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BrianMoyer

DMC60C CAN Control 0 Message

Question

Hello,

I am using a couple of DMC60C with an NI-XNET USB 8502. I have had some good luck but am running into a very specific question.

The control message:

0x02060000

Uses a signed 24-bit integer for both closed loop velocity and closed loop position control setpoints. However, the makeup of that value is only loosely described in the documentation.

My questions are:

1) is the byte order as shown in the manual correct? It appears strange to go trgtH in byte 3, targtL in bye 4, and trgtM in byte 5. I could understand H, M, L or L, M, H but it seems oddly shuffled as presented.

2) is a negative 24 bit value stored as 2's complement?

 

Thank you for any advice. My motor does not appear to like the values I have been sending for velocity control mode.

 

Sincerely,

Brian

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I have determined that the issues I was seeing were a result of poor PID control parameters and that the CAN Control message as documented is just fine.

To anyone else attempting to directly control a DMC60C using CAN, know that having bad PID control parameters can lead to LEDs that flash valid (green or red depending on direction) briefly and then turn to solid yellow for a bit, repeat. This can cause occasionally violent stop-starts or just strange jerky motion. Another possible symptom is having the motor spin (using CL velocity control) but at an apparently constant rate (very fast) that is unresponsive to target setpoint changes.

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