Flexible Space Manipulator Dynamics And Active Control Study

With the deepening of space exploration, the future space missions continue to be more and more, but it is hard to be completed entirely all by the astronauts as a results of the particularity and the risk of the space environment. The space flexible manipulator has the capability of adapting the vile space environment, so it is practically significant in both the economy and security aspects to assist or replace astronauts to complete some space operations utilizing the space manipulators, and it has become an important research direction in the space technology field. This paper is supported by the Key Project of Ministry of Education of China (307005) "space flexible robot dynamics/control coupling system research", and deeply focused on the dynamics and active control strategies for the space manipulator. The main work of this paper is as follows:Firstly, the concept of rigid/flexible/control coupling mode analysis for the space flexible manipulator is proposed. The complex boundary conditions of flexible arm under the dynamic constraint state is obtained using feedback constraint theory, and the gain parameters of the joint controller are introduced into the vibration dynamic equation near the discrete equilibrium position. The analytic method of solving mode differential equations in frequency domain and state space are established separately. Taking into account the problem that the elastic modes are influenced by the large-scale movement, the mode parameters under the rigid/flexible coupling movement are solved in respect of the tangential inertia item. Especially, a multi degree of freedom mode characteristics of space manipulator are solved by the finite element method.Secondly, the rigid/flexible/control coupling dynamics equations for the space manipulator involving the constrained damping non-conservative forces are established with Hamilton variational principle from the perspective of virtual work. Based on state space model, a stable numerical PIM that is suitable for both open and closed-loop conditions system is designed, and a large number of numerical experiments are implemented to verify the integration algorithma. The dynamic response under the feedback constraint is resolved by the PIM in oeder to compare with the traditional KED method, and some conclusions different from the classical vibration theory are obtained.Thirdly, the uncertain second-order cascade dynamics equations including non-consecutive friction and external interference were modelled. In view of the complex dynamics character that flexibility coexists with friction, uncertain parameter perturbations and disturbances, a wavelet neural networks-robust hybrid control strategy was proposed. The global controller was designed using backstepping technique to compensate the flexibility and suppress disturbance based on L2 property. Considering it is difficult for the conventional neural networks to identify the non-consecutive items, the wavelet neural networks approach was locally utilized to estimate the nonlinear terms including friction and uncertainties. This strategy can avoid the complicated derivation, acceleration measurement, friction identification and uncertain upper bound forecast.Fourthly, the two-link manipulator system was decomposed into input-output subsystem and internal subsystem by differential geometry input-output linearization method, and then the normalized equation of zero-dynamics is educed. The relationship between the choice of system observation output position and the zero-dynamic stability is discussed. A robust control approach using global terminal sliding mode was developed and the nonminimum phase control problem of two-link flexible space manipulator was solved. The target completing joint positioning and residual vibration suppression is achieved only rely on the joint driven motor.Finally, some experiments about dynamics and control strategy of flexible space manipulator are researched. A ground gravity flotation simulation integrated experimental platform for space flexible manipulator is designed, and some typical experiments, such as flexible joint position tracking and testing, experimental modal analysis for the flexible beam, and residual vibration suppression are performed.