Nonlinear PID Control Of The Stewart Platform For The Square Kilometers Array

Based on a completely new design project of next generation large radio telescope (LT) integrating mechtronics and optics technologies, for the high requirement of trajectory tracking of the feed-supporting system with large span cables, considering the high rigidity, the high precision and the high ability of load, one kind of Parallel Robot named Stewart platform was adopted by the fine tuning of LT. The Stewart platform is considered as a plant in this paper, inverse problems, the framework on Kinematics of fine tuning Stewart platform and the control strategy is analyzed. And based on the edbedded control technology, the control system of the platform is designed.Stewart platform is one kind of six degrees-of-freedom(DOF) Parallel Robot. The mechanism analysis of the High-precision Tracking Control of the Stewart Platform is deduced. The distributed control strategy is adopt in the joint space, and the double servo control sub-systems involving position control and velocity control is designed. For the system need of the Stewart platform, a kind of nonlinear PID linkspace controller is designed considering the project fact. The nonlinear function is given by the nonlinear PID algorithm, and the algorithm can guarantee the system have the property of the fast response, a little over shot and strong self adaptive.The model of the platform is constrated, and simulation of the typical signal output response is done. The effectiveness and feasibility of the linkspace control strategy and the non-linear PID controller are verified by the analyses and the results of the emulaton.Based on the motion control technology of the parallel robot, the position closed loop control system realized by the computer system is adopted. And the embedded control system of ARM+DSP architecture is adopted, which can guarantee the system have the property of high control precision, the high reliability and the strong realtime performance. And the embedded control system can solve the problem of the limit work place of the Stewart platform. The software and hardware of the embedded control system is also designed.