A Fuzzy-Logic Based Tuning for a Velocity Controller of the DC Servo Drive

The paper presents a methodology of designing a velocity control system for a DC motor servo drive that is widely used in CNC power transmission systems. There are presented both: the algorithm for tuning the velocity controller for a specified value of overshoot and a fuzzy-logic based tuning of PID controller procedure. Usage of a method called PID-OVR, which ensures the assumed overshoot in a control loop, allows one to chose initial settings of the controller. This algorithm is used with assump¬tions that the load of motor is equal to zero and that the elec¬trical Tem and mechanical Tmm parameters (time constants) are known accurately. Since all this parameters are always encumbered with errors and the load torque of motor during its work is greater than zero the initially assumed controller settings may not ensure well enough quality of the velocity regulation. Overshoot and damping factor of a step response in a velocity control loop, both of these parameters are used in a fuzzy-logic based tuning of PID controller procedure. This procedure do not require any active identification experiments to be carried out, thanks to which the control performance is not affected.