Research On Sliding Mode Control Method For Spacecraft Relative Motion

As the first series of commemorative banknotes issued, study on space field and space technology has become increasingly important. Meanwhile, the aerospace activities get more frequency in China. When the country is about to launch Long March-7, Tiangong-2, Shenzhou-11 and is going to implement Chang’e-5, as well as Chinese space station will be put into use, the research for spacecraft relative motion has a great time significance.Firstly, this paper presents the research status of space filed and sliding mode control. Then, the dynamic model of relative motion and the theory of sliding mode control are investigated. Besides, the method of sliding mode control to quickly respond to the input transformation is one of the advantages of their own and has good robustness. This article utilize the method of sliding mode control to determine a switching function and control law. And a sliding mode controller for the relative motion of spacecrafts in a near-circular orbit without disturbance is designed to drive the tracking spacecrafts to follow the expected track status in finite time. A stability analysis provides the sufficient conditions for the asymptotic stability of the switching function and control law by the theorem of Lyapunov. What’s more, the external disturbance factors for spacecrafts relative motion are considered. In order to guarantee the effectiveness of the sliding mode controller, a disturbance observer which supervises the disturbance in real time is introduced to acquire the disturbance value for real-time compensating the desired control inputs. In other words, a sliding mode controller for spacecrafts relative motion based on disturbance observer is designed. Fanally, simulation studies are clarified the effectiveness of the methoeds under the background of the spacecrafts rendezvous.