#include "Plane.h" /* get a speed scaling number for control surfaces. This is applied to PIDs to change the scaling of the PID with speed. At high speed we move the surfaces less, and at low speeds we move them more. */ float Plane::get_speed_scaler(void) { float aspeed, speed_scaler; if (ahrs.airspeed_estimate(aspeed)) { if (aspeed > auto_state.highest_airspeed) { auto_state.highest_airspeed = aspeed; } if (aspeed > 0.0001f) { speed_scaler = g.scaling_speed / aspeed; } else { speed_scaler = 2.0; } // ensure we have scaling over the full configured airspeed float scale_min = MIN(0.5, (0.5 * aparm.airspeed_min) / g.scaling_speed); float scale_max = MAX(2.0, (1.5 * aparm.airspeed_max) / g.scaling_speed); speed_scaler = constrain_float(speed_scaler, scale_min, scale_max); if (quadplane.in_vtol_mode() && hal.util->get_soft_armed()) { // when in VTOL modes limit surface movement at low speed to prevent instability float threshold = aparm.airspeed_min * 0.5; if (aspeed < threshold) { float new_scaler = linear_interpolate(0.001, g.scaling_speed / threshold, aspeed, 0, threshold); speed_scaler = MIN(speed_scaler, new_scaler); // we also decay the integrator to prevent an integrator from before // we were at low speed persistint at high speed rollController.decay_I(); pitchController.decay_I(); yawController.decay_I(); } } } else if (hal.util->get_soft_armed()) { // scale assumed surface movement using throttle output float throttle_out = MAX(SRV_Channels::get_output_scaled(SRV_Channel::k_throttle), 1); speed_scaler = sqrtf(THROTTLE_CRUISE / throttle_out); // This case is constrained tighter as we don't have real speed info speed_scaler = constrain_float(speed_scaler, 0.6f, 1.67f); } else { // no speed estimate and not armed, use a unit scaling speed_scaler = 1; } if (!plane.ahrs.airspeed_sensor_enabled() && (plane.g2.flight_options & FlightOptions::SURPRESS_TKOFF_SCALING) && (plane.flight_stage == AP_Vehicle::FixedWing::FLIGHT_TAKEOFF)) { //scaling is surpressed during climb phase of automatic takeoffs with no airspeed sensor being used due to problems with inaccurate airspeed estimates return MIN(speed_scaler, 1.0f) ; } return speed_scaler; } /* return true if the current settings and mode should allow for stick mixing */ bool Plane::stick_mixing_enabled(void) { #if AC_FENCE == ENABLED const bool stickmixing = fence_stickmixing(); #else const bool stickmixing = true; #endif if (control_mode->does_auto_throttle() && plane.control_mode->does_auto_navigation()) { // we're in an auto mode. Check the stick mixing flag if (g.stick_mixing != STICK_MIXING_DISABLED && g.stick_mixing != STICK_MIXING_VTOL_YAW && stickmixing && failsafe.state == FAILSAFE_NONE && !rc_failsafe_active()) { // we're in an auto mode, and haven't triggered failsafe return true; } else { return false; } } if (failsafe.rc_failsafe && g.fs_action_short == FS_ACTION_SHORT_FBWA) { // don't do stick mixing in FBWA glide mode return false; } // non-auto mode. Always do stick mixing return true; } /* this is the main roll stabilization function. It takes the previously set nav_roll calculates roll servo_out to try to stabilize the plane at the given roll */ void Plane::stabilize_roll(float speed_scaler) { if (fly_inverted()) { // we want to fly upside down. We need to cope with wrap of // the roll_sensor interfering with wrap of nav_roll, which // would really confuse the PID code. The easiest way to // handle this is to ensure both go in the same direction from // zero nav_roll_cd += 18000; if (ahrs.roll_sensor < 0) nav_roll_cd -= 36000; } bool disable_integrator = false; if (control_mode == &mode_stabilize && channel_roll->get_control_in() != 0) { disable_integrator = true; } int32_t roll_out; if (!quadplane.use_fw_attitude_controllers()) { // use the VTOL rate for control, to ensure consistency const auto &pid_info = quadplane.attitude_control->get_rate_roll_pid().get_pid_info(); roll_out = rollController.get_rate_out(degrees(pid_info.target), speed_scaler); /* when slaving fixed wing control to VTOL control we need to decay the integrator to prevent opposing integrators balancing between the two controllers */ rollController.decay_I(); } else { roll_out = rollController.get_servo_out(nav_roll_cd - ahrs.roll_sensor, speed_scaler, disable_integrator); } SRV_Channels::set_output_scaled(SRV_Channel::k_aileron, roll_out); } /* this is the main pitch stabilization function. It takes the previously set nav_pitch and calculates servo_out values to try to stabilize the plane at the given attitude. */ void Plane::stabilize_pitch(float speed_scaler) { int8_t force_elevator = takeoff_tail_hold(); if (force_elevator != 0) { // we are holding the tail down during takeoff. Just convert // from a percentage to a -4500..4500 centidegree angle SRV_Channels::set_output_scaled(SRV_Channel::k_elevator, 45*force_elevator); return; } int32_t demanded_pitch = nav_pitch_cd + g.pitch_trim_cd + SRV_Channels::get_output_scaled(SRV_Channel::k_throttle) * g.kff_throttle_to_pitch; bool disable_integrator = false; if (control_mode == &mode_stabilize && channel_pitch->get_control_in() != 0) { disable_integrator = true; } int32_t pitch_out; if (!quadplane.use_fw_attitude_controllers()) { // use the VTOL rate for control, to ensure consistency const auto &pid_info = quadplane.attitude_control->get_rate_pitch_pid().get_pid_info(); pitch_out = pitchController.get_rate_out(degrees(pid_info.target), speed_scaler); /* when slaving fixed wing control to VTOL control we need to decay the integrator to prevent opposing integrators balancing between the two controllers */ pitchController.decay_I(); } else { // if LANDING_FLARE RCx_OPTION switch is set and in FW mode, manual throttle,throttle idle then set pitch to LAND_PITCH_CD if flight option FORCE_FLARE_ATTITUDE is set if (!quadplane.in_transition() && !control_mode->is_vtol_mode() && channel_throttle->in_trim_dz() && !control_mode->does_auto_throttle() && flare_mode == FlareMode::ENABLED_PITCH_TARGET) { demanded_pitch = landing.get_pitch_cd(); } pitch_out = pitchController.get_servo_out(demanded_pitch - ahrs.pitch_sensor, speed_scaler, disable_integrator); } SRV_Channels::set_output_scaled(SRV_Channel::k_elevator, pitch_out); } /* this gives the user control of the aircraft in stabilization modes */ void Plane::stabilize_stick_mixing_direct() { if (!stick_mixing_enabled() || control_mode == &mode_acro || control_mode == &mode_fbwa || control_mode == &mode_autotune || control_mode == &mode_fbwb || control_mode == &mode_cruise || control_mode == &mode_qstabilize || control_mode == &mode_qhover || control_mode == &mode_qloiter || control_mode == &mode_qland || control_mode == &mode_qrtl || control_mode == &mode_qacro || control_mode == &mode_training || control_mode == &mode_qautotune) { return; } int16_t aileron = SRV_Channels::get_output_scaled(SRV_Channel::k_aileron); aileron = channel_roll->stick_mixing(aileron); SRV_Channels::set_output_scaled(SRV_Channel::k_aileron, aileron); int16_t elevator = SRV_Channels::get_output_scaled(SRV_Channel::k_elevator); elevator = channel_pitch->stick_mixing(elevator); SRV_Channels::set_output_scaled(SRV_Channel::k_elevator, elevator); } /* this gives the user control of the aircraft in stabilization modes using FBW style controls */ void Plane::stabilize_stick_mixing_fbw() { if (!stick_mixing_enabled() || control_mode == &mode_acro || control_mode == &mode_fbwa || control_mode == &mode_autotune || control_mode == &mode_fbwb || control_mode == &mode_cruise || control_mode == &mode_qstabilize || control_mode == &mode_qhover || control_mode == &mode_qloiter || control_mode == &mode_qland || control_mode == &mode_qrtl || control_mode == &mode_qacro || control_mode == &mode_training || control_mode == &mode_qautotune || (control_mode == &mode_auto && g.auto_fbw_steer == 42)) { return; } // do FBW style stick mixing. We don't treat it linearly // however. For inputs up to half the maximum, we use linear // addition to the nav_roll and nav_pitch. Above that it goes // non-linear and ends up as 2x the maximum, to ensure that // the user can direct the plane in any direction with stick // mixing. float roll_input = channel_roll->norm_input(); if (roll_input > 0.5f) { roll_input = (3*roll_input - 1); } else if (roll_input < -0.5f) { roll_input = (3*roll_input + 1); } nav_roll_cd += roll_input * roll_limit_cd; nav_roll_cd = constrain_int32(nav_roll_cd, -roll_limit_cd, roll_limit_cd); float pitch_input = channel_pitch->norm_input(); if (pitch_input > 0.5f) { pitch_input = (3*pitch_input - 1); } else if (pitch_input < -0.5f) { pitch_input = (3*pitch_input + 1); } if (fly_inverted()) { pitch_input = -pitch_input; } if (pitch_input > 0) { nav_pitch_cd += pitch_input * aparm.pitch_limit_max_cd; } else { nav_pitch_cd += -(pitch_input * pitch_limit_min_cd); } nav_pitch_cd = constrain_int32(nav_pitch_cd, pitch_limit_min_cd, aparm.pitch_limit_max_cd.get()); } /* stabilize the yaw axis. There are 3 modes of operation: - hold a specific heading with ground steering - rate controlled with ground steering - yaw control for coordinated flight */ void Plane::stabilize_yaw(float speed_scaler) { if (landing.is_flaring()) { // in flaring then enable ground steering steering_control.ground_steering = true; } else { // otherwise use ground steering when no input control and we // are below the GROUND_STEER_ALT steering_control.ground_steering = (channel_roll->get_control_in() == 0 && fabsf(relative_altitude) < g.ground_steer_alt); if (!landing.is_ground_steering_allowed()) { // don't use ground steering on landing approach steering_control.ground_steering = false; } } /* first calculate steering_control.steering for a nose or tail wheel. We use "course hold" mode for the rudder when either performing a flare (when the wings are held level) or when in course hold in FBWA mode (when we are below GROUND_STEER_ALT) */ if (landing.is_flaring() || (steer_state.hold_course_cd != -1 && steering_control.ground_steering)) { calc_nav_yaw_course(); } else if (steering_control.ground_steering) { calc_nav_yaw_ground(); } /* now calculate steering_control.rudder for the rudder */ calc_nav_yaw_coordinated(speed_scaler); } /* a special stabilization function for training mode */ void Plane::stabilize_training(float speed_scaler) { if (training_manual_roll) { SRV_Channels::set_output_scaled(SRV_Channel::k_aileron, channel_roll->get_control_in()); } else { // calculate what is needed to hold stabilize_roll(speed_scaler); if ((nav_roll_cd > 0 && channel_roll->get_control_in() < SRV_Channels::get_output_scaled(SRV_Channel::k_aileron)) || (nav_roll_cd < 0 && channel_roll->get_control_in() > SRV_Channels::get_output_scaled(SRV_Channel::k_aileron))) { // allow user to get out of the roll SRV_Channels::set_output_scaled(SRV_Channel::k_aileron, channel_roll->get_control_in()); } } if (training_manual_pitch) { SRV_Channels::set_output_scaled(SRV_Channel::k_elevator, channel_pitch->get_control_in()); } else { stabilize_pitch(speed_scaler); if ((nav_pitch_cd > 0 && channel_pitch->get_control_in() < SRV_Channels::get_output_scaled(SRV_Channel::k_elevator)) || (nav_pitch_cd < 0 && channel_pitch->get_control_in() > SRV_Channels::get_output_scaled(SRV_Channel::k_elevator))) { // allow user to get back to level SRV_Channels::set_output_scaled(SRV_Channel::k_elevator, channel_pitch->get_control_in()); } } stabilize_yaw(speed_scaler); } /* this is the ACRO mode stabilization function. It does rate stabilization on roll and pitch axes */ void Plane::stabilize_acro(float speed_scaler) { float roll_rate = (channel_roll->get_control_in()/4500.0f) * g.acro_roll_rate; float pitch_rate = (channel_pitch->get_control_in()/4500.0f) * g.acro_pitch_rate; /* check for special roll handling near the pitch poles */ if (g.acro_locking && is_zero(roll_rate)) { /* we have no roll stick input, so we will enter "roll locked" mode, and hold the roll we had when the stick was released */ if (!acro_state.locked_roll) { acro_state.locked_roll = true; acro_state.locked_roll_err = 0; } else { acro_state.locked_roll_err += ahrs.get_gyro().x * G_Dt; } int32_t roll_error_cd = -ToDeg(acro_state.locked_roll_err)*100; nav_roll_cd = ahrs.roll_sensor + roll_error_cd; // try to reduce the integrated angular error to zero. We set // 'stabilze' to true, which disables the roll integrator SRV_Channels::set_output_scaled(SRV_Channel::k_aileron, rollController.get_servo_out(roll_error_cd, speed_scaler, true)); } else { /* aileron stick is non-zero, use pure rate control until the user releases the stick */ acro_state.locked_roll = false; SRV_Channels::set_output_scaled(SRV_Channel::k_aileron, rollController.get_rate_out(roll_rate, speed_scaler)); } if (g.acro_locking && is_zero(pitch_rate)) { /* user has zero pitch stick input, so we lock pitch at the point they release the stick */ if (!acro_state.locked_pitch) { acro_state.locked_pitch = true; acro_state.locked_pitch_cd = ahrs.pitch_sensor; } // try to hold the locked pitch. Note that we have the pitch // integrator enabled, which helps with inverted flight nav_pitch_cd = acro_state.locked_pitch_cd; SRV_Channels::set_output_scaled(SRV_Channel::k_elevator, pitchController.get_servo_out(nav_pitch_cd - ahrs.pitch_sensor, speed_scaler, false)); } else { /* user has non-zero pitch input, use a pure rate controller */ acro_state.locked_pitch = false; SRV_Channels::set_output_scaled(SRV_Channel::k_elevator, pitchController.get_rate_out(pitch_rate, speed_scaler)); } steering_control.steering = rudder_input(); if (plane.g2.flight_options & FlightOptions::ACRO_YAW_DAMPER) { // use yaw controller calc_nav_yaw_coordinated(speed_scaler); } else { /* manual rudder */ steering_control.rudder = steering_control.steering; } } /* main stabilization function for all 3 axes */ void Plane::stabilize() { if (control_mode == &mode_manual) { // reset steering controls steer_state.locked_course = false; steer_state.locked_course_err = 0; return; } float speed_scaler = get_speed_scaler(); uint32_t now = AP_HAL::millis(); if (quadplane.in_tailsitter_vtol_transition(now)) { /* during transition to vtol in a tailsitter try to raise the nose while keeping the wings level */ uint32_t dt = now - quadplane.transition_start_ms; // multiply by 0.1 to convert (degrees/second * milliseconds) to centi degrees nav_pitch_cd = constrain_float(quadplane.transition_initial_pitch + (quadplane.tailsitter.transition_rate_vtol * dt) * 0.1f, -8500, 8500); nav_roll_cd = 0; } if (now - last_stabilize_ms > 2000) { // if we haven't run the rate controllers for 2 seconds then // reset the integrators rollController.reset_I(); pitchController.reset_I(); yawController.reset_I(); // and reset steering controls steer_state.locked_course = false; steer_state.locked_course_err = 0; } last_stabilize_ms = now; if (control_mode == &mode_training) { stabilize_training(speed_scaler); } else if (control_mode == &mode_acro) { stabilize_acro(speed_scaler); } else if ((control_mode == &mode_qstabilize || control_mode == &mode_qhover || control_mode == &mode_qloiter || control_mode == &mode_qland || control_mode == &mode_qrtl || control_mode == &mode_qacro || control_mode == &mode_qautotune) && !quadplane.in_tailsitter_vtol_transition(now)) { quadplane.control_run(); } else { if (g.stick_mixing == STICK_MIXING_FBW && control_mode != &mode_stabilize) { stabilize_stick_mixing_fbw(); } stabilize_roll(speed_scaler); stabilize_pitch(speed_scaler); if (g.stick_mixing == STICK_MIXING_DIRECT || control_mode == &mode_stabilize) { stabilize_stick_mixing_direct(); } stabilize_yaw(speed_scaler); } /* see if we should zero the attitude controller integrators. */ if (get_throttle_input() == 0 && fabsf(relative_altitude) < 5.0f && fabsf(barometer.get_climb_rate()) < 0.5f && ahrs.groundspeed() < 3) { // we are low, with no climb rate, and zero throttle, and very // low ground speed. Zero the attitude controller // integrators. This prevents integrator buildup pre-takeoff. rollController.reset_I(); pitchController.reset_I(); yawController.reset_I(); // if moving very slowly also zero the steering integrator if (ahrs.groundspeed() < 1) { steerController.reset_I(); } } } void Plane::calc_throttle() { if (aparm.throttle_cruise <= 1) { // user has asked for zero throttle - this may be done by a // mission which wants to turn off the engine for a parachute // landing SRV_Channels::set_output_scaled(SRV_Channel::k_throttle, 0); return; } int32_t commanded_throttle = SpdHgt_Controller->get_throttle_demand(); // Received an external msg that guides throttle in the last 3 seconds? if (control_mode->is_guided_mode() && plane.guided_state.last_forced_throttle_ms > 0 && millis() - plane.guided_state.last_forced_throttle_ms < 3000) { commanded_throttle = plane.guided_state.forced_throttle; } SRV_Channels::set_output_scaled(SRV_Channel::k_throttle, commanded_throttle); } /***************************************** * Calculate desired roll/pitch/yaw angles (in medium freq loop) *****************************************/ /* calculate yaw control for coordinated flight */ void Plane::calc_nav_yaw_coordinated(float speed_scaler) { bool disable_integrator = false; int16_t rudder_in = rudder_input(); int16_t commanded_rudder; // Received an external msg that guides yaw in the last 3 seconds? if (control_mode->is_guided_mode() && plane.guided_state.last_forced_rpy_ms.z > 0 && millis() - plane.guided_state.last_forced_rpy_ms.z < 3000) { commanded_rudder = plane.guided_state.forced_rpy_cd.z; } else { if (control_mode == &mode_stabilize && rudder_in != 0) { disable_integrator = true; } commanded_rudder = yawController.get_servo_out(speed_scaler, disable_integrator); // add in rudder mixing from roll commanded_rudder += SRV_Channels::get_output_scaled(SRV_Channel::k_aileron) * g.kff_rudder_mix; commanded_rudder += rudder_in; } steering_control.rudder = constrain_int16(commanded_rudder, -4500, 4500); } /* calculate yaw control for ground steering with specific course */ void Plane::calc_nav_yaw_course(void) { // holding a specific navigation course on the ground. Used in // auto-takeoff and landing int32_t bearing_error_cd = nav_controller->bearing_error_cd(); steering_control.steering = steerController.get_steering_out_angle_error(bearing_error_cd); if (stick_mixing_enabled()) { steering_control.steering = channel_rudder->stick_mixing(steering_control.steering); } steering_control.steering = constrain_int16(steering_control.steering, -4500, 4500); } /* calculate yaw control for ground steering */ void Plane::calc_nav_yaw_ground(void) { if (gps.ground_speed() < 1 && get_throttle_input() == 0 && flight_stage != AP_Vehicle::FixedWing::FLIGHT_TAKEOFF && flight_stage != AP_Vehicle::FixedWing::FLIGHT_ABORT_LAND) { // manual rudder control while still steer_state.locked_course = false; steer_state.locked_course_err = 0; steering_control.steering = rudder_input(); return; } float steer_rate = (rudder_input()/4500.0f) * g.ground_steer_dps; if (flight_stage == AP_Vehicle::FixedWing::FLIGHT_TAKEOFF || flight_stage == AP_Vehicle::FixedWing::FLIGHT_ABORT_LAND) { steer_rate = 0; } if (!is_zero(steer_rate)) { // pilot is giving rudder input steer_state.locked_course = false; } else if (!steer_state.locked_course) { // pilot has released the rudder stick or we are still - lock the course steer_state.locked_course = true; if (flight_stage != AP_Vehicle::FixedWing::FLIGHT_TAKEOFF && flight_stage != AP_Vehicle::FixedWing::FLIGHT_ABORT_LAND) { steer_state.locked_course_err = 0; } } if (!steer_state.locked_course) { // use a rate controller at the pilot specified rate steering_control.steering = steerController.get_steering_out_rate(steer_rate); } else { // use a error controller on the summed error int32_t yaw_error_cd = -ToDeg(steer_state.locked_course_err)*100; steering_control.steering = steerController.get_steering_out_angle_error(yaw_error_cd); } steering_control.steering = constrain_int16(steering_control.steering, -4500, 4500); } /* calculate a new nav_pitch_cd from the speed height controller */ void Plane::calc_nav_pitch() { // Calculate the Pitch of the plane // -------------------------------- int32_t commanded_pitch = SpdHgt_Controller->get_pitch_demand(); // Received an external msg that guides roll in the last 3 seconds? if (control_mode->is_guided_mode() && plane.guided_state.last_forced_rpy_ms.y > 0 && millis() - plane.guided_state.last_forced_rpy_ms.y < 3000) { commanded_pitch = plane.guided_state.forced_rpy_cd.y; } nav_pitch_cd = constrain_int32(commanded_pitch, pitch_limit_min_cd, aparm.pitch_limit_max_cd.get()); } /* calculate a new nav_roll_cd from the navigation controller */ void Plane::calc_nav_roll() { int32_t commanded_roll = nav_controller->nav_roll_cd(); // Received an external msg that guides roll in the last 3 seconds? if (control_mode->is_guided_mode() && plane.guided_state.last_forced_rpy_ms.x > 0 && millis() - plane.guided_state.last_forced_rpy_ms.x < 3000) { commanded_roll = plane.guided_state.forced_rpy_cd.x; #if OFFBOARD_GUIDED == ENABLED // guided_state.target_heading is radians at this point between -pi and pi ( defaults to -4 ) } else if ((control_mode == &mode_guided) && (guided_state.target_heading_type != GUIDED_HEADING_NONE) ) { uint32_t tnow = AP_HAL::millis(); float delta = (tnow - guided_state.target_heading_time_ms) * 1e-3f; guided_state.target_heading_time_ms = tnow; float error = 0.0f; if (guided_state.target_heading_type == GUIDED_HEADING_HEADING) { error = wrap_PI(guided_state.target_heading - AP::ahrs().yaw); } else { Vector2f groundspeed = AP::ahrs().groundspeed_vector(); error = wrap_PI(guided_state.target_heading - atan2f(-groundspeed.y, -groundspeed.x) + M_PI); } float bank_limit = degrees(atanf(guided_state.target_heading_accel_limit/GRAVITY_MSS)) * 1e2f; g2.guidedHeading.update_error(error); // push error into AC_PID , possible improvement is to use update_all instead.? g2.guidedHeading.set_dt(delta); float i = g2.guidedHeading.get_i(); // get integrator TODO if (((is_negative(error) && !guided_state.target_heading_limit_low) || (is_positive(error) && !guided_state.target_heading_limit_high))) { i = g2.guidedHeading.get_i(); } float desired = g2.guidedHeading.get_p() + i + g2.guidedHeading.get_d(); guided_state.target_heading_limit_low = (desired <= -bank_limit); guided_state.target_heading_limit_high = (desired >= bank_limit); commanded_roll = constrain_float(desired, -bank_limit, bank_limit); #endif // OFFBOARD_GUIDED == ENABLED } nav_roll_cd = constrain_int32(commanded_roll, -roll_limit_cd, roll_limit_cd); update_load_factor(); } /* adjust nav_pitch_cd for STAB_PITCH_DOWN_CD. This is used to make keeping up good airspeed in FBWA mode easier, as the plane will automatically pitch down a little when at low throttle. It makes FBWA landings without stalling much easier. */ void Plane::adjust_nav_pitch_throttle(void) { int8_t throttle = throttle_percentage(); if (throttle >= 0 && throttle < aparm.throttle_cruise && flight_stage != AP_Vehicle::FixedWing::FLIGHT_VTOL) { float p = (aparm.throttle_cruise - throttle) / (float)aparm.throttle_cruise; nav_pitch_cd -= g.stab_pitch_down * 100.0f * p; } } /* calculate a new aerodynamic_load_factor and limit nav_roll_cd to ensure that the load factor does not take us below the sustainable airspeed */ void Plane::update_load_factor(void) { float demanded_roll = fabsf(nav_roll_cd*0.01f); if (demanded_roll > 85) { // limit to 85 degrees to prevent numerical errors demanded_roll = 85; } aerodynamic_load_factor = 1.0f / safe_sqrt(cosf(radians(demanded_roll))); if (quadplane.in_transition() && (quadplane.options & QuadPlane::OPTION_LEVEL_TRANSITION)) { // the user wants transitions to be kept level to within LEVEL_ROLL_LIMIT roll_limit_cd = MIN(roll_limit_cd, g.level_roll_limit*100); nav_roll_cd = constrain_int32(nav_roll_cd, -roll_limit_cd, roll_limit_cd); return; } if (!aparm.stall_prevention) { // stall prevention is disabled return; } if (fly_inverted()) { // no roll limits when inverted return; } if (quadplane.tailsitter_active()) { // no limits while hovering return; } float max_load_factor = smoothed_airspeed / MAX(aparm.airspeed_min, 1); if (max_load_factor <= 1) { // our airspeed is below the minimum airspeed. Limit roll to // 25 degrees nav_roll_cd = constrain_int32(nav_roll_cd, -2500, 2500); roll_limit_cd = MIN(roll_limit_cd, 2500); } else if (max_load_factor < aerodynamic_load_factor) { // the demanded nav_roll would take us past the aerodymamic // load limit. Limit our roll to a bank angle that will keep // the load within what the airframe can handle. We always // allow at least 25 degrees of roll however, to ensure the // aircraft can be maneuvered with a bad airspeed estimate. At // 25 degrees the load factor is 1.1 (10%) int32_t roll_limit = degrees(acosf(sq(1.0f / max_load_factor)))*100; if (roll_limit < 2500) { roll_limit = 2500; } nav_roll_cd = constrain_int32(nav_roll_cd, -roll_limit, roll_limit); roll_limit_cd = MIN(roll_limit_cd, roll_limit); } }