Finite time convergence sliding mode control method combined with robust precise differentiator for conveying parallel robot

Abstract

The invention discloses a finite time convergence sliding mode control method combined with a robust precise differentiator for a conveying parallel robot. Kinematic analysis is carried out on the conveying parallel robot, and an expected movement track is given; a dynamic model of the conveying parallel robot containing unknown dynamics, external interference, friction and other uncertain factorsis timely acquired on line by adopting a time delay estimation technology; a finite time convergence robust accurate differentiator of a conveying parallel robot system is designed for observation aiming at a time delay estimation error generated by the time delay estimation technology; furthermore, a finite time convergence sliding mode controller is designed based on the feedforward compensation effect of a time delay estimation error observation value; and through software programming, finite time convergence sliding mode control combined with a robust precise differentiator feedforward compensation technology for the conveying parallel robot is realized. The finite time convergence sliding mode control method combined with the robust precise differentiator for the conveying parallel robot has a remarkable inhibition effect on buffeting of sliding mode control, and the sliding mode variable and the derivative thereof are converged to the original point within finite time, so that the motion tracking precision is improved.

Description

technical field [0001] The invention relates to a parallel robot for transportation, in particular to a model-free combined robust precise differentiator finite-time convergent sliding mode control method for a parallel robot for transportation. Background technique [0002] In order to meet the engineering application requirements of automotive coating conveying equipment, a parallel robot for conveying was developed based on a parallel mechanism to overcome the lack of carrying capacity and low flexibility of the existing automotive electrophoretic coating conveying equipment that adopts a cantilever beam series structure defect. The parallel robot for transportation has many advantages such as strong carrying capacity, wide applicability of vehicle models, high positioning accuracy, small motion inertia of the end member, no cumulative error, and fast response speed. However, the characteristics of the multi-branch closed-chain structure and the coupling relationship bet...

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Problems solved by technology

There are two disadvantages in this method: (1) the control method needs to establish the dynamic model of the parallel robot first, which requires a large amount of calculation; (2) the control law of the approaching law sliding mode control has a discontinuous sign function, which leads to the failure of the sliding mode control. Chattering

This method has the following disadvantages: (1) The control method directly uses sliding mode control to overcome the influence of uncertain factors such as time delay estimation errors, resulting in a large amount of control required, and a large switching gain is easy to aggravate the chattering of sliding mode control; ( 2) This control method introduces an adaptive rule to adjust the control switching gain, but since the obtained sliding mode control law is still discontinuous, the ability to suppress chattering in sliding mode control is limited, and the adaptive parameters are not easy to adjust in practical applications

(3) This control method belongs to the first-order sliding mode control, which can only guarantee the convergence of the sliding mode variables

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