Method for determining external force on mechanical arm, mechanical arm and storage medium

Abstract

This application discloses a method for determining the external force acting on a robotic arm. The robotic arm includes multiple connecting rods and multiple joints. At least some of the connecting rods have six-degree-of-freedom force and torque sensors installed in the joints at both ends to sense the forces and torques acting on the corresponding joints. The method includes: acquiring the inertial property parameters of each connecting rod; determining the motion state parameters of each connecting rod; determining the inertial force and inertial torque of the target connecting rod at its center of mass based on the motion state parameters and inertial property parameters; acquiring the forces and torques between the two ends of the target connecting rod and the corresponding joints using the force and torque sensors; and determining the external force acting on the target connecting rod based on the inertial force and inertial torque of the target connecting rod at its center of mass and the forces and torques between the two ends of the target connecting rod and the corresponding joints. This application also provides a robotic arm and a storage medium. This application can accurately detect the external forces acting on each connecting rod of the robotic arm.

Description

Technical Field

[0001] This application relates to the field of robotics, specifically to a method for determining the external forces acting on a robotic arm, the robotic arm itself, and a storage medium. Background Technology

[0002] Currently, robotic arms are widely used in various fields such as industrial production and logistics transportation. Because robotic arms face complex external environments, they inevitably encounter collisions during operation. If the external forces acting on the robotic arm cannot be accurately detected, it will be unable to react appropriately to collisions and other external forces, thus affecting its operation. Therefore, accurately detecting the external forces acting on a robotic arm is crucial. Summary of the Invention

[0003] In view of the above problems, this application provides a method for determining the external force on a robotic arm, a robotic arm, and a computer-readable storage medium, which can accurately detect the external force on each connecting rod of the robotic arm.

[0004] In a first aspect, this application provides a method for determining the external forces acting on a robotic arm. The robotic arm includes a plurality of sequentially connected connecting rods and a plurality of joints. The connecting rods are connected to each other via the joints. At least some of the connecting rods have six-degree-of-freedom force and torque sensors installed in the joints at both ends. The six-degree-of-freedom force and torque sensors are used to sense the forces and torques acting on the corresponding joints. The method includes: acquiring inertial property parameters of each connecting rod, wherein the inertial property parameters include the mass, center of mass, and moment of inertia of the connecting rod; and determining the motion of each connecting rod. The motion state parameters include the angular velocity, angular acceleration, and linear acceleration of each connecting rod; based on the motion state parameters of each connecting rod and the inertial property parameters, the inertial force and inertial torque of the target connecting rod at its center of mass are determined; the forces and torques between the two ends of the target connecting rod and the corresponding joints are acquired through the six-degree-of-freedom force and torque sensors; and the external forces acting on the target connecting rod are determined based on the inertial force and inertial torque of the target connecting rod at its center of mass and the forces and torques between the two ends of the target connecting rod and the corresponding joints.

[0005] In some embodiments, determining the motion state parameters of each of the connecting rods includes:

[0006] Obtain the connection parameters and angle information of each joint, wherein the connection parameters are parameters representing the spatial positional relationship between two adjacent connecting rods, and the angle information of each joint includes joint angular position, joint angular velocity, and joint angular acceleration; and

[0007] Based on the inertial property parameters of each connecting rod, the connection parameters of each joint, and the angle information of each joint, the motion state parameters of each connecting rod are determined according to the principles of robot dynamics.

[0008] In some embodiments, each connecting rod is provided with an inertial measurement unit for measuring the angular velocity, angular acceleration and linear acceleration of the corresponding connecting rod. Determining the motion parameters of each connecting rod includes obtaining the motion state parameters of each connecting rod from the inertial measurement unit.

[0009] In some implementations, determining the inertial force and moment of the target connecting rod at its center of mass based on the motion state parameters and inertial property parameters of each connecting rod includes: determining the inertial force and moment of the target connecting rod at its center of mass using the backward recursive equations in the iterative Newton-Euler equations, based on the motion state parameters and inertial property parameters of each connecting rod.

[0010] In some embodiments, determining the external force on the target connecting rod based on the inertial force and inertial torque of the target connecting rod at its center of mass and the forces and torques between the two ends of the target connecting rod and the corresponding joints includes: determining a first difference between the inertial force of the target connecting rod at its center of mass and the forces between the two ends of the target connecting rod and the corresponding joints, and determining the first difference as the magnitude and direction of the external force on the target connecting rod.

[0011] In some embodiments, the method further includes: determining a net torque at a reference point of the target connecting rod based on a second difference between the torque between the two ends of the target connecting rod and the corresponding joint and the inertial torque of the target connecting rod at the center of mass; and determining the position of the external force on the target connecting rod relative to the reference point based on the net torque at the reference point of the target connecting rod and the magnitude and direction of the external force on the target connecting rod.

[0012] In some embodiments, before determining the position of the external force on the target connecting rod relative to the reference point based on the net torque at the reference point of the target connecting rod and the magnitude and direction of the external force on the target connecting rod, the method further includes:

[0013] Determine whether the magnitude of the external force is greater than a preset first threshold, and determine whether the value of the net torque is greater than a preset second threshold;

[0014] If the magnitude of the external force is less than the first threshold, then it is determined that the target connecting rod is not subject to external force; and

[0015] 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, then it is determined that the external force on the target connecting rod is located at the reference point.

[0016] In some implementations, 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 on the target connecting rod relative to the reference point is determined according to the following formula:

[0017]

[0018]

[0019] Where, r mag r is the shortest distance of the line of action of the external force acting on the target connecting rod. vec M is the shortest vector from the position of the reference point to the line of action of the external force on the target connecting rod, F is the net torque value, and F is the magnitude and direction of the external force on the target connecting rod.

[0020] Secondly, this application provides a robotic arm, comprising: a plurality of sequentially connected connecting rods; a plurality of joints, wherein the connecting rods are rotatably connected via the joints; a plurality of six-degree-of-freedom force and torque sensors disposed in at least some of the joints at both ends of the connecting rods, the six-degree-of-freedom force and torque sensors being used to sense forces and torques acting on corresponding joints; and at least one memory and at least one processor. The at least one memory stores computer program instructions, which, when executed by the at least one processor, perform the method for determining the external forces acting on the robotic arm as described in any of the preceding embodiments.

[0021] Thirdly, this application provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the method for determining the external force on the robotic arm as described in any of the preceding embodiments.

[0022] By using six-degree-of-freedom force and torque sensors in the joints at both ends of the connecting rod, the joints of the robotic arm can sense forces and torques in various directions. Combined with the inertial property parameters of the connecting rod, the magnitude, direction, and position of the external force on the target connecting rod can be determined. This allows for the detection of the external forces on each target connecting rod of the robotic arm, making the detection of external forces on the entire robotic arm more accurate.

[0023] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of this application or the conventional technology, the drawings used in the description of the embodiments or the conventional technology will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the disclosed drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of the structure of the robotic arm in one embodiment of this application.

[0026] Figure 2 This is an equivalent schematic diagram of the connection structure between two connecting rods in a robotic arm according to one embodiment of this application.

[0027] Figure 3 This is a flowchart of a method for determining the external force on a robotic arm in one embodiment of this application.

[0028] Figure 4 This is a flowchart illustrating a method for determining the motion parameters of each connecting rod in one embodiment of this application.

[0029] Figure 5 This is a schematic diagram of the coordinate system of the connecting rod in one embodiment of this application.

[0030] Figure 6 This is a schematic diagram showing the force on the connecting rod in one embodiment of this application.

[0031] Figure 7 This is a schematic diagram of the structural frame of the robotic arm in one embodiment of this application. Detailed Implementation

[0032] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0033] 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 application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings, are intended to cover non-exclusive inclusion.

[0034] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more (including two), unless otherwise explicitly defined.

[0035] In the description of the embodiments of this application, unless otherwise defined, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0036] Currently, robotic arms are widely used in various fields such as industrial manufacturing and logistics transportation. Because robotic arms face complex environments, they are frequently affected by external forces, impacting their operation. Therefore, detecting the external forces acting on the robotic arm so that it can react accordingly is crucial. However, the applicant notes that most robotic arms currently only have position sensing capabilities and cannot determine the magnitude, direction, and location of the external forces acting on them. Even with a single degree of freedom (DOF) force and torque sensor installed on the joints of the robotic arm, or a six-DOF force and torque sensor installed at the end effector, only a general determination of the overall external forces acting on the robotic arm can be made; the precise forces acting on each connecting link and their specific locations cannot be determined.

[0037] To address the problem of inaccurately determining the external forces acting on a robotic arm, the applicant has developed a method for determining these forces. The robotic arm comprises multiple sequentially connected connecting rods and multiple joints, with the connecting rods connected via the joints. At least some of the connecting rods have six-degree-of-freedom force and torque sensors installed in the joints at both ends. These sensors are used to sense the forces and torques acting on the corresponding joints. The method for determining the external force on the robotic arm includes: acquiring the inertial property parameters of each connecting rod, wherein the inertial property parameters include the mass, center of mass, and moment of inertia of the connecting rod; determining the motion state parameters of each connecting rod, wherein the motion state parameters include the angular velocity, angular acceleration, and linear acceleration of each connecting rod; determining the inertial force and inertial torque of the target connecting rod at its center of mass based on the motion state parameters and the inertial property parameters of each connecting rod; acquiring the force and torque between the two ends of the target connecting rod and the corresponding joints through the six-degree-of-freedom force and torque sensors; and determining the external force acting on the target connecting rod based on the inertial force and inertial torque of the target connecting rod at its center of mass and the force and torque between the two ends of the target connecting rod and the corresponding joints.

[0038] By installing six-degree-of-freedom force and torque sensors in the joints at both ends of the robotic arm's connecting rods, it is possible to sense the forces acting on each joint of the robotic arm in various directions, and to determine the magnitude, direction, and position of the external force acting on each connecting rod of the robotic arm, making the calculation of the external force acting on the robotic arm more accurate.

[0039] The inventive concept of this application will be described in detail below with reference to various embodiments. The method for determining the external force on a robotic arm disclosed in the various embodiments of this application can be applied to, but is not limited to, robotic arms in fields such as industrial manufacturing and logistics transportation.

[0040] like Figure 1 The diagram shown is a schematic representation of a robotic arm according to one embodiment of this application. The robotic arm 10 includes multiple connecting rods 11, multiple joints 12, and an operating part 13 connected sequentially. The connecting rods 11 are connected via the joints 12. The connecting rods 11 are rotatably connected via the joints 12. In some embodiments, some connecting rods 11 may also be connected via the joints 11 in a linear drive manner. The operating part 13 may be a gripper or other component used to realize the corresponding function of the robotic arm. Please refer to the accompanying documentation. Figure 2In this embodiment, at least some of the connecting rods 11 have six-degree-of-freedom force and torque sensors 14 installed in the joints 12 at both ends. These sensors 14 are used to sense the forces and torques acting on the corresponding joints. For example, in some scenarios, each connecting rod of the robotic arm may be affected by external forces, requiring the calculation of the external forces acting on each connecting rod. In such cases, the six-degree-of-freedom force and torque sensors can be installed in the joints at both ends of each connecting rod. In other scenarios, only a portion of the connecting rods may require calculation of the external forces acting on them, or multiple connecting rods may be considered as a whole when calculating the external forces. In such cases, the six-degree-of-freedom force and torque sensors can be installed in the joints at both ends of the portion of the connecting rods. In other words, the placement of the six-degree-of-freedom force and torque sensors at both ends of the connecting rods can be determined according to actual needs, and this application does not impose any limitations.

[0041] The six-degree-of-freedom force and torque sensor 14 is capable of sensing the forces and torques (F) acting on the joint in three directions in three-dimensional space. x ,F y ,F z ,T x ,T y ,T z ).

[0042] It is understood that in the embodiments of this application, the number of connecting rods 11 and joints 12 of the robotic arm 10 can be set as needed. For example, if the robotic arm 10 is a seven-axis robot, it may include seven joints 12 and a corresponding number of connecting rods 11.

[0043] In some embodiments, the six-DOF force and torque sensor 14 can be disposed at the input end of the joint 12. In other embodiments, the six-DOF force and torque sensor 14 can also be disposed at the output end of the joint 12. Those skilled in the art will understand that the difference between disposing the six-DOF force and torque sensor 14 at the output or input end of the joint, for the method of determining the external force acting on the robotic arm, lies in the need to consider the amplification and reduction of force / torque by the reducer in some directions. That is, the magnitude of the torque value in some directions may differ during the calculation of the external force acting on the robotic arm, and the reference coordinate system used in subsequent data processing and the calculation of the external force acting on the robotic arm may be different, but the calculation method of the external force acting on the robotic arm is essentially the same. For the method of this application, both placement methods are feasible.

[0044] In some embodiments, the six-degree-of-freedom force and torque sensor 14 may be disposed in each of the joints 12. In other embodiments, the six-degree-of-freedom force and torque sensor 14 may also be disposed in the joints at both ends of the target connecting rod that need to detect the external force, instead of disposing of the six-degree-of-freedom force and torque sensor in all joints, depending on actual needs.

[0045] Please see Figure 3 This is a flowchart illustrating a method for determining the external force acting on a robotic arm according to one embodiment of this application. This embodiment applies the method for determining the external force acting on a robotic arm to applications such as... Figure 1-2 The robotic arm shown is used as an example for illustration. The method includes the following steps S1-S5.

[0046] S1. Obtain the inertial property parameters of each of the connecting rods, wherein the inertial property parameters include the mass, center of mass, and moment of inertia of the connecting rod.

[0047] In some embodiments, the robot with the robotic arm 10 also includes a controller (not shown) that stores data describing the robot's structure, such as a Unified Robot Description Format (URDF) file. URDF is an XML-based format for describing robot structures. From a mechanics perspective, a robot is typically modeled as a structure composed of links and joints. Links are rigid bodies with mass properties, and joints are structures that connect and restrict the relative motion of two rigid bodies. Connecting links sequentially through joints forms multiple kinematic chains (i.e., the modeled robot model). A URDF file describes the relative relationships, inertial properties, etc., of a series of joints and links of the robot.

[0048] The inertial property parameters of each connecting rod can be obtained from the URDF file.

[0049] In other embodiments, the inertial property parameters of each connecting rod may also be obtained from other external storage devices.

[0050] S2. Determine the motion state parameters of each of the connecting rods, wherein the motion state parameters include the angular velocity, angular acceleration and linear acceleration of each connecting rod.

[0051] In some embodiments, each connecting rod may be equipped with an inertial measurement unit (IMU) for measuring the angular velocity, angular acceleration, and linear acceleration of the corresponding connecting rod. Determining the motion state parameters of each connecting rod includes acquiring the motion state parameters of each connecting rod from the inertial measurement unit.

[0052] In other implementations, such as Figure 4 As shown, determining the motion state parameters of each connecting rod may include the following steps S201-S202.

[0053] S201. Obtain the connection parameters of each joint and the angle information of each joint, wherein the connection parameters are parameters representing the spatial positional relationship between two adjacent connecting rods, and the angle information of each joint includes the joint angular position, the joint angular velocity, and the joint angular acceleration.

[0054] In some implementations, the connection parameters of each joint can be obtained from the aforementioned URDF file or from other external storage devices. This application does not limit the method of obtaining the connection parameters.

[0055] In some implementations, the connection parameters can be standard Denavit-Hartenberg (DH) parameters. DH parameters are defined by establishing a coordinate system for each link of the robot and then using a 4×4 homogeneous transformation matrix to describe the spatial relationship between adjacent links. Specifically, the DH parameters include the following four parameters: link length, link twist angle, link offset distance, and joint angle. DH parameters are existing technology and will not be described in detail here.

[0056] In other embodiments, the connection parameters may also be improved DH parameters. Improved DH parameters are prior art and will not be described in detail here.

[0057] In some embodiments, the joint 12 is further provided with a joint position sensor (not shown) for sensing angular information such as the joint angular position, joint angular velocity, and joint angular acceleration of the corresponding joint. For example, the joint position sensor may be a rotary encoder. The angle information of each joint may be obtained from the joint position sensor.

[0058] S202. Based on the inertial attribute parameters of each connecting rod, the connection parameters of each joint, and the angle information of each joint, determine the motion state parameters of each connecting rod according to the principles of robot dynamics.

[0059] The robot dynamics principles mentioned include, but are not limited to, the Lagrange method and the Recursive Newton-Euler Algorithm.

[0060] As described above, there are multiple ways to determine the motion state parameters of each connecting link based on the principles of robot dynamics. This embodiment uses the iterative Newton-Euler algorithm as an example to illustrate the robot dynamics principle. In this embodiment, the forward recursive equation of the iterative Newton-Euler algorithm is used to determine the motion state parameters of each connecting link, such as angular velocity, angular acceleration, and linear acceleration, based on the inertial property parameters of each connecting link, the connection parameters of each joint, and the angle information of each joint.

[0061] For example, it is possible to establish Figure 5 The motion coordinate systems of each connecting rod shown include a first coordinate system established at the robot base with O as the origin, and a second coordinate system established at O ​​as the origin. i-1 Establish a second coordinate system with its origin at joint i corresponding to the first end of connecting rod i, and establish a third coordinate system with its origin at joint i+1 corresponding to the second end of connecting rod i. Establish the following forward recursive equation in the iterative Newton-Euler equations, which can determine the motion state parameters of connecting rod i based on the motion state parameters of the previous connecting rod i-1, where:

[0062] angular velocity of connecting rod i i ω i for:

[0063]

[0064] angular acceleration of connecting rod i for:

[0065]

[0066] linear velocity of connecting rod i i v i for:

[0067]

[0068] Linear acceleration of connecting rod i for:

[0069]

[0070] Linear acceleration of connecting rod i at its center of mass

[0071]

[0072] In the above formulas (1)-(5), R i-1 For coordinate system O i-1 To coordinate system O i The rotation transformation matrix, ω i-1 Let z be the angular velocity of the preceding connecting rod i-1. i-1 Let i be the direction vector of the motion axis of joint i. and These are the joint angular velocity and joint angular acceleration of joint i, respectively. i-1 Let r be the linear velocity of the preceding connecting rod i-1. i Connect the origin O of the second coordinate system i-1 and the origin O of the third coordinate system i The vector, and These are the linear velocity and linear acceleration of connecting rod i in the linear drive joint, respectively. ci Let be the position vector of the centroid. The superscript of the vector indicates the reference coordinate system describing the vector (e.g., the superscript 'i' indicates the coordinate system at coordinates O). i (Described in the third coordinate system with the origin as the origin). It should be understood that the description of a vector in different coordinate systems can be obtained from the coordinate transformation relationship between these coordinate systems.

[0073] Among them, the formulas corresponding to the rotary joints in the above formulas (1)-(5) are for the case where two connecting rods are connected by rotation through a joint. The formulas corresponding to the linear drive joints are for the case where two connecting rods are linearly connected by a joint, so that the two connecting rods can move linearly.

[0074] Those skilled in the art will understand that the iterative Newton-Euler equations can have other different transformation forms, which are not shown one by one in the embodiments of this application, but these transformation forms do not depart from the principles and spirit of this application.

[0075] S3. Determine the inertial force and inertial torque of the target connecting rod at its center of mass based on the motion state parameters and inertial property parameters of each connecting rod.

[0076] Specifically, in some implementations, the inertial force and inertial torque of the target connecting rod at its center of mass are determined by using the backward recursive equations in the iterative Newton-Euler equations, based on the motion state parameters and inertial property parameters of each connecting rod.

[0077] For example, the inertial force and moment of inertia of the target connecting rod at its center of mass can be determined using the following inverse recursive equations in the iterative Newton-Euler equations:

[0078]

[0079]

[0080]

[0081]

[0082] in, Let m be the inertial force of connecting rod i at its center of mass. i Let i be the mass of the connecting rod. Let I be the linear acceleration of connecting rod i at its center of mass. i Let be the rotational inertia matrix of connecting rod i about its center of mass. f is the moment of inertia of the connecting rod at its center of mass. i,i-1 Based on the principles of dynamics, at point O i-1 The force exerted by connecting rod i-1 on connecting rod i, n i,i-1 Based on the principles of dynamics, at point O i-1 The resultant torque on connecting rod i-1 about connecting rod i. Here, the superscript of the vector indicates the reference coordinate system describing the vector (e.g., the superscript i indicates the coordinate system at position O). i (Described in the third coordinate system with the origin as the origin). It should be understood that the description of a vector in different coordinate systems can be obtained from the coordinate transformation relationship between these coordinate systems.

[0083] Those skilled in the art will understand that the aforementioned formulas (1)-(9) are in the form of a third coordinate system as the reference coordinate system. If a second coordinate system or other coordinate system is used as the reference coordinate system, the formulas will be transformed accordingly, and the principle and spirit remain the same.

[0084] S4. Obtain the force and torque between the two ends of the target connecting rod and the corresponding joint through the six-degree-of-freedom force and torque sensor.

[0085] Specifically, six-degree-of-freedom force and torque sensors are installed on the joints at both ends of the target connecting rod to acquire the force and torque between the two ends of the target connecting rod and the corresponding joints. It should be understood that the measurements from the force / torque sensors installed on the joints represent the actual measured force / torque between two adjacent connecting rods at that joint. Therefore, in this step, the measured force exerted by the connecting rods before and after the target connecting rod on the target connecting rod can be obtained.

[0086] S5. Determine the external force on the target connecting rod based on the inertial force and inertial torque of the target connecting rod at its center of mass, as well as the force and torque between the two ends of the target connecting rod and the corresponding joints.

[0087] In some embodiments, the external forces acting on the target connecting rod are determined based on the inertial force and moment of inertia of the target connecting rod at its center of mass, as well as the forces and moments between the two ends of the target connecting rod and the corresponding joints.

[0088] A first difference is determined between the inertial force of the target connecting rod at its center of mass and the force between the two ends of the target connecting rod and the corresponding joints, and this first difference is defined as the magnitude and direction of the external force acting on the target connecting rod. The first difference is a vector difference.

[0089] The following is combined Figure 6 This explains the principle of determining the magnitude and direction of the external force acting on the target connecting rod based on the first difference. For example... Figure 6 As shown, the inertial force F of the target connecting rod at its center of mass is... inertial [i] equals the force between the two ends of the target connecting rod and the corresponding joints (i.e., the six degrees of freedom forces in the corresponding joints at both ends of the target connecting rod and the forces sensed by the torque sensors) F sen [i] and F sen [i+1] is connected to the target rod by an external force F. ext The sum of [i] is:

[0090]

[0091] The inertial force F at the center of mass of the target connecting rod. inertial [i] As calculated in step S3, the magnitude and direction of the external force acting on the target connecting rod can be derived as follows:

[0092]

[0093] In other words, the vector F of the external force acting on the target connecting rod ext [i] equals the inertial force vector of the target connecting rod at its center of mass. The force F between the two ends of the target connecting rod and the corresponding joint sen [i]、F sen The difference of [i+1] is the first difference. Here, the first difference is a vector, from which the magnitude and direction of the external force on each target connecting rod can be calculated.

[0094] Furthermore, after determining the magnitude and direction of the external force, embodiments of this application can further calculate the specific location of the external force acting on each target connecting rod. In some embodiments, determining the location of the external force acting on the target connecting rod includes:

[0095] The net torque at the reference point of the target connecting rod is determined based on the second difference between the torque between the two ends of the target connecting rod and the corresponding joint, and the inertial torque of the target connecting rod at its center of mass; and

[0096] Based on the net torque at the reference point of the target connecting rod and the magnitude and direction of the external force acting on the target connecting rod, the position of the external force acting on the target connecting rod relative to the reference point is determined.

[0097] The reference point can be any point in the space where the robotic arm is located, and the specific reference point can be selected according to actual needs. In some embodiments, the location of the reference point can be the origin of the joint coordinate system corresponding to the joint at one end of the target connecting rod. In other embodiments, the location of the reference point can also be the centroid of the target connecting rod.

[0098] Specifically, the position of the external force acting on the target connecting rod relative to the reference point can be determined according to the following formula:

[0099]

[0100]

[0101] Where, r mag r is the shortest distance from the reference point to the line of action of the external force acting on the target connecting rod. vec M is the shortest vector from the reference point to the line of action of the external force on the target connecting rod, and F is the net torque.

[0102] Furthermore, before determining the position of the external force on the target connecting rod relative to the reference point based on the net torque at the reference point of the target connecting rod and the magnitude and direction of the external force on the target connecting rod, the method may further include the following steps:

[0103] Determine whether the magnitude of the external force is greater than a preset first threshold, and determine whether the value of the net torque is greater than a preset second threshold;

[0104] If the magnitude of the external force is less than the first threshold, then it is determined that the target connecting rod is not subject to external force.

[0105] 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, then it is determined that the external force on the target connecting rod is located at the reference point;

[0106] 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, then using the formulas (12) and (13) as described above, the position of the external force on the target connecting rod relative to the reference point is determined based on the net torque at the reference point of the target connecting rod and the magnitude and direction of the external force on the target connecting rod.

[0107] The method for determining the external force on the robotic arm in this embodiment of the application uses six-degree-of-freedom force and torque sensors installed in each joint to sense the force and torque acting on the joint in various directions. Combined with the calculated inertial force and inertial torque of the target connecting rod at the center of mass, the method can determine the magnitude, direction and position of the external force distributed on each target connecting rod, making the detection of the external force on the robotic arm more accurate.

[0108] It should be understood that although the steps in the flowcharts of the various embodiments described above are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the various embodiments described above may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages in other steps.

[0109] Based on the same inventive concept, another aspect of this application provides a robotic arm, which please refer to in conjunction with the invention. Figure 1 and Figure 7 The robotic arm 10 includes multiple connecting rods, multiple joints, and an operating unit. The connecting rods are connected to each other via the joints. Some connecting rods can be rotatably connected via the joints, while others can be connected linearly via the joints. The operating unit can be a gripper or other component used to perform the corresponding functions of the robotic arm. At least some of the connecting rods have six-degree-of-freedom force and torque sensors installed in the joints at both ends to sense the forces and torques acting on the corresponding joints. The robotic arm 10 also includes at least one memory 15 and at least one processor 16. The at least one memory 15 stores a computer program, which, when executed by the at least one processor 16, implements the steps in the method for determining the external forces acting on the robotic arm as described above.

[0110] Obtain the inertial property parameters of each of the connecting rods, wherein the inertial property parameters include the mass, center of mass, and moment of inertia of the connecting rod;

[0111] Determine the motion state parameters of each of the connecting rods, wherein the motion state parameters include the angular velocity, angular acceleration, and linear acceleration of each connecting rod;

[0112] Based on the motion state parameters and inertial property parameters of each connecting rod, determine the inertial force and inertial torque of the target connecting rod at the center of mass;

[0113] The forces and torques between the two ends of the target connecting rod and the corresponding joints are acquired using the six-degree-of-freedom force and torque sensors; and

[0114] The external force acting on the target connecting rod is determined based on the inertial force and inertial torque of the target connecting rod at its center of mass, as well as the force and torque between the two ends of the target connecting rod and the corresponding joints.

[0115] In some embodiments, determining the motion state parameters of each of the connecting rods includes:

[0116] Obtain the connection parameters and angle information of each joint, wherein the connection parameters are parameters representing the spatial positional relationship between two adjacent connecting rods, and the angle information of each joint includes joint angular position, joint angular velocity, and joint angular acceleration; and

[0117] Based on the inertial property parameters of each connecting rod, the connection parameters of each joint, and the angle information of each joint, the motion state parameters of each connecting rod are determined according to the principles of robot dynamics.

[0118] In other embodiments, each connecting rod of the robotic arm is equipped with an inertial measurement unit for measuring the angular velocity, angular acceleration, and linear acceleration of the corresponding connecting rod. Determining the motion parameters of each connecting rod includes acquiring the motion state parameters of each connecting rod from the inertial measurement unit.

[0119] In some embodiments, determining the inertial force and moment of inertia of the target connecting rod at its center of mass, based on the motion state parameters and inertial property parameters of each connecting rod, includes: determining the inertial force and moment of inertia of the target connecting rod at its center of mass using the backward recursive equations in the iterative Newton-Euler equations, based on the motion state parameters and inertial property parameters of each connecting rod. Specific determination methods can be referred to the foregoing embodiments and will not be repeated here.

[0120] In some embodiments, determining the external force acting on the target connecting rod based on the inertial force and moment of inertia of the target connecting rod at its center of mass, and the forces and moments between the two ends of the target connecting rod and the corresponding joints, includes:

[0121] A first difference is determined between the inertial force of the target connecting rod at its center of mass and the force between the two ends of the target connecting rod and the corresponding joints, and this first difference is defined as the magnitude and direction of the external force acting on the target connecting rod. The first difference is a vector difference.

[0122] In some embodiments, the method further includes:

[0123] The net torque at the reference point of the target connecting rod is determined based on the second difference between the torque between the two ends of the target connecting rod and the corresponding joint, and the inertial torque of the target connecting rod at its center of mass; and

[0124] Based on the net torque at the reference point of the target connecting rod and the magnitude and direction of the external force acting on the target connecting rod, the position of the external force acting on the target connecting rod relative to the reference point is determined.

[0125] In some embodiments, before determining the position of the external force on the target connecting rod relative to the reference point based on the net torque at the reference point of the target connecting rod and the magnitude and direction of the external force on the target connecting rod, the method further includes:

[0126] Determine whether the magnitude of the external force is greater than a preset first threshold, and determine whether the value of the net torque is greater than a preset second threshold;

[0127] If the magnitude of the external force is less than the first threshold, then it is determined that the target connecting rod is not subject to external force.

[0128] 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, then it is determined that the external force on the target connecting rod is located at the reference point; and

[0129] 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, then the position of the external force on the target connecting rod relative to the reference point is determined according to the following formula:

[0130]

[0131]

[0132] Where, r mag r is the shortest distance of the line of action of the external force acting on the target connecting rod. vec M is the shortest vector from the position of the reference point to the line of action of the external force on the target connecting rod, F is the net torque, and F is the magnitude and direction of the external force on the target connecting rod.

[0133] Another aspect of this application provides a computer-readable storage medium having computer program instructions stored thereon, which, when executed by a processor, implement the method for determining the external force on a robotic arm as described in one or more of the preceding embodiments.

[0134] Those skilled in the art will understand that all or part of the processes in the above-described embodiments can be implemented by controlling related hardware through computer program instructions. These computer program instructions can be stored in a non-volatile computer-readable storage medium. When executed, the computer program instructions can include the processes described in the above embodiments. Any references to memory, databases, or other media used in the embodiments provided in this application can include at least one of non-volatile 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), magnetic 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 can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM).

[0135] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0136] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for determining the external force acting on a robotic arm, characterized in that, The robotic arm includes multiple connecting rods and multiple joints connected in sequence. The connecting rods are connected to each other through the joints. At least some of the joints at both ends of the connecting rods are provided with six-degree-of-freedom force and torque sensors. The six-degree-of-freedom force and torque sensors are used to sense the forces and torques acting on the corresponding joints. The method includes: Obtain the inertial property parameters of each of the connecting rods, wherein the inertial property parameters include the mass, center of mass, and moment of inertia of the connecting rod; Determine the motion state parameters of each of the connecting rods, wherein the motion state parameters include the angular velocity, angular acceleration, and linear acceleration of each connecting rod; Based on the motion state parameters and inertial property parameters of each connecting rod, determine the inertial force and inertial torque of the target connecting rod at the center of mass; The forces and torques between the two ends of the target connecting rod and the corresponding joints are acquired using the six-degree-of-freedom force and torque sensors; and The external force acting on the target connecting rod is determined based on the inertial force and inertial torque of the target connecting rod at its center of mass, as well as the force and torque between the two ends of the target connecting rod and the corresponding joints.

2. The method according to claim 1, characterized in that, Determining the motion state parameters of each of the connecting rods includes: Obtain the connection parameters and angle information of each joint, wherein the connection parameters are parameters representing the spatial positional relationship between two adjacent connecting rods, and the angle information of each joint includes joint angular position, joint angular velocity, and joint angular acceleration; and Based on the inertial property parameters of each connecting rod, the connection parameters of each joint, and the angle information of each joint, the motion state parameters of each connecting rod are determined according to the principles of robot dynamics.

3. The method according to claim 1, characterized in that, Each connecting rod is equipped with an inertial measurement unit for measuring the angular velocity, angular acceleration, and linear acceleration of the corresponding connecting rod. Determining the motion parameters of each connecting rod includes: The motion state parameters of each connecting rod are obtained from the inertial measurement unit.

4. The method according to claim 1, characterized in that, The step of determining the inertial force and inertial torque of the target connecting rod at its center of mass based on the motion state parameters and inertial property parameters of each connecting rod includes: Based on the motion state parameters and inertial property parameters of each connecting rod, the inertial force and inertial torque of the target connecting rod at the center of mass are determined using the inverse recursive equation in the iterative Newton-Euler equations.

5. The method according to claim 4, characterized in that, The determination of the external force acting on the target connecting rod based on the inertial force and inertial torque at the center of mass of the target connecting rod, and the forces and torques between the two ends of the target connecting rod and the corresponding joints, includes: Determine the first difference between the inertial force of the target connecting rod at its center of mass and the force between the two ends of the target connecting rod and the corresponding joint, and determine the first difference as the magnitude and direction of the external force on the target connecting rod.

6. The method according to claim 5, characterized in that, The method further includes: The net torque at the reference point of the target connecting rod is determined based on the second difference between the torque between the two ends of the target connecting rod and the corresponding joint, and the inertial torque of the target connecting rod at its center of mass; and Based on the net torque at the reference point of the target connecting rod and the magnitude and direction of the external force acting on the target connecting rod, the position of the external force acting on the target connecting rod relative to the reference point is determined.

7. The method according to claim 6, characterized in that, Before determining the position of the external force on the target connecting rod relative to the reference point based on the net torque at the reference point of the target connecting rod and the magnitude and direction of the external force on the target connecting rod, the method further includes: Determine whether the magnitude of the external force is greater than a preset first threshold, and determine whether the value of the net torque is greater than a preset second threshold; If the magnitude of the external force is less than the first threshold, then it is determined that the target connecting rod is not subject to external force; and 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, then it is determined that the external force on the target connecting rod is located at the reference point.

8. The method according to claim 7, characterized in that: 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, then the position of the external force on the target connecting rod relative to the reference point is determined according to the following formula: Where, r mag r is the shortest distance from the reference point to the line of action of the external force acting on the target connecting rod. vec M is the shortest vector of the line of action of the external force on the target connecting rod from the reference point, F is the net torque, and F is the magnitude and direction of the external force on the target connecting rod.

9. A robotic arm, comprising: Multiple connecting rods connected in sequence; Multiple joints, with the connecting rods connected to each other via the joints; Multiple six-degree-of-freedom force and torque sensors are disposed in the joints at at least part of the ends of the connecting rod, the six-degree-of-freedom force and torque sensors being used to sense the forces and torques acting on the corresponding joints; as well as The system includes at least one memory and at least one processor, wherein the at least one memory stores computer program instructions that, when executed by the at least one processor, perform the method for determining the external force acting on the robotic arm as described in any one of claims 1-8.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the method for determining the external force on the robotic arm as described in any one of claims 1-8.

Images