The Design And Research Of The Pneumatic Spring Vertical Suspension System

In order to simulate the condition of zero gravity in space and accord with theconditions of ‘freedom freedom’ for spacecraft simulator on the earth, the paper putsforward a design scheme of pneumatic spring vertical suspension system, featured withgreat load, low rigidity, low frequency, low coefficient of friction and long stroke length.The system mainly consists of zero friction cylinder and piston system, high-precisionpressure control system and accumulator. The first component is used to hang thesimulator so as to bear its weight. The second one is applied to stabilize pressure in theinternal system so as to ensure rigidity and frequency. The last can lower the pressurefluctuation to enhance the system performance.The key element affecting system performance is based on accuracy of modeling.These models include discharge, radial bearing capacity and pressure fluctuation. Thecombination of discharge model and radial bearing capacity model is used to optimizethe system structure parameters and minimize the discharge while guaranteeing therigidity of radial bearing capacity. Pressure fluctuation model belongs to a nonlinearmathematic model with a time relay link. For boosting the control quality, building ahigh precision model is definitely needed.Aiming at the pressure fluctuation model, a corresponding controller is proposed.On the basis of traditional PID controller, PID controllers including trajectory planningand fuzzy control are raised to lower the overshoot and enhance the system quality.What’s more, the paper came up with one control strategy combining of various controllaws including bang-bang controller, PID controllers based on trajectory planning andfuzzy controller.The structure parameters of system and the effects caused by environmentalparameters were finally concluded through combining the pressure control models withthe dynamic models of the simulator. Also the analysis of the system frequency andrigidity and the displacement caused by external incentives in the simulator werecompleted. In conclusion, the displacement response can meet the demands whateverthe simulator is excited by high frequency sine sweeping, low frequency sine sweeping,square wave or triangle wave.