ardupilot/libraries/AC_AttitudeControl/AC_AttitudeControl_Multi.cpp

// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: t -*-

#include "AC_AttitudeControl_Multi.h"
#include <AP_HAL/AP_HAL.h>
#include <AP_Math/AP_Math.h>

// get lean angle max for pilot input that prioritises altitude hold over lean angle
float AC_AttitudeControl_Multi::get_althold_lean_angle_max() const
{
    // calc maximum tilt angle based on throttle
    float thr_max = _motors_multi.get_throttle_thrust_max();

    // divide by zero check
    if (is_zero(thr_max)) {
        return 0.0f;
    }

    return ToDeg(acos(constrain_float(_throttle_in_filt.get()/(0.9f * thr_max), 0.0f, 1.0f))) * 100.0f;
}

// returns a throttle including compensation for roll/pitch angle
// throttle value should be 0 ~ 1
float AC_AttitudeControl_Multi::get_boosted_throttle(float throttle_in)
{
    if (!_angle_boost_enabled) {
        _angle_boost = 0;
        return throttle_in;
    }
    // inverted_factor is 1 for tilt angles below 60 degrees
    // inverted_factor reduces from 1 to 0 for tilt angles between 60 and 90 degrees

    float cos_tilt = _ahrs.cos_pitch() * _ahrs.cos_roll();
    float inverted_factor = constrain_float(2.0f*cos_tilt, 0.0f, 1.0f);
    float boost_factor = 1.0f/constrain_float(cos_tilt, 0.5f, 1.0f);

    float throttle_out = throttle_in*inverted_factor*boost_factor;
    _angle_boost = constrain_float(throttle_out - throttle_in,-1.0f,1.0f);
    return throttle_out;
}