/****************************************************************************
*
* Copyright (c) 2013 PX4 Development Team. All rights reserved.
* Author: Lorenz Meier
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* 3. Neither the name PX4 nor the names of its contributors may be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
****************************************************************************/
/**
* @file fw_att_control_main.c
* Implementation of a generic attitude controller based on classic orthogonal PIDs.
*
* @author Lorenz Meier <lm@inf.ethz.ch>
*
*/
#include <nuttx/config.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <math.h>
#include <poll.h>
#include <time.h>
#include <drivers/drv_hrt.h>
#include <drivers/drv_accel.h>
#include <arch/board/board.h>
#include <uORB/uORB.h>
#include <uORB/topics/airspeed.h>
#include <uORB/topics/vehicle_attitude_setpoint.h>
#include <uORB/topics/manual_control_setpoint.h>
#include <uORB/topics/actuator_controls.h>
#include <uORB/topics/vehicle_rates_setpoint.h>
#include <uORB/topics/vehicle_attitude.h>
#include <uORB/topics/vehicle_control_mode.h>
#include <uORB/topics/parameter_update.h>
#include <systemlib/param/param.h>
#include <systemlib/err.h>
#include <systemlib/pid/pid.h>
#include <geo/geo.h>
#include <systemlib/perf_counter.h>
#include <systemlib/systemlib.h>
#include <mathlib/mathlib.h>
#include <ecl/attitude_fw/ecl_pitch_controller.h>
#include <ecl/attitude_fw/ecl_roll_controller.h>
#include <ecl/attitude_fw/ecl_yaw_controller.h>
/**
* Fixedwing attitude control app start / stop handling function
*
* @ingroup apps
*/
extern "C" __EXPORT int fw_att_control_main(int argc, char *argv[]);
class FixedwingAttitudeControl
{
public:
/**
* Constructor
*/
FixedwingAttitudeControl();
/**
* Destructor, also kills the sensors task.
*/
~FixedwingAttitudeControl();
/**
* Start the sensors task.
*
* @return OK on success.
*/
int start();
private:
bool _task_should_exit; /**< if true, sensor task should exit */
int _control_task; /**< task handle for sensor task */
int _att_sub; /**< vehicle attitude subscription */
int _accel_sub; /**< accelerometer subscription */
int _att_sp_sub; /**< vehicle attitude setpoint */
int _attitude_sub; /**< raw rc channels data subscription */
int _airspeed_sub; /**< airspeed subscription */
int _vcontrol_mode_sub; /**< vehicle status subscription */
int _params_sub; /**< notification of parameter updates */
int _manual_sub; /**< notification of manual control updates */
orb_advert_t _rate_sp_pub; /**< rate setpoint publication */
orb_advert_t _attitude_sp_pub; /**< attitude setpoint point */
orb_advert_t _actuators_0_pub; /**< actuator control group 0 setpoint */
struct vehicle_attitude_s _att; /**< vehicle attitude */
struct accel_report _accel; /**< body frame accelerations */
struct vehicle_attitude_setpoint_s _att_sp; /**< vehicle attitude setpoint */
struct manual_control_setpoint_s _manual; /**< r/c channel data */
struct airspeed_s _airspeed; /**< airspeed */
struct vehicle_control_mode_s _vcontrol_mode; /**< vehicle control mode */
struct actuator_controls_s _actuators; /**< actuator control inputs */
perf_counter_t _loop_perf; /**< loop performance counter */
bool _setpoint_valid; /**< flag if the position control setpoint is valid */
bool _airspeed_valid; /**< flag if the airspeed measurement is valid */
struct {
float tconst;
float p_p;
float p_d;
float p_i;
float p_rmax_pos;
float p_rmax_neg;
float p_integrator_max;
float p_roll_feedforward;
float r_p;
float r_d;
float r_i;
float r_integrator_max;
float r_rmax;
float y_p;
float y_i;
float y_d;
float y_roll_feedforward;
float y_integrator_max;
float airspeed_min;
float airspeed_trim;
float airspeed_max;
} _parameters; /**< local copies of interesting parameters */
struct {
param_t tconst;
param_t p_p;
param_t p_d;
param_t p_i;
param_t p_rmax_pos;
param_t p_rmax_neg;
param_t p_integrator_max;
param_t p_roll_feedforward;
param_t r_p;
param_t r_d;
param_t r_i;
param_t r_integrator_max;
param_t r_rmax;
param_t y_p;
param_t y_i;
param_t y_d;
param_t y_roll_feedforward;
param_t y_integrator_max;
param_t airspeed_min;
param_t airspeed_trim;
param_t airspeed_max;
} _parameter_handles; /**< handles for interesting parameters */
ECL_RollController _roll_ctrl;
ECL_PitchController _pitch_ctrl;
ECL_YawController _yaw_ctrl;
/**
* Update our local parameter cache.
*/
int parameters_update();
/**
* Update control outputs
*
*/
void control_update();
/**
* Check for changes in vehicle control mode.
*/
void vehicle_control_mode_poll();
/**
* Check for changes in manual inputs.
*/
void vehicle_manual_poll();
/**
* Check for airspeed updates.
*/
bool vehicle_airspeed_poll();
/**
* Check for accel updates.
*/
void vehicle_accel_poll();
/**
* Check for set triplet updates.
*/
void vehicle_setpoint_poll();
/**
* Shim for calling task_main from task_create.
*/
static void task_main_trampoline(int argc, char *argv[]);
/**
* Main sensor collection task.
*/
void task_main() __attribute__((noreturn));
};
namespace att_control
{
/* oddly, ERROR is not defined for c++ */
#ifdef ERROR
# undef ERROR
#endif
static const int ERROR = -1;
FixedwingAttitudeControl *g_control;
}
FixedwingAttitudeControl::FixedwingAttitudeControl() :
_task_should_exit(false),
_control_task(-1),
/* subscriptions */
_att_sub(-1),
_accel_sub(-1),
_airspeed_sub(-1),
_vcontrol_mode_sub(-1),
_params_sub(-1),
_manual_sub(-1),
/* publications */
_rate_sp_pub(-1),
_actuators_0_pub(-1),
_attitude_sp_pub(-1),
/* performance counters */
_loop_perf(perf_alloc(PC_ELAPSED, "fw att control")),
/* states */
_setpoint_valid(false),
_airspeed_valid(false)
{
_parameter_handles.tconst = param_find("FW_ATT_TC");
_parameter_handles.p_p = param_find("FW_P_P");
_parameter_handles.p_d = param_find("FW_P_D");
_parameter_handles.p_i = param_find("FW_P_I");
_parameter_handles.p_rmax_pos = param_find("FW_P_RMAX_POS");
_parameter_handles.p_rmax_neg = param_find("FW_P_RMAX_NEG");
_parameter_handles.p_integrator_max = param_find("FW_P_integrator_max");
_parameter_handles.p_roll_feedforward = param_find("FW_P_ROLLFF");
_parameter_handles.r_p = param_find("FW_R_P");
_parameter_handles.r_d = param_find("FW_R_D");
_parameter_handles.r_i = param_find("FW_R_I");
_parameter_handles.r_integrator_max = param_find("FW_R_integrator_max");
_parameter_handles.r_rmax = param_find("FW_R_RMAX");
_parameter_handles.y_p = param_find("FW_Y_P");
_parameter_handles.y_i = param_find("FW_Y_I");
_parameter_handles.y_d = param_find("FW_Y_D");
_parameter_handles.y_roll_feedforward = param_find("FW_Y_ROLLFF");
_parameter_handles.y_integrator_max = param_find("FW_Y_integrator_max");
_parameter_handles.airspeed_min = param_find("FW_AIRSPD_MIN");
_parameter_handles.airspeed_trim = param_find("FW_AIRSPD_TRIM");
_parameter_handles.airspeed_max = param_find("FW_AIRSPD_MAX");
/* fetch initial parameter values */
parameters_update();
}
FixedwingAttitudeControl::~FixedwingAttitudeControl()
{
if (_control_task != -1) {
/* task wakes up every 100ms or so at the longest */
_task_should_exit = true;
/* wait for a second for the task to quit at our request */
unsigned i = 0;
do {
/* wait 20ms */
usleep(20000);
/* if we have given up, kill it */
if (++i > 50) {
task_delete(_control_task);
break;
}
} while (_control_task != -1);
}
att_control::g_control = nullptr;
}
int
FixedwingAttitudeControl::parameters_update()
{
param_get(_parameter_handles.tconst, &(_parameters.tconst));
param_get(_parameter_handles.p_p, &(_parameters.p_p));
param_get(_parameter_handles.p_d, &(_parameters.p_d));
param_get(_parameter_handles.p_i, &(_parameters.p_i));
param_get(_parameter_handles.p_rmax_pos, &(_parameters.p_rmax_pos));
param_get(_parameter_handles.p_rmax_neg, &(_parameters.p_rmax_neg));
param_get(_parameter_handles.p_integrator_max, &(_parameters.p_integrator_max));
param_get(_parameter_handles.p_roll_feedforward, &(_parameters.p_roll_feedforward));
param_get(_parameter_handles.r_p, &(_parameters.r_p));
param_get(_parameter_handles.r_d, &(_parameters.r_d));
param_get(_parameter_handles.r_i, &(_parameters.r_i));
param_get(_parameter_handles.r_integrator_max, &(_parameters.r_integrator_max));
param_get(_parameter_handles.r_rmax, &(_parameters.r_rmax));
param_get(_parameter_handles.y_p, &(_parameters.y_p));
param_get(_parameter_handles.y_i, &(_parameters.y_i));
param_get(_parameter_handles.y_d, &(_parameters.y_d));
param_get(_parameter_handles.y_roll_feedforward, &(_parameters.y_roll_feedforward));
param_get(_parameter_handles.y_integrator_max, &(_parameters.y_integrator_max));
param_get(_parameter_handles.airspeed_min, &(_parameters.airspeed_min));
param_get(_parameter_handles.airspeed_trim, &(_parameters.airspeed_trim));
param_get(_parameter_handles.airspeed_max, &(_parameters.airspeed_max));
/* pitch control parameters */
_pitch_ctrl.set_time_constant(_parameters.tconst);
_pitch_ctrl.set_k_p(math::radians(_parameters.p_p));
_pitch_ctrl.set_k_i(math::radians(_parameters.p_i));
_pitch_ctrl.set_k_d(math::radians(_parameters.p_d));
_pitch_ctrl.set_integrator_max(math::radians(_parameters.p_integrator_max));
_pitch_ctrl.set_max_rate_pos(math::radians(_parameters.p_rmax_pos));
_pitch_ctrl.set_max_rate_neg(math::radians(_parameters.p_rmax_neg));
_pitch_ctrl.set_roll_ff(math::radians(_parameters.p_roll_feedforward));
/* roll control parameters */
_roll_ctrl.set_time_constant(_parameters.tconst);
_roll_ctrl.set_k_p(math::radians(_parameters.r_p));
_roll_ctrl.set_k_i(math::radians(_parameters.r_i));
_roll_ctrl.set_k_d(math::radians(_parameters.r_d));
_roll_ctrl.set_integrator_max(math::radians(_parameters.r_integrator_max));
_roll_ctrl.set_max_rate(math::radians(_parameters.r_rmax));
/* yaw control parameters */
_yaw_ctrl.set_k_side(math::radians(_parameters.y_p));
_yaw_ctrl.set_k_i(math::radians(_parameters.y_i));
_yaw_ctrl.set_k_d(math::radians(_parameters.y_d));
_yaw_ctrl.set_k_roll_ff(math::radians(_parameters.y_roll_feedforward));
_yaw_ctrl.set_integrator_max(math::radians(_parameters.y_integrator_max));
return OK;
}
void
FixedwingAttitudeControl::vehicle_control_mode_poll()
{
bool vcontrol_mode_updated;
/* Check HIL state if vehicle status has changed */
orb_check(_vcontrol_mode_sub, &vcontrol_mode_updated);
if (vcontrol_mode_updated) {
orb_copy(ORB_ID(vehicle_control_mode), _vcontrol_mode_sub, &_vcontrol_mode);
}
}
void
FixedwingAttitudeControl::vehicle_manual_poll()
{
bool manual_updated;
/* get pilots inputs */
orb_check(_manual_sub, &manual_updated);
if (manual_updated) {
orb_copy(ORB_ID(manual_control_setpoint), _manual_sub, &_manual);
}
}
bool
FixedwingAttitudeControl::vehicle_airspeed_poll()
{
/* check if there is a new position */
bool airspeed_updated;
orb_check(_airspeed_sub, &airspeed_updated);
if (airspeed_updated) {
orb_copy(ORB_ID(airspeed), _airspeed_sub, &_airspeed);
return true;
}
return false;
}
void
FixedwingAttitudeControl::vehicle_accel_poll()
{
/* check if there is a new position */
bool accel_updated;
orb_check(_accel_sub, &accel_updated);
if (accel_updated) {
orb_copy(ORB_ID(sensor_accel), _accel_sub, &_accel);
}
}
void
FixedwingAttitudeControl::vehicle_setpoint_poll()
{
/* check if there is a new setpoint */
bool att_sp_updated;
orb_check(_att_sp_sub, &att_sp_updated);
if (att_sp_updated) {
orb_copy(ORB_ID(vehicle_attitude_setpoint), _att_sp_sub, &_att_sp);
_setpoint_valid = true;
}
}
void
FixedwingAttitudeControl::task_main_trampoline(int argc, char *argv[])
{
att_control::g_control->task_main();
}
void
FixedwingAttitudeControl::task_main()
{
/* inform about start */
warnx("Initializing..");
fflush(stdout);
/*
* do subscriptions
*/
_att_sp_sub = orb_subscribe(ORB_ID(vehicle_attitude_setpoint));
_att_sub = orb_subscribe(ORB_ID(vehicle_attitude));
_accel_sub = orb_subscribe(ORB_ID(sensor_accel));
_airspeed_sub = orb_subscribe(ORB_ID(airspeed));
_vcontrol_mode_sub = orb_subscribe(ORB_ID(vehicle_control_mode));
_params_sub = orb_subscribe(ORB_ID(parameter_update));
_manual_sub = orb_subscribe(ORB_ID(manual_control_setpoint));
/* rate limit vehicle status updates to 5Hz */
orb_set_interval(_vcontrol_mode_sub, 200);
orb_set_interval(_att_sub, 100);
parameters_update();
/* get an initial update for all sensor and status data */
(void)vehicle_airspeed_poll();
vehicle_setpoint_poll();
vehicle_accel_poll();
vehicle_control_mode_poll();
vehicle_manual_poll();
/* wakeup source(s) */
struct pollfd fds[2];
/* Setup of loop */
fds[0].fd = _params_sub;
fds[0].events = POLLIN;
fds[1].fd = _att_sub;
fds[1].events = POLLIN;
while (!_task_should_exit) {
/* wait for up to 500ms for data */
int pret = poll(&fds[0], (sizeof(fds) / sizeof(fds[0])), 100);
/* timed out - periodic check for _task_should_exit, etc. */
if (pret == 0)
continue;
/* this is undesirable but not much we can do - might want to flag unhappy status */
if (pret < 0) {
warn("poll error %d, %d", pret, errno);
continue;
}
perf_begin(_loop_perf);
/* only update parameters if they changed */
if (fds[0].revents & POLLIN) {
/* read from param to clear updated flag */
struct parameter_update_s update;
orb_copy(ORB_ID(parameter_update), _params_sub, &update);
/* update parameters from storage */
parameters_update();
}
/* only run controller if attitude changed */
if (fds[1].revents & POLLIN) {
static uint64_t last_run = 0;
float deltaT = (hrt_absolute_time() - last_run) / 1000000.0f;
last_run = hrt_absolute_time();
/* guard against too large deltaT's */
if (deltaT > 1.0f)
deltaT = 0.01f;
/* load local copies */
orb_copy(ORB_ID(vehicle_attitude), _att_sub, &_att);
_airspeed_valid = vehicle_airspeed_poll();
vehicle_setpoint_poll();
vehicle_accel_poll();
vehicle_control_mode_poll();
vehicle_manual_poll();
/* lock integrator until control is started */
bool lock_integrator;
if (_vcontrol_mode.flag_control_attitude_enabled) {
lock_integrator = false;
} else {
lock_integrator = true;
}
/* decide if in stabilized or full manual control */
if (_vcontrol_mode.flag_control_attitude_enabled) {
/* scale from radians to normalized -1 .. 1 range */
const float actuator_scaling = 1.0f / (M_PI_F / 4.0f);
/* scale around tuning airspeed */
float airspeed;
/* if airspeed is smaller than min, the sensor is not giving good readings */
if (!_airspeed_valid ||
(_airspeed.indicated_airspeed_m_s < _parameters.airspeed_min) ||
!isfinite(_airspeed.indicated_airspeed_m_s)) {
airspeed = _parameters.airspeed_min + (_parameters.airspeed_max - _parameters.airspeed_min) / 2.0f;
} else {
airspeed = _airspeed.indicated_airspeed_m_s;
}
float airspeed_scaling = _parameters.airspeed_trim / airspeed;
//warnx("aspd scale: %6.2f act scale: %6.2f", airspeed_scaling, actuator_scaling);
float roll_sp, pitch_sp;
float throttle_sp = 0.0f;
if (_vcontrol_mode.flag_control_velocity_enabled || _vcontrol_mode.flag_control_position_enabled) {
roll_sp = _att_sp.roll_body;
pitch_sp = _att_sp.pitch_body;
throttle_sp = _att_sp.thrust;
/* reset integrals where needed */
if (_att_sp.roll_reset_integral)
_roll_ctrl.reset_integrator();
} else {
/*
* Scale down roll and pitch as the setpoints are radians
* and a typical remote can only do 45 degrees, the mapping is
* -1..+1 to -45..+45 degrees or -0.75..+0.75 radians.
*
* With this mapping the stick angle is a 1:1 representation of
* the commanded attitude. If more than 45 degrees are desired,
* a scaling parameter can be applied to the remote.
*/
roll_sp = _manual.roll * 0.75f;
pitch_sp = _manual.pitch * 0.75f;
throttle_sp = _manual.throttle;
_actuators.control[4] = _manual.flaps;
/*
* in manual mode no external source should / does emit attitude setpoints.
* emit the manual setpoint here to allow attitude controller tuning
* in attitude control mode.
*/
struct vehicle_attitude_setpoint_s att_sp;
att_sp.timestamp = hrt_absolute_time();
att_sp.roll_body = roll_sp;
att_sp.pitch_body = pitch_sp;
att_sp.yaw_body = 0.0f;
att_sp.thrust = throttle_sp;
/* lazily publish the setpoint only once available */
if (_attitude_sp_pub > 0) {
/* publish the attitude setpoint */
orb_publish(ORB_ID(vehicle_attitude_setpoint), _attitude_sp_pub, &att_sp);
} else {
/* advertise and publish */
_attitude_sp_pub = orb_advertise(ORB_ID(vehicle_attitude_setpoint), &att_sp);
}
}
float roll_rad = _roll_ctrl.control(roll_sp, _att.roll, _att.rollspeed,
airspeed_scaling, lock_integrator, _parameters.airspeed_min, _parameters.airspeed_max, airspeed);
_actuators.control[0] = (isfinite(roll_rad)) ? roll_rad * actuator_scaling : 0.0f;
float pitch_rad = _pitch_ctrl.control(pitch_sp, _att.pitch, _att.pitchspeed, _att.roll, airspeed_scaling,
lock_integrator, _parameters.airspeed_min, _parameters.airspeed_max, airspeed);
_actuators.control[1] = (isfinite(pitch_rad)) ? pitch_rad * actuator_scaling : 0.0f;
float yaw_rad = _yaw_ctrl.control(_att.roll, _att.yawspeed, _accel.y, airspeed_scaling, lock_integrator,
_parameters.airspeed_min, _parameters.airspeed_max, airspeed);
_actuators.control[2] = (isfinite(yaw_rad)) ? yaw_rad * actuator_scaling : 0.0f;
/* throttle passed through */
_actuators.control[3] = (isfinite(throttle_sp)) ? throttle_sp : 0.0f;
// warnx("aspd: %s: %6.2f, aspd scaling: %6.2f, controls: %5.2f %5.2f %5.2f %5.2f", (_airspeed_valid) ? "valid" : "unknown",
// airspeed, airspeed_scaling, _actuators.control[0], _actuators.control[1],
// _actuators.control[2], _actuators.control[3]);
/*
* Lazily publish the rate setpoint (for analysis, the actuators are published below)
* only once available
*/
vehicle_rates_setpoint_s rates_sp;
rates_sp.roll = _roll_ctrl.get_desired_rate();
rates_sp.pitch = _pitch_ctrl.get_desired_rate();
rates_sp.yaw = 0.0f; // XXX not yet implemented
rates_sp.timestamp = hrt_absolute_time();
if (_rate_sp_pub > 0) {
/* publish the attitude setpoint */
orb_publish(ORB_ID(vehicle_rates_setpoint), _rate_sp_pub, &rates_sp);
} else {
/* advertise and publish */
_rate_sp_pub = orb_advertise(ORB_ID(vehicle_rates_setpoint), &rates_sp);
}
} else {
/* manual/direct control */
_actuators.control[0] = _manual.roll;
_actuators.control[1] = _manual.pitch;
_actuators.control[2] = _manual.yaw;
_actuators.control[3] = _manual.throttle;
_actuators.control[4] = _manual.flaps;
}
/* lazily publish the setpoint only once available */
_actuators.timestamp = hrt_absolute_time();
if (_actuators_0_pub > 0) {
/* publish the attitude setpoint */
orb_publish(ORB_ID(actuator_controls_0), _actuators_0_pub, &_actuators);
} else {
/* advertise and publish */
_actuators_0_pub = orb_advertise(ORB_ID(actuator_controls_0), &_actuators);
}
}
perf_end(_loop_perf);
}
warnx("exiting.\n");
_control_task = -1;
_exit(0);
}
int
FixedwingAttitudeControl::start()
{
ASSERT(_control_task == -1);
/* start the task */
_control_task = task_spawn_cmd("fw_att_control",
SCHED_DEFAULT,
SCHED_PRIORITY_MAX - 5,
2048,
(main_t)&FixedwingAttitudeControl::task_main_trampoline,
nullptr);
if (_control_task < 0) {
warn("task start failed");
return -errno;
}
return OK;
}
int fw_att_control_main(int argc, char *argv[])
{
if (argc < 1)
errx(1, "usage: fw_att_control {start|stop|status}");
if (!strcmp(argv[1], "start")) {
if (att_control::g_control != nullptr)
errx(1, "already running");
att_control::g_control = new FixedwingAttitudeControl;
if (att_control::g_control == nullptr)
errx(1, "alloc failed");
if (OK != att_control::g_control->start()) {
delete att_control::g_control;
att_control::g_control = nullptr;
err(1, "start failed");
}
exit(0);
}
if (!strcmp(argv[1], "stop")) {
if (att_control::g_control == nullptr)
errx(1, "not running");
delete att_control::g_control;
att_control::g_control = nullptr;
exit(0);
}
if (!strcmp(argv[1], "status")) {
if (att_control::g_control) {
errx(0, "running");
} else {
errx(1, "not running");
}
}
warnx("unrecognized command");
return 1;
}