Research On Dual-Motor Driven Microgravity Simulation System

With the development of deep space exploration technology,microgravity simulation technology that provides an environment for the ground test of spacecrafts has become more and more important.Among various microgravity simulation methods,the suspension method has been widely studied and applied in practical engineering due to its relatively simple structure and high control accuracy.Aiming at the microgravity simulation for spacecraft,this subject designs a dual-motor-driven microgravity simulation system based on the active suspension method,and proposes a dual-motor control strategy and a specific controller to achieve constant tension control vertically.Firstly,the dual-motor driven mechanical structure is designed in this thesis,and the performance analysis and mathematical modeling are carried out.Then,two main factors that have a great influence on the control performance in the microgravity simulation system are analyzed and the solutions are proposed.The problem of mechanical resonance in system can be avoid by selecting materials appropriately.It can be far away from the mechanical resonance point by reducing the moment of inertia of the transmission device.To solve the problem of friction interference widely existing in mechanical system with highly nonlinear characteristic,a dynamic friction model is established to describe and compensate.After that,the basic theory of sliding mode control is briefly introduced.Secondly,a dual-motor control strategy is designed to realize the control for constant tension vertically in microgravity simulation system.The large motor directly utilizes the torque mode for constant torque control,and the small motor performs position control through tension closed loop to compensate for the remaining interference after being buffered by the buffer spring.For compensating the friction torque in the mechanical system fully and accurately,this thesis proposes a dual-state observer based on the improved Lu Gre dynamic friction model and designs adaptive laws for multiple parameters in the model to renew the friction dynamically.As to the controller of small motor,this dissertation raises the algorithm of non-singular fast terminal sliding mode adaptive control(ANFTSM)with a dual-state observer for tension compensation,and the stability of the algorithm is proved according to the theory of Lyapunov stability.The high-precision control is realized through simulation,and the effectiveness and superiority of the algorithm are verified.Finally,an experimental platform with DSP and mechanical structure as the main components is built,and the selection of specific mechanical equipment is given.And then,the dual-motor driven microgravity simulation system is tested under two external interference signals of slope position disturbance and sinusoidal position disturbance,and the effectiveness of the microgravity simulation system designed in this thesis is verified.And the superiority of the ANFTSM control algorithm with friction compensation in terms of control accuracy is proved by comparing with the classic PID and traditional LSM control algorithm.