Technical Manual for EA350 Analog Pulse Type Servo Driver V101 6.11.1 PDFF control When the speed command drives the motor to rotate, as the servo motor has a mechanical load dragging on the shaft end, the performance characteristic of the motor shaft is still determined by the response characteristic of the mechanical system. Considering needs of various mechanical systems, EA350 servo is also designed with a PDFF controller in its speed loop, which can be used in the non-torque mode. The PDFF controller is a controller between PI and IP controllers, having features of both the PI and IP controllers. IP controller structure:
PI controller structure Comparison of the IP and PI control effect in case of the same proportional gain and integral time parameter 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 77 Function Parameter name Function code 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.