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BLDCMotor.cpp
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BLDCMotor.cpp
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#include "BLDCMotor.h"
#include "./communication/SimpleFOCDebug.h"
// see https://www.youtube.com/watch?v=InzXA7mWBWE Slide 5
// each is 60 degrees with values for 3 phases of 1=positive -1=negative 0=high-z
int trap_120_map[6][3] = {
{_HIGH_IMPEDANCE,1,-1},
{-1,1,_HIGH_IMPEDANCE},
{-1,_HIGH_IMPEDANCE,1},
{_HIGH_IMPEDANCE,-1,1},
{1,-1,_HIGH_IMPEDANCE},
{1,_HIGH_IMPEDANCE,-1}
};
// see https://www.youtube.com/watch?v=InzXA7mWBWE Slide 8
// each is 30 degrees with values for 3 phases of 1=positive -1=negative 0=high-z
int trap_150_map[12][3] = {
{_HIGH_IMPEDANCE,1,-1},
{-1,1,-1},
{-1,1,_HIGH_IMPEDANCE},
{-1,1,1},
{-1,_HIGH_IMPEDANCE,1},
{-1,-1,1},
{_HIGH_IMPEDANCE,-1,1},
{1,-1,1},
{1,-1,_HIGH_IMPEDANCE},
{1,-1,-1},
{1,_HIGH_IMPEDANCE,-1},
{1,1,-1}
};
// BLDCMotor( int pp , float R)
// - pp - pole pair number
// - R - motor phase resistance
// - KV - motor kv rating (rmp/v)
// - L - motor phase inductance
BLDCMotor::BLDCMotor(int pp, float _R, float _KV, float _inductance)
: FOCMotor()
{
// save pole pairs number
pole_pairs = pp;
// save phase resistance number
phase_resistance = _R;
// save back emf constant KV = 1/KV
// 1/sqrt(2) - rms value
KV_rating = NOT_SET;
if (_isset(_KV))
KV_rating = _KV*_SQRT2;
// save phase inductance
phase_inductance = _inductance;
// torque control type is voltage by default
torque_controller = TorqueControlType::voltage;
}
/**
Link the driver which controls the motor
*/
void BLDCMotor::linkDriver(BLDCDriver* _driver) {
driver = _driver;
}
// init hardware pins
void BLDCMotor::init() {
if (!driver || !driver->initialized) {
motor_status = FOCMotorStatus::motor_init_failed;
SIMPLEFOC_DEBUG("MOT: Init not possible, driver not initialized");
return;
}
motor_status = FOCMotorStatus::motor_initializing;
SIMPLEFOC_DEBUG("MOT: Init");
// sanity check for the voltage limit configuration
if(voltage_limit > driver->voltage_limit) voltage_limit = driver->voltage_limit;
// constrain voltage for sensor alignment
if(voltage_sensor_align > voltage_limit) voltage_sensor_align = voltage_limit;
// update the controller limits
if(current_sense){
// current control loop controls voltage
PID_current_q.limit = voltage_limit;
PID_current_d.limit = voltage_limit;
}
if(_isset(phase_resistance) || torque_controller != TorqueControlType::voltage){
// velocity control loop controls current
PID_velocity.limit = current_limit;
}else{
// velocity control loop controls the voltage
PID_velocity.limit = voltage_limit;
}
P_angle.limit = velocity_limit;
// if using open loop control, set a CW as the default direction if not already set
if ((controller==MotionControlType::angle_openloop
||controller==MotionControlType::velocity_openloop)
&& (sensor_direction == Direction::UNKNOWN)) {
sensor_direction = Direction::CW;
}
_delay(500);
// enable motor
SIMPLEFOC_DEBUG("MOT: Enable driver.");
enable();
_delay(500);
motor_status = FOCMotorStatus::motor_uncalibrated;
}
// disable motor driver
void BLDCMotor::disable()
{
// set zero to PWM
driver->setPwm(0, 0, 0);
// disable the driver
driver->disable();
// motor status update
enabled = 0;
}
// enable motor driver
void BLDCMotor::enable()
{
// enable the driver
driver->enable();
// set zero to PWM
driver->setPwm(0, 0, 0);
// motor status update
enabled = 1;
}
/**
FOC functions
*/
// FOC initialization function
int BLDCMotor::initFOC() {
int exit_flag = 1;
motor_status = FOCMotorStatus::motor_calibrating;
// align motor if necessary
// alignment necessary for encoders!
// sensor and motor alignment - can be skipped
// by setting motor.sensor_direction and motor.zero_electric_angle
_delay(500);
if(sensor){
exit_flag *= alignSensor();
// added the shaft_angle update
sensor->update();
shaft_angle = shaftAngle();
}else {
exit_flag = 0; // no FOC without sensor
SIMPLEFOC_DEBUG("MOT: No sensor.");
}
// aligning the current sensor - can be skipped
// checks if driver phases are the same as current sense phases
// and checks the direction of measuremnt.
_delay(500);
if(exit_flag){
if(current_sense){
if (!current_sense->initialized) {
motor_status = FOCMotorStatus::motor_calib_failed;
SIMPLEFOC_DEBUG("MOT: Init FOC error, current sense not initialized");
exit_flag = 0;
}else{
exit_flag *= alignCurrentSense();
}
}
else { SIMPLEFOC_DEBUG("MOT: No current sense."); }
}
if(exit_flag){
SIMPLEFOC_DEBUG("MOT: Ready.");
motor_status = FOCMotorStatus::motor_ready;
}else{
SIMPLEFOC_DEBUG("MOT: Init FOC failed.");
motor_status = FOCMotorStatus::motor_calib_failed;
disable();
}
return exit_flag;
}
// Calibarthe the motor and current sense phases
int BLDCMotor::alignCurrentSense() {
int exit_flag = 1; // success
SIMPLEFOC_DEBUG("MOT: Align current sense.");
// align current sense and the driver
exit_flag = current_sense->driverAlign(voltage_sensor_align);
if(!exit_flag){
// error in current sense - phase either not measured or bad connection
SIMPLEFOC_DEBUG("MOT: Align error!");
exit_flag = 0;
}else{
// output the alignment status flag
SIMPLEFOC_DEBUG("MOT: Success: ", exit_flag);
}
return exit_flag > 0;
}
// Encoder alignment to electrical 0 angle
int BLDCMotor::alignSensor() {
int exit_flag = 1; //success
SIMPLEFOC_DEBUG("MOT: Align sensor.");
// check if sensor needs zero search
if(sensor->needsSearch()) exit_flag = absoluteZeroSearch();
// stop init if not found index
if(!exit_flag) return exit_flag;
// if unknown natural direction
if(sensor_direction==Direction::UNKNOWN){
// find natural direction
// move one electrical revolution forward
for (int i = 0; i <=500; i++ ) {
float angle = _3PI_2 + _2PI * i / 500.0f;
setPhaseVoltage(voltage_sensor_align, 0, angle);
sensor->update();
_delay(2);
}
// take and angle in the middle
sensor->update();
float mid_angle = sensor->getAngle();
// move one electrical revolution backwards
for (int i = 500; i >=0; i-- ) {
float angle = _3PI_2 + _2PI * i / 500.0f ;
setPhaseVoltage(voltage_sensor_align, 0, angle);
sensor->update();
_delay(2);
}
sensor->update();
float end_angle = sensor->getAngle();
setPhaseVoltage(0, 0, 0);
_delay(200);
// determine the direction the sensor moved
float moved = fabs(mid_angle - end_angle);
if (moved<MIN_ANGLE_DETECT_MOVEMENT) { // minimum angle to detect movement
SIMPLEFOC_DEBUG("MOT: Failed to notice movement");
return 0; // failed calibration
} else if (mid_angle < end_angle) {
SIMPLEFOC_DEBUG("MOT: sensor_direction==CCW");
sensor_direction = Direction::CCW;
} else{
SIMPLEFOC_DEBUG("MOT: sensor_direction==CW");
sensor_direction = Direction::CW;
}
// check pole pair number
if( fabs(moved*pole_pairs - _2PI) > 0.5f ) { // 0.5f is arbitrary number it can be lower or higher!
SIMPLEFOC_DEBUG("MOT: PP check: fail - estimated pp: ", _2PI/moved);
} else {
SIMPLEFOC_DEBUG("MOT: PP check: OK!");
}
} else { SIMPLEFOC_DEBUG("MOT: Skip dir calib."); }
// zero electric angle not known
if(!_isset(zero_electric_angle)){
// align the electrical phases of the motor and sensor
// set angle -90(270 = 3PI/2) degrees
setPhaseVoltage(voltage_sensor_align, 0, _3PI_2);
_delay(700);
// read the sensor
sensor->update();
// get the current zero electric angle
zero_electric_angle = 0;
zero_electric_angle = electricalAngle();
//zero_electric_angle = _normalizeAngle(_electricalAngle(sensor_direction*sensor->getAngle(), pole_pairs));
_delay(20);
if(monitor_port){
SIMPLEFOC_DEBUG("MOT: Zero elec. angle: ", zero_electric_angle);
}
// stop everything
setPhaseVoltage(0, 0, 0);
_delay(200);
} else { SIMPLEFOC_DEBUG("MOT: Skip offset calib."); }
return exit_flag;
}
// Encoder alignment the absolute zero angle
// - to the index
int BLDCMotor::absoluteZeroSearch() {
// sensor precision: this is all ok, as the search happens near the 0-angle, where the precision
// of float is sufficient.
SIMPLEFOC_DEBUG("MOT: 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 < _2PI){
angleOpenloop(1.5f*_2PI);
// call important for some sensors not to loose count
// not needed for the search
sensor->update();
}
// 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_DEBUG("MOT: Error: Not found!"); }
else { SIMPLEFOC_DEBUG("MOT: Success!"); }
}
return !sensor->needsSearch();
}
// Iterative function looping FOC algorithm, setting Uq on the Motor
// The faster it can be run the better
void BLDCMotor::loopFOC() {
// update sensor - do this even in open-loop mode, as user may be switching between modes and we could lose track
// of full rotations otherwise.
if (sensor) sensor->update();
// if open-loop do nothing
if( controller==MotionControlType::angle_openloop || controller==MotionControlType::velocity_openloop ) return;
// if disabled do nothing
if(!enabled) return;
// Needs the update() to be called first
// This function will not have numerical issues because it uses Sensor::getMechanicalAngle()
// which is in range 0-2PI
electrical_angle = electricalAngle();
switch (torque_controller) {
case TorqueControlType::voltage:
// no need to do anything really
break;
case TorqueControlType::dc_current:
if(!current_sense) return;
// read overall current magnitude
current.q = current_sense->getDCCurrent(electrical_angle);
// filter the value values
current.q = LPF_current_q(current.q);
// calculate the phase voltage
voltage.q = PID_current_q(current_sp - current.q);
// d voltage - lag compensation
if(_isset(phase_inductance)) voltage.d = _constrain( -current_sp*shaft_velocity*pole_pairs*phase_inductance, -voltage_limit, voltage_limit);
else voltage.d = 0;
break;
case TorqueControlType::foc_current:
if(!current_sense) return;
// read dq currents
current = current_sense->getFOCCurrents(electrical_angle);
// filter values
current.q = LPF_current_q(current.q);
current.d = LPF_current_d(current.d);
// calculate the phase voltages
voltage.q = PID_current_q(current_sp - current.q);
voltage.d = PID_current_d(-current.d);
// d voltage - lag compensation - TODO verify
// if(_isset(phase_inductance)) voltage.d = _constrain( voltage.d - current_sp*shaft_velocity*pole_pairs*phase_inductance, -voltage_limit, voltage_limit);
break;
default:
// no torque control selected
SIMPLEFOC_DEBUG("MOT: no torque control selected!");
break;
}
// set the phase voltage - FOC heart function :)
setPhaseVoltage(voltage.q, voltage.d, electrical_angle);
}
// Iterative function running outer loop of the FOC algorithm
// Behavior of this function is determined by the motor.controller variable
// It runs either angle, velocity or torque loop
// - needs to be called iteratively it is asynchronous function
// - if target is not set it uses motor.target value
void BLDCMotor::move(float new_target) {
// downsampling (optional)
if(motion_cnt++ < motion_downsample) return;
motion_cnt = 0;
// shaft angle/velocity need the update() to be called first
// get shaft angle
// TODO sensor precision: the shaft_angle actually stores the complete position, including full rotations, as a float
// For this reason it is NOT precise when the angles become large.
// Additionally, the way LPF works on angle is a precision issue, and the angle-LPF is a problem
// when switching to a 2-component representation.
if( controller!=MotionControlType::angle_openloop && controller!=MotionControlType::velocity_openloop )
shaft_angle = shaftAngle(); // read value even if motor is disabled to keep the monitoring updated but not in openloop mode
// get angular velocity TODO the velocity reading probably also shouldn't happen in open loop modes?
shaft_velocity = shaftVelocity(); // read value even if motor is disabled to keep the monitoring updated
// if disabled do nothing
if(!enabled) return;
// set internal target variable
if(_isset(new_target)) target = new_target;
// calculate the back-emf voltage if KV_rating available U_bemf = vel*(1/KV)
if (_isset(KV_rating)) voltage_bemf = shaft_velocity/KV_rating/_RPM_TO_RADS;
// estimate the motor current if phase reistance available and current_sense not available
if(!current_sense && _isset(phase_resistance)) current.q = (voltage.q - voltage_bemf)/phase_resistance;
// upgrade the current based voltage limit
switch (controller) {
case MotionControlType::torque:
if(torque_controller == TorqueControlType::voltage){ // if voltage torque control
if(!_isset(phase_resistance)) voltage.q = target;
else voltage.q = target*phase_resistance + voltage_bemf;
voltage.q = _constrain(voltage.q, -voltage_limit, voltage_limit);
// set d-component (lag compensation if known inductance)
if(!_isset(phase_inductance)) voltage.d = 0;
else voltage.d = _constrain( -target*shaft_velocity*pole_pairs*phase_inductance, -voltage_limit, voltage_limit);
}else{
current_sp = target; // if current/foc_current torque control
}
break;
case MotionControlType::angle:
// TODO sensor precision: this calculation is not numerically precise. The target value cannot express precise positions when
// the angles are large. This results in not being able to command small changes at high position values.
// to solve this, the delta-angle has to be calculated in a numerically precise way.
// angle set point
shaft_angle_sp = target;
// calculate velocity set point
shaft_velocity_sp = feed_forward_velocity + P_angle( shaft_angle_sp - shaft_angle );
shaft_velocity_sp = _constrain(shaft_velocity_sp,-velocity_limit, velocity_limit);
// calculate the torque command - sensor precision: this calculation is ok, but based on bad value from previous calculation
current_sp = PID_velocity(shaft_velocity_sp - shaft_velocity); // if voltage torque control
// if torque controlled through voltage
if(torque_controller == TorqueControlType::voltage){
// use voltage if phase-resistance not provided
if(!_isset(phase_resistance)) voltage.q = current_sp;
else voltage.q = _constrain( current_sp*phase_resistance + voltage_bemf , -voltage_limit, voltage_limit);
// set d-component (lag compensation if known inductance)
if(!_isset(phase_inductance)) voltage.d = 0;
else voltage.d = _constrain( -current_sp*shaft_velocity*pole_pairs*phase_inductance, -voltage_limit, voltage_limit);
}
break;
case MotionControlType::velocity:
// velocity set point - sensor precision: this calculation is numerically precise.
shaft_velocity_sp = target;
// calculate the torque command
current_sp = PID_velocity(shaft_velocity_sp - shaft_velocity); // if current/foc_current torque control
// if torque controlled through voltage control
if(torque_controller == TorqueControlType::voltage){
// use voltage if phase-resistance not provided
if(!_isset(phase_resistance)) voltage.q = current_sp;
else voltage.q = _constrain( current_sp*phase_resistance + voltage_bemf , -voltage_limit, voltage_limit);
// set d-component (lag compensation if known inductance)
if(!_isset(phase_inductance)) voltage.d = 0;
else voltage.d = _constrain( -current_sp*shaft_velocity*pole_pairs*phase_inductance, -voltage_limit, voltage_limit);
}
break;
case MotionControlType::velocity_openloop:
// velocity control in open loop - sensor precision: this calculation is numerically precise.
shaft_velocity_sp = target;
voltage.q = velocityOpenloop(shaft_velocity_sp); // returns the voltage that is set to the motor
voltage.d = 0;
break;
case MotionControlType::angle_openloop:
// angle control in open loop -
// TODO sensor precision: this calculation NOT numerically precise, and subject
// to the same problems in small set-point changes at high angles
// as the closed loop version.
shaft_angle_sp = target;
voltage.q = angleOpenloop(shaft_angle_sp); // returns the voltage that is set to the motor
voltage.d = 0;
break;
}
}
// Method using FOC to set Uq and Ud to the motor at the optimal angle
// Function implementing Space Vector PWM and Sine PWM algorithms
//
// Function using sine approximation
// regular sin + cos ~300us (no memory usage)
// approx _sin + _cos ~110us (400Byte ~ 20% of memory)
void BLDCMotor::setPhaseVoltage(float Uq, float Ud, float angle_el) {
float center;
int sector;
float _ca,_sa;
switch (foc_modulation)
{
case FOCModulationType::Trapezoid_120 :
// see https://www.youtube.com/watch?v=InzXA7mWBWE Slide 5
// determine the sector
sector = 6 * (_normalizeAngle(angle_el + _PI_6 ) / _2PI); // adding PI/6 to align with other modes
// centering the voltages around either
// modulation_centered == true > driver.voltage_limit/2
// modulation_centered == false > or Adaptable centering, all phases drawn to 0 when Uq=0
center = modulation_centered ? (driver->voltage_limit)/2 : Uq;
if(trap_120_map[sector][0] == _HIGH_IMPEDANCE){
Ua= center;
Ub = trap_120_map[sector][1] * Uq + center;
Uc = trap_120_map[sector][2] * Uq + center;
driver->setPhaseState(PhaseState::PHASE_OFF, PhaseState::PHASE_ON, PhaseState::PHASE_ON); // disable phase if possible
}else if(trap_120_map[sector][1] == _HIGH_IMPEDANCE){
Ua = trap_120_map[sector][0] * Uq + center;
Ub = center;
Uc = trap_120_map[sector][2] * Uq + center;
driver->setPhaseState(PhaseState::PHASE_ON, PhaseState::PHASE_OFF, PhaseState::PHASE_ON);// disable phase if possible
}else{
Ua = trap_120_map[sector][0] * Uq + center;
Ub = trap_120_map[sector][1] * Uq + center;
Uc = center;
driver->setPhaseState(PhaseState::PHASE_ON, PhaseState::PHASE_ON, PhaseState::PHASE_OFF);// disable phase if possible
}
break;
case FOCModulationType::Trapezoid_150 :
// see https://www.youtube.com/watch?v=InzXA7mWBWE Slide 8
// determine the sector
sector = 12 * (_normalizeAngle(angle_el + _PI_6 ) / _2PI); // adding PI/6 to align with other modes
// centering the voltages around either
// modulation_centered == true > driver.voltage_limit/2
// modulation_centered == false > or Adaptable centering, all phases drawn to 0 when Uq=0
center = modulation_centered ? (driver->voltage_limit)/2 : Uq;
if(trap_150_map[sector][0] == _HIGH_IMPEDANCE){
Ua= center;
Ub = trap_150_map[sector][1] * Uq + center;
Uc = trap_150_map[sector][2] * Uq + center;
driver->setPhaseState(PhaseState::PHASE_OFF, PhaseState::PHASE_ON, PhaseState::PHASE_ON); // disable phase if possible
}else if(trap_150_map[sector][1] == _HIGH_IMPEDANCE){
Ua = trap_150_map[sector][0] * Uq + center;
Ub = center;
Uc = trap_150_map[sector][2] * Uq + center;
driver->setPhaseState(PhaseState::PHASE_ON, PhaseState::PHASE_OFF, PhaseState::PHASE_ON); // disable phase if possible
}else if(trap_150_map[sector][2] == _HIGH_IMPEDANCE){
Ua = trap_150_map[sector][0] * Uq + center;
Ub = trap_150_map[sector][1] * Uq + center;
Uc = center;
driver->setPhaseState(PhaseState::PHASE_ON, PhaseState::PHASE_ON, PhaseState::PHASE_OFF); // disable phase if possible
}else{
Ua = trap_150_map[sector][0] * Uq + center;
Ub = trap_150_map[sector][1] * Uq + center;
Uc = trap_150_map[sector][2] * Uq + center;
driver->setPhaseState(PhaseState::PHASE_ON, PhaseState::PHASE_ON, PhaseState::PHASE_ON); // enable all phases
}
break;
case FOCModulationType::SinePWM :
case FOCModulationType::SpaceVectorPWM :
// Sinusoidal PWM modulation
// Inverse Park + Clarke transformation
_sincos(angle_el, &_sa, &_ca);
// Inverse park transform
Ualpha = _ca * Ud - _sa * Uq; // -sin(angle) * Uq;
Ubeta = _sa * Ud + _ca * Uq; // cos(angle) * Uq;
// Clarke transform
Ua = Ualpha;
Ub = -0.5f * Ualpha + _SQRT3_2 * Ubeta;
Uc = -0.5f * Ualpha - _SQRT3_2 * Ubeta;
center = driver->voltage_limit/2;
if (foc_modulation == FOCModulationType::SpaceVectorPWM){
// discussed here: https://community.simplefoc.com/t/embedded-world-2023-stm32-cordic-co-processor/3107/165?u=candas1
// a bit more info here: https://microchipdeveloper.com/mct5001:which-zsm-is-best
// Midpoint Clamp
float Umin = min(Ua, min(Ub, Uc));
float Umax = max(Ua, max(Ub, Uc));
center -= (Umax+Umin) / 2;
}
if (!modulation_centered) {
float Umin = min(Ua, min(Ub, Uc));
Ua -= Umin;
Ub -= Umin;
Uc -= Umin;
}else{
Ua += center;
Ub += center;
Uc += center;
}
break;
}
// set the voltages in driver
driver->setPwm(Ua, Ub, Uc);
}
// Function (iterative) generating open loop movement for target velocity
// - target_velocity - rad/s
// it uses voltage_limit variable
float BLDCMotor::velocityOpenloop(float target_velocity){
// get current timestamp
unsigned long now_us = _micros();
// calculate the sample time from last call
float Ts = (now_us - open_loop_timestamp) * 1e-6f;
// quick fix for strange cases (micros overflow + timestamp not defined)
if(Ts <= 0 || Ts > 0.5f) Ts = 1e-3f;
// calculate the necessary angle to achieve target velocity
shaft_angle = _normalizeAngle(shaft_angle + target_velocity*Ts);
// for display purposes
shaft_velocity = target_velocity;
// use voltage limit or current limit
float Uq = voltage_limit;
if(_isset(phase_resistance)){
Uq = _constrain(current_limit*phase_resistance + fabs(voltage_bemf),-voltage_limit, voltage_limit);
// recalculate the current
current.q = (Uq - fabs(voltage_bemf))/phase_resistance;
}
// set the maximal allowed voltage (voltage_limit) with the necessary angle
setPhaseVoltage(Uq, 0, _electricalAngle(shaft_angle, pole_pairs));
// save timestamp for next call
open_loop_timestamp = now_us;
return Uq;
}
// Function (iterative) generating open loop movement towards the target angle
// - target_angle - rad
// it uses voltage_limit and velocity_limit variables
float BLDCMotor::angleOpenloop(float target_angle){
// get current timestamp
unsigned long now_us = _micros();
// calculate the sample time from last call
float Ts = (now_us - open_loop_timestamp) * 1e-6f;
// quick fix for strange cases (micros overflow + timestamp not defined)
if(Ts <= 0 || Ts > 0.5f) Ts = 1e-3f;
// calculate the necessary angle to move from current position towards target angle
// with maximal velocity (velocity_limit)
// TODO sensor precision: this calculation is not numerically precise. The angle can grow to the point
// where small position changes are no longer captured by the precision of floats
// when the total position is large.
if(abs( target_angle - shaft_angle ) > abs(velocity_limit*Ts)){
shaft_angle += _sign(target_angle - shaft_angle) * abs( velocity_limit )*Ts;
shaft_velocity = velocity_limit;
}else{
shaft_angle = target_angle;
shaft_velocity = 0;
}
// use voltage limit or current limit
float Uq = voltage_limit;
if(_isset(phase_resistance)){
Uq = _constrain(current_limit*phase_resistance + fabs(voltage_bemf),-voltage_limit, voltage_limit);
// recalculate the current
current.q = (Uq - fabs(voltage_bemf))/phase_resistance;
}
// set the maximal allowed voltage (voltage_limit) with the necessary angle
// sensor precision: this calculation is OK due to the normalisation
setPhaseVoltage(Uq, 0, _electricalAngle(_normalizeAngle(shaft_angle), pole_pairs));
// save timestamp for next call
open_loop_timestamp = now_us;
return Uq;
}