closed loop on pressure

<P style="MARGIN: 0px"><A href="dev.roboteq.com/dev1/ax3500closeup.shtml" target=_blank>AX3500 - position closed-loop
<P style="MARGIN: 0px"><FONT face="arial, helvetica, sans-serif" color=#0000cc>Is it feasible to use a pressure transducer feedback signal (amplified) intead of a potentiometer in closed-loop position mode?</FONT>
<P style="MARGIN: 0px"><FONT face="arial, helvetica, sans-serif" color=#0033cc>We want braking force to be proportional to our demand signal - to control braking force by having the actuator push a brake lever and using hydraulic pressure as feedback to close the loop.</FONT>
<P style="MARGIN: 0px"><FONT face="arial, helvetica, sans-serif" color=#0033cc>The dynamics are likely different than using a pot - the actuator doesn't move much to increase force, so we reallly want to control the actuator force, not its position. Force in our actuator is proportional to current - I assume PWM gives reasonable control of average current.</FONT>
<P style="MARGIN: 0px"><FONT face="arial, helvetica, sans-serif" color=#0033cc>Has anyone tried this?</FONT>
<P style="MARGIN: 0px"><FONT face="arial, helvetica, sans-serif" color=#0033cc>Do the PID tuning constants have enough range to accommodate this scenario?</FONT>
<P style="MARGIN: 0px"><FONT face="arial, helvetica, sans-serif" color=#0033cc>Is the PID loop fast enough for this application? (the pressure changes very quickly with very little movement of the actuator)</FONT>
<P style="MARGIN: 0px">

As long as your transducer outputs a signal in the 0-5V range, you should be able to use it as you described. The PID loop executes every 16ms.

Is it possible to use the controller simply as a PWM driver with no feedback?

We think by making the PWM output proportional to the demand signal, we will get proportional braking.

<P style="MARGIN: 0px">You can configure the controller to operate in open loop.
<P style="MARGIN: 0px">
<P style="MARGIN: 0px">However, commands will be read and executed every 16ms.