Method for identifying external force applied to robot arm, robot arm, and storage medium

Abstract

The present disclosure relates to a method for determining an external force applied to a robot arm. The robot arm (10) includes multiple links (11), multiple joints (12), and multiple 6-DOF force / torque sensors (14). In this method, inertial characteristic parameters and motion state parameters of each link are determined (S1, S2), and the inertial force and inertial torque at the center of gravity of a target link are determined (S3). The 6-DOF force / torque sensors acquire the forces and torques between both ends of the target link and the corresponding joints (S4). The external force applied to the target link is determined based on the inertial force and inertial torque at the center of gravity of the target link and the forces and torques between both ends of the target link and the corresponding joints (S5).

Description

[Technical Field]

[0001] The present disclosure relates to the field of robotics, and specifically to a method for identifying an external force applied to a robot arm, a robot arm, and a storage medium. [Background technology]

[0002] Currently, robotic arms are widely used in various fields, such as industrial production and logistics and transportation. Due to the complex external environment, external force impacts are unavoidable during the operation of a robotic arm. If the external force applied to a robotic arm cannot be accurately detected, the robotic arm will be unable to respond to the external force, such as impact, which will affect the operation of the robotic arm. Therefore, accurately detecting the external force applied to a robotic arm is extremely important for a robotic arm. Summary of the Invention [Means for solving the problem]

[0003] In a first aspect, the present disclosure provides a method for determining an external force applied to a robot arm, the robot arm including a plurality of links and a plurality of joints connected in sequence, the links being connected via the joints, and the joints at both ends of at least some of the links being provided with six-degree-of-freedom (6-DOF) force / torque sensors configured to detect forces and torques applied to the corresponding joints. The method includes the steps of acquiring inertial characteristic parameters including a mass, a center of gravity, and a rotational inertia of each of the links, determining motion state parameters including an angular velocity, an angular acceleration, and a linear acceleration of each of the links, determining an inertial force and an inertial torque at the center of gravity of a target link based on the motion state parameters of each of the links and the inertial characteristic parameters, acquiring forces and torques between both ends of the target link and the corresponding joints using the 6-DOF force / torque sensors, and determining the external force applied to the target link based on the inertial force and inertial torque at the center of gravity of the target link and the forces and torques between both ends of the target link and the corresponding joints.

[0004] In one embodiment, the step of determining the motion state parameters of each said link comprises: acquiring connection parameters of each of the joints and angle information of each of the joints; determining a motion state parameter of each of the links according to a robot dynamics principle based on the inertial characteristic parameter of each of the links, the connection parameter of each of the joints, and the angle information of each of the joints; The connection parameters are parameters that indicate the spatial positional relationship between two adjacent links, and the angle information includes a joint angular position, a joint angular velocity, and a joint angular acceleration.

[0005] In one embodiment, each link is provided with an inertial measurement unit configured to measure the angular velocity, angular acceleration and linear acceleration of the corresponding link, and the step of determining the motion state parameters of each link includes obtaining the motion state parameters of each link from the inertial measurement unit.

[0006] In one embodiment, the step of determining the inertial force and the inertial torque at the center of gravity of the target link based on the motion state parameters and the inertial characteristic parameters of each of the links includes determining the inertial force and the inertial torque at the center of gravity of the target link based on the motion state parameters and the inertial characteristic parameters of each of the links using a backward recursive equation of the recursive Newton-Euler equations.

[0007] In one embodiment, the step of determining an external force to be applied to the target link based on an inertial force and an inertial torque at the center of gravity of the target link and a force and a torque between both ends of the target link and the corresponding joint includes determining a first difference between the inertial force at the center of gravity of the target link and a force between both ends of the target link and the corresponding joint, and determining a magnitude and a direction of the external force to be applied to the target link based on the first difference.

[0008] In one embodiment, the method further includes a step of determining a net torque of the target link at a reference point based on a second difference between the torque between both ends of the target link and the corresponding joint and an inertial torque at the center of gravity of the target link, and a step of determining a position of an external force applied to the target link relative to the reference point based on the net torque of the target link at the reference point and the magnitude and direction of the external force applied to the target link.

[0009] In one embodiment, the method further includes, before determining a position of an external force applied to the target link based on a net torque of the target link at a reference point and a magnitude and a direction of the external force applied to the target link, determining whether the magnitude of the external force is greater than a predetermined first threshold value, and determining whether the value of the net torque is greater than a predetermined second threshold value; determining that no external force is being applied to the target link when the magnitude of the external force is smaller than the first threshold value; and determining that the external force applied to the target link is located at the reference point when the magnitude of the external force is equal to or greater than the first threshold and the value of the net torque is smaller than the second threshold.

[0010] In one embodiment, if the magnitude of the external force is greater than or equal to the first threshold and the value of the net torque is greater than the second threshold, the position of the external force applied to the target link relative to the reference point is determined based on the following equation:

[0011] JPEG2026504585000002.jpg52170

[0012] In a second aspect, the present disclosure provides a robot arm including a plurality of sequentially connected links, a plurality of joints, a plurality of six-degree-of-freedom force / torque sensors, at least one memory, and at least one processor, wherein the links are connected via the joints, and the six-degree-of-freedom force / torque sensors are provided at the joints on both ends of at least some of the links and configured to detect forces and torques applied to the corresponding joints. The at least one memory stores computer program commands, and when the computer program commands are executed by the at least one processor, the following steps are performed: acquiring inertial characteristic parameters including the mass, center of gravity, and rotational inertia of each of the links; determining motion state parameters including the angular velocity, angular acceleration, and linear acceleration of each of the links; determining an inertial force and inertial torque at the center of gravity of a target link based on the motion state parameters of each of the links and the inertial characteristic parameters; acquiring forces and torques between both ends of the target link and the corresponding joints using the 6-DOF force / torque sensor; and determining an external force to be applied to the target link based on the inertial force and inertial torque at the center of gravity of the target link and the forces and torques between both ends of the target link and the corresponding joints.

[0013] In one embodiment, the step of determining the motion state parameters of each said link comprises: acquiring connection parameters of each of the joints and angle information of each of the joints; determining a motion state parameter of each of the links according to a robot dynamics principle based on the inertial characteristic parameter of each of the links, the connection parameter of each of the joints, and the angle information of each of the joints; The connection parameters are parameters that indicate the spatial positional relationship between two adjacent links, and the angle information includes a joint angular position, a joint angular velocity, and a joint angular acceleration.

[0014] In one embodiment, each link is provided with an inertial measurement unit configured to measure the angular velocity, angular acceleration and linear acceleration of the corresponding link, and the step of determining the motion state parameters of each link includes obtaining the motion state parameters of each link from the inertial measurement unit.

[0015] In one embodiment, the step of determining the inertial force and the inertial torque at the center of gravity of the target link based on the motion state parameters and the inertial characteristic parameters of each of the links includes determining the inertial force and the inertial torque at the center of gravity of the target link based on the motion state parameters and the inertial characteristic parameters of each of the links using a backward recursive equation of the recursive Newton-Euler equations.

[0016] In one embodiment, the step of determining an external force to be applied to the target link based on an inertial force and an inertial torque at the center of gravity of the target link and a force and a torque between both ends of the target link and the corresponding joint includes determining a first difference between the inertial force at the center of gravity of the target link and a force between both ends of the target link and the corresponding joint, and determining a magnitude and a direction of the external force to be applied to the target link based on the first difference.

[0017] In one embodiment, the following steps are further performed: determining a net torque of the target link at a reference point based on a second difference between the torque between both ends of the target link and the corresponding joint and the inertial torque at the center of gravity of the target link; and determining a position of an external force applied to the target link relative to the reference point based on the net torque of the target link at the reference point and the magnitude and direction of the external force applied to the target link.

[0018] In one embodiment, before determining the position of the external force applied to the target link based on the net torque of the target link at the reference point and the magnitude and direction of the external force applied to the target link, determining whether the magnitude of the external force is greater than a predetermined first threshold value, and determining whether the value of the net torque is greater than a predetermined second threshold value; determining that no external force is being applied to the target link when the magnitude of the external force is smaller than the first threshold value; If the magnitude of the external force is greater than or equal to the first threshold and the value of the net torque is less than the second threshold, a step of determining that the external force applied to the target link is located at the reference point is performed.

[0019] In one embodiment, if the magnitude of the external force is greater than or equal to the first threshold and the value of the net torque is greater than the second threshold, the position of the external force applied to the target link relative to the reference point is determined based on the following equation:

[0020] JPEG2026504585000003.jpg52170

[0021] In a third aspect, the present disclosure provides a non-transitory computer-readable recording medium having a computer program stored therein, the computer program being executed by at least one processor to perform the following steps: acquiring inertial characteristic parameters including the mass, center of gravity, and rotational inertia of each of the links; determining motion state parameters including the angular velocity, angular acceleration, and linear acceleration of each of the links; determining an inertial force and inertial torque at the center of gravity of a target link based on the motion state parameters and the inertial characteristic parameters of each of the links; acquiring forces and torques between both ends of the target link and the corresponding joints using the 6-DOF force / torque sensor; and determining an external force to be applied to the target link based on the inertial force and inertial torque at the center of gravity of the target link and the forces and torques between both ends of the target link and the corresponding joints.

[0022] In one embodiment, the step of determining the motion state parameters of each said link comprises: acquiring connection parameters of each of the joints and angle information of each of the joints; determining a motion state parameter of each of the links according to a robot dynamics principle based on the inertial characteristic parameter of each of the links, the connection parameter of each of the joints, and the angle information of each of the joints; The connection parameters are parameters that indicate the spatial positional relationship between two adjacent links, and the angle information includes a joint angular position, a joint angular velocity, and a joint angular acceleration.

[0023] In one embodiment, the step of determining an external force to be applied to the target link based on an inertial force and an inertial torque at the center of gravity of the target link and a force and a torque between both ends of the target link and the corresponding joint includes determining a first difference between the inertial force at the center of gravity of the target link and a force between both ends of the target link and the corresponding joint, and determining a magnitude and a direction of the external force to be applied to the target link based on the first difference.

[0024] In one embodiment, when the computer program is executed by at least one processor, the following steps are further performed: determining a net torque of the target link at a reference point based on a second difference between the torque between both ends of the target link and the corresponding joint and an inertial torque at the center of gravity of the target link; and determining a position of an external force applied to the target link relative to the reference point based on the net torque of the target link at the reference point and the magnitude and direction of the external force applied to the target link.

[0025] The above description merely provides an outline of the technical solution of the present disclosure. In order to make the technical solution of the present disclosure more clearly understood and enabled to be implemented based on the description in this specification, and to further clarify and facilitate understanding of the objectives, features and advantages of the present disclosure, specific embodiments of the present disclosure are presented below.

[0026] In order to more clearly describe the embodiments of the present disclosure or the technical solutions of the prior art, the drawings necessary for describing the embodiments or the prior art will be briefly described. The drawings described below are only shown in the embodiments of the present disclosure, and it is clear that those skilled in the art can obtain drawings of other embodiments based on these drawings without any creative efforts. [Brief explanation of the drawings]

[0027] [Figure 1] FIG. 1 is a structural schematic diagram of a robot arm according to an embodiment of the present disclosure. [Figure 2] FIG. 1 is an equivalent schematic diagram of a connection structure between links in a robot arm according to an embodiment of the present disclosure. [Figure 3] 1 is a flowchart of a method for identifying an external force applied to a robot arm according to an embodiment of the present disclosure. [Figure 4] 1 is a flowchart of a method for determining a motion state parameter of each link in one embodiment of the present disclosure. [Figure 5] FIG. 2 is a schematic diagram of a coordinate system of a link in one embodiment of the present disclosure. [Figure 6] FIG. 10 is a schematic diagram illustrating an external force applied to a link in one embodiment of the present disclosure. [Figure 7] FIG. 1 is a block diagram illustrating a structure of a robot arm according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0028] Hereinafter, the embodiments of the technical solution of the present disclosure will be described in detail with reference to the drawings. The following embodiments are only for more clearly describing the technical solution of the present disclosure, and therefore are only examples, and do not limit the protection scope of the present disclosure.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The terms used herein are for the purpose of describing particular embodiments only and are not intended to be limiting of the disclosure. The terms "comprises," "having," and any variations thereof in the specification, claims, and description of the drawings of this disclosure are intended to cover a non-exclusive inclusion.

[0030] In describing the embodiments of the present disclosure, terms such as "first," "second," etc. are used only to distinguish between different objects and should not be understood as indicating or implying relative importance, or the number, particular order, or hierarchical relationship of the technical features shown. In describing the embodiments of the present disclosure, "plurality" means two or more (including two), unless otherwise specified.

[0031] In describing the embodiments of the present disclosure, unless otherwise defined, terms such as "attached," "coupled," "connected," and "fixed" should be understood in a broad sense, and may mean, for example, a fixed connection, a detachable connection, an integrated connection, a mechanical connection, an electrical connection, a direct connection, an indirect connection via an intermediary, a communication between two elements, or an interactive relationship between two elements. Those skilled in the art will be able to understand the specific meanings of the above terms in the embodiments of the present disclosure depending on the specific circumstances.

[0032] Currently, robotic arms are widely used in various fields, such as industrial production and logistics and transportation. Due to complex external environments, impacts from external forces are unavoidable during the operation of a robotic arm. Therefore, accurately detecting external forces applied to a robotic arm is extremely important. However, the applicant has discovered that most current robotic arms only have position sensing capabilities and are unable to determine the magnitude, direction, and location of external forces applied to the robotic arm. Even if a single-degree-of-freedom (DOF) force / torque sensor is attached to the joint of a robotic arm, or a six-degree-of-freedom (6-DOF) force / torque sensor is attached to the end effector of a robotic arm, it can only comprehensively determine the external forces applied to the entire robotic arm, but it cannot accurately determine the external forces applied to each link of the robotic arm and the specific locations where the forces are applied.

[0033] To address the problem of being unable to accurately determine external forces applied to a robot arm, the applicant has conducted research and designed a method for determining external forces applied to a robot arm.The robot arm includes a plurality of links and a plurality of joints connected in series, the links are connected via joints, and six-degree-of-freedom (6-DOF) force / torque sensors are provided at the joints on both ends of at least some of the links, and the 6-DOF force / torque sensors are configured to detect the forces and torques applied to the corresponding joints. The method for specifying an external force applied to a robot arm includes the steps of: acquiring inertia characteristic parameters including the mass, center of gravity, and rotational inertia of each link; specifying motion state parameters including the angular velocity, angular acceleration, and linear acceleration of each link; specifying the inertial force and inertial torque at the center of gravity of a target link based on the motion state parameters and inertia characteristic parameters of each link; acquiring forces and torques between both ends of the target link and corresponding joints using a six-degree-of-freedom force / torque sensor; and specifying the external force applied to the target link based on the inertial force and inertial torque at the center of gravity of the target link and the forces and torques between both ends of the target link and corresponding joints.

[0034] By installing 6-degree-of-freedom force / torque sensors at the joints at both ends of the links of the robot arm, it is possible to detect the force acting in each direction at each joint of the robot arm, and to identify the magnitude, direction, and position of the external force applied to each link of the robot arm, thereby making the calculation of the external force applied to the robot arm more accurate.

[0035] The present invention will be described in detail below with reference to the embodiments. The method for identifying an external force applied to a robot arm disclosed in the embodiments of the present disclosure can be applied to, but is not limited to, robot arms in fields such as industrial manufacturing and logistics transportation.

[0036] FIG. 1 is a schematic structural diagram of a robot arm according to an embodiment of the present disclosure. The robot arm 10 includes a plurality of sequentially connected links 11, a plurality of joints 12, and an operating unit 13. The links 11 are connected to each other via the joints 12. The links 11 are also pivotally connected to each other via the joints 12. In one embodiment, some of the links 11 may be connected to each other via the joints 11 in a linear drive manner. The operating unit 13 may be a member for realizing a corresponding function of the robot arm, such as a gripper. Referring to FIG. 2, the joints 12 at both ends of at least some of the links 11 are provided with 6-DOF force / torque sensors 14, which are configured to detect the force and torque applied to the corresponding joint. For example, in some scenarios, each link of the robot arm may be affected by an external force. That is, if it is necessary to calculate the external force applied to each link, a 6-DOF force / torque sensor may be provided at each joint at both ends of each link. In some other scenarios, it may be necessary to calculate an external force applied to some links of a robot arm, or multiple links may be considered as a whole when calculating an external force to be applied, and in this case, 6-DOF force / torque sensors may be provided at joints at both ends of some links. That is, which links to provide 6-DOF force / torque sensors at both ends can be determined according to actual needs, and the present disclosure is not limited thereto.

[0037] The six-degree-of-freedom force / torque sensor 14 detects the force and torque (F x ,F y ,F z ,T x ,T y ,T z ) can be detected.

[0038] As can be understood, in the embodiment of the present disclosure, the number of links 11 and joints 12 of the robot arm 10 can be set as needed. For example, if the robot arm 10 is a seven-axis robot, it may include seven joints 12 and a corresponding number of links 11.

[0039] In one embodiment, the 6-DOF force / torque sensor 14 may be provided at the input end of the joint 12. In another embodiment, the 6-DOF force / torque sensor 14 may be provided at the output end of the joint 12. As will be understood by those skilled in the art, the difference between providing the 6-DOF force / torque sensor 14 at the input or output end of the joint is that the specific method for calculating the external force applied to the robot arm needs to take into account the magnification and reduction of force / torque in some directions due to the reducer, i.e., the magnitude of the torque value in some directions may differ during the process of calculating the external force applied to the robot arm. Also, although the reference coordinate systems used in the subsequent data processing and calculation process of the external force applied to the robot arm are different, the calculation method for the external force applied to the robot arm is essentially the same. The method disclosed herein allows for both of these configuration methods.

[0040] In one embodiment, a 6-DOF force / torque sensor 14 may be provided at each joint 12. In another embodiment, a 6-DOF force / torque sensor 14 may be provided at joints at both ends of some target links that need to detect external forces as needed, and 6-DOF force / torque sensors may not be provided at all joints, and may be provided specifically according to actual needs.

[0041] Referring to Figure 3, this figure is a flowchart of a method for identifying an external force applied to a robot arm in one embodiment of the present disclosure. In this embodiment, the method for identifying an external force applied to a robot arm will be described as being applied to the robot arm shown in Figures 1 and 2 as an example. The method includes the following steps S1 to S5.

[0042] In S1, the inertia characteristic parameters including the mass, center of gravity, and rotational inertia of each link are obtained.

[0043] In one embodiment, the robot having the robot arm 10 further includes a controller (not shown), and data for describing the structure of the robot, such as a Unified Robot Description Format (URDF) file, is stored in the controller. URDF is a format for describing the structure of a robot based on XML specifications. From the perspective of kinematics, a robot is generally modeled as a structure composed of links and joints. A link is a rigid body having a mass attribute, and a joint is a structure that connects two rigid bodies and restricts the relative motion between them. Links are connected in sequence by joints to form multiple kinematic chains (i.e., robot models obtained by modeling). One URDF file is configured to describe the relative relationships between a series of joints and links of a robot, inertia attributes, etc.

[0044] The inertial property parameters of each link may be obtained from a URDF file.

[0045] In another embodiment, the inertial characteristic parameters of each link may be obtained from another external storage device.

[0046] In S2, the motion state parameters including the angular velocity, angular acceleration and linear acceleration of each link are identified.

[0047] In one embodiment, each link may be provided with an inertial measurement unit (IMU), which is configured to measure the angular velocity, angular acceleration, and linear acceleration of the corresponding link, and determining the motion state parameters of each link includes obtaining the motion state parameters of each link from the inertial measurement unit.

[0048] In another embodiment, as shown in FIG. 4, identifying the motion state parameters of each link may include the following steps S201 to S202.

[0049] In S201, connection parameters and angle information of each joint are acquired. The connection parameters are parameters that indicate the spatial positional relationship between two adjacent links, and the angle information includes joint angular position, joint angular velocity, and joint angular acceleration.

[0050] In one embodiment, the connection parameters of each joint may be obtained from the above-mentioned URDF file or from another external storage device, and the present disclosure does not limit the method of obtaining the connection parameters.

[0051] In one embodiment, the connection parameters may be standard Denavit-Hartenberg (D-H) parameters. The D-H parameters set one coordinate system for each link of the robot and describe the spatial relationship between two adjacent links using a 4x4 homogeneous transformation matrix. The D-H parameters specifically include the following four parameters: link length, link twist angle, link offset distance, and joint angle. The D-H parameters are conventional technology and will not be described in detail here.

[0052] In another embodiment, the connection parameters may be improved DH parameters, which are prior art and will not be described in detail here.

[0053] In one embodiment, the joints 12 are further provided with joint position sensors (not shown), which are configured to detect angle information such as the joint angular position, joint angular velocity, and joint angular acceleration of the corresponding joints. For example, the joint position sensors may be rotary encoders. The angle information of each joint may be obtained from the joint position sensors.

[0054] In S202, the motion state parameters of each link are determined according to the robot dynamics principles based on the inertia characteristic parameters of each link, the connection parameters of each joint, and the angle information of each joint.

[0055] Robot dynamics principles include, but are not limited to, the Lagrange Method, the Recursive Newton-Euler Algorithm, and the like.

[0056] As can be seen from the above description, there are various methods for determining the motion state parameters of each link according to the principles of robot dynamics, and in this embodiment, the robot dynamics principle is described as being the recursive Newton-Euler algorithm. In this embodiment, the forward inductive equations of the recursive Newton-Euler algorithm are used to determine the motion state parameters, such as the angular velocity, angular acceleration, and linear acceleration, of each link based on the inertial characteristic parameters of each link, the connection parameters of each joint, and the angle information of each joint.

[0057] For example, the motion coordinate system of each link shown in Figure 5 can be established. The first coordinate system is established on the robot base with O as the origin, and the second coordinate system is established on the robot base with O as the origin. i―1 A second coordinate system is established at joint i corresponding to the first end of link i with Oi as the origin, and a third coordinate system is established at joint i+1 corresponding to the second end of link i with Oi as the origin.The following forward recursive equations in the recursive Newton-Euler equations can be established to determine the motion state parameters of link i based on the motion state parameters of the previous link i-1.

[0058] JPEG2026504585000004.jpg24133

[0059] JPEG2026504585000005.jpg24164

[0060] JPEG2026504585000006.jpg23158

[0061] JPEG2026504585000007.jpg37161

[0062] JPEG2026504585000008.jpg12128

[0063] JPEG2026504585000009.jpg54170

[0064] The equations corresponding to the rotary joints in the above equations (1) to (5) are for the case where two links are connected to rotate via a joint. The equations corresponding to the linearly driven joints are for the case where two links are connected linearly via a joint and move linearly.

[0065] As can be understood by those skilled in the art, the recursive Newton-Euler equations may have other different transformation forms, and although not shown one by one in the embodiments of the present disclosure, none of these transformation forms departs from the principles and spirit of the present disclosure.

[0066] In S3, the inertial force and inertial torque at the center of gravity of the target link are determined based on the motion state parameters and inertial characteristic parameters of each link.

[0067] Specifically, in one embodiment, a backward recursion of the recursive Newton-Euler equations is used to determine the inertial forces and torques at the center of gravity of the target link based on the motion state parameters and inertial characteristic parameters of each link.

[0068] JPEG2026504585000010.jpg53170

[0069] JPEG2026504585000011.jpg45170

[0070] As can be understood by those skilled in the art, the above formulas (1) to (9) are expressions when the third coordinate system is used as the reference coordinate system. When the second coordinate system or another coordinate system is used as the reference coordinate system, the above formulas are subjected to a corresponding coordinate system transformation, and the principle and spirit thereof are substantially the same.

[0071] In S4, the force and torque between both ends of the target link and the corresponding joint are acquired by a 6-DOF force / torque sensor.

[0072] Specifically, the force and torque between each end of the target link and the corresponding joint are obtained by using 6-DOF force / torque sensors provided at joints located at both ends of the target link. It should be understood that the measurements of the force / torque sensors provided at the joints can indicate actual measurements of the acting force / torque between two links adjacent to the joint. Therefore, in this step, measurements of the forces applied to the target link by the links before and after the target link can be obtained.

[0073] In S5, an external force to be applied to the target link is identified based on the inertial force and inertial torque at the center of gravity of the target link and the forces and torques between both ends of the target link and the corresponding joints.

[0074] In one embodiment, the step of identifying an external force to be applied to the target link based on an inertial force and an inertial torque at the center of gravity of the target link and forces and torques between both ends of the target link and the corresponding joints includes: The method includes determining a first difference between an inertial force at the center of gravity of the target link and a force between both ends of the target link and the corresponding joint, and determining a magnitude and a direction of an external force to be applied to the target link based on the first difference. The first difference is a vector difference.

[0075] JPEG2026504585000012.jpg45170

[0076] JPEG2026504585000013.jpg28170

[0077] JPEG2026504585000014.jpg22170

[0078] Furthermore, after determining the magnitude and direction of the external force, an embodiment of the present disclosure can further calculate a specific position of the external force applied to each target link. In one embodiment, the step of determining the specific position of the external force applied to the target link includes the steps of determining a net torque of the target link at a reference point based on a second difference between the torque between both ends of the target link and the corresponding joint and an inertial torque at the center of gravity of the target link, and determining a position of the external force applied to the target link relative to the reference point based on the net torque of the target link at the reference point and the magnitude and direction of the external force applied to the target link.

[0079] The reference point may be any point in the space where the robot arm is located, and may be selected according to actual needs. In one embodiment, the position of the reference point may be the origin of a joint coordinate system corresponding to a joint at one end of the target link. In another embodiment, the position of the reference point may be the center of gravity of the target link.

[0080] JPEG2026504585000015.jpg53170

[0081] Furthermore, before determining the position of the external force applied to the target link based on the net torque of the target link at the reference point and the magnitude and direction of the external force applied to the target link, the method further includes the steps of determining whether the magnitude of the external force is greater than a predetermined first threshold and determining whether the value of the net torque is greater than a predetermined second threshold, determining that no external force is being applied to the target link if the magnitude of the external force is less than the first threshold, and determining that the external force applied to the target link is located at the reference point if the magnitude of the external force is greater than or equal to the first threshold and the value of the net torque is less than the second threshold.If the magnitude of the external force is greater than or equal to the first threshold and the value of the net torque is greater than the second threshold, determining the position of the external force applied to the target link relative to the reference point based on the net torque of the target link at the reference point and the magnitude and direction of the external force applied to the target link using the above equations (12) and (13).

[0082] The method for identifying an external force applied to a robot arm in an embodiment of the present disclosure detects the force and torque in each direction acting on the joint using a 6-degree-of-freedom force / torque sensor provided at each joint, and combines this with the calculated inertial force and inertial torque at the center of gravity of the target link to identify the magnitude, direction, and position of the external force applied to each distributed target link, thereby making it possible to more accurately detect the external force applied to the robot arm.

[0083] It should be understood that although the steps in the flowcharts according to the above-described embodiments are displayed in the order indicated by the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated otherwise in this specification, the execution of these steps is not limited to a strict order, and these steps may be executed in other orders. Furthermore, at least some of the steps in the flowcharts according to the above-described embodiments may include multiple steps or multiple stages, and these steps or stages may not necessarily be executed at the same time but may be executed at different times. The order in which these steps or stages are executed is also not necessarily sequential, but may be executed in order or alternately with other steps or at least some of the steps or stages in other steps.

[0084] Based on a similar inventive concept, referring to FIGS. 1 and 7 , another embodiment of the present disclosure further provides a robot arm. The robot arm 10 includes a plurality of links, a plurality of joints, and an operating unit. The links are connected via joints. The links may be connected in a rotational manner via the joints, and some links may be connected in a linear drive manner via the joints. The operating unit may be a member for realizing a corresponding function of the robot arm, such as a gripper. Joints at both ends of at least some of the links are provided with six-degree-of-freedom force / torque sensors for detecting forces and torques applied to the corresponding joints. The robot arm 10 further includes at least one memory 15 and at least one processor 16. At least one memory 15 stores a computer program, and when the computer program is executed by at least one processor 16, the following steps are performed: acquiring inertial characteristic parameters including the mass, center of gravity, and rotational inertia of each link; determining motion state parameters including the angular velocity, angular acceleration, and linear acceleration of each link; determining the inertial force and inertial torque at the center of gravity of the target link based on the motion state parameters and inertial characteristic parameters of each link; acquiring forces and torques between both ends of the target link and the corresponding joints using a 6-DOF force / torque sensor; determining an external force to be applied to the target link based on the inertial force and inertial torque at the center of gravity of the target link and the forces and torques between both ends of the target link and the corresponding joints; and steps of a method for determining an external force to be applied to a robot arm.

[0085] In one embodiment, the step of identifying the motion state parameters of each link includes the steps of acquiring connection parameters of each joint and angle information of each joint, and identifying the motion state parameters of each link according to robot dynamics principles based on the inertia characteristic parameters of each link, the connection parameters of each joint, and the angle information of each joint, wherein the connection parameters are parameters indicating the spatial positional relationship between two adjacent links, and the angle information includes joint angular positions, joint angular velocities, and joint angular accelerations.

[0086] In another embodiment, each link of the robot arm is provided with an inertial measurement unit configured to measure the angular velocity, angular acceleration, and linear acceleration of the corresponding link, and the step of determining the motion state parameters of each link includes obtaining the motion state parameters of each link from the inertial measurement unit.

[0087] In one embodiment, the step of determining the inertial force and inertial torque at the center of gravity of the target link based on the motion state parameters and inertial characteristic parameters of each link includes determining the inertial force and inertial torque at the center of gravity of the target link based on the motion state parameters and inertial characteristic parameters of each link using a backward recursive equation of the recursive Newton-Euler equations. The specific determination method may be referred to in the above embodiment, and will not be described again here.

[0088] In one embodiment, the step of determining an external force to be applied to the target link based on an inertial force and an inertial torque at the center of gravity of the target link and forces and torques between both ends of the target link and the corresponding joints includes determining a first difference between the inertial force at the center of gravity of the target link and the forces between both ends of the target link and the corresponding joints, and determining a magnitude and a direction of the external force to be applied to the target link based on the first difference, where the first difference is a vector difference.

[0089] In one embodiment, the method further comprises the steps of: determining a net torque of the target link at the reference point based on a second difference between the torque between both ends of the target link and the corresponding joint and the inertial torque at the center of gravity of the target link; and determining a position of the external force applied to the target link relative to the reference point based on the net torque of the target link at the reference point and the magnitude and direction of the external force applied to the target link.

[0090] In one embodiment, before determining the location of the external force applied to the target link based on the net torque of the target link at the reference point and the magnitude and direction of the external force applied to the target link, the following steps are further performed: determining whether the magnitude of the external force is greater than a predetermined first threshold and determining whether the value of the net torque is greater than a predetermined second threshold; determining that no external force is being applied to the target link if the magnitude of the external force is less than the first threshold; and determining that the external force applied to the target link is located at the reference point if the magnitude of the external force is greater than or equal to the first threshold and the value of the net torque is less than the second threshold. If the magnitude of the external force is greater than or equal to the first threshold and the value of the net torque is greater than the second threshold, the location of the external force applied to the target link relative to the reference point is determined based on the following equation:

[0091] JPEG2026504585000016.jpg41170

[0092] Another aspect of the present disclosure further provides a non-transitory computer-readable recording medium having stored thereon computer program commands that, when executed by a processor, perform the method for determining an external force applied to a robot arm in one or more of the above embodiments.

[0093] As will be understood by those skilled in the art, all or part of the processes in the methods of the above embodiments can be achieved by controlling associated hardware through computer program commands. The computer program commands can be stored in a non-volatile computer-readable storage medium, and the processes of the above embodiments can be implemented when the computer program commands are executed. Furthermore, any reference to memory, database, or other medium used in the embodiments provided in this disclosure can include at least one of non-volatile memory and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetoresistive random access memory (MRAM), ferroelectric random access memory (FRAM®), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM may be in various forms such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM).

[0094] The technical features of the above embodiments can be combined in any way, and for the sake of brevity, not all possible combinations of the technical features in the above embodiments are described, but as long as there is no contradiction in the combination of these technical features, they should be considered within the scope described in this specification.

[0095] The above embodiments merely illustrate some embodiments of the present disclosure, and although the description is relatively specific and detailed, it should not be construed as a limitation on the patent scope of the present disclosure. It should be noted that a person skilled in the art can make some modifications and improvements without departing from the concept of the present disclosure, and all of them will fall within the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure shall be defined by the appended claims.

Claims

1. A method for identifying an external force applied to a robot arm, comprising: the robot arm includes a plurality of links and a plurality of joints connected in series, the links being connected to each other via the joints, and the joints at both ends of at least some of the links are provided with six-degree-of-freedom force / torque sensors, i.e., 6-DOF force / torque sensors, which are configured to detect forces and torques applied to the corresponding joints; The method comprises: obtaining inertial characteristic parameters including mass, center of gravity, and rotational inertia of each said link; determining motion state parameters including angular velocity, angular acceleration, and linear acceleration of each said link; determining an inertial force and an inertial torque at the center of gravity of a target link based on the motion state parameters and the inertial characteristic parameters of each link; acquiring forces and torques between both ends of the target link and the corresponding joints by the 6-DOF force / torque sensor; and determining an external force to be applied to the target link based on inertial forces and inertial torques at the center of gravity of the target link and forces and torques between both ends of the target link and the corresponding joints.

2. The step of identifying a motion state parameter of each of the links includes: acquiring connection parameters of each of the joints and angle information of each of the joints, the connection parameters being parameters indicating a spatial positional relationship between two adjacent links, and the angle information including a joint angular position, a joint angular velocity, and a joint angular acceleration; determining a motion state parameter of each of the links according to a robot dynamics principle based on the inertial characteristic parameter of each of the links, the connection parameter of each joint, and the angle information of each joint.

3. each link is provided with an inertial measurement unit configured to measure the angular velocity, angular acceleration, and linear acceleration of the corresponding link; The step of identifying a motion state parameter of each of the links includes:

2. The method of claim 1, further comprising obtaining motion state parameters of each of the links from the inertial measurement unit.

4. The step of determining an inertial force and an inertial torque at the center of gravity of the target link based on the motion state parameters and the inertial characteristic parameters of each of the links includes:

2. The method of claim 1, comprising determining inertial forces and inertial torques at the center of gravity of the target link based on the motion state parameters and the inertial characteristic parameters of each link using a backward recursion of the recursive Newton-Euler equations.

5. The step of specifying an external force to be applied to the target link based on an inertial force and an inertial torque at the center of gravity of the target link and forces and torques between both ends of the target link and the corresponding joints includes: determining a first difference between an inertial force at the center of gravity of the target link and a force between both ends of the target link and the corresponding joint; and determining a magnitude and a direction of an external force applied to the target link based on the first difference.

6. Further, determining a net torque of the target link at a reference point based on a second difference between a torque between both ends of the target link and the corresponding joint and an inertial torque at the center of gravity of the target link; and determining a position of the external force applied to the target link relative to the reference point based on a net torque of the target link at the reference point and a magnitude and direction of the external force applied to the target link.

7. before determining the position of the external force applied to the target link based on the net torque of the target link at the reference point and the magnitude and direction of the external force applied to the target link, determining whether the magnitude of the external force is greater than a predetermined first threshold value, and determining whether the value of the net torque is greater than a predetermined second threshold value; determining that no external force is being applied to the target link when the magnitude of the external force is smaller than the first threshold value; and determining that the external force applied to the target link is located at the reference point when the magnitude of the external force is equal to or greater than the first threshold and the value of the net torque is less than the second threshold.

8.

9. A robotic arm, a plurality of sequentially connected links; a plurality of joints connected to the joint; a plurality of six-degree-of-freedom force / torque sensors (6-DOF force / torque sensors) provided at the joints at both ends of at least some of the links and configured to detect forces and torques applied to the corresponding joints; at least one memory for storing computer program commands; at least one processor for executing said computer program commands; When the computer program instructions are executed by the at least one processor, obtaining inertial characteristic parameters including mass, center of gravity, and rotational inertia of each said link; determining motion state parameters including angular velocity, angular acceleration, and linear acceleration of each said link; determining an inertial force and an inertial torque at the center of gravity of a target link based on the motion state parameters and the inertial characteristic parameters of each link; acquiring forces and torques between both ends of the target link and the corresponding joints by the 6-DOF force / torque sensor; and identifying an external force to be applied to the target link based on an inertial force and an inertial torque at the center of gravity of the target link and forces and torques between both ends of the target link and the corresponding joints.

10. The step of identifying a motion state parameter of each of the links includes: acquiring connection parameters of each of the joints and angle information of each of the joints, the connection parameters being parameters indicating a spatial positional relationship between two adjacent links, and the angle information including a joint angular position, a joint angular velocity, and a joint angular acceleration; and determining a motion state parameter of each of the links according to a robot dynamics principle based on the inertial characteristic parameter of each of the links, the connection parameter of each joint, and the angle information of each joint.

11. each link is provided with an inertial measurement unit configured to measure the angular velocity, angular acceleration, and linear acceleration of the corresponding link; The step of identifying a motion state parameter of each of the links includes:

10. The robot arm of claim 9, further comprising acquiring motion state parameters of each of the links from the inertial measurement unit.

12. The step of determining an inertial force and an inertial torque at the center of gravity of the target link based on the motion state parameters and the inertial characteristic parameters of each of the links includes:

10. The robot arm of claim 9, further comprising: determining an inertial force and an inertial torque at the center of gravity of the target link based on the motion state parameters and the inertial characteristic parameters of each of the links using a backward recursion of the recursive Newton-Euler equations.

13. The step of specifying an external force to be applied to the target link based on an inertial force and an inertial torque at the center of gravity of the target link and forces and torques between both ends of the target link and the corresponding joints includes: determining a first difference between an inertial force at the center of gravity of the target link and a force between both ends of the target link and the corresponding joint; and determining a magnitude and a direction of an external force to be applied to the target link based on the first difference.

14. Further, determining a net torque of the target link at a reference point based on a second difference between a torque between both ends of the target link and the corresponding joint and an inertial torque at the center of gravity of the target link; 14. The robot arm of claim 13, further comprising the step of: determining a position of an external force applied to the target link relative to the reference point based on a net torque of the target link at the reference point and a magnitude and direction of the external force applied to the target link.

15. before determining the position of the external force applied to the target link based on the net torque of the target link at the reference point and the magnitude and direction of the external force applied to the target link, determining whether the magnitude of the external force is greater than a predetermined first threshold value, and determining whether the value of the net torque is greater than a predetermined second threshold value; determining that no external force is being applied to the target link when the magnitude of the external force is smaller than the first threshold value; 15. The robot arm of claim 14, further comprising: a step of determining that the external force applied to the target link is located at the reference point when the magnitude of the external force is equal to or greater than the first threshold value and the value of the net torque is smaller than the second threshold value.

16.

17. A non-transitory computer-readable recording medium storing a computer program, When the computer program is executed by at least one processor, obtaining inertial characteristic parameters including mass, center of gravity, and rotational inertia of each link; determining motion state parameters including angular velocity, angular acceleration, and linear acceleration of each said link; determining an inertial force and an inertial torque at the center of gravity of a target link based on the motion state parameters and the inertial characteristic parameters of each link; Obtaining forces and torques between both ends of the target link and corresponding joints by a 6-DOF force / torque sensor; and determining an external force to be applied to the target link based on inertial forces and inertial torques at the center of gravity of the target link and forces and torques between both ends of the target link and the corresponding joints.

18. The step of identifying a motion state parameter of each of the links includes: acquiring connection parameters of each of the joints and angle information of each of the joints; determining a motion state parameter of each of the links according to a robot dynamics principle based on the inertial characteristic parameter of each of the links, the connection parameter of each of the joints, and the angle information of each of the joints; 18. The non-transitory computer-readable storage medium of claim 17, wherein the connection parameters are parameters indicating a spatial positional relationship between two adjacent links, and the angle information includes a joint angular position, a joint angular velocity, and a joint angular acceleration.

19. The step of specifying an external force to be applied to the target link based on an inertial force and an inertial torque at the center of gravity of the target link and forces and torques between both ends of the target link and the corresponding joints includes: determining a first difference between an inertial force at the center of gravity of the target link and a force between both ends of the target link and the corresponding joint; and determining a magnitude and a direction of an external force to be applied to the target link based on the first difference.

20. The computer program when executed by at least one processor further comprises: determining a net torque of the target link at a reference point based on a second difference between a torque between both ends of the target link and the corresponding joint and an inertial torque at the center of gravity of the target link; and determining a position of the external force applied to the target link relative to the reference point based on a net torque of the target link at the reference point and a magnitude and direction of the external force applied to the target link.

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