ardupilot/libraries/AC_WPNav/AC_Circle.cpp

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/// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
#include <AP_HAL.h>
#include <AC_Circle.h>
extern const AP_HAL::HAL& hal;
const AP_Param::GroupInfo AC_Circle::var_info[] PROGMEM = {
// @Param: RADIUS
// @DisplayName: Circle Radius
// @Description: Defines the radius of the circle the vehicle will fly when in Circle flight mode
// @Units: cm
// @Range: 0 10000
// @Increment: 100
// @User: Standard
AP_GROUPINFO("RADIUS", 0, AC_Circle, _radius, AC_CIRCLE_RADIUS_DEFAULT),
// @Param: RATE
// @DisplayName: Circle rate
// @Description: Circle mode's turn rate in deg/sec. Positive to turn clockwise, negative for counter clockwise
// @Units: deg/s
// @Range: -90 90
// @Increment: 1
// @User: Standard
AP_GROUPINFO("RATE", 1, AC_Circle, _rate, AC_CIRCLE_RATE_DEFAULT),
AP_GROUPEND
};
// Default constructor.
// Note that the Vector/Matrix constructors already implicitly zero
// their values.
//
AC_Circle::AC_Circle(const AP_InertialNav& inav, const AP_AHRS& ahrs, AC_PosControl& pos_control) :
_inav(inav),
_ahrs(ahrs),
_pos_control(pos_control),
_last_update(0),
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_angle(0)
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{
AP_Param::setup_object_defaults(this, var_info);
}
/// init - initialise circle controller setting center specifically
void AC_Circle::init(const Vector3f& center)
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{
_center = center;
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// To-Do: set target position, angle, etc so that copter begins circle from closest point to stopping point
_pos_control.set_pos_target(_inav.get_position());
// To-Do: set _pos_control speed and accel
// calculate velocities
calc_velocities();
// set start angle from position
init_start_angle(false);
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}
/// init - initialise circle controller setting center using stopping point and projecting out based on the copter's heading
void AC_Circle::init()
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{
Vector3f stopping_point;
// get reasonable stopping point
_pos_control.get_stopping_point_xy(stopping_point);
_pos_control.get_stopping_point_z(stopping_point);
// set circle center to circle_radius ahead of stopping point
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_center.x = stopping_point.x + _radius * _ahrs.cos_yaw();
_center.y = stopping_point.y + _radius * _ahrs.sin_yaw();
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_center.z = stopping_point.z;
// update pos_control target to stopping point
_pos_control.set_pos_target(stopping_point);
// calculate velocities
calc_velocities();
// set starting angle from vehicle heading
init_start_angle(true);
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}
/// update - update circle controller
void AC_Circle::update()
{
// calculate dt
uint32_t now = hal.scheduler->millis();
float dt = (now - _last_update) / 1000.0f;
// update circle position at 10hz
if (dt > 0.095f) {
// double check dt is reasonable
if (dt >= 1.0f) {
dt = 0.0;
}
// capture time since last iteration
_last_update = now;
// ramp up angular velocity to maximum
if (_rate >= 0) {
if (_angular_vel < _angular_vel_max) {
_angular_vel += _angular_accel * dt;
_angular_vel = constrain_float(_angular_vel, 0, _angular_vel_max);
}
}else{
if (_angular_vel > _angular_vel_max) {
_angular_vel += _angular_accel * dt;
_angular_vel = constrain_float(_angular_vel, _angular_vel_max, 0);
}
}
// update the target angle and total angle traveled
float angle_change = _angular_vel * dt;
_angle += angle_change;
_angle = wrap_PI(_angle);
_angle_total += angle_change;
// if the circle_radius is zero we are doing panorama so no need to update loiter target
if (_radius != 0.0) {
// calculate target position
Vector3f target;
target.x = _center.x + _radius * cosf(-_angle);
target.y = _center.y - _radius * sinf(-_angle);
target.z = _pos_control.get_alt_target();
// update position controller target
_pos_control.set_pos_target(target);
// heading is 180 deg from vehicles target position around circle
_yaw = wrap_PI(_angle-PI) * AC_CIRCLE_DEGX100;
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}else{
// set target position to center
Vector3f target;
target.x = _center.x;
target.y = _center.y;
target.z = _pos_control.get_alt_target();
// update position controller target
_pos_control.set_pos_target(target);
// heading is same as _angle but converted to centi-degrees
_yaw = _angle * AC_CIRCLE_DEGX100;
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}
// trigger position controller on next update
_pos_control.trigger_xy();
}
// run loiter's position to velocity step
_pos_control.update_pos_controller(false);
}
// get_closest_point_on_circle - returns closest point on the circle
// circle's center should already have been set
// closest point on the circle will be placed in result
// result's altitude (i.e. z) will be set to the circle_center's altitude
// if vehicle is at the center of the circle, the edge directly behind vehicle will be returned
void AC_Circle::get_closest_point_on_circle(Vector3f &result)
{
// return center if radius is zero
if (_radius <= 0) {
result = _center;
return;
}
// get current position
const Vector3f &curr_pos = _inav.get_position();
// calc vector from current location to circle center
Vector2f vec; // vector from circle center to current location
vec.x = (curr_pos.x - _center.x);
vec.y = (curr_pos.y - _center.y);
float dist = pythagorous2(vec.x, vec.y);
// if current location is exactly at the center of the circle return edge directly behind vehicle
if (dist == 0) {
result.x = _center.x - _radius * _ahrs.cos_yaw();
result.y = _center.y - _radius * _ahrs.sin_yaw();
result.z = _center.z;
return;
}
// calculate closest point on edge of circle
result.x = _center.x + vec.x / dist * _radius;
result.y = _center.y + vec.y / dist * _radius;
result.z = _center.z;
}
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// calc_velocities - calculate angular velocity max and acceleration based on radius and rate
// this should be called whenever the radius or rate are changed
// initialises the yaw and current position around the circle
void AC_Circle::calc_velocities()
{
// if we are doing a panorama set the circle_angle to the current heading
if (_radius <= 0) {
_angular_vel_max = ToRad(_rate);
_angular_accel = _angular_vel_max; // reach maximum yaw velocity in 1 second
}else{
// set starting angle to current heading - 180 degrees
_angle = wrap_PI(_ahrs.yaw-PI);
// calculate max velocity based on waypoint speed ensuring we do not use more than half our max acceleration for accelerating towards the center of the circle
float velocity_max = min(_pos_control.get_speed_xy(), safe_sqrt(0.5f*_pos_control.get_accel_xy()*_radius));
// angular_velocity in radians per second
_angular_vel_max = velocity_max/_radius;
_angular_vel_max = constrain_float(ToRad(_rate),-_angular_vel_max,_angular_vel_max);
// angular_velocity in radians per second
_angular_accel = _pos_control.get_accel_xy()/_radius;
if (_rate < 0.0f) {
_angular_accel = -_angular_accel;
}
}
// initialise angular velocity
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_angular_vel = 0;
}
// init_start_angle - sets the starting angle around the circle and initialises the angle_total
// if use_heading is true the vehicle's heading will be used to init the angle causing minimum yaw movement
// if use_heading is false the vehicle's position from the center will be used to initialise the angle
void AC_Circle::init_start_angle(bool use_heading)
{
// initialise angle total
_angle_total = 0;
// if the radius is zero we are doing panorama so init angle to the current heading
if (_radius <= 0) {
_angle = _ahrs.yaw;
return;
}
// if use_heading is true
if (use_heading) {
_angle = wrap_PI(_ahrs.yaw-PI);
} else {
// if we are exactly at the center of the circle, init angle to directly behind vehicle (so vehicle will backup but not change heading)
const Vector3f &curr_pos = _inav.get_position();
if (curr_pos.x == _center.x && curr_pos.y == _center.y) {
_angle = wrap_PI(_ahrs.yaw-PI);
} else {
// get bearing from circle center to vehicle in radians
float bearing_rad = ToRad(90) + atan2f(-(curr_pos.x-_center.x), curr_pos.y-_center.y);
_angle = wrap_PI(bearing_rad);
}
}
}