// get acceleration limited desired speed
float AR_AttitudeControl::get_desired_speed_accel_limited(float desired_speed, float dt) const
{
// return input value if no recent calls to speed controller
// apply no limiting when ATC_ACCEL_MAX is set to zero
const uint32_t now = AP_HAL::millis();
if ((_speed_last_ms == 0) || ((now - _speed_last_ms) > AR_ATTCONTROL_TIMEOUT_MS) || !is_positive(_throttle_accel_max)) {
return desired_speed;
}
// sanity check dt
dt = constrain_float(dt, 0.0f, 1.0f);
// use previous desired speed as basis for accel limiting
float speed_prev = _desired_speed;
// if no recent calls to speed controller limit based on current speed
if (!speed_control_active()) {
get_forward_speed(speed_prev);
}
// acceleration limit desired speed
float speed_change_max;
if (fabsf(desired_speed) < fabsf(_desired_speed) && is_positive(_throttle_decel_max)) {
speed_change_max = _throttle_decel_max * dt;
} else {
speed_change_max = _throttle_accel_max * dt;
}
return constrain_float(desired_speed, speed_prev - speed_change_max, speed_prev + speed_change_max);
}
// get latest desired speed recorded during call to get_throttle_out_speed. For reporting purposes only
float AR_AttitudeControl::get_desired_speed() const
{
// return zero if no recent calls to speed controller
if (!speed_control_active()) {
return 0.0f;
}
return _desired_speed;
}
// get acceleration limited desired speed
float AR_AttitudeControl::get_desired_speed_accel_limited(float desired_speed, float dt) const
{
// sanity check dt
dt = constrain_float(dt, 0.0f, 1.0f);
// use previous desired speed as basis for accel limiting
float speed_prev = _desired_speed;
// if no recent calls to speed controller limit based on current speed
if (!speed_control_active()) {
get_forward_speed(speed_prev);
}
// acceleration limit desired speed
float speed_change_max;
if (fabsf(desired_speed) < fabsf(_desired_speed) && is_positive(_throttle_decel_max)) {
speed_change_max = _throttle_decel_max * dt;
} else {
speed_change_max = _throttle_accel_max * dt;
}
return constrain_float(desired_speed, speed_prev - speed_change_max, speed_prev + speed_change_max);
}
// return a throttle output from -1 to +1 given a desired speed in m/s (use negative speeds to travel backwards)
// motor_limit should be true if motors have hit their upper or lower limits
// cruise speed should be in m/s, cruise throttle should be a number from -1 to +1
float AR_AttitudeControl::get_throttle_out_speed(float desired_speed, bool motor_limit_low, bool motor_limit_high, float cruise_speed, float cruise_throttle, float dt)
{
// sanity check dt
dt = constrain_float(dt, 0.0f, 1.0f);
// get speed forward
float speed;
if (!get_forward_speed(speed)) {
// we expect caller will not try to control heading using rate control without a valid speed estimate
// on failure to get speed we do not attempt to steer
return 0.0f;
}
// if not called recently, reset input filter and desired speed to actual speed (used for accel limiting)
const uint32_t now = AP_HAL::millis();
if (!speed_control_active()) {
_throttle_speed_pid.reset_filter();
_desired_speed = speed;
}
_speed_last_ms = now;
// acceleration limit desired speed
_desired_speed = get_desired_speed_accel_limited(desired_speed, dt);
// set PID's dt
_throttle_speed_pid.set_dt(dt);
// calculate speed error and pass to PID controller
const float speed_error = desired_speed - speed;
_throttle_speed_pid.set_input_filter_all(speed_error);
// record desired speed for logging purposes only
_throttle_speed_pid.set_desired_rate(desired_speed);
// get feed-forward
const float ff = _throttle_speed_pid.get_ff(desired_speed);
// get p
const float p = _throttle_speed_pid.get_p();
// get i unless moving at low speed or motors have hit a limit
float i = _throttle_speed_pid.get_integrator();
if ((is_negative(speed_error) && !motor_limit_low && !_throttle_limit_low) || (is_positive(speed_error) && !motor_limit_high && !_throttle_limit_high)) {
i = _throttle_speed_pid.get_i();
}
// get d
const float d = _throttle_speed_pid.get_d();
// calculate base throttle (protect against divide by zero)
float throttle_base = 0.0f;
if (is_positive(cruise_speed) && is_positive(cruise_throttle)) {
throttle_base = desired_speed * (cruise_throttle / cruise_speed);
}
// calculate final output
float throttle_out = (ff+p+i+d+throttle_base);
// clear local limit flags used to stop i-term build-up as we stop reversed outputs going to motors
_throttle_limit_low = false;
_throttle_limit_high = false;
// protect against reverse output being sent to the motors unless braking has been enabled
if (!_brake_enable) {
// if both desired speed and actual speed are positive, do not allow negative values
if ((desired_speed >= 0.0f) && (throttle_out <= 0.0f)) {
throttle_out = 0.0f;
_throttle_limit_low = true;
}
if ((desired_speed <= 0.0f) && (throttle_out >= 0.0f)) {
throttle_out = 0.0f;
_throttle_limit_high = true;
}
}
// final output throttle in range -1 to 1
return throttle_out;
}
