Index search routine

Finding the encoder index is performed only if the constructor of the Encoder class has been provided with the index pin. The search is performed by setting a constant velocity of the motor until it reaches the index pin. To set the desired searching velocity alter the parameter:

// index search velocity - default 1rad/s
motor.velocity_index_search = 2;

The index search is executed in the motor.initFOC() function.

This velocity control loop is implemented exactly the same as velocity open-loop and the only difference is that the voltage set to the motor will not be the motor.volatge_limit (or motor.curren_limit*motor.phase_resistance) but motor.voltage_sensor_align.

Example of code using Index search

This is an example of a motion control program which uses encoder as position sensor and particularly, encoder with index signal. The index search velocity is set to be 3 RAD/s:

// index search velocity [rad/s]
motor.velocity_index_search = 3;

After the motor and the position senor have been aligned in motor.initFOC() by performing index search. The motor will start spinning with angular velocity 2 RAD/s and maintain this value.

#include <SimpleFOC.h>

// motor instance
BLDCMotor motor = BLDCMotor(11);
// driver instance
BLDCDriver3PWM driver = BLDCDriver3PWM(9, 10, 11, 8);

// encoder instance
Encoder encoder = Encoder(2, 3, 500, A0);
// channel A and B callbacks
void doA(){encoder.handleA();}
void doB(){encoder.handleB();}
void doIndex(){encoder.handleIndex();}


void setup() {
  
  // initialize encoder sensor hardware
  encoder.init();
  encoder.enableInterrupts(doA, doB,doIndex); 

  // link the motor to the sensor
  motor.linkSensor(&encoder);

  // driver config
  driver.init();
  motor.linkDriver(&driver);

  // index search velocity [rad/s]
  motor.velocity_index_search = 3; // rad/s
  motor.voltage_sensor_align = 4; // Volts

  // set motion control loop to be used
  motor.controller = MotionControlType::velocity;

  // controller configuration 
  // default parameters in defaults.h

  // velocity PI controller parameters
  motor.PID_velocity.P = 0.2;
  motor.PID_velocity.I = 20;
  // default voltage_power_supply
  motor.voltage_limit = 6;
  // jerk control using voltage voltage ramp
  // default value is 300 volts per sec  ~ 0.3V per millisecond
  motor.PID_velocity.output_ramp = 1000;
 
  // velocity low pass filtering time constant
  motor.LPF_velocity.Tf = 0.01;


  // use monitoring with serial 
  Serial.begin(115200);
  // comment out if not needed
  motor.useMonitoring(Serial);
  
  // initialize motor
  motor.init();
  // align encoder and start FOC
  motor.initFOC();


  Serial.println("Motor ready.");
  _delay(1000);
}

// angle set point variable
float target_velocity = 2;

void loop() {
  // main FOC algorithm function
  motor.loopFOC();

  // Motion control function
  motor.move(target_velocity);

}