Research On Active Disturbance Rejection Control Of Pneumatic Gravity Compensation System

In the simulation of space zero-gravity environment,the gravity compensation system is widely used.The zero-gravity environment that can perform relevant dynamic experiments on the ground before on-orbit flight of space systems such as aircrafts and space stations is provided by gravity compensation system.Because the high power-to-mass ratio,excellent controllability and dynamic compensation can be realized of pneumatic systems.This subject proposes a gravity compensation system based on an air-float and non-friction cylinder.Through the high-precision control of the gas pressure in the cylinder chamber,real-time accurate gravity compensation of the load can be realized.The main research contents of this article are summarized as follows:Firstly,the overall structure of the pneumatic gravity compensation system is designed,the key components needed for the system are selected and analyzed,the system mechanical structure and system software structure are designed,and the prototype of the control system is developed;Secondly,the pressure control strategy of the pneumatic gravity compensation system based on the active disturbance rejection controller is analyzed.In order to achieve the improvement of the ADRC,the defect of the non-continuous derivative that the nonlinear function fal in the classical active disturbance rejection controller is improved to a smooth continuous function in the entire real number domain.Afterwards,a second-order simplified mathematical model for pressure servo control of pneumatic gravity compensation system based on proportional flow valve control is established.The simulation experiments about classical active disturbance rejection controller,improved active disturbance rejection controller and traditional PID controller for established mathematical model is performed.Finally,the pressure control experiment on the prototype of the pneumatic gravity compensation system is performed.The results show that the improvement of the active disturbance rejection controller for gravity compensation system based on air-float and non-friction cylinders is effective.The control accuracy,response speed and anti-interference ability of the improved active disturbance rejection controller are obviously better than those of the traditional PID controller.Compared with the traditional PID controller,the steady-state error is reduced by more than 62.81%,the response speed is improved by more than 58.67%,and the anti-interference ability is improved by more than 59.65%of the improved active disturbance rejection controller,the real-time and high-precision pressure control of the pneumatic gravity compensation system is realized.