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Analog input for Servo-feedback


Raghav
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Dear All,

I'm using piezo-actuator along with servo motors. I want to use the piezo's strain-gauge voltage output as my feedback. I have a ACC36-E card which is used with the UMAC rack. I had configured the card to automatic read mode by using the manual. Now I face the following issues:

 

1) The suggested M variable M5061=4023 counts. But the voltage output range is only 0-10V. So I'm not sure of the count value since it points to 20V.

 

The following are the A/D convert code is:

I5060=1

I5061=$78C00

I5062=$78C00

I5063=$78C00

I5064=$78C00

I5065=$78C00

I5066=$78C00

I5067=$78C00

I5068=$78C00

I5069=$78800

I5070=$78800

I5071=$78800

I5072=$78800

I5073=$78800

I5074=$78800

I5075=$78800

I5076=$78800

 

 

I5080=1

I5081=$0

I5082=$1

I5083=$2

I5084=$3

I5085=$4

I5086=$5

I5087=$6

I5088=$7

 

Also I'm not sure of using this value to form an analog input based servo control. I couldn't find the hardware ACC36E in the ECT (as mentioned in the manual). So kindly guide me in addressing the ADC 1 to act as the feedback for axis 3 of the UMAC.

 

Also, let me know if there will be any issue in the synchronized programmed move between the Piezo axis and the other servo axis.

 

Thanks in advance.

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  • 3 weeks later...

Hi All,

I had set the A/D channel 1 to point-out Motor-3 encoder. I'm able to see the counts in the position window for a given "o" command. But when I try to use the closed-loop jog command, I don't see any change in the counts. What could be wrong?

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There are a few steps to do before trying to close the loop on a motor:

- Make sure you have feedback: move motor by hand and monitor position changes in the position window

- Know how many counts per travel (revolution, or mm) you have

- Set up the motor output so it is responsive to open loop commands

- Set up the command output properly, corresponding the amplifier/motor specs

- Perform an open loop test: Make sure the motor goes in positive direction with positive open loop commands, and negative direction with negative open loop commands. Once you pass this step, you then can try closing the loop and tuning the motor.

 

Note, that if you need to change the encoder (analog input) direction you would have to swap the analog input leads on the ACC-36E (ADC+ goes to ADC- or vice versa).

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