ardupilot/ArduSub/mode_althold.cpp

#include "Sub.h"


bool ModeAlthold::init(bool ignore_checks) {
    if(!sub.control_check_barometer()) {
        return false;
    }

    // initialize vertical maximum speeds and acceleration
    // sets the maximum speed up and down returned by position controller
    // All limits must be positive
    position_control->D_set_max_speed_accel_cm(sub.get_pilot_speed_dn(), g.pilot_speed_up, g.pilot_accel_z);
    position_control->D_set_correction_speed_accel_cm(sub.get_pilot_speed_dn(), g.pilot_speed_up, g.pilot_accel_z);

    // initialise position and desired velocity
    position_control->D_init_controller();

    sub.last_pilot_heading_rad = ahrs.get_yaw_rad();

    return true;
}

// althold_run - runs the althold controller
// should be called at 100hz or more
void ModeAlthold::run()
{
    run_pre();
    control_depth();
    run_post();
}

void ModeAlthold::run_pre()
{
    uint32_t tnow = AP_HAL::millis();

    // initialize vertical speeds and acceleration
    // All limits must be positive
    position_control->D_set_max_speed_accel_cm(sub.get_pilot_speed_dn(), g.pilot_speed_up, g.pilot_accel_z);

    if (!motors.armed()) {
        motors.set_desired_spool_state(AP_Motors::DesiredSpoolState::GROUND_IDLE);
        // Sub vehicles do not stabilize roll/pitch/yaw when not auto-armed (i.e. on the ground, pilot has never raised throttle)
        attitude_control->set_throttle_out(NEUTRAL_THROTTLE,true,g.throttle_filt);
        attitude_control->relax_attitude_controllers();
        position_control->D_relax_controller(motors.get_throttle_hover());
        sub.last_pilot_heading_rad = ahrs.get_yaw_rad();
        return;
    }

    motors.set_desired_spool_state(AP_Motors::DesiredSpoolState::THROTTLE_UNLIMITED);

    // get pilot desired lean angles
    float target_roll, target_pitch;

    // Check if set_attitude_target_no_gps is valid
    if (tnow - sub.set_attitude_target_no_gps.last_message_ms < 5000) {
        float target_yaw;
        Quaternion(
            sub.set_attitude_target_no_gps.packet.q
        ).to_euler(
            target_roll,
            target_pitch,
            target_yaw
        );
        target_roll = degrees(target_roll);
        target_pitch = degrees(target_pitch);
        target_yaw = degrees(target_yaw);

        attitude_control->input_euler_angle_roll_pitch_yaw_cd(target_roll * 1e2f, target_pitch * 1e2f, target_yaw * 1e2f, true);
        return;
    }

    sub.get_pilot_desired_lean_angles(channel_roll->get_control_in(), channel_pitch->get_control_in(), target_roll, target_pitch, attitude_control->get_althold_lean_angle_max_cd());

    // get pilot's desired yaw rate
    float yaw_input = channel_yaw->pwm_to_angle_dz_trim(channel_yaw->get_dead_zone() * sub.gain, channel_yaw->get_radio_trim());
    float target_yaw_rate = sub.get_pilot_desired_yaw_rate(yaw_input);

    // call attitude controller
    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_cd(target_roll, target_pitch, target_yaw_rate);
        sub.last_pilot_heading_rad = ahrs.get_yaw_rad();
        sub.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 < sub.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_cd(target_roll, target_pitch, target_yaw_rate);
            sub.last_pilot_heading_rad = ahrs.get_yaw_rad(); // update heading to hold

        } else { // call attitude controller holding absolute bearing
            attitude_control->input_euler_angle_roll_pitch_yaw_cd(target_roll, target_pitch, rad_to_cd(sub.last_pilot_heading_rad), true);
        }
    }
}

void ModeAlthold::run_post()
{
    motors.set_forward(channel_forward->norm_input());
    motors.set_lateral(channel_lateral->norm_input());
}

void ModeAlthold::control_depth() {
    // return 0.2f when at the surface to p
    // scale linearly between 0.2f and 1.0f as we approach the surface
    float distance_to_surface = (g.surface_depth - inertial_nav.get_position_z_up_cm()) * 0.01f;
    distance_to_surface = constrain_float(distance_to_surface, 0.0f, 1.0f);
    motors.set_max_throttle(g.surface_max_throttle + (1.0f - g.surface_max_throttle) * distance_to_surface);

    float target_climb_rate_cms = sub.get_pilot_desired_climb_rate(channel_throttle->get_control_in());
    target_climb_rate_cms = constrain_float(target_climb_rate_cms, -sub.get_pilot_speed_dn(), g.pilot_speed_up);

    // desired_climb_rate returns 0 when within the deadzone.
    //we allow full control to the pilot, but as soon as there's no input, we handle being at surface/bottom
    if (fabsf(target_climb_rate_cms) < 0.05f)  {
        if (sub.ap.at_surface) {
            position_control->set_pos_desired_U_cm(MIN(position_control->get_pos_desired_U_cm(), g.surface_depth)); // set target to 5 cm below surface level
        } else if (sub.ap.at_bottom) {
            position_control->set_pos_desired_U_cm(MAX(inertial_nav.get_position_z_up_cm() + 10.0f, position_control->get_pos_desired_U_cm())); // set target to 10 cm above bottom
        }
    }

    position_control->D_set_pos_target_from_climb_rate_cms(target_climb_rate_cms);
    position_control->D_update_controller();
}