Research on Theodolite Auto-Focus Motor Control Technology Based on a Disturbance Observer

The design of DC servo control system for focus motor is an important part to realize the electronic theodolites auto-focusing. Focus motor is seriously influenced by various disturbances, such as friction and torque fluctuation, in frequently reversing process. It is difficult to accurately locate. To solve these problems, a DC motor control method was put forward which combined the integral separation PID and disturbance observer. Based on the three closed-loop DC servo system, the integral separation PID controller was taken in position loop, in order to eliminate static error and improve the control precision. The methods of motor trajectory planning were analyzed, the 4-5-6-7 interpolation trajectory planning was used to decline or prevent the start-stop impact and oscillation. The effectiveness of the control strategy was verified by comparative simulation experiment. The robustness anti-disturbance and location precision performance is improved significantly.