Research on Adaptive Reaction Null Space Planning and Control Strategy Based on VFF–RLS and SSADE–ELM algorithm for Free-Floating Space Robot

Ye Ye,Dong Dong,Hong Hong

doi:10.3390/electronics8101111

Abstract

With the increase of on-orbit maintenance and support requirements, the application of a space manipulator is becoming more promising. In actual operation, the strong coupling of the free-floating space robot itself and the unknown disturbance of the contact target caused a major challenge to the robot base posture control. Traditional Reaction Null Space (RNS) motion planning and control methods require the construction of precise dynamic models, which is impossible in reality. In order to solve this problem, this paper proposes a new Adaptive Reaction Null Space (ARNS) path planning and control strategy for the contact of free-floating space robots with unknown targets. The ARNS path planning strategy is constructed by the Variable Forgetting Factor Recursive Least Squares (VFF–RLS) algorithm. At the same time, a robust adaptive control strategy based on the Strategy Self-Adaption Differential Evolution–Extreme Learning Machine (SSADE–ELM) algorithm is proposed to track the dynamic changes of the planned path. The algorithm enables us to intelligently learn and compensate for the unknown disturbance. Then, this paper constructs a robust controller to compensate model uncertainty. A striking feature of the proposed strategy is that it does not require an accurate system model or any information about unknown attributes. This design can dynamically implement RNS path tracking performance. Finally, through simulation and experiment, the proposed algorithm is compared with the existing methods to prove its effectiveness and superiority.

Highlights

Nowadays, with the increasing frequency of space activities, the impact of spacecraft being hit by space debris has increased
This paper proposes an Adaptive Reaction Null Space (ARNS)
The Strategy Self-Adaptation Differential Evolution (SSADE)–Extreme Learning Machine (ELM) algorithm proposed in this paper is compared with the adaptive control algorithm based on ELM and the POS–ELM control algorithm proposed in Reference [21]

Summary

Introduction

With the increasing frequency of space activities, the impact of spacecraft being hit by space debris has increased. A large amount of space debris has already seriously threatened the safety of on-orbit spacecraft. By a large number of large-scale space debris, they may change the attitude and orbit of the spacecraft and even cause the spacecraft to be completely destroyed [1]. In order to solve such problems, the development of space debris removal technology has become urgent. Among the many active space removal technologies, the technology of space manipulator removal in the orbit has received extensive attention. The ETS–VII of Japan, the Orbital Express of the United States, and the SY-7 of China have successively conducted verification experiments on this technology in space, and are still intensifying their research [2,3]

Results

Discussion

Conclusion