Research On Modeling And Control For Space Robot System With Gravity Effect Consideration

Space robot is researched and developed on the ground but it serves in the space. Themotion behavior of space robot varies due to the changes of gravity and the physicalprocess affected by gravity. How to cope with the differences of motion behavior causedby different mechanical effect on the ground and in the space is one of the most importantproblems for the control system. Microgravity simulation test is the main research andverification means resulting from the actual space engineering accident caused by thisproblem. However, the existing microgravity simulation method is only effective for a fewtypes of object and task in limited precision scale. Many cases of on-orbit test show thatthe dynamics experiments of manipulation in the simulation environment on the groundhas a larger difference than on the orbit.The previous control strategies were designed based on space model, withoutconsidering the change of model caused by the changes of the gravity environment. Therealization of the expected control performance and running accuracy depended on theground microgravity simulation system. But the fidelity of the existing microgravitysimulation was limited, which can easily cause or cover up the possible fault in the realoperating environment, and can’t provide the reliable guarantee for the effective validationof the control strategy. High precision and complex space mechanism is highly sensitive tothe variation of gravity. This problem will become more prominent, and harder to avoid.Therefore, the free floating space robot with series configuration, the space stationdexterous manipulator with hybrid configuration and the spacecraft with complexstructure were selected as the research objects, and the modeling method of system underdifferent gravity environment, the control strategy with adaptive ability on the change ofthe gravity environment, and the chaos of system were studied, the research contents andresults are as follows:Firstly, low computational modeling method of aerospace engineering was carriedout. Based on screw theory, the dynamical models of free-floating space robot with seriesconfiguration and space station dexterous robotic manipulator with hybrid configurationunder different gravity condition were set up by combining with the conservation of momentum theorem and Lie groups and Lie algebra. Focusing on common inversesolution of redundant of the space station dexterous manipulator, and considering theapplicability of gravity change and demand for the future of anthropomorphic operation,inverse kinematics algorithm with real-time optimization of humanoid arm operatingposture was studied. At the same time, the dynamics model of complex structure of aspacecraft under the interference of mechanical arm motion was set up, providing themathematical basis for the follow-up control algorithm.Then, setting a series configuration of free-floating space robot as an example, thecontrol strategy considering the gravity effect was designed. In view of the existing basemomentum coupling and freedom change, First the adaptive compensation strategy wasput forward basing on the fuzzy identification online of gravity related terms, realizing theeffective control for the model change. Then taking the gravity related items asdisturbance of the system, adaptive fuzzy backstepping controller was designed from theangle of interference suppression. Based on the above solutions, taking the hybrid spacestation dexterous robotic manipulator as an example, the high precision joint spacetrajectory tracking control strategies with gravity effect related design for complexstructure space robot under the condition of strong nonlinearity and uncertainty werestudied.Finaly, based on the research above, the possible chaotic motion of space robotconsidering the effect of gravity was further analyzed. Based on the generalized Hamiltonmodel, the present stabilization controller which can adapt to gravity change was designedby redistributing energy and injecting nonlinear damping. And the L2disturbancesuppression characteristic of the system was researched. Besides, the possible chaoticmotion of spacecraft caused by the manipulator motion and the liquid sloshing analyzingwas analyzed. In view of the difficult in interference measure, such as liquid sloshing, H∞control strategy based on disturbance observer was proposed to solve the chaotic problemof system under internal and external disturbance.