Gripper assembly for robot manipulator

Abstract

The present invention relates to a gripper assembly for a robot manipulator. The gripper assembly includes a ball screw assembly including two finger assemblies, a first ball screw nut connected to the first finger assembly, and a ball screw shaft including a first section to which the first ball screw nut is movably attached. An actuator is directly connected to the ball screw shaft and configured to rotate the ball screw shaft about its longitudinal axis to move the first finger assembly toward the second finger assembly when the ball screw shaft is rotated in one of a clockwise direction or a counterclockwise direction, and to move the first finger assembly away from the second finger assembly when the ball screw shaft is rotated in the other of the clockwise direction or the counterclockwise direction.

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE The present disclosure relates to a gripper assembly for a robotic manipulator. Aspects of the present disclosure relate to a gripper assembly and a robotic manipulator including the gripper assembly. [Background technology]

[0002] Known robot grippers operate using an indirect force control method, either a position control method or a force-plus-position control method. In the position control method, the position of each of the gripper's finger assemblies is controlled independently of the gripping force applied to the finger assemblies. In the force-plus-position control method, the position of each of the finger assemblies is controlled relative to a force limit. That is, the force-plus-position control method does not maintain or adjust the gripping force, but simply limits the maximum force that can be applied to the finger assemblies. A problem with these indirect force control methods is that they require an extra force sensor at the contact area of the finger assemblies to measure the gripping force. Furthermore, because force control is performed indirectly via position, even with gripping force feedback, the control is prone to instability due to contact modeling errors. Furthermore, most grippers on the market are not back-drivable, resulting in low interaction safety. Such control methods are also a source of instability and poor control performance.

[0003] SUMMARY OF THE INVENTION It is an object of the present invention to address one or more disadvantages associated with known robotic grippers. Summary of the Invention

[0004] Thus, in a first aspect, there is provided a gripper assembly for a robotic manipulator, the gripper assembly comprising first and second finger assemblies and a ball screw actuator assembly, the ball screw actuator assembly comprising: a first ball screw nut connected to the first finger assembly; a ball screw shaft having a first section to which the first ball screw nut is movably mounted; the ball screw shaft rotatable about its longitudinal axis, and an actuator directly connected to the ball screw shaft and configured to rotate the ball screw shaft about its longitudinal axis, wherein the ball screw nut and ball screw shaft are configured to move the first finger assembly toward the second finger assembly when the ball screw shaft is rotated in one of a clockwise or counterclockwise direction, and to move the first finger assembly away from the second finger assembly when the ball screw shaft is rotated in the other of the clockwise or counterclockwise direction.

[0005] This configuration is advantageous, first, in that it allows the gripper assembly to be controlled using a direct force control scheme, as opposed to using a position control scheme. When using a position control scheme, a target position of the finger assembly is determined based on the item being manipulated or gripped, and the force applied to the item is a function of the target position. Such a control scheme is suitable for applications in which the items being manipulated generally have similar or identical characteristics. However, in other applications, such as an online grocery retail operation with 1,000 or 10,000 items of various characteristics (e.g., shape, size, weight, stiffness, coefficient of friction, etc.), such a control scheme is inappropriate because two similarly sized items may be very different in other respects and therefore the force applied to them by the finger assembly, determined as a function of their respective positions, may be inappropriate. That is, in most cases, when using a position control scheme, the relationship between the applied force and the position of the finger assembly is unknown. However, in the configuration of the present invention, which is suitable for a direct force control scheme, feedback regarding the target position or the position of the finger assembly is not required. Instead, the output torque of the actuator is controlled to match the desired force applied by the finger assembly to the manipulated item. This is made possible by a novel configuration that uses a ball screw actuator assembly that includes a direct connection between the actuator and a ball screw shaft to move the finger assembly. The ball screw actuator assembly is a low-friction transmission device, and in this example, is used to convert the output torque of the actuator into axial reciprocating motion of the finger assembly. Being a low-friction transmission device, in the absence of other transmission mechanisms, such as a gear arrangement between the actuator and the ball screw shaft, means that the applied force of the finger assembly is proportional to the torque output of the actuator, allowing the applied force to be accurately mapped to the torque output, providing precise direct force control capabilities without the need for external force measurement.

[0006] Second, because the ball screw actuator assembly provides low-friction transmission between the actuator assembly and the finger assembly, the gripper assembly is mechanically back-drivable. That is, the finger assemblies can be manually moved toward or away from each other to effect rotation of the ball screw shaft. This ensures that the gripper assembly has a degree of compliance, allowing for safe physical interaction with its workspace.

[0007] Finally, the ball screw actuator assembly can be preloaded to reduce any clearance between the raceways of the first and second ball screw nuts and the first and second sections of the ball screw shaft, minimizing "axial play" or "slack" in the assembly that could otherwise result in errors in the force applied by the finger assembly against the item being manipulated.

[0008] Optionally, the gripper assembly further comprises one or more guide rails, a first carriage assembly movably mounted on the one or more guide rails, and a first support assembly configured to connect the first ball screw nut and the first finger assembly to the carriage assembly, wherein the one or more guide rails guide movement of the first finger assembly, prevent the first ball screw nut from rotating when the ball screw shaft is rotated, and fix a rotational position of the first ball screw nut.

[0009] Optionally, the first support assembly is configured to provide a rigid connection between the first finger assembly and the first carriage assembly and a movable connection between the first ball screw nut and the first carriage assembly. This configuration isolates the ball screw actuator assembly from any forces applied to the gripper assembly as a result of manipulating an item and transmits them to the first carriage assembly and the one or more guide rails. In particular, it ensures that the ball screw shaft is not subjected to any radial forces that could bend the ball screw shaft and, as a result, increase friction between the ball screw and the ball screw shaft.

[0010] Optionally, the ball screw actuator assembly further comprises a second ball screw nut connected to the second finger assembly, wherein the ball screw shaft further comprises a second section to which the second ball screw nut is movably mounted, wherein the first and second ball screw nuts and ball screw shaft are configured to move the first and second finger assemblies toward each other when the ball screw shaft is rotated in one of a clockwise or counterclockwise direction and to move the first and second finger assemblies away from each other when the ball screw shaft is rotated in the other of the clockwise or counterclockwise direction. This configuration provides two opposing movable finger assemblies and provides a wide range of positions.

[0011] Optionally, the gripper assembly further comprises a second carriage assembly movably mounted on the one or more guide rails, and a second support assembly configured to connect the second ball screw nut and the second finger assembly to the second carriage assembly, wherein this configuration prevents the second ball screw nut from rotating when the ball screw shaft rotates, thereby fixing a rotational position of the second ball screw nut.

[0012] Optionally, the second support assembly is configured to provide a rigid connection between the second finger assembly and the second carriage assembly and a movable connection between the second ball screw nut and the second carriage assembly, this arrangement particularly isolating the ball screw shaft from radial loads that arise during manipulation of the item.

[0013] Optionally, the one or more guide rails comprise two guide rails, each guide rail of the two guide rails positioned on either side of the ball screw shaft, this configuration providing a uniform force distribution across the gripper assembly when manipulating an item.

[0014] Optionally, the actuator is disposed between the first and second sections of the ball screw shaft, This configuration provides a more uniform rotation of the ball screw shaft and limits any torsional motion experienced by the shaft.

[0015] Alternatively, the actuator is located at one end of the ball screw shaft.

[0016] Optionally, the first section of the ball screw shaft includes one of a right-handed or left-handed helical trajectory, and the second section of the ball screw shaft includes the other of the right-handed or left-handed helical trajectory.

[0017] Optionally, the ball screw actuator assembly further comprises: a second ball screw nut connected to the second finger assembly; a second ball screw shaft comprising a section to which the second ball screw nut is movably mounted; the second ball screw shaft rotatable about its longitudinal axis; and a second actuator directly connected to the second ball screw shaft and configured to rotate the second ball screw shaft about its longitudinal axis, wherein the second ball screw nut and the second ball screw shaft are configured to move the second finger assembly toward the first finger assembly when the second ball screw shaft is rotated in one of a clockwise or counterclockwise direction, and to move the second finger assembly away from the first finger assembly when the second ball screw shaft is rotated in the other of the clockwise or counterclockwise direction.

[0018] According to a second aspect, there is provided a robotic manipulator comprising a gripper assembly according to the first aspect.

[0019] According to a third aspect, there is provided a manipulator apparatus comprising a robotic manipulator according to the second aspect.

[0020] These and other aspects of the present invention will now be described, by way of example only, with reference to the accompanying drawings. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a schematic diagram of a picking system including a manipulator device according to an embodiment of the present invention. [Figure 2a] FIG. 2a is an isometric view of a gripper assembly according to an embodiment of the present invention for use with the manipulator apparatus of FIG. [Figure 2b] FIG. 2b is a cross-sectional view of the gripper assembly of FIG. 2a in a vertical plane. [Figure 2c] FIG. 2c is a horizontal cross-sectional view of the gripper assembly of FIG. 2a. [Figure 3] FIG. 3 is a perspective view of the fingers and support assembly of the gripper assembly of FIG. 2a, as well as parts of the ball screw actuator and carriage assembly. [Figure 4] FIG. 4 is an isometric view of the support assembly of FIG. [Figure 5] FIG. 5 is a schematic diagram of a gripper assembly according to another embodiment of the present invention. [Figure 6] FIG. 6 is a schematic diagram of a gripper assembly in accordance with yet another embodiment of the present invention.

[0022] In the drawings, like features are indicated by like reference numerals where appropriate. DETAILED DESCRIPTION OF THE INVENTION

[0023] In the following description, specific details are included to provide a thorough understanding of various disclosed embodiments. However, one skilled in the art will recognize that the embodiments can be practiced without one or more of these specific details, or with other methods, components, materials, etc. In some instances, well-known structures associated with the gripper assembly and / or robot, such as processors, sensors, storage devices, network interfaces, workpieces, tension members, fasteners, electrical connectors, mixers, etc., are not shown or described in detail to avoid unnecessarily obscuring the description of the disclosed embodiments.

[0024] Unless the context requires otherwise, throughout this specification and the appended claims, the word "comprise" and variations thereof, such as "comprises" and "comprising," are to be interpreted in their open and inclusive sense, such as "including, but not limited to."

[0025] References throughout this specification to "one," "an," or "another" applied to an "embodiment," "example," or "implementation" mean that a particular feature, structure, or characteristic described in connection with an embodiment, example, or implementation is included in at least one embodiment, example, or implementation. Thus, the appearances of "in one embodiment" or similar phrases in various places throughout this specification do not necessarily all refer to the same embodiment. Furthermore, particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments, examples, or implementations.

[0026] It should be noted that, as used herein and in the appended claims, the user forms "a," "an," and "the" include plural referents unless the content dictates otherwise. Thus, for example, a reference to a robot including a "gripper assembly" includes a gripper assembly, or two or more gripper assemblies. It should be noted that the term "or" is generally used in its sense including "and / or" unless expressly dictated otherwise.

[0027] Referring to FIG. 1 , an example of a picking system 100 adapted for use with the present invention is illustrated. The picking system 100 can form part of an online retail operation, such as an online grocery retail operation, but can also be applied to any other operation requiring the picking and / or sorting of items. In this example, the system 100 includes a manipulator device 102 with a robotic manipulator 121 configured to pick items from a first location and place the items at a second location. The manipulator device 102 is communicatively coupled via a communication interface 104 to other components of the system 100, such as one or more optional operator interfaces 106, from which an observer can observe or monitor the operation of the system 100 and the manipulator device 102. The observer interface 106 may include a WIMP interface and an output display of a narrative or dynamic representation of the manipulator device 102 in a context or scenario. For example, the dynamic representation of the manipulator device 102 may include video and audio feeds, e.g., computer-generated animation. Examples of suitable communication interfaces 104 include a wire-based network or communication interface, an optical-based network or communication interface, a wireless network or communication interface, or a combination of wired, optical, and / or wireless network or communication interfaces.

[0028] The system 100 further comprises a control system 108 including at least one controller 110 communicatively coupled to the manipulator device 102 and other components of the system 100 via a communication interface 104. The controller 110 comprises a control unit or computing device having one or more electronic processors embedded therein a set of control instructions provided as processor-executable data that, when executed, cause the controller 110 to issue actuation commands or control signals to the manipulator device 102 and the manipulator 121 to perform various methods and actions, such as identifying and manipulating items. The one or more electronic processors may include at least one logic processing unit such as one or more microprocessors, central processing units (CPUs), digital signal processors (DSPs), graphics processing units (GPUs), application specific integrated circuits (ASICs), programmable gate arrays (PGAs), programmed logic units (PGAs), and the like. In some implementations, controller 110 is a smaller processor-based device such as a mobile phone, single-board computer, embedded computer, etc., which may be interchangeably referred to as a computer, server, or analyzer. A set of control instructions may be provided as processor-executable data associated with the operation of system 100 and manipulator apparatus 102 contained in a non-transitory processor-readable storage device 112 that forms part of system 100 and is accessible to controller 110 via communications interface 104. In some embodiments, storage device 112 comprises two or more separate devices. Storage device 112 may include, for example, one or more volatile storage devices, such as random access memory (RAM), and one or more non-volatile storage devices, such as read-only memory (ROM), flash memory, magnetic hard disk (HDD), optical disk, solid-state disk (SSD), etc.Those skilled in the art will appreciate that storage may be implemented in a variety of ways, such as read-only memory (ROM), random access memory (RAM), hard disk drive (HDD), network drive, flash memory, digital versatile disc (DVD), any other form of computer- and processor-readable memory or storage medium, and / or combinations thereof. Storage may be read-only or read-and-write, as appropriate.

[0029] The system 100 includes a sensor subsystem 114 comprising one or more sensors that detect, sense, or measure the condition or state of the manipulator apparatus 102 and / or the conditions of the environment or workspace in which the manipulator 121 operates, and generate or provide corresponding sensor data or information. The sensor information includes environmental sensor information representative of environmental conditions within the workspace of the manipulator 121, as well as information representative of the condition or state of the manipulator apparatus 102, including its various subsystems and components, and characteristics of the item to be manipulated. The acquired data can be transmitted via the communication interface 104 to the controller 110 to instruct the manipulator 121 accordingly. Such information can include, for example, diagnostic sensor information useful in diagnosing the state or condition of the manipulator apparatus 102 or the environment in which the manipulator 121 operates. For example, such sensors may include contact sensors, force sensors, strain gauges, vibration sensors, position sensors, orientation sensors, accelerometers, etc. Such sensors may include one or more of a camera or imager 116 (e.g., responsive in the visible and / or non-visible range of the electromagnetic spectrum, including infrared and ultraviolet), radar, sonar, touch sensors, pressure sensors, load cells, microphones 118, weather sensors, chemical sensors, etc. In some implementations, the diagnostic sensors include sensors for monitoring the status and / or health of an on-board power source (e.g., a battery array, an ultracapacitor array, a fuel cell array) in the manipulator device 102. In some embodiments, the one or more sensors comprise a receiver for receiving position and / or orientation information regarding the manipulator 121, for example, a Global Positioning System (GPS) receiver for receiving GPS data, two or more time signals for the controller 110 to generate position measurements based on data in the signal, such as time of flight, signal strength, or other data to achieve a position measurement. Also, for example, one or more accelerometers forming part of the manipulator device 102 may be provided in the manipulator 121 to obtain inertial or orientation data in one, two, or three axes regarding its movement.

[0030] Manipulator 121 may be operated over a network, such as network 106, by a human operator at an operator interface. In a human-operator control or steering mode, the human operator observes a representation of sensor data, e.g., video, audio, or tactile data, received from one or more sensors of sensor subsystem 114. The human operator then acts conditioned by their perception of the representation of the data and creates information or executable control instructions to guide manipulator 121 accordingly. In the steering mode, manipulator device 102 may execute control instructions as received from operator interface 106 in real time (e.g., without additional delay) based on the sensed information and without consideration of other control instructions.

[0031] In some implementations, the manipulator device 102 operates autonomously, i.e., a human operator does not generate control instructions in the operator interface 106 to direct the manipulator 121. The manipulator device 102 may operate in an autonomous control mode by executing autonomous control instructions. For example, the controller 110 can use sensor data from one or more sensors in the sensor subsystem 114, which sensor data is associated with operator-generated control instructions from one or more times the manipulator device 102 was in pilot mode, to generate autonomous control instructions for subsequent use. In autonomous mode, for example, by using deep learning techniques to extract features from the sensor data, the manipulator device 102 autonomously recognizes features or conditions in its environment and the item to be manipulated and, in response, performs a defined action, set of actions, task, or pipeline or sequence of tasks. In some implementations, the controller 110 autonomously perceives features and / or conditions in the environment surrounding the manipulator 121, as represented by sensor data from the sensor subsystem 114 and one or more virtual items synthesized into the environment, and issues control signals to the manipulator device 102 to perform one or more actions or tasks in response to the representations being presented.

[0032] In some examples, the manipulator device 102 may be autonomously controlled at some times while being piloted, operated, or controlled by a human operator at other times; that is, operating under an autonomous control mode and changing to operate under a piloted (i.e., non-autonomous) mode. In another mode of operation, the manipulator device 102 may replay or execute control instructions previously executed in a human-operator controlled (or piloted) mode. That is, the manipulator device 102 may operate without sensor data, based on replayed pilot data.

[0033] Manipulator device 102 further includes a communications interface subsystem 124, e.g., a network interface device communicatively coupled to bus 126 and providing bidirectional communication with other components of system 100 (e.g., controller 110) via communications interface 104. Communications interface subsystem 124 may be any circuitry that affects bidirectional communication of processor-readable data and processor-executable instructions, such as a radio (e.g., a radio or microwave frequency transmitter, receiver, transceiver), communications port, and / or associated controller. Suitable communications protocols include FTP, HTTP, web services, SOAP with XML, Wi-Fi® compliant, Bluetooth® compliant, cellular (e.g., GSM®, CDMA), etc.

[0034] The manipulator 121 is an electromechanical machine that includes one or more appendages, such as a robotic arm 120, and a gripper assembly or end effector 122 attached to the end of the robotic arm 120. The gripper assembly 122 is a complexly designed device configured to interact with an environment to perform several tasks, including, for example, grasping, grasping, releasably engaging, or otherwise interacting with an item. The manipulator apparatus 102 further includes a motion subsystem 130 that is communicatively coupled to the robotic arm 120 and the gripper assembly 122. The motion subsystem 130 includes one or more motors, solenoids, other actuators, linkages, drive belts, etc., operable to move the robotic arm 120 and / or the gripper assembly 122 through a range of motion according to actuation commands or control signals issued by the controller 110. The motion subsystem 130 is communicatively coupled to the controller 110 via a bus 126.

[0035] The manipulator device 102 also includes an output subsystem 128 that includes one or more output devices, such as a speaker, a light, or a display, that enable the manipulator device 102 to transmit signals into the workspace, for example, to communicate with an operator and / or another manipulator device 102.

[0036] Those skilled in the art will understand that the components of manipulator device 102 may be changed, combined, divided, omitted, etc. In some examples, one or more of communication interface subsystem 124, output subsystem 128, and / or movement subsystem 130 may be combined. In other examples, one or more of the subsystems (e.g., kinematic subsystem 130) are divided into additional subsystems.

[0037] As previously mentioned, the manipulator 121 is configured to remove an article, workpiece, or item from a first location, such as a storage tote, and place the item in a second location, such as a shipping tote; FIGS. 2a-2c illustrate an example of a gripper assembly 122 suitable for performing such an operation. In this example, the gripper assembly 122 comprises a housing 142 (the sides of which have been removed in FIG. 2a to facilitate this illustration) and a connector or interface 123 for connecting the gripper assembly 122 to the robot arm 120. The gripper assembly 122 further comprises first and second finger assemblies 132, 146, which are shown in a closed configuration. The finger assemblies 132, 146 are configured to move away from or toward each other as needed to grip or release an item. To that end, the gripper assembly further comprises a ball screw actuator assembly, generally designated 134, comprising first and second ball screw nuts 136, 150 along with a ball screw shaft 138. First ball screw nut 136 is connected to first finger assembly 132 by first support assembly 133, and second ball screw nut 150 is connected to second finger assembly 132 by second support assembly 135. Support assemblies 133, 135 extend through elongated openings 163 in housing 142, which are configured to facilitate lateral movement of finger assemblies 132, 146. Ball screw shaft 138 includes a first section 140 having one of a right-handed or left-handed helical track to which first ball screw nut 136 having a complementary helical track is movably mounted, and a second section 152 having the other of the right-handed or left-handed helical track to which second ball screw nut 150 is movably mounted. Ball screw actuator assembly 134 further includes an actuator 154 directly connected to ball screw shaft 138 and configured to rotate ball screw shaft 138 about its longitudinal axis 144 in clockwise and counterclockwise directions.In this embodiment, the actuator 154 comprises a DC motor 155 held within a motor housing 157, although in other embodiments, the actuator 154 may instead include an AC motor. A ball screw shaft 138 is fixed to a rotor 161 and rotatably supported in the motor housing 157 by a support bearing 159. The first and second ball screw nuts 136, 150 and the ball screw shaft 138 are configured such that, upon receipt of an appropriate actuation command issued by the controller 110 at the motion subsystem 130, the first and second finger assemblies 132, 146 move toward each other in one of a clockwise or counterclockwise direction when the ball screw shaft 138 is rotated by the actuator 154, and move the first and second finger assemblies 132, 146 away from each other, increasing the gap therebetween, when the ball screw shaft 138 is rotated in the other of the clockwise or counterclockwise direction by the actuator 154, such that the finger assemblies 132, 146 can grip an item. This configuration, using the ball screw actuator assembly 134 to provide a direct connection between the actuator 154 and the ball screw shaft 138 to move the finger assemblies 132, 146, is advantageous for several reasons.

[0038] First, it allows for the gripper assembly 122 to be controlled using a direct force control scheme, as opposed to using a position control scheme. When using a position control scheme, a target position of the finger assemblies is determined based on the item being manipulated or gripped, and the force applied to the item is a function of the target position. Such a control scheme is suitable for applications in which the items being manipulated generally have similar or identical characteristics. However, in other applications, such as an online grocery retail operation with 1,000 or 10,000 items that vary in characteristics (e.g., shape, size, weight, stiffness, coefficient of friction, etc.), such a control scheme is inappropriate because two similarly sized items may differ in other respects, and therefore the force applied to them by the finger assemblies, determined as a function of their respective positions, may be inappropriate. That is, in most cases, when using a position control scheme, the relationship between the applied force and the position of the finger assemblies is often unknown, and therefore the use of a force sensor is required to measure the gripping force. However, in this configuration, which is suitable for a direct force control scheme, no feedback is required regarding the target position or the position of the finger assemblies 132, 146. Instead, the output torque of the actuator 154 is controlled to match the desired force applied to the item being manipulated by the finger assemblies 132, 146. This is made possible by a novel arrangement for moving the finger assemblies 132, 146 using a ball screw actuator assembly 134 that includes a direct connection between the actuator 154 and a ball screw shaft 138. The ball screw actuator assembly 134 is a low-friction transmission device that, in this example, is used to convert the output torque of the actuator 154 into axial reciprocating motion of the finger assemblies 132, 146.Being a low friction transmission device, in the absence of other transmission mechanisms such as a gear arrangement between the actuator 154 and the ball screw shaft 138, the applied or gripping force of the finger assemblies 132, 146 is directly proportional to the torque output of the actuator 154, meaning that the applied force can be accurately mapped to the torque output to provide precise direct force control capability without the need for external force measurements.

[0039] Second, because the ball screw actuator assembly 134 provides a low-friction transmission between the actuator 154 and the finger assemblies 132, 146, the gripper assembly 122 is mechanically back-drivable. That is, the first and second finger assemblies 132, 146 can be manually moved toward or away from each other to effect rotation of the ball screw shaft 138. This ensures that the gripper assembly 122 has a degree of compliance, allowing for safe physical interaction with its workspace.

[0040] In this example, gripper assembly 122 further includes two guide rails 156 supported within housing 142 on either side of ball screw shaft 138 by mounts 158. Guide rails 156 function, in part, to guide lateral movement of finger assemblies 132, 146, prevent first and second ball screw nuts 136, 150 from rotating when ball screw shaft 138 is rotated, and fix the rotational positions of first and second ball screw nuts 136, 150. To that end, gripper assembly 122 further includes first and second carriage assemblies 160, 162, each including two linear guides 164 slidably mounted on guide rails 156. Referring to FIG. 3 , first support assembly 133 is configured to connect first ball screw nut 136 and first finger assembly 132 to first carriage assembly 160, and second support assembly 135 is configured to connect second ball screw nut 150 and second finger assembly 146 to second carriage assembly 162. Each support assembly 133, 135 includes a pair of support arms 166 and a pair of ball screw nut connectors 168. Each support arm 166 is rigidly connected to its respective finger assembly 132, 146 and linear guide 164 by a first plurality of fasteners 170 (some of which are not visible in FIG. 3 ). Similarly, each ball screw nut connector 168 is rigidly fastened to one of ball screw nuts 136, 150 by a second plurality of fasteners 172, but is movably connected to its respective support arm 166, providing an indirect connection to its respective linear guide 164. 4, the movable connection includes a generally circular protrusion 174 that extends from one end of the ball screw nut connector 168 into an open channel 176 formed in a portion of the support arm 166 that fastens to the linear guide 164. The width of the channel 176 is such that there is no play between the channel and the protrusion 174 when the ball screw nut connector 168 moves with the ball screws 136, 150.This ensures that movement of the ball screws 136, 150 along the ball screw shaft 138, as indicated by arrow 178, is accurately transmitted to the finger assemblies 132, 146. However, the length of the channel 176 (i.e., the dimension of the channel parallel to the major axis of the support arm 166) is elongated to allow play between the protrusion 174 and the channel 176 along the length of the channel 176. That is, the protrusion 174 and the channel 176 are configured to allow relative movement therebetween along the length of the channel 176, while preventing such movement across the width of the channel 176. Specifically, the channel 176 is long enough to ensure that the protrusion 174 cannot contact either end of the channel 176 during use, thereby preventing the protrusion 174 from carrying any load via its respective support arm 166. This configuration isolates the ball screw actuator assembly 134 from any forces applied to the gripper assembly 122 during manipulation of an item and transmits them to the carriage assemblies 160, 162 and the guide rail 156. In particular, it ensures that no radial forces are applied to the ball screw shaft 138 which may cause the ball screw shaft 138 to bend and, as a result, increase friction between the ball screws 136, 150 and the ball screw shaft 138.

[0041] 5 , gripper assembly 222 includes a first finger assembly 232 and a ball screw actuator assembly 234. Ball screw actuator assembly 234 includes a ball screw nut 236 connected to first finger assembly 232 and a ball screw shaft 238 including a section 240 to which ball screw nut 236 is movably mounted, for moving first finger assembly 232 back and forth along section 240, as indicated by arrow 241. Ball screw shaft 238 is suitably secured within housing 242 of gripper assembly 222 such that ball screw shaft 238 is rotatable about its longitudinal axis 244 as provided by actuator 254 directly connected to ball screw shaft 238 and forming part of ball screw actuator assembly 234. Gripper assembly 222 further includes a second finger assembly 246 held within housing 242 in a fixed position relative to first finger assembly 232. Actuator 254 is disposed at the end of housing 242 remote from second finger assembly 246 and is configured to rotate ball screw shaft 238 in either a clockwise or counterclockwise direction about its longitudinal axis 244. Ball screw nut 236 and ball screw shaft 238 are configured such that, upon receipt of an appropriate actuation command issued by controller 110 at motion subsystem 130, ball screw nut 236 moves first finger assembly 232 toward second finger assembly 246 when ball screw shaft 238 is rotated in one of the clockwise or counterclockwise direction by actuator 254, and moves first finger assembly 232 away from second finger assembly 246 when ball screw shaft 238 is rotated in the other of the clockwise or counterclockwise direction.

[0042] 6 , gripper assembly 322 includes a first finger assembly 332 and a ball screw actuator assembly 334. Ball screw actuator assembly 334 includes a first ball screw nut 336 connected to first finger assembly 332 and a first ball screw shaft 338 including a section 340 to which first ball screw nut 336 is movably mounted, and moves first finger assembly 332 back and forth along first section 340, as indicated by arrow 341. First ball screw shaft 338 is suitably secured within housing 342 of gripper assembly 322 such that first ball screw shaft 338 is rotatable about its longitudinal axis 344. Ball screw actuator assembly 334 further includes a first actuator 354 directly connected to first ball screw shaft 338 and configured to rotate first ball screw shaft 338 about its longitudinal axis 344 in either a clockwise or counterclockwise direction. Ball screw nut 336 and ball screw shaft 338 are configured to move first finger assembly 332 toward second finger assembly 346 when first ball screw shaft 338 is rotated in one of a clockwise or counterclockwise direction by first actuator 354, and to move first finger assembly 332 away from second finger assembly 346 when first ball screw shaft 338 is rotated in the other of the clockwise or counterclockwise direction. Ball screw actuator assembly 334 further includes a second ball screw nut 350 connected to second finger assembly 346 and a second ball screw shaft 356 rotatable about its longitudinal axis 344. Second ball screw shaft 356 includes a section 352 to which second ball screw nut 350 is movably mounted. The ball screw actuator assembly 334 further includes a second actuator 358 directly connected to the second ball screw shaft 356 and configured to rotate the second ball screw shaft 356 about its longitudinal axis 344.The second ball screw nut 350 and the second ball screw shaft 356 are configured to move the second finger assembly 346 toward the first finger assembly 332 when the second ball screw shaft 356 is rotated in one of a clockwise or counterclockwise direction, and to move the second finger assembly 346 away from the first finger assembly 332 when the second ball screw shaft 356 is rotated in the other of a clockwise or counterclockwise direction. The inventions described in the original claims of this application are set forth below. [1] A gripper assembly for a robotic manipulator, comprising: first and second finger assemblies; a ball screw actuator assembly, the ball screw actuator assembly comprising: a first ball screw nut connected to the first finger assembly; a ball screw shaft having a first section to which the first ball screw nut is movably mounted, the ball screw shaft being rotatable about its longitudinal axis; an actuator directly connected to the ball screw shaft and configured to rotate the ball screw shaft about its longitudinal axis; wherein the ball screw nut and the ball screw shaft are configured to move the first finger assembly toward the second finger assembly when the ball screw shaft is rotated in one of the clockwise or counterclockwise directions, and to move the first finger assembly away from the second finger assembly when the ball screw shaft is rotated in the other of the clockwise or counterclockwise directions. [2] one or more guide rails; a first carriage assembly movably mounted on the one or more guide rails; The gripper assembly of [1], further comprising: a first support assembly configured to connect the first ball screw nut and the first finger assembly to the carriage assembly. [3] The gripper assembly described in [2], wherein the first support assembly is configured to provide a rigid connection between the first finger assembly and the first carriage assembly, and a movable connection between the first ball screw nut and the first carriage assembly. [4] The gripper assembly of any one of [1] to [3], wherein the ball screw actuator assembly further comprises a second ball screw nut connected to the second finger assembly, the ball screw shaft further comprises a second section to which the second ball screw nut is movably attached, and the first and second ball screw nuts and the ball screw shaft are configured to move the first and second finger assemblies toward each other when the ball screw shaft is rotated in one of a clockwise or counterclockwise direction, and to move the first and second finger assemblies away from each other when the ball screw shaft is rotated in the other of the clockwise or counterclockwise direction. [5] a second carriage assembly movably mounted on one or more guide rails; and The gripper assembly described in [4] according to [2] or any claim dependent thereon, further comprising: a second support assembly configured to connect the second ball screw nut and the second finger assembly to the second carriage assembly. [6] The gripper assembly described in [5], wherein the second support assembly is configured to provide a rigid connection between the second finger assembly and the second carriage assembly and a movable connection between the second ball screw nut and the second carriage assembly. [7] A gripper assembly as described in [2] or any claim dependent thereon, wherein the one or more guide rails include two guide rails, each guide rail of the two guide rails being positioned on either side of the ball screw shaft. [8] A gripper assembly according to any one of [4] to [7], wherein the actuator is disposed between the first section and the second section of the ball screw shaft. [9] A gripper assembly according to any one of [1] to [8], wherein the actuator is disposed at one end of the ball screw shaft.

[10] The gripper assembly of any one of [1] to [9], wherein the first section of the ball screw shaft has one of a right-handed or left-handed helical trajectory.

[11] A gripper assembly as described in

[10] that depends on [4] or any claim dependent thereon, wherein the second section of the ball screw shaft includes the other of the clockwise or counterclockwise helical track.

[12] The ball screw actuator assembly a second ball screw nut connected to the second finger assembly; a second ball screw shaft having a section to which the second ball screw nut is movably mounted, the second ball screw shaft being rotatable about its longitudinal axis; and a second actuator directly connected to the second ball screw shaft and configured to rotate the second ball screw shaft about its longitudinal axis, wherein the second ball screw nut and the second ball screw shaft are configured to move the second finger assembly toward the first finger assembly when the second ball screw shaft is rotated in one of a clockwise or counterclockwise direction, and to move the second finger assembly away from the first finger assembly when the second ball screw shaft is rotated in the other of the clockwise or counterclockwise direction.

[13] A robot manipulator comprising the gripper assembly according to any one of [1] to

[12] .

[14] A manipulator device comprising the robot manipulator according to

[13] .

Claims

1. 1. A gripper assembly for a robotic manipulator, comprising: first and second finger assemblies; a ball screw actuator assembly, the ball screw actuator assembly comprising: a first ball screw nut connected to the first finger assembly; a ball screw shaft having a first section to which the first ball screw nut is movably mounted, the ball screw shaft being rotatable about its longitudinal axis; an actuator directly connected to the ball screw shaft and configured to rotate the ball screw shaft about its longitudinal axis; wherein the ball screw nut and the ball screw shaft are configured to move the first finger assembly toward the second finger assembly when the ball screw shaft is rotated in one of the clockwise and counterclockwise directions, and to move the first finger assembly away from the second finger assembly when the ball screw shaft is rotated in the other of the clockwise and counterclockwise directions; one or more guide rails; a first carriage assembly movably mounted on the one or more guide rails; a first support assembly configured to connect the first ball screw nut and the first finger assembly to the carriage assembly; A gripper assembly, wherein the first support assembly is configured to provide a rigid connection between the first finger assembly and the first carriage assembly and a movable connection between the first ball screw nut and the first carriage assembly.

2. 2. The gripper assembly of claim 1, wherein the ball screw actuator assembly further comprises a second ball screw nut connected to the second finger assembly, the ball screw shaft further comprising a second section to which the second ball screw nut is movably mounted, the first and second ball screw nuts and the ball screw shaft configured to move the first and second finger assemblies toward each other when the ball screw shaft is rotated in one of a clockwise or counterclockwise direction and to move the first and second finger assemblies away from each other when the ball screw shaft is rotated in the other of the clockwise or counterclockwise direction.

3. 3. The gripper assembly of claim 2, further comprising: a second carriage assembly movably mounted on one or more guide rails; and a second support assembly configured to connect the second ball screw nut and the second finger assembly to the second carriage assembly.

4. 4. The gripper assembly of claim 3, wherein the second support assembly is configured to provide a rigid connection between the second finger assembly and the second carriage assembly and a movable connection between the second ball screw nut and the second carriage assembly.

5. The gripper assembly of claim 1 , wherein the one or more guide rails comprise two guide rails, each guide rail of the two guide rails positioned on either side of the ball screw shaft.

6. The gripper assembly of claim 2 , wherein the actuator is disposed between the first section and the second section of the ball screw shaft.

7. The gripper assembly of claim 1 , wherein the actuator is disposed at one end of the ball screw shaft.

8. The gripper assembly of claim 2 , wherein the first section of the ball screw shaft comprises one of a right-handed or left-handed helical track.

9. The gripper assembly of claim 8 , wherein a second section of the ball screw shaft includes the other of the right-handed or left-handed helical track.

10. The ball screw actuator assembly a second ball screw nut connected to the second finger assembly; a second ball screw shaft having a section to which the second ball screw nut is movably mounted, the second ball screw shaft being rotatable about its longitudinal axis; a second actuator directly connected to the second ball screw shaft and configured to rotate the second ball screw shaft about its longitudinal axis, wherein the second ball screw nut and the second ball screw shaft are configured to move the second finger assembly toward the first finger assembly when the second ball screw shaft is rotated in one of a clockwise or counterclockwise direction and to move the second finger assembly away from the first finger assembly when the second ball screw shaft is rotated in the other of the clockwise or counterclockwise direction.

11. A robot manipulator comprising a gripper assembly according to any one of claims 1 to 10.

12. A manipulator system comprising the robot manipulator of claim 11.

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