Control of automated guided vehicle with forklift capability

Abstract

The invention relates to a method for monitoring and controlling automated guided vehicle navigation. The vehicle includes a fork, a primary sensor, a secondary sensor, and a controller. The method includes monitoring movement of the vehicle between a first position and a second position in a normal mode, and monitoring movement of the vehicle between the second position and a target position in an object handling mode. The monitoring in the object handling mode includes establishing a distance change between the vehicle and the object at two points in time based on a distance obtained by the primary sensor, measuring a distance traveled by the vehicle during the two points in time by the secondary sensor, and comparing the distance change and the measured distance, and determining whether the movement of the vehicle needs to be corrected based on the comparison result.

Description

Technical Field

[0001] The invention relates to a method of controlling an automated guided vehicle comprising a fork and an automated guided vehicle comprising a fork having at least one tine. Background Art

[0002] In the prior art, it is known from EP3729345 to control a vehicle to engage and disengage a pallet. The positioning of the vehicle before penetrating the pallet with the forks is based on a baseline geometric representation of the face of the pallet. The baseline geometric representation is established from sensor data and automated guided vehicle positioning data. It can be determined that the deviation of the updated geometric representation from the baseline geometric representation exceeds a threshold value, and in response, the movement of the vehicle can be adjusted.

[0003] The control method disclosed in EP3729345 is sensitive to errors in the positioning data and the proposed control method does not identify situations where a pallet is pushed against a wall or other infrastructure / object and / or where the drive wheels of the AGV slip. Summary of the invention

[0004] The inventors have recognized the above-mentioned problems and challenges associated with the navigation of automated guided vehicles to avoid pushing or dragging pallets, and have addressed these problems through the present invention as described below.

[0005] In one aspect, the invention relates to a method of monitoring navigation of an automated guided vehicle in an object handling mode of operation, the automated guided vehicle comprising forks, a primary sensor, a secondary sensor, and a controller for controlling the movement of the automated guided vehicle, the method comprising the steps of:

[0006] monitoring movement of the automated guided vehicle between a first position and a second position while operating in a normal mode,

[0007] monitoring movement of the automated guided vehicle between the second location and a target location while operating in the object handling mode,

[0008] Wherein, the monitoring in the object loading and unloading mode includes:

[0009] establishing a change in the distance between the automated guided vehicle and the object over a period of time between two points in time based on distance measurements obtained by the primary sensor,

[0010] a distance measured by the secondary sensor that the automated guided vehicle travels during the time period,

[0011] The established distance change is compared to the measured distance representation, and based on the comparison, it is determined whether a correction of the movement of the automated guided vehicle is required.

[0012] This method of monitoring the movement of an automated guided vehicle is advantageous because it is based on two different and specific travel distance monitoring techniques. Furthermore, the monitoring method has the advantage that it can be implemented with existing sensors, in which the primary sensor is dependent on the object to be loaded or unloaded by the automated guided vehicle and the secondary sensor is independent of the object to be loaded or unloaded by the automated guided vehicle.

[0013] By using two different measuring techniques, at least one of which depends on the object to be loaded and unloaded, errors in loading and unloading objects, such as pushing objects against walls and slipping of the wheels of the automated guided vehicle, can be detected and therefore subsequently taken into account in the control of the movement of the automated guided vehicle.

[0014] Furthermore, an advantage of the invention is that it can be used in a docking mode and in an undocking mode. In the docking mode, when the automated guided vehicle approaches an object, such as a pallet, which is at a target position, there is a risk that the pallet is pushed by the forks of the automated guided vehicle. In the undocking mode, when an object, such as a pallet, is positioned at its target position and picked up by the automated guided vehicle, there is a risk that the pallet is dragged while the automated guided vehicle moves away from the pallet. With the existing sensors of the automated guided vehicle according to the invention, both situations can be detected and subsequently compensated for in the control of the automated guided vehicle.

[0015] An automated guided vehicle should be understood as any automated guided vehicle or robot that autonomously navigates (i.e., interacts with predetermined map information and objects sensed from the surroundings of the automated guided vehicle) as described above. Therefore, such automated guided vehicles are sometimes also referred to as autonomous mobile robots, self-driving and semi-automated forklifts.

[0016] The first position may be understood as the position from which the automated guided vehicle starts its travel towards the second position. The first position may be, for example, a position where the automated guided vehicle changes direction of movement (e.g. from forks moving at the rear to forks moving at the front), a waypoint, a starting position, etc.

[0017] The second position may be understood as a position where the automated guided vehicle changes direction of motion in front of a target position where an object such as a pallet is to be dropped off or picked up.

[0018] Alternatively, if the direction of motion does not change, the second position may be the point at which the automated guided vehicle is aligned with the target position (ie, when the automated guided vehicle reaches the predetermined target position without further adjustment of the direction of motion).

[0019] The target position is to be understood as the position where the object is to be picked up or dropped off. The exact coordinates of the target position may not be known in advance, so the target position may be "at the end of a row of objects", the first object in a planned row, between objects / obstacles, etc. Therefore, the automated guided vehicle is controlled towards the target position in normal operating mode, and when approaching the target position, it is correctly positioned according to the target position.

[0020] Positioning according to the target position is called docking mode, i.e. docking mode refers to the situation when the automated guided vehicle is approaching the target position (with or without the forks carrying an object / load). On the other hand, when the automated guided vehicle moves away from the target position (with or without the forks carrying an object / load), this is called undocking operation mode.

[0021] The normal operating mode is to be understood as an operating mode in which the automated guided vehicle is controlled based on a navigation system, for example, including a map of the area. Such a map may define the positions or coordinates of obstacles, areas that the automated guided vehicle cannot enter, etc. In the normal operating mode, the front sensors (e.g., LiDAR) are used in conjunction with the controller's map to determine the position / coordinates of the automated guided vehicle on the map.

[0022] The object handling operation mode is used only at a target location close to an object to be dropped off or picked up by an automated guided vehicle. In other words, the object handling mode may include a docking mode and an undocking mode, wherein the docking mode refers to positioning the automated guided vehicle at the target location and moving the automated guided vehicle toward the target location. Conversely, the undocking mode refers to the movement of the automated guided vehicle away from the target location, i.e. when an object is dropped off or picked up. "Close" should be understood as closer than, for example, 2 meters of the target location. In the object handling mode, the movement of the automated guided vehicle is monitored (and controlled) only by the sensor according to the present invention. Therefore, according to the present invention, a navigation system and a map are not required to drop off or pick up objects.

[0023] The established distance change is the distance traveled by the automated guided vehicle during a period of time. The primary sensor measures the distance from the sensor to the object at the beginning of the period of time and at the end of the period of time, and the controller subtracts the two measurements to obtain the established distance change. The time period does not have to be continuous, but can be selected from every 2, 3, 4, etc. samples of the distance measurements of the primary sensor.

[0024] The measured distance representation is used to determine the distance that the automated guided vehicle has moved during a period of time. The measured representation may be a direct measurement of the distance performed by the secondary sensor, or it may be an input from the secondary sensor that needs to be processed to determine the actual distance that the automated guided vehicle has moved. It should be noted that the secondary sensor may also be used as a reference to determine whether the automated guided vehicle is moving, i.e., for example, whether one or more wheels are slipping.

[0025] The measured distance representation is measured continuously while the automated guided vehicle is moving or while the wheels of the automated guided vehicle are turning (if the wheels are slipping, the expected distance is not measured.) Therefore, additional calculations may be required to establish the measured distance, but line of sight between the secondary sensor and the object is not required to establish the distance traveled, unlike the case with the primary sensor.

[0026] The continuous time points may be start times and end times that define a time period in which the travel distance is established.

[0027] In an exemplary embodiment of the present invention, the object handling mode includes a docking operation mode and / or an undocking operation mode.

[0028] As mentioned, the object handling modes of operation may include a docking mode of operation and an undocking mode of operation. Monitoring and controlling the positioning of the automated guided vehicle may be similar in the docking mode and the undocking mode.

[0029] The object handling mode may also include controlling the raising and lowering of the forks. Thus, when the automated guided vehicle is correctly docked at the loading and unloading location where the object is to be picked up or dropped off, the forks may be raised or lowered. Subsequently, the automated guided vehicle is undocked, i.e. moved away from the loading and unloading location, with or without the object.

[0030] Throughout this document, the present invention will be described primarily with reference to the docked mode of operation, keeping in mind the above-mentioned similarities between the docked mode and the undocked mode.

[0031] Thus, the docking operation mode is understood to be a control mode in which, without an object, the automated guided vehicle is controlled to move towards an object to be lifted / repositioned, for example by lifting the object. The docking mode may also include a control mode in which, with an object, the automated guided vehicle is controlled to move towards a target position where the object is to be positioned, for example by lowering the object until it is positioned, for example, on the ground.

[0032] The undocking mode is understood to be a control mode in which, with an object, the automated guided vehicle is controlled to move away from a position where the automated guided vehicle engages the object, such as by lifting the object with a fork. The undocking mode may also include a control mode in which, without an object, the automated guided vehicle is controlled to move away from a position where the object has been positioned.

[0033] The position of the object (where the object is put down or picked up) may be referred to as the loading and unloading position. Thus, the loading and unloading position should be understood as the position of the automated guided vehicle when it is controlled to raise or lower its forks.

[0034] It should be mentioned that an object may be referred to as a target object or a load in this document.

[0035] In an exemplary embodiment of the invention, if the comparison results in a difference between the established distance change and the measured travelled distance representation being greater than a maximum threshold, a correction of the movement of the automated guided vehicle is required.

[0036] In an exemplary embodiment of the invention, control of the automated guided vehicle during the object handling mode is controlled according to a first threshold value and a second threshold value.

[0037] In an exemplary embodiment of the invention, said established distance variation is established based on a direct distance measurement between said primary sensor and said object.

[0038] If the automated guided vehicle comprises only one tine, the lidar / primary sensor is preferably positioned between the two tines and above the single tine at the automated guided vehicle. This position is advantageous because the distance measured is a direct distance that does not require any processing before use.

[0039] In an exemplary embodiment of the present invention, the scanning lidar sensor further measures a first corner distance and a second corner distance of the object located at the target position.

[0040] It is advantageous to measure the distance to the corner of the object several times during the time that the automated guided vehicle approaches the object at the target location, because comparing these distances indicates whether the automated guided vehicle is approaching perpendicular to the object or whether it needs to be adjusted to approach perpendicularly.

[0041] In an exemplary embodiment of the invention, the automated guided vehicle comprises, in addition to the primary sensor, a laser distance sensor.

[0042] This is advantageous because, for example, scanning LiDAR sensors may not provide valid distance measurements at distances less than, for example, 30 cm. Therefore, in order to ensure the ability to establish the correct distance between automated guided vehicles when the distance between them is less than, for example, 30 cm, a laser distance sensor may be used.

[0043] In an exemplary embodiment of the invention, the secondary sensor measures the distance travelled by the wheels of the automated guided vehicle.

[0044] Measuring the distance travelled by the wheels is advantageous because it has the effect that the measured distance is independent of the object at the target location and therefore independent of the situation in which the object is moving. Therefore, based on the measurements from the secondary sensor and from the primary sensor, it can be determined whether the automated guided vehicle is pushing an object. It should be mentioned that the measurements representing the distance may need to be converted into actual distances before they can be used for any control and comparison. In this document, references to the measured distance may be references to distances derived from direct measurements representing the distance or directly measured distances.

[0045] In an exemplary embodiment of the invention, the automated guided vehicle comprises two secondary sensors.

[0046] Implementing secondary sensors at two or more wheels of an automated guided vehicle is advantageous because the measured distances can be compared. Thus, if one secondary sensor measures a longer distance than another, the controller knows that the automated guided vehicle is turning, i.e. not moving in a straight line.

[0047] In an exemplary embodiment of the present invention, the distance traveled by the automated guided vehicle is further measured by a tertiary sensor.

[0048] The tertiary sensor may be, for example, an inertial measurement unit mounted on an automated guided vehicle, which is capable of calculating the forces, angular rates, and direction of motion of the automated guided vehicle. The inertial measurement unit may include a gyroscope, a magnetometer, and an accelerometer.

[0049] The inertial measurement unit can measure the distance traveled or it can be converted into a representation of the distance traveled. In addition, the inertial measurement unit can measure the direction of the distance traveled. Both measurements are independent of the line of sight to the object, in fact it can be completely independent of the object. Therefore, by using an inertial measurement unit together with, for example, the primary sensor and / or the secondary sensor, it can be determined whether an object is being pushed by an automated guided vehicle or whether the wheels of the automated guided vehicle are slipping.

[0050] Furthermore, it should be mentioned that the inertial measurement unit can be used to verify the distance established or measured by the secondary sensor. This is advantageous, for example, in the event of wheel slip. In this case, the secondary sensor may indicate a certain movement, while the measurement of the inertial measurement unit (e.g., based on acceleration) may indicate less movement or no movement.

[0051] In an exemplary embodiment of the invention, the method further comprises the step of stopping the automated guided vehicle if the direct distance does not change but the measured distance changes.

[0052] In the event that the distance measured by the secondary sensor changes but the direct distance measured by the scanning lidar sensor does not change, movement of the automated guided vehicle may cease, as this may indicate that the object is being pushed or dragged.

[0053] In an exemplary embodiment of the invention, the method further comprises the step of adjusting one or more control parameters of the automated guided vehicle if the direct distance does not change but the measured distance changes.

[0054] Adjusting the control parameters can result in a change in the direction of movement of the automated guided vehicle, a change in the height of the forks, etc.

[0055] The methods described in paragraphs

[0005] -

[0048] and

[0050] -

[0051] are implemented in the apparatus described in paragraph

[0052] .

[0056] In one aspect, the invention relates to a method of controlling an automated guided vehicle according to any of the preceding paragraphs in a normal operating mode followed by an object handling mode of operation followed by the normal operating mode, the automated guided vehicle comprising forks, a primary sensor, a front sensor, a secondary sensor, a data storage and a controller for controlling the movement of the automated guided vehicle, wherein the method comprises the following steps:

[0057] controlling movement of the automated guided vehicle in the normal operating mode during a first time period, wherein the normal operating mode includes navigating the automated guided vehicle based at least on a digital representation of an area in which the automated guided vehicle is to move and input from the front sensor,

[0058] controlling movement of the automated guided vehicle in the object handling mode of operation during a second time period that is shorter than the first time period, wherein the object handling mode of operation includes navigating the automated guided vehicle based on at least input from the primary sensor and input from the secondary sensor,

[0059] controlling movement of the automated guided vehicle in the normal operating mode during a third time period that is longer than the second time period, wherein the normal operating mode includes navigating the automated guided vehicle based at least on the digital representation of the area in which the automated guided vehicle is to move and input from the front sensor,

[0060] Controlling or navigating the automated guided vehicle in both the normal operating mode and the object handling operating mode during the subsequent time period is advantageous because accuracy is a focus and is increased when necessary. Furthermore, an overall improvement to the autonomous system including the object handling automated guided vehicle is achieved. Such improvements reduce wear and damage to the object due to the high accuracy in the operation of the automated guided vehicle. Furthermore, the number of errors requiring manual interaction (such as dragging or pushing an object) is reduced, which is very advantageous because this is a very time-consuming error in the autonomous system of the automated guided vehicle.

[0061] In one aspect, the invention relates to an automated guided vehicle comprising a fork, a primary sensor, a secondary sensor and a controller, the controller controlling the movement of the automated guided vehicle in a normal operating mode and in an object handling operating mode according to the method described in any of the preceding paragraphs,

[0062] Wherein, when operating in the object loading and unloading operation mode,

[0063] The primary sensor is configured to establish a change in the distance between the automated guided vehicles over a period of time between two points in time,

[0064] the secondary sensor being configured to measure a distance representative of a distance traveled by the automated guided vehicle during the time period,

[0065] The controller is configured to compare the established distance change with the measured distance and determine whether a correction of the movement of the automated guided vehicle is required based on the comparison result, and

[0066] Wherein, the controller is configured to control the movement of the automated guided vehicle in the object handling operation mode according to the comparison result. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] For a more complete understanding of the present disclosure, reference is now made to the following brief description in conjunction with the accompanying drawings and specific embodiments, wherein like reference numerals represent like parts. The accompanying drawings illustrate embodiments of the present invention, and elements of different drawings may be combined within the scope of the present invention:

[0068] FIG. 1 a shows an automated guided vehicle approaching an object at a target location according to an embodiment of the present invention,

[0069] FIG. 1 b shows a side view of an automated guided vehicle according to an embodiment of the present invention,

[0070] FIG. 1c shows a rear view of an automated guided vehicle according to an embodiment of the present invention,

[0071] FIG. 1 d shows an alternative automated guided vehicle in side view,

[0072] Figure 2 shows the movement of an automated guided vehicle picking up a load,

[0073] Figure 3 An automated guided vehicle is shown approaching a load, and

[0074] Figure 4 A flow chart showing the control of an automated guided vehicle picking up a load. DETAILED DESCRIPTION

[0075] The invention has been described in terms of exemplary embodiments intended only to illustrate the principles and implementations of the invention. A skilled person will be able to provide several embodiments within the scope of the claims.

[0076] Figure 1A-Figure 1C An example of an automated guided vehicle AGV according to the present invention is schematically shown. FIG. 1d shows a second example of an automated guided vehicle AGV according to the present invention. The automated guided vehicle AGV is also referred to as AGV in this document. FIG. 1a shows the AGV and an object OB to be picked up by the AGV in a top view. FIG. 1b shows the AGV and the object OB in a side view, and FIG. 1c shows the AGV from the rear.

[0077] Figure 1A The AGV shown includes forks FO, making the AGV suitable for lifting a pallet PA carrying a load LO, which together may be referred to as an object OB or target object. The object OB is shown positioned at a target position TP. Figure 1A , the position of the object OB coincides with the target position TP, which in this embodiment is larger than the object OB. The actual position of the object OB may not be known in advance by the controller, but is determined only by the controller CO with reference to the position of the AGV and, for example, also based on sensor inputs from the AGV's surroundings. Thus, with the known position of the AGV and knowledge of, for example, the dimensions of the objects (load and pallet), the controller CO is able to determine and record the actual position of the object OB at least when the engagement between the forks FO and the pallet PA is established.

[0078] It should be mentioned that when referring to an AGV with forks, it is meant that the AGV includes one or more fork tines / forks, making the AGV suitable for lifting objects such as pallets, for example, carrying loads, or pipes, which can be wrapped around the loads.

[0079] The illustrated AGV includes a controller CO that controls the movement of the AGV. The movement includes driving the AGV forward and backward relative to the fork FO, turning the AGV clockwise and counterclockwise, lifting the fork FO, stopping the AGV, adjusting the speed of the movement, etc. The control is based on control software stored in a data storage device associated with the controller (i.e., as part of the controller CO and sensor input or communicating with the controller CO and sensor input). The controller CO further controls the movement according to different operating modes. The controller can be a standard programmable logic controller or a dedicated AGV controller designed specifically for its purpose. As known to those skilled in the art, in addition to the data storage device, the controller can also communicate with / include communication interfaces, position determination equipment (such as a global positioning system), and other elements required to safely navigate the AGV.

[0080] The controller may allow the AGV to travel at a speed of, for example, 2 m / s during normal operation, and travel in docking mode / undocking mode at one or more reduced travel speeds. An example of such a reduced travel speed may be 0.3 m / s. The speed and when to allow the speed may be determined, for example, by the distance to the load, such that the slowest speed is when the forks are closest to the load. In this way, speed control may be provided based on the distance to the load.

[0081] The control software may include a map of the area in which the AGV will move. The map may include the location of obstacles, allowed areas / not allowed areas, target locations, starting locations, aisles, etc. It should be mentioned that the map may be a virtual map that only includes the coordinates of map elements such as the above-mentioned obstacles, locations and obstacles, etc.

[0082] The sensor input can be provided by a series of sensors. The most important ones with regard to the present invention are the so-called primary sensors PS and secondary sensors SS. However, tertiary sensors and additional sensors can also provide relevant inputs.

[0083] The primary sensor PS is also referred to as a rear sensor because it is positioned opposite to the direction of movement of the AGV when controlled according to the normal operating mode. The primary sensor PS is typically of the distance sensor type and may be implemented as a scanning LiDAR sensor, which is an example of a common sensor type for AGVs. Alternatively, the primary sensor PS may be implemented as a laser distance sensor.

[0084] Thus, the change in distance between the AGV and the object OB during a period of time can be determined from the primary sensor PS. The primary sensor PS is characterized in that it relies on reflective objects in order to be able to measure the distance. The AGV may also include a front sensor that is also implemented as, for example, a scanning lidar sensor. Thus, based on the rear sensor and the front sensor, the controller can establish a digital representation of the AGV's surroundings and is thereby able to locate itself and the object OB in the digital representation. In FIG. 1a , the dotted line between the primary sensor PS and the object OB indicates that the direct distance DD between the AGV and the object OB is measured.

[0085] The second sensor SS is typically of the motion sensor type, from which the position over time can be measured or derived. The secondary sensor SS can be implemented as an odometer sensor, which measures a distance traveled during a period of time, or a distance traveled. The secondary sensor SS is characterized in that it does not rely on an object capable of performing measurements of the distance traveled by the AGV.

[0086] The tertiary sensor TS (not shown in FIGS. 1a-1d ) may be implemented as an inertial measurement unit IMU that uses, for example, accelerometers and gyroscopes to determine the motion characteristics of the AGV and the distance traveled by the AGV. Additional sensors may also be used. Such additional sensors may be of the types described above or other types. An example of an additional sensor for an AGV is referred to as a front sensor FS (see Figure 2 ), which is positioned opposite the forks and is used in normal operating mode when the AGV is moving. The corner sensor CS shown in FIG1d also belongs to the category of additional sensors. The corner sensor CS can be a scanning lidar type as a primary sensor. In addition, an angle odometer also belongs to the category of additional sensors, via which the angle at which the AGV turns can be determined.

[0087] FIG. 1b shows a side view of Figure 1AThe object OB and the AGV are located on the warehouse floor WF. Note that the object OB can be positioned on a pallet PA, which together with the object is referred to as a load LO. The pallet PA can be engaged with the forks FO of the AGV and in this way lifted and transported from one location to another. The illustrated AGV includes a drive wheel DW, two casters CW, and two fork wheels FW. The drive wheel DW is typically positioned below the center of the AGV, while the casters are positioned at the center of each side of the AGV. The fork wheels are positioned as a support for the forks when lifting the object OB.

[0088] Figure 1c shows the AGV from the rear as it moves towards an object and is used to illustrate the position of the wheels DW, CW, FW of the AGV. In fact, it can be argued that the AGV shown in Figure 1c is seen in a front view because when controlled in normal operation, the AGV is usually driven with the forks pointing in the direction opposite to the direction of travel. It is further noted that the wheels shown are of the same size, however it should be mentioned that typically the drive wheel DW will be larger than the castor wheel CW and the fork wheel FW.

[0089] Figure 1D An alternative example of an AGV is shown. This particular illustration shows a side view of an AGV located in a flat floor environment such as a warehouse floor WF.

[0090] The AGV includes a sensing system in the form of two scanning LiDAR sensors placed at opposite corners of the AGV, hence referred to as corner sensors CS. Given the positioning of the corner sensors CS, scanning signals are permitted to travel from the corner scanners CS into the robot's surroundings, each of the two corner scanners CS being able to scan an angle of approximately 270 degrees. The corner scanners CS are thus able to efficiently cover all 360 degrees around the AGV horizontally.

[0091] Furthermore, three wheels can be seen in the illustration, one of the two drive wheels and two of the four corner wheels CW. The AGV may have a total of six wheels, wherein the visible wheels obstruct the view of the remaining wheels.

[0092] Some of the wheels are responsible for guiding the robot, such as the casters CW located at the corners of the AGV. Other wheels, called drive wheels DW, are associated with one or more odometers that provide an indication of the distance traveled by the AGV. This is useful for supporting navigation, especially when there are no obstacles in the surroundings of the AGV, which can be used to determine its position, for example, relative to a map of the area. In other embodiments, the same wheel is used for guidance and distance measurement.

[0093] Furthermore, the AGV has a support surface SI for receiving items to be transported by the AGV. The support interface SI may be implemented as a fork (not shown) for lifting, for example, a pallet PA located at one of the ends of the AGV. Alternatively, as in the illustrated embodiment of FIG. 1d , the AGV may be intended to travel under an object / load to lift and transport a load LO, which may be positioned on a shelf.

[0094] The AGV further includes a robot control system, which may include a controller CO and a safety controller (not shown). In addition, the AGV may include a sensor system, such as the above-mentioned odometer, inertial measurement unit, etc., which are shown as secondary sensors SS and tertiary sensors TS. These elements are integrated inside the AGV, represented by a dashed rectangle in the figure.

[0095] The robot control system can control the planned robot routes, the creation of subroutes, the steering of the AGV (via wheels), and the execution of the Monte Carlo localization algorithm used to determine the position of the AGV in the physical environment. The safety controller provides safety functions such as emergency braking to avoid collisions with people and obstacles.

[0096] The robot control system and the sensing system including the above-mentioned sensors are communicatively connected so that the measurements performed by the scanning lidar sensor can be provided to the control system so that these measurements can be processed. The input from the sensors of the sensing system to the control system can thus be used as a basis for manipulating and positioning the robot.

[0097] Optionally, the control system further provides an AGV state indicating the current operating condition of the AGV. For example, a first possible state indicates normal operation of the AGV, and a second state indicates limited mobility of the AGV.

[0098] Figure 2 An embodiment of the invention is shown in which the AGV is controlled in a normal mode during a first portion of the distance between a first position 1PO and a target position TP. More specifically, the first portion (shown by two arrows) is between the first position 1PO and a second position 2PO, wherein the first position is shown as a dashed AGV and the second position is shown as a solid AGV. Furthermore, during a second portion of the distance between the first position 1PO and the target position TP, the AGV is controlled in an object handling mode. More specifically, during Figure 2 In the illustrated embodiment, this second portion (indicated by the arrow) is located between the second position 2PO and the target position TP. The target position TP coincides with the position of the object OB in this illustration. In this embodiment, when the AGV approaches the object, this portion of the object handling mode may also be referred to as the docking mode. Note that the positions in this document may also be referred to as waypoints.

[0099] Object handling operation modes include docking (approaching a target location with or without a load), loading (raising or lowering the forks and thereby lifting or lowering the load), and undocking (moving away from a target location with or without a load). When not operating in object handling mode, the AGV operates in normal operation mode.

[0100] It should be mentioned that the actual position of the AGV when it has reached the target position TP and is ready to raise or lower the forks can be referred to as the loading and unloading position. Typically, the automated guided vehicle will not move in the loading and unloading position. However, when the automated guided vehicle approaches the target position TP, the automated guided vehicle can start to raise / lower the forks before the AGV comes to a standstill in the loading and unloading position. The reason for such a control strategy can be to reduce the loading and unloading time, i.e. the time that the AGV is in the object loading and unloading mode.

[0101] The first position 1PO can in principle be any starting position or location on the route of the AGV to the target position TP. It can be a charging station, where the AGV has positioned a load LO, a transfer of a zone or area, a transfer from driving in one aisle to another aisle, etc. Note that the aisles are illustrated as being defined by a first aisle side 1COS and a second aisle side 2COS. These sides can be defined, for example, by the front of a row of objects or obstacles, which can be stationary, such as walls.

[0102] In contrast to the first position 1PO, the second position 2PO is rather clearly defined, since it is located “in front of” the object OB to be picked up. Thus, when the fork FO is pointing at the object OB, the AGV is positioned at the second position 2PO and only minor (preferably no) adjustments are required to navigate the fork FO into the pallet slot. Ideally, the path traveled by the AGV from the second position 2PO toward the target position TP is perpendicular to the front of the object / pallet. Thus, the second position 2PO can be any distance “in front of” the object OB. Typically, this distance is limited by the width of an aisle or similar obstacle. Thus, the second position 2PO can be selected as a distance in the distance range DR between the object OB and the opposite aisle side (here the second aisle side 2COS), the aisle width, an opposite obstacle, etc.

[0103] The positioning of the second position 2PO may be predetermined, i.e. the coordinates of the first object OB in a row of objects may be specified by the control software or by a staff member communicating with the AGV via a user interface. Alternatively, the second position 2PO may be determined by the last object OB in a row of objects. Therefore, if the controller CO knows that it has positioned five objects OB or this information is provided from the AGV fleet controller, then by knowing the size of the object and the coordinates of the row, the controller CO can calculate the positioning of the target position and thereby the positioning of the second position 2PO. Alternatively, the coordinates of the target position TP may be provided to the controller CO from the fleet controller. This is correct for both docking mode and undocking mode. The controller CO may receive information on the size of the object to be picked up and the pick-up position (target position), and when it approaches, the scanning input from the scanning lidar sensor may be used to confirm that the correct object is at the target position.

[0104] The normal operating mode is based on input from the sensor system as described above, i.e. any available one of the primary sensor PS (e.g. rear sensor), secondary sensor SS (e.g. odometer), tertiary sensor TS (e.g. inertial measurement unit), front sensor FS and corner sensor CS. The input from the sensor system is used by the controller CO together with the area map information / information of permanent obstacles and / or information from the fleet controller to navigate the AGV.

[0105] Once the AGV is at a distance within the distance range DR from the target position, if the AGV is approaching the object OB, the control mode changes to the object handling mode, which is the docking mode, and if the AGV is moving away from the object OB, the object handling mode is the undocking mode.

[0106] It should be noted that once the AGV is in the second position 2PO, the scanning Lidar PS can scan the object OB / pallet PA to identify the pallet slot and thus the path to follow for the optimal engagement between the forks FO of the AGV and the object OB / pallet PA. Once the pallet position and pose are identified, the controller CO can establish the direct distance DD using only the scanning Lidar sensor.

[0107] Thus, it may happen that the scanning LiDAR sensor is not able to fully scan the load when the AGV is approaching it, and thus features such as the pallet position, its slots, pose, geometry, engagement areas, etc. may be identified when the AGV is in the second position or indirectly when it is approaching. Load features may thus be identified from stored data such as width and length, the load may include markings based on which the AGV is able to identify load features and position, for example object features and position on a pallet if the pallet is an integral part of an object such as a beverage container, fish container, etc., etc.

[0108] The illustrated AGV does not carry the object OB but is about to approach the object OB to pick up the object OB, so the controller CO changes the operation mode from the normal operation mode to the docking mode of the object handling mode.

[0109] In the object handling operation mode, it is assumed that there is no obstacle between the AGV and the object OB. It is reasonable to assume that when the AGV is turned and located at a position in the second position range DR, at least one of the front scanner FS, the primary scanner PS or the corner scanner CS scans the area between the AGV and the object OB.

[0110] Thus, in docked mode (and similarly in undocked mode), the AGV is now controlled based on input from the primary sensor PS and the secondary sensor SS.

[0111] As mentioned above, the primary sensor PS can also be referred to as a rear sensor and is implemented as a scanning lidar sensor that measures the direct distance DD between the object OB and the AGV. In this way, the distance between the object OB and the AGV is measured with a sampling frequency of, for example, less than one second. Therefore, the change in the distance between the AGV and the object OB can be established based on the measurement of the direct distance DD performed at two different time points.

[0112] It should be noted that the sampling frequency / scanning speed is fast enough compared to the speed at which the AGV moves to ensure that the AGV does not collide with obstacles identified by the scanner.

[0113] As mentioned, the secondary sensor SS may be of the odometer type, measuring the distance travelled by its associated wheel. Thus, independently of the object OB, the controller CO is able to determine the distance travelled by the AGV between two different points in time based on the input from the secondary sensor.

[0114] When two different points in time are identical, the controller CO can compare the distances (established distance and measured distance) and thus monitor whether the AGV is moving towards the object OB as expected. If for some reason this is not the case, the controller CO can react by adapting or adjusting the control of the AGV.

[0115] If monitoring shows a difference in distance according to two different distance measurement methods, controls (such as turning, stopping, and reversing the AGV) may need to be adjusted. Therefore, if the wheels of the AGV are slipping, the odometry measurement will imply that the AGV is moving, but if the direct distance measured by the primary sensor does not change, it indicates that the wheels are slipping. This may happen, for example, if the object is pushed against an obstacle, wall, or other infrastructure. In addition, the above method can also indicate that the object OB is dragged when undocking, for example, if the forks are not lowered enough to disengage from the pallet PA.

[0116] Figure 3 An embodiment of the invention is shown in which the AGV further comprises a tertiary sensor in the form of an inertial measurement unit IMU. Furthermore, as shown, the scanning Lidar sensor PS also measures the distance to the corners of the object OB.

[0117] The inertial measurement unit IMU can also be used to determine if the drive wheels DW of the AGV are slipping. Therefore, without the direct distance DD, it may be difficult to determine slipping using existing sensors of the AGV. The inertial measurement unit IMU may include at least a gyroscope and an accelerometer, so if there is no indication of acceleration from the inertial measurement unit IMU or an indication of less acceleration than expected and there is an indication of the distance traveled from the odometer, there is a high risk of slipping or pushing the object OB / pallet PA. Therefore, inputs from the odometer and from the inertial measurement unit IMU can be used to determine if the wheels are slipping or if the object is being pushed.

[0118] In the event that a mismatch is detected between the inputs from the odometry and the inertial measurement unit IMU, the controller CO can control the movement of the AGV in the opposite direction and can try to adjust the direction of movement to see if the forks are better positioned in the pallet slot and therefore do not push the pallet.

[0119] In addition to the direct distance DD, the scanning lidar sensor PS can also monitor the distance to the corners of the object 1CD, 2CD. Monitoring these corner distances 1CD, 2CD can be used to adjust the movement of the AGV so that the forks of the AGV reach the pallet mouth slot without hitting the pallet or the object and thereby damaging the load LO. Therefore, if the two corner distances 1CD, 2CD are not equal, this indicates that the AGV is not moving along a straight line (vertical) toward the object OB, and therefore the movement should be adjusted to reach such a straight line. If the distance sensed by the primary sensor PS indicates that the end of the fork is about to enter the pallet mouth slot and the primary sensor PS records an increased difference between the corner distances 1CD and 2CD at this point, this indicates that the pallet is pushed by one of the forks of the fork and the movement should be adjusted or stopped. Possibly, the AGV should travel back again toward the second position to end at a new docking position (new second position), and make additional attempts to approach the pallet and engage with the pallet taking into account the changed posture of the recorded pallet. Preferably, the AGV moves vertically toward the object OB. When the object OB is located on the pallet PA, vertical should be understood as approximately vertical, since the pallet slot is a few centimeters wider than the width of the forks, for example 2-3 centimeters.

[0120] Figure 3 The position of the AGV at a first time 1T (dashed line, second position) and a second time 2T (IP intermediate position) is further shown. This is to illustrate the distance DT travelled by the AGV between the two time periods, which is established from the two distance measurements made by the scanning lidar sensor PS and measured by the odometer.

[0121] As described above, the control of the AGV in the undocking mode is more or less the same as the control of the AGV in the docking mode. Obviously, when docking, i.e. approaching the target position, when the object is at the target position, the object can be used to establish a direct distance. When there is no object, the position of the object OB can be determined with reference to adjacent objects in a row or stationary obstacles, coordinates, etc. When undocking, i.e. moving away from the target position (with or without an object), if the object exists, the AGV can be controlled based on the distance to the object, or if no object is present at the target position, the AGV can be controlled based on the distance to the adjacent object, obstacle, coordinates, etc.

[0122] Wheel slip and drag on objects may be monitored in the same manner as described above with reference to the docking mode of operation.

[0123] Therefore, the main purpose in the undocking mode is to ensure that the load is not dragged behind the AGV. One way to terminate the undocking mode is to measure the distance traveled by the AGV. When this distance is the same as or longer than the length of the forks and there is a fixed distance between the load and the AGV, it can be concluded that the load is not dragged behind the AGV. Therefore, the control mode can be changed.

[0124] The docking operation mode may be started when the AGV is in the second position 2PO with its forks facing the target position and ready to move with its forks facing the target position TP. The docking mode may be stopped when the AGV reaches the loading and unloading position HP (i.e., where the forks are raised to engage with the object OB or lowered to position the object OB).

[0125] The undocking operation mode may start when the AGV moves from the loading and unloading position HP and returns towards the second position 2PO, i.e. when dropping an object by lowering the forks or picking up an object by raising the forks. The undocking operation mode may be terminated when the second position 2PO is reached or when the distance moved away from the object OB is longer than the forks.

[0126] Based on the above description, in one embodiment, the control of the AGV can follow Figure 4 The flowchart shown in Figure 4 In the process, the AGV will pick up the load and in step S1, in the normal operation mode, the AGV is controlled from the first position 1PO to the second position 2PO. The control includes the following steps: Figure 2 90 degree turn shown.

[0127] In step S2, the AGV is in a second position, ie the forks of the AGV are facing / pointing towards the load. The load is scanned for an identifier in an engagement position that can be used to provide information of the load, such as a pallet and / or an object.

[0128] In step S3, docking mode is started and the AGV moves towards the loading and unloading position where it will pick up the load. Encoders such as wired encoders are used during this step because the lidar scanner may be temporarily blinded or at least may not be able to see the entire load when the AGV approaches the load. During docking mode, the scanner can be used to determine the distance to the load, and encoders that measure the rotation of the wheels and pallet detectors can be used to control the movement of the AGV.

[0129] In step S4, the AGV reaches the loading and unloading position, the distance to the object / pallet is, for example, 2 cm, and the movement of the AGV stops, i.e. the docking mode is completed.

[0130] In step S5 , the forks are raised and the load is thereby lifted.

[0131] In step S6, the AGV enters the undocking mode and leaves the loading and unloading position and moves toward the second position. During this operating mode, the movement of the AGV receives input from the wheel / motor encoder.

[0132] In step S7, the AGV reaches a second position, a position in range DR, where it is safe to turn and subsequently move along the aisle towards the destination of the load the AGV is now carrying.When turning, the movement of the AGV is controlled according to the normal operating mode.

[0133] When the AGV approaches the target location with the load to be unloaded, the steps for controlling the AGV follow the Figure 4 The principle described.

[0134] As described above, the controller CO controls the movement of the AGV from a starting position to a target position in a control loop. The starting position (first position) may be a coordinate defining a physical position that may be derived from an area map. The starting position may be the positioning of the object OB in a row of objects, a charging station, etc. Thus, the control loop may start away from the target position TP. Thus, during a first time period, the AGV may be controlled according to a normal operating mode, characterized in that the control during this first time period is based on an area map and at least input from a front sensor FS (e.g., a scanning lidar sensor). The first time period may be relatively long, typically longer than 5 minutes.

[0135] The controller CO may receive information of the location of the target location, for example, from an external controller such as a fleet controller, from a human worker via a user interface, from a continuously repeated control routine, or the like.

[0136] When the position of the AGV is within a radius of, for example, less than two meters from the coordinates of the target position TP, the controller CO changes the operation mode to an object handling operation mode, more specifically, to a docking mode, because the AGV is approaching the target position TP.

[0137] During the object handling maneuvering mode, the controller CO may control the AGV based solely on the sensor input. The second time period for controlling the AGV according to the object handling mode is shorter than the first time period. The duration of the second time period is less than five minutes.

[0138] Sensor input is provided from at least one primary sensor PS (a rear sensor such as a scanning LiDAR sensor) and one secondary sensor SS (an odometer sensor). This means that the AGV can be controlled without reference to its surroundings (except for the object OB that may be to be picked up). Therefore, no area map, scanning of objects and their surroundings, etc. is required to control the AGV.

[0139] It should be mentioned that scanning of the AGV surroundings and the object OB surroundings may be required for safety reasons only.

[0140] When the object OB is lifted by the AGV or positioned by the AGV and moved away from the target location (undocking mode), a third time period may be started during which the controller CO controls the AGV again according to the normal operation mode. During this third time period, which is longer than the second time period, the AGV moves the object OB to a new target location, or the AGV moves to a new target location to pick up a new object OB. As described above, the control according to the normal operation mode is based on the area map and sensor input.

[0141] Therefore, the last part of the distance traveled by the AGV controlled in the docking operation mode from the second position 2PO to the object OB can be controlled based solely on the input from the odometer. Therefore, for example, in the last 0.5m, it is assumed that there are no obstacles between the object OB and the AGV, and therefore, in the last 0.5m, the AGV is controlled based solely on the odometer input and when the 0.5m distance has been reached. One reason for controlling based solely on the odometer is that the measurements provided by the scanning lidar sensor may be accurate over such short distances. Therefore, in this embodiment, especially during the last part of the distance to the object OB, the inertial measurement unit IMU can be used to determine whether slipping or pushing the object OB has occurred.

[0142] Alternatively, one or more laser range sensors may be used as input instead of or in addition to a scanning LiDAR sensor. In this way, the odometer input may be supplemented by input from another sensor type if desired.

[0143] The AGV may move at speeds in the range of 1.5m / s, however the speed may be reduced further when approaching an object (eg the last 0.5m).

[0144] It is mentioned that the determined distances and the measured distances from both sensor systems should be the same. Obviously, it is mentioned that these distances should be substantially the same, ie within eg a few centimeters, such as below 0.1 m or 0.05 m.

[0145] In addition, as described above, slipping, pushing or pulling can be detected and, in some cases, allowed. The distance at which an object is allowed to be pushed or pulled can vary. If, for example, the pallet PA is wrapped, the fork needs to break through the wrapping before reaching the optimal engagement position. The AGV can push the object OB until a breakthrough of the wrapping caused by the fork occurs. In this case, pushing the pallet PA may be allowed, for example, up to 0.05m. The breakthrough can be detected, for example, by comparing the distance measured by the odometer and the acceleration input from the inertial measurement unit. Once the fork has broken through the wrapping, the AGV may not be allowed to push the pallet PA more than a few centimeters, such as up to 0.02m.

[0146] Note that the lengths and times provided in this document are merely examples, which may vary between different applications due to, for example, the size of the object OB, the AGV, the area of ​​the warehouse floor WF, etc.

[0147] In an exemplary embodiment of the invention, the target position is defined by the actual position of the object.

[0148] Thus, the target location may be the desired or expected location of an object (to be picked up or dropped off), but the object may not be precisely located at the expected target location (e.g., at predetermined coordinates) on the warehouse floor. Thus, the target location and actual location of the object may differ slightly.

[0149] Thus, when the forks of the automated guided vehicle are fully engaged or disengaged from an object, a target position may be determined relative to the loading and unloading position of the automated guided vehicle.

[0150] "Slightly different" should be understood as within a few centimeters, such as within 10 centimeters from the target position. The difference may be caused, for example, by a pallet mouth slot that is wider than the tines of the fork, sensor feedback, errors in processing, etc.

[0151] Finally, it should be mentioned that the target position may be defined as, for example, an area wider than the circumference of the object, an area similar to the circumference of the object, a central position of the object, or the like.

[0152] In an exemplary embodiment of the present invention, the motion correction is performed by the controller.

[0153] Thus, according to the invention, when monitoring of the operation of the automated guided vehicle (i.e. the monitored change in distance / representation of the distance travelled) indicates that a motion correction is required, such correction can still be performed by the controller according to the invention. The required correction can be indicated if the difference between the distance measurement / representation of the distance is above a threshold, i.e. the control reacts to the difference in the distance measurement.

[0154] In an exemplary embodiment of the invention, the maximum threshold is lower than 0.3 m, preferably lower than 0.2 m, most preferably lower than 0.1 m.

[0155] The maximum threshold defines the maximum length that the automated guided vehicle is allowed to push or tow an object before the automated guided vehicle's motion toward or away from the object is stopped. Typically, less than 30 cm is allowable, but it can vary between different applications and therefore can sometimes be greater or less than 30 cm.

[0156] In an exemplary embodiment of the present invention, the maximum threshold is a total threshold, which is the sum of the first threshold and the second threshold.

[0157] In an exemplary embodiment of the present invention, the first threshold is below 0.2 m, preferably below 0.1 m, most preferably below 0.05 m.

[0158] In an exemplary embodiment of the present invention, the second threshold value is below 0.1 m, preferably below 0.05 m, most preferably below 0.02 m.

[0159] Having two thresholds, which together may form a maximum threshold, is advantageous in the control of an automated guided vehicle because it allows the automated guided vehicle to continue operating in various situations that may allow pushing or towing an object.

[0160] Such a situation includes pushing an object (such as a pallet) while moving the forks closer and closer to the correct engagement position. In this case, pushing the pallet by, for example, 10 cm may be permissible, while when the correct engagement position is reached, it may only be permissible to push the pallet by, for example, 2 cm.

[0161] This particular situation can be determined by the controller, for example, based on a comparison of inputs from the primary sensor and the secondary sensor, such as if the direct distance measured by the primary sensor decreases, but not at an expected rate based on the input from the secondary sensor. When the decrease in direct distance deviates from expectations, a timer can be started, and after, for example, 5 seconds of continuous deviation, the controller can stop the movement of the automated guided vehicle.

[0162] Another example of such a situation is breaking through a package wrapped around a pallet. The pallet can be pushed a distance corresponding to a first threshold while trying to penetrate the package. Once penetrated, the pallet can only be pushed a distance corresponding to a second threshold.

[0163] This particular situation can be determined by the controller, for example, based on a comparison of inputs from the primary sensor and the secondary sensor. This situation can be detected if the direct distance measured by the primary sensor does not decrease while the input from the secondary sensor indicates motion. When this happens, a timer can be started, and after, for example, 5 seconds, the direct distance has not decreased, the controller can stop the movement of the automated guided vehicle. When the forks penetrate the package, the direct distance can be as expected again based on the input from the secondary sensor.

[0164] In an exemplary embodiment of the invention, the movement of the automated guided vehicle is stopped if the established distance change is below a direct docking threshold.

[0165] The direct docking threshold may specify the distance between the primary sensor and the object when the automated guided vehicle is in the correct engagement position. The direct docking threshold may be between 0.01 m and 0.3 m, depending on where the primary sensor is located on the automated guided vehicle.

[0166] It should be mentioned that for this particular close-up measurement, alternative sensors (such as laser distance sensors) can be used to provide more accurate distance measurements than the primary sensor can provide.

[0167] In an exemplary embodiment of the present invention, the primary sensor is a lidar sensor.

[0168] The primary sensor is sometimes referred to as a rear sensor because it is located at the rear portion of the automated guided vehicle when the automated guided vehicle is traveling in its normal direction (opposite the forks). A lidar sensor is advantageous because it is fast (e.g., scanning at a frequency of 100 Hz) and the measurements are accurate (e.g., with an accuracy of less than 10 mm).

[0169] In an exemplary embodiment of the present invention, the primary sensor is a scanning LiDAR sensor that scans the area in front of the forks.

[0170] When used to monitor and control an automated guided vehicle in an object handling mode, an object positioned at a target location is within the reach of a scanning area of ​​a scanning lidar sensor.

[0171] In an exemplary embodiment of the invention, the primary sensor is implemented as one or more laser distance sensors.

[0172] One or more rotating or fixed laser range sensors may be used as an alternative to a scanning lidar sensor.

[0173] In an exemplary embodiment of the invention, the secondary sensor is a rotary encoder.

[0174] An advantage of a rotary encoder is that it can convert the angular position or angular motion of a wheel or motor shaft into an analog or digital output signal.A rotary encoder may be an electromechanical device which may also be referred to as an odometer.

[0175] It should be mentioned that the secondary sensor may also be implemented as other types of sensors, such as a camera, a 3D camera, a laser distance sensor, an ultrasonic distance sensor or any other type of known electronic distance sensor that a person skilled in the art may find suitable, all of which may be independent of the object.

[0176] In an exemplary embodiment of the invention, the method further comprises the steps of: monitoring motor data; deriving an expected travel distance based on the motor data; and comparing the established travel distance with an actual measured distance measured by the secondary sensor.

[0177] The controller may have access to a data store where knowledge of, for example, expected power consumption per distance traveled is stored. Based on this information, the controller may therefore estimate the distance traveled based on the power consumption of the motor. If this expected distance traveled does not match the distance measured by / input from the secondary sensor, this indicates that the wheel is slipping and therefore a change in control action is required. Of course, in theory, this way of monitoring and evaluating motor data and measured distances could be done for both / all wheels of an automated guided vehicle.

[0178] It should be noted that in addition to monitoring motor data, other internal data / operating parameters may also be monitored, such as various temperature sensors, encoders, accelerometers, gyroscopes, magnetometers, compasses, GPS, cameras, etc.

[0179] In an exemplary embodiment of the present invention, the method further comprises the step of measuring a first corner distance and a measured second corner distance of the object.

[0180] If the two measured corner distances are the same, it indicates that the automated guided vehicle is approaching / engaging the object in a straight line. If the two measured corner distances are below the corner docking threshold, the controller stops the movement of the automated guided vehicle because it is expected that the forks will be properly engaged / positioned to lift the object.

[0181] In an exemplary embodiment of the present invention, the method further includes the following steps: if one of the measured first corner distance or the measured second corner distance does not change, the movement of the automated guided vehicle is stopped, and the movement of the automated guided vehicle is indicated by the distance measured by at least one of the secondary sensor or the inertial measurement unit.

[0182] The absence of a change in one or both of the corner distances while either the direct distance between the automated guided vehicle and the object decreases or the motion measured by the secondary sensor or inertial measurement unit decreases indicates that the object is being pushed and therefore, it may be advantageous to stop the motion of the automated guided vehicle.

[0183] It should be mentioned that if one or both of the measured corner distances are decreasing, but not decreasing at the same rate as the direct distance decreases or as the distance measured by the secondary sensor or inertial measurement unit increases, the movement of the automated guided vehicle towards the object can continue. This is because it indicates that even though the object, such as a pallet, is being pushed, the forks are still increasing the portion of their engagement with the pallet. In this case, the controller can slightly adjust the direction of movement so that the decrease in the measured corner distance and the direct distance decrease / increase in the measured distance are consistent.

[0184] Note that when referring to "same rate" or "consistent" measurements of, for example, a scanning LiDAR, this is not mathematically correct. This is because the distance from the scanning LiDAR sensor to the corner of an object and the distance from the scanning LiDAR sensor to the object (direct distance) / distance traveled by the wheels are not the same.

[0185] In an exemplary embodiment of the present invention, the method further includes the following steps: if one of the measured first corner distance or the measured second corner distance does not change, reversing the direction of movement of the automated guided vehicle, while indicating the movement of the automated guided vehicle by the distance measured by at least one of the secondary sensors or the inertial measurement unit.

[0186] The controller may abort the docking mode, move the AGM away from the object, and then initiate a new docking mode as described in this document. Such a new docking mode may be initiated in the event that the AGM follows a slightly changed route and / or the height of the forks changes (up or down).

[0187] In an exemplary embodiment of the invention, the method further comprises the step of stopping the movement of the automated guided vehicle if the measured first corner distance and the measured second corner distance do not change at the same rate.

[0188] If the measured corner distance does not change at the same rate / speed, it may indicate that the object is rotating or twisting and therefore halting the movement of the automated guided vehicle.

[0189] In an exemplary embodiment of the invention, the object is a pallet.

[0190] In an exemplary embodiment of the invention, the movement of the automated guided vehicle from the second position to the target position is performed using the fork towards the target position.

[0191] In an exemplary embodiment of the invention, motion control in normal mode is based at least in part on input from a front scanner of the automated guided vehicle.

[0192] Navigation should be understood as controlling the movement of the automated guided vehicle. The movement of the automated guided vehicle in normal operating mode is usually in the opposite direction of the forks, which is why the name of the sensor located at the opposite end of the automated guided vehicle is named the front sensor.

[0193] In an exemplary embodiment of the invention, the method according to claim 14 is implemented in an apparatus according to claim 15 .

[0194] In an exemplary embodiment of the invention, the device according to claim 15 is implementing the method according to any one of claims 1-14.

[0195] Based on the above, it is now clear that the present invention relates to a method for monitoring and controlling an AGV when the AGV is approaching an object to be picked up or to be placed at a target location or is moving away from the object. The AGV is controlled according to a normal control mode before and after the so-called object loading and unloading mode. During the object loading and unloading mode, inputs from two independent sensor types are used to control the AGV. The first sensor type measures the distance between the AGV and the object OB at a sampling frequency. The distance traveled is established based on two of these measurements. The second sensor type measures the distance traveled by the AGV independently of the surrounding environment of the AGV.

[0196] Additionally, during the final portion of the distance toward the object / target location, the motion of the AGV is controlled based on input from the second sensor type, and if necessary, the movement of the AGV is adjusted or stopped based on input from the first sensor type.

[0197] As long as the established distance and the measured distance are substantially the same, the controller CO continues to allow the AGV to move forward. However, if, for example, the second sensor type indicates motion and the first sensor type does not, then an indication of AGV wheel slippage or pushing / dragging of an object may occur and control action may be required.

[0198] Determining wheel slip and dragging / pushing of objects using only existing AGV sensors and based solely on distance measurements that are independent of the surrounding environment is advantageous because time-consuming object handling errors (due to the need for manual remediation) and damage to the objects can be avoided.

[0199] The present invention has been illustrated above with reference to specific examples of methods and robotic systems for purposes of illustration and not limitation. Details such as specific methods and system structures have been provided for the purpose of understanding the embodiments of the present invention. It should be noted that detailed descriptions of well-known systems, devices, circuits, and methods have been omitted so as not to obscure the description of the present invention with unnecessary detail.

[0200] List

[0201] AGV. Automated Guided Vehicle

[0202] FO.Fork

[0203] SI. Support interface

[0204] PS. Primary sensor

[0205] SS. Secondary sensor

[0206] TS.Three-stage sensor

[0207] CO. Controller

[0208] 1PO. First position

[0209] 2PO. Second position

[0210] IP.Middle position

[0211] DR. Second position range

[0212] TP. Target location

[0213] HP. Loading and unloading position

[0214] DD. Direct distance

[0215] DT. Distance traveled

[0216] OB. Object

[0217] PA.Pallets

[0218] LO. Loading

[0219] 1CD. First corner distance

[0220] 2CD. Second corner distance

[0221] IMU. Inertial Measurement Unit

[0222] DAS.Data Storage

[0223] FS.Front sensor

[0224] 1T. First time

[0225] 2P. Second time

[0226] WF.Warehouse floor

[0227] 1COS. First aisle side

[0228] 2COS. Second aisle side

Claims

1. A method for monitoring navigation of an automated guided vehicle (AGV) in an object handling operation mode, the automated guided vehicle (AGV) comprising a fork (FO), a primary sensor (PS), a secondary sensor (SS) and a controller (CO) for controlling the movement of the automated guided vehicle (AGV), the method comprising the following steps: monitoring movement of the automated guided vehicle (AGV) between a first position (1PO) and a second position (2PO) while operating in a normal mode, monitoring movement of the automated guided vehicle (AGV) operating in the object handling mode between the second position (2PO) and a target position (TP), Wherein, the monitoring in the object loading and unloading mode includes: establishing a change in the distance between the automated guided vehicle (AGV) and the object (OB) within a time period between two points in time based on distance measurements obtained by the primary sensor (PS), a distance represented by the distance travelled by the automated guided vehicle (AGV) during the time period measured by the secondary sensor (SS), The established distance change and the measured distance representation are compared, and based on the comparison, it is determined whether a correction of movement of the automated guided vehicle (AGV) is required.

2. The method according to claim 1, wherein: The object handling mode includes a docking operation mode and / or an undocking operation mode.

3. A method according to any one of the preceding claims, wherein: If the comparison results in a difference between the established distance change and the measured representation of distance traveled being greater than a maximum threshold, a correction of the movement of the automated guided vehicle (AGV) is required.

4. A method according to any one of the preceding claims, wherein: Control of the automated guided vehicle (AGV) during the object handling mode is controlled according to first and second thresholds.

5. A method according to any one of the preceding claims, wherein: The established distance variation is established based on a direct distance (DD) measurement performed between the primary sensor (PS) and the object OB.

6. A method according to any one of the preceding claims, wherein: The scanning lidar sensor further measures a first corner distance (1CD) and a second corner distance (2CD) of the object (OB) at the target position (TP).

7. A method according to any one of the preceding claims, wherein: In addition to the primary sensor (PS), the automated guided vehicle (AGV) also comprises a laser distance sensor.

8. A method according to any one of the preceding claims, wherein: The secondary sensor (SS) measures the distance travelled by the wheels of the automated guided vehicle (ARM).

9. A method according to any one of the preceding claims, wherein: The automated guided vehicle (AGV) includes two secondary sensors (SS).

10. A method according to any one of the preceding claims, wherein: The distance traveled by the automated guided vehicle (AGV) is further measured by a tertiary sensor (TS).

11. A method according to any one of the preceding claims, wherein: The method further comprises the step of stopping the automated guided vehicle (AGV) if the direct distance (DD) does not change and the measured distance changes.

12. A method according to any one of the preceding claims, wherein: The method further comprises the step of adjusting one or more control parameters of the automated guided vehicle (AGV) if the direct distance (DD) does not change and the measured distance changes.

13. The method according to any one of claims 1 to 12 and claim 14 is implemented in an apparatus according to claim 15.

14. A method of controlling an automated guided vehicle (AGV) according to any one of the preceding claims in a normal operating mode, the normal operating mode being followed by an object handling mode operation, the object handling mode operation being followed by the normal operating mode, the automated guided vehicle (AGV) comprising a fork (FO), a primary sensor (PS), a front sensor (FS), a secondary sensor (SS), a data storage (DAS) and a controller (CO) for controlling the movement of the automated guided vehicle (AGV), wherein: The method comprises the following steps: controlling movement of the automated guided vehicle (AGV) in the normal operating mode during a first time period, wherein the normal operating mode includes navigating the automated guided vehicle (AGV) based at least on a digital representation of an area in which the automated guided vehicle (AGV) is to move and input from the front sensor (FS), controlling movement of the automated guided vehicle (ARM) in the object handling mode of operation during a second time period shorter than the first time period, wherein the object handling mode of operation includes navigating the automated guided vehicle (AGV) based at least on input from the primary sensor (PS) and input from the secondary sensor (SS), During a third time period longer than the second time period, in the normal operating mode, controlling the movement of the automated guided vehicle (ARM), wherein the normal operating mode includes navigating the automated guided vehicle (AGV) based at least on a digital representation of an area in which the automated guided vehicle (AGV) will move and input from the front sensor.

15. An automated guided vehicle (AGV) comprising a fork (FO), a primary sensor (PS), a secondary sensor (SS) and a controller (CO), the controller controlling the movement of the automated guided vehicle (AGV) in a normal operating mode and in an object handling operating mode according to the method of any of the preceding claims, in, When operating in the object handling mode of operation, The primary sensor (PS) is configured to establish a change in distance between the automated guided vehicles (AGVs) within a time period between two points in time, the secondary sensor (SS) being configured to measure a distance representative of a distance traveled by the automated guided vehicle (AGV) during the time period, The controller (CO) is configured to compare the established distance change with the measured distance and determine whether a correction of the movement of the automated guided vehicle (AGV) is required based on the comparison result, and Wherein, the controller (CO) is configured to control the movement of the automated guided vehicle (AGV) in the object handling operation mode according to the comparison result.

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