Finite time control for probe descent near small bodies

Chunhun Liang^{1, 2}, Yuanchun Li^{1, 3} 

¹College of Communication Engineering, Jilin University, 130012, Changchun, China

²College of Electrical and Information, Changchun Institute of Technology, 130012, Changchun, China

³Department of Control Engineering, Changchun University of Technology, 130012, Changchun, China

For the purpose of probe soft landing on small bodies safely, this paper focuses on the orbital dynamics and describes a new control algorithm for the probe descent near a rotating small body. The general formulation of the probe equations of motion in the Body-Fixed Coordinate system is obtained through Newton’s second law firstly. Then the nominal polynomial trajectory of vertical direction is planned in the condition of fuel consumption suboptimum. Considering uncertainties and perturbations, the control laws based on Adaptive Terminal Sliding Mode with compensation term are developed to track the desired trajectory finally. Suppose the initial conditions presented in this paper, position and velocity errors tend to zero in the finite time in the phase of sliding mode motion so it will make the task succeed during descent phase near small bodies. Finally, the effectiveness of the guidance and control algorithm is verified by MATLAB simulations. The proposed algorithm can fast and accurately track the planned trajectory in the finite time and is robust to parameter uncertainty, feedback state error and external disturbances. The validity is conformed by computer simulation.