Due to the optical system is not in the rotating mechanism which can greatly reduce the weight of system

Periscopic Structure has been widely used in recent years in photoelectric terminal.But its periscope asymmetric structure always faces the phenomenon of cold welding

non-linear friction torque which caused by the low-temperature vacuum in space environment.In order to solve these problems and also to improve the control precision

a "dynamical lubricate" conception is proposed in this dissertation

which based on the dual-loop PID control

it includes position-loop and velocity-loop controller and a high-frequency pulse controller.The controller can lubricate the bearing and make the system in a dynamically status by using "soft" algorithm.The friction torque is compensated and the range of the controller linearity is ensured.At last a space temperature simulation experiment was held to test the effect.The temperature range was set from-30 degree to 50 degree.The positioning accuracy in the experiment is less than 10μrad

sinusoidal tracking accuracy is less than 28μrad.This result shows that by using the new control algorithm

an high-precision control needs is achieved during the great range of temperature and the tracking errors are distributed evenly.