Abstract
The tethered space robot (TSR) is a new concept of space robot which consists of a robot platform, space tether and operation robot. This paper presents a multi-objective optimal trajectory planning and a coordinated tracking control scheme for TSR based on velocity impulse in the approaching phase. Both total velocity impulse and flight time are included in this optimization. The non-dominated sorting genetic algorithm is employed to obtain the optimal trajectory Pareto solution using the TSR dynamic model and optimal trajectory planning model. The coordinated tracking control scheme utilizes optimal velocity impulse. Furthermore, the PID controller is designed in order to compensate for the distance measurement errors. The PID control force is optimized and distributed to thrusters and the space tether using a simulated annealing algorithm. The attitude interferential torque of the space tether is compensated a using time-delay algorithm through reaction wheels. The simulation results show that the multi-objective optimal trajectory planning method can reveal the relationships among flight time, fuel consumption, planar view angle and velocity impulse number. This method can provide a series of optimal trajectory according to a number of special tasks. The coordinated control scheme can significantly save thruster fuel for tracking the optimal trajectory, restrain the attitude interferential torque produced by space tether and maintain the relative attitude stability of the operation robot.
Highlights
With the development of space technology, the number of satellites increases dramatically
The interferential torque produced by the space tether is stabilized using the attitude stability method based on a time-delay algorithm through reaction wheels in the interim
This paper studies a multi-objective optimal trajectory planning method based on velocity impulses using an non-dominated sorting genetic algorithm (NSGA)-2 algorithm
Summary
With the development of space technology, the number of satellites increases dramatically. To save the fuel of the operation robot, this paper presents a coordinated orbit and attitude control method for tracking the optimal trajectory. Mori proposed the concept of tethered satellite cluster systems whose parts were connected by tethers He established a coordinated control method using tension force and thrust force, which decreased thruster fuel and improved control precision [12]. The TSR is similar in concept to the above researches, which mention the coordinated control method; they only considered one aspect, such as orbit movement or attitude change. This paper presents an optimal trajectory of an operation robot for approaching the target based on the multiobjective velocity impulse method. To economize the thrust fuel of operation robot, we present a coordinated orbit control and attitude stability method for tracking the optimal approach trajectory. The numerical results of the optimal trajectory and the coordinated control method are plotted in Section V, and conclusions are given at the end
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