PX4-Autopilot/src/modules/sih/sih.cpp

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/**
 * @file sih.cpp
 * Simulator in Hardware
 *
 * @author Romain Chiappinelli      <romain.chiap@gmail.com>
 *
 * Coriolis g Corporation - January 2019
 */

#include "aero.hpp"
#include "sih.hpp"

#include <px4_platform_common/getopt.h>
#include <px4_platform_common/log.h>

#include <drivers/drv_pwm_output.h>         // to get PWM flags
#include <lib/drivers/device/Device.hpp>

using namespace math;
using namespace matrix;
using namespace time_literals;

Sih::Sih() :
	ModuleParams(nullptr),
	ScheduledWorkItem(MODULE_NAME, px4::wq_configurations::rate_ctrl)
{
	_px4_accel.set_temperature(T1_C);
	_px4_gyro.set_temperature(T1_C);
	_px4_mag.set_temperature(T1_C);

	parameters_updated();
	init_variables();
	gps_no_fix();

	const hrt_abstime task_start = hrt_absolute_time();
	_last_run = task_start;
	_gps_time = task_start;
	_airspeed_time = task_start;
	_gt_time = task_start;
	_dist_snsr_time = task_start;
	_vehicle = (VehicleType)constrain(_sih_vtype.get(), static_cast<typeof _sih_vtype.get()>(0),
					  static_cast<typeof _sih_vtype.get()>(1));
}

Sih::~Sih()
{
	perf_free(_loop_perf);
	perf_free(_loop_interval_perf);
}

bool Sih::init()
{
	int rate = _imu_gyro_ratemax.get();

	// default to 250 Hz (4000 us interval)
	if (rate <= 0) {
		rate = 250;
	}

	// 200 - 2000 Hz
	int interval_us = math::constrain(int(roundf(1e6f / rate)), 500, 5000);
	ScheduleOnInterval(interval_us);

	return true;
}

void Sih::Run()
{
	perf_count(_loop_interval_perf);

	// check for parameter updates
	if (_parameter_update_sub.updated()) {
		// clear update
		parameter_update_s pupdate;
		_parameter_update_sub.copy(&pupdate);

		// update parameters from storage
		updateParams();
		parameters_updated();
	}

	perf_begin(_loop_perf);

	_now = hrt_absolute_time();
	_dt = (_now - _last_run) * 1e-6f;
	_last_run = _now;

	read_motors();

	generate_force_and_torques();

	equations_of_motion();

	reconstruct_sensors_signals();

	// update IMU every iteration
	_px4_accel.update(_now, _acc(0), _acc(1), _acc(2));
	_px4_gyro.update(_now, _gyro(0), _gyro(1), _gyro(2));

	// magnetometer published at 50 Hz
	if (_now - _mag_time >= 20_ms
	    && fabs(_mag_offset_x) < 10000
	    && fabs(_mag_offset_y) < 10000
	    && fabs(_mag_offset_z) < 10000) {
		_mag_time = _now;
		_px4_mag.update(_now, _mag(0), _mag(1), _mag(2));
	}

	// baro published at 20 Hz
	if (_now - _baro_time >= 50_ms
	    && fabs(_baro_offset_m) < 10000) {
		_baro_time = _now;
		_px4_baro.set_temperature(_baro_temp_c);
		_px4_baro.update(_now, _baro_p_mBar);
	}

	// gps published at 20Hz
	if (_now - _gps_time >= 50_ms) {
		_gps_time = _now;
		send_gps();
	}

	if (_vehicle == VehicleType::FW && _now - _airspeed_time >= 50_ms) {
		_airspeed_time = _now;
		send_airspeed();
	}

	// distance sensor published at 50 Hz
	if (_now - _dist_snsr_time >= 20_ms
	    && fabs(_distance_snsr_override) < 10000) {
		_dist_snsr_time = _now;
		send_dist_snsr();
	}

	// send groundtruth message every 40 ms
	if (_now - _gt_time >= 40_ms) {
		_gt_time = _now;

		publish_sih();  // publish _sih message for debug purpose
	}

	perf_end(_loop_perf);
}

// store the parameters in a more convenient form
void Sih::parameters_updated()
{
	_T_MAX = _sih_t_max.get();
	_Q_MAX = _sih_q_max.get();
	_L_ROLL = _sih_l_roll.get();
	_L_PITCH = _sih_l_pitch.get();
	_KDV = _sih_kdv.get();
	_KDW = _sih_kdw.get();
	_H0 = _sih_h0.get();

	_LAT0 = (double)_sih_lat0.get() * 1.0e-7;
	_LON0 = (double)_sih_lon0.get() * 1.0e-7;
	_COS_LAT0 = cosl((long double)radians(_LAT0));

	_MASS = _sih_mass.get();

	_W_I = Vector3f(0.0f, 0.0f, _MASS * CONSTANTS_ONE_G);

	_I = diag(Vector3f(_sih_ixx.get(), _sih_iyy.get(), _sih_izz.get()));
	_I(0, 1) = _I(1, 0) = _sih_ixy.get();
	_I(0, 2) = _I(2, 0) = _sih_ixz.get();
	_I(1, 2) = _I(2, 1) = _sih_iyz.get();

	_Im1 = inv(_I);

	_mu_I = Vector3f(_sih_mu_x.get(), _sih_mu_y.get(), _sih_mu_z.get());

	_gps_used = _sih_gps_used.get();
	_baro_offset_m = _sih_baro_offset.get();
	_mag_offset_x = _sih_mag_offset_x.get();
	_mag_offset_y = _sih_mag_offset_y.get();
	_mag_offset_z = _sih_mag_offset_z.get();

	_distance_snsr_min = _sih_distance_snsr_min.get();
	_distance_snsr_max = _sih_distance_snsr_max.get();
	_distance_snsr_override = _sih_distance_snsr_override.get();

	_T_TAU = _sih_thrust_tau.get();
}

// initialization of the variables for the simulator
void Sih::init_variables()
{
	srand(1234);    // initialize the random seed once before calling generate_wgn()

	_p_I = Vector3f(0.0f, 0.0f, 0.0f);
	_v_I = Vector3f(0.0f, 0.0f, 0.0f);
	_q = Quatf(1.0f, 0.0f, 0.0f, 0.0f);
	_w_B = Vector3f(0.0f, 0.0f, 0.0f);

	_u[0] = _u[1] = _u[2] = _u[3] = 0.0f;
}

void Sih::gps_fix()
{
	_sensor_gps.fix_type = 3;  // 3D fix
	_sensor_gps.satellites_used = _gps_used;
	_sensor_gps.heading = NAN;
	_sensor_gps.heading_offset = NAN;
	_sensor_gps.s_variance_m_s = 0.5f;
	_sensor_gps.c_variance_rad = 0.1f;
	_sensor_gps.eph = 0.9f;
	_sensor_gps.epv = 1.78f;
	_sensor_gps.hdop = 0.7f;
	_sensor_gps.vdop = 1.1f;
}

void Sih::gps_no_fix()
{
	_sensor_gps.fix_type = 0;  // 3D fix
	_sensor_gps.satellites_used = _gps_used;
	_sensor_gps.heading = NAN;
	_sensor_gps.heading_offset = NAN;
	_sensor_gps.s_variance_m_s = 100.f;
	_sensor_gps.c_variance_rad = 100.f;
	_sensor_gps.eph = 100.f;
	_sensor_gps.epv = 100.f;
	_sensor_gps.hdop = 100.f;
	_sensor_gps.vdop = 100.f;
}


// read the motor signals outputted from the mixer
void Sih::read_motors()
{
	actuator_outputs_s actuators_out;

	float pwm_middle = 0.5f * (PWM_DEFAULT_MIN + PWM_DEFAULT_MAX);

	if (_actuator_out_sub.update(&actuators_out)) {
		for (int i = 0; i < NB_MOTORS; i++) { // saturate the motor signals
			if (_vehicle == VehicleType::FW && i < 3) { // control surfaces in range [-1,1]
				_u[i] = constrain(2.0f * (actuators_out.output[i] - pwm_middle) / (PWM_DEFAULT_MAX - PWM_DEFAULT_MIN), -1.0f, 1.0f);

			} else { // throttle signals in range [0,1]
				float u_sp = constrain((actuators_out.output[i] - PWM_DEFAULT_MIN) / (PWM_DEFAULT_MAX - PWM_DEFAULT_MIN), 0.0f, 1.0f);
				_u[i] = _u[i] + _dt / _T_TAU * (u_sp - _u[i]); // first order transfer function with time constant tau
			}
		}
	}
}

// generate the motors thrust and torque in the body frame
void Sih::generate_force_and_torques()
{
	if (_vehicle == VehicleType::MC) {
		_T_B = Vector3f(0.0f, 0.0f, -_T_MAX * (+_u[0] + _u[1] + _u[2] + _u[3]));
		_Mt_B = Vector3f(_L_ROLL * _T_MAX * (-_u[0] + _u[1] + _u[2] - _u[3]),
				 _L_PITCH * _T_MAX * (+_u[0] - _u[1] + _u[2] - _u[3]),
				 _Q_MAX * (+_u[0] + _u[1] - _u[2] - _u[3]));
		_Fa_I = -_KDV * _v_I;   // first order drag to slow down the aircraft
		_Ma_B = -_KDW * _w_B;   // first order angular damper

	} else if (_vehicle == VehicleType::FW) {
		_T_B = Vector3f(_T_MAX * _u[3], 0.0f, 0.0f); 	// forward thruster
		// _Mt_B = Vector3f(_Q_MAX*_u[3], 0.0f,0.0f); 	// thruster torque
		_Mt_B = Vector3f();
		generate_aerodynamics();
	}

}

void Sih::generate_aerodynamics()
{
	_v_B = _C_IB.transpose() * _v_I; 	// velocity in body frame [m/s]
	float altitude = _H0 - _p_I(2);
	_wing_l.update_aero(_v_B, _w_B, altitude, _u[0]*FLAP_MAX);
	_wing_r.update_aero(_v_B, _w_B, altitude, -_u[0]*FLAP_MAX);
	_tailplane.update_aero(_v_B, _w_B, altitude, _u[1]*FLAP_MAX, _T_MAX * _u[3]);
	_fin.update_aero(_v_B, _w_B, altitude, _u[2]*FLAP_MAX, _T_MAX * _u[3]);
	_fuselage.update_aero(_v_B, _w_B, altitude);
	_Fa_I = _C_IB * (_wing_l.get_Fa() + _wing_r.get_Fa() + _tailplane.get_Fa() + _fin.get_Fa() + _fuselage.get_Fa())
		- _KDV * _v_I; 	// sum of aerodynamic forces
	// _Ma_B = wing_l.Ma + wing_r.Ma + tailplane.Ma + fin.Ma + flap_moments() -_KDW * _w_B; 	// aerodynamic moments
	_Ma_B = _wing_l.get_Ma() + _wing_r.get_Ma() + _tailplane.get_Ma() + _fin.get_Ma() + _fuselage.get_Ma() - _KDW *
		_w_B; 	// aerodynamic moments
}

// apply the equations of motion of a rigid body and integrate one step
void Sih::equations_of_motion()
{
	_C_IB = matrix::Dcm<float>(_q); // body to inertial transformation

	// Equations of motion of a rigid body
	_p_I_dot = _v_I;                        // position differential
	_v_I_dot = (_W_I + _Fa_I + _C_IB * _T_B) / _MASS;   // conservation of linear momentum
	// _q_dot = _q.derivative1(_w_B);              // attitude differential
	_dq = Quatf::expq(0.5f * _dt * _w_B);
	_w_B_dot = _Im1 * (_Mt_B + _Ma_B - _w_B.cross(_I * _w_B)); // conservation of angular momentum

	// fake ground, avoid free fall
	if (_p_I(2) > 0.0f && (_v_I_dot(2) > 0.0f || _v_I(2) > 0.0f)) {
		if (_vehicle == VehicleType::MC) {
			if (!_grounded) {    // if we just hit the floor
				// for the accelerometer, compute the acceleration that will stop the vehicle in one time step
				_v_I_dot = -_v_I / _dt;

			} else {
				_v_I_dot.setZero();
			}

			_v_I.setZero();
			_w_B.setZero();
			_grounded = true;

		} else if (_vehicle == VehicleType::FW) {
			if (!_grounded) {    // if we just hit the floor
				// for the accelerometer, compute the acceleration that will stop the vehicle in one time step
				_v_I_dot(2) = -_v_I(2) / _dt;

			} else {
				// we only allow negative acceleration in order to takeoff
				_v_I_dot(2) = fminf(_v_I_dot(2), 0.0f);
			}

			// integration: Euler forward
			_p_I = _p_I + _p_I_dot * _dt;
			_v_I = _v_I + _v_I_dot * _dt;
			Eulerf RPY = Eulerf(_q);
			RPY(0) = 0.0f;	// no roll
			RPY(1) = radians(0.0f); 	// pitch slightly up to get some lift
			_q = Quatf(RPY);
			_w_B.setZero();
			_grounded = true;
		}

	} else {
		// integration: Euler forward
		_p_I = _p_I + _p_I_dot * _dt;
		_v_I = _v_I + _v_I_dot * _dt;
		_q = _q * _dq; // as given in attitude_estimator_q_main.cpp
		_q.normalize();
		// integration Runge-Kutta 4
		// rk4_update(_p_I, _v_I, _q, _w_B);
		_w_B = constrain(_w_B + _w_B_dot * _dt, -6.0f * M_PI_F, 6.0f * M_PI_F);
		_grounded = false;
	}
}

// Sih::States Sih::eom_f(States x) 	// equations of motion f: x'=f(x)
// {
// 	States x_dot{}; 	// dx/dt

// 	Dcmf C_IB = matrix::Dcm<float>(x.q); // body to inertial transformation
// 	// Equations of motion of a rigid body
// 	x_dot.p_I = x.v_I;                        // position differential
// 	x_dot.v_I = (_W_I + _Fa_I + C_IB * _T_B) / _MASS;   // conservation of linear momentum
// 	x_dot.q = x.q.derivative1(x.w_B);              // attitude differential
// 	x_dot.w_B = _Im1 * (_Mt_B + _Ma_B - x.w_B.cross(_I * x.w_B)); // conservation of angular momentum

// 	return x_dot;
// }

// reconstruct the noisy sensor signals
void Sih::reconstruct_sensors_signals()
{
	// The sensor signals reconstruction and noise levels are from [1]
	// [1] Bulka, Eitan, and Meyer Nahon. "Autonomous fixed-wing aerobatics: from theory to flight."
	//     In 2018 IEEE International Conference on Robotics and Automation (ICRA), pp. 6573-6580. IEEE, 2018.

	// IMU
	_acc = _C_IB.transpose() * (_v_I_dot - Vector3f(0.0f, 0.0f, CONSTANTS_ONE_G)) + noiseGauss3f(0.5f, 1.7f, 1.4f);
	_gyro = _w_B + noiseGauss3f(0.14f, 0.07f, 0.03f);
	_mag = _C_IB.transpose() * _mu_I + noiseGauss3f(0.02f, 0.02f, 0.03f);
	_mag(0) += _mag_offset_x;
	_mag(1) += _mag_offset_y;
	_mag(2) += _mag_offset_z;

	// barometer
	float altitude = (_H0 - _p_I(2)) + _baro_offset_m + generate_wgn() * 0.14f; // altitude with noise
	_baro_p_mBar = CONSTANTS_STD_PRESSURE_MBAR *        // reconstructed pressure in mBar
		       powf((1.0f + altitude * TEMP_GRADIENT / T1_K), -CONSTANTS_ONE_G / (TEMP_GRADIENT * CONSTANTS_AIR_GAS_CONST));
	_baro_temp_c = T1_K + CONSTANTS_ABSOLUTE_NULL_CELSIUS + TEMP_GRADIENT * altitude; // reconstructed temperture in celcius

	// GPS
	_gps_lat_noiseless = _LAT0 + degrees((double)_p_I(0) / CONSTANTS_RADIUS_OF_EARTH);
	_gps_lon_noiseless = _LON0 + degrees((double)_p_I(1) / CONSTANTS_RADIUS_OF_EARTH) / _COS_LAT0;
	_gps_alt_noiseless = _H0 - _p_I(2);

	_gps_lat = _gps_lat_noiseless + degrees((double)generate_wgn() * 0.2 / CONSTANTS_RADIUS_OF_EARTH);
	_gps_lon = _gps_lon_noiseless + degrees((double)generate_wgn() * 0.2 / CONSTANTS_RADIUS_OF_EARTH) / _COS_LAT0;
	_gps_alt = _gps_alt_noiseless + generate_wgn() * 0.5f;
	_gps_vel = _v_I + noiseGauss3f(0.06f, 0.077f, 0.158f);
}

void Sih::send_gps()
{
	_sensor_gps.timestamp = _now;
	_sensor_gps.lat = (int32_t)(_gps_lat * 1e7);       // Latitude in 1E-7 degrees
	_sensor_gps.lon = (int32_t)(_gps_lon * 1e7); // Longitude in 1E-7 degrees
	_sensor_gps.alt = (int32_t)(_gps_alt * 1000.0f); // Altitude in 1E-3 meters above MSL, (millimetres)
	_sensor_gps.alt_ellipsoid = (int32_t)(_gps_alt * 1000); // Altitude in 1E-3 meters bove Ellipsoid, (millimetres)
	_sensor_gps.vel_ned_valid = true;              // True if NED velocity is valid
	_sensor_gps.vel_m_s = sqrtf(_gps_vel(0) * _gps_vel(0) + _gps_vel(1) * _gps_vel(
					    1)); // GPS ground speed, (metres/sec)
	_sensor_gps.vel_n_m_s = _gps_vel(0);           // GPS North velocity, (metres/sec)
	_sensor_gps.vel_e_m_s = _gps_vel(1);           // GPS East velocity, (metres/sec)
	_sensor_gps.vel_d_m_s = _gps_vel(2);           // GPS Down velocity, (metres/sec)
	_sensor_gps.cog_rad = atan2(_gps_vel(1),
				    _gps_vel(0)); // Course over ground (NOT heading, but direction of movement), -PI..PI, (radians)

	if (_gps_used >= 4) {
		gps_fix();

	} else {
		gps_no_fix();
	}

	// device id
	device::Device::DeviceId device_id;
	device_id.devid_s.bus_type = device::Device::DeviceBusType::DeviceBusType_SIMULATION;
	device_id.devid_s.bus = 0;
	device_id.devid_s.address = 0;
	device_id.devid_s.devtype = DRV_GPS_DEVTYPE_SIM;
	_sensor_gps.device_id = device_id.devid;

	_sensor_gps_pub.publish(_sensor_gps);
}

void Sih::send_airspeed()
{
	airspeed_s  airspeed{};
	airspeed.timestamp = _now;
	airspeed.true_airspeed_m_s	= fmaxf(0.1f, _v_B(0) + generate_wgn() * 0.2f);
	airspeed.indicated_airspeed_m_s = airspeed.true_airspeed_m_s * sqrtf(_wing_l.get_rho() / RHO);
	airspeed.air_temperature_celsius = _baro_temp_c;
	airspeed.confidence = 0.7f;
	_airspeed_pub.publish(airspeed);
}

void Sih::send_dist_snsr()
{
	_distance_snsr.timestamp = _now;
	_distance_snsr.type = distance_sensor_s::MAV_DISTANCE_SENSOR_LASER;
	_distance_snsr.orientation = distance_sensor_s::ROTATION_DOWNWARD_FACING;
	_distance_snsr.min_distance = _distance_snsr_min;
	_distance_snsr.max_distance = _distance_snsr_max;
	_distance_snsr.signal_quality = -1;
	_distance_snsr.device_id = 0;

	if (_distance_snsr_override >= 0.f) {
		_distance_snsr.current_distance = _distance_snsr_override;

	} else {
		_distance_snsr.current_distance = -_p_I(2) / _C_IB(2, 2);

		if (_distance_snsr.current_distance > _distance_snsr_max) {
			// this is based on lightware lw20 behaviour
			_distance_snsr.current_distance = UINT16_MAX / 100.f;

		}
	}

	_distance_snsr_pub.publish(_distance_snsr);
}

void Sih::publish_sih()
{
	// publish angular velocity groundtruth
	_vehicle_angular_velocity_gt.timestamp = hrt_absolute_time();
	_vehicle_angular_velocity_gt.xyz[0] = _w_B(0); // rollspeed;
	_vehicle_angular_velocity_gt.xyz[1] = _w_B(1); // pitchspeed;
	_vehicle_angular_velocity_gt.xyz[2] = _w_B(2); // yawspeed;

	_vehicle_angular_velocity_gt_pub.publish(_vehicle_angular_velocity_gt);

	// publish attitude groundtruth
	_att_gt.timestamp = hrt_absolute_time();
	_att_gt.q[0] = _q(0);
	_att_gt.q[1] = _q(1);
	_att_gt.q[2] = _q(2);
	_att_gt.q[3] = _q(3);

	_att_gt_pub.publish(_att_gt);

	// publish position groundtruth
	_gpos_gt.timestamp = hrt_absolute_time();
	_gpos_gt.lat = _gps_lat_noiseless;
	_gpos_gt.lon = _gps_lon_noiseless;
	_gpos_gt.alt = _gps_alt_noiseless;

	_gpos_gt_pub.publish(_gpos_gt);
}

float Sih::generate_wgn()   // generate white Gaussian noise sample with std=1
{
	// algorithm 1:
	// float temp=((float)(rand()+1))/(((float)RAND_MAX+1.0f));
	// return sqrtf(-2.0f*logf(temp))*cosf(2.0f*M_PI_F*rand()/RAND_MAX);
	// algorithm 2: from BlockRandGauss.hpp
	static float V1, V2, S;
	static bool phase = true;
	float X;

	if (phase) {
		do {
			float U1 = (float)rand() / RAND_MAX;
			float U2 = (float)rand() / RAND_MAX;
			V1 = 2.0f * U1 - 1.0f;
			V2 = 2.0f * U2 - 1.0f;
			S = V1 * V1 + V2 * V2;
		} while (S >= 1.0f || fabsf(S) < 1e-8f);

		X = V1 * float(sqrtf(-2.0f * float(logf(S)) / S));

	} else {
		X = V2 * float(sqrtf(-2.0f * float(logf(S)) / S));
	}

	phase = !phase;
	return X;
}

// generate white Gaussian noise sample vector with specified std
Vector3f Sih::noiseGauss3f(float stdx, float stdy, float stdz)
{
	return Vector3f(generate_wgn() * stdx, generate_wgn() * stdy, generate_wgn() * stdz);
}

int Sih::print_status()
{
	if (_vehicle == VehicleType::MC) {
		PX4_INFO("Running MC");

	} else {
		PX4_INFO("Running FW");
	}

	PX4_INFO("vehicle landed: %d", _grounded);
	PX4_INFO("dt [us]: %d", (int)(_dt * 1e6f));
	PX4_INFO("inertial position NED (m)");
	_p_I.print();
	PX4_INFO("inertial velocity NED (m/s)");
	_v_I.print();
	PX4_INFO("attitude roll-pitch-yaw (deg)");
	(Eulerf(_q) * 180.0f / M_PI_F).print();
	PX4_INFO("angular acceleration roll-pitch-yaw (deg/s)");
	(_w_B * 180.0f / M_PI_F).print();
	PX4_INFO("actuator signals");
	Vector<float, 8> u = Vector<float, 8>(_u);
	u.transpose().print();
	PX4_INFO("Aerodynamic forces NED inertial (N)");
	_Fa_I.print();
	PX4_INFO("Aerodynamic moments body frame (Nm)");
	_Ma_B.print();
	PX4_INFO("v_I.z: %f", (double)_v_I(2));
	PX4_INFO("v_I_dot.z: %f", (double)_v_I_dot(2));
	return 0;
}

int Sih::task_spawn(int argc, char *argv[])
{
	Sih *instance = new Sih();

	if (instance) {
		_object.store(instance);
		_task_id = task_id_is_work_queue;

		if (instance->init()) {
			return PX4_OK;
		}

	} else {
		PX4_ERR("alloc failed");
	}

	delete instance;
	_object.store(nullptr);
	_task_id = -1;

	return PX4_ERROR;
}

int Sih::custom_command(int argc, char *argv[])
{
	return print_usage("unknown command");
}

int Sih::print_usage(const char *reason)
{
	if (reason) {
		PX4_WARN("%s\n", reason);
	}

	PRINT_MODULE_DESCRIPTION(
		R"DESCR_STR(
### Description
This module provide a simulator for quadrotors and fixed-wings running fully
inside the hardware autopilot.

This simulator subscribes to "actuator_outputs" which are the actuator pwm
signals given by the mixer.

This simulator publishes the sensors signals corrupted with realistic noise
in order to incorporate the state estimator in the loop.

### Implementation
The simulator implements the equations of motion using matrix algebra.
Quaternion representation is used for the attitude.
Forward Euler is used for integration.
Most of the variables are declared global in the .hpp file to avoid stack overflow.


)DESCR_STR");

    PRINT_MODULE_USAGE_NAME("sih", "simulation");
    PRINT_MODULE_USAGE_COMMAND("start");
    PRINT_MODULE_USAGE_DEFAULT_COMMANDS();

    return 0;
}

extern "C" __EXPORT int sih_main(int argc, char *argv[])
{
	return Sih::main(argc, argv);
}