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ardupilot/libraries/AP_Follow/AP_Follow.cpp

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/*
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <AP_HAL/AP_HAL.h>
#include "AP_Follow.h"
#include <ctype.h>
#include <stdio.h>
#include <AP_AHRS/AP_AHRS.h>
#include <AP_Logger/AP_Logger.h>
extern const AP_HAL::HAL& hal;
#define AP_FOLLOW_TIMEOUT_MS 3000 // position estimate timeout after 1 second
#define AP_FOLLOW_SYSID_TIMEOUT_MS 10000 // forget sysid we are following if we haave not heard from them in 10 seconds
#define AP_FOLLOW_OFFSET_TYPE_NED 0 // offsets are in north-east-down frame
#define AP_FOLLOW_OFFSET_TYPE_RELATIVE 1 // offsets are relative to lead vehicle's heading
#define AP_FOLLOW_ALTITUDE_TYPE_RELATIVE 1 // relative altitude is used by default
#define AP_FOLLOW_POS_P_DEFAULT 0.1f // position error gain default
// table of user settable parameters
const AP_Param::GroupInfo AP_Follow::var_info[] = {
// @Param: _ENABLE
// @DisplayName: Follow enable/disable
// @Description: Enabled/disable following a target
// @Values: 0:Disabled,1:Enabled
// @User: Standard
AP_GROUPINFO_FLAGS("_ENABLE", 1, AP_Follow, _enabled, 0, AP_PARAM_FLAG_ENABLE),
// 2 is reserved for TYPE parameter
// @Param: _SYSID
// @DisplayName: Follow target's mavlink system id
// @Description: Follow target's mavlink system id
// @Range: 0 255
// @User: Standard
AP_GROUPINFO("_SYSID", 3, AP_Follow, _sysid, 0),
// 4 is reserved for MARGIN parameter
// @Param: _DIST_MAX
// @DisplayName: Follow distance maximum
// @Description: Follow distance maximum. targets further than this will be ignored
// @Units: m
// @Range: 1 1000
// @User: Standard
AP_GROUPINFO("_DIST_MAX", 5, AP_Follow, _dist_max, 100),
// @Param: _OFS_TYPE
// @DisplayName: Follow offset type
// @Description: Follow offset type
// @Values: 0:North-East-Down, 1:Relative to lead vehicle heading
// @User: Standard
AP_GROUPINFO("_OFS_TYPE", 6, AP_Follow, _offset_type, AP_FOLLOW_OFFSET_TYPE_NED),
// @Param: _OFS_X
// @DisplayName: Follow offsets in meters north/forward
// @Description: Follow offsets in meters north/forward. If positive, this vehicle fly ahead or north of lead vehicle. Depends on FOLL_OFS_TYPE
// @Range: -100 100
// @Units: m
// @Increment: 1
// @User: Standard
// @Param: _OFS_Y
// @DisplayName: Follow offsets in meters east/right
// @Description: Follow offsets in meters east/right. If positive, this vehicle will fly to the right or east of lead vehicle. Depends on FOLL_OFS_TYPE
// @Range: -100 100
// @Units: m
// @Increment: 1
// @User: Standard
// @Param: _OFS_Z
// @DisplayName: Follow offsets in meters down
// @Description: Follow offsets in meters down. If positive, this vehicle will fly below the lead vehicle
// @Range: -100 100
// @Units: m
// @Increment: 1
// @User: Standard
AP_GROUPINFO("_OFS", 7, AP_Follow, _offset, 0),
#if !(APM_BUILD_TYPE(APM_BUILD_Rover))
// @Param: _YAW_BEHAVE
// @DisplayName: Follow yaw behaviour
// @Description: Follow yaw behaviour
// @Values: 0:None,1:Face Lead Vehicle,2:Same as Lead vehicle,3:Direction of Flight
// @User: Standard
AP_GROUPINFO("_YAW_BEHAVE", 8, AP_Follow, _yaw_behave, 1),
#endif
// @Param: _POS_P
// @DisplayName: Follow position error P gain
// @Description: Follow position error P gain. Converts the difference between desired vertical speed and actual speed into a desired acceleration that is passed to the throttle acceleration controller
// @Range: 0.01 1.00
// @Increment: 0.01
// @User: Standard
AP_SUBGROUPINFO(_p_pos, "_POS_", 9, AP_Follow, AC_P),
#if !(APM_BUILD_TYPE(APM_BUILD_Rover))
// @Param: _ALT_TYPE
// @DisplayName: Follow altitude type
// @Description: Follow altitude type
// @Values: 0:absolute, 1:relative
// @User: Standard
AP_GROUPINFO("_ALT_TYPE", 10, AP_Follow, _alt_type, AP_FOLLOW_ALTITUDE_TYPE_RELATIVE),
#endif
AP_GROUPEND
};
/*
The constructor also initialises the proximity sensor. Note that this
constructor is not called until detect() returns true, so we
already know that we should setup the proximity sensor
*/
AP_Follow::AP_Follow() :
_p_pos(AP_FOLLOW_POS_P_DEFAULT)
{
AP_Param::setup_object_defaults(this, var_info);
}
// restore offsets to zero if necessary, should be called when vehicle exits follow mode
void AP_Follow::clear_offsets_if_required()
{
if (_offsets_were_zero) {
_offset = Vector3f();
}
_offsets_were_zero = false;
}
// get target's estimated location
bool AP_Follow::get_target_location_and_velocity(Location &loc, Vector3f &vel_ned) const
{
// exit immediately if not enabled
if (!_enabled) {
return false;
}
// check for timeout
if ((_last_location_update_ms == 0) || (AP_HAL::millis() - _last_location_update_ms > AP_FOLLOW_TIMEOUT_MS)) {
return false;
}
// calculate time since last actual position update
const float dt = (AP_HAL::millis() - _last_location_update_ms) * 0.001f;
// get velocity estimate
if (!get_velocity_ned(vel_ned, dt)) {
return false;
}
// project the vehicle position
Location last_loc = _target_location;
last_loc.offset(vel_ned.x * dt, vel_ned.y * dt);
last_loc.alt -= vel_ned.z * 100.0f * dt; // convert m/s to cm/s, multiply by dt. minus because NED
// return latest position estimate
loc = last_loc;
return true;
}
// get distance vector to target (in meters) and target's velocity all in NED frame
bool AP_Follow::get_target_dist_and_vel_ned(Vector3f &dist_ned, Vector3f &dist_with_offs, Vector3f &vel_ned)
{
// get our location
Location current_loc;
if (!AP::ahrs().get_position(current_loc)) {
clear_dist_and_bearing_to_target();
return false;
}
// get target location and velocity
Location target_loc;
Vector3f veh_vel;
if (!get_target_location_and_velocity(target_loc, veh_vel)) {
clear_dist_and_bearing_to_target();
return false;
}
// change to altitude above home if relative altitude is being used
if (target_loc.relative_alt == 1) {
current_loc.alt -= AP::ahrs().get_home().alt;
}
// calculate difference
const Vector3f dist_vec = current_loc.get_distance_NED(target_loc);
// fail if too far
if (is_positive(_dist_max.get()) && (dist_vec.length() > _dist_max)) {
clear_dist_and_bearing_to_target();
return false;
}
// initialise offsets from distance vector if required
init_offsets_if_required(dist_vec);
// get offsets
Vector3f offsets;
if (!get_offsets_ned(offsets)) {
clear_dist_and_bearing_to_target();
return false;
}
// calculate results
dist_ned = dist_vec;
dist_with_offs = dist_vec + offsets;
vel_ned = veh_vel;
// record distance and heading for reporting purposes
if (is_zero(dist_with_offs.x) && is_zero(dist_with_offs.y)) {
clear_dist_and_bearing_to_target();
} else {
_dist_to_target = safe_sqrt(sq(dist_with_offs.x) + sq(dist_with_offs.y));
_bearing_to_target = degrees(atan2f(dist_with_offs.y, dist_with_offs.x));
}
return true;
}
// get target's heading in degrees (0 = north, 90 = east)
bool AP_Follow::get_target_heading_deg(float &heading) const
{
// exit immediately if not enabled
if (!_enabled) {
return false;
}
// check for timeout
if ((_last_heading_update_ms == 0) || (AP_HAL::millis() - _last_heading_update_ms > AP_FOLLOW_TIMEOUT_MS)) {
return false;
}
// return latest heading estimate
heading = _target_heading;
return true;
}
// handle mavlink DISTANCE_SENSOR messages
void AP_Follow::handle_msg(const mavlink_message_t &msg)
{
// exit immediately if not enabled
if (!_enabled) {
return;
}
// skip our own messages
if (msg.sysid == mavlink_system.sysid) {
return;
}
// skip message if not from our target
if (_sysid != 0 && msg.sysid != _sysid) {
if (_automatic_sysid) {
// maybe timeout who we were following...
if ((_last_location_update_ms == 0) || (AP_HAL::millis() - _last_location_update_ms > AP_FOLLOW_SYSID_TIMEOUT_MS)) {
_sysid.set(0);
}
}
return;
}
// decode global-position-int message
if (msg.msgid == MAVLINK_MSG_ID_GLOBAL_POSITION_INT) {
// get estimated location and velocity (for logging)
Location loc_estimate{};
Vector3f vel_estimate;
UNUSED_RESULT(get_target_location_and_velocity(loc_estimate, vel_estimate));
// decode message
mavlink_global_position_int_t packet;
mavlink_msg_global_position_int_decode(&msg, &packet);
// ignore message if lat and lon are (exactly) zero
if ((packet.lat == 0 && packet.lon == 0)) {
return;
}
_target_location.lat = packet.lat;
_target_location.lng = packet.lon;
// select altitude source based on FOLL_ALT_TYPE param
if (_alt_type == AP_FOLLOW_ALTITUDE_TYPE_RELATIVE) {
// relative altitude
_target_location.alt = packet.relative_alt / 10; // convert millimeters to cm
_target_location.relative_alt = 1; // set relative_alt flag
} else {
// absolute altitude
_target_location.alt = packet.alt / 10; // convert millimeters to cm
_target_location.relative_alt = 0; // reset relative_alt flag
}
_target_velocity_ned.x = packet.vx * 0.01f; // velocity north
_target_velocity_ned.y = packet.vy * 0.01f; // velocity east
_target_velocity_ned.z = packet.vz * 0.01f; // velocity down
// get a local timestamp with correction for transport jitter
_last_location_update_ms = _jitter.correct_offboard_timestamp_msec(packet.time_boot_ms, AP_HAL::millis());
if (packet.hdg <= 36000) { // heading (UINT16_MAX if unknown)
_target_heading = packet.hdg * 0.01f; // convert centi-degrees to degrees
_last_heading_update_ms = _last_location_update_ms;
}
// initialise _sysid if zero to sender's id
if (_sysid == 0) {
_sysid.set(msg.sysid);
_automatic_sysid = true;
}
// log lead's estimated vs reported position
// @LoggerMessage: FOLL
// @Description: Follow library diagnostic data
// @Field: TimeUS: Time since system startup
// @Field: Lat: Target latitude
// @Field: Lon: Target longitude
// @Field: Alt: Target absolute altitude
// @Field: VelN: Target earth-frame velocity, North
// @Field: VelE: Target earth-frame velocity, East
// @Field: VelD: Target earth-frame velocity, Down
// @Field: LatE: Vehicle latitude
// @Field: LonE: Vehicle longitude
// @Field: AltE: Vehicle absolute altitude
AP::logger().WriteStreaming("FOLL",
"TimeUS,Lat,Lon,Alt,VelN,VelE,VelD,LatE,LonE,AltE", // labels
"sDUmnnnDUm", // units
"F--B000--B", // mults
"QLLifffLLi", // fmt
AP_HAL::micros64(),
_target_location.lat,
_target_location.lng,
_target_location.alt,
(double)_target_velocity_ned.x,
(double)_target_velocity_ned.y,
(double)_target_velocity_ned.z,
loc_estimate.lat,
loc_estimate.lng,
loc_estimate.alt
);
}
}
// get velocity estimate in m/s in NED frame using dt since last update
bool AP_Follow::get_velocity_ned(Vector3f &vel_ned, float dt) const
{
vel_ned = _target_velocity_ned + (_target_accel_ned * dt);
return true;
}
// initialise offsets to provided distance vector to other vehicle (in meters in NED frame) if required
void AP_Follow::init_offsets_if_required(const Vector3f &dist_vec_ned)
{
// return immediately if offsets have already been set
if (!_offset.get().is_zero()) {
return;
}
_offsets_were_zero = true;
float target_heading_deg;
if ((_offset_type == AP_FOLLOW_OFFSET_TYPE_RELATIVE) && get_target_heading_deg(target_heading_deg)) {
// rotate offsets from north facing to vehicle's perspective
_offset = rotate_vector(-dist_vec_ned, -target_heading_deg);
gcs().send_text(MAV_SEVERITY_INFO, "Relative follow offset loaded");
} else {
// initialise offset in NED frame
_offset = -dist_vec_ned;
// ensure offset_type used matches frame of offsets saved
_offset_type = AP_FOLLOW_OFFSET_TYPE_NED;
gcs().send_text(MAV_SEVERITY_INFO, "N-E-D follow offset loaded");
}
}
// get offsets in meters in NED frame
bool AP_Follow::get_offsets_ned(Vector3f &offset) const
{
const Vector3f &off = _offset.get();
// if offsets are zero or type is NED, simply return offset vector
if (off.is_zero() || (_offset_type == AP_FOLLOW_OFFSET_TYPE_NED)) {
offset = off;
return true;
}
// offset type is relative, exit if we cannot get vehicle's heading
float target_heading_deg;
if (!get_target_heading_deg(target_heading_deg)) {
return false;
}
// rotate offsets from vehicle's perspective to NED
offset = rotate_vector(off, target_heading_deg);
return true;
}
// rotate 3D vector clockwise by specified angle (in degrees)
Vector3f AP_Follow::rotate_vector(const Vector3f &vec, float angle_deg) const
{
// rotate roll, pitch input from north facing to vehicle's perspective
const float cos_yaw = cosf(radians(angle_deg));
const float sin_yaw = sinf(radians(angle_deg));
return Vector3f((vec.x * cos_yaw) - (vec.y * sin_yaw), (vec.y * cos_yaw) + (vec.x * sin_yaw), vec.z);
}
// set recorded distance and bearing to target to zero
void AP_Follow::clear_dist_and_bearing_to_target()
{
_dist_to_target = 0.0f;
_bearing_to_target = 0.0f;
}
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