Dual Fuzzy Sliding Mode Control of Collaborative Robot Based on Adaptive Algorithm

The six-degree-of-freedom collaborative robot is a kind of nonlinear system with multiple inputs and multiple outputs, parameter uncertainty, external disturbance and unmodeled characteristics of the system. Changes in information and parameters adversely affect the operation of the robotic arm. Sliding mode variable structure control is very good enough to suppress the influence of external disturbance and internal disturbance on the stability of the system itself. Based on this, an adaptive fuzzy sliding mode controller based on exponential reaching law is designed in this paper, which adaptively estimates the uncertain upper bound of disturbance, and deduces the controller step by step, which can well eliminate the chattering problem of the control law. However, it did not solve the problem that the overall adjustment time of the control system was too long, and the performance of the control system on the control index of "rapidity" was not very good. Then a double fuzzy sliding mode control algorithm is designed, and the experiment proves that this scheme has higher tracking accuracy than the ordinary sliding mode control scheme. It greatly improves the robustness to external disturbances, system uncertain information and parameter changes.

I. Introduction

After more than 50 years of development, sliding mode variable structure control has formed a relatively independent research branch, which is very suitable for the time-varying, strongly coupled multi-input and multi-output nonlinear system control of cooperative six-degree-of-freedom robots [1]. In [2], the terminal sliding mode control algorithm considering nonlinear terms is applied to the tracking control of collaborative robots, which shows its superiority in the control of nonlinear systems. Literature [3] designed a non-singular terminal sliding mode surface, based on which the third-order sliding mode finite-time attitude control law was obtained; Literature [4] studies an adaptive fast terminal sliding mode control algorithm combined with global sliding mode. It ensures that the system tends to a sliding stable state within a limited time; Literature [5] proposed an integral terminal sliding mode controller to realize the tracking control of collaborative robots; Literature [6] uses a fuzzy logic system to compensate for unknown uncertainties in the system. Then, the terminal sliding modal surface is designed using the adaptive backstepping method. Thus, a variable structure controller with both robust and adaptive properties is obtained; Literature [7] uses the sliding mode control algorithm to realize the linear pose tracking control of the collaborative robot in the two-dimensional plane; Literature [8] designed a single-constant sliding mode controller and introduced a disturbance observer to control the multi-degree-of-freedom collaborative robot to achieve better control effects; Literature [9] combines sliding mode control and feedback linearization control to design a feedback linearization collaborative robot pose tracking control strategy; Literature [10] proposed a sliding mode variable structure control algorithm with a time-varying boundary layer, which not only weakens chattering and improves the robustness of the system, but also further improves the accuracy of trajectory tracking control; Literature [11] designed a sliding mode controller based on exponential approach rate. At the same time, the chattering problem caused by the sliding mode variable structure controller was weakened by introducing a saturation function and an adaptive adjustment algorithm, and the steady-state tracking error of the trajectory tracking was improved. Metrics such as tracking adjustment time have also been greatly improved.