Online variable impedance compliant control method for human-robot interaction

Abstract

The application discloses an online variable impedance compliance control method for human-computer interaction, and solves the technical problem that the compliance of human-computer interaction is difficult to control. The online variable impedance compliance control method for human-computer interaction comprises the following steps: obtaining an operator intention according to a robot end speed and a compensation force control law to design a variable impedance strategy, obtaining a desired speed and a desired acceleration of the robot from the variable impedance strategy; obtaining a reference speed according to an error between the desired speed and the robot end speed; calculating a speed compensation term according to the reference speed and the robot end speed, thereby calculating a robot speed control law according to the speed compensation term and a robot dynamics model; calculating an estimated value of a human hand feedforward force, an estimated value of a human hand damping parameter and an estimated value of a human hand stiffness parameter through a parameter self-adaptive law, thereby obtaining a compensation force control law; and a total controller of the robot performs compliance control on human-computer interaction according to the robot speed control law and the compensation force control law.

Description

Technical Field

[0001] This invention relates to the technical field of compliant human-computer interaction control, and more specifically, to an online variable impedance compliant control method for human-computer interaction. Background Technology

[0002] With the increasingly widespread application of robots, the interaction between robots and operators is also increasing. Position control alone is no longer sufficient to meet production needs. In human-robot interaction, robots need to respond to the forces exerted by the operator. Therefore, achieving compliant robot control is essential, such as teaching, collision detection, and precise force control. Impedance control is one of the important means to achieve compliant control in human-robot interaction. One of the purposes of impedance control is to achieve compliant control in human-robot interaction through the dynamic relationship between robot position and force.

[0003] Zhang Sihan's paper, "Research on Human-Robot Interaction with Force-Controlled Exoskeletons and Compliant Assembly of Robotic Arms," ​​proposes a velocity-based admittance controller, primarily using the robot's mass and damping parameters to achieve compliant control of human-robot interaction. However, using force sensors at the robot's end effector to obtain the human-robot interaction force presents challenges in reality. Force sensors exhibit measurement noise, which can negatively impact the control system, and their cost is also high. Furthermore, to achieve compliant human-robot interaction control, a variable impedance strategy should be adopted for the robot, understanding the operator's intentions. Summary of the Invention

[0004] The main objective of this invention is to provide an online variable impedance compliance control method for human-computer interaction, so as to solve the technical problem that the compliance of human-computer interaction is difficult to control in the prior art.

[0005] To achieve the above objectives, this invention provides a human-computer interactive online variable impedance compliant control method, the technical solution of which is as follows:

[0006] A human-computer interaction-based online variable impedance compliance control method includes the following steps:

[0007] The operator's intention is obtained based on the robot's end-effector velocity and the compensation force control law. A variable impedance strategy is designed, and the robot's desired velocity and desired acceleration are obtained from the variable impedance strategy. Then, the reference velocity is obtained based on the error between the desired velocity and the robot's end-effector velocity.

[0008] The speed compensation term is calculated based on the reference speed and the robot end-effector speed. Then, the robot speed control law is calculated based on the speed compensation term and the robot dynamics model.

[0009] The estimated values ​​of the feedforward force, damping parameters, and stiffness parameters of the human hand are obtained by calculating the parameter adaptive law, thereby obtaining the compensation force control law.

[0010] The robot's master controller performs compliant control of human-robot interaction based on the robot's speed control law and compensating force control law.

[0011] In the control method of this invention, firstly, the interaction force generated during robot-human interaction and the robot's end effector speed (i.e., the speed of the robot's end effector) are combined to predict the operator's intention, thereby designing a variable impedance strategy based on the operator's intention; secondly, to make the speed more stable, a speed compensation term is added to the dynamic model, and the speed control law designed in this way enables the robot speed to be more stable; thirdly, to eliminate the noise introduced by the force sensor when measuring the interaction force, a compensating force control law obtained through parameter adaptive law is used to replace the interaction force, thereby eliminating the force sensor noise. Verification has shown that the control method of this invention effectively solves the technical problem of difficulty in controlling the compliance of human-machine interaction in the prior art, enabling the robot speed to remain stable within an acceptable range during interaction with the operator, effectively achieving compliance in human-machine interaction.

[0012] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0013] The accompanying drawings, which form part of this invention, are used to aid in understanding the invention. The content provided in the drawings and their related descriptions can be used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0014] Figure 1 This is a schematic diagram of an embodiment of the human-computer interaction online variable impedance compliance control method of the present invention. Detailed Implementation

[0015] The present invention will now be clearly and completely described in conjunction with the accompanying drawings. Those skilled in the art will be able to implement the present invention based on these descriptions. Before describing the present invention in conjunction with the accompanying drawings, it should be particularly noted that:

[0016] The technical solutions and features provided in the various parts of this invention, including the following description, can be combined with each other without conflict.

[0017] Furthermore, the embodiments of the present invention described below are generally only some, not all, of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0018] Regarding the terminology and units used in this invention: The terms "comprising," "having," and any variations thereof in the specification, claims, and related parts of this invention are intended to cover non-exclusive inclusion.

[0019] Figure 1 This is a schematic diagram of an embodiment of the human-computer interaction online variable impedance compliance control method of the present invention. Figure 1 In the diagram, "+" represents the addition operator, "-" represents the subtraction operator, and "○" represents the comparator.

[0020] like Figure 1 As shown, an embodiment of the human-computer interaction online variable impedance compliance control method includes the following steps:

[0021] (1) Based on the operator’s intention obtained from the robot end-effector speed and the compensation force control law, a variable impedance strategy is designed. The desired speed and desired acceleration of the robot are obtained from the variable impedance strategy. Then, the reference speed is obtained based on the error between the desired speed and the robot end-effector speed.

[0022] The variable impedance strategy adjusts the damping and mass parameters in the impedance model according to the operator's intention. Specifically, the interaction force generated when the robot interacts with the human and the robot's end-effector velocity are combined to predict the operator's intention: when the direction of the human-machine interaction force and the direction of the robot's end-effector velocity are the same, it is assumed that the operator wants to accelerate; when the direction of the human-machine interaction force and the direction of the robot's end-effector velocity are opposite, it is assumed that the operator wants to decelerate.

[0023] The impedance model is a second-order mass-damped model, specifically:

[0024]

[0025] During acceleration, b = b c -ρ|f kr |;

[0026] During deceleration, b = b c +κ|f kr |;

[0027]

[0028] Where m is the mass parameter and b is the damping parameter; For the desired speed; f is the desired acceleration. h For human-computer interaction, in order to eliminate the adverse effects of force sensors, the human-computer interaction force f... h The value of b will be replaced by the value of the compensating force control law; c ρ and κ are the default values ​​for the damping parameters; ρ and κ are adjustable parameters; |fkr | represents the absolute value of the compensating force control law; m c This is the default quality setting.

[0029] The calculation model for the human-computer interaction force is as follows:

[0030]

[0031] Among them, f h It is human-computer interaction; f r It is the feedforward force of the human hand, B r It is the damping parameter of the human hand, K r These are the stiffness parameters of the human hand; α is a positive constant; e is the robot's position error, e = xx d x is the position of the robot's end effector. d For the desired position; For robot speed error, For the robot's end effector speed, t represents the desired velocity; t represents time.

[0032] (2) The speed compensation term is calculated based on the reference speed and the robot end-effector speed, and then the robot speed control law is calculated based on the speed compensation term and the robot dynamics model.

[0033] The speed control law is as follows:

[0034]

[0035] Among them, f kv It is the robot speed control law; M x It is the robot's end-effector inertia matrix; C x It is the matrix of centrifugal force and Coriolis force at the end of the robot; G x ξ is the gravity matrix at the end; ξ is a positive constant. For reference speed; It is the reference acceleration.

[0036] The speed control law consists of a speed compensation term and a dynamic speed term, wherein... This refers to the speed compensation term; This is the dynamic model of the robot.

[0037] (3) The estimated values ​​of the feedforward force, damping parameters, and stiffness parameters of the human hand are obtained by calculating the parameter adaptive law, thereby obtaining the compensation force control law.

[0038] The aforementioned adaptive parameter law is:

[0039]

[0040] The compensating force control law is as follows:

[0041]

[0042] Among them, f kr It is the compensatory force control law; An estimate of the feedforward force of the human hand; The estimated values ​​of the damping parameters for the human hand; The estimated values ​​of the stiffness parameters of the human hand; Γ K ,Γ B and Γ f All are positive definite matrices; x represents the position of the robot's end effector. For reference speed, It is a normal number.

[0043] (4) The robot’s main controller performs compliant control of human-machine interaction based on the robot’s speed control law and compensating force control law;

[0044] The robot's main controller is composed of the aforementioned calculation models for the speed control law and the compensation force control law, namely:

[0045]

[0046] in, This provides a dynamic model of the robot, enabling position tracking. For speed compensation, error compensation is used to control the robot speed within an acceptable range; The compensating force control law is used to compensate for the human-computer interaction force.

[0047] The stability of the control method of the present invention will be demonstrated below using the Lyapunov function.

[0048] The Lyapunov function for a human-computer interaction compliant system with a powerless sensor is:

[0049]

[0050] in, and tr(·) represents the trace of ·.

[0051] Its derivative is:

[0052]

[0053] in, diag(·) denotes a diagonal matrix with a dot. Let I denote the Kroll inner product, where I is the identity matrix. Ψ(t)=[f r T (t),vec(K r (t)) T ,vec(B r (t)) T ] T vec(·) denotes the column vectorization operator, ΔΨ(t)=Ψ(t)-Ψ(t-δ), where δ is a time constant.

[0054] In order to make Only in That is, in Within the range.

[0055] in, D2=-η||Ψ(t)||, D3=-ζ||θ|| 2 γ, γ1, and γ2 are positive constants. Therefore, the control method of this invention can ensure that the system's stability and speed vary within an acceptable range, ultimately making human-machine interaction smoother even without sensors.

[0056] The foregoing has described the relevant content of the present invention. Those skilled in the art will be able to implement the present invention based on these descriptions. All other embodiments obtained by those skilled in the art based on the above description of the present invention without inventive effort should fall within the scope of protection of the present invention.

Claims

1. A human-computer interactive online variable impedance compliance control method, characterized in that: Including the following steps: The operator's intention is obtained based on the robot's end-effector velocity and the compensation force control law. A variable impedance strategy is designed, and the robot's desired velocity and desired acceleration are obtained from the variable impedance strategy. Then, the reference velocity is obtained based on the error between the desired velocity and the robot's end-effector velocity. The speed compensation term is calculated based on the reference speed and the robot end-effector speed. Then, the robot speed control law is calculated based on the speed compensation term and the robot dynamics model. The estimated values ​​of the feedforward force, damping parameters, and stiffness parameters of the human hand are obtained by calculating the parameter adaptive law, thereby obtaining the compensation force control law. The robot's main controller performs compliant control of human-robot interaction based on the robot's speed control law and compensating force control law; The variable impedance strategy adjusts the damping and mass parameters in the impedance model according to the operator's intention. Specifically, the interaction force generated when the robot interacts with the human and the robot's end-effector velocity are combined to predict the operator's intention: when the direction of the human-robot interaction force and the direction of the robot's end-effector velocity are the same, it is assumed that the operator wants to accelerate; when the direction of the human-robot interaction force and the direction of the robot's end-effector velocity are opposite, it is assumed that the operator wants to decelerate. The impedance model is a second-order mass-damped model, specifically: ； The speed control law is as follows: ； The compensating force control law is as follows: ； The aforementioned adaptive parameter law is: ； In the formula, m For quality parameters; b For damping parameters; For the desired speed; For the desired acceleration; f h For human-computer interaction, in order to eliminate the adverse effects of force sensors, therefore, human-computer interaction force... f h The value will be replaced by the value of the compensation force control law; f kv It is the robot's speed control law; M x It is the robot's end effector inertia matrix; C x It is the matrix of centrifugal force and Coriolis force at the end of the robot; G x It is the gravity matrix at the end; ζ It is a positive number; This refers to the robot's end effector velocity. For reference speed; It is the reference acceleration; This refers to the speed compensation term; For the robot's dynamic model; f kr It is the compensatory force control law; a It is a positive constant; An estimate of the feedforward force of the human hand; The estimated values ​​of the damping parameters for the human hand; Estimates of the stiffness parameters of the human hand; e For robot position error, This refers to the robot's speed error. , and All are positive definite matrices; , x For the robot's end effector position, , φ It is a normal number.

2. The human-computer interaction online variable impedance compliant control method as described in claim 1, characterized in that: During acceleration, ; During deceleration, ; ； in, b c This is the default value for the damping parameter; ρ and These are adjustable parameters; The absolute value of the compensating force control law; m c This is the default quality setting.

3. The online variable impedance compliant control method for human-computer interaction as described in claim 1, characterized in that: The calculation model for the human-computer interaction force is as follows: ； in, f r It is the feedforward force of the human hand; B r These are the damping parameters of the human hand; K r These are the stiffness parameters of the human hand; , x d For the desired position; .

4. The human-computer interaction online variable impedance compliant control method as described in claim 1, characterized in that: The robot's main controller is: ； in, This provides a dynamic model of the robot, enabling position tracking. For speed compensation, error compensation is used to control the robot speed within an acceptable range; The compensating force control law is used to compensate for the human-computer interaction force.

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