Help to understand the performance

Support DYNAMIXEL
1

Hi all, I have a dynamixel MX64AT based on Prtocol 2.0 and powered by 12V.

I have some questions about performances:

  1. from the graph https://emanual.robotis.com/assets/images/dxl/mx/mx-64_ntgraph.jpg
    it seems that a speed of 0 is made by a current of 4.1A and I have some confusion because of the unit, in the graph’s image is 4.1mA and in the specifications DYNAMIXEL MX-64AT - ROBOTIS is 4.1A. Looking then in wizard 2.0, if I set 1941 the conversion becomes 4100mA. Is the graph’s scale wrong?

  2. What is the relation between the raw unit and the milli_ampere unit of the current looking at this https://emanual.robotis.com/docs/en/popup/arduino_api/setGoalCurrent/?

  3. I m interested to understand better the topic of the torque-stall torque controlling also the performance graph. In my case I would like to swing an rectangular objects as pendulum
    Cattura
    and I would like to understand if the dynamixel is able to drive a pendulum of a certain weight (for example 1kg it’s not important) and 1 m of length for example. I noticed this interesting page Torque Ratings - ROBOTIS where there are some formula but not so practical. Indeed, how can I get also an hypotesys of efficiency in terms of working time duration?
    A little example in poor words, if I set 2800 mA (from the first graph) I shall have 3Nm of torque and 70% of efficiency. How is the maximum load that the dynamixel can swings and for how long time?

  4. How a variable resistance could interfere with that above?

Surely your comments and tips could help me to make it clearer, thank you.

2
  1. The linked graph does not extend all the way to the maximum 4.1A input current. The highest point shown on the chart is for approximately 2.6A
  2. The relationship is about 3.36mA per unit.
  3. You can calculate the expected torque load by multiplying the weight by the length of the moment arm. In your example case, a weight of 1Kg on a 1m would require 1Kg/m of force (9.80665N/m). Regarding your output estimate from the graph, the given chart does not provide values at 2.8A. If we look at 2.45A, (the highest clearly labeled current) we see that we should expect about 2.8N/m of torque at 26RPM with an efficiency of only 25%.
  4. A variable amount of resistive force would affect the calculation for torque requirements by changing the weight at the end of the moment arm.
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