ManualSmoothingXY.cpp

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/**
 * @file ManualSmoothingXY.cpp
 */

#include "ManualSmoothingXY.hpp"
#include <mathlib/mathlib.h>
#include <float.h>
#include <px4_platform_common/defines.h>

using namespace matrix;

ManualSmoothingXY::ManualSmoothingXY(ModuleParams *parent, const Vector2f &vel) :
    ModuleParams(parent),   _vel_sp_prev(vel)

{
    _acc_state_dependent = _param_mpc_acc_hor.get();
    _jerk_state_dependent = _param_mpc_jerk_max.get();
}

void
ManualSmoothingXY::smoothVelocity(Vector2f &vel_sp, const Vector2f &vel, const float &yaw,
                  const float &yawrate_sp, const float dt)
{
    _updateAcceleration(vel_sp, vel, yaw, yawrate_sp, dt);
    _velocitySlewRate(vel_sp, dt);
    _vel_sp_prev = vel_sp;
}

void
ManualSmoothingXY::_updateAcceleration(Vector2f &vel_sp, const Vector2f &vel,  const float &yaw,
                       const float &yawrate_sp, const float dt)
{
    Intention intention = _getIntention(vel_sp, vel, yaw, yawrate_sp);

    // Adapt acceleration and jerk based on current state and
    // intention. Jerk is only used for braking.
    _setStateAcceleration(vel_sp, vel, intention, dt);
}

ManualSmoothingXY::Intention
ManualSmoothingXY::_getIntention(const Vector2f &vel_sp, const Vector2f &vel, const float &yaw,
                 const float &yawrate_sp)
{

    if (vel_sp.length() > FLT_EPSILON) {
        // Distinguish between acceleration, deceleration and direction change

        // Check if stick direction and current velocity are within 135.
        // If current setpoint and velocity are more than 135 apart, we assume
        // that the user demanded a direction change.
        // The detection is done in body frame.
        // Rotate velocity setpoint into body frame
        Vector2f vel_sp_heading = _getWorldToHeadingFrame(vel_sp, yaw);
        Vector2f vel_heading = _getWorldToHeadingFrame(vel, yaw);

        if (vel_sp_heading.length() > FLT_EPSILON) {
            vel_sp_heading.normalize();
        }

        if (vel_heading.length() > FLT_EPSILON) {
            vel_heading.normalize();
        }

        const bool is_aligned = (vel_sp_heading * vel_heading) > -0.707f;

        // In almost all cases we want to use acceleration.
        // Only use direction change if not aligned, no yawspeed demand, demand larger than 0.7 of max speed and velocity larger than 2m/s.
        // Only use deceleration if stick input is lower than previous setpoint, aligned and no yawspeed demand.
        bool yawspeed_demand =  fabsf(yawrate_sp) > 0.05f && PX4_ISFINITE(yawrate_sp);
        bool direction_change = !is_aligned && (vel_sp.length() > 0.7f * _vel_max) && !yawspeed_demand
                    && (vel.length() > 2.0f);
        bool deceleration = is_aligned && (vel_sp.length() < _vel_sp_prev.length()) && !yawspeed_demand;

        if (direction_change) {
            return Intention::direction_change;

        } else if (deceleration) {
            return Intention::deceleration;

        } else {
            return Intention::acceleration;
        }
    }

    return Intention::brake; //default is brake
}

void
ManualSmoothingXY::_setStateAcceleration(const Vector2f &vel_sp, const Vector2f &vel,
        const Intention &intention, const float dt)
{
    switch (intention) {
    case Intention::brake: {

            if (_intention == Intention::direction_change) {
                // Vehicle switched from direction change to brake.
                // Don't do any slwerate and just stop.
                _jerk_state_dependent = 1e6f;
                _vel_sp_prev = vel;

            } else if (intention != _intention) {
                // start the brake with lowest acceleration which
                // makes stopping smoother
                _acc_state_dependent = _param_mpc_dec_hor_slow.get();

                // Adjust jerk based on current velocity. This ensures
                // that the vehicle will stop much quicker at large speed but
                // very slow at low speed.
                _jerk_state_dependent = 1e6f; // default

                if (_param_mpc_jerk_max.get() > _param_mpc_jerk_min.get() && _param_mpc_jerk_min.get() > FLT_EPSILON) {

                    _jerk_state_dependent = math::min((_param_mpc_jerk_max.get() - _param_mpc_jerk_min.get())
                                      / _vel_max * vel.length() + _param_mpc_jerk_min.get(), _param_mpc_jerk_max.get());
                }

                // User wants to brake smoothly but does NOT want the vehicle to
                // continue to fly in the opposite direction. slewrate has to be reset
                // by setting previous velocity setpoint to current velocity. */
                _vel_sp_prev = vel;
            }

            /* limit jerk when braking to zero */
            float jerk = (_param_mpc_acc_hor_max.get() - _acc_state_dependent) / dt;

            if (jerk > _jerk_state_dependent) {
                _acc_state_dependent = _jerk_state_dependent * dt
                               + _acc_state_dependent;

            } else {
                _acc_state_dependent = _param_mpc_acc_hor_max.get();
            }

            break;
        }

    case Intention::direction_change: {
            // We allow for fast change by setting previous setpoint to current  setpoint.


            // Because previous setpoint is equal to current setpoint,
            // slewrate will have no effect. Nonetheless, just set
            // acceleration to maximum.
            _acc_state_dependent = _param_mpc_acc_hor_max.get();
            break;
        }

    case Intention::acceleration: {
            // Limit acceleration linearly based on velocity setpoint.
            _acc_state_dependent = (_param_mpc_acc_hor.get() - _param_mpc_dec_hor_slow.get())
                           / _vel_max * vel_sp.length() + _param_mpc_dec_hor_slow.get();
            break;
        }

    case Intention::deceleration: {
            _acc_state_dependent = _param_mpc_dec_hor_slow.get();
            break;
        }
    }

    // Update intention for next iteration.
    _intention = intention;
}

void
ManualSmoothingXY::_velocitySlewRate(Vector2f &vel_sp, const float dt)
{
    // Adjust velocity setpoint if demand exceeds acceleration. /
    Vector2f acc{};

    if (dt > FLT_EPSILON) {
        acc = (vel_sp - _vel_sp_prev) / dt;
    }

    if (acc.length() > _acc_state_dependent) {
        vel_sp = acc.normalized() * _acc_state_dependent  * dt + _vel_sp_prev;
    }
}

Vector2f
ManualSmoothingXY::_getWorldToHeadingFrame(const Vector2f &vec, const float &yaw)
{
    Quatf q_yaw = AxisAnglef(Vector3f(0.0f, 0.0f, 1.0f), yaw);
    Vector3f vec_heading = q_yaw.conjugate_inversed(Vector3f(vec(0), vec(1), 0.0f));
    return Vector2f(vec_heading);
}

Vector2f
ManualSmoothingXY::_getHeadingToWorldFrame(const Vector2f &vec, const float &yaw)
{
    Quatf q_yaw = AxisAnglef(Vector3f(0.0f, 0.0f, 1.0f), yaw);
    Vector3f vec_world = q_yaw.conjugate(Vector3f(vec(0), vec(1), 0.0f));
    return Vector2f(vec_world);
}