mirror of https://github.com/ArduPilot/ardupilot
927 lines
35 KiB
C++
927 lines
35 KiB
C++
/// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
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#include <AP_HAL.h>
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#include <AC_PosControl.h>
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#include <AP_Math.h>
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extern const AP_HAL::HAL& hal;
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const AP_Param::GroupInfo AC_PosControl::var_info[] PROGMEM = {
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// 0 was used for HOVER
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// @Param: _ACC_XY_FILT
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// @DisplayName: XY Acceleration filter cutoff frequency
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// @Description: Lower values will slow the response of the navigation controller and reduce twitchiness
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// @Units: Hz
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// @Range: 0.5 5
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// @Increment: 0.1
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// @User: Advanced
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AP_GROUPINFO("_ACC_XY_FILT", 1, AC_PosControl, _accel_xy_filt_hz, POSCONTROL_ACCEL_FILTER_HZ),
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AP_GROUPEND
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};
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// Default constructor.
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// Note that the Vector/Matrix constructors already implicitly zero
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// their values.
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//
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AC_PosControl::AC_PosControl(const AP_AHRS& ahrs, const AP_InertialNav& inav,
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const AP_Motors& motors, AC_AttitudeControl& attitude_control,
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AC_P& p_pos_z, AC_P& p_vel_z, AC_PID& pid_accel_z,
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AC_P& p_pos_xy, AC_PI_2D& pi_vel_xy) :
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_ahrs(ahrs),
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_inav(inav),
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_motors(motors),
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_attitude_control(attitude_control),
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_p_pos_z(p_pos_z),
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_p_vel_z(p_vel_z),
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_pid_accel_z(pid_accel_z),
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_p_pos_xy(p_pos_xy),
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_pi_vel_xy(pi_vel_xy),
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_dt(POSCONTROL_DT_10HZ),
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_dt_xy(POSCONTROL_DT_50HZ),
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_last_update_xy_ms(0),
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_last_update_z_ms(0),
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_throttle_hover(POSCONTROL_THROTTLE_HOVER),
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_speed_down_cms(POSCONTROL_SPEED_DOWN),
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_speed_up_cms(POSCONTROL_SPEED_UP),
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_speed_cms(POSCONTROL_SPEED),
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_accel_z_cms(POSCONTROL_ACCEL_Z),
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_accel_cms(POSCONTROL_ACCEL_XY),
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_leash(POSCONTROL_LEASH_LENGTH_MIN),
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_leash_down_z(POSCONTROL_LEASH_LENGTH_MIN),
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_leash_up_z(POSCONTROL_LEASH_LENGTH_MIN),
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_roll_target(0.0f),
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_pitch_target(0.0f),
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_alt_max(0.0f),
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_distance_to_target(0.0f),
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_accel_target_jerk_limited(0.0f,0.0f),
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_accel_target_filter(POSCONTROL_ACCEL_FILTER_HZ)
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{
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AP_Param::setup_object_defaults(this, var_info);
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// initialise flags
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_flags.recalc_leash_xy = true;
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_flags.recalc_leash_z = true;
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_flags.reset_desired_vel_to_pos = true;
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_flags.reset_rate_to_accel_xy = true;
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_flags.reset_accel_to_lean_xy = true;
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_flags.reset_rate_to_accel_z = true;
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_flags.reset_accel_to_throttle = true;
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}
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///
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/// z-axis position controller
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///
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/// set_dt - sets time delta in seconds for all controllers (i.e. 100hz = 0.01, 400hz = 0.0025)
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void AC_PosControl::set_dt(float delta_sec)
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{
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_dt = delta_sec;
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// update rate controller's dt
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_pid_accel_z.set_dt(_dt);
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// update rate z-axis velocity error and accel error filters
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_vel_error_filter.set_cutoff_frequency(POSCONTROL_VEL_ERROR_CUTOFF_FREQ);
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}
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/// set_dt_xy - sets time delta in seconds for horizontal controller (i.e. 50hz = 0.02)
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void AC_PosControl::set_dt_xy(float dt_xy)
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{
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_dt_xy = dt_xy;
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_pi_vel_xy.set_dt(dt_xy);
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}
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/// set_speed_z - sets maximum climb and descent rates
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/// To-Do: call this in the main code as part of flight mode initialisation
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/// calc_leash_length_z should be called afterwards
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/// speed_down should be a negative number
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void AC_PosControl::set_speed_z(float speed_down, float speed_up)
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{
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// ensure speed_down is always negative
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speed_down = -fabsf(speed_down);
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if ((fabsf(_speed_down_cms-speed_down) > 1.0f) || (fabsf(_speed_up_cms-speed_up) > 1.0f)) {
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_speed_down_cms = speed_down;
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_speed_up_cms = speed_up;
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_flags.recalc_leash_z = true;
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calc_leash_length_z();
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}
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}
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/// set_accel_z - set vertical acceleration in cm/s/s
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void AC_PosControl::set_accel_z(float accel_cmss)
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{
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if (fabsf(_accel_z_cms-accel_cmss) > 1.0f) {
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_accel_z_cms = accel_cmss;
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_flags.recalc_leash_z = true;
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calc_leash_length_z();
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}
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}
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/// set_alt_target_with_slew - adjusts target towards a final altitude target
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/// should be called continuously (with dt set to be the expected time between calls)
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/// actual position target will be moved no faster than the speed_down and speed_up
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/// target will also be stopped if the motors hit their limits or leash length is exceeded
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void AC_PosControl::set_alt_target_with_slew(float alt_cm, float dt)
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{
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float alt_change = alt_cm-_pos_target.z;
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_vel_desired.z = 0.0f;
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// adjust desired alt if motors have not hit their limits
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if ((alt_change<0 && !_motors.limit.throttle_lower) || (alt_change>0 && !_motors.limit.throttle_upper)) {
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_pos_target.z += constrain_float(alt_change, _speed_down_cms*dt, _speed_up_cms*dt);
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}
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// do not let target get too far from current altitude
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float curr_alt = _inav.get_altitude();
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_pos_target.z = constrain_float(_pos_target.z,curr_alt-_leash_down_z,curr_alt+_leash_up_z);
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}
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/// set_alt_target_from_climb_rate - adjusts target up or down using a climb rate in cm/s
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/// should be called continuously (with dt set to be the expected time between calls)
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/// actual position target will be moved no faster than the speed_down and speed_up
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/// target will also be stopped if the motors hit their limits or leash length is exceeded
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void AC_PosControl::set_alt_target_from_climb_rate(float climb_rate_cms, float dt, bool force_descend)
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{
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// jerk_z is calculated to reach full acceleration in 1000ms.
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float jerk_z = _accel_z_cms * POSCONTROL_JERK_RATIO;
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float accel_z_max = min(_accel_z_cms, safe_sqrt(2.0f*fabsf(_vel_desired.z - climb_rate_cms)*jerk_z));
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_accel_last_z_cms += jerk_z * dt;
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_accel_last_z_cms = min(accel_z_max, _accel_last_z_cms);
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float vel_change_limit = _accel_last_z_cms * dt;
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_vel_desired.z = constrain_float(climb_rate_cms, _vel_desired.z-vel_change_limit, _vel_desired.z+vel_change_limit);
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// adjust desired alt if motors have not hit their limits
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// To-Do: add check of _limit.pos_down?
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if ((_vel_desired.z<0 && (!_motors.limit.throttle_lower || force_descend)) || (_vel_desired.z>0 && !_motors.limit.throttle_upper && !_limit.pos_up)) {
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_pos_target.z += _vel_desired.z * dt;
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}
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// do not let target alt get above limit
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if (_alt_max > 0 && _pos_target.z > _alt_max) {
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_pos_target.z = _alt_max;
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_limit.pos_up = true;
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// decelerate feed forward to zero
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_vel_desired.z = constrain_float(0.0f, _vel_desired.z-vel_change_limit, _vel_desired.z+vel_change_limit);
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}
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}
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/// add_takeoff_climb_rate - adjusts alt target up or down using a climb rate in cm/s
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/// should be called continuously (with dt set to be the expected time between calls)
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/// almost no checks are performed on the input
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void AC_PosControl::add_takeoff_climb_rate(float climb_rate_cms, float dt)
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{
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_pos_target.z += climb_rate_cms * dt;
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}
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/// relax_alt_hold_controllers - set all desired and targets to measured
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void AC_PosControl::relax_alt_hold_controllers(float throttle_setting)
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{
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_pos_target.z = _inav.get_altitude();
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_vel_desired.z = 0.0f;
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_vel_target.z= _inav.get_velocity_z();
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_vel_last.z = _inav.get_velocity_z();
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_accel_feedforward.z = 0.0f;
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_accel_last_z_cms = 0.0f;
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_accel_target.z = -(_ahrs.get_accel_ef_blended().z + GRAVITY_MSS) * 100.0f;
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_flags.reset_accel_to_throttle = true;
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_pid_accel_z.set_integrator(throttle_setting);
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}
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// get_alt_error - returns altitude error in cm
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float AC_PosControl::get_alt_error() const
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{
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return (_pos_target.z - _inav.get_altitude());
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}
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/// set_target_to_stopping_point_z - returns reasonable stopping altitude in cm above home
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void AC_PosControl::set_target_to_stopping_point_z()
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{
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// check if z leash needs to be recalculated
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calc_leash_length_z();
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get_stopping_point_z(_pos_target);
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}
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/// get_stopping_point_z - calculates stopping point based on current position, velocity, vehicle acceleration
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void AC_PosControl::get_stopping_point_z(Vector3f& stopping_point) const
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{
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const float curr_pos_z = _inav.get_altitude();
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float curr_vel_z = _inav.get_velocity_z();
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float linear_distance; // half the distance we swap between linear and sqrt and the distance we offset sqrt
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float linear_velocity; // the velocity we swap between linear and sqrt
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// if position controller is active add current velocity error to avoid sudden jump in acceleration
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if (is_active_z()) {
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curr_vel_z += _vel_error.z;
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curr_vel_z -= _vel_desired.z;
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}
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// calculate the velocity at which we switch from calculating the stopping point using a linear function to a sqrt function
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linear_velocity = _accel_z_cms/_p_pos_z.kP();
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if (fabsf(curr_vel_z) < linear_velocity) {
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// if our current velocity is below the cross-over point we use a linear function
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stopping_point.z = curr_pos_z + curr_vel_z/_p_pos_z.kP();
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} else {
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linear_distance = _accel_z_cms/(2.0f*_p_pos_z.kP()*_p_pos_z.kP());
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if (curr_vel_z > 0){
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stopping_point.z = curr_pos_z + (linear_distance + curr_vel_z*curr_vel_z/(2.0f*_accel_z_cms));
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} else {
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stopping_point.z = curr_pos_z - (linear_distance + curr_vel_z*curr_vel_z/(2.0f*_accel_z_cms));
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}
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}
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stopping_point.z = constrain_float(stopping_point.z, curr_pos_z - POSCONTROL_STOPPING_DIST_Z_MAX, curr_pos_z + POSCONTROL_STOPPING_DIST_Z_MAX);
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}
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/// init_takeoff - initialises target altitude if we are taking off
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void AC_PosControl::init_takeoff()
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{
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const Vector3f& curr_pos = _inav.get_position();
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_pos_target.z = curr_pos.z + POSCONTROL_TAKEOFF_JUMP_CM;
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// freeze feedforward to avoid jump
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freeze_ff_z();
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// shift difference between last motor out and hover throttle into accelerometer I
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_pid_accel_z.set_integrator(_motors.get_throttle()-_throttle_hover);
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}
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// is_active_z - returns true if the z-axis position controller has been run very recently
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bool AC_PosControl::is_active_z() const
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{
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return ((hal.scheduler->millis() - _last_update_z_ms) <= POSCONTROL_ACTIVE_TIMEOUT_MS);
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}
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/// update_z_controller - fly to altitude in cm above home
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void AC_PosControl::update_z_controller()
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{
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// check time since last cast
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uint32_t now = hal.scheduler->millis();
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if (now - _last_update_z_ms > POSCONTROL_ACTIVE_TIMEOUT_MS) {
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_flags.reset_rate_to_accel_z = true;
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_flags.reset_accel_to_throttle = true;
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}
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_last_update_z_ms = now;
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// check if leash lengths need to be recalculated
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calc_leash_length_z();
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// call position controller
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pos_to_rate_z();
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}
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/// calc_leash_length - calculates the vertical leash lengths from maximum speed, acceleration
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/// called by pos_to_rate_z if z-axis speed or accelerations are changed
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void AC_PosControl::calc_leash_length_z()
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{
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if (_flags.recalc_leash_z) {
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_leash_up_z = calc_leash_length(_speed_up_cms, _accel_z_cms, _p_pos_z.kP());
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_leash_down_z = calc_leash_length(-_speed_down_cms, _accel_z_cms, _p_pos_z.kP());
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_flags.recalc_leash_z = false;
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}
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}
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// pos_to_rate_z - position to rate controller for Z axis
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// calculates desired rate in earth-frame z axis and passes to rate controller
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// vel_up_max, vel_down_max should have already been set before calling this method
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void AC_PosControl::pos_to_rate_z()
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{
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float curr_alt = _inav.get_altitude();
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// clear position limit flags
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_limit.pos_up = false;
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_limit.pos_down = false;
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// calculate altitude error
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_pos_error.z = _pos_target.z - curr_alt;
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// do not let target altitude get too far from current altitude
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if (_pos_error.z > _leash_up_z) {
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_pos_target.z = curr_alt + _leash_up_z;
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_pos_error.z = _leash_up_z;
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_limit.pos_up = true;
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}
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if (_pos_error.z < -_leash_down_z) {
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_pos_target.z = curr_alt - _leash_down_z;
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_pos_error.z = -_leash_down_z;
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_limit.pos_down = true;
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}
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// calculate _vel_target.z using from _pos_error.z using sqrt controller
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_vel_target.z = AC_AttitudeControl::sqrt_controller(_pos_error.z, _p_pos_z.kP(), _accel_z_cms);
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// add feed forward component
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_vel_target.z += _vel_desired.z;
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// call rate based throttle controller which will update accel based throttle controller targets
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rate_to_accel_z();
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}
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// rate_to_accel_z - calculates desired accel required to achieve the velocity target
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// calculates desired acceleration and calls accel throttle controller
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void AC_PosControl::rate_to_accel_z()
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{
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const Vector3f& curr_vel = _inav.get_velocity();
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float p; // used to capture pid values for logging
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// check speed limits
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// To-Do: check these speed limits here or in the pos->rate controller
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_limit.vel_up = false;
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_limit.vel_down = false;
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if (_vel_target.z < _speed_down_cms) {
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_vel_target.z = _speed_down_cms;
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_limit.vel_down = true;
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}
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if (_vel_target.z > _speed_up_cms) {
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_vel_target.z = _speed_up_cms;
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_limit.vel_up = true;
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}
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// reset last velocity target to current target
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if (_flags.reset_rate_to_accel_z) {
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_vel_last.z = _vel_target.z;
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}
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// feed forward desired acceleration calculation
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if (_dt > 0.0f) {
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if (!_flags.freeze_ff_z) {
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_accel_feedforward.z = (_vel_target.z - _vel_last.z)/_dt;
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} else {
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// stop the feed forward being calculated during a known discontinuity
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_flags.freeze_ff_z = false;
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}
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} else {
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_accel_feedforward.z = 0.0f;
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}
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// store this iteration's velocities for the next iteration
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_vel_last.z = _vel_target.z;
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// reset velocity error and filter if this controller has just been engaged
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if (_flags.reset_rate_to_accel_z) {
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// Reset Filter
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_vel_error.z = 0;
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_vel_error_filter.reset(0);
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_flags.reset_rate_to_accel_z = false;
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} else {
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// calculate rate error and filter with cut off frequency of 2 Hz
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_vel_error.z = _vel_error_filter.apply(_vel_target.z - curr_vel.z, _dt);
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}
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// calculate p
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p = _p_vel_z.kP() * _vel_error.z;
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// consolidate and constrain target acceleration
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_accel_target.z = _accel_feedforward.z + p;
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// set target for accel based throttle controller
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accel_to_throttle(_accel_target.z);
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}
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// accel_to_throttle - alt hold's acceleration controller
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// calculates a desired throttle which is sent directly to the motors
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void AC_PosControl::accel_to_throttle(float accel_target_z)
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{
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float z_accel_meas; // actual acceleration
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float p,i,d; // used to capture pid values for logging
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// Calculate Earth Frame Z acceleration
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z_accel_meas = -(_ahrs.get_accel_ef_blended().z + GRAVITY_MSS) * 100.0f;
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// reset target altitude if this controller has just been engaged
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if (_flags.reset_accel_to_throttle) {
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// Reset Filter
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_accel_error.z = 0;
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_flags.reset_accel_to_throttle = false;
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} else {
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// calculate accel error
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_accel_error.z = accel_target_z - z_accel_meas;
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}
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// set input to PID
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_pid_accel_z.set_input_filter_d(_accel_error.z);
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// separately calculate p, i, d values for logging
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p = _pid_accel_z.get_p();
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// get i term
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i = _pid_accel_z.get_integrator();
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// update i term as long as we haven't breached the limits or the I term will certainly reduce
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// To-Do: should this be replaced with limits check from attitude_controller?
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if ((!_motors.limit.throttle_lower && !_motors.limit.throttle_upper) || (i>0&&_accel_error.z<0) || (i<0&&_accel_error.z>0)) {
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i = _pid_accel_z.get_i();
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}
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// get d term
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d = _pid_accel_z.get_d();
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float thr_out = p+i+d+_throttle_hover;
|
|
|
|
// send throttle to attitude controller with angle boost
|
|
_attitude_control.set_throttle_out(thr_out, true, POSCONTROL_THROTTLE_CUTOFF_FREQ);
|
|
}
|
|
|
|
///
|
|
/// position controller
|
|
///
|
|
|
|
/// set_accel_xy - set horizontal acceleration in cm/s/s
|
|
/// calc_leash_length_xy should be called afterwards
|
|
void AC_PosControl::set_accel_xy(float accel_cmss)
|
|
{
|
|
if (fabsf(_accel_cms-accel_cmss) > 1.0f) {
|
|
_accel_cms = accel_cmss;
|
|
_flags.recalc_leash_xy = true;
|
|
calc_leash_length_xy();
|
|
}
|
|
}
|
|
|
|
/// set_speed_xy - set horizontal speed maximum in cm/s
|
|
/// calc_leash_length_xy should be called afterwards
|
|
void AC_PosControl::set_speed_xy(float speed_cms)
|
|
{
|
|
if (fabsf(_speed_cms-speed_cms) > 1.0f) {
|
|
_speed_cms = speed_cms;
|
|
_flags.recalc_leash_xy = true;
|
|
calc_leash_length_xy();
|
|
}
|
|
}
|
|
|
|
/// set_pos_target in cm from home
|
|
void AC_PosControl::set_pos_target(const Vector3f& position)
|
|
{
|
|
_pos_target = position;
|
|
|
|
_vel_desired.z = 0.0f;
|
|
// initialise roll and pitch to current roll and pitch. This avoids a twitch between when the target is set and the pos controller is first run
|
|
// To-Do: this initialisation of roll and pitch targets needs to go somewhere between when pos-control is initialised and when it completes it's first cycle
|
|
//_roll_target = constrain_int32(_ahrs.roll_sensor,-_attitude_control.lean_angle_max(),_attitude_control.lean_angle_max());
|
|
//_pitch_target = constrain_int32(_ahrs.pitch_sensor,-_attitude_control.lean_angle_max(),_attitude_control.lean_angle_max());
|
|
}
|
|
|
|
/// set_xy_target in cm from home
|
|
void AC_PosControl::set_xy_target(float x, float y)
|
|
{
|
|
_pos_target.x = x;
|
|
_pos_target.y = y;
|
|
}
|
|
|
|
/// set_target_to_stopping_point_xy - sets horizontal target to reasonable stopping position in cm from home
|
|
void AC_PosControl::set_target_to_stopping_point_xy()
|
|
{
|
|
// check if xy leash needs to be recalculated
|
|
calc_leash_length_xy();
|
|
|
|
get_stopping_point_xy(_pos_target);
|
|
}
|
|
|
|
/// get_stopping_point_xy - calculates stopping point based on current position, velocity, vehicle acceleration
|
|
/// distance_max allows limiting distance to stopping point
|
|
/// results placed in stopping_position vector
|
|
/// set_accel_xy() should be called before this method to set vehicle acceleration
|
|
/// set_leash_length() should have been called before this method
|
|
void AC_PosControl::get_stopping_point_xy(Vector3f &stopping_point) const
|
|
{
|
|
const Vector3f curr_pos = _inav.get_position();
|
|
Vector3f curr_vel = _inav.get_velocity();
|
|
float linear_distance; // the distance at which we swap from a linear to sqrt response
|
|
float linear_velocity; // the velocity above which we swap from a linear to sqrt response
|
|
float stopping_dist; // the distance within the vehicle can stop
|
|
float kP = _p_pos_xy.kP();
|
|
|
|
// add velocity error to current velocity
|
|
if (is_active_xy()) {
|
|
curr_vel.x += _vel_error.x;
|
|
curr_vel.y += _vel_error.y;
|
|
}
|
|
|
|
// calculate current velocity
|
|
float vel_total = pythagorous2(curr_vel.x, curr_vel.y);
|
|
|
|
// avoid divide by zero by using current position if the velocity is below 10cm/s, kP is very low or acceleration is zero
|
|
if (kP <= 0.0f || _accel_cms <= 0.0f || is_zero(vel_total)) {
|
|
stopping_point.x = curr_pos.x;
|
|
stopping_point.y = curr_pos.y;
|
|
return;
|
|
}
|
|
|
|
// calculate point at which velocity switches from linear to sqrt
|
|
linear_velocity = _accel_cms/kP;
|
|
|
|
// calculate distance within which we can stop
|
|
if (vel_total < linear_velocity) {
|
|
stopping_dist = vel_total/kP;
|
|
} else {
|
|
linear_distance = _accel_cms/(2.0f*kP*kP);
|
|
stopping_dist = linear_distance + (vel_total*vel_total)/(2.0f*_accel_cms);
|
|
}
|
|
|
|
// constrain stopping distance
|
|
stopping_dist = constrain_float(stopping_dist, 0, _leash);
|
|
|
|
// convert the stopping distance into a stopping point using velocity vector
|
|
stopping_point.x = curr_pos.x + (stopping_dist * curr_vel.x / vel_total);
|
|
stopping_point.y = curr_pos.y + (stopping_dist * curr_vel.y / vel_total);
|
|
}
|
|
|
|
/// get_distance_to_target - get horizontal distance to loiter target in cm
|
|
float AC_PosControl::get_distance_to_target() const
|
|
{
|
|
return _distance_to_target;
|
|
}
|
|
|
|
// is_active_xy - returns true if the xy position controller has been run very recently
|
|
bool AC_PosControl::is_active_xy() const
|
|
{
|
|
return ((hal.scheduler->millis() - _last_update_xy_ms) <= POSCONTROL_ACTIVE_TIMEOUT_MS);
|
|
}
|
|
|
|
/// init_xy_controller - initialise the xy controller
|
|
/// sets target roll angle, pitch angle and I terms based on vehicle current lean angles
|
|
/// should be called once whenever significant changes to the position target are made
|
|
/// this does not update the xy target
|
|
void AC_PosControl::init_xy_controller(bool reset_I)
|
|
{
|
|
// set roll, pitch lean angle targets to current attitude
|
|
_roll_target = _ahrs.roll_sensor;
|
|
_pitch_target = _ahrs.pitch_sensor;
|
|
|
|
// initialise I terms from lean angles
|
|
if (reset_I) {
|
|
// reset last velocity if this controller has just been engaged or dt is zero
|
|
lean_angles_to_accel(_accel_target.x, _accel_target.y);
|
|
_pi_vel_xy.set_integrator(_accel_target);
|
|
}
|
|
|
|
// flag reset required in rate to accel step
|
|
_flags.reset_desired_vel_to_pos = true;
|
|
_flags.reset_rate_to_accel_xy = true;
|
|
_flags.reset_accel_to_lean_xy = true;
|
|
}
|
|
|
|
/// update_xy_controller - run the horizontal position controller - should be called at 100hz or higher
|
|
void AC_PosControl::update_xy_controller(xy_mode mode, float ekfNavVelGainScaler)
|
|
{
|
|
// compute dt
|
|
uint32_t now = hal.scheduler->millis();
|
|
float dt = (now - _last_update_xy_ms) / 1000.0f;
|
|
_last_update_xy_ms = now;
|
|
|
|
// sanity check dt - expect to be called faster than ~5hz
|
|
if (dt > POSCONTROL_ACTIVE_TIMEOUT_MS*1.0e-3f) {
|
|
dt = 0.0f;
|
|
}
|
|
|
|
// check if xy leash needs to be recalculated
|
|
calc_leash_length_xy();
|
|
|
|
// translate any adjustments from pilot to loiter target
|
|
desired_vel_to_pos(dt);
|
|
|
|
// run position controller's position error to desired velocity step
|
|
pos_to_rate_xy(mode, dt, ekfNavVelGainScaler);
|
|
|
|
// run position controller's velocity to acceleration step
|
|
rate_to_accel_xy(dt, ekfNavVelGainScaler);
|
|
|
|
// run position controller's acceleration to lean angle step
|
|
accel_to_lean_angles(dt, ekfNavVelGainScaler);
|
|
}
|
|
|
|
float AC_PosControl::time_since_last_xy_update() const
|
|
{
|
|
uint32_t now = hal.scheduler->millis();
|
|
return (now - _last_update_xy_ms)*0.001f;
|
|
}
|
|
|
|
/// init_vel_controller_xyz - initialise the velocity controller - should be called once before the caller attempts to use the controller
|
|
void AC_PosControl::init_vel_controller_xyz()
|
|
{
|
|
// set roll, pitch lean angle targets to current attitude
|
|
_roll_target = _ahrs.roll_sensor;
|
|
_pitch_target = _ahrs.pitch_sensor;
|
|
|
|
// reset last velocity if this controller has just been engaged or dt is zero
|
|
lean_angles_to_accel(_accel_target.x, _accel_target.y);
|
|
_pi_vel_xy.set_integrator(_accel_target);
|
|
|
|
// flag reset required in rate to accel step
|
|
_flags.reset_desired_vel_to_pos = true;
|
|
_flags.reset_rate_to_accel_xy = true;
|
|
_flags.reset_accel_to_lean_xy = true;
|
|
|
|
// set target position in xy axis
|
|
const Vector3f& curr_pos = _inav.get_position();
|
|
set_xy_target(curr_pos.x, curr_pos.y);
|
|
|
|
// move current vehicle velocity into feed forward velocity
|
|
const Vector3f& curr_vel = _inav.get_velocity();
|
|
set_desired_velocity_xy(curr_vel.x, curr_vel.y);
|
|
}
|
|
|
|
/// update_velocity_controller_xyz - run the velocity controller - should be called at 100hz or higher
|
|
/// velocity targets should we set using set_desired_velocity_xyz() method
|
|
/// callers should use get_roll() and get_pitch() methods and sent to the attitude controller
|
|
/// throttle targets will be sent directly to the motors
|
|
void AC_PosControl::update_vel_controller_xyz(float ekfNavVelGainScaler)
|
|
{
|
|
// capture time since last iteration
|
|
uint32_t now = hal.scheduler->millis();
|
|
float dt = (now - _last_update_xy_ms) / 1000.0f;
|
|
|
|
// sanity check dt - expect to be called faster than ~5hz
|
|
if (dt >= POSCONTROL_ACTIVE_TIMEOUT_MS*1.0e-3f) {
|
|
dt = 0.0f;
|
|
}
|
|
|
|
// check if xy leash needs to be recalculated
|
|
calc_leash_length_xy();
|
|
|
|
// apply desired velocity request to position target
|
|
desired_vel_to_pos(dt);
|
|
|
|
// run position controller's position error to desired velocity step
|
|
pos_to_rate_xy(XY_MODE_POS_LIMITED_AND_VEL_FF, dt, ekfNavVelGainScaler);
|
|
|
|
// run velocity to acceleration step
|
|
rate_to_accel_xy(dt, ekfNavVelGainScaler);
|
|
|
|
// run acceleration to lean angle step
|
|
accel_to_lean_angles(dt, ekfNavVelGainScaler);
|
|
|
|
// update altitude target
|
|
set_alt_target_from_climb_rate(_vel_desired.z, dt);
|
|
|
|
// run z-axis position controller
|
|
update_z_controller();
|
|
|
|
// record update time
|
|
_last_update_xy_ms = now;
|
|
}
|
|
|
|
///
|
|
/// private methods
|
|
///
|
|
|
|
/// calc_leash_length - calculates the horizontal leash length given a maximum speed, acceleration
|
|
/// should be called whenever the speed, acceleration or position kP is modified
|
|
void AC_PosControl::calc_leash_length_xy()
|
|
{
|
|
if (_flags.recalc_leash_xy) {
|
|
_leash = calc_leash_length(_speed_cms, _accel_cms, _p_pos_xy.kP());
|
|
_flags.recalc_leash_xy = false;
|
|
}
|
|
}
|
|
|
|
/// desired_vel_to_pos - move position target using desired velocities
|
|
void AC_PosControl::desired_vel_to_pos(float nav_dt)
|
|
{
|
|
// range check nav_dt
|
|
if( nav_dt < 0 ) {
|
|
return;
|
|
}
|
|
|
|
// update target position
|
|
if (_flags.reset_desired_vel_to_pos) {
|
|
_flags.reset_desired_vel_to_pos = false;
|
|
} else {
|
|
_pos_target.x += _vel_desired.x * nav_dt;
|
|
_pos_target.y += _vel_desired.y * nav_dt;
|
|
}
|
|
}
|
|
|
|
/// pos_to_rate_xy - horizontal position error to velocity controller
|
|
/// converts position (_pos_target) to target velocity (_vel_target)
|
|
/// when use_desired_rate is set to true:
|
|
/// desired velocity (_vel_desired) is combined into final target velocity and
|
|
/// velocity due to position error is reduce to a maximum of 1m/s
|
|
void AC_PosControl::pos_to_rate_xy(xy_mode mode, float dt, float ekfNavVelGainScaler)
|
|
{
|
|
Vector3f curr_pos = _inav.get_position();
|
|
float linear_distance; // the distance we swap between linear and sqrt velocity response
|
|
float kP = ekfNavVelGainScaler * _p_pos_xy.kP(); // scale gains to compensate for noisy optical flow measurement in the EKF
|
|
|
|
// avoid divide by zero
|
|
if (kP <= 0.0f) {
|
|
_vel_target.x = 0.0f;
|
|
_vel_target.y = 0.0f;
|
|
}else{
|
|
// calculate distance error
|
|
_pos_error.x = _pos_target.x - curr_pos.x;
|
|
_pos_error.y = _pos_target.y - curr_pos.y;
|
|
|
|
// constrain target position to within reasonable distance of current location
|
|
_distance_to_target = pythagorous2(_pos_error.x, _pos_error.y);
|
|
if (_distance_to_target > _leash && _distance_to_target > 0.0f) {
|
|
_pos_target.x = curr_pos.x + _leash * _pos_error.x/_distance_to_target;
|
|
_pos_target.y = curr_pos.y + _leash * _pos_error.y/_distance_to_target;
|
|
// re-calculate distance error
|
|
_pos_error.x = _pos_target.x - curr_pos.x;
|
|
_pos_error.y = _pos_target.y - curr_pos.y;
|
|
_distance_to_target = _leash;
|
|
}
|
|
|
|
// calculate the distance at which we swap between linear and sqrt velocity response
|
|
linear_distance = _accel_cms/(2.0f*kP*kP);
|
|
|
|
if (_distance_to_target > 2.0f*linear_distance) {
|
|
// velocity response grows with the square root of the distance
|
|
float vel_sqrt = safe_sqrt(2.0f*_accel_cms*(_distance_to_target-linear_distance));
|
|
_vel_target.x = vel_sqrt * _pos_error.x/_distance_to_target;
|
|
_vel_target.y = vel_sqrt * _pos_error.y/_distance_to_target;
|
|
}else{
|
|
// velocity response grows linearly with the distance
|
|
_vel_target.x = _p_pos_xy.kP() * _pos_error.x;
|
|
_vel_target.y = _p_pos_xy.kP() * _pos_error.y;
|
|
}
|
|
|
|
if (mode == XY_MODE_POS_LIMITED_AND_VEL_FF) {
|
|
// this mode is for loiter - rate-limiting the position correction
|
|
// allows the pilot to always override the position correction in
|
|
// the event of a disturbance
|
|
|
|
// scale velocity within limit
|
|
float vel_total = pythagorous2(_vel_target.x, _vel_target.y);
|
|
if (vel_total > POSCONTROL_VEL_XY_MAX_FROM_POS_ERR) {
|
|
_vel_target.x = POSCONTROL_VEL_XY_MAX_FROM_POS_ERR * _vel_target.x/vel_total;
|
|
_vel_target.y = POSCONTROL_VEL_XY_MAX_FROM_POS_ERR * _vel_target.y/vel_total;
|
|
}
|
|
|
|
// add velocity feed-forward
|
|
_vel_target.x += _vel_desired.x;
|
|
_vel_target.y += _vel_desired.y;
|
|
} else {
|
|
if (mode == XY_MODE_POS_AND_VEL_FF) {
|
|
// add velocity feed-forward
|
|
_vel_target.x += _vel_desired.x;
|
|
_vel_target.y += _vel_desired.y;
|
|
}
|
|
|
|
// scale velocity within speed limit
|
|
float vel_total = pythagorous2(_vel_target.x, _vel_target.y);
|
|
if (vel_total > _speed_cms) {
|
|
_vel_target.x = _speed_cms * _vel_target.x/vel_total;
|
|
_vel_target.y = _speed_cms * _vel_target.y/vel_total;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
/// rate_to_accel_xy - horizontal desired rate to desired acceleration
|
|
/// converts desired velocities in lat/lon directions to accelerations in lat/lon frame
|
|
void AC_PosControl::rate_to_accel_xy(float dt, float ekfNavVelGainScaler)
|
|
{
|
|
const Vector3f &vel_curr = _inav.get_velocity(); // current velocity in cm/s
|
|
float accel_total; // total acceleration in cm/s/s
|
|
Vector2f vel_xy_p, vel_xy_i;
|
|
|
|
// reset last velocity target to current target
|
|
if (_flags.reset_rate_to_accel_xy) {
|
|
_vel_last.x = _vel_target.x;
|
|
_vel_last.y = _vel_target.y;
|
|
_flags.reset_rate_to_accel_xy = false;
|
|
}
|
|
|
|
// feed forward desired acceleration calculation
|
|
if (dt > 0.0f) {
|
|
if (!_flags.freeze_ff_xy) {
|
|
_accel_feedforward.x = (_vel_target.x - _vel_last.x)/dt;
|
|
_accel_feedforward.y = (_vel_target.y - _vel_last.y)/dt;
|
|
} else {
|
|
// stop the feed forward being calculated during a known discontinuity
|
|
_flags.freeze_ff_xy = false;
|
|
}
|
|
} else {
|
|
_accel_feedforward.x = 0.0f;
|
|
_accel_feedforward.y = 0.0f;
|
|
}
|
|
|
|
// store this iteration's velocities for the next iteration
|
|
_vel_last.x = _vel_target.x;
|
|
_vel_last.y = _vel_target.y;
|
|
|
|
// calculate velocity error
|
|
_vel_error.x = _vel_target.x - vel_curr.x;
|
|
_vel_error.y = _vel_target.y - vel_curr.y;
|
|
|
|
// call pi controller
|
|
_pi_vel_xy.set_input(_vel_error);
|
|
|
|
// get p
|
|
vel_xy_p = _pi_vel_xy.get_p();
|
|
|
|
// update i term if we have not hit the accel or throttle limits OR the i term will reduce
|
|
if ((!_limit.accel_xy && !_motors.limit.throttle_upper)) {
|
|
vel_xy_i = _pi_vel_xy.get_i();
|
|
} else {
|
|
vel_xy_i = _pi_vel_xy.get_i_shrink();
|
|
}
|
|
|
|
// combine feed forward accel with PID output from velocity error and scale PID output to compensate for optical flow measurement induced EKF noise
|
|
_accel_target.x = _accel_feedforward.x + (vel_xy_p.x + vel_xy_i.x) * ekfNavVelGainScaler;
|
|
_accel_target.y = _accel_feedforward.y + (vel_xy_p.y + vel_xy_i.y) * ekfNavVelGainScaler;
|
|
|
|
// scale desired acceleration if it's beyond acceptable limit
|
|
// To-Do: move this check down to the accel_to_lean_angle method?
|
|
accel_total = pythagorous2(_accel_target.x, _accel_target.y);
|
|
if (accel_total > POSCONTROL_ACCEL_XY_MAX && accel_total > 0.0f) {
|
|
_accel_target.x = POSCONTROL_ACCEL_XY_MAX * _accel_target.x/accel_total;
|
|
_accel_target.y = POSCONTROL_ACCEL_XY_MAX * _accel_target.y/accel_total;
|
|
_limit.accel_xy = true; // unused
|
|
} else {
|
|
// reset accel limit flag
|
|
_limit.accel_xy = false;
|
|
}
|
|
}
|
|
|
|
/// accel_to_lean_angles - horizontal desired acceleration to lean angles
|
|
/// converts desired accelerations provided in lat/lon frame to roll/pitch angles
|
|
void AC_PosControl::accel_to_lean_angles(float dt, float ekfNavVelGainScaler)
|
|
{
|
|
float accel_right, accel_forward;
|
|
float lean_angle_max = _attitude_control.lean_angle_max();
|
|
|
|
// reset accel to current desired acceleration
|
|
if (_flags.reset_accel_to_lean_xy) {
|
|
_accel_target_jerk_limited.x = _accel_target.x;
|
|
_accel_target_jerk_limited.y = _accel_target.y;
|
|
_accel_target_filter.reset(Vector2f(_accel_target.x, _accel_target.y));
|
|
_flags.reset_accel_to_lean_xy = false;
|
|
}
|
|
|
|
// apply jerk limit of 17 m/s^3 - equates to a worst case of about 100 deg/sec/sec
|
|
float max_delta_accel = dt * POSCONTROL_JERK_LIMIT_CMSSS;
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Vector2f accel_in(_accel_target.x, _accel_target.y);
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Vector2f accel_change = accel_in-_accel_target_jerk_limited;
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float accel_change_length = accel_change.length();
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if(accel_change_length > max_delta_accel) {
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accel_change *= max_delta_accel/accel_change_length;
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}
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_accel_target_jerk_limited += accel_change;
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// lowpass filter on NE accel
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_accel_target_filter.set_cutoff_frequency(min(_accel_xy_filt_hz, 5.0f*ekfNavVelGainScaler));
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Vector2f accel_target_filtered = _accel_target_filter.apply(_accel_target_jerk_limited, dt);
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// rotate accelerations into body forward-right frame
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accel_forward = accel_target_filtered.x*_ahrs.cos_yaw() + accel_target_filtered.y*_ahrs.sin_yaw();
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accel_right = -accel_target_filtered.x*_ahrs.sin_yaw() + accel_target_filtered.y*_ahrs.cos_yaw();
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// update angle targets that will be passed to stabilize controller
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_pitch_target = constrain_float(atanf(-accel_forward/(GRAVITY_MSS * 100))*(18000/M_PI_F),-lean_angle_max, lean_angle_max);
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float cos_pitch_target = cosf(_pitch_target*M_PI_F/18000);
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_roll_target = constrain_float(atanf(accel_right*cos_pitch_target/(GRAVITY_MSS * 100))*(18000/M_PI_F), -lean_angle_max, lean_angle_max);
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}
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// get_lean_angles_to_accel - convert roll, pitch lean angles to lat/lon frame accelerations in cm/s/s
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void AC_PosControl::lean_angles_to_accel(float& accel_x_cmss, float& accel_y_cmss) const
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{
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// rotate our roll, pitch angles into lat/lon frame
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accel_x_cmss = (GRAVITY_MSS * 100) * (-(_ahrs.cos_yaw() * _ahrs.sin_pitch() / max(_ahrs.cos_pitch(),0.5f)) - _ahrs.sin_yaw() * _ahrs.sin_roll() / max(_ahrs.cos_roll(),0.5f));
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accel_y_cmss = (GRAVITY_MSS * 100) * (-(_ahrs.sin_yaw() * _ahrs.sin_pitch() / max(_ahrs.cos_pitch(),0.5f)) + _ahrs.cos_yaw() * _ahrs.sin_roll() / max(_ahrs.cos_roll(),0.5f));
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}
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/// calc_leash_length - calculates the horizontal leash length given a maximum speed, acceleration and position kP gain
|
|
float AC_PosControl::calc_leash_length(float speed_cms, float accel_cms, float kP) const
|
|
{
|
|
float leash_length;
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|
|
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// sanity check acceleration and avoid divide by zero
|
|
if (accel_cms <= 0.0f) {
|
|
accel_cms = POSCONTROL_ACCELERATION_MIN;
|
|
}
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|
|
|
// avoid divide by zero
|
|
if (kP <= 0.0f) {
|
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return POSCONTROL_LEASH_LENGTH_MIN;
|
|
}
|
|
|
|
// calculate leash length
|
|
if(speed_cms <= accel_cms / kP) {
|
|
// linear leash length based on speed close in
|
|
leash_length = speed_cms / kP;
|
|
}else{
|
|
// leash length grows at sqrt of speed further out
|
|
leash_length = (accel_cms / (2.0f*kP*kP)) + (speed_cms*speed_cms / (2.0f*accel_cms));
|
|
}
|
|
|
|
// ensure leash is at least 1m long
|
|
if( leash_length < POSCONTROL_LEASH_LENGTH_MIN ) {
|
|
leash_length = POSCONTROL_LEASH_LENGTH_MIN;
|
|
}
|
|
|
|
return leash_length;
|
|
}
|