/**************************************************************************** * * Copyright (c) 2017 Estimation and Control Library (ECL). All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in * the documentation and/or other materials provided with the * distribution. * 3. Neither the name ECL nor the names of its contributors may be * used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE * POSSIBILITY OF SUCH DAMAGE. * ****************************************************************************/ #include "tecs.h" #include #include using math::constrain; using math::max; using math::min; static constexpr float DT_MIN = 0.001f; ///< minimum allowed value of _dt (sec) static constexpr float DT_MAX = 1.0f; ///< max value of _dt allowed before a filter state reset is performed (sec) /** * @file tecs.cpp * * @author Paul Riseborough */ /* * This function implements a complementary filter to estimate the climb rate when * inertial nav data is not available. It also calculates a true airspeed derivative * which is used by the airspeed complimentary filter. */ void TECS::update_vehicle_state_estimates(float airspeed, const matrix::Dcmf &rotMat, const matrix::Vector3f &accel_body, bool altitude_lock, bool in_air, float altitude, bool vz_valid, float vz, float az) { // calculate the time lapsed since the last update uint64_t now = ecl_absolute_time(); float dt = constrain((now - _state_update_timestamp) * 1.0e-6f, DT_MIN, DT_MAX); bool reset_altitude = false; if (_state_update_timestamp == 0 || dt > DT_MAX) { dt = DT_DEFAULT; reset_altitude = true; } if (!altitude_lock || !in_air) { reset_altitude = true; } if (reset_altitude) { _vert_pos_state = altitude; if (vz_valid) { _vert_vel_state = -vz; } else { _vert_vel_state = 0.0f; } _vert_accel_state = 0.0f; _states_initalized = false; } _state_update_timestamp = now; _EAS = airspeed; _in_air = in_air; // Generate the height and climb rate state estimates if (vz_valid) { // Set the velocity and position state to the the INS data _vert_vel_state = -vz; _vert_pos_state = altitude; } else { // Get height acceleration float hgt_ddot_mea = -az; // If we have no vertical INS data, estimate the vertical velocity using a complementary filter // Perform filter calculation using backwards Euler integration // Coefficients selected to place all three filter poles at omega // Reference Paper: Optimising the Gains of the Baro-Inertial Vertical Channel // Widnall W.S, Sinha P.K, AIAA Journal of Guidance and Control, 78-1307R float omega2 = _hgt_estimate_freq * _hgt_estimate_freq; float hgt_err = altitude - _vert_pos_state; float vert_accel_input = hgt_err * omega2 * _hgt_estimate_freq; _vert_accel_state = _vert_accel_state + vert_accel_input * dt; float vert_vel_input = _vert_accel_state + hgt_ddot_mea + hgt_err * omega2 * 3.0f; _vert_vel_state = _vert_vel_state + vert_vel_input * dt; float vert_pos_input = _vert_vel_state + hgt_err * _hgt_estimate_freq * 3.0f; // If more than 1 second has elapsed since last update then reset the position state // to the measured height if (reset_altitude) { _vert_pos_state = altitude; } else { _vert_pos_state = _vert_pos_state + vert_pos_input * dt; } } // Update and average speed rate of change if airspeed is being measured if (ISFINITE(airspeed) && airspeed_sensor_enabled()) { // Assuming the vehicle is flying X axis forward, use the X axis measured acceleration // compensated for gravity to estimate the rate of change of speed float speed_deriv_raw = rotMat(2, 0) * CONSTANTS_ONE_G + accel_body(0); // Apply some noise filtering _speed_derivative = 0.95f * _speed_derivative + 0.05f * speed_deriv_raw; } else { _speed_derivative = 0.0f; } if (!_in_air) { _states_initalized = false; } } void TECS::_update_speed_states(float airspeed_setpoint, float indicated_airspeed, float EAS2TAS) { // Calculate the time in seconds since the last update and use the default time step value if out of bounds uint64_t now = ecl_absolute_time(); const float dt = constrain((now - _speed_update_timestamp) * 1.0e-6f, DT_MIN, DT_MAX); // Convert equivalent airspeed quantities to true airspeed _EAS_setpoint = airspeed_setpoint; _TAS_setpoint = _EAS_setpoint * EAS2TAS; _TAS_max = _indicated_airspeed_max * EAS2TAS; _TAS_min = _indicated_airspeed_min * EAS2TAS; // If airspeed measurements are not being used, fix the airspeed estimate to halfway between // min and max limits if (!ISFINITE(indicated_airspeed) || !airspeed_sensor_enabled()) { _EAS = 0.5f * (_indicated_airspeed_min + _indicated_airspeed_max); } else { _EAS = indicated_airspeed; } // If first time through or not flying, reset airspeed states if (_speed_update_timestamp == 0 || !_in_air) { _tas_rate_state = 0.0f; _tas_state = (_EAS * EAS2TAS); } // Obtain a smoothed airspeed estimate using a second order complementary filter // Update TAS rate state float tas_error = (_EAS * EAS2TAS) - _tas_state; float tas_rate_state_input = tas_error * _tas_estimate_freq * _tas_estimate_freq; // limit integrator input to prevent windup if (_tas_state < 3.1f) { tas_rate_state_input = max(tas_rate_state_input, 0.0f); } // Update TAS state _tas_rate_state = _tas_rate_state + tas_rate_state_input * dt; float tas_state_input = _tas_rate_state + _speed_derivative + tas_error * _tas_estimate_freq * 1.4142f; _tas_state = _tas_state + tas_state_input * dt; // Limit the airspeed state to a minimum of 3 m/s _tas_state = max(_tas_state, 3.0f); _speed_update_timestamp = now; } void TECS::_update_speed_setpoint() { // Set the airspeed demand to the minimum value if an underspeed or // or a uncontrolled descent condition exists to maximise climb rate if ((_uncommanded_descent_recovery) || (_underspeed_detected)) { _TAS_setpoint = _TAS_min; } _TAS_setpoint = constrain(_TAS_setpoint, _TAS_min, _TAS_max); // Calculate limits for the demanded rate of change of speed based on physical performance limits // with a 50% margin to allow the total energy controller to correct for errors. float velRateMax = 0.5f * _STE_rate_max / _tas_state; float velRateMin = 0.5f * _STE_rate_min / _tas_state; _TAS_setpoint_adj = constrain(_TAS_setpoint, _TAS_min, _TAS_max); // calculate the demanded rate of change of speed proportional to speed error // and apply performance limits _TAS_rate_setpoint = constrain((_TAS_setpoint_adj - _tas_state) * _speed_error_gain, velRateMin, velRateMax); } void TECS::_update_height_setpoint(float desired, float state) { // Detect first time through and initialize previous value to demand if (ISFINITE(desired) && fabsf(_hgt_setpoint_in_prev) < 0.1f) { _hgt_setpoint_in_prev = desired; } // Apply a 2 point moving average to demanded height to reduce // intersampling noise effects. if (ISFINITE(desired)) { _hgt_setpoint = 0.5f * (desired + _hgt_setpoint_in_prev); } else { _hgt_setpoint = _hgt_setpoint_in_prev; } _hgt_setpoint_in_prev = _hgt_setpoint; // Apply a rate limit to respect vehicle performance limitations if ((_hgt_setpoint - _hgt_setpoint_prev) > (_max_climb_rate * _dt)) { _hgt_setpoint = _hgt_setpoint_prev + _max_climb_rate * _dt; } else if ((_hgt_setpoint - _hgt_setpoint_prev) < (-_max_sink_rate * _dt)) { _hgt_setpoint = _hgt_setpoint_prev - _max_sink_rate * _dt; } _hgt_setpoint_prev = _hgt_setpoint; // Apply a first order noise filter _hgt_setpoint_adj = 0.1f * _hgt_setpoint + 0.9f * _hgt_setpoint_adj_prev; // Calculate the demanded climb rate proportional to height error plus a feedforward term to provide // tight tracking during steady climb and descent manoeuvres. _hgt_rate_setpoint = (_hgt_setpoint_adj - state) * _height_error_gain + _height_setpoint_gain_ff * (_hgt_setpoint_adj - _hgt_setpoint_adj_prev) / _dt; _hgt_setpoint_adj_prev = _hgt_setpoint_adj; // Limit the rate of change of height demand to respect vehicle performance limits if (_hgt_rate_setpoint > _max_climb_rate) { _hgt_rate_setpoint = _max_climb_rate; } else if (_hgt_rate_setpoint < -_max_sink_rate) { _hgt_rate_setpoint = -_max_sink_rate; } } void TECS::_detect_underspeed() { if (!_detect_underspeed_enabled) { _underspeed_detected = false; return; } if (((_tas_state < _TAS_min * 0.9f) && (_throttle_setpoint >= _throttle_setpoint_max * 0.95f)) || ((_vert_pos_state < _hgt_setpoint_adj) && _underspeed_detected)) { _underspeed_detected = true; } else { _underspeed_detected = false; } } void TECS::_update_energy_estimates() { // Calculate specific energy demands in units of (m**2/sec**2) _SPE_setpoint = _hgt_setpoint_adj * CONSTANTS_ONE_G; // potential energy _SKE_setpoint = 0.5f * _TAS_setpoint_adj * _TAS_setpoint_adj; // kinetic energy // Calculate specific energy rate demands in units of (m**2/sec**3) _SPE_rate_setpoint = _hgt_rate_setpoint * CONSTANTS_ONE_G; // potential energy rate of change _SKE_rate_setpoint = _tas_state * _TAS_rate_setpoint; // kinetic energy rate of change // Calculate specific energies in units of (m**2/sec**2) _SPE_estimate = _vert_pos_state * CONSTANTS_ONE_G; // potential energy _SKE_estimate = 0.5f * _tas_state * _tas_state; // kinetic energy // Calculate specific energy rates in units of (m**2/sec**3) _SPE_rate = _vert_vel_state * CONSTANTS_ONE_G; // potential energy rate of change _SKE_rate = _tas_state * _speed_derivative;// kinetic energy rate of change } void TECS::_update_throttle_setpoint(const float throttle_cruise, const matrix::Dcmf &rotMat) { // Calculate total energy error _STE_error = _SPE_setpoint - _SPE_estimate + _SKE_setpoint - _SKE_estimate; // Calculate demanded rate of change of total energy, respecting vehicle limits float STE_rate_setpoint = constrain((_SPE_rate_setpoint + _SKE_rate_setpoint), _STE_rate_min, _STE_rate_max); // Calculate the total energy rate error, applying a first order IIR filter // to reduce the effect of accelerometer noise _STE_rate_error = 0.2f * (STE_rate_setpoint - _SPE_rate - _SKE_rate) + 0.8f * _STE_rate_error; // Calculate the throttle demand if (_underspeed_detected) { // always use full throttle to recover from an underspeed condition _throttle_setpoint = 1.0f; } else { // Adjust the demanded total energy rate to compensate for induced drag rise in turns. // Assume induced drag scales linearly with normal load factor. // The additional normal load factor is given by (1/cos(bank angle) - 1) float cosPhi = sqrtf((rotMat(0, 1) * rotMat(0, 1)) + (rotMat(1, 1) * rotMat(1, 1))); STE_rate_setpoint = STE_rate_setpoint + _load_factor_correction * (1.0f / constrain(cosPhi, 0.1f, 1.0f) - 1.0f); // Calculate a predicted throttle from the demanded rate of change of energy, using the cruise throttle // as the starting point. Assume: // Specific total energy rate = _STE_rate_max is achieved when throttle is set to _throttle_setpoint_max // Specific total energy rate = 0 at cruise throttle // Specific total energy rate = _STE_rate_min is achieved when throttle is set to _throttle_setpoint_min float throttle_predicted = 0.0f; if (STE_rate_setpoint >= 0) { // throttle is between cruise and maximum throttle_predicted = throttle_cruise + STE_rate_setpoint / _STE_rate_max * (_throttle_setpoint_max - throttle_cruise); } else { // throttle is between cruise and minimum throttle_predicted = throttle_cruise + STE_rate_setpoint / _STE_rate_min * (_throttle_setpoint_min - throttle_cruise); } // Calculate gain scaler from specific energy error to throttle float STE_to_throttle = 1.0f / (_throttle_time_constant * (_STE_rate_max - _STE_rate_min)); // Add proportional and derivative control feedback to the predicted throttle and constrain to throttle limits _throttle_setpoint = (_STE_error + _STE_rate_error * _throttle_damping_gain) * STE_to_throttle + throttle_predicted; _throttle_setpoint = constrain(_throttle_setpoint, _throttle_setpoint_min, _throttle_setpoint_max); // Rate limit the throttle demand if (fabsf(_throttle_slewrate) > 0.01f) { float throttle_increment_limit = _dt * (_throttle_setpoint_max - _throttle_setpoint_min) * _throttle_slewrate; _throttle_setpoint = constrain(_throttle_setpoint, _last_throttle_setpoint - throttle_increment_limit, _last_throttle_setpoint + throttle_increment_limit); } _last_throttle_setpoint = _throttle_setpoint; if (_integrator_gain > 0.0f) { // Calculate throttle integrator state upper and lower limits with allowance for // 10% throttle saturation to accommodate noise on the demand. float integ_state_max = _throttle_setpoint_max - _throttle_setpoint + 0.1f; float integ_state_min = _throttle_setpoint_min - _throttle_setpoint - 0.1f; // Calculate a throttle demand from the integrated total energy error // This will be added to the total throttle demand to compensate for steady state errors _throttle_integ_state = _throttle_integ_state + (_STE_error * _integrator_gain) * _dt * STE_to_throttle; if (_climbout_mode_active) { // During climbout, set the integrator to maximum throttle to prevent transient throttle drop // at end of climbout when we transition to closed loop throttle control _throttle_integ_state = integ_state_max; } else { // Respect integrator limits during closed loop operation. _throttle_integ_state = constrain(_throttle_integ_state, integ_state_min, integ_state_max); } } else { _throttle_integ_state = 0.0f; } if (airspeed_sensor_enabled()) { // Add the integrator feedback during closed loop operation with an airspeed sensor _throttle_setpoint = _throttle_setpoint + _throttle_integ_state; } else { // when flying without an airspeed sensor, use the predicted throttle only _throttle_setpoint = throttle_predicted; } _throttle_setpoint = constrain(_throttle_setpoint, _throttle_setpoint_min, _throttle_setpoint_max); } } void TECS::_detect_uncommanded_descent() { /* * This function detects a condition that can occur when the demanded airspeed is greater than the * aircraft can achieve in level flight. When this occurs, the vehicle will continue to reduce height * while attempting to maintain speed. */ // Calculate rate of change of total specific energy float STE_rate = _SPE_rate + _SKE_rate; // If total energy is very low and reducing, throttle is high, and we are not in an underspeed condition, then enter uncommanded descent recovery mode bool enter_mode = !_uncommanded_descent_recovery && !_underspeed_detected && (_STE_error > 200.0f) && (STE_rate < 0.0f) && (_throttle_setpoint >= _throttle_setpoint_max * 0.9f); // If we enter an underspeed condition or recover the required total energy, then exit uncommanded descent recovery mode bool exit_mode = _uncommanded_descent_recovery && (_underspeed_detected || (_STE_error < 0.0f)); if (enter_mode) { _uncommanded_descent_recovery = true; } else if (exit_mode) { _uncommanded_descent_recovery = false; } } void TECS::_update_pitch_setpoint() { /* * The SKE_weighting variable controls how speed and height control are prioritised by the pitch demand calculation. * A weighting of 1 givea equal speed and height priority * A weighting of 0 gives 100% priority to height control and must be used when no airspeed measurement is available. * A weighting of 2 provides 100% priority to speed control and is used when: * a) an underspeed condition is detected. * b) during climbout where a minimum pitch angle has been set to ensure height is gained. If the airspeed * rises above the demanded value, the pitch angle demand is increased by the TECS controller to prevent the vehicle overspeeding. * The weighting can be adjusted between 0 and 2 depending on speed and height accuracy requirements. */ // Calculate the weighting applied to control of specific kinetic energy error float SKE_weighting = constrain(_pitch_speed_weight, 0.0f, 2.0f); if ((_underspeed_detected || _climbout_mode_active) && airspeed_sensor_enabled()) { SKE_weighting = 2.0f; } else if (!airspeed_sensor_enabled()) { SKE_weighting = 0.0f; } // Calculate the weighting applied to control of specific potential energy error float SPE_weighting = 2.0f - SKE_weighting; // Calculate the specific energy balance demand which specifies how the available total // energy should be allocated to speed (kinetic energy) and height (potential energy) float SEB_setpoint = _SPE_setpoint * SPE_weighting - _SKE_setpoint * SKE_weighting; // Calculate the specific energy balance rate demand float SEB_rate_setpoint = _SPE_rate_setpoint * SPE_weighting - _SKE_rate_setpoint * SKE_weighting; // Calculate the specific energy balance and balance rate error _SEB_error = SEB_setpoint - (_SPE_estimate * SPE_weighting - _SKE_estimate * SKE_weighting); _SEB_rate_error = SEB_rate_setpoint - (_SPE_rate * SPE_weighting - _SKE_rate * SKE_weighting); // Calculate derivative from change in climb angle to rate of change of specific energy balance float climb_angle_to_SEB_rate = _tas_state * _pitch_time_constant * CONSTANTS_ONE_G; if (_integrator_gain > 0.0f) { // Calculate pitch integrator input term float pitch_integ_input = _SEB_error * _integrator_gain; // Prevent the integrator changing in a direction that will increase pitch demand saturation // Decay the integrator at the control loop time constant if the pitch demand from the previous time step is saturated if (_pitch_setpoint_unc > _pitch_setpoint_max) { pitch_integ_input = min(pitch_integ_input, min((_pitch_setpoint_max - _pitch_setpoint_unc) * climb_angle_to_SEB_rate / _pitch_time_constant, 0.0f)); } else if (_pitch_setpoint_unc < _pitch_setpoint_min) { pitch_integ_input = max(pitch_integ_input, max((_pitch_setpoint_min - _pitch_setpoint_unc) * climb_angle_to_SEB_rate / _pitch_time_constant, 0.0f)); } // Update the pitch integrator state. _pitch_integ_state = _pitch_integ_state + pitch_integ_input * _dt; } else { _pitch_integ_state = 0.0f; } // Calculate a specific energy correction that doesn't include the integrator contribution float SEB_correction = _SEB_error + _SEB_rate_error * _pitch_damping_gain + SEB_rate_setpoint * _pitch_time_constant; // During climbout, bias the demanded pitch angle so that a zero speed error produces a pitch angle // demand equal to the minimum pitch angle set by the mission plan. This prevents the integrator // having to catch up before the nose can be raised to reduce excess speed during climbout. if (_climbout_mode_active) { SEB_correction += _pitch_setpoint_min * climb_angle_to_SEB_rate; } // Sum the correction terms and convert to a pitch angle demand. This calculation assumes: // a) The climb angle follows pitch angle with a lag that is small enough not to destabilise the control loop. // b) The offset between climb angle and pitch angle (angle of attack) is constant, excluding the effect of // pitch transients due to control action or turbulence. _pitch_setpoint_unc = (SEB_correction + _pitch_integ_state) / climb_angle_to_SEB_rate; _pitch_setpoint = constrain(_pitch_setpoint_unc, _pitch_setpoint_min, _pitch_setpoint_max); // Comply with the specified vertical acceleration limit by applying a pitch rate limit float ptchRateIncr = _dt * _vert_accel_limit / _tas_state; if ((_pitch_setpoint - _last_pitch_setpoint) > ptchRateIncr) { _pitch_setpoint = _last_pitch_setpoint + ptchRateIncr; } else if ((_pitch_setpoint - _last_pitch_setpoint) < -ptchRateIncr) { _pitch_setpoint = _last_pitch_setpoint - ptchRateIncr; } _last_pitch_setpoint = _pitch_setpoint; } void TECS::_initialize_states(float pitch, float throttle_cruise, float baro_altitude, float pitch_min_climbout, float EAS2TAS) { if (_pitch_update_timestamp == 0 || _dt > DT_MAX || !_in_air || !_states_initalized) { // On first time through or when not using TECS of if there has been a large time slip, // states must be reset to allow filters to a clean start _vert_accel_state = 0.0f; _vert_vel_state = 0.0f; _vert_pos_state = baro_altitude; _tas_rate_state = 0.0f; _tas_state = _EAS * EAS2TAS; _throttle_integ_state = 0.0f; _pitch_integ_state = 0.0f; _last_throttle_setpoint = (_in_air ? throttle_cruise : 0.0f);; _last_pitch_setpoint = constrain(pitch, _pitch_setpoint_min, _pitch_setpoint_max); _pitch_setpoint_unc = _last_pitch_setpoint; _hgt_setpoint_adj_prev = baro_altitude; _hgt_setpoint_adj = _hgt_setpoint_adj_prev; _hgt_setpoint_prev = _hgt_setpoint_adj_prev; _hgt_setpoint_in_prev = _hgt_setpoint_adj_prev; _TAS_setpoint_last = _EAS * EAS2TAS; _TAS_setpoint_adj = _TAS_setpoint_last; _underspeed_detected = false; _uncommanded_descent_recovery = false; _STE_rate_error = 0.0f; if (_dt > DT_MAX || _dt < DT_MIN) { _dt = DT_DEFAULT; } } else if (_climbout_mode_active) { // During climbout use the lower pitch angle limit specified by the // calling controller _pitch_setpoint_min = pitch_min_climbout; // throttle lower limit is set to a value that prevents throttle reduction _throttle_setpoint_min = _throttle_setpoint_max - 0.01f; // height demand and associated states are set to track the measured height _hgt_setpoint_adj_prev = baro_altitude; _hgt_setpoint_adj = _hgt_setpoint_adj_prev; _hgt_setpoint_prev = _hgt_setpoint_adj_prev; // airspeed demand states are set to track the measured airspeed _TAS_setpoint_last = _EAS * EAS2TAS; _TAS_setpoint_adj = _EAS * EAS2TAS; // disable speed and decent error condition checks _underspeed_detected = false; _uncommanded_descent_recovery = false; } _states_initalized = true; } void TECS::_update_STE_rate_lim() { // Calculate the specific total energy upper rate limits from the max throttle climb rate _STE_rate_max = _max_climb_rate * CONSTANTS_ONE_G; // Calculate the specific total energy lower rate limits from the min throttle sink rate _STE_rate_min = - _min_sink_rate * CONSTANTS_ONE_G; } void TECS::update_pitch_throttle(const matrix::Dcmf &rotMat, float pitch, float baro_altitude, float hgt_setpoint, float EAS_setpoint, float indicated_airspeed, float eas_to_tas, bool climb_out_setpoint, float pitch_min_climbout, float throttle_min, float throttle_max, float throttle_cruise, float pitch_limit_min, float pitch_limit_max) { // Calculate the time since last update (seconds) uint64_t now = ecl_absolute_time(); _dt = constrain((now - _pitch_update_timestamp) * 1e-6f, DT_MIN, DT_MAX); // Set class variables from inputs _throttle_setpoint_max = throttle_max; _throttle_setpoint_min = throttle_min; _pitch_setpoint_max = pitch_limit_max; _pitch_setpoint_min = pitch_limit_min; _climbout_mode_active = climb_out_setpoint; // Initialize selected states and variables as required _initialize_states(pitch, throttle_cruise, baro_altitude, pitch_min_climbout, eas_to_tas); // Don't run TECS control algorithms when not in flight if (!_in_air) { return; } // Update the true airspeed state estimate _update_speed_states(EAS_setpoint, indicated_airspeed, eas_to_tas); // Calculate rate limits for specific total energy _update_STE_rate_lim(); // Detect an underspeed condition _detect_underspeed(); // Detect an uncommanded descent caused by an unachievable airspeed demand _detect_uncommanded_descent(); // Calculate the demanded true airspeed _update_speed_setpoint(); // Calculate the demanded height _update_height_setpoint(hgt_setpoint, baro_altitude); // Calculate the specific energy values required by the control loop _update_energy_estimates(); // Calculate the throttle demand _update_throttle_setpoint(throttle_cruise, rotMat); // Calculate the pitch demand _update_pitch_setpoint(); // Update time stamps _pitch_update_timestamp = now; // Set TECS mode for next frame if (_underspeed_detected) { _tecs_mode = ECL_TECS_MODE_UNDERSPEED; } else if (_uncommanded_descent_recovery) { _tecs_mode = ECL_TECS_MODE_BAD_DESCENT; } else if (_climbout_mode_active) { _tecs_mode = ECL_TECS_MODE_CLIMBOUT; } else { // This is the default operation mode _tecs_mode = ECL_TECS_MODE_NORMAL; } }