A method for a robot to achieve full body compliance by processing large-area tactile signals

Abstract

The present invention discloses a method for a robot to achieve full-body compliance by processing large-area tactile signals. The present invention obtains tactile signals through a large-area tactile skin array covered on the surface of a multi-degree-of-freedom mobile robot, and processes and simplifies the signals to be equivalent to a six-dimensional resultant force / torque of a single-point contact, thereby avoiding the separate calculation of the force / torque of each tactile sensing unit. The present invention maps the resultant force to each joint of the robot to obtain the external torque of the joint, and then obtains the motion instructions of the robot when it is subjected to force through an assumed robot virtual dynamics model, thereby achieving the full-body compliance behavior of the robot in response to external forces, and further contributing to the realization of large-scale and safe human-machine physical interaction.

Description

Technical Field

[0001] The present invention relates to the field of robot perception and human-machine interaction, and in particular to a method for a robot to achieve whole-body compliance by processing large-area tactile signals. Background Art

[0002] Tactile perception of robots is an important and practical ability. In recent years, it has been increasingly used in robot multimodal perception, dexterous manipulation, human-robot interaction and other fields (Mittendorfer, P., Yoshida, E. and Cheng, G., 2015. Realizing whole-body tactile interactions with a self-organizing, multi-modal artificial skin on a humanoid robot. Advanced Robotics, 29(1), pp.51-67.), (Niu, H., Li, H., Gao, S., Li, Y., Wei, X., Chen,Y., Yue, W., Zhou, W. and Shen, G., 2022. Perception‐to‐cognition tactile sensing based on artificial‐intelligence‐motivated human full‐skin bionicelectronic skin. Advanced Materials, 34(31), p.2202622.), (Pugach, G., Melnyk,A., Tolochko, O., Pitti, A. and Gaussier, P., 2016, October. Touch-basedadmittance control of a robotic arm using neural learning of an artificialskin. In 2016 IEEE / RSJ International Conference on Intelligent Robots andSystems (IROS) (pp. 3374-3380). IEEE.), (Strohmayr, MW, Wörn, H. andHirzinger, G., 2013, May. The DLR artificial skin step I: Uniting sensitivity and collision tolerance. In 2013 IEEE International Conference on Roboticsand Automation (pp. 1012-1018).IEEE.), (Teyssier, M., Parilusyan, B., Roudaut, A. and Steimle, J., 2021, May. Human-like artificial skin sensor for physical human-robot interaction. In 2021 IEEE International Conference on Robotics and Automation (ICRA), (pp. 3626-3633). IEEE.). .

[0003] Compared with traditional end force sensors, tactile skin can obtain richer surface contact information, allowing robots to achieve a wider range of human-machine physical interactions. The rich tactile signals make it necessary to process and analyze them. However, there is a lack of a method that can equate surface contact to point contact that is applicable to robot tactile skin.

[0004] In order to ensure the safe coexistence of humans and robots, robots should be compliant to external forces. However, when the tactile skin senses external forces over a large area, the contact is not limited to a single point and the distribution area is large and random. Currently, there is a lack of methods to achieve full-body compliance of robots based on large-area tactile skin. Summary of the invention

[0005] The purpose of the present invention is to address the deficiencies of the prior art and provide a method for a robot to achieve full body compliance by processing large-area tactile signals.

[0006] The object of the present invention is achieved through the following technical solution: A method for a robot to achieve whole body compliance by processing large-area tactile signals, comprising the following steps:

[0007] Step 1, calculating the pressure center and geometric center of the tactile contact surface of a single tactile skin, and obtaining the total vector sum of the external forces of all tactile units as a resultant force, wherein the resultant force acts on the pressure center; establishing a coordinate system with the geometric center as the origin as a reference, and calculating the torque of the resultant force;

[0008] Step 2: For each tactile skin, the Jacobian matrix of the geometric center coordinate system of the contact surface of the tactile skin is calculated, and the resultant force / torque obtained in step 1 is mapped to the whole body joints of the robot to obtain the joint torque; the joint torques corresponding to all skins are summed to obtain the total joint resultant external torque;

[0009] Step 3: Establish a virtual dynamic model of the robot. The input is the joint external torque obtained in step 2. Substitute it into the kinematic equation to obtain the joint acceleration. Further integrate it to obtain the joint velocity or position command and publish it.

[0010] Furthermore, the step 1 includes the following sub-steps:

[0011] 1.1. Find the vector sum of the contact forces of all tactile units in contact on a single tactile skin , as shown in the following formula:

[0012] ;

[0013] Among them, the vector and That is, the resultant force of the contact force, i represents the number of a single tactile skin, j represents the number of the tactile unit in contact, represents the contact force;

[0014] 1.2. Find the pressure center of the tactile skin contact surface , also known as the zero moment point, is the point where the relative moment of the contact surface is 0, as shown in the following formula:

[0015] ;

[0016] in, Tactile unit The coordinates of , further obtained:

[0017] ;

[0018] Solving the above formula ;

[0019] 1.3. Find the geometric center of the tactile skin contact surface , average the coordinates of the tactile units in the contact surface:

[0020] ;

[0021] in, Indicates the number of tactile units in the contact surface;

[0022] 1.4. Taking the geometric center A reference coordinate system is established for the origin, and the direction of the coordinate axis is consistent with the joint coordinate system. The resultant force / torque of the contact surface relative to the geometric center is calculated as shown in the following formula:

[0023] ;

[0024] in, represents the resultant moment;

[0025] The above steps avoid the calculation and summation of each tactile unit; the force / torque of the contact surface relative to the geometric center for:

[0026] .

[0027] Furthermore, the step 2 includes the following sub-steps:

[0028] 2.1. Calculate the Jacobian matrix of the geometric center coordinate system of each tactile skin contact surface ;

[0029] 2.2. Map the resultant force / torque to the joint torque and sum all skins to obtain the total external torque of the robot's joints , as shown in the following formula:

[0030] ;

[0031] Where i represents the number of each tactile skin. represents the resultant force / torque at the geometric center, Represents the transpose of a matrix.

[0032] Furthermore, the step 3 includes the following sub-steps:

[0033] 3.1. Establish the general equation of robot dynamics, as shown in the following formula:

[0034] ;

[0035] in, Represent the joint position, velocity and acceleration respectively, Represents the robot inertia matrix (the specific parameters use the actual physical parameters of the robot), represents the robot's Coriolis force / centripetal force matrix, represents the joint torque generated by the robot's gravity, represents the external moment of the joint, Represents the control torque output by the joint; , to compensate for the effect of gravity;

[0036] 3.2. At fixed time intervals, substitute the joint external torque and the current state of the robot into the general equation of dynamics, calculate the joint acceleration at the current moment, integrate to obtain the joint velocity and position command at the next moment, and issue the motion command of each joint.

[0037] The present invention also provides an electronic device, comprising a memory and a processor, wherein the memory is coupled to the processor; wherein the memory is used to store program data, and the processor is used to execute the program data to implement the method of a robot achieving whole-body compliance by processing large-area tactile signals.

[0038] The present invention also provides a computer-readable storage medium on which a computer program is stored. When the program is executed by a processor, the method for a robot to achieve whole-body compliance by processing large-area tactile signals is implemented.

[0039] The beneficial effects of the present invention are as follows: by making large-area contact equivalent to single-point contact, the calculation of the torque of the contact surface relative to the reference point is simplified, and the key information of the force on the tactile contact surface is extracted from more data; at the same time, the compliant behavior of the robot is realized through the dynamic model, so that the robot can sense and comply with external forces through the tactile skin to ensure large-scale and safe human-machine physical interaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0041] Figure 1 It is a schematic diagram of attaching multiple tactile skins to the surface of a multi-degree-of-freedom mobile robot;

[0042] Figure 2 It is a schematic diagram of the pressure center and geometric center obtained according to the pressure distribution of the contact surface when the tactile skin of a person and a robot come into contact;

[0043] Figure 3 It is a flow chart of the present invention. DETAILED DESCRIPTION

[0044] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Instead, they are merely examples of devices and methods consistent with some aspects of the present invention as detailed in the appended claims.

[0045] The terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The singular forms "a", "the" and "the" used in the present invention and the appended claims are also intended to include plural forms unless the context clearly indicates other meanings. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0046] It should be understood that although the terms first, second, third, etc. may be used in the present invention to describe various information, these information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other. For example, without departing from the scope of the present invention, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Depending on the context, the word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining".

[0047] The present invention is described in detail below in conjunction with the accompanying drawings. In the absence of conflict, the features of the following embodiments and implementations can be combined with each other.

[0048] like Figure 3 As shown, an embodiment of the present invention proposes a method for a robot to achieve whole-body compliance by processing large-area tactile signals, wherein the robot is a conventional mobile rigid robot (a joint coordinate system established under standard DH parameters), and includes the following steps:

[0049] (1) Calculate the virtual resultant force / torque of a single tactile skin: First, calculate the pressure center and geometric center of the tactile contact surface, then calculate the total vector sum of the external forces of all tactile units as the resultant force, which acts on the pressure center; then use the geometric center as the origin as a reference to calculate the torque of the resultant force; specifically, it includes the following sub-steps:

[0050] (1.1) If Figure 1 The figure shows the robot tactile skin and its tactile unit. ) on all the tactile units (numbered ) contact force The vector sum (in the joint coordinate system where the skin is located) is used as the resultant force on the tactile skin:

[0051] ;

[0052] The vector and The resultant contact force is represents a 3×1 real vector, represents an m×n real matrix.

[0053] (1.2) If Figure 2 As shown, find the three-dimensional coordinates of the pressure center of the skin contact surface in the joint coordinate system , also known as the zero moment point, that is, the relative moment of all tactile units relative to the contact surface is Points:

[0054] ;

[0055] in, Tactile unit The three-dimensional coordinates (in the joint coordinate system where the skin is located) are further obtained:

[0056] ;

[0057] Solving the above formula .

[0058] (1.3) If Figure 2 As shown, the three-dimensional coordinates of the geometric center of the tactile skin contact surface in the joint coordinate system are calculated. , average the three-dimensional coordinates of all tactile units on the contact surface:

[0059] ;

[0060] in, Indicates the number of tactile units in the contact surface.

[0061] (1.4) With the geometric center A reference Cartesian coordinate system is established as the origin, and the direction of the coordinate axis is consistent with the joint coordinate system. Then the force arm of the resultant force on the skin relative to the geometric center is , then the calculation of the resultant moment can be simplified to:

[0062] ;

[0063] in, Represents the resultant torque.

[0064] The above steps avoid the calculation and summation of each tactile unit, improving the calculation efficiency. Then the six-dimensional resultant force / torque of the contact surface relative to the geometric center is:

[0065] .

[0066] (2) Calculate the virtual total external torque on the robot's joints: For each tactile skin, first calculate the Jacobian matrix of the geometric center coordinate system of the contact surface, then map the resultant force / torque obtained in step (1) to the robot's joints through the principle of virtual work to obtain the joint torque, and finally sum the joint torques corresponding to all skins to obtain the total joint total external torque; specifically, the following sub-steps are included:

[0067] (2.1) Pre-calculate the analytical form of the Jacobian matrix with each tactile unit as the origin in the same coordinate axis direction, and then approximate the Jacobian matrix of the point based on the geometric position of the geometric center of the contact surface in the tactile unit array, and calculate the Jacobian matrix of each tactile skin (numbered ) Jacobian matrix of the contact surface geometric center coordinate system .

[0068] (2.2) Through the principle of virtual work, that is, the mapping relationship between the Cartesian space force of the robot and the joint space force, the external force / torque of each skin is mapped to the joint torque, and the joint torque obtained by mapping the resultant force / torque of all skins to the joint is summed:

[0069] ;

[0070] The total external torque of the robot's joints is obtained through the above formula, where i represents the number of each tactile skin, represents the resultant force / torque at the geometric center, Represents the transpose of a matrix.

[0071] (3) Robot forward kinematics solution: Establish a virtual dynamic model of the robot, and use the joint external torque obtained in step (2) as input. Substitute it into the kinematic equation to solve the forward dynamics to obtain the joint acceleration. Further integrate in each control cycle to obtain the joint velocity or position command and issue the motion command for each joint. Specifically, it includes the following sub-steps:

[0072] (3.1) According to the actual physical parameters of the robot, the general equation of robot dynamics is established (assuming that the number of robot joints is ):

[0073] ;

[0074] in, are joint positions, velocities and accelerations, is the robot inertia matrix (the specific parameters use the actual physical parameters of the robot), is the robot's Coriolis force / centripetal force matrix, is the joint torque generated by the robot's gravity. The above parameter matrix can be calculated in real time by robot dynamics libraries such as Pinocchio and RBDL. is the external moment of the joint, is the control torque output by the joint; , that is, to compensate for the effect of gravity;

[0075] (3.2) At fixed time intervals To control the cycle, the external torque of the joint and the current state of the robot are substituted into the dynamic equation, the joint acceleration of the current control cycle is calculated, and then the acceleration is integrated within the control cycle to obtain the joint velocity at the next moment. Similarly, the joint velocity is integrated to obtain the joint position, and the motion instructions of each joint are issued.

[0076] ;

[0077] .

[0078] in, Indicates the current state of the joints. Indicates the states of the joints at the next moment after the interval control period T.

[0079] An embodiment of the present invention also provides an electronic device, comprising a memory and a processor, wherein the memory is coupled to the processor; wherein the memory is used to store program data, and the processor is used to execute the program data to implement a method for a robot to achieve whole-body compliance by processing large-area tactile signals as described in any embodiment.

[0080] An embodiment of the present invention further provides a computer-readable storage medium having a computer program stored thereon. When the program is executed by a processor, the method for a robot to achieve whole-body compliance by processing large-area tactile signals as described in any embodiment is implemented.

[0081] The computer-readable storage medium may be an internal storage unit of any device with data processing capability described in any of the aforementioned embodiments, such as a hard disk or a memory. The computer-readable storage medium may also be any device with data processing capability, such as a plug-in hard disk, a smart media card (SMC), an SD card, a flash card, etc. equipped on the device. Furthermore, the computer-readable storage medium may also include both an internal storage unit of any device with data processing capability and an external storage device. The computer-readable storage medium is used to store the computer program and other programs and data required by any device with data processing capability, and may also be used to temporarily store data that has been output or is to be output.

[0082] The above embodiments are only used to illustrate the design ideas and features of the present invention, and their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. The protection scope of the present invention is not limited to the above embodiments. Therefore, any equivalent changes or modifications made based on the principles and design ideas disclosed by the present invention are within the protection scope of the present invention.

Claims

1. A method for a robot to achieve full body compliance by processing large-area tactile signals, characterized in that: The steps include: (1) calculating the pressure center and geometric center of the tactile contact surface of a single piece of tactile skin, and obtaining the total vector sum of the external forces of all tactile units as a resultant force, wherein the resultant force acts on the pressure center; establishing a coordinate system with the geometric center as the origin as a reference, and calculating the torque of the resultant force; (2) For each tactile skin, the Jacobian matrix of the geometric center coordinate system of the contact surface of the tactile skin is calculated, and the resultant force / torque obtained in step (1) is mapped to the joints of the robot to obtain the joint torque; The joint torques corresponding to all skins are summed to obtain the total joint external torque; (3) A virtual dynamics model of the robot is established, and the joint external torque obtained in step (2) is input, which is substituted into the kinematic equation to obtain the joint acceleration, and the joint velocity and position instructions are further integrated and issued.

2. A method for achieving whole-body compliance of a robot by processing large-area tactile signals according to claim 1, characterized in that: The step (1) comprises the following sub-steps: (1.1) Find the vector sum of the contact forces of all tactile units in contact on a single tactile skin F i , as shown in the following formula: Among them, the vector and F i That is, the resultant force of the contact force, i represents the number of a single tactile skin, j represents the number of the tactile unit in contact, and f i，j represents the contact force; (1.2) Find the pressure center p of the tactile skin contact surface i , as shown in the following formula: Among them, r i，j is the coordinate of tactile unit j, and further we get: Solve the above formula to get p i ; (1.3) Find the geometric center g of the tactile skin contact surface i , average the coordinates of the tactile units in the contact surface: g i =(∑ j r i，j ) / n i ; Among them, n i Indicates the number of tactile units in the contact surface; (1.4) With the geometric center g i A reference coordinate system is established for the origin, and the direction of the coordinate axis is consistent with the joint coordinate system. The resultant force / torque of the contact surface relative to the geometric center is calculated as shown in the following formula: C i =(p i -g i )×F i ; Among them, Γ i represents the resultant moment; The resultant force / torque W of the contact surface relative to the geometric center i for:

3. The method for achieving whole-body compliance of a robot by processing large-area tactile signals according to claim 1, characterized in that: The step (2) comprises the following sub-steps: (2.1) Calculate the Jacobian matrix J of the geometric center coordinate system of each tactile skin contact surface i ; (2.2) Map the resultant force / torque to the joint torque and sum all skins to obtain the total external torque τ of the robot's joints ext , as shown in the following formula: Where i represents the number of each tactile skin, W i represents the resultant force / torque at the geometric center, and T represents the transpose of the matrix.

4. The method for achieving whole-body compliance of a robot by processing large-area tactile signals according to claim 1, characterized in that: The step (3) comprises the following sub-steps: (3.1) Establish the robot dynamics equation as shown in the following formula: in, Respectively represent joint position, velocity and acceleration, M(q) represents the robot inertia matrix, represents the robot's Coriolis force / centripetal force matrix, g(q) represents the joint torque generated by the robot's gravity, τ ext represents the external moment of the joint, τ ctrl represents the control torque output by the joint; let the control torque output by the joint τ ctrl =g(q), compensating for the effect of gravity; (3.2) At fixed time intervals, the joint external torque and the current state of the robot are substituted into the general equation of dynamics, the joint acceleration at the current moment is calculated, and then the joint velocity and position instructions at the next moment are obtained by integration and the motion instructions of each joint are issued.

5. An electronic device comprising a memory and a processor, characterized in that: The memory is coupled to the processor; wherein the memory is used to store program data, and the processor is used to execute the program data to implement a method for a robot to achieve whole-body compliance by processing large-area tactile signals as described in any one of claims 1-4.

6. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by the processor, a method for a robot to achieve whole-body compliance by processing large-area tactile signals as described in any one of claims 1 to 4 is implemented.

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