为了增强大口径望远镜跟踪架伺服控制系统的抗扰动性能, 提高其低速跟踪精度, 提出了基于扰动力矩观测器的力矩补偿方法。该方法采用改进的加减速法控制转台的加减速时间, 使得望远镜转台微震; 通过测量电机的速度和电流响应曲线, 辨识获得望远镜转台的转动惯量。然后, 设计了望远镜转台的加速度估计器, 根据编码器位置反馈数据, 采用双积分和PD控制的方法, 估计出当前系统的加速度。最后, 基于转动惯量辨识和加速度估计, 设计了扰动力矩观测器, 根据电机的电流和转台的加速度, 计算出外部的扰动力矩, 并将扰动前馈补偿到电流控制器的输入端, 以修正电流输入参考值。在2 m望远镜控制系统中对扰动观测器的性能进行了实验验证, 结果表明, 加入扰动力矩观测器补偿后, 在跟踪斜率为0.36 (″)/s的位置斜坡时, 跟踪误差值(RMS)由0.012 7″减小到0.007 3″; 相比未加入扰动力矩观测器的补偿方法, 望远镜的低速跟踪抖动明显减小, 提高了伺服系统的低速跟踪精度, 实现了对目标的平滑、稳定跟踪。

To improve the anti-disturbance performance and following tracking accuracy for the servo system in a large telescope, a torque compensation method based on a disturbance observer was proposed. With the method, the revised acceleration/deceleration control method was adopt to guide the telescope turntable oscillating in a little angle. Through measuring the velocity and current of a motor, the rotation inertia of the telescope turntable was indentified. Then, an acceleration estimator was designed to estimate the low-acceleration based on encoder feedback data by using the double integration and PD control method. Finally, based on the inertia identification and acceleration estimation, a disturbance observer was designed to estimate the external torque according to the motor current and turntable acceleration. Furthermore, the estimated disturbance torque was used to compensate the current input to correct reference currents . Experiment results demonstrate that after the observer is added, the following error RMS is reduced from 0.012 7″ to 0.0073″ at the sloop position of servo system to be 0.36 (″)/s. Compared with that without the disturbance torque observer, the following tracking jitter is reduced and the tracking accuracy is improved.