position tracking using encoder counts

[Ya-hoo]

I have two feedback signals, encoder and pressure gauge, for two types of control mode respectively, velocity and pressure. In velocity mode, primary feedback is set to encoder 1 and in pressure mode, primary feedback is set to ADC 1 programmatically. So in pressure mode, the analog signal should represent pump pressure instead of position. I will lose position tracking in this case, Am I right?

Is there any possibility to implement it?

Thanks.

[mhaag]

Analog feedback simply sends a voltage to the motion controller board that uses that input voltage to hold a given position of the motor. For example, if you have a pressure sensor and need to maintain a given pressure, which will correspond to a known voltage, then the PID loop of the servo motor system will maintain that pressure and position of the motor. The motor will move as needed to maintain the desired value of the analog feedback device.

If you would like to keep track of the position of the motor also via an encoder, then you could wire that encoder input into an open axis. For example, you could be running your motor off of Axis 1 and then set up a dummy motor and your actual encoder on Axis 2. This would allow you to
monitor the position but also take advantage of using the analog feedback.

Regards,
Michael

[Ya-hoo]

Hi mahaag,

Thanks for your very valuable point. I have a question here, is it a big difference for control performance if 2 axes are used? because the PID loop time will be 125us instead of 62.5us.

Thanks.