Servo motors running synchronized

A video showing two servo motors being controlled independently & synchronized over RS485 based field bus. A small custom C++ software is generating the trajectory points independently for each axis and feeding the points to servo drive command buffers. Drives execute commands from buffer based on their internal clock yielding gapless and smooth motion even when PC is under load.

Both axis are fed 1250 position commands per second and tracking error value is read back at same rate and displayed on the PC screen. The software has a buffer monitor widget that shows how much data drive buffer currently has. Everything is fine as long as buffer doesn’t go empty which would cause a break in motion.

The app has merely 200 lines of code. I’m planning to extend it to run G-code after Argon drives are out.

9 thoughts on “Servo motors running synchronized

  1. Excellent!
    response speed of the motors is incredible is exelent for CNC machine tools

    what type of engine for this test ?

    • These motors have a story to tell. 6 or 7 years ago they were available from surpluscenter for bargain prices and I purchased several among some other Finnish guys. However I had no drive for them and didn’t feel like using some random stuff from ebay, so I started designing a drive. The rest is history :)

      • ok so the origin of design drivre VSD-E is somewhat thanks to this engine

        I have a DC motor without brake control
        I do not know if I could dynamicly also important to
        their characteristic :
        max voltage 200V
        nominal current 12.8A
        peak current 125A
        permanent magnet

        • Actually VSD-A was the first drive.

          The DC motor specs looks good, however that peak current is very high and Argon can’t output that much (~20A max). However, this affects only to available short term peak torque which may not be needed anyway. More important 12.8A continuous can be fulfilled 100%.

          • effectively the peak current is not necessary
            and I not think the old electronic control can get out as current

            you think to design a version of “X” for argon as the VSD-E
            which is available in VSD-XE?
            to deliver more current

          • Actually Argon is the “X” model. The name very originally was VSD-XR but was renamed to Argon as it is so much different from any VSD drive.

            Argon already has the most powerful high freq capable motor power stage module available from Fairchild semiconductor.

  2. Hi Tero!
    Hi Everybody!

    Honestly I didn’t see any synchronized motion. I mean any usable in the industry. Please, turn the both drives together with the same positon setpoint at 5000+ rpm. Put a stroboscope triggered by the index pulse of one of the encoders. Voiles – it would show if the motion is really synchronized. I’m pretty seduced to see / provide such an experiment – if I could have 2 drives of course.

    • They run synchronized but independently. At the beginning of video you’ll see motors shaking synchronized (both follow sin(t)) and after that, one motor follows sin(t) and the second cos(t) function.

      I’ll think of better demos later :)

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