Adaptive trajectory tracking control of a free-flying space robot subject to input nonlinearities
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(2020) 42:574
TECHNICAL PAPER
Adaptive trajectory tracking control of a free‑flying space robot subject to input nonlinearities Qijia Yao1 Received: 15 May 2020 / Accepted: 28 September 2020 © The Brazilian Society of Mechanical Sciences and Engineering 2020
Abstract The input nonlinearities widely exist in a large range of mechanical systems. Nonetheless, they were relatively less considered in the trajectory tracking control of a space robot in the previous studies. In this paper, an adaptive neural network (NN) control method is proposed for the fast and exact trajectory tracking control of an attitude-controlled free-flying space robot subject to input nonlinearities. The parametric uncertainties and external disturbances are also taken into the consideration. First, a model-based controller is designed to track the desired trajectory of the space robot within a framework of backstepping technique. Then, an adaptive NN controller is designed by using two NNs to compensate for the lumped uncertainties caused by parametric uncertainties and external disturbances and the input nonlinearities, respectively. Rigorous theoretical analysis for the semiglobal uniform ultimate boundedness of the whole closed-loop system is provided. The proposed adaptive NN controller is structurally simple and model-independent, which makes the controller affordable for practical applications. In addition, the proposed adaptive NN controller can guarantee the position and velocity tracking errors converge to the small neighborhoods about zero even in the presence of parametric uncertainties, external disturbances, and input nonlinearities. To the best of the authors’ knowledge, there are really limited existing controllers can achieve such excellent performance in the same conditions. Numerical simulations illustrate the effectiveness and superiority of the proposed control method. Keywords Trajectory tracking control · Space robot · Input nonlinearity · Neural network · Adaptive control
1 Introduction Space robot is considered as one of the most promising technologies for future space activities owing to its important role in on-orbit servicing and active debris removal [1–3]. The purpose of on-orbit servicing is to prolong the service lifetime of satellites through refueling, repairing, and component replacement. Graham and Kingston [4] analyzed the commercial viability of various on-orbit servicing missions. The objective of active debris removal is to clean up large space debris in low earth orbit (LEO). Ref. [5] shows that the active debris removal can effectively control the growth of space debris populations in LEO. Smahat et al.
Technical Editor: Jader Barbosa. * Qijia Yao [email protected] 1
School of Aerospace Engineering, Beijing Institute of Technology, Beijing 100081, China
[6] investigated the mechanical behavior of debris impact on spacecraft structure at hyper-high velocity. Since the early 1990s, some robotic demonstration experiments have been conducted with success, such as Robot Technology Experiment (RO
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