Research On Active Vibration Isolation System Based On Voice Coil Motor Under Microgravity Condition

When the spacecraft is in orbit, precise instruments and equipments are in micro-gravity environment, small low-frequency vibration influence on them is particularlysignificantly. In order to protect the instruments and equipments in the spacecraft andto improve their precision, it’s necessary to design vibration isolation platform tosuppress of small low-frequency of vibration. The structure of voice coil motor issimple, and is small in size, light in weight, and has high acceleration and speed,uniform thrust, fast response and high precision advantages, so it is very suitable for theisolation design. In this paper, active vibration isolation system is designed based onStewart platform, which has strong bearing capacity and high stiffness, using voice coilmotor(VCM) as actuators.Firstly the causes of micro-gravity it’s influence on kinetic analysis is analyzed,then the working principle of the VCM is introduced and its theory model is established,and the basis of the voice coil motor selection is given. Stewart platform of cubic ischosen because of little coupling and that SISO control can simplify the control system.The principle and structure of the active rod is designed based on the vibration isolationeffect of single-pole parameters and the point of the control force.Using displacement transfer rate as the goal of optimization target, a controlsystem is designed in this part, the displacement transfer rate of which is equal to zeroin theory. Then the stability of the active control system is analyzed and the system isunconditionally stable. Simulink simulation results show that the active control systemhas good vibration isolation effects.By using PID control principle, a feedforward-feedback compound control systemis designed in this article, which is on the basis of the impact of vibration isolationeffect of different feedback parameters. Under the premise of the control system to meetthe control targets, the PID controller is replaced by a simple P controller to simplify thecontrol system design. The feedforward control signal is the excitation signals and theabsolute displacement of the controlled object is used as feedback control signal. Thesimulation results show that the designed controller achieves vibration isolation effect touse a low control voltage and a small control force.The parameters of the cubic Stewart platform infrastructure are chosen and theStewart active vibration isolation platform is analyzed using co-simulation of ADAMS-Matlab/Simulink. Firstly mechanistic model in ADAMS is established, then SISOcontrol system of six active poles is created and calls the ADAMS Controls module toestablish a channel of data exchange. Using the excitation of typical signals, the designed Stewart active vibration isolation platform for precision instruments has apretty good vibration isolation effect of the vibration intensity in vertical direction,which is the main direction of vibration source. The vibration isolation platform also hasgood isolation effects on the vibration from the horizontal direction. At last, the demandof the control voltage and driving force is analyzed in the paper and the results showthat the system can satisfy the low power consumption requirements.