PID controller loop

[Morganito]

Hi,
I have a problem to control the torque's setpoint.
I'm using the example in Labview 6.1 PID controller loop.
The process variable measures the torque and it's the same value indicated in the torquetronic, but the system isn't regulate as I want.
I always have the upper limit(10V) to the servovalve,so I have 7Nm even if I put 2Nm in the setpoint box.
I'm sure that the parameters in MAX are good (to the range).
How can I regulate the torque??
My PID values are: P=0,2 ; I=5 ; D=0 Are they right??

Salutations

[Dr._Imad]

Hi,
I am assuming that if the voltage to the servo valve is increased, the torque increases, and if it is decreased, the torque deceases.

First, test the setup in open loop, that is, set the voltage directly to the servo (0--10V)(without using the loop), does the torque value changes accordingly, if not you have a mechnaical/electrical problem.
If it reponds, then
Start with D=0, and small values of P and I, and monitor the voltage output of the PID,
then incease P and I in small increments
In general, as P and/or I are increased, the voltage output and torque also increase. Large values will make the system torque/voltage osciilate.