finder 150B are configured to measure distances to individual landmarks so that the position and orientation of the mobility platform within the work site (e.g., position and orientation in the x-y plane) can be determined. The mobility platform of Figure 12 is configured to mark the floor of the work site and includes a marking device 140.

[0071]

[0097] As shown in FIG. 12 , the work site includes a first passive landmark 300A and a second passive landmark 300B. The first passive landmark 300A and the second passive landmark 300B can be located at known landmark position points (e.g., control points) within the work site. The passive landmarks can then be used to determine the absolute position and attitude of the mobility platform using distance measurements by the first laser range finder 150A and the second laser range finder 150B. Such a process is further discussed above with respect to FIG. 10 . The mobility platform may also include at least one wheel odometer configured to provide odometry information used to determine the local position and attitude of the mobility platform. The local position can be confirmed against the position determined using the first laser range finder 150A and the second laser range finder 150B. In some embodiments, additional or alternative sensors, including an inertial measurement unit, may be employed, as the disclosure is not so limited.

[0072]

[0098] As shown in FIG. 12 , the plan for the layout is shown in small dashed lines on the work site. In particular, line 400 indicates the portion of the work site that will be marked with marking fluid to form visible lines within the work site. In addition, the plan for marking within the work site according to the embodiment of FIG. 12 includes text 402. The lines 400 and text 402 may be marked by positioning the marking device 140 over the area to be marked and instructing the marking device to deposit marking fluid in the desired locations according to the plan. The drive path of the mobility platform 110 may allow for changes in position and orientation to position the marking device 140 over all of the lines 400 and text 402 to be marked within the work site. In some embodiments, the drive path may be generated according to task efficiency (e.g., the fastest way to mark all of the lines 400 and text 402 within the work site). In some embodiments, the drive path may be generated based at least in part on the progressive completion of task fields (e.g., tasks across a work site), consistent readability of markings (e.g., orienting all text 402 in the same direction), and reduced movement between tasks to eliminate the need to reacquire the first landmark 300A and second landmark 300B at various task locations.

[0073]

[0099] FIG. 13 illustrates the mobility platform 110 of FIG. 12 as it performs the task of marking a line 400 at a work site. As shown in FIG. 13, once the marking device 140 is positioned on the planned line 400, marking 404 can be performed using marking fluid. As shown in FIG. 13, the mobility platform 110 can move along the planned line 400 to ensure that the marking device 140 can perform marking 404. In some embodiments, the mobility platform 110 can move continuously along the length of the planned line 400. In some embodiments, before commencing marking 404, the mobility platform can stop and confirm its position using distance information from the first laser range finder 150A and the second laser range finder 150B. Additionally, in some embodiments, the mobility platform can stop at the end of marking the continuous line 400 and confirm its position. In some embodiments, the mobility platform can move between the start and end points of the planned line 400 to perform marking 404 continuously. In some embodiments, such as those discussed with respect to FIG. 15 , the mobility platform may be capable of marking a continuous curve. In some embodiments, the mobility platform may stop at predetermined intervals of travel distance or time to confirm its position using distance measurements from the first and second laser range finders. While confirming its position using the first and second laser range finders, the laser range finders may perform a sweep as discussed above. As shown in FIG. 13 , as the mobility platform moves, the wheel assemblies 118A, 118B, 118C, 118D may change orientation to allow the mobility platform to change position without changing its attitude. In some embodiments, both the position and attitude of the mobility platform may change as the mobility platform travels its drive path.As shown in Figure 13 in comparison to Figure 12, the yaw angles of the first and second laser range finders 150A and 150B may be changed to track the first and second passive landmarks 300A and 300B. The changes in the yaw angles of the first and second laser range finders may be based on information from one or more other sensors, such as wheel odometers or an inertial measurement unit. In some embodiments, as discussed above, a camera 166 may be used to keep the laser range finders pointed toward their respective passive landmarks.

[0074]

[0100] FIG. 14 is a block diagram of an exemplary embodiment of a method for operating a mobility platform. In some embodiments, the method of FIG. 14 may be executed in whole or in part by at least one processor of the mobility platform. At block 500, a first passive landmark is acquired with a first laser range finder. In some embodiments, acquiring the first passive landmark may include determining from reflected light (e.g., infrared light, visible spectrum light, etc.) that the landmark is present within an area illuminated with light from the first laser range finder. For example, as discussed above, the first laser range finder may be configured to sweep the work site to identify the first passive landmark. At block 502, a second passive landmark is acquired with a second laser range finder. In some embodiments, acquiring the second passive landmark may include determining from reflected light (e.g., infrared light, visible spectrum light, etc.) that the second passive landmark is present within an area illuminated with light from the second laser range finder. For example, as discussed above, the second laser rangefinder may be configured to sweep the work site to identify a second passive landmark. At block 504, the position and attitude of the mobility platform in a plane of the work site are determined based on information from the first laser rangefinder and the second laser rangefinder (e.g., distance information for the first passive landmark and the second passive landmark). At block 506, the mobility platform is moved along a drive path to perform one or more tasks at one or more task locations with the work site. At block 508, based on odometry information from at least one odometry sensor (e.g., wheel odometer, inertial measurement unit, etc.) of the mobility platform, the method includes tracking the first passive landmark with the first laser rangefinder and tracking the second passive landmark with the second laser rangefinder. At optional block 510, the method includes detecting a discontinuity in the distance provided by the first laser rangefinder.For example, the discontinuity may be a gradual increase or decrease in the measured distance that may occur when light emitted by the first laser range finder reflects off the first passive landmark and does not return to the first laser range finder. As one option, in optional block 512, the first passive landmark may be reacquired with the first laser range finder, as discussed above. As an alternative option, in optional block 514, a third passive landmark may be acquired with the first laser range finder. Optional block 514 may be implemented when the discontinuity is caused by loss of line of sight between the first laser range finder and the first passive landmark.

[0075]

[0101] FIG. 15 is a block diagram of an exemplary embodiment for planning the operation of a mobility platform. In some embodiments, the method of FIG. 15 may be executed in whole or in part by a remote server of a construction support system, and output of the method of FIG. 15 may be provided to a mobility platform for execution within a work site. At block 520, the method includes obtaining a task plan including at least one curve to be printed (e.g., a curved line). The curve to be printed may be planned to be printed as part of a construction layout at the work site. At block 522, the method may include determining an arc center for the at least one curve. The arc center may be a point from which all points on the curve are equidistant. At block 524, a radius of the curve may be determined. The radius may be the distance between the arc center and all points on the at least one curve. At block 526, a start angle of the curve may be determined. The start angle may be measured relative to a reference direction in the plane of the work site. For example, the start angle may be determined using a Cartesian axis (e.g., the x-axis or y-axis) established within the work site. At block 528, an end angle of the at least one curve may be determined. The end angle, like the start angle, can be determined relative to a reference direction in the plane of the work site. At block 530, the method includes determining a drive path for the mobility platform including the marking device based on the arc center, the radius, the start angle, and the end angle. The drive path can include orienting one or more wheel assemblies of the mobility platform and a chassis of the mobility platform to enable the mobility platform to move continuously along the length of the at least one curve to continuously mark the at least one curve with the marking device.

[0076]

[0102] FIG. 16 is a top-view schematic diagram of an exemplary embodiment of the mobility platform 110 and obstacle 302 in a first position and attitude. FIGS. 17-19 illustrate changes in the position and attitude of the mobility platform using a holonomic drive system to accomplish tasks at a work site, which may be near the obstacle 302 or the outer edge of the work site. Additionally, FIGS. 17-19 illustrate a method for employing multiple laser range finders on the mobility platform to track passive landmarks when changes in the mobility platform's attitude cause discrepancies between the laser range finders. As shown in FIG. 16 , a layout plan for the work site includes text 402 positioned adjacent to the obstacle 302. The obstacle 302 in FIGS. 17-19 may be a wall. The mobility platform 110 includes a chassis 112 supported by multiple wheel assemblies 118A, 118B, 118C, and 118D, which may form a holonomic drive system, as discussed elsewhere herein. The mobility platform also includes a marking device 140. The chassis of the mobility platform includes a first side 114, a second side 115, a third side 116, and a fourth side 117. In the embodiment of Figures 16-19, the marking device 140 is located on the second side 115. Thus, the marking device is located asymmetrically relative to the center of the chassis 112. As a result, reorienting the chassis 112 so that the second side 115 is positioned toward the obstacle 302 allows the marking device 140 to reach areas of the work site that may otherwise be inaccessible.

[0077]

[0103] 16 , the mobility platform includes a first laser range finder 150A and a second laser range finder 150B. The first laser range finder and the second laser range finder may be employed to determine the position and / or attitude of the mobility platform based on distance measurements to the locations of a first passive landmark 300A and a second passive landmark 300B within the work site. The first passive landmark 300A and the second passive landmark 300B may be located at known landmark position points (e.g., control points) such that measurements relative to the passive landmarks may be employed to determine the absolute position of the mobility platform within the work site.

[0078]

[0104] In the state shown in FIG. 16 , the mobility platform 110 is positioned within a work site. The fourth side 117 of the chassis 112 faces the planned text 402 to be marked by the marking device 140. In the position shown in FIG. 16 , the marking device 140 may not be able to reach the text 402 because the fourth side 117 of the chassis 112 contacts an obstacle 302 before the marking device can be positioned on the text. As shown in FIG. 17 , the drive path of the mobility platform may include a change in the mobility platform's attitude. As indicated by the dashed arrows, the wheel assemblies 118A, 118B, 118C, and 118D may change attitude to allow the chassis to rotate (e.g., counterclockwise). In the state shown in FIG. 17 , the position of the mobility platform 110 may remain unchanged relative to the position shown in FIG. 16 , where the mobility platform's position is represented by a point (e.g., geometric center, center of mass, etc.). However, the mobility platform's attitude has changed so that the first side 114 now faces the text 402. In the orientation of FIG. 17 , the marking device 140 may still be unable to reach the text 402. Therefore, as shown in FIG. 18 , the orientation can continue to change along the drive path to orient the mobility platform to the appropriate orientation so that the marking device can reach and mark the text 402. In FIG. 18 , the orientation has changed again with a further counterclockwise rotation (e.g., 90 degrees). Therefore, the second side 115 now faces the text 402. In the orientation of FIG. 18 , the marking device 140 may be able to reach the text 402. As shown in FIG. 19 , the mobility platform can be moved to the orientation of FIG. 18 with the second side 115 facing the text 402. Once the marking device 140 is aligned with the planned text 402, marking fluid can be deposited to complete the printed text 406 on the shop floor.

[0079]

[0105] 16-18, the first laser range finder 150A and the second laser range finder 150B can track the first passive landmark 300A and the second passive landmark 300B. In the initial position shown in FIG. 16-14, the first laser range finder may be pointing toward the first passive landmark 300A, and the second laser range finder 150B may be pointing toward the second passive landmark 300B. In the position change to the state shown in FIG. 17, a crossover point may exist between the first laser range finder and the second laser range finder. That is, if the first laser range finder 150A continues to track the first passive landmark 300A and the second laser range finder 150B tracks the second passive landmark 300B, the first laser range finder and the second laser range finder may be pointing toward each other, which may interfere with the measurements obtained by each laser range finder. For example, if each laser rangefinder is located on the same elevation plane and the elevation range of interest for each landmark is located on the same elevation plane, one laser rangefinder may physically block the light emitted from the other laser rangefinder. Thus, a crossover point may be a point in the drive path at an attitude of the mobility platform where one laser rangefinder interferes with the distance measurements of the other laser rangefinder.

[0080]

[0106] In some embodiments, during drive path generation, crossover points may be identified so that the laser range finders can reacquire alternative passive landmarks at the crossover points to avoid interference. In some embodiments, the mobility platform itself may identify the crossover points and initiate a reacquisition process for the laser range finders to ensure continued accurate distance measurements. In the example of FIG. 17 , the first laser range finder 150A is instructed to acquire the second passive landmark 300B, and the second laser range finder 150B is instructed to acquire the first passive landmark 300A. The first laser range finder may be able to track the second passive landmark through further changes in the mobility platform's attitude without interference from the second laser range finder until another crossover point is reached. Similarly, the second laser range finder may be able to track the first passive landmark through further changes in the mobility platform's attitude without interference from the first laser range finder until another crossover point is reached. In some embodiments, the first and second laser range finders may be located at different elevation planes on the mobility platform such that physical interference in distance measurements may be reduced or eliminated, thereby correspondingly reducing crossover points and thus eliminating the reacquisition process, which may speed up the overall operation of the mobility platform moving along the drive path.

[0081]

[0107] FIG. 20 is a block diagram of an exemplary embodiment of a method for operating a mobility platform. In some embodiments, the method of FIG. 20 may be executed in whole or in part by a remote server of a construction support system as part of a planning process for a drive path, and the output of the method of FIG. 20 may be provided to a mobility platform for execution within a work site. In some embodiments, the method of FIG. 20 may be executed in whole or in part by a mobility platform within a work site. At block 540, a first passive landmark is acquired by a first laser range finder according to an exemplary method described herein. At block 542, a second passive landmark is acquired by a second laser range finder according to an exemplary method described herein. At block 544, a position and attitude of the mobility platform is determined within a plane based on information from the first laser range finder and the second laser range finder. At block 546, an attitude of the mobility platform is changed. In some embodiments, the position of the mobility platform may be changed instead of or in addition to changing the attitude. At block 548, based on the change in orientation, the method includes determining one or more crossover points between the first laser range finder and the second laser range finder within the change in attitude. At block 550, the method may include acquiring a first passive landmark with the second laser range finder at one of the one or more crossover points. At block 552, the method may include acquiring a second passive landmark with the first laser range finder at one of the one or more crossover points.

[0082]

[0108] FIG. 21 is a schematic diagram illustrating an exemplary embodiment of a driving path 410 and line of sight to two passive landmarks 300A, 300B at a work site 301. While the embodiment of FIG. 21 depicts the work site as a bounded rectangle, the disclosure is not so limited; in some embodiments, the work site may be unbounded or lack a physical boundary. As shown in FIG. 21 , a first passive landmark 300A and a second passive landmark 300B are positioned within the work site 301 at known points and may serve as references for determining position and orientation using laser range finder distance measurements, as described herein. The driving path 410 represents a possible path a mobility platform may take within the work site 301. The work site in FIG. 21 includes multiple obstacles, which in the embodiment of FIG. 21 are pillars 304. The line of sight between various areas of the work site 301 and the passive landmarks 300A, 300B is marked in text. A dashed line indicates the boundary of the line of sight to the first passive landmark 300A. The dashed-dotted lines indicate the boundaries of the line of sight to the second passive landmark 300B. The area marked "A" has line of sight only to the first passive landmark 300A. The area marked "B" has line of sight only to the second passive landmark 300B. The area marked "AB" has line of sight to both the first passive landmark 300A and the second passive landmark 300B. The area marked "N" has no line of sight to either the first passive landmark 300A or the second passive landmark 300B. The lack of line of sight means that the mobility platform may not be able to measure the distance to a passive landmark that is blocked by an obstacle in the work site. Thus, in areas without line of sight to a particular passive landmark, that passive landmark may not be used in determining position and / or attitude.

[0083]

[0109] According to some embodiments, line of sight to at least two landmarks may be used to determine the position and attitude of the mobility platform. According to such embodiments, a landmark position placement process may occur during the planning process of drive path 410. During the landmark placement process, the positions of passive landmarks within the work site may be determined (e.g., by a remote server based on drive path 410). A user may then place passive landmarks at appropriate locations within the work site to enable the mobility platform to determine its position and attitude as the drive path is navigated and one or more associated tasks are performed. In some embodiments, the landmark placement process may include ensuring that, for every position along drive path 410, at least two landmarks are within line of sight to the mobility platform. Thus, if there are fewer than two passive landmarks, additional passive landmarks may be added to the work site to supplement the positions of the passive landmarks already present.

[0084]

[0110] In the drive path 410 of FIG. 21 , the mobility platform may have line of sight to at least one of the first passive landmark 300A and the second passive landmark 300B at each location along the drive path. However, there are certain portions of the drive path where the mobility platform only has line of sight to one of the first passive landmark 300A and the second passive landmark 300B. Thus, as shown in FIG. 22 , a third passive landmark 300C can be added to the work site 301 to complement the first passive landmark 300A and the second passive landmark 300B. As shown in FIG. 22 , with the addition of the third passive landmark, each region has been updated to reflect line of sight to three passive landmarks. For each portion of the drive path 410 that previously had line of sight to fewer than two passive landmarks, the drive path now has line of sight to at least two passive landmarks. For example, region 303 and the portion of the drive path 410 therein only had line of sight to the first passive landmark 300A in FIG. 21 . 22, however, region 303 and the portion of drive path 410 therein has line of sight to both the first passive landmark 300A and the newly placed third passive landmark 300C. Depending on the particular drive path, additional passive landmarks may be added to ensure line of sight coverage for each portion of the drive path. In some embodiments, additional passive landmarks may be added to ensure that there is line of sight to at least two passive landmarks for each region of worksite 301, regardless of drive path 410.

[0085]

[0111] FIG. 23 is a block diagram of an exemplary embodiment for planning the operation of a mobility platform. In some embodiments, the method of FIG. 23 may be executed in whole or in part by a remote server of a construction support system as part of a planning process for a drive path, and output of the method of FIG. 23 may be provided to a user for locating the mobility platform for execution within the work site and landmarks within the work site. In some embodiments, "determining" may be a calculation performed by a processor based on one or more data inputs and one or more sets of computer-readable instructions. At block 560, the method includes determining a drive path for the mobility platform through the work site. The drive path may be based on the completion of one or more tasks at one or more task locations within the work site. At block 562, the method includes determining, for each position of the mobility platform on the drive path, a line of sight between the mobility platform and a first landmark. For example, the method may include generating a schematic diagram similar to FIG. 21. At block 564, the method includes determining, for each position of the mobility platform on the drive path, a line of sight between the mobility platform and a second landmark. For example, the method may include generating a schematic diagram similar to FIG. 21. At block 566, the method includes determining whether there is a portion of the driving path without line of sight to at least two of the first landmark, the second landmark, and any additional landmarks. If the determination at block 574 is no, the method may end, and at block 576, the driving path and the landmark locations of the first landmark and the second landmark may be provided to the mobility platform and / or the user. For example, the driving path and the landmark locations may be communicated to the mobility platform via a communications network (e.g., a wireless network). As another example, the driving path and / or the landmark locations may be made known to the user so that the user can view the driving path and / or the landmark locations. In some embodiments, the driving path and / or the landmark locations may be displayed on a graphical user interface.In some embodiments, a user may accept, modify, or initiate regeneration of the drive path and / or landmark positions on the graphical user interface through user input. If the determination at block 568 is yes, at block 570, additional landmarks may be added to the work site. At block 572, the method may include determining a line of sight between the mobility platform and the additional landmark for portions of the drive path lacking a line of sight from block 566. Depending on the line of sight determined at block 572, the positions of the additional landmarks may be adjusted so that all portions of the drive path have a line of sight to the additional landmark. The method may then return to block 566. Block 566 may serve as a confirmation that the entire drive path has a line of sight to at least two passive landmarks within the work site. Blocks 566, 568, 570, and 572 may be repeated as necessary until the entire drive path has adequate line of sight coverage by passive landmarks.

[0086]

[0112] FIG. 24 is a schematic side view of an exemplary embodiment of a mobility platform 110 having passive landmarks 300 and a first chassis pitch, and FIG. 25 is a schematic side view of a mobility platform having a second chassis pitch. As shown in FIG. 24 , the mobility platform is similar to that of FIGS. 5-6 and includes a chassis 112, a wheel assembly 118 including wheels 120, a laser range finder 150, and a marking device 140 attached to the chassis 112 by a carriage 142. The laser range finder 150 of FIGS. 24-25 operates similarly to that of FIGS. 7-9 and is adjustable in a yaw direction (e.g., about the z-axis) and a pitch direction (e.g., about the y-axis or another axis disposed in the x-y plane). In some embodiments, such as those shown in FIGS. 24-25 , the laser range finder 150 may include a camera 166, which may assist in feedback control of the laser range finder 150 and / or acquisition of passive landmarks 300, as described above.

[0087]

[0113] According to the embodiment of FIGS. 24-25 , the passive landmark 300 includes a landmark target area 305. The landmark target area 305 may be configured to be a position at an altitude where light emitted from the laser range finder 150 reflects when the chassis 112 is horizontal (e.g., flat) and the laser range finder 150 is also horizontal. For example, as shown in FIG. 24 , the difference in the pitch of the laser range finder relative to the pitch ρ1 of the chassis 112 in the state of FIG. 24 is zero relative to the horizontal plane, and light emitted from the laser range finder, shown by the dashed line, is configured to reflect from the landmark target area 305 on the passive landmark 300. As shown in FIGS. 24-25 , the landmark target area 305 may have some tolerance. In some embodiments, the landmark target area may have a different reflectivity, color, or other characteristic compared to other portions of the passive landmark that may be detectable by the first laser range finder and / or camera 166. In other embodiments, the target selection area may be virtual, and the passive landmark 300 may have the same characteristic at all altitudes. As shown in FIG. 24, the mobility platform is placed on a flat work site floor 306 parallel to the horizontal plane (eg, perpendicular to the direction of local gravity).

[0088]

[0114] As shown in FIG. 25 , in some cases, the worksite floor 306 may not be perfectly flat, and elevations may vary in different parts of the worksite. For example, as shown in FIG. 25 , the mobility platform 110 is positioned on a slope of the worksite floor. The slope shown in FIG. 25 may be exaggerated for simplicity. Slight changes in the elevation of the worksite floor may be significant in construction operations, and the inventors have recognized the benefits of measuring the topography of the worksite floor. In some embodiments, the laser range finder 150 may be maintained at a target elevation range as the mobility platform 110 moves along the worksite floor. In some cases, the target elevation range may be aligned with the landmark target range 305. In some such embodiments, the pitch of the laser range finder may no longer be horizontal. Changes in the pitch of the laser range finder may be employed to determine changes in the elevation of the mobility platform. Additionally, changes in the pitch of the laser range finder may be employed to determine a corresponding change in chassis pitch. Based on the chassis pitch, the elevation of the contact point between each of the wheels 120 can be determined based on the known distances between the wheels, the chassis, and the laser range finder. In some embodiments, the target altitude range may maintain alignment of the laser range finder with a horizontal plane. For example, as shown in FIG. 25 , the laser range finder 150 may be maintained horizontally so that light emitted from the laser range finder reflects off a lower portion of the passive landmark 300 compared to the state of FIG. 24 . In some cases, maintaining the laser range finder in a horizontal plane may cause light reflected from the passive landmark 300 to deviate from the landmark target range 305. The difference between the horizontal laser range finder pitch and the chassis pitch ρ2 may be used to determine the chassis pitch. The chassis pitch may then be used to determine the altitude of the contact point between the wheel 120 and the floor 306. This process may be completed throughout the mobility platform's drive path so that altitude data for each wheel 120 may be collected.This data can then be employed to generate a three-dimensional topographical map of the work site floor 306, which may be useful for adjusting construction plans, taking remedial measures to level the work site floor, or for providing information to users of the mobility platform.

[0089]

[0115] In some embodiments, the process of determining the elevation of the work site, as described above with respect to FIGS. 24-25, may extend to a second laser range finder. That is, in some embodiments, the determination of the elevation may be performed based on pitch information from the second laser range finder. In some embodiments, using the second laser range finder may enable the roll angle of the chassis to be determined. For example, a first laser range finder may fix a first point in three-dimensional space, and a second laser range finder may fix a second point in three-dimensional space. A unique three-dimensional vector between the first point and the second point, when combined with pitch information from the first and second laser range finders, may enable the attitude of the chassis 112 about the pitch and roll axes to be determined. In this manner, the elevation of each of the mobility platform's four wheels may be determined based on information from the first and second laser range finders.

[0090]

[0116] FIG. 26 is a block diagram of an exemplary embodiment of a method for operating a mobility platform. In some embodiments, the method of FIG. 26 may be performed in whole or in part by a mobility platform within a work site. At block 580, the method includes acquiring passive landmarks with a laser range finder (e.g., using a camera or a sweeping process). At block 582, the method includes moving the mobility platform along the drive path. At block 584, the method includes altering the range finder pitch of the laser range finder to maintain the laser range finder at a horizontal pitch (e.g., a target altitude range). At block 586, the method includes determining a chassis pitch of the mobility platform for each position of the mobility platform along the drive path based on the alteration of the range finder pitch of the laser range finder. At optional block 588, the method includes generating a topographical map of the drive path based on the alteration of the chassis pitch of the mobility platform. In some embodiments, data from blocks 584 and 586 may be transmitted to a remote server, which may process the data and perform the steps of block 588.

[0091]

[0117] FIG. 27 is a block diagram of an exemplary embodiment for operating the construction assistance system. The embodiment of FIG. 27 illustrates a process flow of the construction assistance system according to some embodiments. In block 600, CAD data or another file may be provided to the remote server 200 of the construction assistance system. As described above, in block 602, the remote server may process the CAD data as part of a path planning process. As part of the path planning process, the remote server may generate a 2D map of the work site in block 604, generate landmark locations for placing landmarks within the work site in block 606, generate driving information for moving the mobility platform along the driving path in block 608, and generate task information 610 for completion of one or more tasks at one or more task locations within the work site. Input during the path planning process of block 602 may be received from a user at the user workstation 210 (e.g., via the graphical user interface 212). For example, the user may specify certain tasks and task locations for the task information 610. The completed driving path may be provided by the remote server 200 to the workstation 210 for verification and adjustment by the user. In block 612, the user can verify the accuracy of the path plan, make appropriate corrections, or add additional input, and re-complete the path planning process. The user can also validate the driving path, which can then be transmitted to the mobility platform 110 for execution. In block 614, the mobility platform can execute the driving path and complete the task. Prior to executing the driving path, the user can place passive landmarks within the work site according to the landmark information in block 606.

[0092]

[0118] The above-described embodiments of the technology described herein can be implemented in any of numerous ways. For example, these embodiments can be implemented using hardware, software, or a combination thereof. When implemented in software, the software code can be executed on any suitable processor or collection of processors, whether provided within a single computer or distributed among multiple computers. Such a processor can be implemented as an integrated circuit with one or more processors within an integrated circuit component, including commercially available integrated circuit components known in the art by names such as CPU chips, GPU chips, microprocessors, microcontrollers, or coprocessors. Alternatively, the processor can be implemented by custom circuitry, such as an ASIC, or semi-custom circuitry resulting from constructing a programmable logic device. As yet another alternative, the processor can be part of a larger circuit or semiconductor device, whether commercially available, semi-custom, or custom. As a specific example, some commercially available microprocessors have multiple cores, such that one or a subset of the cores can constitute a processor. However, a processor can be implemented using any suitable form of circuitry.

[0093]

[0119] It should further be understood that a computer may be embodied in any of a number of forms, such as a rack-mounted computer, a desktop computer, a laptop computer, or a tablet computer, etc. In addition, a computer may be embedded in devices not generally considered computers but having suitable processing capabilities, including personal digital assistants (PDAs), smartphones, or any other suitable portable or fixed electronic device.

[0094]

[0120] Additionally, a computer may have one or more input and output devices. These devices may be used, among other things, to present a user interface. Examples of output devices that may be used to provide a user interface include a printer or display screen for visually presenting output, and a speaker or other audio device for audibly presenting output. Examples of input devices that may be used in a user interface include keyboards and pointing devices such as mice, touchpads, and digitizing tablets. As another example, a computer may receive input information through speech recognition or other audible formats.

[0095]

[0121] Such computers may be interconnected by one or more networks of any suitable type, including local or wide area networks such as an enterprise network or the Internet. Such networks may be based on any suitable technology and may operate according to any suitable protocol, and may include wireless networks, wired networks, or fiber optic networks.

[0096]

[0122] Furthermore, the various methods or processes outlined herein may be coded as software executable on one or more processors employing any one of a variety of operating systems or platforms. In addition, such software may be written using any of a number of suitable programming languages ​​and / or programming or scripting tools, and may be compiled as executable machine code or intermediate code that runs on a framework or virtual machine.

[0097]

[0123] In this regard, the embodiments described herein may be embodied as a computer-readable storage medium (or multiple computer-readable media) (e.g., computer memory, one or more floppy disks, compact disks (CDs), optical disks, digital video disks (DVDs), magnetic tapes, flash memory, circuitry in rewritable gate arrays or other semiconductor devices, or other tangible computer storage media) encoded with one or more programs that, when executed on one or more computers or other processors, perform methods that implement the various embodiments described above. As is evident from the above examples, a computer-readable storage medium may retain information for a period of time sufficient to provide computer-executable instructions in a non-transitory form. Such a computer-readable storage medium may be transportable such that the programs stored thereon can be loaded onto one or more different computers or other processors to implement various aspects of the present disclosure discussed above. As used herein, the term "computer-readable storage medium" encompasses only non-transitory computer-readable media that can be considered an article of manufacture (i.e., product) or machine. Alternatively or additionally, the present disclosure may be embodied as a computer-readable medium other than a computer-readable storage medium, such as a propagated signal.

[0098]

[0124] The terms "program" or "software" are used herein in a generic sense to refer to any type of computer code or set of computer-executable instructions that can be employed to program a computer or other processor to implement various aspects of the present disclosure as discussed above. Additionally, in accordance with one aspect of the present embodiments, it should be understood that one or more computer programs that, when executed, perform the methods of the present disclosure need not reside on a single computer or processor, but may be modularly distributed among a number of different computers or processors to implement various aspects of the present disclosure.

[0099]

[0125] Computer-executable instructions may be in many forms, such as program modules, executed by one or more computers or other devices. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types. Typically, the functionality of the program modules may be combined or distributed as desired in various embodiments.

[0100]

[0126] Furthermore, data structures may be stored in a computer-readable medium in any suitable format. For simplicity of illustration, data structures may be depicted as having fields that are related by location within the data structure. Such relationships may similarly be achieved by assigning storage for the fields to locations within the computer-readable medium, with the locations conveying the relationship between the fields. However, any suitable mechanism may be used to establish relationships between information within fields of a data structure, including the use of pointers, tags, or other mechanisms for establishing relationships between data elements. [Example]

[0101]

[0127] example

[0102]

[0128] In one example, a mobility platform is provided, configured to perform one or more tasks at a worksite having a first passive landmark located at a first known landmark location and a second passive landmark located at a second known landmark location. The mobility platform includes a chassis, a drive system supporting the chassis, the drive system including at least two wheels and configured to move the mobility platform within a work site, a first laser rangefinder disposed on the chassis at a first location, and a second laser rangefinder disposed on the chassis at a second location different from the first location, and at least one processor configured to acquire a first passive landmark with the first laser rangefinder and acquire a second passive landmark with the second laser rangefinder, determine a first position of the chassis based on a first distance measured by the first laser rangefinder between the first location and a first known landmark position and a second distance measured by the second laser rangefinder between the second location and a second known landmark position, and determine a first attitude of the mobility platform based on first yaw angle information from at least one of the first laser rangefinder and the second laser rangefinder.

[0103]

[0129] Optionally, the mobility platform may include one or more of the following attributes: a. The drive system is a holonomic drive system. b. The drive system includes four wheel assemblies, each of the four wheel assemblies including a wheel configured to rotate about a wheel axis, a first actuator configured to rotate the wheel about the wheel axis, and a second actuator configured to rotate the wheel about a pivot axis perpendicular to the wheel axis. c. The mobility platform further includes four wheel odometers, each of the four wheel odometers configured to measure a distance traveled by one of the four wheel assemblies, and the at least one processor is further configured to estimate a change in position of the chassis from the first position based on odometry information from the four wheel odometers. d. The mobility platform further includes a marking device disposed on the chassis and configured to deposit marking material on the work site floor. e. Acquiring a first passive landmark with a first laser rangefinder includes sweeping the work site with the first laser rangefinder to collect first sweep information, detecting a first known landmark position of the first passive landmark based on the first sweep information, and orienting the first laser rangefinder relative to the first passive landmark based on the first known landmark position. f. Detecting a first known landmark position of the first passive landmark includes detecting a shape of the first passive landmark. g. Detecting a first known landmark position of the first passive landmark includes detecting a color of the first passive landmark. h. the mobility platform further includes at least one camera, and acquiring the first passive landmark includes identifying a first known landmark position of the first passive landmark with the at least one camera, and directing the first laser rangefinder toward the first passive landmark based on the first known landmark position. i. the at least one processor is further configured to track a first passive landmark with a first laser rangefinder and track a second passive landmark with a second laser rangefinder based on information from the at least one camera. j. The at least one processor is further configured to command the drive system to move the mobility platform along the drive path to perform one or more tasks at one or more task locations within the work site. k. One or more tasks include marking the floor of the work site with a marking material. l. The at least one processor is further configured to track a first passive landmark with a first laser range finder and track a second passive landmark with a second laser range finder based on odometry information from the at least one odometry sensor. m. The at least one processor is further configured to command the drive system to stop the mobility platform at one or more task locations within the work site, and upon commanding the drive system to stop, reacquire a first passive landmark with a first laser range finder, reacquire a second passive landmark with a second laser range finder, determine a second position of the chassis based on a first distance between the first position measured by the first laser range finder and the first known landmark location, and a second distance between the second position measured by the second laser range finder and the second known landmark location, and determine a second attitude of the mobility platform based on second yaw angle information from at least one of the first laser range finder and the second laser range finder. n. The at least one processor is further configured to detect a discontinuity in the first distance measured by the first laser range finder and, upon detecting the discontinuity in the first distance measured by the first laser range finder, reacquire the first passive landmark with the first laser range finder. o. The at least one processor is further configured to detect a discontinuity in the first distance measured by the first laser range finder, and, upon detecting the discontinuity in the first distance measured by the first laser range finder, acquire a third passive landmark positioned within the work site at a third known landmark location with the first laser range finder. p. The discontinuity in the first distance measured by the first laser rangefinder is a change in the measured first distance that exceeds a distance change threshold. q. The at least one processor is further configured to command the drive system to move the mobility platform to a third pose based on the drive path and the one or more task positions. r. The at least one processor is further configured to determine a crossover point between the first laser range finder and the second laser range finder within the movement of the mobility platform to the third attitude, acquire a first passive landmark at the crossover point with the second laser range finder, and acquire a second passive landmark at the crossover point with the first laser range finder. s. The at least one processor is further configured to acquire a third passive landmark placed at a third unknown landmark location with a first laser range finder, and determine the third unknown landmark location based on the first position of the chassis, a third distance measured by the first laser range finder between the first position and the third unknown landmark location, and yaw angle information from the first laser range finder.

[0104]

[0130] In another example, a mobility platform may operate within a work site according to a method. The mobility platform includes a chassis, a first laser range finder disposed at a first position on the chassis, a second laser range finder disposed at a second position on the chassis, and a drive system. The method includes acquiring a first passive landmark disposed at a first known landmark position with the first laser range finder, acquiring a second passive landmark disposed at a second known landmark position with the second laser range finder, determining a first position of the chassis based on a first distance between the first position and the first known landmark position measured by the first laser range finder and a second distance between the second position and the second known landmark position measured by the second laser range finder, and determining a first attitude of the mobility platform based on first yaw angle information from at least one of the first laser range finder and the second laser range finder.

[0105]

[0131] Optionally, the method may include one or more of the following features: a. Acquiring a first passive landmark includes sweeping the work site with a first laser range finder to collect first sweep information, detecting a first known landmark position of the first passive landmark based on the first sweep information, and orienting the first laser range finder to the first passive landmark based on the first known landmark position. b. Detecting a first known landmark position of the first passive landmark includes detecting a shape of the first passive landmark. c. Detecting a first known landmark position of a first passive landmark includes detecting a color of the first passive landmark. d. The method further includes acquiring the first passive landmark, wherein the method includes identifying a first known landmark position of the first passive landmark with at least one camera of the mobility platform, and directing a first laser rangefinder toward the first passive landmark based on the first known landmark position. e. The method further includes tracking a first passive landmark with a first laser rangefinder based on information from the at least one camera, and tracking a second passive landmark with a second laser rangefinder. f. The method further includes moving the mobility platform along the drive path to perform one or more tasks at one or more task locations within the work site. g. One or more tasks include marking the work site floor with marking material. h. The method further includes tracking a first passive landmark with a first laser range finder based on odometry information from at least one odometry sensor of the mobility platform, and tracking a second passive landmark with a second laser range finder. i. the method further includes stopping the mobility platform at one or more task locations within the work site, and, upon stopping the mobility platform, reacquiring a first passive landmark with a first laser range finder, reacquiring a second passive landmark with a second laser range finder, determining a second position of the chassis based on a first distance between the first position measured by the first laser range finder and the first known landmark position, and a second distance between the second position measured by the second laser range finder and the second known landmark position, and determining a second attitude of the mobility platform based on second yaw angle information from at least one of the first laser range finder and the second laser range finder. j. The method further includes detecting a discontinuity in the first distance measured by the first laser range finder, and upon detecting the discontinuity in the first distance measured by the first laser range finder, reacquiring the first passive landmark with the first laser range finder. k. The method further includes detecting a discontinuity in the first distance measured by the first laser range finder, and upon detecting the discontinuity in the first distance measured by the first laser range finder, acquiring with the first laser range finder a third passive landmark located within the work site at a third known landmark location. l. The first distance discontinuity measured by the first laser rangefinder is a change in the measured first distance that exceeds a distance change threshold. m. The method further includes moving the mobility platform to a third pose based on the drive path and the one or more task positions. n. The method further includes determining a crossover point between the first laser range finder and the second laser range finder within movement of the mobility platform to the third attitude, acquiring a first passive landmark at the crossover point with the second laser range finder, and acquiring a second passive landmark at the crossover point with the second laser range finder. o. the method further includes acquiring a third passive landmark positioned at a third unknown landmark location with a first laser range finder, and determining the third unknown landmark location based on the first position of the chassis, a third distance measured by the first laser range finder between the first position and the third unknown landmark location, and yaw angle information from the first laser range finder.

[0106]

[0132] In another example, a non-transitory computer-readable storage medium is provided having instructions stored thereon that, when executed by at least one processor, cause the at least one processor to perform a method for operating a mobility platform at a work site. The mobility platform includes a chassis, a first laser range finder disposed at a first position on the chassis, a second laser range finder disposed at a second position on the chassis, and a drive system. The method includes acquiring a first passive landmark disposed at a first known landmark position with the first laser range finder, acquiring a second passive landmark disposed at a second known landmark position with the second laser range finder, determining a first position of the chassis based on a first distance measured by the first laser range finder between the first position and the first known landmark position and a second distance measured by the second laser range finder between the second position and the second known landmark position, and determining a first attitude of the mobility platform based on first yaw angle information from at least one of the first laser range finder and the second laser range finder.

[0107]

[0133] Optionally, the method may include one or more of the following features: a. Acquiring a first passive landmark includes sweeping the work site with a first laser range finder to collect first sweep information, detecting a first known landmark position of the first passive landmark based on the first sweep information, and orienting the first laser range finder to the first passive landmark based on the first known landmark position. b. Detecting a first known landmark position of the first passive landmark includes detecting a shape of the first passive landmark. c. Detecting a first known landmark position of a first passive landmark includes detecting a color of the first passive landmark. d. The method further includes acquiring the first passive landmark, wherein the method includes identifying a first known landmark position of the first passive landmark with at least one camera of the mobility platform, and directing a first laser rangefinder toward the first passive landmark based on the first known landmark position. e. The method further includes tracking a first passive landmark with a first laser rangefinder based on information from the at least one camera, and tracking a second passive landmark with a second laser rangefinder. f. The method further includes moving the mobility platform along the drive path to perform one or more tasks at one or more task locations within the work site. g. One or more tasks include marking the work site floor with marking material. h. The method further includes tracking a first passive landmark with a first laser range finder based on odometry information from at least one odometry sensor of the mobility platform, and tracking a second passive landmark with a second laser range finder. i. the method further includes stopping the mobility platform at one or more task locations within the work site, and, upon stopping the mobility platform, reacquiring a first passive landmark with a first laser range finder, reacquiring a second passive landmark with a second laser range finder, determining a second position of the chassis based on a first distance between the first position measured by the first laser range finder and the first known landmark position, and a second distance between the second position measured by the second laser range finder and the second known landmark position, and determining a second attitude of the mobility platform based on second yaw angle information from at least one of the first laser range finder and the second laser range finder. j. The method further includes detecting a discontinuity in the first distance measured by the first laser range finder, and upon detecting the discontinuity in the first distance measured by the first laser range finder, reacquiring the first passive landmark with the first laser range finder. k. The method further includes detecting a discontinuity in the first distance measured by the first laser range finder, and upon detecting the discontinuity in the first distance measured by the first laser range finder, acquiring with the first laser range finder a third passive landmark located within the work site at a third known landmark location. l. The first distance discontinuity measured by the first laser rangefinder is a change in the measured first distance that exceeds a distance change threshold. m. The method further includes moving the mobility platform to a third pose based on the drive path and the one or more task positions. n. The method further includes determining a crossover point between the first laser range finder and the second laser range finder within movement of the mobility platform to the third attitude, acquiring a first passive landmark at the crossover point with the second laser range finder, and acquiring a second passive landmark at the crossover point with the second laser range finder. o. the method further includes acquiring a third passive landmark positioned at a third unknown landmark location with a first laser range finder, and determining the third unknown landmark location based on the first position of the chassis, a third distance measured by the first laser range finder between the first position and the third unknown landmark location, and yaw angle information from the first laser range finder.

[0108]

[0134] In yet a further example, a method for placing landmarks within a work site is provided, the method including obtaining obstacle information within the work site, calculating, with at least one processor, a drive path for a mobility platform through the work site based on one or more tasks performed within the work site at one or more task locations, calculating a first landmark position for a first passive landmark within the work site, calculating a second landmark position for a second passive landmark within the work site, calculating, for each location on the drive path, a line of sight between the mobility platform and the first passive landmark at the first landmark location and a line of sight between the mobility platform and the second passive landmark at the second landmark location, calculating whether there is a portion of the drive path with line of sight to below both the first passive landmark and the second passive landmark, and if determining that there is a portion of the drive path with line of sight to below both the first passive landmark and the second passive landmark, calculating a third landmark position for a third passive landmark at the work site, and informing a user of the first landmark position, the second landmark position, and the third landmark position.

[0109]

[0135] Optionally, the method may include one or more of the following features: a. Calculating a line of sight between the mobility platform and a first passive landmark at a first landmark location and a second passive landmark at a second landmark location is based on the obstacle information. b. The third landmark location has a line of sight to a portion of the drive path that has a line of sight to less than both the first passive landmark or the second passive landmark. c. The method further includes calculating, with at least one processor, that the entire drive path has line of sight to at least two of the first passive landmark, the second passive landmark, and the third passive landmark, and communicating the drive path, the first landmark position, the second landmark position, and the third landmark position to the mobility platform. d. The method further includes calculating, with the at least one processor, a redirection of the mobility platform within the drive path based on the one or more of the task position and obstacle information. e. The method further includes using at least one processor to calculate, within a redirection of the mobility platform, a crossover point between the first laser range finder and the second laser range finder of the mobility platform, and adjusting at least one of the first landmark position, the second landmark position, and the third landmark position to eliminate the crossover point between the first laser range finder and the second laser range finder. f. The method further includes using at least one processor to calculate, for each position of the mobility platform on the drive path, a line of sight between the mobility platform and a first passive landmark at the first landmark location, a line of sight between the mobility platform and a second passive landmark at the second landmark location, and a line of sight between the mobility platform and a third passive landmark at the third landmark location, calculating whether there is a second portion of the drive path that has line of sight to fewer than at least two of the first passive landmark, the second passive landmark, and the third passive landmark, and if it is determined that there is a second portion of the drive path that has line of sight to fewer than at least two of the first passive landmark, the second passive landmark, and the third passive landmark, calculating a fourth landmark position for a fourth passive landmark at the work site. g. the method further includes placing a first passive landmark at a first landmark location within the work site, placing a second passive landmark at a second landmark location within the work site, and placing a third passive landmark at a third landmark location within the work site. h. Informing the user of the first landmark location, the second landmark location, and the third landmark location includes displaying the first landmark location, the second landmark location, and the third landmark location in a graphical user interface.

[0110]

[0136] In yet another example, a non-transitory computer-readable storage medium having stored thereon instructions that, when executed by at least one processor, cause the at least one processor to perform a method for placing landmarks within a worksite. The method includes calculating a drive path for a mobility platform through the work site based on one or more tasks performed within the work site at one or more task locations; calculating a first landmark position for a first passive landmark within the work site; calculating a second landmark position for a second passive landmark within the work site; for each location on the drive path, calculating a line of sight between the mobility platform and the first passive landmark at the first landmark location and a line of sight between the mobility platform and the second passive landmark at the second landmark location; calculating whether there is a portion of the drive path where there is line of sight to below both the first passive landmark and the second passive landmark; and if it is determined that there is a portion of the drive path where there is line of sight to below both the first passive landmark and the second passive landmark, calculating a third landmark position for a third passive landmark at the work site; and informing a user of the first landmark position, the second landmark position, and the third landmark position.

[0111]

[0137] Optionally, the method may include one or more of the following features: a. Calculating a line of sight between the mobility platform and a first passive landmark at a first landmark location and a second passive landmark at a second landmark location is based on the obstacle information. b. The third landmark location has a line of sight to a portion of the drive path that has a line of sight to less than both the first passive landmark or the second passive landmark. c. The method further includes calculating, with at least one processor, that the entire drive path has line of sight to at least two of the first passive landmark, the second passive landmark, and the third passive landmark, and communicating the drive path, the first landmark position, the second landmark position, and the third landmark position to the mobility platform. d. The method further includes calculating, with the at least one processor, a redirection of the mobility platform within the drive path based on the one or more of the task position and obstacle information. e. The method further includes using at least one processor to calculate, within a redirection of the mobility platform, a crossover point between the first laser range finder and the second laser range finder of the mobility platform, and adjusting at least one of the first landmark position, the second landmark position, and the third landmark position to eliminate the crossover point between the first laser range finder and the second laser range finder. f. The method further includes using at least one processor to calculate, for each position of the mobility platform on the drive path, a line of sight between the mobility platform and a first passive landmark at the first landmark location, a line of sight between the mobility platform and a second passive landmark at the second landmark location, and a line of sight between the mobility platform and a third passive landmark at the third landmark location, calculating whether there is a second portion of the drive path that has line of sight to fewer than at least two of the first passive landmark, the second passive landmark, and the third passive landmark, and if it is determined that there is a second portion of the drive path that has line of sight to fewer than at least two of the first passive landmark, the second passive landmark, and the third passive landmark, calculating a fourth landmark position for a fourth passive landmark at the work site. g. the method further includes placing a first passive landmark at a first landmark location within the work site, placing a second passive landmark at a second landmark location within the work site, and placing a third passive landmark at a third landmark location within the work site. h. Informing the user of the first landmark location, the second landmark location, and the third landmark location includes displaying the first landmark location, the second landmark location, and the third landmark location in a graphical user interface.

[0112]

[0138] In yet another example, a method for operating a mobility platform at a work site is provided. The mobility platform includes a chassis, a first laser range finder disposed on the chassis, and a drive system including at least one wheel. The method includes acquiring a first passive landmark with the first laser range finder, moving the mobility platform along a drive path with the drive system, altering a first range finder pitch of the first laser range finder to maintain the first laser range finder within a first target altitude range above the first passive landmark as the mobility platform moves along the drive path, determining a chassis pitch of the mobility platform for each position of the mobility platform along the drive path based on the alteration of the first range finder pitch of the first laser range finder, and determining an altitude of the work site for the at least one wheel for each position of the mobility platform along the drive path based on the chassis pitch.

[0113]

[0139] Optionally, the method may include one or more of the following features: a. Changing the first rangefinder pitch includes commanding an actuator to move the first laser rangefinder. b. The drive system is a holonomic drive system. c. The at least one wheel is a four wheel, and the drive system includes four wheel assemblies, each of the four wheel assemblies including a wheel of the four wheels configured to rotate about a wheel axis, a first actuator configured to rotate the wheel about the wheel axis, and a second actuator configured to rotate the wheel about a pivot axis perpendicular to the wheel axis. d. The mobility platform further includes a second laser rangefinder disposed on the chassis, and the method further includes acquiring a second passive landmark with the second laser rangefinder, altering a second rangefinder pitch of the second laser rangefinder to maintain the second laser rangefinder within a second target altitude range on the second passive landmark as the mobility platform moves along the drive path, determining a second chassis pitch of the mobility platform for each position of the mobility platform along the drive path based on the alteration of the second rangefinder pitch of the second laser rangefinder, and determining an altitude of the work site at at least one wheel based on the chassis pitch and the second chassis pitch for each position of the mobility platform along the drive path. e. The method further includes generating, for each position of the mobility platform along the drive path, a topographical map of the drive path based on the elevation of the work site. f. Acquiring the first passive landmark includes sweeping the work site with a first laser range finder to collect first sweep information, detecting a first landmark position of the first passive landmark based on the first sweep information, and orienting the first laser range finder relative to the first passive landmark based on the first landmark position. g. Detecting a first landmark position of the first passive landmark includes detecting a shape of the first passive landmark. h. Detecting a first landmark position of the first passive landmark includes detecting a reflectance threshold of the first passive landmark. i. Detecting a first landmark position of a first passive landmark includes detecting a color of the first passive landmark. j. Acquiring the first passive landmark includes identifying a first landmark position of the first passive landmark with at least one camera of the mobility platform, and directing a first laser rangefinder toward the first passive landmark based on the first landmark position. k. The method further includes tracking the first passive landmark with the first laser rangefinder based on odometry information from at least one odometry sensor of the mobility platform. l. The method further includes detecting a discontinuity in the information from the first laser range finder, and upon detecting the discontinuity in the information from the first laser range finder, reacquiring the first passive landmark with the first laser range finder. m. The method further includes detecting a discontinuity in the information from the first laser range finder, and upon detecting the discontinuity in the information from the first laser range finder, acquiring a third passive landmark located within the work site with the first laser range finder. n. An information discontinuity is a change in measured distance that exceeds a distance change threshold.

[0114]

[0140] In yet another example, a non-transitory computer-readable storage medium is provided having instructions stored thereon. The instructions, when executed by at least one processor, cause the at least one processor to perform a method for operating a mobility platform. The mobility platform includes a chassis, a first laser rangefinder disposed on the chassis, and a drive system including at least one wheel. The method includes acquiring a first passive landmark with the first laser rangefinder, moving the mobility platform along a drive path with the drive system, altering a first rangefinder pitch of the first laser rangefinder to maintain the first laser rangefinder within a first target altitude range above the first passive landmark as the mobility platform moves along the drive path, determining a chassis pitch of the mobility platform for each position of the mobility platform along the drive path based on the alteration of the first rangefinder pitch of the first laser rangefinder, and determining, for each position of the mobility platform along the drive path, an altitude of a work site at the at least one wheel based on the chassis pitch.

[0115]

[0141] Optionally, the method may include one or more of the following features: a. Changing the first rangefinder pitch includes commanding an actuator to move the first laser rangefinder. b. The drive system is a holonomic drive system. c. The at least one wheel is a four wheel, and the drive system includes four wheel assemblies, each of the four wheel assemblies including a wheel of the four wheels configured to rotate about a wheel axis, a first actuator configured to rotate the wheel about the wheel axis, and a second actuator configured to rotate the wheel about a pivot axis perpendicular to the wheel axis. d. The mobility platform further includes a second laser rangefinder disposed on the chassis, and the method further includes acquiring a second passive landmark with the second laser rangefinder, altering a second rangefinder pitch of the second laser rangefinder to maintain the second laser rangefinder within a second target altitude range on the second passive landmark as the mobility platform moves along the drive path, determining a second chassis pitch of the mobility platform for each position of the mobility platform along the drive path based on the alteration of the second rangefinder pitch of the second laser rangefinder, and determining an altitude of the work site at at least one wheel based on the chassis pitch and the second chassis pitch for each position of the mobility platform along the drive path. e. The method further includes generating, for each position of the mobility platform along the drive path, a topographical map of the drive path based on the elevation of the work site. f. Acquiring the first passive landmark includes sweeping the work site with a first laser range finder to collect first sweep information, detecting a first landmark position of the first passive landmark based on the first sweep information, and orienting the first laser range finder relative to the first passive landmark based on the first landmark position. g. Detecting a first landmark position of the first passive landmark includes detecting a shape of the first passive landmark. h. Detecting a first landmark position of the first passive landmark includes detecting a reflectance threshold of the first passive landmark. i. Detecting a first landmark position of a first passive landmark includes detecting a color of the first passive landmark. j. Acquiring the first passive landmark includes identifying a first landmark position of the first passive landmark with at least one camera of the mobility platform, and directing a first laser rangefinder toward the first passive landmark based on the first landmark position. k. The method further includes tracking the first passive landmark with the first laser rangefinder based on odometry information from at least one odometry sensor of the mobility platform. l. The method further includes detecting a discontinuity in the information from the first laser range finder, and upon detecting the discontinuity in the information from the first laser range finder, reacquiring the first passive landmark with the first laser range finder. m. The method further includes detecting a discontinuity in the information from the first laser range finder, and upon detecting the discontinuity in the information from the first laser range finder, acquiring a third passive landmark located within the work site with the first laser range finder. n. An information discontinuity is a change in measured distance that exceeds a distance change threshold.

[0116]

[0142] Various aspects of the present disclosure may be used alone, in combination, or in various configurations not specifically discussed in the embodiments described above, and therefore are not limited in application to the details and arrangements of components set forth in the above description or illustrated in the drawings. For example, aspects described in one embodiment may be combined in any manner with aspects described in other embodiments.

[0117]

[0143] Additionally, the embodiments described herein may be embodied as methods, examples of which are provided. The acts performed as part of a method may be ordered in any suitable manner. Thus, while exemplary embodiments may show acts as sequential, embodiments may be constructed in which acts are performed in a different order than depicted, including performing some acts simultaneously.

[0118]

[0144] Additionally, some actions have been described as being performed by a "user." It should be understood that a "user" need not be a single individual, and that in some embodiments actions attributed to a "user" may be performed by a team of individuals and / or an individual in combination with computer-assisted tools or other mechanisms.

[0119]

[0145] While the present teachings have been described in conjunction with various embodiments and examples, it is not intended that the present teachings be limited to such embodiments or examples. On the contrary, the present teachings encompass various alternatives, modifications, and equivalents, as will be appreciated by those skilled in the art. Accordingly, the foregoing description and drawings are by way of example only.

Claims

1. A mobility platform configured to perform one or more tasks in a work site including a first passive landmark located at a first known landmark location and a second passive landmark located at a second known landmark location, Chassis and A drive system supporting the chassis, comprising at least two wheels, and configured to move the mobility platform within the work site, A first laser rangefinder is positioned on the chassis at a first location, A second laser rangefinder is positioned on the chassis at a second position different from the first position, The first passive landmark is acquired by the first laser rangefinder, The second passive landmark is acquired by the second laser rangefinder, The first distance measured by the first laser rangefinder between the first position and the first known landmark position, and The second distance measured by the second laser rangefinder between the second position and the second known landmark position. Based on this, the first position of the chassis is determined, The first attitude of the mobility platform is determined based on first yaw angle information from at least one of the first laser rangefinder and the second laser rangefinder. At least one processor configured as follows and A mobility platform that includes [this].

2. The drive system includes a plurality of wheel assemblies, and each of the plurality of wheel assemblies is A wheel configured to rotate around a wheel axle, A first actuator configured to rotate the wheel around the wheel axle, A second actuator configured to rotate the wheel around a pivot axis perpendicular to the wheel axle, Includes, The mobility platform according to claim 1, further comprising a plurality of wheel odometers, each of which is associated with an individual wheel of a four wheel assembly and configured to measure the distance traveled by the individual wheel, and the at least one processor further configured to estimate the change in the position of the chassis from the first position based on odometry information from the plurality of wheel odometers.

3. The mobility platform according to claim 1, further comprising a marking device disposed on the chassis and configured to deposit marking material on the floor of the work site.

4. The acquisition of the first passive landmark by the first laser rangefinder is The first laser rangefinder is used to sweep the work site and collect first sweep information. Based on the first sweep information, the location of the first known landmark of the first passive landmark is detected, and Orienting the first laser rangefinder toward the first passive landmark based on the location of the first known landmark. The mobility platform according to claim 1, including the following:

5. The mobility platform according to claim 4, wherein detecting the location of the first known landmark of the first passive landmark includes detecting the shape of the first passive landmark.

6. The system further includes at least one camera to acquire the first passive landmark. Identifying the location of the first known landmark of the first passive landmark with at least one camera, and Orienting the first laser rangefinder toward the first passive landmark based on the location of the first known landmark. The mobility platform according to claim 1, including the following:

7. The at least one processor, based on information from the at least one camera, The first passive landmark is tracked using the first laser rangefinder. The second passive landmark is tracked using the second laser rangefinder. The mobility platform according to claim 6, further configured as follows.

8. When at least one processor commands the drive system to stop the mobility platform at one or more task locations within the work site, and commands the drive system to stop, The first passive landmark is reacquired using the first laser rangefinder. The second passive landmark is reacquired using the second laser rangefinder. The first distance between the first position measured by the first laser rangefinder and the first known landmark position, and The second distance between the second position measured by the second laser rangefinder and the second known landmark position. Based on this, the second position of the chassis is determined, The second attitude of the mobility platform is determined based on second yaw angle information from at least one of the first laser rangefinder and the second laser rangefinder. The mobility platform according to claim 11, further configured as follows.

9. The aforementioned at least one processor, The discontinuity of the first distance measured by the first laser rangefinder is detected, When the discontinuity in the first distance measured by the first laser rangefinder is detected, the first laser rangefinder acquires a third passive landmark located within the work site at the position of the third known landmark. The mobility platform according to claim 1, further configured as follows.

10. The mobility platform according to claim 9, wherein the discontinuity of the first distance measured by the first laser rangefinder is a change in the measured first distance that exceeds a distance change threshold.

11. The aforementioned at least one processor, The crossover point between the first laser rangefinder and the second laser rangefinder is determined within the movement of the mobility platform to the third attitude. At the crossover point, the first passive landmark is acquired by the second laser rangefinder. At the aforementioned crossover point, the second passive landmark is acquired by the first laser rangefinder. The mobility platform according to claim 8, further configured as follows.

12. The aforementioned at least one processor, The third passive landmark, positioned at the location of the third unknown landmark, is acquired by the first laser rangefinder. The first position of the chassis, The third distance measured by the first laser rangefinder between the first position and the third unknown landmark position, and Yaw angle information from the first laser rangefinder The location of the third unknown landmark is determined based on this. The mobility platform according to claim 1, further configured as follows.

13. A method for operating a mobility platform at a work site, the mobility platform comprising a chassis, a first laser rangefinder positioned at a first location on the chassis, a second laser rangefinder positioned at a second location on the chassis, and a drive system, the method being: To acquire a first passive landmark located at a first known landmark location using the first laser rangefinder, Acquiring a second passive landmark located at a second known landmark location using the second laser rangefinder, The first distance measured by the first laser rangefinder between the first position and the first known landmark position, and The second distance measured by the second laser rangefinder between the second position and the second known landmark position. The first position of the chassis is determined based on the above, and The first attitude of the mobility platform is determined based on first yaw angle information from at least one of the first laser rangefinder and the second laser rangefinder. Methods that include...

14. Obtaining the first passive landmark mentioned above is The first laser rangefinder is used to sweep the work site and collect first sweep information. Based on the first sweep information, the location of the first known landmark of the first passive landmark is detected, and Orienting the first laser rangefinder toward the first passive landmark based on the location of the first known landmark. The method according to claim 13, including the method described in claim 13.

15. The method according to claim 14, wherein detecting the location of the first known landmark of the first passive landmark includes detecting the shape of the first passive landmark.

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