[BUG] absoluteZeroSearch not moving the motor to seek for the encoder zero

[F00LM1N4]

This is a simplified template, feel free to change it if it does not fit your case.

Describe the bug
I have configured the encoder as an ABI with Zero index feature.
During the initFOC() function the motor should try to find the zero index position in open-loop mode,
but it doesn't move so it will never find it. See the logs:

MOT:Monitor enabled!
MOT:Init
MOT:Enable driver.
MOT:Align sensor.
MOT:Index search...
ERR-MOT:Not found!
ERR-MOT:Init FOC fail

If I am quick enough and move the motor shaft manually when i see MOT:Index search... then the motor registers the zero position and goes on. See logs:

MOT:Monitor enabled! 
MOT:Init 
MOT:Enable driver. 
MOT:Align sensor. 
MOT:Index search... 
MOT:Success! 
MOT:sensor dir: CCW

That got me curious and reading the absoluteZeroSearch function it seems that the while loop that should
search for the zero position on the encoder only calls angleOpenloop(1.5f*_2PI); which to me seems to
only setup some variables to prepare for a movement doesn't actually perform one.

I tried blindly mimicking what's done inside the move() function in the case when the MotionControlType corresponds to angle_openloop then calling loopFOC all insid the while loop of absoluteZeroSearch,
but all I got was a vibrating motor not a movement.

I'm just starting to investigate this project so I'm sorry if this is not a bug but just me being a noob.

Describe the hardware setup
For us it is very important to know what is the hardware setup you're using in order to be able to help more directly

• Which motor: No name 1000KV motor
• Which driver: B-G431B-ESC1
• Which microcontroller: STM32G431CB
• Which position sensor: generic ABI encoder
• Current sensing used? NO

IDE you are using

• Platformio

[askuric]

Hey @F00LM1N4,

You are absolutely right. This is a bug!
Up to 2.3.5 the angleOpenloop function was calling setPhaseVoltage directly and was applying voltages to the motor.
Since v2.4 this is no longer the case and it is the loopFOC that is doing it.

I've forgotten to update this part of the code. I'm sorry about that!
If you roll back to v2.3.5 you should not have issues any more.

The smallest modification of the v2.4. code that would work is adding the setPhaseVoltage to the loop (in the file FOCMotor.cpp line 953):

  while(sensor->needsSearch() && shaft_angle < _2PI){
    angleOpenloop(1.5f*_2PI);
    // call important for some sensors not to loose count
    // not needed for the search
    sensor->update();
    // set the voltage to the motor
    setPhaseVoltage(voltage_limit, 0, shaft_angle);
  }

Sorry about that!
Let me know if this works for you and feel free to do a PR if you're interested.

There are a couple of these small bugs that we've found so far so we might do a quick follow-up release soon.

[F00LM1N4]

No problem! I'm glad to contribute :)
I'm trying your solution now, I'll let you know if I'm able to solve the bug (Hoping to have enough time between life and work xD).

If I fix it I'm available to do a PR, do you prefer me working on the dev branch or open a new one?

[F00LM1N4]

No problem! I'm glad to contribute :) I'm trying your solution now, I'll let you know if I'm able to solve the bug (Hoping to have enough time between life and work xD).

If I fix it I'm available to do a PR, do you prefer me working on the dev branch or open a new one?

UPDATE:
Your solution worked I just had to add the pole_pairs to the angle, due to the fact that the open loop function considers electrical angle insted of mechanical ones.

// Encoder alignment the absolute zero angle
// - to the index
int FOCMotor::absoluteZeroSearch() {
  // sensor precision: this is all ok, as the search happens near the 0-angle, where the precision
  //                    of float is sufficient.
  SIMPLEFOC_MOTOR_DEBUG("Index search...");
  // search the absolute zero with small velocity
  float limit_vel = velocity_limit;
  float limit_volt = voltage_limit;
  velocity_limit = velocity_index_search;
  voltage_limit = voltage_sensor_align;
  shaft_angle = 0;
  while(sensor->needsSearch() && shaft_angle < pole_pairs*_2PI){
    angleOpenloop(pole_pairs*1.5f*_2PI);
    // call important for some sensors not to loose count
    // not needed for the search
    sensor->update();
    // set the voltage to the motor
    setPhaseVoltage(voltage_limit, 0, shaft_angle);
  }
  // disable motor
  setPhaseVoltage(0, 0, 0);
  // reinit the limits
  velocity_limit = limit_vel;
  voltage_limit = limit_volt;
  // check if the zero found
  if(monitor_port){
    if(sensor->needsSearch()) { SIMPLEFOC_MOTOR_ERROR("Not found!"); }
    else { SIMPLEFOC_MOTOR_DEBUG("Success!"); }
  }
  return !sensor->needsSearch();
}

The fix is minimal, tell me if you prefer me making a PR or not 👍

[askuric]

Awesome!

Yeah, I'd be happy to have a PR for this.
Maybe just instead of multiplying the target velocity by the pole pairs use the electrical angle function:

Arduino-FOC/src/common/base_classes/FOCMotor.cpp

Line 597 in 7f9c45f

electrical_angle = _electricalAngle((shaft_angle), pole_pairs);

But otherwise it looks good to me!
Thanks

[dekutree64]

The open loop examples also need updated to call loopFOC.