Surveying instrument and a method for drive control thereof

摘要

A surveying instrument assumes either a high-speed drive control mode for driving a surveying optical system at high speed or a low-speed drive control mode for driving the surveying optical system at low speed. A motor is continuously driven through a PWM control method in the high-speed drive control mode. Then, the low-speed drive control mode is selected to drive the motor so as to allow the motor to alternate acceleration and a virtual stop. As the surveying optical system approaches a predetermined position, a condition for next motor acceleration is set based upon the detected rotational angle of the surveying optical system. Thus, it becomes possible to stop the surveying optical system at the predetermined position with a high degree of accuracy.