System Design And Control Strategy Research Of The Subreflector Adjusting Control System For65Meters Radio Telescope

The subreflector’s pose of the65m radiotelescope is adjusted using Stewart parallel adjusting mechanism, which to realize the pointing error correction and feed conversion. The control system of the adjusting mechanism is designed and the theoretical analysis and experimental study is deeply carried out for the control strategy, on how to improve the parallel adjusting mechanism’s stability, accuracy and rapidity. The main contents are as follows:The mapping relationship between generalized coordinates and moving platform, velocity and acceleration of driving links is analyzed, the partial velocity and partial angle velocity of each component are also computed. The inertia force of each component is obtained by analyzing the velocity and acceleration of each component caused by base moving, and which is taken as the system external force. The mechanism’s dynamic model, when the base is moving and is fixed, is established by using the Kane method with highly real-time characteristic, respectively. The system dynamic performances of two situations mentioned above are analyzed contrastively through numerical analysis and Adams software simulation.On the basis of the PID feedback control, the feedforward compensator is designed to compensate the velocity, acceleration and viscous friction, and its principle and stability is also analyzed. The dynamic model of the driving links is constructed, and the control system’s performance is tested and verified by S curve tracking response. The multi-axis control system and mechainsm model are bulit by the software Simulink and SimMechanism, respectively, and the tracking precision of the former is also simulated and tested by adjusting the given circle trajectory dynamic tracking.The method for monitoring the pose accuracy of the adjusting mechanism is proposed and gives out the error out-of-tolerance discriminant formula. The zero point reconstruction is realized by analyzing the homing principle and using the mutual correction method of the magnetoscale and homing sensor, and its precision is also tested by experiment. According to the characteristic that the number of mechanism degree of freedom (DOF) is larger than the task, the fault-tolerant strategy of adjusting mechanism is put forward based on redundant DOF, and the workspace of the mechanism with fault tolerant strategy is also analyzed. A digitization method to identify the irregular workspace boundary is designed to enlarge the working range of the mechanism.The modular thought is used to design the electrical control system which include servo driver unit, linear motion unit, low pressure control unit and motion control unit by analyzing the functional requirements of the adusting mechanism. The software system of is designed by using the COM component, ActiveX control and dynamic link library technology, and the CUDA parallel computing technology is used to deal with the trajectory planing interpolation, which promote the real-time characteristic of the symstem. The Client/Server network control structure is established and the romote control of adjusting system is also realized by the TCP/IP protocol.The method to be suitable for measuring and evaluating the repetitive positioning accuracy in conjunction with coupling repetitive positioning accuracy of parallel mechanism is proposed, which refering to the detection and evaluation method for the repetitive positioning accuracy of the numerical control machine in the national standard GB/T1741.2-2000, and the adjusting mechanism’s repetitive position precision is measured and analyzed by using the laser tracker. The dynamic tracking precision are tested and analyzed of the driving links and adjusting mechanism, and the feasibility of the adjusting mechanism’s fault-tolerant strategy based on the redundant DOF proposed in this article is verified by experiment...