forked from Archive/PX4-Autopilot
275 lines
7.9 KiB
C++
275 lines
7.9 KiB
C++
/****************************************************************************
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*
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* Copyright (c) 2013 Estimation and Control Library (ECL). All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name ECL nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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****************************************************************************/
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/**
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* @file ecl_l1_pos_control.h
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* Implementation of L1 position control.
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*
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*
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* Acknowledgements and References:
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*
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* This implementation has been built for PX4 based on the original
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* publication from [1] and does include a lot of the ideas (not code)
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* from [2].
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*
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*
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* [1] S. Park, J. Deyst, and J. P. How, "A New Nonlinear Guidance Logic for Trajectory Tracking,"
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* Proceedings of the AIAA Guidance, Navigation and Control
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* Conference, Aug 2004. AIAA-2004-4900.
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*
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* [2] Paul Riseborough, Brandon Jones and Andrew Tridgell, L1 control for APM. Aug 2013.
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* - Explicit control over frequency and damping
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* - Explicit control over track capture angle
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* - Ability to use loiter radius smaller than L1 length
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* - Modified to use PD control for circle tracking to enable loiter radius less than L1 length
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* - Modified to enable period and damping of guidance loop to be set explicitly
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* - Modified to provide explicit control over capture angle
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*
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*/
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#ifndef ECL_L1_POS_CONTROLLER_H
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#define ECL_L1_POS_CONTROLLER_H
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#include <mathlib/mathlib.h>
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#include <geo/geo.h>
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#include <ecl/ecl.h>
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/**
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* L1 Nonlinear Guidance Logic
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*/
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class __EXPORT ECL_L1_Pos_Controller
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{
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public:
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ECL_L1_Pos_Controller() :
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_L1_distance(20.0),
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_L1_period(25.0),
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_L1_damping(0.75),
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_L1_ratio(5.0),
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_K_L1(2.0),
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_heading_omega(1.0),
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_roll_lim_rad(math::radians(10.0))
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{
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}
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/**
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* The current target bearing
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*
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* @return bearing angle (-pi..pi, in NED frame)
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*/
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float nav_bearing();
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/**
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* Get lateral acceleration demand.
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*
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* @return Lateral acceleration in m/s^2
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*/
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float nav_lateral_acceleration_demand();
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/**
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* Heading error.
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*
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* The heading error is either compared to the current track
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* or to the tangent of the current loiter radius.
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*/
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float bearing_error();
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/**
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* Bearing from aircraft to current target.
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*
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* @return bearing angle (-pi..pi, in NED frame)
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*/
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float target_bearing();
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/**
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* Get roll angle setpoint for fixed wing.
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*
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* @return Roll angle (in NED frame)
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*/
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float nav_roll();
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/**
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* Get the current crosstrack error.
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*
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* @return Crosstrack error in meters.
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*/
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float crosstrack_error();
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/**
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* Returns true if the loiter waypoint has been reached
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*/
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bool reached_loiter_target();
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/**
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* Returns true if following a circle (loiter)
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*/
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bool circle_mode() {
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return _circle_mode;
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}
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/**
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* Get the switch distance
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*
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* This is the distance at which the system will
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* switch to the next waypoint. This depends on the
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* period and damping
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*
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* @param waypoint_switch_radius The switching radius the waypoint has set.
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*/
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float switch_distance(float waypoint_switch_radius);
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/**
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* Navigate between two waypoints
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*
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* Calling this function with two waypoints results in the
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* control outputs to fly to the line segment defined by
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* the points and once captured following the line segment.
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* This follows the logic in [1].
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*
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* @return sets _lateral_accel setpoint
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*/
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void navigate_waypoints(const math::Vector<2> &vector_A, const math::Vector<2> &vector_B, const math::Vector<2> &vector_curr_position,
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const math::Vector<2> &ground_speed);
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/**
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* Navigate on an orbit around a loiter waypoint.
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*
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* This allow orbits smaller than the L1 length,
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* this modification was introduced in [2].
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*
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* @return sets _lateral_accel setpoint
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*/
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void navigate_loiter(const math::Vector<2> &vector_A, const math::Vector<2> &vector_curr_position, float radius, int8_t loiter_direction,
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const math::Vector<2> &ground_speed_vector);
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/**
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* Navigate on a fixed bearing.
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*
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* This only holds a certain direction and does not perform cross
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* track correction. Helpful for semi-autonomous modes. Introduced
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* by [2].
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*
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* @return sets _lateral_accel setpoint
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*/
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void navigate_heading(float navigation_heading, float current_heading, const math::Vector<2> &ground_speed);
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/**
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* Keep the wings level.
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*
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* This is typically needed for maximum-lift-demand situations,
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* such as takeoff or near stall. Introduced in [2].
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*/
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void navigate_level_flight(float current_heading);
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/**
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* Set the L1 period.
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*/
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void set_l1_period(float period) {
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_L1_period = period;
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/* calculate the ratio introduced in [2] */
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_L1_ratio = 1.0f / M_PI_F * _L1_damping * _L1_period;
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/* calculate normalized frequency for heading tracking */
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_heading_omega = sqrtf(2.0f) * M_PI_F / _L1_period;
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}
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/**
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* Set the L1 damping factor.
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*
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* The original publication recommends a default of sqrt(2) / 2 = 0.707
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*/
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void set_l1_damping(float damping) {
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_L1_damping = damping;
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/* calculate the ratio introduced in [2] */
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_L1_ratio = 1.0f / M_PI_F * _L1_damping * _L1_period;
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/* calculate the L1 gain (following [2]) */
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_K_L1 = 4.0f * _L1_damping * _L1_damping;
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}
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/**
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* Set the maximum roll angle output in radians
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*
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*/
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void set_l1_roll_limit(float roll_lim_rad) {
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_roll_lim_rad = roll_lim_rad;
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}
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private:
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float _lateral_accel; ///< Lateral acceleration setpoint in m/s^2
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float _L1_distance; ///< L1 lead distance, defined by period and damping
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bool _circle_mode; ///< flag for loiter mode
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float _nav_bearing; ///< bearing to L1 reference point
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float _bearing_error; ///< bearing error
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float _crosstrack_error; ///< crosstrack error in meters
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float _target_bearing; ///< the heading setpoint
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float _L1_period; ///< L1 tracking period in seconds
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float _L1_damping; ///< L1 damping ratio
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float _L1_ratio; ///< L1 ratio for navigation
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float _K_L1; ///< L1 control gain for _L1_damping
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float _heading_omega; ///< Normalized frequency
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float _roll_lim_rad; ///<maximum roll angle
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/**
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* Convert a 2D vector from WGS84 to planar coordinates.
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*
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* This converts from latitude and longitude to planar
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* coordinates with (0,0) being at the position of ref and
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* returns a vector in meters towards wp.
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*
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* @param ref The reference position in WGS84 coordinates
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* @param wp The point to convert to into the local coordinates, in WGS84 coordinates
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* @return The vector in meters pointing from the reference position to the coordinates
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*/
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math::Vector<2> get_local_planar_vector(const math::Vector<2> &origin, const math::Vector<2> &target) const;
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};
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#endif /* ECL_L1_POS_CONTROLLER_H */
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