ardupilot/ArduSub/control_stabilize.cpp

#include "Sub.h"

// stabilize_init - initialise stabilize controller
bool Sub::stabilize_init()
{
    // set target altitude to zero for reporting
    pos_control.set_alt_target(0);
    last_pilot_heading = ahrs.yaw_sensor;

    return true;
}

// stabilize_run - runs the main stabilize controller
// should be called at 100hz or more
void Sub::stabilize_run()
{
    uint32_t tnow = AP_HAL::millis();
    float target_roll, target_pitch;
    float target_yaw_rate;

    // if not armed set throttle to zero and exit immediately
    if (!motors.armed()) {
        motors.set_desired_spool_state(AP_Motors::DESIRED_SPIN_WHEN_ARMED);
        attitude_control.set_throttle_out_unstabilized(0,true,g.throttle_filt);
        last_pilot_heading = ahrs.yaw_sensor;
        return;
    }

    motors.set_desired_spool_state(AP_Motors::DESIRED_THROTTLE_UNLIMITED);

    // convert pilot input to lean angles
    // To-Do: convert get_pilot_desired_lean_angles to return angles as floats
    get_pilot_desired_lean_angles(channel_roll->get_control_in(), channel_pitch->get_control_in(), target_roll, target_pitch, aparm.angle_max);

    // get pilot's desired yaw rate
    target_yaw_rate = get_pilot_desired_yaw_rate(channel_yaw->get_control_in());

    // call attitude controller
    // update attitude controller targets

    if (!is_zero(target_yaw_rate)) { // call attitude controller with rate yaw determined by pilot input
        attitude_control.input_euler_angle_roll_pitch_euler_rate_yaw(target_roll, target_pitch, target_yaw_rate);
        last_pilot_heading = ahrs.yaw_sensor;
        last_pilot_yaw_input_ms = tnow; // time when pilot last changed heading

    } else { // hold current heading

        // this check is required to prevent bounce back after very fast yaw maneuvers
        // the inertia of the vehicle causes the heading to move slightly past the point when pilot input actually stopped
        if (tnow < last_pilot_yaw_input_ms + 250) { // give 250ms to slow down, then set target heading
            target_yaw_rate = 0;  // Stop rotation on yaw axis

            // call attitude controller with target yaw rate = 0 to decelerate on yaw axis
            attitude_control.input_euler_angle_roll_pitch_euler_rate_yaw(target_roll, target_pitch, target_yaw_rate);
            last_pilot_heading = ahrs.yaw_sensor; // update heading to hold

        } else { // call attitude controller holding absolute absolute bearing
            attitude_control.input_euler_angle_roll_pitch_yaw(target_roll, target_pitch, last_pilot_heading, true);
        }
    }

    // output pilot's throttle
    attitude_control.set_throttle_out(channel_throttle->norm_input(), false, g.throttle_filt);

    //control_in is range -1000-1000
    //radio_in is raw pwm value
    motors.set_forward(channel_forward->norm_input());
    motors.set_lateral(channel_lateral->norm_input());
}