Space tether system unfolding control method based on nonlinear model predictive control

Abstract

The invention provides a stability control method for unfolding of a three-dimensional space tether system operating in a low earth elliptical orbit in an initial stage. A tether is released to a desired length and the swing of the tether is restrained only by adjusting the limited tether tension without relying on other thrusters. The method comprises the following steps that S1, a two-body spacetether system dynamic model considering tether mass is established; S2, under the conditions such as disturbance, uncertainty, underactuation, restricted tether swing angle and tether tension, basedon a nonlinear model predictive control (NMPC) algorithm, a pseudo-spectral algorithm is used for discretizing an original nonlinear model, and an open loop optimal problem in predictive control is transformed into a nonlinear programming problem for solving; and S3, according to the solution of the nonlinear programming problem, the control quantity of the next control period is determined to form the closed-loop control. Finally, the three-dimensional space tether system operating in the low earth elliptical orbit is stably released and unfolded in the initial stage.

Description

technical field [0001] The invention relates to a method for controlling deployment of a space tether system, and belongs to the technical field of space tether system applications. Background technique [0002] The space tether system refers to a combination of man-made space objects that are connected together by tethers to complete in-orbit flight. The tether is connected to another aircraft with a larger mass (the main star), forming a space combination of the main star-tether-sub-star. The main star can be a variety of space vehicles such as satellites, spaceships, space shuttles, and space stations, or even abandoned final-stage launch vehicles; the sub-stars can be small satellites, return capsules, and micro-probes. [0003] The complex space tether system is composed of multiple space objects, and they are connected into closed loops, trees or polyhedrons with tethers. The space tether system is a new type of structure built by people in space, which can complete ...

AI Technical Summary

Problems solved by technology

[0004] Because the space tether deployment control system is affected by space perturbation, it is very easy to generate complex tether vibration problems. At the same time, the system is not only a nonlinear, typical underactuated system, but also subject to some physical constraints, such as the pulling force is always positive and has an upper limit. , these bring difficulties to the design of the controller

Images