PX4-Autopilot/src/lib/FlightTasks/tasks/Utility/ManualSmoothingZ.cpp

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/**
 * @file ManualSmoothingZ.cpp
 */

#include "ManualSmoothingZ.hpp"
#include "uORB/topics/parameter_update.h"
#include <mathlib/mathlib.h>
#include <float.h>

ManualSmoothingZ::ManualSmoothingZ(const float &vel, const float &stick) :
	_vel(vel), _stick(stick), _vel_sp_prev(vel)
{
	_acc_max_up_h = param_find("MPC_ACC_UP_MAX");
	_acc_max_down_h = param_find("MPC_ACC_DOWN_MAX");
	_jerk_max_h = param_find("MPC_JERK_MAX");

	/* Load the params the very first time */
	setParams();
}

/* in manual altitude control apply acceleration limit based on stick input
 * we consider two states
 * 1.) brake
 * 2.) accelerate */

void
ManualSmoothingZ::smoothVelFromSticks(float &vel_sp, const float dt)
{
	updateParams();
	updateAcceleration(vel_sp, dt);
	velocitySlewRate(vel_sp, dt);
	_vel_sp_prev = vel_sp;
}

void
ManualSmoothingZ::updateParams()
{
	bool updated;
	parameter_update_s param_update;
	orb_check(_parameter_sub, &updated);

	if (updated) {
		orb_copy(ORB_ID(parameter_update), _parameter_sub, &param_update);
		setParams();
	}
}

void
ManualSmoothingZ::setParams()
{
	param_get(_acc_max_up_h, &_acc_max_up);
	param_get(_acc_max_down_h, &_acc_max_down);
	param_get(_jerk_max_h, &_jerk_max);
}

void
ManualSmoothingZ::updateAcceleration(float &vel_sp, const float dt)
{
	/* Check for max acceleration */
	setMaxAcceleration();

	/* check if zero input stick */
	const bool is_current_zero = (fabsf(_stick) <= FLT_EPSILON);

	/* default is acceleration */
	ManualIntentionZ intention = ManualIntentionZ::acceleration;

	/* check zero input stick */
	if (is_current_zero) {
		intention = ManualIntentionZ::brake;
	}

	/*
	 * update intention
	 */
	if ((_intention != ManualIntentionZ::brake) && (intention == ManualIntentionZ::brake)) {

		/* we start with lowest acceleration */
		_acc_state_dependent = _acc_max_down;

		/* reset slew-rate: this ensures that there
		 * is no delay present when user demands to brake
		 */

		_vel_sp_prev = _vel;

	}

	switch (intention) {
	case ManualIntentionZ::brake: {

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

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

			} else {
				_acc_state_dependent = _acc_max_up;
			}

			break;
		}

	case ManualIntentionZ::acceleration: {

			_acc_state_dependent = (getMaxAcceleration() - _acc_max_down)
					       * fabsf(_stick) + _acc_max_down;
			break;
		}
	}

	_intention = intention;
}

void
ManualSmoothingZ::setMaxAcceleration()
{
	/* Note: NED frame */

	if (_stick < -FLT_EPSILON) {
		/* accelerating upward */
		_max_acceleration =  _acc_max_up;

	} else if (_stick > FLT_EPSILON) {
		/* accelerating downward */
		_max_acceleration = _acc_max_down;

	} else {

		/* want to brake */

		if (fabsf(_vel_sp_prev) < FLT_EPSILON) {
			/* at rest */
			_max_acceleration = _acc_max_up;

		} else if (_vel_sp_prev < 0.0f) {
			/* braking downward */
			_max_acceleration = _acc_max_down;

		} else {
			/* braking upward */
			_max_acceleration = _acc_max_up;
		}
	}
}

void
ManualSmoothingZ::velocitySlewRate(float &vel_sp, const float dt)
{
	/* limit vertical acceleration */
	float acc = (vel_sp - _vel_sp_prev) / dt;
	float max_acc = (acc < 0.0f) ? -_acc_state_dependent : _acc_state_dependent;

	if (fabsf(acc) > fabsf(max_acc)) {
		vel_sp = max_acc * dt + _vel_sp_prev;
	}
}