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brycegerman edited this page Apr 16, 2019 · 4 revisions

Smart Current Limit

Keeps the current draw from the Neos below the given limit. The smart current limit also allows for three different variables to be passed:

  • Stall Limit
    • Current limit when the velocity is below the RPM limit
  • Free Speed Limit
    • Current limit when the velocity is above the RPM limit
  • RPM Limit
    • Velocity at which the current limit changes from the stall limit to the free speed limit

NOTE: If the current reaches or exceeds 80 amps it can damage the Neos.

Code Example:
neoMotorObject.setSmartCurrentLimit(stallLimit, currentLimit, rpmLimit);

Finding the Ideal Current Limits

Our initial use of the current limit still caused the Spark Max motor controllers to disable the Neos as they were drawing too much current.
The initial current limit was 80 amps, but it did not account for the stall or RPM limits.

Current Tests:

  • Test 1:
    • Stall: 35
    • Free: 35
    • RPM: 10
    • Results:
      • The robot drove forward and reverse smoothly, without tipping the robot. It accelerated rather quickly. However this current limit didn't allow for the robot to turn in place. Turning while driving drove smoothly.
  • Test 2:
    • Stall: 40
    • Free: 40
    • RPM: 10
    • Results:
      • The robot drove forward and reverse rather choppy, as it accelerated rather quickly. With these values the robot was tipping during sudden accelerations in the opposite direction. However, turning in place was possible, but was rather choppy as well, causing the robot to bounce from side to side as it turned.
  • Test 3:
    • Stall: 38
    • Free: 38
    • RPM: 10
    • Results:
      • The robot drove and accelerated forward and reverse smoothly, but still could cause tipping if the speed moves from a forward speed to a negative speed. Turning in place and turning while driving were both smooth. Turning in place can cause tipping if the robot is spinning at full speed.
  • Conclusion:
    • We decided to use a Stall limit of 40 amps, and a free limit of 40 amps. This allows the robot to be able to ramp up at the same rate, as well as limit the amount of amps being drawn when the velocity is near zero.

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