Research On Suspended Gravity Balance Control Based On DOB Fuzzy Self-tuning Smith Prediction

With the development of aerospace technology,human's exploration of space has become more and more in-depth.The Chang'e Project currently under way in China is nearing its end,and there will be more and more planetary exploration missions in the future,due to the extremely complex environment in outer space,the microgravity environment on the surface of different planets is different,so it is particularly important to simulate the microgravity environment on the ground.At present,there are many researches on the gravity compensation devices for the horizontal and low-speed motion of planetary vehicles in our country,but few on the simulation of the vertical and high-speed motion of the spacecraft cabin section separation.Therefore,the control method of the active suspension gravity compensation device simulating the lunar microgravity environment is studied in this paper,the factors influencing the control performance of the constant tension system are analyzed and the control algorithm is designed to restrain the influence and improve the control accuracy and response speed of the system.Finally,the simulation and experimental verification are carried out.Aiming at the active suspension gravity compensator,the mathematical model of constant tension system is established.The effects of nonlinear factors such as friction,time delay,parameter variation and resonance of buffer spring on the control performance of constant tension system are analyzed.PID control is introduced as a reference to establish the static and dynamic balance process of the system,then the influence of nonlinear factors on the anti-interference ability and follow-up response speed of the system is simulated and analyzed when the constant tension system is disturbed by strong external position disturbance.In this paper,Smith predictor is used to predict and compensate the time delay of the system.Considering the inaccuracy of the model caused by the time-varying parameters of the system,fuzzy PID controller is adopted to replace the PID controller to form fuzzy self-tuning Smith control system,which improves the dynamic performance of the system.In addition,disturbance observer is introduced to further improve the anti-disturbance ability of the system.The simulation results show that the fuzzy self-tuning Smith control based on disturbance observer can make the system fast enough while ensuring the control accuracy of the system.The optimal stiffness value of the cushion spring is determined by simulation for the influence of the stiffness change of the cushion spring on the system in the constant tension system.In order to verify the effectiveness of the new control method and the selection of cushion spring stiffness value,an experimental analysis is carried out by using the gravity compensation device.Through parallel control experiment,it is shown that fuzzy self-tuning Smith control based on disturbance observer can improve the antidisturbance ability and response speed of constant tension system compared with PID control,and the optimal value of buffer spring stiffness is determined by experiment.