PX4-Autopilot/src/modules/rover_ackermann/AckermannRateControl/AckermannRateControl.cpp

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#include "AckermannRateControl.hpp"

using namespace time_literals;

AckermannRateControl::AckermannRateControl(ModuleParams *parent) : ModuleParams(parent)
{
	_rover_steering_setpoint_pub.advertise();
	_rover_rate_status_pub.advertise();
	updateParams();
}

void AckermannRateControl::updateParams()
{
	ModuleParams::updateParams();
	_max_yaw_rate = _param_ro_yaw_rate_limit.get() * M_DEG_TO_RAD_F;

	// Set up PID controller
	_pid_yaw_rate.setGains(_param_ro_yaw_rate_p.get(), _param_ro_yaw_rate_i.get(), 0.f);
	_pid_yaw_rate.setIntegralLimit(1.f);
	_pid_yaw_rate.setOutputLimit(1.f);

	// Set up slew rate
	_adjusted_yaw_rate_setpoint.setSlewRate(_param_ro_yaw_accel_limit.get() * M_DEG_TO_RAD_F);
}

void AckermannRateControl::updateRateControl()
{
	updateSubscriptions();

	hrt_abstime timestamp_prev = _timestamp;
	_timestamp = hrt_absolute_time();
	const float dt = math::constrain(_timestamp - timestamp_prev, 1_ms, 5000_ms) * 1e-6f;

	if (PX4_ISFINITE(_yaw_rate_setpoint)) {
		if (fabsf(_estimated_speed) > FLT_EPSILON) {
			// Set up feasible yaw rate setpoint
			float steering_setpoint{0.f};
			float max_possible_yaw_rate = fabsf(_estimated_speed) * tanf(_param_ra_max_str_ang.get()) /
						      _param_ra_wheel_base.get(); // Maximum possible yaw rate at current velocity
			float yaw_rate_limit = math::min(max_possible_yaw_rate, _max_yaw_rate);
			float constrained_yaw_rate = math::constrain(_yaw_rate_setpoint, -yaw_rate_limit, yaw_rate_limit);

			if (_param_ro_yaw_accel_limit.get() > FLT_EPSILON) { // Apply slew rate if configured
				if (fabsf(_adjusted_yaw_rate_setpoint.getState() - _vehicle_yaw_rate) > fabsf(constrained_yaw_rate -
						_vehicle_yaw_rate)) {
					_adjusted_yaw_rate_setpoint.setForcedValue(_vehicle_yaw_rate);
				}

				_adjusted_yaw_rate_setpoint.update(constrained_yaw_rate, dt);

			} else {
				_adjusted_yaw_rate_setpoint.setForcedValue(constrained_yaw_rate);
			}

			// Feed forward
			steering_setpoint = atanf(_adjusted_yaw_rate_setpoint.getState() * _param_ra_wheel_base.get() / _estimated_speed);

			// Feedback (Only when driving forwards because backwards driving is NMP and can introduce instability)
			if (_estimated_speed > FLT_EPSILON) {
				_pid_yaw_rate.setSetpoint(_adjusted_yaw_rate_setpoint.getState());
				steering_setpoint += _pid_yaw_rate.update(_vehicle_yaw_rate, dt);
			}

			rover_steering_setpoint_s rover_steering_setpoint{};
			rover_steering_setpoint.timestamp = _timestamp;
			rover_steering_setpoint.normalized_steering_angle = math::interpolate<float>(steering_setpoint,
					-_param_ra_max_str_ang.get(), _param_ra_max_str_ang.get(), -1.f, 1.f); // Normalize steering setpoint
			_rover_steering_setpoint_pub.publish(rover_steering_setpoint);

		} else {
			_pid_yaw_rate.resetIntegral();
			rover_steering_setpoint_s rover_steering_setpoint{};
			rover_steering_setpoint.timestamp = _timestamp;
			rover_steering_setpoint.normalized_steering_angle = 0.f;
			_rover_steering_setpoint_pub.publish(rover_steering_setpoint);
		}
	}


	// Publish rate controller status (logging only)
	rover_rate_status_s rover_rate_status;
	rover_rate_status.timestamp = _timestamp;
	rover_rate_status.measured_yaw_rate = _vehicle_yaw_rate;
	rover_rate_status.adjusted_yaw_rate_setpoint = _adjusted_yaw_rate_setpoint.getState();
	rover_rate_status.pid_yaw_rate_integral = _pid_yaw_rate.getIntegral();
	_rover_rate_status_pub.publish(rover_rate_status);

}

void AckermannRateControl::updateSubscriptions()
{
	if (_vehicle_angular_velocity_sub.updated()) {
		vehicle_angular_velocity_s vehicle_angular_velocity{};
		_vehicle_angular_velocity_sub.copy(&vehicle_angular_velocity);
		_vehicle_yaw_rate = fabsf(vehicle_angular_velocity.xyz[2]) > _param_ro_yaw_rate_th.get() * M_DEG_TO_RAD_F ?
				    vehicle_angular_velocity.xyz[2] : 0.f;
	}

	// Estimate forward speed based on throttle
	if (_actuator_motors_sub.updated()) {
		actuator_motors_s actuator_motors;
		_actuator_motors_sub.copy(&actuator_motors);
		_estimated_speed = math::interpolate<float>(actuator_motors.control[0], -1.f, 1.f,
				   -_param_ro_max_thr_speed.get(), _param_ro_max_thr_speed.get());
		_estimated_speed = fabsf(_estimated_speed) >  _param_ro_speed_th.get() ? _estimated_speed : 0.f;
	}

	if (_rover_rate_setpoint_sub.updated()) {
		rover_rate_setpoint_s rover_rate_setpoint{};
		_rover_rate_setpoint_sub.copy(&rover_rate_setpoint);
		_yaw_rate_setpoint = rover_rate_setpoint.yaw_rate_setpoint;
	}
}

bool AckermannRateControl::runSanityChecks()
{
	bool ret = true;

	if (_param_ro_max_thr_speed.get() < FLT_EPSILON) {
		ret = false;
		events::send<float>(events::ID("ackermann_rate_control_conf_invalid_max_thr_speed"), events::Log::Error,
				    "Invalid configuration of necessary parameter RO_MAX_THR_SPEED", _param_ro_max_thr_speed.get());

	}

	if (_param_ra_wheel_base.get() < FLT_EPSILON) {
		ret = false;
		events::send<float>(events::ID("ackermann_rate_control_conf_invalid_wheel_base"), events::Log::Error,
				    "Invalid configuration of necessary parameter RA_WHEEL_BASE", _param_ra_wheel_base.get());

	}

	if (_param_ra_max_str_ang.get() < FLT_EPSILON) {
		ret = false;
		events::send<float>(events::ID("ackermann_rate_control_conf_invalid_max_str_ang"), events::Log::Error,
				    "Invalid configuration of necessary parameter RA_MAX_STR_ANG", _param_ra_max_str_ang.get());

	}

	if (_param_ro_yaw_rate_limit.get() < FLT_EPSILON) {
		ret = false;
		events::send<float>(events::ID("ackermann_rate_control_conf_invalid_yaw_rate_lim"), events::Log::Error,
				    "Invalid configuration of necessary parameter RO_YAW_RATE_LIM", _param_ro_yaw_rate_limit.get());

	}

	return ret;
}