Help needed for closed loop BLDC velocity control with SimpleFOC

VikSauce · May 14, 2026, 2:29pm

Hello!
I am currently struggling to achieved closed loop velocity control of a BLDC motor, and I due to my lack of experience I have not been able to figure out how to resolve my problem.

Here is the problem: upon attempting to run the motor, it stays stuck and cannot be moved by hand while heating up rapidly.

Here is the hardware I am using:

Nucleo 64 stm32 G474RE
SimpleFOC Drive v1.3
24V power supply (2 LiPo 12V batteries in series)
BLDC 42BLS40-24-01 motor from StepperOnline (it has a very low internal resistance)

Here is my code:

#include <Arduino.h>
#include <SimpleFOC.h>

// ─────────────────────────────────────────────
//  USER-TUNABLE PARAMETERS
// ─────────────────────────────────────────────

constexpr int   POLE_PAIRS        = 4;      // 8 magnetic poles → 4 pole-pairs
constexpr float PHASE_RESISTANCE  = 0.30f;  // Ω  (datasheet: ~0.3 Ω/phase)
constexpr float KV_SI             = 260.0f * (float)(M_PI / 30.0); // ≈ 27.2 rad/s/V

constexpr float SUPPLY_VOLTAGE    = 24.0f;  // V

constexpr float CURRENT_LIMIT_A   = 1.0f;   // A (peak phase)

constexpr float TARGET_VELOCITY   = 0.0f;  // rad/s ≈ 478 RPM

// ── Velocity outer-loop PID ──────────────────
constexpr float VEL_P             = 0.5f;
constexpr float VEL_I             = 5.0f;
constexpr float VEL_D             = 0.001f;
constexpr float VEL_TF            = 0.010f;  
constexpr float VEL_RAMP          = 1000.0f; 

// ── Q-axis (torque-producing) current inner-loop PID ────────────────────────
constexpr float CUR_Q_P           = 5.0f;
constexpr float CUR_Q_I           = 300.0f;
constexpr float CUR_Q_D           = 0.0f;
constexpr float CUR_Q_LPF_TF      = 0.002f;  // 2 ms → ~80 Hz LPF on Iq feedback

// ── D-axis (flux) current inner-loop PID ────────────────────────────────────
constexpr float CUR_D_P           = 5.0f;
constexpr float CUR_D_I           = 300.0f;
constexpr float CUR_D_D           = 0.0f;
constexpr float CUR_D_LPF_TF      = 0.002f;

constexpr uint32_t MONITOR_DS     = 12500;

// ─────────────────────────────────────────────
//  HARDWARE OBJECTS
// ─────────────────────────────────────────────

BLDCDriver3PWM driver(
  /* phA */ PA6,   // D6
  /* phB */ PB6,   // D10
  /* phC */ PB4,   // D5
  /* en  */ PA9    // D8
);

InlineCurrentSense current_sense(0.001f, 22.222f, A0, A2);

HallSensor sensor(
  /* H1 */ PA10,   // D2
  /* H2 */ PB3,    // D3
  /* H3 */ PB5,    // D4
  POLE_PAIRS
);

BLDCMotor motor(POLE_PAIRS, PHASE_RESISTANCE, KV_SI);

Commander command(Serial);

// ─────────────────────────────────────────────
//  HALL INTERRUPT CALLBACKS
// ─────────────────────────────────────────────
void doH1() { sensor.handleA(); }
void doH2() { sensor.handleB(); }
void doH3() { sensor.handleC(); }

// ─────────────────────────────────────────────
//  COMMANDER CALLBACKS
// ─────────────────────────────────────────────
void onMotor(char* cmd)  { command.motor(&motor, cmd); }
void onTarget(char* cmd) { command.scalar(&motor.target, cmd); }

// ─────────────────────────────────────────────
//  SETUP
// ─────────────────────────────────────────────
void setup() {
  Serial.begin(115200);
  delay(500);

  Serial.println(F("=== BOOT ==="));

  Serial.println(F("============================================"));
  Serial.println(F("  42BLS40  True-FOC  Velocity Control"));
  Serial.println(F("  SimpleFOC Drive v1.3  /  Nucleo-G474RE"));
  Serial.println(F("  Mode: 3-PWM + inline current sense"));
  Serial.println(F("============================================"));
  Serial.println();

  // ── 1. Hall sensor ───────────────────────────
  sensor.init();
  sensor.enableInterrupts(doH1, doH2, doH3);
  Serial.println(F("[OK] Hall sensor initialised"));

  // ── 2. Gate driver ───────────────────────────
  driver.voltage_power_supply = SUPPLY_VOLTAGE;
  driver.voltage_limit  = SUPPLY_VOLTAGE;
  driver.pwm_frequency  = 25000;  
  if (driver.init() != 1) {
    Serial.println(F("[FATAL] Driver init failed – check PWM/EN wiring. Halting."));
    while (1) {}
  }
  Serial.println(F("[OK] Driver initialised (3-PWM, 25 kHz)"));

  // ── 3. Inline current sense ──────────────────
  current_sense.linkDriver(&driver);
  if (current_sense.init() != 1) {
    Serial.println(F("[FATAL] Current sense init failed – check A0/A2 wiring. Halting."));
    while (1) {}
  }
  // ── Polarity check ───────────────────────────
  Serial.println(F("[OK] Current sense initialised (phases A+B, C reconstructed)"));

  // ── 4. Motor configuration ───────────────────
  motor.linkSensor(&sensor);
  motor.linkDriver(&driver);
  motor.linkCurrentSense(&current_sense);

  // Control topology
  motor.controller        = MotionControlType::velocity;    
  motor.torque_controller = TorqueControlType::foc_current; 

  // Velocity PID
  motor.PID_velocity.P           = VEL_P;
  motor.PID_velocity.I           = VEL_I;
  motor.PID_velocity.D           = VEL_D;
  motor.PID_velocity.output_ramp = VEL_RAMP;
  motor.LPF_velocity.Tf          = VEL_TF;

  // Q-axis current PID
  motor.PID_current_q.P  = CUR_Q_P;
  motor.PID_current_q.I  = CUR_Q_I;
  motor.PID_current_q.D  = CUR_Q_D;
  motor.LPF_current_q.Tf = CUR_Q_LPF_TF;

  // D-axis current PID  
  motor.PID_current_d.P  = CUR_D_P;
  motor.PID_current_d.I  = CUR_D_I;
  motor.PID_current_d.D  = CUR_D_D;
  motor.LPF_current_d.Tf = CUR_D_LPF_TF;

  // Limits
  motor.voltage_sensor_align = 0.5f;
  motor.current_limit  = CURRENT_LIMIT_A;         
  motor.voltage_limit  = 0.5f;
  motor.velocity_limit = 200.0f;                  
  motor.sensor_direction = Direction::CW;

  // ── 5. Monitoring ────────────────────────────
  motor.useMonitoring(Serial);
  motor.monitor_variables  = _MON_TARGET | _MON_VEL | _MON_CURR_Q | _MON_CURR_D;
  motor.monitor_downsample = MONITOR_DS;

  // ── 6. Initialise and calibrate ──────────────
  Serial.println(F("Calling motor.init()..."));
  motor.init();
  Serial.println(F("Calling motor.initFOC()..."));
  motor.initFOC();
  Serial.println(F("[OK] FOC initialised – motor ready"));

  // ── 7. Set initial target ────────────────────
  motor.target = TARGET_VELOCITY;

  // ── 8. Commander ─────────────────────────────
  command.add('M', onMotor,  "motor (full param tree)");
  command.add('T', onTarget, "target velocity [rad/s]");

  Serial.println();
  Serial.println(F("── Runtime commands ──────────────────────────"));
  Serial.println(F("  T<value>   set target velocity (rad/s)"));
  Serial.println(F("  MVP<val>   set velocity P gain"));
  Serial.println(F("  MVI<val>   set velocity I gain"));
  Serial.println(F("  MCQP<val>  set Q-axis current P gain"));
  Serial.println(F("  MCQI<val>  set Q-axis current I gain"));
  Serial.println(F("  ML<val>    set current limit (A)"));
  Serial.println(F("  MS0        disable / coast"));
  Serial.println(F("  MS3        open-loop velocity (diagnostics)"));
  Serial.println(F("  M          print full motor status"));
  Serial.println(F("──────────────────────────────────────────────"));
  Serial.println(F("Monitor columns: target[rad/s], vel[rad/s], Iq[A], Id[A]"));
  Serial.println();
}

// ─────────────────────────────────────────────
//  MAIN LOOP
// ─────────────────────────────────────────────
void loop() {

  motor.loopFOC();

  motor.move();

  motor.monitor();

  command.run();
}

Here is the output of my last test:
=== BOOT ===

42BLS40 True-FOC Velocity Control
SimpleFOC Drive v1.3 / Nucleo-G474RE
Mode: 3-PWM + inline current sense

[OK] Hall sensor initialised
[OK] Driver initialised (3-PWM, 25 kHz)
[OK] Current sense initialised (phases A+B, C reconstructed)
MOT:Monitor enabled!
Calling motor.init()…
MOT:Init
MOT:Enable driver.
Calling motor.initFOC()…
MOT:Align sensor.
MOT:Skip dir calib.
MOT:Zero elec. angle: 0.00
MOT:Align current sense.
MOT:Success: 1
MOT:Ready.
[OK] FOC initialised – motor ready
── Runtime commands ──────────────────────────
T set target velocity (rad/s)
MVP set velocity P gain
MVI set velocity I gain
MCQP set Q-axis current P gain
MCQI set Q-axis current I gain
ML set current limit (A)
MS0 disable / coast
MS3 open-loop velocity (diagnostics)
M print full motor status
──────────────────────────────────────────────
Monitor columns: target[rad/s], vel[rad/s], Iq[A], Id[A]
0.0000 8317.2216 2984.8823 0.0000
0.0000 7919.0249 2817.5078 0.0000
0.0000 7588.7368 2751.7604 0.0000
0.0000 7298.4711 2631.5268 0.0000

Here is a photo of my setup:

Any help is greatly appreciated!

dekutree64 · May 14, 2026, 8:45pm

Have you tried setting the target to something other than 0? Holding position is the expected behavior for commanding 0 velocity in open loop. If so, and it still won’t move, then try disconnecting the motor and checking the output voltages (relative to ground) with a multimeter. Use angle open loop mode and change the target angle and motor.voltage_limit and see if the measured voltages change accordingly.

VikSauce · May 15, 2026, 10:22am

Thank you for the reply! Yes the motor does not move regardless of the target velocity, I just set it to 0 in this case to check if the motor would still heat up rapidly if it was not asked to move, which it did . I unfortunately do not have access to a multimeter at the moment, are there any other tests I could try to identify the source of the problem (whether it is the motor, wiring, or the code)?

Antun_Skuric · May 15, 2026, 1:26pm

Hey there,

The best idea might be to start with the getting started guide.
It’s simple and you should be able to pin point the main issues a bit quicker.

o_lampe · May 16, 2026, 9:08pm

I have a similar motor (act 42BLF01) with almost the same numbers, except it has 2.2ohm phase to phase resistance. For simplefoc I have to set 1.1ohm (single phase)

It wouldn’t hurt to try the same number.

VikSauce · May 17, 2026, 12:11pm

I think the main problem I’m facing is the fact that I cannot seem to read the information from the hall sensors, no matter what I try .

I’ve been trying to get this to work with this motor for a while now and I think I might pivot to an entirely different set up, because I can not figure it out.

o_lampe · May 17, 2026, 1:01pm

Then raise that value, 0.5 V is pretty low for a 24V motor.

VikSauce · May 17, 2026, 1:47pm

I am not sure if that is the source of the problem, as I get no input from the hall sensors at all when using the code from the get started guide to test the sensor (https://docs.simplefoc.com/test_sensor), it simply stays at 0 for the angle and velocity.

I tried multiple different pins, to no avail.

Help needed for closed loop BLDC velocity control with SimpleFOC

7 Answers