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CN-122008312-A - Composite control method and system for gap-containing joint mechanical arm

CN122008312ACN 122008312 ACN122008312 ACN 122008312ACN-122008312-A

Abstract

The invention discloses a composite control method and a system for a gap-containing joint mechanical arm, which belong to the technical field of engineering equipment control, wherein a control boundary of a collision force feedforward module and a PD feedback module is defined based on a six-degree-of-freedom mechanical arm nonlinear dynamics model of a gap-containing joint by quantifying the coupling relation between joint gaps and collision forces, and a composite control structure of collision force feedforward compensation-PD feedback tracking is built based on the dynamics model, wherein the feedforward module acquires joint collision force signals in real time, calculates reverse compensation torque to offset disturbance of the nonlinear collision force to the mechanical arm motion in advance, the PD feedback module monitors joint position and posture deviation in real time and outputs tracking torque to accurately correct track errors, and the two layers of modules are nested and cooperated to work, so that the advantage of feedforward control of actively suppressing disturbance is played, steady-state accuracy of track tracking is ensured by PD feedback control, and the operation accuracy and reliability of the gap-containing joint mechanical arm are effectively improved.

Inventors

  • SUN XIUTING
  • FU YAODONG
  • XU JIAN

Assignees

  • 同济大学

Dates

Publication Date
20260512
Application Date
20260202

Claims (5)

  1. 1. A compound control method of a gap-containing joint mechanical arm is characterized by comprising the following steps of S101, constructing a nonlinear dynamics model of the system based on a six-degree-of-freedom mechanical arm with a gap joint, modeling the joint gap and the collision force of the mechanical arm, and determining the control boundary of a collision force feedforward module and a PD feedback module; S102, constructing a composite control structure of collision force feedforward compensation-PD feedback tracking based on the nonlinear dynamics model; and S103, based on the composite control structure, the joint position and the gesture of the mechanical arm are accurately tracked, the collision force disturbance caused by the clearance is compensated in real time, and the operation precision and the reliability of the mechanical arm are improved.
  2. 2. The composite control method of the mechanical arm with the gap joint according to claim 1, wherein the constructing a nonlinear dynamics model of the mechanical arm with the gap joint is specifically as follows: Defining the clearance vector as the difference between the bearing geometric center r ob and the sleeve geometric center r oj Eccentricity size The gap size is satisfied; (1); Wherein R b represents the bearing radius, R j represents the sleeve radius, and the contact deformation is Calculating normal collision force of the joint by adopting LANKARANI-NIKRAVESH model; (2); tangential friction is calculated by adopting a Stribeck model: (3); Where n=1.5 is a nonlinear coefficient, In order to achieve a contact deformation rate, Is the coefficient of static friction of the rubber belt, Is the coefficient of dynamic friction of the rubber belt, For the Stribeck speed threshold value, As a rule of thumb constant, In order to achieve a viscous coefficient of friction, The total collision force is as follows: (4); further establishing a gap-containing mechanical arm dynamics model: (5); Where q is the generalized coordinate, Represents a generalized velocity of the vehicle, Represents generalized acceleration, M is a mass matrix, C is a damping matrix, K is a stiffness matrix, F e is the generalized force to which the system is subjected, The constraint matrix of the system, F c , represents the collision force.
  3. 3. The composite control method of the gap-containing joint mechanical arm according to claim 1, wherein the composite control structure of the collision force feedforward compensation-PD feedback tracking is specifically as follows: the collision force feedforward compensation module is based on the collision force X-axis component Component of Y axis The center of mass coordinate (x b ,y b ) of the combined bearing, the center of mass coordinate (x i ,y j ) of the shaft sleeve and the compensation torque of the bearing at the gap hinge are calculated Compensation torque of shaft sleeve Total feedforward compensation torque And a PD control module for controlling the torque to be: ,(6); Wherein, the Representing the desired angle of the ith joint And the actual angle of the joint Error between the feedforward compensation torque and the feedback tracking torque, wherein K p is a proportional coefficient, K d is a differential coefficient, and total control torque is superposition of the feedforward compensation torque and the feedback tracking torque: (7)。
  4. 4. The method for compositely controlling the gap-containing joint mechanical arm according to claim 2, wherein the calculation of the contact stiffness coefficient K and the damping coefficient D in the LANKARANI-NIKRAVESH model is specifically as follows: coefficient of contact stiffness: (8); (9); (10); wherein v b and E b are the poisson's ratio and young's modulus of the bearing, and v j and E j are the poisson's ratio and young's modulus of the sleeve; Damping coefficient: (11); Wherein c e is the recovery factor taken to be 0.9, Is the initial collision velocity of the collision point.
  5. 5. A composite control system for a gap-containing articulated arm capable of implementing the method of any one of claims 1-4, comprising: The modeling module is used for constructing a non-linear dynamics model of the mechanical arm system with the gap joint based on the six-degree-of-freedom mechanical arm with the gap joint, wherein the model covers a joint gap kinematics model, a LANKARANI-NIKRAVESH collision force model, a Stribeck friction force model and a Lagrange dynamics equation of the mechanical arm system; the control structure construction module is used for constructing a composite control structure of 'collision force feedforward compensation-PD feedback tracking' based on a nonlinear dynamics model, and determining cooperative work logic of the feedforward module and the feedback module; a tracking and compensation module for calculating total control torque based on the composite control structure The joint position and the gesture of the mechanical arm are accurately tracked, and collision force disturbance caused by gaps is compensated in real time.

Description

Composite control method and system for gap-containing joint mechanical arm Technical Field The invention belongs to the technical field of engineering equipment control, and particularly relates to a composite control method and system combining collision force feedforward and PD feedback. Background In complex scenes such as industrial production, aerospace and the like, the six-degree-of-freedom mechanical arm is required to complete high-precision and high-stability operation tasks, and the joint performance directly determines the overall operation quality. However, during long-term load operation of the mechanical arm joint, the relative friction of the bearing and the shaft sleeve inevitably generates wear, thereby forming joint gaps. The gap can cause the problems of periodic vibration, shaking and the like when the mechanical arm operates, so that not only is the fatigue damage of joints increased and the service life of equipment shortened, but also strong nonlinear collision force can be induced, and the track error of the end effector is increased. From the state of the control technology, the existing control strategies for the gap-containing mechanical arm mainly comprise traditional PD control, self-adaptive control, robust control and the like. Although the traditional PD control is simple to realize, the dynamic characteristics such as nonlinearity, parameter perturbation and the like caused by gaps are difficult to deal with, the adaptive control has certain parameter adaptation capability, but is highly dependent on the modeling precision of the system, the control performance is obviously reduced when modeling errors exist, and the robust control can inhibit part of disturbance, but cannot accurately offset the source influence of collision force, so that the dynamic response speed and the steady-state precision are difficult to be simultaneously considered. At present, the core defects of the prior art are that the nonlinear characteristics of the collision force of joints are not fully considered, the control strategy is mostly single-target optimization, the cooperative design of disturbance suppression-precision tracking is lacked, the control parameter adaptation is delayed from the dynamic change of gaps, and the dynamic characteristic change of a system cannot be adapted in real time. Therefore, there is a need to design a composite control method with high accuracy, strong robustness and capability of adapting to gap uncertainty, so as to meet the requirement of stable operation of the gap-containing joint mechanical arm in complex scenes. Disclosure of Invention The invention aims to solve the problem that the prior art is difficult to cope with the defects of non-linear collision force, control precision and reliability of joint gaps, and provides a collision force feedforward-PD feedback composite control method and system suitable for a joint mechanical arm with gaps. In order to achieve the purpose, the invention is realized by adopting the following technical scheme: in one aspect, the present invention provides a method for controlling a gap-containing joint mechanical arm, comprising S101, constructing a nonlinear dynamics model of the system based on a six-degree-of-freedom mechanical arm with a gap joint, modeling the joint gap and the collision force of the mechanical arm, and determining the control boundary of a collision force feedforward module and a PD feedback module; S102, constructing a composite control structure of collision force feedforward compensation-PD feedback tracking based on the nonlinear dynamics model; and S103, based on the composite control structure, the joint position and the gesture of the mechanical arm are accurately tracked, the collision force disturbance caused by the clearance is compensated in real time, and the operation precision and the reliability of the mechanical arm are improved. Preferably, the constructing a mechanical arm nonlinear dynamics model containing a gap joint specifically comprises: Defining the clearance vector as the difference between the bearing geometric center r ob and the sleeve geometric center r ojEccentricity sizeThe gap size satisfies: (1); Wherein R b represents the bearing radius, R j represents the sleeve radius, and the contact deformation is And then, adopting LANKARANI-NIKRAVESH model to calculate the normal collision force of the joint: (2); tangential friction is calculated by adopting a Stribeck model: (3); Where n=1.5 is a nonlinear coefficient, In order to achieve a contact deformation rate,Is the coefficient of static friction of the rubber belt,Is the coefficient of dynamic friction of the rubber belt,For the Stribeck speed threshold value,As a rule of thumb constant,In order to achieve a viscous coefficient of friction,The total collision force is as follows: (4); further establishing a gap-containing mechanical arm dynamics model: (5); Where q is the generalized coordinate, Represents a gen