terrain_estimator.h
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/****************************************************************************
*
* Copyright (c) 2015 Roman Bapst. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* 3. Neither the name PX4 nor the names of its contributors may be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
****************************************************************************/
/**
* @file terrain_estimator.h
*/
#pragma once
#include <lib/mathlib/mathlib.h>
#include <matrix/math.hpp>
#include <uORB/topics/sensor_combined.h>
#include <uORB/topics/vehicle_gps_position.h>
#include <uORB/topics/vehicle_attitude.h>
#include <uORB/topics/distance_sensor.h>
/*
* This class can be used to estimate distance to the ground using a laser range finder.
* It's assumed that the laser points down vertically if the vehicle is in it's neutral pose.
* The predict(...) function will do a state prediciton based on accelerometer inputs. It also
* considers accelerometer bias.
* The measurement_update(...) function does a measurement update based on range finder and gps
* velocity measurements. Both functions should always be called together when there is new
* acceleration data available.
* The is_valid() function provides information whether the estimate is valid.
*/
class __EXPORT TerrainEstimator
{
public:
TerrainEstimator();
~TerrainEstimator() = default;
bool is_valid() {return _terrain_valid;}
float get_distance_to_ground() {return -_x(0);}
float get_velocity() {return _x(1);}
void predict(float dt, const struct vehicle_attitude_s *attitude, const struct sensor_combined_s *sensor,
const struct distance_sensor_s *distance);
void measurement_update(uint64_t time_ref, const struct vehicle_gps_position_s *gps,
const struct distance_sensor_s *distance,
const struct vehicle_attitude_s *attitude);
private:
enum {n_x = 3};
float _distance_last;
bool _terrain_valid;
// kalman filter variables
matrix::Vector<float, n_x> _x; // state: ground distance, velocity, accel bias in z direction
float _u_z; // acceleration in earth z direction
matrix::Matrix<float, 3, 3> _P; // covariance matrix
// timestamps
uint64_t _time_last_distance;
uint64_t _time_last_gps;
/*
struct {
float var_acc_z;
float var_p_z;
float var_p_vz;
float var_lidar;
float var_gps_vz;
} _params;
*/
bool is_distance_valid(float distance);
};