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 "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 <uORB/topics/actuator_outputs.h>
#include <uORB/topics/vehicle_status.h>     // to get the HIL status

#include <unistd.h>
#include <string.h>
#include <fcntl.h>
#include <termios.h>

using namespace math;
using namespace matrix;

int Sih::print_status()
{
    PX4_INFO("Running");
    return 0;
}

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


int Sih::task_spawn(int argc, char *argv[])
{
    _task_id = px4_task_spawn_cmd("sih",
                      SCHED_DEFAULT,
                      SCHED_PRIORITY_MAX,
                      1024,
                      (px4_main_t)&run_trampoline,
                      (char *const *)argv);

    if (_task_id < 0) {
        _task_id = -1;
        return -errno;
    }

    return 0;
}

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

    if (instance == nullptr) {
        PX4_ERR("alloc failed");
    }

    return instance;
}

Sih::Sih() :
    ModuleParams(nullptr),
    _loop_perf(perf_alloc(PC_ELAPSED, "sih_execution")),
    _sampling_perf(perf_alloc(PC_ELAPSED, "sih_sampling"))
{
}

void Sih::run()
{
    // to subscribe to (read) the actuators_out pwm
    _actuator_out_sub = orb_subscribe(ORB_ID(actuator_outputs));

    // initialize parameters
    parameters_update_poll();

    init_variables();
    init_sensors();

    const hrt_abstime task_start = hrt_absolute_time();
    _last_run = task_start;
    _gps_time = task_start;
    _serial_time = task_start;

    px4_sem_init(&_data_semaphore, 0, 0);

    hrt_call_every(&_timer_call, LOOP_INTERVAL, LOOP_INTERVAL, timer_callback, &_data_semaphore);

    perf_begin(_sampling_perf);

    while (!should_exit()) {
        px4_sem_wait(&_data_semaphore);     // periodic real time wakeup

        perf_end(_sampling_perf);
        perf_begin(_sampling_perf);

        perf_begin(_loop_perf);

        inner_loop();   // main execution function

        perf_end(_loop_perf);
    }

    hrt_cancel(&_timer_call);   // close the periodic timer interruption
    px4_sem_destroy(&_data_semaphore);
    orb_unsubscribe(_actuator_out_sub);
}

// timer_callback() is used as a real time callback to post the semaphore
void Sih::timer_callback(void *sem)
{
    px4_sem_post((px4_sem_t *)sem);
}

// this is the main execution waken up periodically by the semaphore
void Sih::inner_loop()
{
    _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();

    send_IMU();

    if (_now - _gps_time >= 50000) { // gps published at 20Hz
        _gps_time = _now;
        send_gps();
    }

    // send uart message every 40 ms
    if (_now - _serial_time >= 40000) {
        _serial_time = _now;

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

        parameters_update_poll();   // update the parameters if needed
    }
}

void Sih::parameters_update_poll()
{
    // 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();
    }
}

// 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(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());
}

// 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::init_sensors()
{
    _vehicle_gps_pos.fix_type = 3;  // 3D fix
    _vehicle_gps_pos.satellites_used = 8;
    _vehicle_gps_pos.heading = NAN;
    _vehicle_gps_pos.heading_offset = NAN;
    _vehicle_gps_pos.s_variance_m_s = 0.5f;
    _vehicle_gps_pos.c_variance_rad = 0.1f;
    _vehicle_gps_pos.eph = 0.9f;
    _vehicle_gps_pos.epv = 1.78f;
    _vehicle_gps_pos.hdop = 0.7f;
    _vehicle_gps_pos.vdop = 1.1f;
}

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

    // read the actuator outputs
    bool updated = false;
    orb_check(_actuator_out_sub, &updated);

    if (updated) {
        orb_copy(ORB_ID(actuator_outputs), _actuator_out_sub, &actuators_out);

        for (int i = 0; i < NB_MOTORS; i++) { // saturate the motor signals
            _u[i] = constrain((actuators_out.output[i] - PWM_DEFAULT_MIN) / (PWM_DEFAULT_MAX - PWM_DEFAULT_MIN), 0.0f, 1.0f);
        }
    }
}

// generate the motors thrust and torque in the body frame
void Sih::generate_force_and_torques()
{
    _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
}

// apply the equations of motion of a rigid body and integrate one step
void Sih::equations_of_motion()
{
    _C_IB = _q.to_dcm(); // 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
    _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 (!_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 {
        // integration: Euler forward
        _p_I = _p_I + _p_I_dot * _dt;
        _v_I = _v_I + _v_I_dot * _dt;
        _q = _q + _q_dot * _dt; // as given in attitude_estimator_q_main.cpp
        _q.normalize();
        _w_B = _w_B + _w_B_dot * _dt;
        _grounded = false;
    }
}

// reconstruct the noisy sensor signals
void Sih::reconstruct_sensors_signals()
{
    // The sensor signals reconstruction and noise levels are from
    // 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);

    // barometer
    float altitude = (_H0 - _p_I(2)) + 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 + (double)(generate_wgn() * 7.2e-6f); // latitude in degrees
    _gps_lon = _gps_lon_noiseless + (double)(generate_wgn() * 1.75e-5f); // longitude in degrees
    _gps_alt = _gps_alt_noiseless + generate_wgn() * 1.78f;
    _gps_vel = _v_I + noiseGauss3f(0.06f, 0.077f, 0.158f);
}

void Sih::send_IMU()
{
    // gyro
    {
        static constexpr float scaling = 1000.0f;
        _px4_gyro.set_scale(1 / scaling);
        _px4_gyro.set_temperature(T1_C);
        _px4_gyro.update(_now, _gyro(0) * scaling, _gyro(1) * scaling, _gyro(2) * scaling);
    }

    // accel
    {
        static constexpr float scaling = 1000.0f;
        _px4_accel.set_scale(1 / scaling);
        _px4_accel.set_temperature(T1_C);
        _px4_accel.update(_now, _acc(0) * scaling, _acc(1) * scaling, _acc(2) * scaling);
    }

    // magnetometer
    {
        static constexpr float scaling = 1000.0f;
        _px4_mag.set_scale(1 / scaling);
        _px4_mag.set_temperature(T1_C);
        _px4_mag.update(_now, _mag(0) * scaling, _mag(1) * scaling, _mag(2) * scaling);
    }

    // baro
    {
        _px4_baro.set_temperature(_baro_temp_c);
        _px4_baro.update(_now, _baro_p_mBar);
    }
}

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

    if (_vehicle_gps_pos_pub != nullptr) {
        orb_publish(ORB_ID(vehicle_gps_position), _vehicle_gps_pos_pub, &_vehicle_gps_pos);

    } else {
        _vehicle_gps_pos_pub = orb_advertise(ORB_ID(vehicle_gps_position), &_vehicle_gps_pos);
    }
}

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;

    if (_vehicle_angular_velocity_gt_pub != nullptr) {
        orb_publish(ORB_ID(vehicle_angular_velocity_groundtruth), _vehicle_angular_velocity_gt_pub,
                &_vehicle_angular_velocity_gt);

    } else {
        _vehicle_angular_velocity_gt_pub = orb_advertise(ORB_ID(vehicle_angular_velocity_groundtruth),
                           &_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);

    if (_att_gt_pub != nullptr) {
        orb_publish(ORB_ID(vehicle_attitude_groundtruth), _att_gt_pub, &_att_gt);

    } else {
        _att_gt_pub = orb_advertise(ORB_ID(vehicle_attitude_groundtruth), &_att_gt);
    }

    _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.vel_n = _v_I(0);
    _gpos_gt.vel_e = _v_I(1);
    _gpos_gt.vel_d = _v_I(2);

    if (_gpos_gt_pub != nullptr) {
        orb_publish(ORB_ID(vehicle_global_position_groundtruth), _gpos_gt_pub, &_gpos_gt);

    } else {
        _gpos_gt_pub = orb_advertise(ORB_ID(vehicle_global_position_groundtruth), &_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_main(int argc, char *argv[])
{
    return Sih::main(argc, argv);
}

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 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;
}