赤道式望远镜的变结构PI控制

Motion Control of Large Equatorial Telescope Based on Variable Structure PI Controller

为提高赤道式望远镜伺服系统的性能,分析了经典PI控制器的特点,并结合变结构的思想,设计了一种变结构PI控制器(VSPI)。构造了以速度误差为自变量的比例增益函数和以位置误差为自变量的积分增益函数,通过这两个函数,VSPI能够根据误差的变化实时改变其结构和参数。针对某赤道式望远镜的传递函数模型,仿真比较了经典PI和VSPI的控制结果,验证了VSPI的作用,同时在望远镜上进行了实验。实验结果表明:应用VSPI控制器后,赤道式望远镜的1°位置阶跃过渡时间由0.68 s缩短至0.59 s,稳态误差由0.62″RMS减小到0.13″RMS,等效正弦跟踪误差由3″RMS减小到1.87″RMS。采用变结构PI控制器的伺服系统性能明显提高,满足赤道式望远镜跟踪精度高、响应速度快的要求。

In order to improve the performance of the equatorial telescope servo system,the characteristics of the classical PI controller are analyzed,and a variable structure PI controller(VSPI)is designed based on the idea of variable structure.The proportional gain function with velocity error as independent variable and the integral gain function with position error as independent variable are constructed.Through these two functions,VSPI can change its structure and parameters in real time according to the variation of error.According to the transfer function model of an equatorial telescope,the effect of VSPI is verified by comparing the simulation result of classical PI and VSPI,and experimentsare carried out in the same telescope.The experimental data show that,by using VSPI controller,1 degrees position step transition time of equatorial telescope is shortened from 0.68s to 0.59s,the steady-state error is reduced from 0.62"RMS to 0.13"RMS,the equivalent sine tracking erroris reduced from 3"to 1.87".The performance of the servo system with variable structure PI controller is obviously improved,which meets the requirement of high tracking accuracy and fast response of equatorial telescope.