Adaptive fixed-time trajectory tracking control for Mars entry vehicle
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ORIGINAL PAPER
Adaptive fixed-time trajectory tracking control for Mars entry vehicle Ganghui Shen · Yuanqing Xia · Jinhui Zhang · Bing Cui
Received: 13 July 2020 / Accepted: 11 November 2020 © Springer Nature B.V. 2020
Abstract This paper develops a fixed-time trajectory tracking control scheme for Mars entry vehicle under uncertainty. First, a novel fixed-time nonsingular terminal sliding mode (FTNTSM) surface with bounded convergence time independent on the initial conditions is developed, which not only averts the singularity problem but also assures fast convergence. Second, based on the FTNTSM surface and adaptive technique, a continuous adaptive fixed-time nonsingular terminal sliding mode control (AFTNTSMC) method is proposed. Under the control scheme, the fixed-time convergence of tracking error is assured, and the chattering phenomenon is alleviated. Furthermore, by estimating the square of upper bound of the uncertainty, the designed AFTNTSMC method averts the use of boundary layer technique as imposed in most existing literature on adaptive fixed-time control. The effectiveness of the developed control approach is confirmed by numerical simulations. Keywords Fixed-time control · Nonsingular terminal sliding mode · Adaptive control · Mars entry trajectory tracking
G. Shen · Y. Xia · J. Zhang (B) · B. Cui School of Automation, Beijing Institute of Technology, Beijing 100081, China e-mail: [email protected]
1 Introduction With the progress of science and technology, the pinpoint Mars landing becomes necessary requirement for next-generation Mars exploration mission [1–3]. Mars landing process is mainly composed of three phases including entry, descent and landing (EDL). During Mars landing process, entry phase from atmospheric interface to parachute deployment is a vital stage for the entire mission, and entry guidance method is pivotal in Mars accurate landing [4]. Generally, entry phase is subject to uncertainties and parameter perturbations which are main error sources resulting in large landing dispersions. Therefore, to improve Mars landing accuracy under large uncertainties, some valid strategies should be investigated for Mars entry guidance. Broadly speaking, entry guidance strategies are segmented into two categories: predictor-corrector approach and reference trajectory tracking method [5– 7]. A performance comparison between the above two guidance strategies is carried out in [4], whose results reveal that trajectory tracking method is more appropriate for Mars entry guidance. As a result, numerous control schemes have been used to handle the trajectory tracking problem, such as feedback linearization [3], incremental nonlinear dynamic inversion (INDI) [5], model predictive control (MPC) [8], and sliding mode control (SMC) [9]. Although the controllers mentioned above can improve guidance precision under uncertainties, they merely achieve asymptotic convergence.
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Considering that Mars entry phase lasts a short time, finite-time convergence is an indispensable feature
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