follow_target.h

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/**
 * @file followme.cpp
 *
 * Helper class to track and follow a given position
 *
 * @author Jimmy Johnson <catch22@fastmail.net>
 */

#pragma once

#include "navigator_mode.h"
#include "mission_block.h"

#include <mathlib/mathlib.h>
#include <matrix/math.hpp>

#include <px4_platform_common/module_params.h>
#include <uORB/Subscription.hpp>
#include <uORB/topics/follow_target.h>

class FollowTarget : public MissionBlock, public ModuleParams
{

public:
    FollowTarget(Navigator *navigator);
    ~FollowTarget() = default;

    void on_inactive() override;
    void on_activation() override;
    void on_active() override;

private:

    static constexpr int TARGET_TIMEOUT_MS = 2500;
    static constexpr int TARGET_ACCEPTANCE_RADIUS_M = 5;
    static constexpr int INTERPOLATION_PNTS = 20;
    static constexpr float FF_K = .25F;
    static constexpr float OFFSET_M = 8;

    enum FollowTargetState {
        TRACK_POSITION,
        TRACK_VELOCITY,
        SET_WAIT_FOR_TARGET_POSITION,
        WAIT_FOR_TARGET_POSITION
    };

    enum {
        FOLLOW_FROM_RIGHT,
        FOLLOW_FROM_BEHIND,
        FOLLOW_FROM_FRONT,
        FOLLOW_FROM_LEFT
    };

    static constexpr float _follow_position_matricies[4][9] = {
        { 1.0F, -1.0F, 0.0F,  1.0F,  1.0F, 0.0F, 0.0F, 0.0F, 1.0F}, // follow right
        {-1.0F,  0.0F, 0.0F,  0.0F, -1.0F, 0.0F, 0.0F, 0.0F, 1.0F}, // follow behind
        { 1.0F,  0.0F, 0.0F,  0.0F,  1.0F, 0.0F, 0.0F, 0.0F, 1.0F}, // follow front
        { 1.0F,  1.0F, 0.0F, -1.0F,  1.0F, 0.0F, 0.0F, 0.0F, 1.0F}  // follow left side
    };

    DEFINE_PARAMETERS(
        (ParamFloat<px4::params::NAV_MIN_FT_HT>) _param_nav_min_ft_ht,
        (ParamFloat<px4::params::NAV_FT_DST>) _param_nav_ft_dst,
        (ParamInt<px4::params::NAV_FT_FS>) _param_nav_ft_fs,
        (ParamFloat<px4::params::NAV_FT_RS>) _param_nav_ft_rs
    )

    FollowTargetState _follow_target_state{SET_WAIT_FOR_TARGET_POSITION};
    int _follow_target_position{FOLLOW_FROM_BEHIND};

    uORB::Subscription _follow_target_sub{ORB_ID(follow_target)};
    float _step_time_in_ms{0.0f};
    float _follow_offset{OFFSET_M};

    uint64_t _target_updates{0};
    uint64_t _last_update_time{0};

    matrix::Vector3f _current_vel;
    matrix::Vector3f _step_vel;
    matrix::Vector3f _est_target_vel;
    matrix::Vector3f _target_distance;
    matrix::Vector3f _target_position_offset;
    matrix::Vector3f _target_position_delta;
    matrix::Vector3f _filtered_target_position_delta;

    follow_target_s _current_target_motion{};
    follow_target_s _previous_target_motion{};

    float _yaw_rate{0.0f};
    float _responsiveness{0.0f};
    float _yaw_angle{0.0f};

    // Mavlink defined motion reporting capabilities
    enum {
        POS = 0,
        VEL = 1,
        ACCEL = 2,
        ATT_RATES = 3
    };

    matrix::Dcmf _rot_matrix;

    void track_target_position();
    void track_target_velocity();
    bool target_velocity_valid();
    bool target_position_valid();
    void reset_target_validity();
    void update_position_sp(bool velocity_valid, bool position_valid, float yaw_rate);
    void update_target_motion();
    void update_target_velocity();

    /**
     * Set follow_target item
     */
    void set_follow_target_item(struct mission_item_s *item, float min_clearance, follow_target_s &target, float yaw);
};