rtabmap/corelib/include/rtabmap/core/IMU.h

/*
Copyright (c) 2010-2026, Mathieu Labbe - IntRoLab - Universite de Sherbrooke
All rights reserved.

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      names of its contributors may be used to endorse or promote products
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*/

#ifndef IMU_H_
#define IMU_H_

#include "rtabmap/core/rtabmap_core_export.h" // DLL export/import defines
#include <opencv2/core/core.hpp>
#include <rtabmap/utilite/UEvent.h>
#include <rtabmap/core/Transform.h>

namespace rtabmap {

/**
 * @class IMU
 * @brief Inertial measurement sample (ROS @c sensor_msgs/Imu-like fields).
 *
 * Holds orientation (quaternion), angular velocity, linear acceleration, optional
 * 3×3 row-major covariance matrices (double), and an optional @ref Transform
 * expressing the IMU frame relative to the robot base.
 *
 * @ref empty() is true when @ref localTransform() is null (default constructor).
 * A sample constructed with @ref Transform::getIdentity() is not empty.
 *
 * @ref convertToBaseFrame() rotates linear/angular velocity (and orientation when
 * quaternion x/y/z are non-zero) into the base frame, then clears rotation in
 * @ref localTransform() while keeping translation.
 *
 * @see SensorData::imu()
 * @see IMUEvent
 */
class RTABMAP_CORE_EXPORT IMU
{
public:
	/** @brief Default-constructs an empty sample (null @ref localTransform()). */
	IMU() {}

	/**
	 * @brief Constructs a sample with orientation and motion data.
	 * @param orientation Unit quaternion (qx, qy, qz, qw).
	 * @param orientationCovariance 3×3 row-major covariance about x, y, z (empty if unused).
	 * @param angularVelocity Rad/s about x, y, z.
	 * @param angularVelocityCovariance 3×3 row-major covariance (empty if unused).
	 * @param linearAcceleration m/s² about x, y, z.
	 * @param linearAccelerationCovariance 3×3 row-major covariance (empty if unused).
	 * @param localTransform IMU frame in base coordinates (default identity).
	 */
	IMU(const cv::Vec4d & orientation, // qx qy qz qw
		const cv::Mat & orientationCovariance,
		const cv::Vec3d & angularVelocity,
		const cv::Mat & angularVelocityCovariance,
		const cv::Vec3d & linearAcceleration,
		const cv::Mat & linearAccelerationCovariance,
		const Transform & localTransform = Transform::getIdentity()) :
			orientation_(orientation),
			orientationCovariance_(orientationCovariance),
			angularVelocity_(angularVelocity),
			angularVelocityCovariance_(angularVelocityCovariance),
			linearAcceleration_(linearAcceleration),
			linearAccelerationCovariance_(linearAccelerationCovariance),
			localTransform_(localTransform)
	{
	}

	/**
	 * @brief Constructs a sample without orientation (e.g. no magnetometer / no attitude).
	 * @param angularVelocity Rad/s about x, y, z.
	 * @param angularVelocityCovariance 3×3 row-major covariance (empty if unused).
	 * @param linearAcceleration m/s² about x, y, z.
	 * @param linearAccelerationCovariance 3×3 row-major covariance (empty if unused).
	 * @param localTransform IMU frame in base coordinates (default identity).
	 */
	IMU(const cv::Vec3d & angularVelocity,
		const cv::Mat & angularVelocityCovariance,
		const cv::Vec3d & linearAcceleration,
		const cv::Mat & linearAccelerationCovariance,
		const Transform & localTransform = Transform::getIdentity()) :
			angularVelocity_(angularVelocity),
			angularVelocityCovariance_(angularVelocityCovariance),
			linearAcceleration_(linearAcceleration),
			linearAccelerationCovariance_(linearAccelerationCovariance),
			localTransform_(localTransform)
	{
	}

	/** @return Orientation quaternion (qx, qy, qz, qw). */
	const cv::Vec4d & orientation() const {return orientation_;}
	/** @return 3×3 orientation covariance (row-major, empty if orientation unset). */
	const cv::Mat & orientationCovariance() const {return orientationCovariance_;}

	/** @return Angular velocity (rad/s). */
	const cv::Vec3d & angularVelocity() const {return angularVelocity_;}
	/** @return 3×3 angular velocity covariance (row-major, empty if unused). */
	const cv::Mat & angularVelocityCovariance() const {return angularVelocityCovariance_;}

	/** @return Linear acceleration (m/s²). */
	const cv::Vec3d & linearAcceleration() const {return linearAcceleration_;}
	/** @return 3×3 linear acceleration covariance (row-major, empty if unused). */
	const cv::Mat & linearAccelerationCovariance() const {return linearAccelerationCovariance_;}

	/** @return Transform from IMU frame to base frame. */
	const Transform & localTransform() const {return localTransform_;}

	/**
	 * @brief Rotate motion (and optionally orientation) into the base frame.
	 *
	 * Applies @ref localTransform() rotation to vectors and covariances, then sets
	 * rotational part of @ref localTransform() to identity (translation unchanged).
	 * No-op if @ref localTransform() is null or rotation is identity.
	 * Orientation is updated only when quaternion qx, qy, qz, qw are not all zero.
	 */
	void convertToBaseFrame();

	/**
	 * @brief True when @ref localTransform() is null (placeholder / unset sample).
	 */
	bool empty() const
	{
		return localTransform_.isNull();
	}

private:
	cv::Vec4d orientation_;
	cv::Mat orientationCovariance_;

	cv::Vec3d angularVelocity_;
	cv::Mat angularVelocityCovariance_;

	cv::Vec3d linearAcceleration_;
	cv::Mat linearAccelerationCovariance_;

	Transform localTransform_;
};

/**
 * @class IMUEvent
 * @brief @ref UEvent carrying an @ref IMU sample and timestamp.
 */
class IMUEvent : public UEvent
{
public:
	/** @brief Default-constructs an event with zero stamp. */
	IMUEvent() :
		stamp_(0.0)
	{}
	/**
	 * @brief Constructs an event with IMU data and stamp.
	 * @param data IMU sample.
	 * @param stamp Timestamp in seconds.
	 */
	IMUEvent(const IMU & data, double stamp) :
		data_(data),
		stamp_(stamp)
	{
	}
	/** @return Event type name for the utilite event system. */
	virtual std::string getClassName() const {return "IMUEvent";}
	/** @return IMU payload. */
	const IMU & getData() const {return data_;}
	/** @return Timestamp in seconds. */
	double getStamp() const {return stamp_;}

private:
	IMU data_;
	double stamp_;
};

}

#endif /* IMU_H_ */