PX4-Autopilot/src/modules/mc_pos_control/PositionControl.cpp

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/**
 * @file PositionControl.cpp
 *
 * This file implements a P-position-control cascaded with a
 * PID-velocity-controller.
 *
 * Inputs: vehicle states (pos, vel, q)
 *         desired setpoints (pos, vel, thrust, yaw)
 * Outputs: thrust and yaw setpoint
 */

#include "PositionControl.hpp"
#include <float.h>
#include <mathlib/mathlib.h>
#include "uORB/topics/parameter_update.h"
#include "Utility/ControlMath.hpp"
#include <lib/ecl/geo/geo.h>  //TODO: only used for wrap_pi -> move this to mathlib since
// it makes more sense

using namespace matrix;

using Data = matrix::Vector3f;

PositionControl::PositionControl()
{
	_Pz_h   = param_find("MPC_Z_P");
	_Pvz_h  = param_find("MPC_Z_VEL_P");
	_Ivz_h  = param_find("MPC_Z_VEL_I");
	_Dvz_h  = param_find("MPC_Z_VEL_D");
	_Pxy_h  = param_find("MPC_XY_P");
	_Pvxy_h = param_find("MPC_XY_VEL_P");
	_Ivxy_h = param_find("MPC_XY_VEL_I");
	_Dvxy_h = param_find("MPC_XY_VEL_D");
	_VelMaxXY = param_find("MPC_XY_VEL_MAX");
	_VelMaxZdown_h = param_find("MPC_Z_VEL_MAX_DN");
	_VelMaxZup_h = param_find("MPC_Z_VEL_MAX_UP");
	_ThrHover_h = param_find("MPC_THR_HOVER");
	_ThrMax_h = param_find("MPC_THR_MAX");
	_ThrMin_h = param_find("MPC_THR_MIN");
	_YawRateMax_h = param_find("MPC_MAN_Y_MAX");
	_Pyaw_h = param_find("MC_YAW_P");

	/* Set parameter the very first time. */
	_setParams();
};

void PositionControl::updateState(const struct vehicle_local_position_s state, const Data &vel_dot,
				  const matrix::Matrix<float, 3, 3> &R)
{
	_pos = Data(&state.x);
	_vel = Data(&state.vx);
	_yaw = state.yaw;
	_vel_dot = vel_dot;
	_R = R;
}

void PositionControl::updateSetpoint(struct vehicle_local_position_setpoint_s setpoint)
{
	_pos_sp = Data(&setpoint.x);
	_vel_sp = Data(&setpoint.vx);
	_acc_sp = Data(&setpoint.acc_x);
	_thr_sp = Data(&setpoint.thr_x);
	_yaw_sp = setpoint.yaw; //integrate
	_yawspeed_sp = setpoint.yawspeed;
	_interfaceMapping();
}

void PositionControl::generateThrustYawSetpoint(const float &dt)
{
	_updateParams();

	/* Only run position/velocity controller
	 * if no altitude thrust is given.
	 */
	if (!PX4_ISFINITE(_thr_sp(2))) {
		_positionController();
		_velocityController(dt);
	}

	_yawController(dt);
}

void PositionControl::_interfaceMapping()
{
	/* Respects FlightTask interface, where
	 * NAN-setpoints are of no interest and
	 * do not require control.
	 */

	/* Loop through x,y and z components of all setpoints. */
	for (int i = 0; i <= 2; i++) {

		if (PX4_ISFINITE(_thr_sp(i))) {

			_pos_sp(i) = _pos(i);
			_vel_sp(i) = _vel(i);
			_acc_sp(i) = _acc(i);
			continue;
		}

		if (PX4_ISFINITE(_pos_sp(i))) {

			/* Position control is required */

			if (!PX4_ISFINITE(_vel_sp(i))) {
				/* Velocity is not used as feedforward term. */
				_vel_sp(i) = 0.0f;
			}

		} else {

			/* Velocity controller is active without
			 * position control.
			 */
			_pos_sp(i) = _pos(i);

			if (!PX4_ISFINITE(_vel_sp(i)))  {
				/* No position/velocity controller active.
				 * Attitude will be generated from sticks directly
				 * TODO: Adjust to the new FlightTask interface
				 * that also sends thrust setpoints.
				 */
				_vel_sp(i) = _vel(i);
			}
		}
	}

	if (!PX4_ISFINITE(_yawspeed_sp)) {

		/* Target yaw is yaw setpoint. No need for yawspeed */
		_yawspeed_sp = 0.0f;

		if (!PX4_ISFINITE(_yaw_sp)) {

			/* There is no finite setpoint. The best
			 * we can do is to just re-use old setpoint */
			_yaw_sp = _yaw_sp_int;
		}

	} else if (!PX4_ISFINITE(_yaw_sp)) {
		/* Nothing is finite: Best we can do is to just
		 * reuse old setpoint.
		 */
		_yaw_sp = _yaw_sp_int;
	}
}

void PositionControl::_positionController()
{
	/* Generate desired velocity setpoint */

	/* P-controller */
	_vel_sp = (_pos_sp - _pos).emult(Pp) + _vel_sp;

	/* Make sure velocity setpoint is constrained in all directions (xyz). */
	float vel_norm_xy = sqrtf(_vel_sp(0) * _vel_sp(0) + _vel_sp(1) * _vel_sp(1));

	if (vel_norm_xy > _VelMaxXY) {
		_vel_sp(0) = _vel_sp(0) * _VelMaxXY / vel_norm_xy;
		_vel_sp(1) = _vel_sp(1) * _VelMaxXY / vel_norm_xy;
	}

	_vel_sp(2) = math::constrain(_vel_sp(2), -_VelMaxZ[0], _VelMaxZ[1]);
}

void PositionControl::_velocityController(const float &dt)
{
	/* Generate desired thrust setpoint */
	/* PID
	 * u_des = P(vel_err) + D(vel_err_dot) + I(vel_integral)
	 * Umin <= u_des <= Umax
	 *
	 * Saturation for vel_integral;
	 * u_des = _thr_sp; r = _vel_sp; y = _vel
	 * u_des >= Umax and r - y >= 0 => Saturation = true
	 * u_des >= Umax and r - y <= 0 => Saturation = false
	 * u_des <= Umin and r - y <= 0 => Saturation = true
	 * u_des <= Umin and r - y >= 0 => Saturation = false
	 *
	 */

	Data vel_err = _vel_sp - _vel;

	/* TODO: add offboard acceleration mode
	 * PID-controller */
	Data offset(0.0f, 0.0f, _ThrHover);
	_thr_sp = Pv.emult(vel_err) + Dv.emult(_vel_dot) + _thr_int - offset;

	/* Limit tilt with priority on z
	 * For manual controlled mode excluding pure manual and rate control, maximum tilt is 90;
	 * It is to note that pure manual and rate control will never enter _velocityController method.
	 * TODO: This needs to be revisited. */
	float tilt_max = PX4_ISFINITE(_constraints.tilt_max) ? _constraints.tilt_max : M_PI_2_F;
	tilt_max = math::min(tilt_max, M_PI_2_F);
	_thr_sp = ControlMath::constrainTilt(_thr_sp, tilt_max);


	/* Constrain thrust set-point and update saturation flag */
	/* To get (r-y) for horizontal direction, we look at the dot-product
	 * for vel_err and _vel_sp. The sign of the dot product indicates
	 * if (r-y) is greater or smaller than 0
	 */
	float dot_xy = matrix::Vector2f(&vel_err(0)) * matrix::Vector2f(&_vel_sp(0));
	float direction[2] = {dot_xy, -vel_err(2)}; // negative sign because of N-E-D
	bool stop_I[2] = {false, false}; // stop integration for xy and z
	ControlMath::constrainPIDu(_thr_sp, stop_I, _ThrLimit, direction);

	/* Update integrals */
	if (!stop_I[0]) {
		_thr_int(0) += vel_err(0) * Iv(0) * dt;
		_thr_int(1) += vel_err(1) * Iv(1) * dt;
	}

	if (!stop_I[1]) {
		_thr_int(2) += vel_err(2) * Iv(2) * dt;
	}


}

void PositionControl::_yawController(const float &dt)
{
	const float yaw_offset_max = math::radians(_YawRateMax) / _Pyaw;
	const float  yaw_target = _wrap_pi(_yaw_sp + _yawspeed_sp * dt);
	const float yaw_offset = _wrap_pi(yaw_target - _yaw);

	// If the yaw offset became too big for the system to track stop
	// shifting it, only allow if it would make the offset smaller again.
	if (fabsf(yaw_offset) < yaw_offset_max || (_yawspeed_sp > 0 && yaw_offset < 0)
	    || (_yawspeed_sp < 0 && yaw_offset > 0)) {
		_yaw_sp = yaw_target;
	}

	/* Update yaw setpoint integral */
	_yaw_sp_int = _yaw_sp;

}

void PositionControl::updateConstraints(const Controller::Constraints &constraints)
{
	_constraints = constraints;
}

void PositionControl::_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 PositionControl::_setParams()
{
	param_get(_Pxy_h, &Pp(0));
	param_get(_Pxy_h, &Pp(1));
	param_get(_Pz_h, &Pp(2));

	param_get(_Pvxy_h, &Pv(0));
	param_get(_Pvxy_h, &Pv(1));
	param_get(_Pvz_h, &Pv(2));

	param_get(_Ivxy_h, &Iv(0));
	param_get(_Ivxy_h, &Iv(1));
	param_get(_Ivz_h, &Iv(2));

	param_get(_Dvxy_h, &Dv(0));
	param_get(_Dvxy_h, &Dv(1));
	param_get(_Dvz_h, &Dv(2));

	param_get(_VelMaxXY_h, &_VelMaxXY);
	param_get(_VelMaxZup_h, &_VelMaxZ[0]);
	param_get(_VelMaxZdown_h, &_VelMaxZ[1]);

	param_get(_ThrHover_h, &_ThrHover);
	param_get(_ThrMax_h, &_ThrLimit[0]);
	param_get(_ThrMin_h, &_ThrLimit[1]);

	param_get(_YawRateMax_h, &_YawRateMax);
	param_get(_Pyaw_h, &_Pyaw);
}