simulation organization and cleanup

- new modules/simulation directory to collect all simulators and related modules
 - new Tools/simulation directory to collect and organize scattered simulation submodules, scripts, etc
 - simulation module renamed to simulator_mavlink
 - sih renamed to simulator_sih (not a great name, but I wanted to be clear it was a simulator)
 - ignition_simulator renamed to simulator_ignition_bridge
 - large sitl_target.cmake split by simulation option and in some cases pushed to appropriate modules
 - sitl targets broken down to what's actually available (eg jmavsim only has 1 model and 1 world)
 - new Gazebo consistently referred to as Ignition for now (probably the least confusing thing until we fully drop Gazebo classic support someday)

src/modules/simulation/battery_simulator/BatterySimulator.cpp

@@ -0,0 +1,163 @@
+/****************************************************************************
+ *
+ *   Copyright (c) 2020 PX4 Development Team. All rights reserved.
+ *
+ * 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.
+ *
+ ****************************************************************************/
+
+#include "BatterySimulator.hpp"
+
+BatterySimulator::BatterySimulator() :
+	ModuleParams(nullptr),
+	ScheduledWorkItem(MODULE_NAME, px4::wq_configurations::hp_default),
+	_battery(1, this, BATTERY_SIMLATOR_SAMPLE_INTERVAL_US, battery_status_s::BATTERY_SOURCE_POWER_MODULE)
+{
+}
+
+BatterySimulator::~BatterySimulator()
+{
+	perf_free(_loop_perf);
+}
+
+bool BatterySimulator::init()
+{
+	ScheduleOnInterval(BATTERY_SIMLATOR_SAMPLE_INTERVAL_US);
+	return true;
+}
+
+void BatterySimulator::Run()
+{
+	if (should_exit()) {
+		ScheduleClear();
+		exit_and_cleanup();
+		return;
+	}
+
+	perf_begin(_loop_perf);
+
+	// Check if parameters have changed
+	if (_parameter_update_sub.updated()) {
+		// clear update
+		parameter_update_s param_update;
+		_parameter_update_sub.copy(&param_update);
+
+		updateParams();
+	}
+
+	if (_vehicle_status_sub.updated()) {
+		vehicle_status_s vehicle_status;
+
+		if (_vehicle_status_sub.copy(&vehicle_status)) {
+			_armed = (vehicle_status.arming_state == vehicle_status_s::ARMING_STATE_ARMED);
+		}
+	}
+
+	const hrt_abstime now_us = hrt_absolute_time();
+
+	const float discharge_interval_us = _param_sim_bat_drain.get() * 1000 * 1000;
+
+	if (_armed) {
+		if (_last_integration_us != 0) {
+			_battery_percentage -= (now_us - _last_integration_us) / discharge_interval_us;
+		}
+
+		_last_integration_us = now_us;
+
+	} else {
+		_battery_percentage = 1.f;
+		_last_integration_us = 0;
+	}
+
+	float ibatt = -1.0f; // no current sensor in simulation
+
+	_battery_percentage = math::max(_battery_percentage, _param_bat_min_pct.get() / 100.f);
+	float vbatt = math::interpolate(_battery_percentage, 0.f, 1.f, _battery.empty_cell_voltage(),
+					_battery.full_cell_voltage());
+	vbatt *= _battery.cell_count();
+
+	_battery.setConnected(true);
+	_battery.updateVoltage(vbatt);
+	_battery.updateCurrent(ibatt);
+	_battery.updateAndPublishBatteryStatus(now_us);
+
+	perf_end(_loop_perf);
+}
+
+int BatterySimulator::task_spawn(int argc, char *argv[])
+{
+	BatterySimulator *instance = new BatterySimulator();
+
+	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 BatterySimulator::custom_command(int argc, char *argv[])
+{
+	return print_usage("unknown command");
+}
+
+int BatterySimulator::print_usage(const char *reason)
+{
+	if (reason) {
+		PX4_WARN("%s\n", reason);
+	}
+
+	PRINT_MODULE_DESCRIPTION(
+		R"DESCR_STR(
+### Description
+
+
+)DESCR_STR");
+
+	PRINT_MODULE_USAGE_NAME("battery_simulator", "system");
+	PRINT_MODULE_USAGE_COMMAND("start");
+	PRINT_MODULE_USAGE_DEFAULT_COMMANDS();
+
+	return 0;
+}
+
+extern "C" __EXPORT int battery_simulator_main(int argc, char *argv[])
+{
+	return BatterySimulator::main(argc, argv);
+}