Parker TPDM - Feedforward of Speed Loop

Parker Hannifin Manufacturing Srl user’s manual TPDM
114
9.6.11 FeedForward of speed loop
The feedforward into the speed loop is realized to offset the torque, like this during the
acceleration the speed error is reduced to zero.
Usage case:
• when the system needs high accelerations without error;
• when is difficult to calibrate the system;
in these case the feedforward of speed loop (Pr283) permits to increase the performances.
The current is monitoring by two parameters Pr284, FFWD monitor, and Pr287, speed loop
monitor. The optimal condition is to set-up the Pr283 until the speed torque, Pr287, is equal to
0 during the acceleration and deceleration phase.
An offset of torque (Pr285) is possible set to compensate the weight force, for example when
the payload is vertical.
To calculate the value of the feedforward gain is possible use the following method, in
according to the motor used:
Rotary motor (SMB, MB):
163842048
1
1
10128
1
60
2
256
1
283
Pr
6
••••
•
•
••=
−
peak
IKt
J
π
Where:
J [kg m
2
] = total inertia of the system;
Kt [N m/A] = motor torque constant;
I
peak
[A] = peak current of the drive.
Linear motor (PowerROD, Trilogy):
163842048
1
1
10128
1
60
1
256
1
283Pr
6
••
•
•••
•
••
=
−
peak
I
Kf
MPP
Where:
I
peak
[A] = peak current of the drive;
PP [m] = pole pitch;
M [kg] = total mass in movement;
Kf [N/A]= motor force constant.