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ardupilot/libraries/AP_Motors/AP_MotorsMulticopter.cpp

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/*
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
/*
* AP_MotorsMulticopter.cpp - ArduCopter multicopter motors library
* Code by Randy Mackay and Robert Lefebvre. DIYDrones.com
*
*/
#include "AP_MotorsMulticopter.h"
#include <AP_HAL/AP_HAL.h>
extern const AP_HAL::HAL& hal;
// parameters for the motor class
const AP_Param::GroupInfo AP_MotorsMulticopter::var_info[] = {
// 0 was used by TB_RATIO
// 1,2,3 were used by throttle curve
// 5 was SPIN_ARMED
// @Param: YAW_HEADROOM
// @DisplayName: Matrix Yaw Min
// @Description: Yaw control is given at least this pwm range
// @Range: 0 500
// @Units: pwm
// @User: Advanced
AP_GROUPINFO("YAW_HEADROOM", 6, AP_MotorsMulticopter, _yaw_headroom, AP_MOTORS_YAW_HEADROOM_DEFAULT),
// 7 was THR_LOW_CMP
// @Param: THST_EXPO
// @DisplayName: Thrust Curve Expo
// @Description: Motor thrust curve exponent (from 0 for linear to 1.0 for second order curve)
// @Range: 0.25 0.8
// @User: Advanced
AP_GROUPINFO("THST_EXPO", 8, AP_MotorsMulticopter, _thrust_curve_expo, AP_MOTORS_THST_EXPO_DEFAULT),
// @Param: SPIN_MAX
// @DisplayName: Motor Spin maximum
// @Description: Point at which the thrust saturates expressed as a number from 0 to 1 in the entire output range
// @Values: 0.9:Low, 0.95:Default, 1.0:High
// @User: Advanced
AP_GROUPINFO("SPIN_MAX", 9, AP_MotorsMulticopter, _spin_max, AP_MOTORS_SPIN_MAX_DEFAULT),
// @Param: BAT_VOLT_MAX
// @DisplayName: Battery voltage compensation maximum voltage
// @Description: Battery voltage compensation maximum voltage (voltage above this will have no additional scaling effect on thrust). Recommend 4.4 * cell count, 0 = Disabled
// @Range: 6 35
// @Units: Volts
// @User: Advanced
AP_GROUPINFO("BAT_VOLT_MAX", 10, AP_MotorsMulticopter, _batt_voltage_max, AP_MOTORS_BAT_VOLT_MAX_DEFAULT),
// @Param: BAT_VOLT_MIN
// @DisplayName: Battery voltage compensation minimum voltage
// @Description: Battery voltage compensation minimum voltage (voltage below this will have no additional scaling effect on thrust). Recommend 3.5 * cell count, 0 = Disabled
// @Range: 6 35
// @Units: Volts
// @User: Advanced
AP_GROUPINFO("BAT_VOLT_MIN", 11, AP_MotorsMulticopter, _batt_voltage_min, AP_MOTORS_BAT_VOLT_MIN_DEFAULT),
// @Param: BAT_CURR_MAX
// @DisplayName: Motor Current Max
// @Description: Maximum current over which maximum throttle is limited (0 = Disabled)
// @Range: 0 200
// @Units: Amps
// @User: Advanced
AP_GROUPINFO("BAT_CURR_MAX", 12, AP_MotorsMulticopter, _batt_current_max, AP_MOTORS_BAT_CURR_MAX_DEFAULT),
// 13, 14 were used by THR_MIX_MIN, THR_MIX_MAX
// @Param: PWM_TYPE
// @DisplayName: Output PWM type
// @Description: This selects the output PWM type, allowing for normal PWM continuous output or OneShot125
// @Values: 0:Normal,1:OneShot,2:OneShot125
// @User: Advanced
AP_GROUPINFO("PWM_TYPE", 15, AP_MotorsMulticopter, _pwm_type, PWM_TYPE_NORMAL),
// @Param: PWM_MIN
// @DisplayName: PWM output miniumum
// @Description: This sets the min PWM output value that will ever be output to the motors, 0 = use input RC3_MIN
// @Range: 0 2000
// @User: Advanced
AP_GROUPINFO("PWM_MIN", 16, AP_MotorsMulticopter, _pwm_min, 0),
// @Param: PWM_MAX
// @DisplayName: PWM output maximum
// @Description: This sets the max PWM value that will ever be output to the motors, 0 = use input RC3_MAX
// @Range: 0 2000
// @User: Advanced
AP_GROUPINFO("PWM_MAX", 17, AP_MotorsMulticopter, _pwm_max, 0),
// @Param: SPIN_MIN
// @DisplayName: Motor Spin minimum
// @Description: Point at which the thrust starts expressed as a number from 0 to 1 in the entire output range. Should be higher than MOT_SPIN_ARM.
// @Values: 0.0:Low, 0.15:Default, 0.3:High
// @User: Advanced
AP_GROUPINFO("SPIN_MIN", 18, AP_MotorsMulticopter, _spin_min, AP_MOTORS_SPIN_MIN_DEFAULT),
// @Param: SPIN_ARM
// @DisplayName: Motor Spin armed
// @Description: Point at which the motors start to spin expressed as a number from 0 to 1 in the entire output range. Should be lower than MOT_SPIN_MIN.
// @Values: 0.0:Low, 0.1:Default, 0.2:High
// @User: Advanced
AP_GROUPINFO("SPIN_ARM", 19, AP_MotorsMulticopter, _spin_arm, AP_MOTORS_SPIN_ARM_DEFAULT),
// @Param: BAT_CURR_TC
// @DisplayName: Motor Current Max Time Constant
// @Description: Time constant used to limit the maximum current
// @Range: 0 10
// @Units: Seconds
// @User: Advanced
AP_GROUPINFO("BAT_CURR_TC", 20, AP_MotorsMulticopter, _batt_current_time_constant, AP_MOTORS_BAT_CURR_TC_DEFAULT),
// @Param: THST_HOVER
// @DisplayName: Thrust Hover Value
// @Description: Motor thrust needed to hover expressed as a number from 0 to 1
// @Range: 0.2 0.8
// @User: Advanced
AP_GROUPINFO("THST_HOVER", 21, AP_MotorsMulticopter, _throttle_hover, AP_MOTORS_THST_HOVER_DEFAULT),
// @Param: HOVER_LEARN
// @DisplayName: Hover Value Learning
// @Description: Enable/Disable automatic learning of hover throttle
// @Values: 0:Disabled, 1:Learn, 2:LearnAndSave
// @User: Advanced
AP_GROUPINFO("HOVER_LEARN", 22, AP_MotorsMulticopter, _throttle_hover_learn, HOVER_LEARN_AND_SAVE),
AP_GROUPEND
};
// Constructor
AP_MotorsMulticopter::AP_MotorsMulticopter(uint16_t loop_rate, uint16_t speed_hz) :
AP_Motors(loop_rate, speed_hz),
_spool_mode(SHUT_DOWN),
_spin_up_ratio(0.0f),
_batt_voltage_resting(0.0f),
_batt_current_resting(0.0f),
_batt_resistance(0.0f),
_batt_timer(0),
_lift_max(1.0f),
_throttle_limit(1.0f),
_throttle_thrust_max(0.0f)
{
AP_Param::setup_object_defaults(this, var_info);
// disable all motors by default
memset(motor_enabled, false, sizeof(motor_enabled));
// setup battery voltage filtering
_batt_voltage_filt.set_cutoff_frequency(AP_MOTORS_BATT_VOLT_FILT_HZ);
_batt_voltage_filt.reset(1.0f);
// default throttle ranges (i.e. _throttle_radio_min, _throttle_radio_max)
set_throttle_range(1100, 1900);
};
// output - sends commands to the motors
void AP_MotorsMulticopter::output()
{
// update throttle filter
update_throttle_filter();
// update battery resistance
update_battery_resistance();
// calc filtered battery voltage and lift_max
update_lift_max_from_batt_voltage();
// run spool logic
output_logic();
// calculate thrust
output_armed_stabilizing();
// apply any thrust compensation for the frame
thrust_compensation();
// convert rpy_thrust values to pwm
output_to_motors();
};
// sends minimum values out to the motors
void AP_MotorsMulticopter::output_min()
{
set_desired_spool_state(DESIRED_SHUT_DOWN);
_spool_mode = SHUT_DOWN;
output();
}
// update the throttle input filter
void AP_MotorsMulticopter::update_throttle_filter()
{
if (armed()) {
_throttle_filter.apply(_throttle_in, 1.0f/_loop_rate);
// constrain filtered throttle
if (_throttle_filter.get() < 0.0f) {
_throttle_filter.reset(0.0f);
}
if (_throttle_filter.get() > 1.0f) {
_throttle_filter.reset(1.0f);
}
} else {
_throttle_filter.reset(0.0f);
}
}
// return current_limit as a number from 0 ~ 1 in the range throttle_min to throttle_max
float AP_MotorsMulticopter::get_current_limit_max_throttle()
{
// return maximum if current limiting is disabled
if (_batt_current_max <= 0) {
_throttle_limit = 1.0f;
return 1.0f;
}
// remove throttle limit if disarmed
if (!_flags.armed) {
_throttle_limit = 1.0f;
return 1.0f;
}
// calculate the maximum current to prevent voltage sag below _batt_voltage_min
float batt_current_max = MIN(_batt_current_max, _batt_current + (_batt_voltage-_batt_voltage_min)/_batt_resistance);
float batt_current_ratio = _batt_current/batt_current_max;
float loop_interval = 1.0f/_loop_rate;
_throttle_limit += (loop_interval/(loop_interval+_batt_current_time_constant))*(1.0f - batt_current_ratio);
// throttle limit drops to 20% between hover and full throttle
_throttle_limit = constrain_float(_throttle_limit, 0.2f, 1.0f);
// limit max throttle
return get_throttle_hover() + ((1.0-get_throttle_hover())*_throttle_limit);
}
// apply_thrust_curve_and_volt_scaling - returns throttle in the range 0 ~ 1
float AP_MotorsMulticopter::apply_thrust_curve_and_volt_scaling(float thrust) const
{
float throttle_ratio = thrust;
// apply thrust curve - domain 0.0 to 1.0, range 0.0 to 1.0
if (_thrust_curve_expo > 0.0f){
if(!is_zero(_batt_voltage_filt.get())) {
throttle_ratio = ((_thrust_curve_expo-1.0f) + safe_sqrt((1.0f-_thrust_curve_expo)*(1.0f-_thrust_curve_expo) + 4.0f*_thrust_curve_expo*_lift_max*thrust))/(2.0f*_thrust_curve_expo*_batt_voltage_filt.get());
} else {
throttle_ratio = ((_thrust_curve_expo-1.0f) + safe_sqrt((1.0f-_thrust_curve_expo)*(1.0f-_thrust_curve_expo) + 4.0f*_thrust_curve_expo*_lift_max*thrust))/(2.0f*_thrust_curve_expo);
}
}
return constrain_float(throttle_ratio, 0.0f, 1.0f);
}
// update_lift_max from battery voltage - used for voltage compensation
void AP_MotorsMulticopter::update_lift_max_from_batt_voltage()
{
// sanity check battery_voltage_min is not too small
// if disabled or misconfigured exit immediately
if((_batt_voltage_max <= 0) || (_batt_voltage_min >= _batt_voltage_max) || (_batt_voltage < 0.25f*_batt_voltage_min)) {
_batt_voltage_filt.reset(1.0f);
_lift_max = 1.0f;
return;
}
_batt_voltage_min = MAX(_batt_voltage_min, _batt_voltage_max * 0.6f);
// add current based voltage sag to battery voltage
float batt_voltage = _batt_voltage + (_batt_current-_batt_current_resting) * _batt_resistance;
batt_voltage = constrain_float(batt_voltage, _batt_voltage_min, _batt_voltage_max);
// filter at 0.5 Hz
float batt_voltage_filt = _batt_voltage_filt.apply(batt_voltage/_batt_voltage_max, 1.0f/_loop_rate);
// calculate lift max
_lift_max = batt_voltage_filt*(1-_thrust_curve_expo) + _thrust_curve_expo*batt_voltage_filt*batt_voltage_filt;
}
// update_battery_resistance - calculate battery resistance when throttle is above hover_out
void AP_MotorsMulticopter::update_battery_resistance()
{
// if disarmed reset resting voltage and current
if (!_flags.armed) {
_batt_voltage_resting = _batt_voltage;
_batt_current_resting = _batt_current;
_batt_timer = 0;
} else if (_batt_voltage_resting > _batt_voltage && _batt_current_resting < _batt_current) {
// update battery resistance when throttle is over hover throttle
float batt_resistance = (_batt_voltage_resting-_batt_voltage)/(_batt_current-_batt_current_resting);
if ((_batt_timer < 400) && ((_batt_current_resting*2.0f) < _batt_current)) {
if (get_throttle() >= get_throttle_hover()) {
// filter reaches 90% in 1/4 the test time
_batt_resistance += 0.05f*(batt_resistance - _batt_resistance);
_batt_timer += 1;
} else {
// initialize battery resistance to prevent change in resting voltage estimate
_batt_resistance = batt_resistance;
}
}
// make sure battery resistance value doesn't result in the predicted battery voltage exceeding the resting voltage
if(batt_resistance < _batt_resistance){
_batt_resistance = batt_resistance;
}
}
}
float AP_MotorsMulticopter::get_compensation_gain() const
{
// avoid divide by zero
if (_lift_max <= 0.0f) {
return 1.0f;
}
float ret = 1.0f / _lift_max;
#if AP_MOTORS_DENSITY_COMP == 1
// air density ratio is increasing in density / decreasing in altitude
if (_air_density_ratio > 0.3f && _air_density_ratio < 1.5f) {
ret *= 1.0f / constrain_float(_air_density_ratio,0.5f,1.25f);
}
#endif
return ret;
}
int16_t AP_MotorsMulticopter::calc_thrust_to_pwm(float thrust_in) const
{
thrust_in = constrain_float(thrust_in, 0.0f, 1.0f);
return get_pwm_output_min() + (get_pwm_output_max()-get_pwm_output_min()) * (_spin_min + (_spin_max-_spin_min)*apply_thrust_curve_and_volt_scaling(thrust_in));
}
int16_t AP_MotorsMulticopter::calc_spin_up_to_pwm() const
{
return get_pwm_output_min() + constrain_float(_spin_up_ratio, 0.0f, 1.0f) * _spin_min * (get_pwm_output_max()-get_pwm_output_min());
}
// get minimum or maximum pwm value that can be output to motors
int16_t AP_MotorsMulticopter::get_pwm_output_min() const
{
// return _pwm_min if both PWM_MIN and PWM_MAX parameters are defined and valid
if ((_pwm_min > 0) && (_pwm_max > 0) && (_pwm_max > _pwm_min)) {
return _pwm_min;
}
return _throttle_radio_min;
}
// get maximum pwm value that can be output to motors
int16_t AP_MotorsMulticopter::get_pwm_output_max() const
{
// return _pwm_max if both PWM_MIN and PWM_MAX parameters are defined and valid
if ((_pwm_min > 0) && (_pwm_max > 0) && (_pwm_max > _pwm_min)) {
return _pwm_max;
}
return _throttle_radio_max;
}
// set_throttle_range - sets the minimum throttle that will be sent to the engines when they're not off (i.e. to prevents issues with some motors spinning and some not at very low throttle)
// also sets throttle channel minimum and maximum pwm
void AP_MotorsMulticopter::set_throttle_range(int16_t radio_min, int16_t radio_max)
{
// sanity check
if ((radio_max > radio_min)) {
_throttle_radio_min = radio_min;
_throttle_radio_max = radio_max;
}
}
// update the throttle input filter. should be called at 100hz
void AP_MotorsMulticopter::update_throttle_hover(float dt)
{
if (_throttle_hover_learn != HOVER_LEARN_DISABLED) {
// we have chosen to constrain the hover throttle to be within the range reachable by the third order expo polynomial.
_throttle_hover = constrain_float(_throttle_hover + (dt/(dt+AP_MOTORS_THST_HOVER_TC))*(get_throttle()-_throttle_hover), AP_MOTORS_THST_HOVER_MIN, AP_MOTORS_THST_HOVER_MAX);
}
}
// run spool logic
void AP_MotorsMulticopter::output_logic()
{
// force desired and current spool mode if disarmed or not interlocked
if (!_flags.armed || !_flags.interlock) {
_spool_desired = DESIRED_SHUT_DOWN;
_spool_mode = SHUT_DOWN;
}
switch (_spool_mode) {
case SHUT_DOWN:
// Motors should be stationary.
// Servos set to their trim values or in a test condition.
// set limits flags
limit.roll_pitch = true;
limit.yaw = true;
limit.throttle_lower = true;
limit.throttle_upper = true;
// make sure the motors are spooling in the correct direction
if (_spool_desired != DESIRED_SHUT_DOWN) {
_spool_mode = SPIN_WHEN_ARMED;
break;
}
// set and increment ramp variables
_spin_up_ratio = 0.0f;
_throttle_thrust_max = 0.0f;
break;
case SPIN_WHEN_ARMED: {
// Motors should be stationary or at spin when armed.
// Servos should be moving to correct the current attitude.
// set limits flags
limit.roll_pitch = true;
limit.yaw = true;
limit.throttle_lower = true;
limit.throttle_upper = true;
// set and increment ramp variables
float spool_step = 1.0f/(AP_MOTORS_SPOOL_UP_TIME*_loop_rate);
if (_spool_desired == DESIRED_SHUT_DOWN){
_spin_up_ratio -= spool_step;
// constrain ramp value and update mode
if (_spin_up_ratio <= 0.0f) {
_spin_up_ratio = 0.0f;
_spool_mode = SHUT_DOWN;
}
} else if(_spool_desired == DESIRED_THROTTLE_UNLIMITED) {
_spin_up_ratio += spool_step;
// constrain ramp value and update mode
if (_spin_up_ratio >= 1.0f) {
_spin_up_ratio = 1.0f;
_spool_mode = SPOOL_UP;
}
} else { // _spool_desired == SPIN_WHEN_ARMED
float spin_up_armed_ratio = 0.0f;
if (_spin_min > 0.0f) {
spin_up_armed_ratio = _spin_arm / _spin_min;
}
_spin_up_ratio += constrain_float(spin_up_armed_ratio-_spin_up_ratio, -spool_step, spool_step);
}
_throttle_thrust_max = 0.0f;
break;
}
case SPOOL_UP:
// Maximum throttle should move from minimum to maximum.
// Servos should exhibit normal flight behavior.
// initialize limits flags
limit.roll_pitch = false;
limit.yaw = false;
limit.throttle_lower = false;
limit.throttle_upper = false;
// make sure the motors are spooling in the correct direction
if (_spool_desired != DESIRED_THROTTLE_UNLIMITED ){
_spool_mode = SPOOL_DOWN;
break;
}
// set and increment ramp variables
_spin_up_ratio = 1.0f;
_throttle_thrust_max += 1.0f/(AP_MOTORS_SPOOL_UP_TIME*_loop_rate);
// constrain ramp value and update mode
if (_throttle_thrust_max >= MIN(get_throttle(), get_current_limit_max_throttle())) {
_throttle_thrust_max = get_current_limit_max_throttle();
_spool_mode = THROTTLE_UNLIMITED;
} else if (_throttle_thrust_max < 0.0f) {
_throttle_thrust_max = 0.0f;
}
break;
case THROTTLE_UNLIMITED:
// Throttle should exhibit normal flight behavior.
// Servos should exhibit normal flight behavior.
// initialize limits flags
limit.roll_pitch = false;
limit.yaw = false;
limit.throttle_lower = false;
limit.throttle_upper = false;
// make sure the motors are spooling in the correct direction
if (_spool_desired != DESIRED_THROTTLE_UNLIMITED) {
_spool_mode = SPOOL_DOWN;
break;
}
// set and increment ramp variables
_spin_up_ratio = 1.0f;
_throttle_thrust_max = get_current_limit_max_throttle();
break;
case SPOOL_DOWN:
// Maximum throttle should move from maximum to minimum.
// Servos should exhibit normal flight behavior.
// initialize limits flags
limit.roll_pitch = false;
limit.yaw = false;
limit.throttle_lower = false;
limit.throttle_upper = false;
// make sure the motors are spooling in the correct direction
if (_spool_desired == DESIRED_THROTTLE_UNLIMITED) {
_spool_mode = SPOOL_UP;
break;
}
// set and increment ramp variables
_spin_up_ratio = 1.0f;
_throttle_thrust_max -= 1.0f/(AP_MOTORS_SPOOL_UP_TIME*_loop_rate);
// constrain ramp value and update mode
if (_throttle_thrust_max <= 0.0f){
_throttle_thrust_max = 0.0f;
}
if (_throttle_thrust_max >= get_current_limit_max_throttle()) {
_throttle_thrust_max = get_current_limit_max_throttle();
} else if (is_zero(_throttle_thrust_max)) {
_spool_mode = SPIN_WHEN_ARMED;
}
break;
}
}
// passes throttle directly to all motors for ESC calibration.
// throttle_input is in the range of 0 ~ 1 where 0 will send get_pwm_output_min() and 1 will send get_pwm_output_max()
void AP_MotorsMulticopter::set_throttle_passthrough_for_esc_calibration(float throttle_input)
{
if (armed()) {
uint16_t pwm_out = get_pwm_output_min() + constrain_float(throttle_input, 0.0f, 1.0f) * (get_pwm_output_max() - get_pwm_output_min());
// send the pilot's input directly to each enabled motor
hal.rcout->cork();
for (uint16_t i=0; i < AP_MOTORS_MAX_NUM_MOTORS; i++) {
if (motor_enabled[i]) {
rc_write(i, pwm_out);
}
}
hal.rcout->push();
}
}
// output a thrust to all motors that match a given motor mask. This
// is used to control tiltrotor motors in forward flight. Thrust is in
// the range 0 to 1
void AP_MotorsMulticopter::output_motor_mask(float thrust, uint8_t mask)
{
hal.rcout->cork();
for (uint8_t i=0; i<AP_MOTORS_MAX_NUM_MOTORS; i++) {
if (motor_enabled[i]) {
int16_t motor_out;
if (mask & (1U<<i)) {
motor_out = calc_thrust_to_pwm(thrust);
} else {
motor_out = get_pwm_output_min();
}
rc_write(i, motor_out);
}
}
hal.rcout->push();
}
// save parameters as part of disarming
void AP_MotorsMulticopter::save_params_on_disarm()
{
// save hover throttle
if (_throttle_hover_learn == HOVER_LEARN_AND_SAVE) {
_throttle_hover.save();
}
}
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