IP controllers are commonly designed for small machines with quick response (high mechanical rigidity). For step command of position, softening torque rise characteristic upon startup can reduce vibration. PI controllers are commonly designed for large machines with slow response (low mechanical rigidity). As a large torque can be attained within a relatively short time after receipt of a speed command, use in machines with high rigidity (such as small machines driven by using screw rods) can improve the torque rise characteristic upon startup. PDFF controllers have characteristics of both IP and PI controllers.
They can be used for biased IP or PI control depending on the value of the PDFF coefficient, with both response and reduction of vibration upon frequent start/stop considered. Associated parameter 66 Technical Manual for EA190 Series Servo Driver V100 Function code Parameter name Function P4-12 PDFF control coefficient When the set value approaches to 0, the control is biased towards IP control; when it is 0, the control is totally IP control. When the set value approaches to 100, the control is biased towards PI control; when the set value is 100, the control is totally PI control.
When overshooting occurs to speed feedback, P4-12 shall be gradually reduced from 100 until the desired effect is achieved.