CN-116244928-B - Variable-stiffness joint external force estimation method and device

CN116244928BCN 116244928 BCN116244928 BCN 116244928BCN-116244928-B

Abstract

The invention provides a variable stiffness joint external force estimation method and device, which comprise the steps of obtaining stiffness values in real time, substituting the obtained stiffness values into an adaptive fusion coefficient model to be resolved, obtaining an adaptive fusion coefficient, obtaining external force estimation I based on current information of a variable stiffness joint, obtaining external force estimation II based on elastic deformation information and stiffness values of the variable stiffness joint, and obtaining an external force estimation value based on fusion of the current and the elastic deformation information based on the adaptive fusion coefficient, the external force estimation I and the external force estimation II. According to the invention, the information of both current and elastic deformation is fused in the external force estimation process, so that the external force estimation effect under dynamic and quasi-static rigidity is improved, and the method is suitable for a variable rigidity joint system requiring high-precision external force estimation under a force interaction scene.

Inventors

NING YINGHAO
FAN LI
LI DONG
ZENG BO
YANG RONGCHAO
MIAO QIAN
ZHANG QING
ZHAO HANG
ZHANG PENGFEI
SHI ZHANDONG
YU QIANYUAN

Assignees

中国烟草总公司郑州烟草研究院

Dates

Publication Date: 20260508
Application Date: 20230118

Claims (10)

1. The method for estimating the external force of the variable-stiffness joint is characterized by comprising the following steps of: acquiring a rigidity value in real time; Substituting the obtained rigidity value into an adaptive fusion coefficient model to perform resolving to obtain an adaptive fusion coefficient, wherein the adaptive fusion coefficient model is as follows: Wherein, the Representing joint stiffness Is used to determine the absolute value of the derivative of (c), And All are normal numbers, satisfy ; Acquiring external force estimation I based on current information of the variable stiffness joint; acquiring external force estimation II based on the elastic deformation information and the rigidity value of the rigidity-variable joint; based on the self-adaptive fusion coefficient, the external force estimation I and the external force estimation II, obtaining an external force estimation value based on fusion of current and elastic deformation information: Wherein, the The I is estimated for the external force, The estimate II is made for the external force, Is an adaptive fusion coefficient.
2. The method for estimating external force of a variable stiffness joint according to claim 1, wherein the expression of the external force estimation II is: Wherein, the The value of the stiffness is indicated, As a variable of the stiffness of the steel, Indicating elastic deformation of the joint interior.
3. The method for estimating external force of a variable stiffness joint according to claim 1, wherein the obtaining the external force estimate I based on the current information of the variable stiffness joint comprises: establishing a dynamic model of the position driving module and the rigidity adjusting module: Wherein, the And The rotational inertia of the position driving module and the rigidity adjusting module are respectively represented; And Respectively representing the friction force of the position driving module and the rigidity adjusting module; And Output moments of the position driving module and the rigidity adjusting module are respectively represented; And Input moments of the position driving module and the rigidity adjusting module are respectively represented; And Respectively representing the output angular displacement of the position driving module and the rigidity adjusting module; acquiring moment of inertia in dynamic model by dynamic parameter identification method 、 And friction force 、 Is an accurate value of (2); Measuring current information of position motor and rigidity adjusting motor And The input torque of the position drive module and the stiffness adjustment module is calculated according to the following formula: Wherein, the And Respectively representing the total moment constants of the position driving module and the rigidity adjusting module; substituting the calculated input torques of the position driving module and the rigidity adjusting module into dynamic models of the position driving module and the rigidity adjusting module to calculate so as to obtain output torques of the position driving module and the rigidity adjusting module; calculating the sum of output moments of the position driving module and the rigidity adjusting module as an external force estimation I: 。
4. the method for estimating external force of a variable stiffness joint according to claim 1, wherein the step of acquiring the stiffness value in real time comprises the steps of: Designing a rigidity area controller, and calculating a rigidity variable expected value based on the external force estimated value and the maximum external moment constraint at the previous moment; the expected value of the rigidity variable is acted on the motion control of the rigidity adjusting motor, and the actual value of the rigidity variable is obtained; Substituting the actual value of the rigidity variable into a rigidity model to obtain an updated rigidity value, wherein the rigidity model is a function of the rigidity variable.
5. The method of claim 4, wherein when the variable stiffness joint is a lever type variable stiffness joint, the designing stiffness region controller calculates a stiffness variable expected value based on the external force estimated value and a maximum external moment constraint at the previous time, comprising: (1) Designing a stiffness region controller based on the lyapunov barrier function; For a lever-type variable stiffness joint, the lyapunov barrier function for the stiffness region controller is expressed as: Wherein, the The variables of the function are represented and, ; 、、 Are all normal numbers and satisfy , ; Representing the estimated external torque; Representing a particular stiffness variable Maximum allowable external moment of lower joint and rigidity variable Related to; the range of the values is as follows ; (2) Dividing rigidity adjustment into three areas, namely a rigidity increasing area, a rigidity reducing area and a constant rigidity area, based on a Lyapunov barrier function; (3) The derivative of the lyapunov barrier function is expressed as: (4) Is properly designed Make it meet To ensure that In the region of constant stiffness of the device, The expression of (2) is: Wherein, the To express the constant of the speed of the rigidity of the lever type rigidity-variable joint from the rigidity increasing area or the rigidity decreasing area to the constant rigidity area, and Greater than 0; (5) According to Definition of (2) will The derivative of (2) is expressed as: Wherein, the Representing lever-type variable stiffness joint stiffness variable Is a derivative of (2); (6) After further finishing, obtain Is represented by the expression: 。
6. the method for estimating an external force of a joint with variable stiffness as defined in claim 5, wherein the parameters of the Lyapunov barrier function are used when the stiffness adjustment is divided into three regions based on the Lyapunov barrier function ; When (when) When the rigidity is increased, the rigidity is increased; When (when) In the case of a reduced stiffness region; When (when) And is a constant stiffness region.
7. A variable stiffness joint external force estimation device, comprising: The rigidity acquisition module is configured to acquire a rigidity value in real time; the external force estimation I acquisition module is configured to acquire external force estimation I based on current information of the variable stiffness joint; the external force estimation II acquisition module is configured to acquire external force estimation II based on the elastic deformation information and the rigidity value of the variable-rigidity joint; the self-adaptive fusion coefficient model is used for obtaining updated rigidity values based on the rigidity variable actual values, wherein the self-adaptive fusion coefficient model is used for: Wherein, the Representing joint stiffness Is used to determine the absolute value of the derivative of (c), And All are normal numbers, satisfy ; The fusion module is used for obtaining an external force estimated value based on fusion of current and elastic deformation information based on the self-adaptive fusion coefficient, the external force estimated I and the external force estimated II: Wherein, the The I is estimated for the external force, The estimate II is made for the external force, Is an adaptive fusion coefficient.
8. The variable stiffness joint external force estimation device according to claim 7, wherein the external force estimation II has the expression: Wherein, the The value of the stiffness is indicated, As a variable of the stiffness of the steel, Indicating elastic deformation of the joint interior.
9. The variable stiffness joint external force estimation device according to claim 7, wherein the stiffness acquisition module includes: The rigidity variable expected value calculation module is configured to design a rigidity area controller and calculate a rigidity variable expected value based on the external force estimated value and the maximum external moment constraint at the last moment; the rigidity variable actual value acquisition module is configured to act the rigidity variable expected value on the motion control of the rigidity adjusting motor to obtain the rigidity variable actual value; and the rigidity model is configured to obtain updated rigidity numerical values based on the actual values of the rigidity variables, wherein the rigidity model is a function of the rigidity variables.
10. The variable stiffness joint external force estimation device according to claim 7, wherein the external force estimation I acquisition module comprises: the dynamic model construction module is configured to establish a dynamic model of the position driving module and the rigidity adjusting module: Wherein, the And The rotational inertia of the position driving module and the rigidity adjusting module are respectively represented; And Respectively representing the friction force of the position driving module and the rigidity adjusting module; And Output moments of the position driving module and the rigidity adjusting module are respectively represented; And Input moments of the position driving module and the rigidity adjusting module are respectively represented; And Respectively representing the output angular displacement of the position driving module and the rigidity adjusting module; the parameter identification module is configured to acquire the moment of inertia in the dynamic model through a dynamic parameter identification method 、 And friction force 、 Is an accurate value of (2); an external force calculation module configured to adjust current information of the motor based on the measured position and stiffness of the motor And The input torque of the position drive module and the stiffness adjustment module is calculated using the following formulas: Wherein, the And Respectively representing the total moment constants of the position driving module and the rigidity adjusting module; The output torque calculation module is configured to substitute the calculated input torques of the position driving module and the rigidity adjustment module into the dynamic models of the position driving module and the rigidity adjustment module to be calculated, so as to obtain the output torques of the position driving module and the rigidity adjustment module; and calculating the sum of the output moments of the position driving module and the rigidity adjusting module as an external force estimation I: 。

Description

Variable-stiffness joint external force estimation method and device Technical Field The invention belongs to the technical field of robots, and particularly relates to a variable stiffness joint external force estimation method and device. Background The rigidity-variable joint has flexibility and is widely applied to the scene of robot interaction with the surrounding environment. In complex interaction tasks, high-precision external force sensing is an important development direction in the future. Traditional external force sensing is mainly realized through an external force sensor, however, the external force sensor has high cost and is limited by complex structures, additional installation space and the like, and the application of the external force sensor is limited. In recent years, external force sensing methods other than force sensors have been developed. Chinese patent 201410112717.5 discloses a mechanical arm external force estimation method based on H ∞ filtering, deduces a dynamic model without acceleration, regards external force as a state variable of a state space equation, and realizes external force estimation based on H ∞ filtering. Chinese patent 202210279718.3 discloses a mechanical arm tactile external force estimation method based on a mechanism data hybrid model, which estimates external force based on current information, and utilizes a supervision statistical learning method of Gaussian process regression to train an unmodeled residual dynamic model compensation term based on a dataset so as to compensate unknown disturbance. China patent 202210207511.5 discloses a robot external force estimation method and system based on the optimization of the position jacobian condition number, which uses a generalized momentum observer to estimate the external force applied to a robot, and improves the external force estimation precision of the observer through accurate modeling of friction force, screens the position of the robot based on the optimization of the position jacobian condition number, and suppresses the influence of joint moment noise and modeling errors on the external force estimation. However, external force estimation based on current information requires an accurate dynamic model, and for a variable stiffness joint, the dynamic model adopts a dual-drive configuration form of a position motor and a stiffness adjusting motor, and the external force estimation effect is restricted by the complexity of the dynamic model and the dynamic unmodeled residual part. Because the variable-stiffness joint has internal flexibility, external force can be estimated by detecting the elastic deformation in the joint, but the method has a good external force estimation effect under quasi-static stiffness, and the external force estimation effect is often poor under dynamic stiffness. In addition, for lever type variable stiffness joints, the maximum allowable external moment of the joint is different under different rigidities, and neglecting the factor can lead to saturated output of the detection moment. Therefore, how to realize high-precision external force estimation of the variable stiffness joint is a problem to be solved. Disclosure of Invention Aiming at the defects of the prior art, the invention provides a variable stiffness joint external force estimation method and device, which can realize high-precision external force estimation in a variable stiffness joint system. The present invention achieves the above technical object by the following means. The first aspect of the invention provides a variable stiffness joint external force estimation method, which comprises the following steps: acquiring a rigidity value in real time; Substituting the obtained rigidity value into an adaptive fusion coefficient model to perform resolving to obtain an adaptive fusion coefficient, wherein the adaptive fusion coefficient model is as follows: Wherein, the The absolute value of the derivative K of the joint rigidity is represented, and R w1 and R w2 are normal numbers and meet R w2＞Rw1; acquiring external force estimation I based on current information of the variable stiffness joint; acquiring external force estimation II based on the elastic deformation information and the rigidity value of the rigidity-variable joint; based on the self-adaptive fusion coefficient, the external force estimation I and the external force estimation II, obtaining an external force estimation value based on fusion of current and elastic deformation information: τq＝Kττei+(1-Kτ)τec wherein τ ei is external force estimation I, τ ec is external force estimation II, and K τ is an adaptive fusion coefficient. In one embodiment of the first aspect, the step of obtaining the stiffness value in real time is as follows: Designing a rigidity area controller, and calculating a rigidity variable expected value based on the external force estimated value and the maximum external moment constraint at the previous moment; t