Robotic end effector system and method with lockable compliance

Abstract

A robotic system and method are provided with an end effector having lockable compliance. The robotic system for manipulating a workpiece includes: an arm having a pair of segments connected by a joint assembly, in which a locking element is disposed. A gripper is connected to the arm and configured to alternately grip and release the workpiece. A controller operates the locking element to alternately lock and unlock the joint assembly. The gripper holds the workpiece during deformation of the workpiece, while the controller can unlock the locking element to allow movement of the joint assembly to release forces generated on the arm during deformation of the workpiece.

Description

Technical Field

[0001] This disclosure generally relates to automated forming and assembly, and more particularly to robotic systems and methods with end effectors including lockable arms with optional compliance to allow deformation of the gripped article. Background Technology

[0002] Performing certain forming and assembly operations efficiently is challenging. For components such as sheet metal panels, forming can be performed using expensive, specific geometric tools (such as dies mounted in a press) and complex transfer tooling for moving parts between operations. In cases requiring high-volume panel production, relatively expensive presses and dies with long development cycles can be used. However, this operation can be costly when low-volume production is involved.

[0003] Robots are becoming increasingly common, including in assembly operations that are difficult to perform manually. Vehicle assembly plants already use robots for spot welding and painting. These applications utilize relatively simple end effectors, such as paint sprayers and spot welders. Each manufacturing application can use its own type of end effector. Forming operations using robotic systems and end effectors are challenging because the items being formed are gripped and released by the robot while changing their dimensions during forming. This requires repeatedly engaging the items with some form of gripper.

[0004] Therefore, it is desirable to provide robotic systems and methods that can efficiently, accurately, and repeatably perform forming and / or assembly operations involving dimensional changes of the articles being processed. Furthermore, it is desirable to flexibly apply these systems to a variety of operations. In addition, other desirable features and characteristics of the invention will become apparent from the following detailed description and appended claims, taken in conjunction with the accompanying drawings and the foregoing technical and background information. Summary of the Invention

[0005] A robotic system and method are provided with an end effector having lockable compliance. A robotic system for manipulating a workpiece includes: an arm having a pair of segments connected by a joint assembly, in which a locking member is disposed. A gripper is connected to the arm and configured to alternately grip and release the workpiece. A controller operates the locking member to alternately lock and unlock the joint assembly. The gripper holds the workpiece during deformation of the workpiece, while the controller can unlock the locking member to allow movement of the joint assembly to release forces generated on the arm during deformation of the workpiece.

[0006] In an additional embodiment, the joint assembly includes a force sensor configured to provide a force signal to the controller, wherein the controller is configured to unlock the joint when the force signal exceeds a threshold force.

[0007] In an additional embodiment, the controller is configured to unlock the lock while the gripper holds the workpiece.

[0008] In an additional embodiment, the vision system is configured to provide the controller with a signal indicating deformation of the workpiece, wherein the controller is configured to unlock the joint when the signal indicates deformation exceeding a threshold.

[0009] In an additional embodiment, the first segment includes an elongated body having a first end, a second end, and a side extending from the first end to the second end. The first end is connected to the joint assembly, wherein the clamp is connected to the side of the body.

[0010] In an additional embodiment, the arm is a first arm, and the robotic system includes a second arm comprising a second locking element configured to alternately lock and unlock the second arm. The second arm includes a second gripper configured to alternately grip and release the workpiece. The controller is configured to alternately lock and unlock the second locking element.

[0011] In an additional embodiment, the joint assembly includes a force sensor configured to provide a force signal to the controller. The controller: records a baseline force on the arm based on the force signal received prior to deformation of the workpiece; receives a measured force from the force sensor after initiating the deformation; compares the measured force with a threshold force; and unlocks the joint when the measured force exceeds the threshold force.

[0012] In an additional embodiment, the gripper includes a suction cup. A pneumatic system is connected to the suction cup and to the controller. The controller is configured to control the pneumatic system to maintain the connection between the suction cup and the workpiece during the deformation.

[0013] In an additional embodiment, the joint assembly includes a ball and a ball joint, wherein the locking member includes a band surrounding the ball, the band being configured to compress the ball in response to the controller to lock the joint.

[0014] In an additional embodiment, the gripper is a first gripper disposed on the first segment. A second gripper is disposed on the second segment. The first gripper and the second gripper are configured to simultaneously grip the workpiece.

[0015] In some other embodiments, a method for manipulating a workpiece includes: constructing an arm having a first segment and a second segment connected to the first segment via a joint assembly. A locking element is provided in the joint assembly, and a gripper is connected to the arm. The workpiece is alternately gripped and released by the gripper. A controller operates the locking element to alternately lock and unlock the joint. The gripper holds the workpiece during deformation of the workpiece while the controller unlocks the joint to allow movement of the joint assembly, thereby releasing forces generated on the arm during deformation of the workpiece.

[0016] In an additional embodiment, a force sensor at the joint assembly provides a force signal to the controller. When the force signal exceeds a threshold force, the controller unlocks the joint.

[0017] In an additional embodiment, the controller unlocks the lock while the clamp holds the workpiece.

[0018] In an additional embodiment, the vision system provides the controller with a signal indicating deformation of the workpiece. When the signal exceeds a threshold deformation, the controller unlocks the joint.

[0019] In an additional embodiment, the first segment is formed of an elongated body having a first end, a second end, and a side extending from the first end to the second end. The first end is connected to the joint assembly, and the clamp is connected to the side of the body.

[0020] In an additional embodiment, the second arm includes a second locking member configured to alternately lock and unlock the second arm. A second gripper is configured to alternately grip and release the workpiece. The controller alternately locks and unlocks the second locking member.

[0021] In an additional embodiment, a force sensor is disposed at the joint assembly to provide a force signal to the controller. The controller records a baseline force on the arm received from the force sensor before deformation of the workpiece. The controller receives a measured force from the force sensor after initiating the deformation. The controller compares the measured force to a threshold force. When the measured force exceeds the threshold force, the controller unlocks the joint.

[0022] In an additional embodiment, the gripper is a suction cup. A pneumatic system is connected to the suction cup and to the controller. The controller controls the pneumatic system to maintain the connection between the suction cup and the workpiece during the deformation.

[0023] In an additional embodiment, the clamp is connected to the first segment, and the second clamp is connected to the second segment. The workpiece is simultaneously clamped by both clamps.

[0024] In some additional embodiments, a robotic system for manipulating a workpiece includes an end effector with a fixing device. A first arm is connected to the fixing device and has a first segment and a second segment connected to the first segment via a first joint assembly, in which a first locking member is disposed. A second arm is connected to the fixing device and has a third segment and a fourth segment connected to the third segment via a second joint assembly, in which a second locking member is disposed. A first gripper is included on the first arm and configured to alternately grip and release the workpiece. A second gripper is included on the second arm and configured to alternately grip and release the workpiece. A controller is configured to: control the first locking member to alternately lock and unlock the first joint assembly; control the second locking member to alternately lock and unlock the second joint assembly; control the first gripper and the second gripper to hold the workpiece during deformation of the workpiece; and unlock at least one of the first locking member and the second locking member to allow movement of the joint assembly to release forces generated on at least one of the first arm and the second arm during deformation of the workpiece. Attached Figure Description

[0025] Exemplary embodiments will be described below in conjunction with the following figures, wherein the same numerals denote the same elements, and wherein:

[0026] Figure 1 These are schematic perspective views of robot systems according to various embodiments;

[0027] Figure 2 According to various embodiments Figure 1 A schematic diagram of a portion of a compliant tooling for a robotic system, the compliant tooling having a pneumatic end gripper;

[0028] Figure 3 According to various embodiments Figure 1 A schematic diagram of a portion of a compliant tooling for a robotic system, the compliant tooling having a mechanical gripper;

[0029] Figure 4 According to various embodiments Figure 1 A schematic diagram of a portion of a compliant tooling for a robotic system, the compliant tooling having multiple pneumatic side grippers;

[0030] Figure 5 It is compatible with various embodiments Figure 1A schematic diagram of a portion of a compliant tooling used in a robotic system, which clamps a sheet being formed;

[0031] Figure 6 According to various embodiments Figure 1 A schematic diagram of a portion of a compliant tooling of a robotic system, which clamps and positions a sheet material to be formed.

[0032] Figure 7 According to various embodiments Figure 1 A schematic diagram of a portion of the compliant tooling of a robotic system, which clamps a sheet being formed;

[0033] Figure 8 It is compatible with various embodiments Figure 1 A schematic diagram of a portion of a compliant tooling used in a robotic system, which clamps a sheet material while allowing stress relief; and

[0034] Figure 9 This is based on the use of various embodiments. Figure 1 The flowchart of the process of the robot system. Detailed Implementation

[0035] The following detailed description is exemplary in nature only and is not intended to limit application and use. Furthermore, it is not intended to be bound by any express or implied theory set forth in the foregoing technical fields, background art, summary of the invention, or the following detailed description. As used herein, the term "module" refers to any hardware, software, firmware, electronic control components, processing logic, and / or processor device, individually or in any combination, including but not limited to: application-specific integrated circuits (ASICs), electronic circuits, processors (shared, dedicated, or grouped) and memories executing one or more software or firmware programs, combinational logic circuits, and / or other suitable components providing the described functionality.

[0036] Embodiments of this disclosure are described herein according to functional and / or logical block components and various processing steps. It should be understood that such block components can be implemented by any number of hardware, software, and / or firmware components configured to perform specified functions. For example, embodiments of this disclosure may employ various integrated circuit components, such as memory elements, digital signal processing elements, logic elements, lookup tables, etc., which can perform various functions under the control of one or more microprocessors or other control devices. Furthermore, those skilled in the art will understand that embodiments of this disclosure can be practiced in conjunction with any number of steering systems, and the vehicle system described herein is merely one example embodiment of this disclosure.

[0037] For the sake of brevity, conventional techniques related to signal processing, data transmission, signaling, control, and other functional aspects of the system (and its various operating components) will not be described in detail herein. Furthermore, the connecting lines shown in the various figures included herein are intended to represent example functional relationships and / or physical connections between various elements. It should be noted that many alternative or additional functional relationships or physical connections may exist in the embodiments of this disclosure.

[0038] In some embodiments, the robotic system flexibly manipulates a workpiece and maintains gripping the workpiece while its geometry undergoes changes. The workpiece can be any processed product that undergoes or is permitted to undergo geometric changes. For example, a workpiece may be gripped during a forming operation in any manufacturing process. In other examples, a workpiece may be gripped upon stress relief (such as when springback occurs and the workpiece moves to its unconstrained state). Gripping a workpiece refers to holding it with any engagement mechanism as a gripper via an end-effector of the robotic system. While the embodiments described herein may be applicable to certain manufacturing applications (such as sheet forming), the present disclosure is not limited to any particular type of workpiece or manufacturing process, but is broadly applicable to situations where it is desirable to be able to manipulate workpieces undergoing geometric changes.

[0039] As described herein, robotic systems can be used to automate processes in which a robot holds a workpiece, and the workpiece undergoes incremental deformation, such as during manufacturing machining. If the robot's gripping of the part is rigid and lacks compliance, deformation is limited. Conversely, as disclosed herein, the arm of a robotic end effector has one or more rigid links with flexible joints that can be controllably alternated between a locked state with no movement and an unlocked state with free movement. The locking and unlocking of the flexible joints can be automatically controlled in a set of joints or individual joints. During the forming process, the joint locking mechanism is controlled to position the arm to securely hold the workpiece when needed, while flexibly adapting to changes in the position and / or orientation of the gripping points on the sheet while the sheet is still held. The joints can be unlocked to relax and prevent the arm from applying unwanted forces to the workpiece. For example, a lockable arm can be unlocked to allow rapid springback of the workpiece without releasing it.

[0040] Reference Figure 1The diagram illustrates a robotic system 20, which generally includes a robot 22 with an end effector 24 and a workpiece 26 being processed by a manufacturing machine 28. The robot 22 may be autonomous or a collaborative robot designed to work alongside humans in a manufacturing environment. Generally, the robot 22 includes several structural elements linked together and movable (including a robotic arm 30), and includes a control system 32 (with actuators and sensors for use in moving the robotic arm 30 in three-dimensional space). Generally, the end effector 24 includes a pair of arms 34, 36 connected to the end portion 38 of the robotic arm 30 via a fixing device 40. The end effector 24 is also coupled to the control system 32, and to actuators and sensors for manipulating the workpiece 26. As shown, a three-dimensional vision system 44 is included for monitoring the workpiece 26 (e.g., for scanning the curvature / deflection of the workpiece 26, which can be used when manipulating the end effector 24). The end effector 24 is also coupled to a pneumatic system 42 for manipulating the arms 34, 36. The pneumatic system 42 may also be coupled to the control system 32. Although a pneumatic actuator is used for the end effector 24 in the current embodiment, other types of actuators, such as electric actuators or other actuators, may be used in other embodiments.

[0041] As shown in the figure, applications of manufacturing machine 28 include, for example, forming sheets representing workpiece 26 when creating vehicle panels. Forming can be performed using the British wheels 46 of rotary equipment 48. The advantage of rotary equipment is that it allows for the flexible production of different panels using the same rotary equipment 48 with wheels 46 of different geometries during the forming process that processes the surface of workpiece 26 to induce plastic deformation. Rotary equipment can be used efficiently for producing small quantities of composite curved panels at relatively low output. Robotic system 20 is suitable for other types of manufacturing operations, such as bending, shearing, drawing, stretching, punching, etc.

[0042] The control system 32 includes a controller 50 (which may include a processor 52, a memory device 54), and may include or be coupled to a storage device 56. While one controller 50 is shown coupled to the robot 22, the end effector 24, the pneumatic system 42, the vision system 44, and the manufacturing machine 28, any number of controllers can be used to coordinate operations to perform various functions. Therefore, although the components of the control system 32 are depicted as part of the same system, it is understood that in some embodiments, these features may include multiple systems, and any number of individual controllers may be employed. The controller 50 can execute instructions that, when executed by the processor 52, support receiving and processing signals such as those from various sensors, and executing logic, calculations, methods, and / or algorithms for the automated control of the components and systems described herein, such as the various actuators of the robot system 20. During operation, the processor 52 can execute one or more programs and can use data, each of which can be retrieved from the storage device 56, thus enabling the processor 52 to perform the processes described herein (such as those described below). Figure 9 In the process described further, the general operation of the control controller 50 is controlled. The memory device 54 can store the above-described program along with one or more stored values ​​of data, such as for short-term data access. The storage device 56 stores data, such as for long-term data access, for use in the automated control robot system 20.

[0043] Reference Figure 2 It shows what can be used as Figure 1 An embodiment of arm 60, or one of arms 34, 36, or used therein, has a gripper 62 at its distal end 64. The distal end 64 is the end of arm 34, 36 furthest from the fixing device 40. Arm 60 comprises three arm segments 70, 72, 74 connected by two joints 76, 78. Thus, arm segments 70, 72, 74 can be described as rigid links comprising arms 34, 36 linked together at hinged joints 76, 78. In embodiments, arms 34, 36 can consist of any number of segments, determined by the coverage and flexibility required for application. Arm segment 70 includes a rigid body 80, which in the present embodiment is cylindrical and tubular, and has a built-in rigid connecting insert 82 for engagement with arm segment 72. Connecting insert 82 includes a disc-shaped insert with a threaded hole 84 at its end facing arm segment 72. The arm segment 70 also includes a gripper 62, which in this embodiment is a suction cup. A connector 86 is disposed inside the main body 80 for connecting the suction cup / gripper 62 to an external pneumatic line 87, which can be configured to extend to... Figure 1The pneumatic system 42. Therefore, the arm 60 is configured to clamp the workpiece 26 by suction / vacuum and to release the workpiece 26 when the vacuum is stopped.

[0044] Arm segments 72 and 74 are substantially identical and include corresponding bodies 88 and 90, which are rigid and tubular, having corresponding connecting inserts 92 and 94 (the connecting inserts 92 and 94 are built-in rigid and have threaded holes 96 and 98), and corresponding joint assemblies 100 and 102. Joint assemblies 100 and 102 include ball sockets 104 and 106, configured as rigid disc-shaped inserts with openings 108 and 110, which are hemispherical and contain corresponding locking bands 112 and 114, which are exposed without being cut open in the current view. Openings 108 and 110 contain corresponding balls 116 and 118 disposed within the locking bands 112 and 114 in a capturing manner. Balls 116 and 118 are rigidly connected to corresponding shafts 120 and 122. Shaft 120 is inserted into hole 84 connecting arm segments 70 and 72, and has space 124 between bodies 80 and 88, allowing bodies 80 and 88 to pivot relative to each other at various angles and in various directions, thereby allowing joint assemblies 100 and 102 to move with multiple degrees of freedom. Similarly, shaft 122 is inserted into threaded hole 96 connecting arm segments 74 and 72, and has space 126 between bodies 88 and 90, allowing bodies 88 and 90 to pivot relative to each other. As shown, joints 76 and 78 are bent to a certain degree, and arm 60 has a length 130. Applying a larger amount of bending to one or both of joints 76 and 78 shortens the length 130, while applying a smaller amount of bending to one or both of joints 76 and 78 increases the length 130. Through this mechanism, arm 60, and therefore arms 34 and 36, are able to compensate for the movement of their clamping points on workpiece 26 when their joints 76 and 78 are unlocked.

[0045] Compensation of the clamping point is achieved by selectively locking and unlocking joints 76 and 78 while the gripper 62 continues to hold the workpiece 26. In the current embodiment, the joint assembly 100 includes a locking band 112, which can be configured as an inflatable bladder structure and is connected to the pneumatic system 42 via a pneumatic line 132. The locking band 112 locks the joint 76 by selectively compressing the ball 116. When this compressing force is applied due to pneumatic pressure, it locks and prevents movement of the ball 116 in the ball socket 104 and prevents bending of the joint 76. When this force / pneumatic pressure is released, the joint 76 is allowed to bend freely by overcoming the very small friction of the ball 116 in the ball socket 104, allowing the ball 116 to pivot. In other embodiments, the locking band 112 may be configured with a lever mechanism (not shown) that can be operated using pneumatic pressure and / or vacuum, wherein pivoting of the lever mechanism alternately compresses and releases forces on the ball 116 by respectively decreasing or increasing the diameter of the locking band 112. In other embodiments, other types of locking mechanisms may be employed. For example, an electrically driven actuator (not shown), such as utilizing a motor and gear set, may be used to selectively increase and decrease the diameter of the locking band 112. In embodiments, the pressure / force applied to the ball 116 by the pneumatic system 42 / other mechanism can be varied to allow the joint 76 to bend under a customizable amount of force.

[0046] Similarly, joint assembly 102 includes a locking band 114, which can be configured as an inflatable bladder structure or as a lever-driven friction band structure and is connected to pneumatic system 42 via pneumatic line 134. The locking band 114 locks joint 78 by selectively compressing ball bearings 118. When this compressing force is applied due to variations in applied pneumatic pressure, it prevents movement of ball bearings 118 within ball sockets 106 and prevents bending of joint 78. When this force is released, joint 78 is allowed to bend freely by overcoming very small frictional forces on ball bearings 118 within ball sockets 106, allowing ball bearings 118 to pivot / rotate therein. In other embodiments, the locking band 114 may be configured with a lever mechanism (not shown) that can be operated using pneumatic pressure and / or vacuum, wherein pivoting of the lever mechanism alternately compresses and releases forces on ball bearings 118 by respectively decreasing or increasing the diameter of the locking band 114. In other embodiments, other types of locking mechanisms may be employed. For example, an electrically driven actuator (not shown), such as utilizing a motor and gear set, may be used to selectively increase and decrease the diameter of the locking band 114. In embodiments, the pressure / force applied to the ball 118 by the pneumatic system 42 / other mechanism may be varied to allow the joint 78 to bend under a customizable amount of force. In other embodiments, other types of joints 76, 78 may be employed. For example, any lockable articulated joint may be used, such as a translational / sliding joint, an orthogonal joint, a rotary joint, a torsion joint, a slewing joint, or a combination thereof.

[0047] Control of joints 76 and 78 can be accomplished according to pre-programmed algorithms and / or with the assistance of real-time input. For example, in this embodiment, joints 76 and 78 include force sensors configured as load cells 146 and 148. Load cells 146 and 148 are respectively disposed on shafts 120 and 122. Shafts 120 and 122 may be minimally elastic, and load cells 146 and 148 may be configured, for example, by means of strain gauges, to sense stress / force in shafts 120 and 122. Thus, when workpiece 26 applies a load to arms 34 and 36, load cells 146 and 148 provide signals indicating the load to controller 50, for example, via conductors 147 and 149. Knowing the load at each joint 76, 78, etc., allows for individual control of joints 76, 78, etc., thereby enabling deductive determination of at which joint 76, 78, etc., the locked state is changed. For example, one or more joints can be unlocked, or one or more joints can be unlocked to different degrees, to control the bending of joints 76, 78, etc., in response to the specific current state and existing forces of workpiece 26.

[0048] Reference Figure 3An alternative embodiment of the gripper 62 is shown. In this case, the gripper 62 is configured to selectively open and close (as shown) to hold or release the robotic hand-like clamp of the workpiece 26. The gripper 62 may include an electrically operated actuator 140 coupled to a controller 50 via a conductor 141. The controller can be operated to move the jaws 142, 144 via the actuator 140 and any number of pivotable links. In other embodiments, any number of jaws may be used. In other embodiments, other forms of grippers may be used, such as electromagnets, expansion mandrels, threaded shafts, articulated fingers, or others.

[0049] exist Figure 4 Another embodiment of an arm portion 150 is shown, which has a plurality of grippers 62. In this embodiment, each of the joint segments 152, 154, 156 includes a gripper 62, and this embodiment corresponds to Figure 1 The end effector 24. Each gripper 62 is configured as a suction cup and is connected to the pneumatic system 42 via corresponding conduits 160, 162, 164. Conduits 160, 162, 164 extend through corresponding bodies 80, 88, 90 to the corresponding gripper 62. For example, the gripper 62 on body 80 is disposed on the side 168 of tubular body 80 between the distal end 64 and the end 166 containing the connecting insert 82. The grippers 62 on bodies 88, 90 are similarly disposed such that arm portion 150 can engage with workpiece 26 in three places, which effectively accommodates gripping larger and / or heavier workpieces 26.

[0050] In reference Figure 5 The steps in processing workpiece 26 are shown. It includes four arms 171-174, each with a gripper 62 at its distal end. Therefore, each arm 171-174 is configured with… Figure 2 The arm section 60. It should be understood that each arm 171-174 can be connected to a common structure (such as the fixing device 40), thereby connecting to the robot 22. For example... Figure 5 As shown, workpiece 26 can initially be set in a planar, flat state, and arms 171-174 can lock their respective joints. In this configuration, workpiece 26 can be engaged from a presenting position (such as from a stack of blanks), clamped with the joints unlocked to achieve a stress-free connection with workpiece 26, then rigidly locked and transported by robot 22 to a forming operation, such as machining via British wheel 46.

[0051] In reference Figure 6 The text shows the relationship with... Figure 5The joining step in workpiece 26 is handled similarly. It includes two arms 34 and 36, each with a gripper 62 at each of its three arm segments. Therefore, each arm 34 and 36 is configured with... Figure 4 The arm portion 150. Each arm 34, 36 can be connected to a common structure (such as a fixing device 40), thereby connecting with, for example... Figure 1 The robot 22 shown is connected. (As shown) Figure 6 As shown, workpiece 26 can initially be in a planar, flat configuration, and arms 34, 36 can unlock their respective joints for engagement, and then lock their respective joints. In this configuration, workpiece 26 can be engaged, clamped, and transported by robot 22 to forming operations, such as machining via British wheel 46.

[0052] Reference Figure 7 Workpiece 26 has been at least partially machined by British wheel 46, and with Figure 6 Compared to the previous configuration, workpiece 26 has already been deformed. For example, as shown, the corners 191-194 of workpiece 26 have moved downwards relative to the center 195 of workpiece 26. Therefore, the grippers 62 move downwards to continue holding workpiece 26. During machining where the geometry of workpiece 26 changes, any number of joints (such as joints 181-186) can be unlocked to allow all six grippers 62 to maintain holding of workpiece 26 during deformation. After machining is complete, or as an intermediate step, any or all joints 181-186 can be relocked.

[0053] like Figure 8 As shown, the workpiece 26 can be machined on the surface 196 of the support and fixing device 197. Any or all joints of the arms 171-174 can be unlocked to allow stress relief in the workpiece 26. For example, when the unlocked joints of the arms 171-174 bend to a greater extent, springback can be allowed in the workpiece 26. For example, as a result of springback when the joints are unlocked, the corner 192 can move upward to position 199.

[0054] Together Figures 1 to 8 Together, in reference Figure 9The process 200 for using the robot system 20 is illustrated in flowchart form. Process 200 begins (202), and workpiece 26 is presented (204) for access by robot 22. For example, workpiece 26 may be placed on a fixture that orients it in a desired position. In some embodiments, workpiece 26 may be presented as a stack of similar workpieces, and one workpiece may be removed from the stack at a time. End effector 24, such as under the control of control system 32, is moved (206) to the presented (204) workpiece 26, and gripper 62 engages with workpiece 26. Before, during, or after engagement with workpiece 26, arms 34, 36 relax with joints unlocked, allowing the arms (such as arms 34, 36) to be stress-free engaged with workpiece 26. In some embodiments, such as during engagement with workpiece 26, the joints of arms 34, 36 may be progressively unlocked. After full engagement, gripper 62, such as by controller 50, grips (212) workpiece 26. After clamping (212) in a relaxed state of the joints, all joints such as those of the arms 34 and 36 are locked (210) by the controller 50 when the arms are bent.

[0055] As process 200 continues, workpiece 26 is gripped (212) and held by robot 22 via end effector 24. Arms 34, 36 are inflexible / rigid, with all their joints locked. Robot 22 is operated, for example by control system 32 via controller 50, to move (214) workpiece 26 to a position for processing by manufacturing machine 28. In an embodiment, workpiece 26 is placed on surface 196 of support fixture 197, and gripper 62 continues to hold workpiece 26. Force sensors (such as load sensors 146, 148) in arms 34, 36 provide signals to controller 50, and stress-free baseline forces at each joint of each arm 34, 36 are recorded (216) in storage device 56 of controller 50 / storage device 56 coupled to controller 50. Force sensors (such as load sensors 146, 148) may be located at each joint of each arm (such as arm 34, 36). Alternatively, the vision system 44 operated by the controller 50 can scan the workpiece 26 to record (216) data of the three-dimensional coordinates of the surface of the workpiece 26, including its curvature.

[0056] Process 200 continues, such as initiating machining (218) of workpiece 26 by forming via manufacturing machine 28, and applying plastic deformation via British wheel 46. During machining (218), gripper 62 continues to hold workpiece 26. Also during machining (218), controller 50 monitors and measures the force at each joint of arms 34, 36 via load sensors 146, 148, and / or controller 50 monitors the deformation / curvature of workpiece 26 via vision system 44. Processor 52 of controller 50 determines (220) whether the force measured on arms 34, 36 exceeds a recorded baseline value and reaches a force threshold (the amount by which the force increases from the baseline force). The force threshold can be determined for each specific application, such as by computer-based modeling and / or testing. For example, the force threshold can be set at a level above the baseline force that prevents movement or disconnection of gripper 62 relative to workpiece 26 when the measured force remains low. In another example, the force threshold can be set at a level that prevents springback of workpiece 26, at least for some stages. The force threshold can be set to the delta force value exceeding the baseline force, where the measured force is compared to the baseline force, and a determination (220) is made when the difference exceeds the delta force value. When a determination (220) is made, it means that the measured force exceeds the force threshold, the process continues, and one or more joints are unlocked (222). When the measured force exceeds the force threshold of one of the arms 34, 36, that arm (arm 34 or arm 36) is unlocked during the continuous machining of workpiece 26 (218) to release the force in that arm by allowing its joints to move. If the measured force exceeds the force threshold of multiple arms 34, 36, machining is paused (218) with multiple arms (e.g., arms 34 and 36) unlocked (222) to release the force by allowing joint movement, and the gripper 62 continues to hold workpiece 26. Once arms 34, 36 are relaxed, their joints are relocked for further machining (218).

[0057] In addition to, or instead of, force information, the controller 50 monitors, for example, the continuous deformation / curvature of the workpiece 26 during processing (218) via the vision system 44. When determination 220 is negative, it means that the measured force does not exceed a force threshold, or instead of determination (220), the process continues to determine, for example, via the controller 50, whether the deformation monitored via the vision system 44 exceeds a baseline stored data value by a deformation threshold amount. When the monitored deformation exceeds the deformation threshold of the workpiece 26, the process 200 continues to unlock (226) the arms 34, 36 by unlocking the joints of the arms 34, 36, thereby relaxing the arms 34, 36. Once the arms 34, 36 are relaxed (this occurs after joint movement), the joints are relocked for further processing (218).

[0058] When determination (224) is negative, it means that the monitored deflection does not exceed the deformation threshold, and / or when proceeding from the unlocking (222) step, process 200 continues to determine (228) whether either the measured force or the monitored deflection exceeds its corresponding threshold. When determined to be negative, it means that both values ​​are below their thresholds, and process 200 continues processing (230). When one or both values ​​exceed their thresholds, the process returns to unlocking (226), and processing (230) continues only if both values ​​are below their corresponding thresholds. In an embodiment, controller 50 may be programmed to automatically move to unlocking (222) and perform full relaxation on all arms (such as arms 34, 36) at defined intervals (such as in a specific bending state) to relieve stress. After relaxation at unlocking (226), the joints are locked, and process 200 continues. When manufacturing machine 28 completes its operation on workpiece 26, robot 22, such as when operated by controller 50, moves workpiece 26 (232) to its completed destination, and gripper 62 is operated to release workpiece 26, and process 200 ends (234). The steps of process 200 can be performed in any order, including in a different order than described above. Furthermore, only some steps in process 200 may be performed, while others may be omitted.

[0059] In summary, the end effector 24 includes one or more lockable arms 34, 36, etc., which can be controllably alternating between rigid and flexible as needed. Arms 34, 36, etc., include links / segments connected by joints, which can be in a locked state with no movement, in an unlocked state to allow movement of the joints with multiple degrees of freedom, or in a smart state to allow movement under applied threshold forces. Locking / unlocking of each or all joints in one or more arms is controlled automatically, for example, by controller 50. The unlocking, relaxation, and relocking of arms 34, 36, etc., performed sequentially during forming can be programmed to achieve incremental springback compensation while the workpiece remains held by gripper 62. Force sensors (such as load sensors 146, 148) can be used to monitor forces (tension / compression / bending / shear) on arms 34, 36, etc. When an increase in force is sensed compared to a baseline, an unlocking sequence can be continuously initiated at each joint until the force drops back to the baseline level. The curvature / deflection of workpiece 26 can be used as an unlocking guide. When the curvature changes beyond a specified threshold, molding can be stopped, and full relaxation can be achieved by unlocking and relocking all arms 34, 36, etc.

[0060] Through the above embodiments, an automated robotic system and method are provided for gripping a workpiece during manufacturing operations using an arm with lockable compliance. The arm of the robotic end effector consists of one or more rigid links with flexible joints that can alternate between a locked state with no movement and an unlocked state with free rotation. The locking and unlocking of the joints can be automatically controlled, either in groups or individually. During the forming process, the locking of the joints is controlled to keep the arm in a position that firmly holds the workpiece while flexibly adapting to changes in the position / orientation of the gripping points on the sheet. The joints can be unlocked to relax and release the forces involved. The lockable arm can be operated to allow rapid springback of the workpiece upon release.

[0061] Although at least one exemplary embodiment has been presented in the foregoing detailed description, it should be understood that numerous variations exist. It should also be understood that the exemplary embodiments or multiple exemplary embodiments are merely examples and are not intended to limit the scope, applicability, or configuration of this disclosure in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient roadmap for implementing the exemplary embodiments or multiple exemplary embodiments. It should be understood that various changes may be made to the function and arrangement of the elements without departing from the scope of this disclosure as set forth in the appended claims and their legal equivalents.

Claims

1. A robot system for manipulating a workpiece, the robot system comprising: An arm having a first segment and a second segment connected to the first segment via a joint assembly, wherein a locking element is provided in the joint assembly; A gripper, which is attached to the arm and configured to alternately grip and release the workpiece; as well as A controller configured to operate the locking mechanism to alternately lock and unlock the joint assembly. The gripper is configured to hold the workpiece during deformation, and the controller is configured to unlock the locking element to allow movement of the joint assembly, thereby releasing the forces generated on the arm during the deformation of the workpiece. The joint assembly includes a force sensor configured to provide a force signal to the controller, wherein the controller is configured to unlock the joint assembly when the force signal exceeds a threshold force.

2. The robot system according to claim 1, wherein, The controller is configured to unlock the locking element while the clamp holds the workpiece.

3. The robot system of claim 1, further comprising a vision system configured to provide the controller with a signal indicating deformation of the workpiece, wherein, The controller is configured to unlock the joint assembly when the signal indicates a deformation exceeding a threshold.

4. The robot system according to claim 1, wherein, The first segment includes an elongated body having a first end, a second end, and a side extending from the first end to the second end, wherein the first end is connected to the joint assembly, and wherein the clamp is connected to the side of the body.

5. The robot system according to claim 1, wherein, The arm is a first arm, and the robot system includes a second arm, the second arm including a second locking element configured to alternately lock and unlock the second arm, and a second gripper configured to alternately grip and release the workpiece. The controller is configured to alternately lock and unlock the second lock.

6. The robot system according to claim 1, wherein, The controller is configured to: A baseline force on the arm is recorded, the baseline force being recorded based on the force signal received prior to deformation of the workpiece; The force is measured from the force sensor after the deformation is initiated; The measured force is compared with the threshold force; and The joint assembly is unlocked when the measured force exceeds the threshold force.

7. The robot system according to claim 1, wherein, The gripper includes a suction cup, and the robot system includes a pneumatic system connected to the suction cup and coupled to the controller, the controller being configured to control the pneumatic system to maintain the connection between the suction cup and the workpiece during the deformation.

8. A method for manipulating a workpiece, the method comprising: Construct an arm having a first segment and a second segment connected to the first segment via a joint assembly, in which a locking element is provided; Connect the gripper to the arm; The workpiece is held by the clamp; Release the workpiece from the clamp; The locking mechanism is operated via a controller to alternately lock and unlock the joint assembly; The workpiece is held in place by the clamp during deformation, and the locking mechanism is unlocked by the controller to allow movement of the joint assembly; as well as The unlocking process releases the force generated on the arm during the deformation of the workpiece. The method further includes: Position the force sensor at the joint assembly; The force sensor provides a force signal to the controller; and When the force signal exceeds the threshold force, the joint assembly is unlocked by the controller.

9. The method of claim 8, comprising: The controller records the baseline force on the arm received from the force sensor before the workpiece is deformed; After the deformation is initiated, the controller receives the measured force from the force sensor. The controller compares the measured force with a threshold force. as well as When the measured force exceeds the threshold force, the joint assembly is unlocked by the controller.

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