Velocity Feedforward - Leadshine EL8-EC Series User Manual

6.8.1 Velocity feedforward

Velocity feedforward can be used in position control mode. When the function is enabled,
it can increase velocity responsiveness, reduce position deviation during constant velocity.
Name
Pr1.10
Range
Activation
Used for decreasing following error caused by low responsiveness of velocity loop. Might cause
overshoot or increase in noise if set value is too high.
Name
Pr1.11
Range
Activation
Set velocity feed forward low pass filter to eliminate high or abnormal frequencies in velocity feed
forward command. Often used when position command with low resolution or high electronic gear
ration to smoothen velocity feed forward.
Position deviation under constant velocity can be lowered with higher velocity feed forward gain.
Please to refer to the equation below.
Position deviation[Uint]=
Velocity feedforward application
Set Pr1.11 to around 50 (0.5ms), then tune Pr1.10 from 0 to bigger values until the velocity
feedforward achieves better performance. Under constant velocity, the position deviation
in a motion will decrease as the velocity feedforward gain increase.
Steps to tuning:
1. Increase Pr1.10 to increase responsiveness but velocity overshoot might occur
during acc-/deceleration.
2. By reducing Pr1.11, velocity feedforward would be more effective and vice versa.
Pr1.10 and Pr1.11 need to be tuned to a balance.
3. If mechanical noise exists under normal working conditions, please increase Pr1.11
or use position command filter (1 time delay/ FIR smoothing filter)
Velocity feed forward
gain
0~1000 Unit 0.10%
Immediate
Velocity feed forward
filter time constant
0~6400 Unit 0.01ms Default
Immediate
User manual of EL8-EC***F AC Servo
Mode PP
Default 300
Mode
PP
50
CS
HM
P
Index 2110h
CS
HM
P
Index 2111h
251