Motion Control and Motor Drives
feedforward PID control of actuator not responding
Hello,
We have a linear actuator operating under load control. This meaning that the force produced by the actuator is proportional to a reference voltage sent to the actuators control drive from our computer running labview. The linear actuator has a very nonlinear response to the current sent from the motor drive, and to correct for this, we have had some luck with the PID controller. But we have not got it perfect yet.
So although we have scaled the inputs to the PID controller, a problem is that there is a phase delay. An image of this is attached. Green is the PID output, red is the set point, and white the reading from the load cell. The amplitudes and DC levels are not perfectly adjusted as it is as close as it can get, I think, until the phase is corrected. So this particular phase delay seems to be because there is a time difference between the time the sinusoidal set point is created and the time the load cell (feedback PV) is sampled.
So to correct for this, I thought a feed forward algorithm might work as I though this is what they are created for. But I haven't had any luck making the feedforward do anything. I have set the gain to 1 to 1.5, and lead and lag terms individually to many different values from 0.001 to 5. I have not seen the phase change yet. I would have expected some shift between the PV and SP. Any ideas on what is going on? Ill attach the labview program. Im just be implementing it wrong.
Ill attach the main program.
