Research On Position And Vibration Suppression Control Of Space Manipulator With Flexible Joint

Nowadays, most of the countries pay special attention to the utilization and development of the space resources. Space manipulators for finishing some space operation tasks show great significance, and have become an important research direction in space technology research field. The following features that a space manipulator must have:large output torque, high control precision, long life design, high reliability et al,all demands. Carefully designing of its control system. This article mainly focuses on the research of flexible joint, which is the key part of space manipulator. The research includes the dynamic model of the flexible joint, high precision position control and vibration suppression problems.Firstly, the simplified model of flexible joint is built based on Lagrange equation. The dynamics simulation analysis of the model is done applying Matlab/SimMechanics simulation software. This simulation analysis results demonstrate the performance of the dynamic model, so as to provide an important theoretical basis to the following research of control strategy. For flexible joint modeled as linear torsional spring model and spring damper adopted the normal PD control, we give a series of simulations and experiments under different input signals controller parameters and non-linear dampling items to compare and analysis their impacts on the system. Simulation results show that in order to control flexible joint precisely, further research on control strategy is needed.Secondly, we undertake a study on the high precision position control of space manipulator flexible joint. Taking consideration of the influence of the non-linear factors, by analyzing and combining the advantages and disadvantages of PD based half-closed-loop position control and PD based full-closed-loop position control, we design a position feedback PD controller to improve the position trajectory tracking precision of the joint output. In order to achieve a higher precision of the position trajectory tracking control.,aiming at the defects of PD controller, we adopt the Active Disturbance Rejection Control (ADRC) and, design a double position closed loop feedback ADRC control strategy. By simulation experiments, this control strategy can not only achieve high precision trajectory tracking control, but also overcome the negative effects of the non-linear factors such as friction and so on.Thirdly, we take research on the vibration abatement of the flexible joints on space manipulators. By the analysis of the vibration state of flexible joint, we adopt a torque negative feedback control to abate the vibration of joint. Considering that the joint torque is often affected by the disturbance signal, we further improve the torque feedback control by applying PD controller..The simulations reveal that the designed torque feedback PD controller can implement vibration suppression as well as better avoid the influence of disturbance signal. The designed torque feedback PD controller can’t suppress vibration effectively while remaining high trajectory tracking precision, a vibration torque feedback controller is designed to solve the problem. The simulation result shows that the designed controller can better suppress the vibration of the joints while keeping good trajectory tracking precision.Lastly, for the purpose of satisfying the design objective of the manipulator flexible joint, which should ensure high precision of the position control and at the same time achieve effective suppression of the vibration of the flexible joint, we combine the control strategies above to design four different position/force hybrid control strategies. Simulation results show the effectiveness of the four control strategies, and that the double position closed loop feedback ADRC control+vibration torque feedback mixture control strategy performs the best among the four strategies.