Synchronous Robust Sliding Mode Control of a Parallel Robot for Automobile Electro-Coating Conveying

Abstract

This paper is devoted to improving the synchronization and robustness performance of a parallel robot used for automobile electro-coating conveying via a novel synchronous robust sliding mode control (SMC). A sliding surface is designed based on a composite error, which is composed of the tracking error of each joint and the synchronization errors among the joints. By incorporating a nonlinear disturbance observer into the finite-time SMC based on the composite error, the synchronous robust SMC of the parallel robot is realized. The finite-time Lyapunov stability of the sliding variable and the asymptotic convergence of the tracking error and synchronization error have been proved theoretically. The lumped disturbance in the system is estimated by the proposed scheme, and restriction on the change rate of the lumped disturbance has been relaxed. Due to the feedforward compensation with the disturbance estimation value, the switching gain of SMC required is merely larger than the upper bound of the disturbance estimation error, rather than the upper bound of the disturbance, resulting in chattering attenuation. Finally, the numerical simulation and experiment on the prototype system of the parallel robot are implemented to validate the effectiveness of the synchronous robust SMC.

Screw Dynamic Modeling and Novel Composite Error-Based Second-order Sliding Mode Dynamic Control for a Bilaterally Symmetrical Hybrid Robot

“…Among the previous researches of our group, the combination of synchronous control theory and SMC theory has been raised to conquer the trajectory tracking problem and the synchronization problem concurrently. [36][37][38] Ref. [36] defines a coupling error by combining tracking errors of the active joints with synchronization errors among the joints and proposes a coupling error-based reaching law SMC method.…”

“…Ref. [38] defines a composite error, and the synchronous robust SMC of the hybrid robot is realized by combining a nonlinear disturbance observer with the finite-time SMC based on the composite error. From the above works in Refs.…”

“…From the above works in Refs. [36][37][38], the uncertainty problems could be conquered and the synchronization among active joints could be guaranteed simultaneously, whereas the slow convergence rate problem still exists in the SMC methods mentioned above; moreover, for the bilaterally symmetrical hybrid robot involved in this paper, the aforementioned synchronization errors which merely consider synchronization errors among the active joints could not ensure the synchronization performance of the hybrid robot end-effector. The chief reasons are that bilateral walking mechanisms may be asynchronous and the motion transfer error exists from the active joints to the robot end-effector.…”

Finite-Time Dynamic Tracking Control of Parallel Robots with Uncertainties and Input Saturation

“…Due to the mechanical properties of strong carrying capacity, high precision and fast response speed, parallel robots exhibit outstanding performance in various applications, e.g., industry, agriculture, medical equipment [ 1 , 2 , 3 ]. However, the system complexity, purposeful simplification of the system dynamics and circumstance variations introduce uncertainties to the dynamic control of parallel robots, such as modeling errors, friction and external disturbance, all of which can be defined as the lumped disturbance.…”

Pose detection of parallel robot based on improved Hough‐K‐means and SURF algorithms

“…The existing electrocoating conveying robots, such as RoDip robot and Vario‐shuttle robot, are not suitable for the electrocoating conveying of heavy vehicle body due to the complex structure, high requirement of manufacturing and installation, and cantilever beam structure of robots. Therefore, our team develops a novel auto electrocoating conveying parallel robot [1]. Accurate and rapid pose detection of robot can effectively reduce the pose error caused by the kinematics model solution, and further realise the high‐performance closed‐loop motion control of electrocoating conveying robot [2–5].…”