Research On Technologies Of Horizontal Position Tracking For Suspended Zero-gravity Simulation System

The high reliability of aerospace-craft is largely depended on the low or zerogravity test on the ground. Compared to drop tower, parabolic flight, underwater,air-bearing and other ways, the sling suspension method to compensate the gravityis relatively more easy,effective and ecnomic.In the zero-gravity simulationsystem by sling suspension,to actively track the suspended target is the keytechnology to keep the sling vetical and to eliminate the system disturbance,also isthe key part to increase the simulation accuracy. Our project is established forresearching the control approach to track the horizontal position of suspendedtarget,includes the research of tracking control with zero disturbance and theresearch of target position measure with high precision and high frequency.To research the tracking control method,the system design is firstly presented,then the3-D dynamic model with5DOFs of tracking and suspension module isestablished by Lagrange method, and the3-D model is linearized and simplified toa2-D modle with3DOFs by its symmetric and decoupled characteristics;Theavailability of danymic model is validated by numerical simulation,thecharacteristics of dynamic and control are also analysed.In order to eliminate the disturbance effect, a new control strategy based onthe time integral value of disturbance force equals zero is proposed, and thehorizontal tracking control law is derived base on such strategy; The trackingcontrol system is constructed by regulating the swing angle after the design ofmechanical drive, transmission and electric for control sysem; A method of speedrate feedback control is used to avoid resonance within the bandwidth of controlsystem; then a classic controller is designed; The software simulation resultsindicates tracking controller works very well in coincidence with initial intention,it’s verified to be feasible, effective and robust.To research the target position measure method, a system scheme bases on thetechniques of PSD and auto-collimation is presented, then the optic mathematicalmodel is established; The model simulation is implemented to research the idealspace scatter of beam spot via swing angel, the locus of beam spot on PSD, and thenonlinear characteristic of measure method, and the validity of the mathematicalmodel is verified; To verify the feasibility of the mesure method,the measureerrors are analysed, the assembly errors of PSD and reflector mirror are modeledto discuss the reduction steps for the engineering practice.