Tool-engaging coupling system and related methods

Abstract

There is provided a tool-engaging coupling system configured to engage a tool-engaging coupler with a locator positioned relative to a workpiece at a working position of the tool, the system comprising a robot arm coupled to the tool-engaging coupler and movable in multiple axes relative to the workpiece to position the tool-engaging coupler at the working position via the locator, the robot arm operating in one or more impedance modes, the or each impedance mode configured to produce a different stiffness in one or more of the axes of motion of the tool-engaging coupler.

Description

[Technical Field]

[0001] The present invention relates to a tool engaging coupling system and associated method, and more particularly to a tool engaging coupling system and associated method configured to position a tool at a predetermined working location on a workpiece. [Background technology]

[0002] Vehicle manufacturing traditionally requires skilled operators to work in unergonomic, limited-access areas for long periods of time using a series of different tooling and shop aids to complete drilling tasks. Traditional methods involve a wide range of process variables that are difficult to quantify, such as the operator's skill and concentration level, the placement accuracy of drill tooling (blocks and bushings, drill jigs, etc.), and the maintainability of hand tooling (pneumatic drills, drill bits, torque wrenches, etc.). All of these factors contribute to increased potential for non-conformance reports (NCRs) / quality defects, variability in process completion times, and the cost of air vehicle manufacturing.

[0003] Although various solutions have been proposed, they fail to address the problem, which means that there remains a need to automate at least some of the actions currently provided by the operator. Additionally, there is a need for a precise process that ensures that the tooling is guided to a precise location to perform any operation. Summary of the Invention

[0004] According to an aspect of the present invention, there is provided a tool engaging coupling system configured to engage a tool engaging coupler with a locator positioned relative to a workpiece at a working position of the tool, the system comprising a robot arm coupled to the tool engaging coupler and movable in multiple axes relative to the workpiece to position the tool engaging coupler at the working position via the locator, the robot arm operating in one or more impedance modes, the or each impedance mode configured to produce a different stiffness in one or more of the axes of motion of the tool engaging coupler.

[0005] Preferably, a tool engaging coupling system is provided in which the impedance mode can be selected based on at least one of the task the system is required to undertake and the distance of the tool engaging coupler from the work position.

[0006] Preferably, a tool engaging coupling system is provided wherein the distance comprises a plurality of distance ranges, in each of which the robot arm operates in a predetermined impedance mode.

[0007] Preferably, a tool engagement coupling system is provided wherein the first of the or each predetermined impedance mode comprises a rigid mode, and in the rigid mode the robot arm is movable in one or more axes of motion.

[0008] Preferably, a tool engagement coupling system is provided in which, in the rigid mode, the robot arm is movable in one axis of motion.

[0009] Preferably, a tool engagement coupling system is provided wherein the second of the or each predetermined impedance mode comprises a flexible mode, in which the robot arm is movable in multiple axes of motion.

[0010] Preferably, in the flexible mode, the robot arm is provided with a tool engaging coupling system that is movable in the X and Y axes as well as in yaw, pit, and roll.

[0011] Preferably, a tool engaging coupling system is provided which operates in a continuous predetermined impedance mode.

[0012] Preferably, the impedance mode is determined from the impedance on the tool engaging coupler from the effective weight experienced at the tool engaging coupler.

[0013] Preferably, a tool engaging coupling system is provided in which the effective weight is based on the movement of the arm, the weight applied to the tool engaging coupler by the robot arm, and the associated load supported by the robot arm.

[0014] Preferably, a tool engaging coupling system is provided in which the associated load comprises one or more of a connector between the system and the tool engaging coupler, a tool, and a joint in the arm.

[0015] Preferably, a tool engaging coupling system is provided, the tool engaging coupling system including a tool engaging coupler.

[0016] Preferably, a tool engaging coupling system is provided in which the tool engaging coupler includes an engaging member having a first predetermined shape adapted to engage with a locator having a second predetermined shape.

[0017] Preferably, a tool engaging coupling system is provided, wherein the tool engaging coupler is adapted to be moved by the robot arm based on a level of spatial tolerance that decreases as the tool engaging coupler approaches the locator based at least in part on the first predetermined shape and the second predetermined shape.

[0018] Preferably, a tool engaging coupling system is provided which further comprises a sensor for determining impedance on the tool engaging coupler to enable one or more of the impedance modes.

[0019] Preferably, a tool engaging coupler is provided for use in a tool engaging coupling.

[0020] Preferably, a locator is provided for use in a tool engaging coupling system.

[0021] According to an aspect of the invention, there is provided a method of engaging a tool-engaging coupler with a locator positioned relative to a workpiece at a working position of the tool, the method comprising: moving a robot arm coupled to the tool-engaging coupler in a plurality of axes relative to the workpiece to position the tool-engaging coupler at the working position via the locator; and operating the robot arm in one or more impedance modes, each configured to produce a different stiffness in one or more of the axes of motion of the tool-engaging coupler.

[0022] Preferably, a method is provided which further comprises selecting an impedance mode based on at least one of the task the system is required to undertake and the distance of the tool engagement coupler from the work position.

[0023] Preferably, a method is provided in which an algorithm records the current position and is used to improve the accuracy of indexing between subsequent holes in the locator and / or fixture.

[0024] Preferably, a method is provided wherein a first of the or each predetermined impedance mode comprises a rigid mode, in which the robot arm is movable in one or more axes of motion.

[0025] Preferably, a method is provided wherein in the rigid mode the robot arm is movable in one axis of motion.

[0026] Preferably, a method is provided wherein a second of the or each predetermined impedance mode comprises a flexible mode, in which the robot arm is movable in multiple axes of motion.

[0027] Preferably, a method is provided wherein in the flexible mode the robot arm is movable in the X and Y axes as well as in yaw, pit and roll.

[0028] Preferably, a method is provided wherein the system operates in a continuous predetermined impedance mode.

[0029] Embodiments of the present invention will now be described, by way of example only, with reference to the drawings, in which: [Brief explanation of the drawings]

[0030] [Figure 1] 1 illustrates a block diagram of a multi-function mobile platform in accordance with an aspect of the present invention. [Figure 2] 2 shows a simplified diagram of a tool engagement coupler, locator, and locator fixture for use with the platform of FIG. 1; [Figure 3] FIG. 10 shows a schematic demonstrating engagement between a tool engagement coupler and a locator. [Figure 4] 10 is a flow chart relating to the operation of the tool engaging coupling. DETAILED DESCRIPTION OF THE INVENTION

[0031] System 100 includes a mobile platform (MP) 101, shown in Figure 1, and is technology developed to tackle a wide range of manufacturing tasks either fully autonomously or in collaboration with an operator. One use case for the present invention is the development of a tool engagement coupler (TEC) for use with limited or non-limited access drilling or other tooling.

[0032] Air vehicle manufacturing traditionally requires skilled operators to work in unergonomic, limited-access areas for long periods of time to complete tasks. Traditional methods also involve a wide range of process variables that are difficult to quantify, such as tooling placement accuracy. This often results in defects, variability in process completion times, and increased costs for air vehicle manufacturing. Using autonomous devices such as systems to perform manufacturing tasks presents numerous challenges.

[0033] First, the positioning of the device to perform a task needs to be precise so that the operation to be performed on the component (e.g., drilling) is performed at the required work location (WP). This is particularly important for the manufacture of intricate structures that require precision engineering, such as components for aeronautical applications. The embodiments described herein achieve this precision by providing a tool engagement coupler connected to the mobile platform (MP) and a locator positioned proximate to the work location that engage with each other to guide the tool to the work location.

[0034] Automatic positioning of a device in a work position to perform a task is unlikely to be perfect in every case. Therefore, it is desirable to provide a spatial tolerance (e.g., ±5 mm) for positioning the device when approaching the work position. The embodiments described below achieve this spatial tolerance by configuring a tool engagement coupler and locator to guide the tool into the correct engagement position.

[0035] The system 100 includes a mobile platform (MP) 101, a service unit 108, and a control unit 110. The MP 101 enables the system 100 to automatically move to a work site location. The MP 101 is connected to a robotic arm 104. The robotic arm 104 is connected to a tool unit (TU) 106, which is connected to a tool engagement coupler 102.

[0036] The tool-engaging coupler 102 is connected to a robotic arm 104. The robotic arm 104 is responsible for positioning the tool-engaging coupler 102 near a locator and applying the force required for the tool-engaging coupler 102 to engage with the locator. The robotic arm 104 houses components configured to operate mechanisms housed within the tool-engaging coupler 102, which enable the tool-engaging coupler to engage with the locator. In another embodiment, the components configured to operate the mechanisms housed within the tool-engaging coupler 102 are separate from the robotic arm 104. For example, a robot umbilical connected to the system 100 and the tool-engaging coupler 102 houses components configured to operate the tool-engaging coupler 102. The robotic arm 104 is connected to the system 100, which includes a service unit 108 and a control unit 110. The control unit 110 is pre-programmed to control the positioning and movement of the robotic arm. The components configured to operate the mechanisms housed within the tool-engaging coupler 102 are separate from the robot arm 104. A robot umbilical 112 connected to the system 100 and the tool-engaging coupler 102 houses the components configured to operate the TEC tool-engaging coupler, such as cabling, compressed air, etc.

[0037] The tool-engaging coupler or coupling (TEC) 102 is configured to guide the tool to a working position. This is accomplished by guiding the tool-engaging coupler toward and engaging a locator positioned at a predetermined location relative to the workpiece. The guiding and engagement of the tool-engaging coupler 102 and locator provide precise positioning of the tool on the workpiece when the tool-engaging coupler 102 and locator are engaged. The guiding toward and engagement of the tool-engaging coupler 102 and locator operate within a predetermined spatial tolerance (e.g., ±5 mm displacement from the tool's working position) for initial positioning of the tool-engaging coupler 102 prior to final engagement with the locator.

[0038] As previously explained, the control unit 110 controls the operation and movement of the robot arm 104 to ensure that the tool engagement coupling is accurately positioned relative to the locator workpiece in the working position. As explained above, the locator is at a known, predetermined position relative to the Cartesian axes and in terms of the rotational axes (roll, pitch, and yaw, referred to as A, B, and C). Positioning not only needs to be accurate, but also smooth and consistent. If the movement is jerky and / or unclear, there may be problems with the coupling and worse damage to the workpiece, engagement mechanism, and / or tool being used.

[0039] A robotic arm 104 is connected to the system 100 and includes multiple joints along the length of the arm. The joints allow sections of the robotic arm 104 to rotate, pitch, and yaw relative to one another, which allows six degrees of freedom (6 DOF) of movement of the tool engagement coupler 102. The multiple joints allow the robotic arm 104 to flexibly adopt different shapes, and as a result, the shape of the robotic arm 104 can be adapted to suit the local environment for the working position. The joints include torque sensors that provide feedback to the control unit 110 of the forces acting on the robotic arm 104.

[0040] The TU 106 comprises a tool and a means for driving the tool. The TU 106 comprises an advanced drilling unit (ADU), and the TU 106 is connected to the robot arm via a tool changer configured to connect to different types of TUs. The TU 106 inserts the tool into the tool engagement coupler 102. The service unit 108 is configured to supply the components of the system 100 with substances required for the components to function, such as lubricants and compressed air.

[0041] The present invention seeks to address some of the problems associated with ensuring smooth delivery of a tool engagement coupling to engage a locator without misalignment and potential collision.

[0042] The system 100 includes hardware and software capabilities for task automation. Through programming and processes, the system can be moved to locations required for the task at hand. The system includes motors (not shown) in its body that allow the system to move around factory locations or move within a vehicle. The system autonomously moves to the location of the workpiece where tooling is required. Upon arriving at the location within the factory, the system stops moving and the robotic arm 104 is deployed to be moved toward the locator.

[0043] 2 shows a two-dimensional representation of the tool-engagement coupler 102. As previously described, the tool-engagement coupler 102 is connected to the robot arm 104 via the TU 106. The tool-engagement coupler 102 comprises a first portion 202, a second portion (also referred to herein as a drive portion) 204, and an engagement member 206. A tool 208 provided by the TU 106 is housed by the engagement member 206. A locator 210 of a plurality of locators housed by a locator fixture 212 is positioned below the engagement member 206. The locator fixture 212 is attached to a workpiece 214.

[0044] The first portion 202 is positioned at the proximal end of the tool engagement coupler 102 and forms a connection with the robot arm 104 via the TU 106. The first portion 202 comprises a motor configured to power components in the second portion 204. The motor may comprise a stepper motor that may be accompanied by a controller that provides position feedback to the stepper motor. The controller receives information from a proximity sensor located in the engagement member 206. The motor is controlled by the control unit 110. The motor is operated via control passed through the robot umbilical 112. The connection between the motor portion 202 and the drive portion 204 may comprise a drive shaft or a drive coupling.

[0045] The second portion 204 of the tool engagement coupler 102 comprises components configured to drive an engagement mechanism in the engagement member 206. The engagement mechanism is described in more detail in FIG. 3. The drive portion 204 optionally comprises one or more of a series of gears (e.g., miter gears), a drive belt, and a drive belt tensioner connected to a drive shaft or drive coupling. In some embodiments, a worm drive is used to drive the engagement mechanism in the engagement member 206.

[0046] An engagement member 206 of the tool-engaging coupler 102 is configured to engage a locator in a working position. The engagement member 206 is also configured to accommodate a tool 208. The engagement member 206 has a predetermined shape adapted to engage a locator 210 having a second predetermined shape. The first and second predetermined shapes are described in more detail with reference to FIG. 3 but are not shown in FIG. 2; the engagement member 206 is optionally cylindrical in shape and includes an opening through its center through which the tool 208 can pass, as indicated by the arrow in FIG. 2.

[0047] FIG. 3 shows a schematic two-dimensional side profile view of the engagement member 206 engaged with the locator 210. The locator 210 is secured to a locator fixture 212. The locator 210 is optionally a bushing. The locator 210 is secured to the locator fixture 212 in any suitable manner, including mechanical fastening, adhesive fastening, magnetic fastening, etc. The locator 210 includes a tool opening 350 and an opposing work site opening 352 closest to the work site. Although not shown in FIG. 3 , the tool opening 350 may be circular. To ensure that the TEC 102 can be positioned precisely enough for the locator 210 to receive the engagement member 206, the diameter of the tool opening 350 may be determined by the spatial accuracy of the robot arm 104. For example, the diameter may be equal to or greater than the spatial accuracy of the robot arm. The locator 210 further comprises a lip (also referred to herein as a lipped portion) 356 that extends into the tool opening 350 on the tool opening 350 side of the locator 210 .

[0048] The engagement member 206 and locator 210 work in conjunction to allow the robot arm 104 to position the tool-engagement coupler 102 within predetermined spatial tolerances when positioning the tool-engagement coupler 102 in a working position. FIG. 3 shows the engagement member body 310 having a first predetermined shape with a tapered end 314 that forms a conical shape in three dimensions. The locator 210 is shown having a second predetermined shape with a sloped, “bowl-like” interior structure. As a result, when the tapered end 314 of the engagement member 206 contacts the sloped interior structure of the locator 210 and is moved toward the locator 210, the central opening 312 is moved toward the center of the locator 210 in the working position. Thus, the level of movement or spatial tolerance of the tool-engagement coupler 102 by the robot arm 104 decreases as the engagement member 206 approaches the locator 210 based at least in part on the first predetermined shape of the engagement member body 310 and the second predetermined shape of the locator 210. For example, when the engagement member 206 is positioned above the locator, the movement or spatial tolerance of the tool engagement coupler 102 is determined by the range of motion of the robot arm 104. In contrast, when the engagement member is positioned with the locator, the movement or spatial tolerance of the tool engagement coupler 102 is greater toward the top compared to the bottom of the locator 210.

[0049] The robot arm, and accordingly the tool engagement coupler 102, is more flexible in the x-axis and y-axis compared to the z-axis (shown in FIG. 3 ), which may be set according to a control mode. The increased flexibility may also extend to the pitch, roll, and yaw of the robot arm. The tool engagement coupler 102 can now be moved in the z-axis by the robot arm 104. As a result, the position and configuration of the robot arm 104 (and therefore the position of the tool engagement coupler 102) reacts to the interfacing between the engagement member 206 and the locator 210 while the tool engagement coupler is moved in the z-direction. Once the tool engagement coupler 102 is correctly positioned, the robot arm 104 moves the tool engagement coupler 102 a predetermined amount in the z-axis, thereby engaging the tool engagement coupler 102 and the locator 210 in the final working position.

[0050] When aligned, the engagement member 206 is moved toward the workpiece by the robot arm 104 and the tapered end 314 of the engagement member 206 contacts the edge of the opening in the locator 210, thereby guiding the engagement member 206 toward the center of the locator 210.

[0051] The engaging member 206 and locator 210 also work in conjunction to secure the position of the central opening 312 in the working position. The locator 210 includes a lipped portion 356 around the edge of the tool opening that is configured to receive the locking component 308 of the engaging member 206. As a result, the engaging member 206 is prevented from moving in the locator 210 except in the z-axis. Furthermore, the locking component 308 also prevents the engaging member 206 from moving in the x- and y-axes of the locator 210. The locking component 308 applies a force to the inside of the locator 210, thereby holding the engaging member 206 in place. The engaging member 206 is therefore held in a rigid position when the tool 208 is delivered to the working position through the central opening 312.

[0052] The restricted motion in the different operating modes does not have to be as described above: depending on the use case, the different axes can be rigid or flexible, as will be described in more detail below.

[0053] The extension length 358 of the locking component 308 is preconfigured to a length based on the width of the lipped portion 356 of the locator 210. The extension of the locking component 308 therefore contributes to the accuracy of delivery of the tool 208 to the work location by ensuring the locking component 308 is a predefined distance from the lip 356 of the locator 210. The locking component 308 also ensures a predetermined vertical displacement from the work site by extending the locking component 308 into the angled interior structure of the locator 210 and moving the engaging member 206 in the z-direction away from the work location.

[0054] The engagement of the first predetermined shape of the engagement member 206 with the second predetermined shape of the locator 210 means that precise positioning of the engagement member 206 is not entirely dependent on the control of the control unit 110 of the robot arm 104. The control unit 110 is responsible for positioning the tool engagement coupler 102 within a spatial tolerance of the working position (e.g., ±20 mm), while fine positioning is achieved using the features described with respect to the engagement member 206 and the locator 210.

[0055] Reducing the fine positioning burden on the control unit 110 increases the speed and efficiency of tool delivery to the work site. Additionally, it means that less accurate robotic systems, such as cobots, can be used for precision tooling with the assistance of the tool engagement coupler 102 and locator 210. Considering that the robot arm 104 may be used to move the tool engagement coupler 102 in space-scarce environments, the control unit may have to process numerous parameters related to the configuration of the robot arm 104 (e.g., six degrees of freedom of movement of the joints of the robot arm 104) when making fine adjustments to the position of the tool engagement coupler 102. As explained above, positioning the engagement member 206 and the locator 210 at the work location reduces the processing workload because the fine positioning is achieved automatically due to the first and second predetermined shapes of the engagement member 206 and the locator 210, respectively.

[0056] Due to the configuration of the TEC 102, it can be powered solely using electricity. While typical clamping systems require a compressed air supply to secure the tooling mechanism to the work site, this is not a necessary requirement for the present invention. Without the need for a compressed air supply, the system 100 can be integrated into a mobile platform due to the reduced weight of an electric system compared to a pneumatic or hydraulic system. This allows the system to be programmed to automatically move to a work site while also being able to move into confined spaces or hazardous environments.

[0057] The contribution of the features displayed in the figure can be explained by describing the step-by-step process of delivering a tool to a work site. First, the control unit 110 moves the robot arm 104 into the work area using the arm's six degrees of freedom to avoid any access restrictions to the work location. The robot arm 104 and tool-engaging coupler 102 are moved by the control unit toward the work location where a locator fixture 212 comprising locator(s) 210 is positioned. The control unit 110 then commands the robot arm 104 to apply a force in a direction toward the locators, thereby moving the robot arm in the z-direction as the engagement members 206 approach the locators 210, and simultaneously commands the robot arm 104 to be flexible in one or more axes and rigid in at least one axis, depending on the relative orientation of the tool-engaging coupler 102 and the locators 210. When the tapered end of the engagement member 206 contacts the angled internal structure of the locator 210, the engagement member 206 slides toward the center of the locator 210. Following engagement of the tapered end 314 of the engagement member 206 with the angled internal structure of the locator 210, movement of the TEC 102 becomes more constrained in one or more axes (e.g., the x-axis and y-axis).

[0058] When the engagement member 206 engages the locator 210, the control unit 110 activates a motor in the first portion 202 of the tool engagement coupler 102, which drives a component in the second portion 204 of the tool engagement coupler 102. Activation of the motor is initiated in response to a torque sensor in the robot arm 104 detecting a change in force on the robot arm 104 in response to the engagement member 206 contacting the locator 210. A proximity sensor in or on the engagement member 206 may facilitate activation. This actuates a mechanism in the engagement member 206, causing the locking component 308 to extend radially from the engagement member 206. In the embodiment illustrated in FIG. 3 , the mechanism in the engagement member 206 comprises a rotary worm drive 303. The worm drive 303 contacts and drives the rotation of the worm wheel 304. The worm wheel 304 is connected to one or more locking components 308 via a rotating cam (not shown in FIG. 3) located within the engagement member body 310. As the worm wheel 304 rotates, the locking components 308 are extended radially from the engagement member body 310.

[0059] The locking components 308 extend below a lip 356 on the top edge of the locator 210 and apply a force to the inner wall of the locator 210, thereby locking the engagement members 206 in place and preventing movement of the TEC in the x, y, z, pitch, roll, and yaw axes. In the locked position, the central opening 312 of the engagement members is in the working position. Sensors positioned on or within the engagement members 206, in some cases, track the extension of the locking components 308 to detect when they are positioned below the lip 356. Similar sensors may also detect the rotation of a cam (connecting the worm wheel 304 to one or more locking components 308 and located within the engagement member body 310) to indirectly detect the extension of the locking components 308. During the extension of the locking components 308, the control unit 110 commands the robot arm 104 to operate in one of the control modes (e.g., Cartesian impedance control mode). As a result, the locking component 308 applies a force to the internal structure of the locator 210, causing the engagement member 206 to move to a precise predetermined position in the x, y, and z axes, and configured pitch, yaw, and roll orientations.

[0060] Air vehicle manufacturing traditionally requires skilled operators to work in unergonomic, restricted-access areas for long periods of time using a series of different tooling and shop aids to complete drilling or other manufacturing tasks. Traditional methods also involve a wide range of process variables that are difficult to quantify, such as the operator's skill and concentration level, tool placement accuracy, and the maintainability of any other tooling required for the task. All of these factors contribute to the potential for manufacturing defects, variability in process completion times, and increased costs of air vehicle manufacturing. The present invention seeks to overcome some of these problems.

[0061] The present invention has been developed to tackle a wide range of manufacturing tasks, either fully autonomously or in collaboration with an operator. As previously discussed, system 100 includes a control unit 110 that controls the movement of system 100 and a collaborative robot (not shown) that controls the movement of robot arm 104 (also referred to as a robotic arm). System 100 and the robot have hardware and software capabilities for task automation through unique programming and process methodologies, as discussed below.

[0062] The system 100 is programmed to move around the factory floor or move in a vehicle to move the system to the associated workpiece. Movement from piece to piece or location to location is via motors that drive wheels on the bottom of the system. The system uses simultaneous localization and mapping (SLAM) using laser scanners and wheel encoders to navigate autonomously through the factory. The path for the system is pre-programmed, but the system is capable of autonomously navigating the programmed path to navigate around obstacles as needed.

[0063] Once the system is near the workpiece, it stops moving and the robot is used to move the robot arm into engagement with the required locator at the required working position. The movement of the arm relative to the locator and underlying workpiece should be smooth and consistent. If the movement is jerky or not precisely controlled, the tool engagement coupling may collide with the workpiece and cause damage. The present invention, as explained below, seeks to avoid this.

[0064] As previously described, a robotic arm has multiple joints that can move in different directions or rotations. Each joint has an associated torque sensor capable of measuring twisting or rotational forces about an axis, which can be applied in a clockwise or counterclockwise direction. Torque is a function of force and length. In the case of a robotic arm, movement of each joint about its respective axis contributes to the effective weight of the tool-engaging coupler 102. The effect of each joint remains substantially constant and is known by the system. Movement from pose to pose causes small changes in the effective weight of the arm at the distal end of the tool-engaging coupler 102. However, there are other elements associated with the arm that contribute significantly to the variable effective weight. In this context, this includes the umbilical cord that supplies compressed air and lubricant to the tool-engaging coupler system and any cabling or other connections suspended or supported by the arm. Additionally, if a tool is supported near the tool-engaging coupler during movement, the weight of the tool can also affect the effective weight experienced by the tool-engaging coupler. The effective weight from either source can be determined by the torque sensor.

[0065] Although the weight of each portion of the robot arm is known, its movement from pose to pose causes a change in the effective weight of the arm at the distal end of the tool engaging coupler 102. In the present invention, this change in effective weight is compensated for to ensure accurate positioning of the tool engaging coupling in the locator. This is facilitated by a three-step guide and calculation method as described with reference to Figures 4A-4C. It will be recognized that there may be more or fewer steps depending on the process being performed.

[0066] The first stage shown in FIG. 4A is rigid Cartesian impedance mode 1. The second stage shown in FIG. 4B is flexible Cartesian impedance mode 2. The third stage shown in FIG. 4C is a more rigid Cartesian impedance mode 1. Cartesian impedance control modes are associated with the task / interfacing the robot is required to perform. Different Cartesian control modes are used depending on how the solution is required to interact with the world. In this example, two different Cartesian control modes (rigid and flexible) are initiated at different distances and parts of the process depending on the flexibility required for the system. Rigid Cartesian impedance control mode 1 is used to approach the workpiece for accuracy purposes, flexible Cartesian impedance control mode 2 is used for workpiece interaction to allow flexibility for precise location and normalization, and the more rigid Cartesian impedance control mode is then used for drilling or other tooling activities.

[0067] The different steps may be performed sequentially, in the order in which they occur as described, or in any other suitable order.

[0068] Impedance is a measure of how much a body resists motion and is the ratio of the force applied to the body to the speed at which the body moves. By changing the impedance of a body, the body can be made more rigid or flexible. In the present invention, multiple impedance modes can be used to create different stiffness in different axes of motion. Two such modes are mentioned above and further explained below. In this context, rigid means that the robot arm cannot be moved by influences and moments external to the robot arm, but is controlled only by control or programmed movement in certain axes. Flexible in this context means that the robot arm can be programmed to be influenced, moved, or pushed around by external influences to bring the robot arm into a desired position or pose. In some situations, the robot arm can be flexible in X, Y, A, B, and C and guided by a combination of programmed robot arm control and external influences including tapered locators, associated shapes of engaging members, effective weight, etc.

[0069] 4A, the robot arm autonomously moves to a work position (400). The robot guides the tool engagement coupler 102 to a fixture park position (step 402) a known, activity-dependent distance from the work position or locator fixture engagement point. The example park position is variable depending on the job, but the 30 mm position is one of many examples.

[0070] Measurements from the torque sensors on each robot joint are used to on-the-fly recalculate and calibrate the effective weight of the tool engaging coupler 102 and different portions of the robot arm that apply torque to the distal end of the tool engaging coupler 102 (step 404). This is to compensate for any changes in effective weight in the tool engaging coupler 102 and robot arm due to movement and external influences from cables, umbilical cords, or anything supported by the arm. The calculation is performed by JavaScript code or any other suitable mechanism. In step 406, the tool engaging coupler 102 is moved to within approximately 10 mm of the locator based at least in part on the compensated effective weight.

[0071] Code is used to generate torque sensor data for each joint, allowing recalculation of the end-of-arm tooling weight on the fly to compensate for weight changes caused by changes in robot pose and umbilical / cable management lengths.

[0072] Automated end-effector weight calculation and calibration will now be described in more detail. Before entering flexible mode, the algorithm uses the end-effector's programmed center of gravity and live joint torque data to calculate and update the end-effector's programmed weight. The algorithm and system address this action by adding and subtracting weight from the end-effector's programmed weight, using torque sensors on each joint as scales to perfectly balance the programmed end-effector weight.

[0073] The process then moves to Flexible Mode 2, as shown in FIG. 4B. In step 408, the system transitions to a specialized programmed Flexible Cartesian Impedance Control Mode 2, which allows the robot arm to be flexible in X and Y, but rigid in Z. This allows the tool center point of the tool-engaging coupler and locator 210 to be misaligned from the center of the locator by up to ±5 mm. In step 410, the robot (e.g., a collaborative robot) drives the tool-engaging coupler 102 into the locator 210 mounted on the locator fixture 212 in Flexible Cartesian Impedance Control Mode. In step 412, the tool-engaging coupler 102 engages the correct locator 210, where the distal end of the tool-engaging coupler 102 is not movable relative to the locator, thereby clamping the tool-engaging coupler 102 to the locator.

[0074] In step 413, once the system is clamped and the end effector is in the correct position, a frame get command is used to teach the current position and increase the accuracy of finding the next locator.

[0075] As mentioned above, clamping is promoted and facilitated by specialized bushings, also called locators, and the tapered end of the tool engagement coupler 102, also called the distal end, which, as they move into engagement, seamlessly guide the distal end into working position on the workpiece.

[0076] Once the end effector is clamped and normalized, the robot returns to rigid Cartesian impedance control mode 1, as shown at 414 in FIG. 4C. The required tool is deployed through the central opening that passes through the tool-engaging coupler 102 and locator to engage the workpiece at the working location. Once the manufacturing process (e.g., drilling) is complete, the tool is removed from the central opening and the tool-engaging coupler 102 is ready to be decoupled from the locator. The tool-engaging coupler 102 is then moved to the next locator or to a safe position (step 416).

[0077] From the above, the system can be configured to operate in a "rigid" mode and a "flexible" mode. There can be different modes that use rotary axes, combinations of rotary axes, Cartesian axes, and combinations thereof. The flexible Cartesian impedance control mode allows a less accurate robotic system to be used for precise, high tolerance manufacturing processes.

[0078] Each mode is based on the required allowable degree of movement of the distal end of the tool engagement coupler 102 relative to the locator in each axis. It will be appreciated that one or more axes may be configured to have the same or different allowable degrees of movement from one another.

[0079] The system, in this case, operates in a rigid mode and a flexible mode. It will be understood that the number and type of modes can vary depending on many variables. These include, but are not limited to, the number and type of axes, the size and shape of the workpiece or work location, the size and shape of the system or any other components thereof, the orientation of the workpiece relative to the system, the nature of the tooling, and any other related conditions needed to accommodate the tooling required at the work location. The system will operate from any type of robot and any type of manufacturing situation.

[0080] The allowable distances in each axis are predefined for different modes and are further based on relevant situational variables and the effective weight of the tool engaging coupler 102 .

[0081] Accurate location of the tool-engaging coupler 102 in the working position is achieved based on at least one or more of the different modes, the shape of the distal end and locator of the tool-engaging coupler 102, and correct calibration based on the effective weight of the tool-engaging coupler 102. Additionally, the pose of the robot may add further effects.

[0082] The above describes several different aspects and examples of the present invention. It will be appreciated that alternatives to the described features may fall within the scope of the claims.

Claims

1. 1. A tool engaging coupling system configured to engage a tool engaging coupler with a locator positioned relative to a workpiece at a working position of the tool, the system comprising: a robot arm coupled to the tool engaging coupler and movable in multiple axes relative to the workpiece to position the tool engaging coupler at the work position via the locator; 10. A tool engaging coupling system, wherein the robot arm is configured to operate in one or more impedance modes, the or each impedance mode producing a different stiffness in one or more of the axes of motion of the tool engaging coupler.

2. 2. The tool engaging coupling system of claim 1, wherein the impedance mode is selected based on at least one of a task the system is required to undertake and a distance of the tool engaging coupler from the work position.

3. The tool engaging coupling system of claim 2 , wherein the distance comprises a plurality of distance ranges, and in each of the distance ranges, the robot arm operates in a predetermined impedance mode.

4. 4. The tool engaging coupling system of claim 3, wherein a first of the or each predetermined impedance mode comprises a rigid mode, in which the robot arm is movable in one or more axes of motion.

5. The tool engaging coupling system of claim 4 , wherein in the rigid mode, the robotic arm is movable in one axis of motion.

6. 6. A tool engaging coupling system according to any one of claims 3 to 5, wherein a second of the or each predetermined impedance mode comprises a flexible mode, in which the robot arm is movable in multiple axes of motion.

7. The tool engaging coupling system of claim 6 , wherein in the flexible mode, the robotic arm is movable in the X and Y axes and in yaw, pit, and roll.

8. A tool engaging coupling system according to any one of claims 3 to 7, wherein the system operates in a continuous predetermined impedance mode.

9. A tool engaging coupling system according to any preceding claim, wherein the impedance mode is determined from the impedance on the tool engaging coupler from a significant weight experienced at the tool engaging coupler.

10. 10. The tool engaging coupling system of claim 9, wherein the effective weight is based on movement of the arm, weight applied to the tool engaging coupler by the robotic arm, and associated loads supported by the robotic arm.

11. The tool engaging coupling system of claim 10 , wherein the associated load comprises one or more of a connector between the system and the tool engaging coupler, the tool, and a joint of the arm.

12. The tool engaging coupling system of any preceding claim, wherein the tool engaging coupling system includes a tool engaging coupler.

13. The tool engaging coupling system of claim 12 , wherein the tool engaging coupler includes an engaging member having a first predetermined shape adapted to engage with the locator having a second predetermined shape.

14. 14. The tool engaging coupling system of claim 13, wherein the tool engaging coupler is adapted to be moved by the robot arm based on a decreasing level of spatial tolerance as the tool engaging coupler approaches the locator based at least in part on the first predetermined shape and the second predetermined shape.

15. 15. A tool engaging coupling system according to any preceding claim, further comprising a sensor for determining impedance on the tool engaging coupler to enable one or more of the impedance modes.

16. A tool engaging coupler for use in a tool engaging coupling system according to any preceding claim.

17. A locator for use in a tool engaging coupling system according to any preceding claim.

18. 1. A method for engaging a tool engaging coupler with a locator positioned relative to a workpiece in a working position of a tool, the method comprising: moving a robot arm coupled to the tool engaging coupler in multiple axes relative to the workpiece to position the tool engaging coupler at the work position via the locator; operating the robotic arm in one or more impedance modes; wherein each of the impedance modes is configured to produce a different stiffness in one or more axes of motion of the tool engagement coupler.

19. 20. The method of claim 18, further comprising selecting the impedance mode based on at least one of a task the system is required to undertake and a distance of the tool engaging coupler from the work position.

20. 20. The method of claim 18 or 19, wherein an algorithm is used to record the current position and improve the accuracy of indexing between subsequent holes in the locator and / or fixture.

21. 21. The method of any one of claims 18 to 20, wherein a first of the or each predetermined impedance mode comprises a rigid mode, and in the rigid mode the robot arm is movable in one or more axes of motion.

22. 22. The method of claim 21, wherein in the rigid mode, the robotic arm is movable in one axis of motion.

23. 23. The method of any one of claims 20 to 22, wherein a second of the or each predetermined impedance mode comprises a flexible mode, in which the robotic arm is movable in multiple axes of motion.

24. 24. The method of claim 23, wherein in the flexible mode, the robotic arm is movable in the X and Y axes and in yaw, pit, and roll.

25. A method according to any one of claims 19 to 24, wherein the system operates in a continuous predetermined impedance mode.

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