path: root/src/platforms/ros/nodes/mc_mixer/mc_mixer.cpp

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/**
 * @file mc_mixer.cpp
 * Dummy multicopter mixer for euroc simulator (gazebo)
 *
 * @author Roman Bapst <romanbapst@yahoo.de>
*/
 #include <ros/ros.h>
 #include <px4.h>
 #include <lib/mathlib/mathlib.h>
 #include <mav_msgs/MotorSpeed.h>

 class MultirotorMixer {
public:

	MultirotorMixer();

	struct Rotor {
		float roll_scale;
		float pitch_scale;
		float yaw_scale;
	};

	void actuatorControlsCallback(const PX4_TOPIC_T(actuator_controls_0) &msg);

private:

	ros::NodeHandle _n;
	ros::Subscriber _sub;
	ros::Publisher _pub;

	const Rotor *_rotors;

	unsigned _rotor_count;

	struct {
		float control[6];
	}inputs;

	struct  {
		float control[6];
	}outputs;

	void mix();
};

const MultirotorMixer::Rotor _config_x[] = {
	{ -0.707107,  0.707107,  1.00 },
	{  0.707107, -0.707107,  1.00 },
	{  0.707107,  0.707107, -1.00 },
	{ -0.707107, -0.707107, -1.00 },
};

const MultirotorMixer::Rotor _config_quad_plus[] = {
	{ -1.000000,  0.000000,  1.00 },
	{  1.000000,  0.000000,  1.00 },
	{  0.000000,  1.000000, -1.00 },
	{ -0.000000, -1.000000, -1.00 },
};

const MultirotorMixer::Rotor *_config_index[3] = {
	&_config_x[0],
	&_config_quad_plus[0],
};

MultirotorMixer::MultirotorMixer():
	_n(),
	_rotor_count(4),
	_rotors(_config_index[1]) //XXX +config hardcoded
{
	_sub = _n.subscribe("actuator_controls_0", 1, &MultirotorMixer::actuatorControlsCallback,this);
	_pub = _n.advertise<mav_msgs::MotorSpeed>("/mixed_motor_commands",10);
	if (!_n.hasParam("motor_scaling_radps")) {
		_n.setParam("motor_scaling_radps", 1500.0);
	}
}

void MultirotorMixer::mix() {
	float roll = math::constrain(inputs.control[0], -1.0f, 1.0f);
	float pitch = math::constrain(inputs.control[1], -1.0f, 1.0f);
	float yaw = math::constrain(inputs.control[2], -1.0f, 1.0f);
	float thrust = math::constrain(inputs.control[3], 0.0f, 1.0f);
	float min_out = 0.0f;
	float max_out = 0.0f;

	/* perform initial mix pass yielding unbounded outputs, ignore yaw */
	for (unsigned i = 0; i < _rotor_count; i++) {
		float out = roll * _rotors[i].roll_scale
				+ pitch * _rotors[i].pitch_scale + thrust;

		/* limit yaw if it causes outputs clipping */
		if (out >= 0.0f && out < -yaw * _rotors[i].yaw_scale) {
			yaw = -out / _rotors[i].yaw_scale;
		}

		/* calculate min and max output values */
		if (out < min_out) {
			min_out = out;
		}
		if (out > max_out) {
			max_out = out;
		}

		outputs.control[i] = out;
	}
	/* scale down roll/pitch controls if some outputs are negative, don't add yaw, keep total thrust */
	if (min_out < 0.0f) {
		float scale_in = thrust / (thrust - min_out);

		/* mix again with adjusted controls */
		for (unsigned i = 0; i < _rotor_count; i++) {
			outputs.control[i] = scale_in
					* (roll * _rotors[i].roll_scale
							+ pitch * _rotors[i].pitch_scale) + thrust;
		}

	} else {
		/* roll/pitch mixed without limiting, add yaw control */
		for (unsigned i = 0; i < _rotor_count; i++) {
			outputs.control[i] += yaw * _rotors[i].yaw_scale;
		}
	}

	/* scale down all outputs if some outputs are too large, reduce total thrust */
	float scale_out;
	if (max_out > 1.0f) {
		scale_out = 1.0f / max_out;

	} else {
		scale_out = 1.0f;
	}

	/* scale outputs to range _idle_speed..1, and do final limiting */
	for (unsigned i = 0; i < _rotor_count; i++) {
		outputs.control[i] = math::constrain(outputs.control[i], 0.0f, 1.0f);
	}
}

 void MultirotorMixer::actuatorControlsCallback(const PX4_TOPIC_T(actuator_controls_0) &msg)
{
	// read message
	for(int i = 0;i < msg.NUM_ACTUATOR_CONTROLS;i++) {
		inputs.control[i] = msg.control[i];
	}

	// mix
	mix();

	// publish message
	mav_msgs::MotorSpeed rotor_vel_msg;
	double scaling;
	_n.getParamCached("motor_scaling_radps", scaling);
	for (int i = 0; i < _rotor_count; i++) {
		rotor_vel_msg.motor_speed.push_back(outputs.control[i] * scaling);
	}
	_pub.publish(rotor_vel_msg);
}

 int main(int argc, char **argv)
{
  ros::init(argc, argv, "mc_mixer");
  MultirotorMixer mixer;
  ros::spin();

  return 0;
}