Position control device and method of a robot system

A position control method of a robot system, comprising the steps of:

• receiving moving distance data from a main CPU and computing objective position data corresponding to a position to which an object is to be moved and a first deviation data between the objective position data and actual distance data every sampling time by a central processing unit;
• reading-in the actual position data of the motor, computing a second deviation value by subtracting a first motor position data of a previous, first sampling time from the actual position data and a third deviation value by subtracting a second motor position data of a previous, second sampling time from the first motor position data and computing a differential value by subtracting the third deviation value from the second deviation value;
• determining whether the second deviation value corresponds to one rotation of the motor;
• adding or subtracting the number of pulses corresponding one rotation of the motor to or from the second deviation value when the motor has been rotated once in the determining step to obtain the third deviation value and the differential value again and comparing the absolute value of the obtained differential value with the maximum upper limit of noise decision to determine whether noise components are contained in the actual position data, and, comparing the maximum upper limit of noise decision with the absolute value of the differential value of the position data of the motor when the motor has not been rotated once to determine whether noise components are contained in the actual position data of the motor;
• and,
• controlling directly the motor when, at the adding or subtracting step, noise components are not contained in the actual position data of the motor, and, adding or subtracting an objective position deviation value obtained to or from the actual position data when noise components are contained in the actual position data to thereby control the motor.