Sensor Fusion

The SensorFusion module interacts with the sensor fusion algorithm running on MetaMotion boards. When using the sensor fusion algorithm, it is important that you do not simultaenously use the Accelerometer, Gyro, and Magnetometer modules; the algorithm configures those sensors internally based on how you configure the sensor fusion algorithm.

To activate the sensor fusion algorithm, first set the fusion mode and data ranges, then call start with the desired algorithm data, enumerated by the DataOutput enum.

Mode

The sensor fusion algorithm has 4 fusion modes, listed in the below table:

Mode	Description
NDoF	Calculates absolute roeintation from accelerometer, gyro, and magnetometer
IMUPlus	Calculates relative orientation in space from accelerometer and gyro data
Compass	Determines geographic direction from th Earth’s magnetic field
M4G	Similar to IMUPlus except rotation is detected with the magnetometer

The mode is set via a ConfigEditor object which is retrieved by calling configure.

import com.mbientlab.metawear.module.SensorFusion;

// Set mode to NDoF, accel range to +/-8G
// Note that accel range is not set through the Accelerometer module
final SensorFusion sensorFusion = mwBoard.getModule(SensorFusion.class);
sensorFusion.configure()
    .setMode(SensorFusion.Mode.NDOF)
    .setAccRange(SensorFusion.AccRange.AR_8G)
    .commit();

Data

The sensor fusion algorithm provides raw acceleration, rotation, and magnetic field values along with quaternion values and Euler angles. Furthermore, the source of acceleration can be separated into gravity and linear acceleration and both values are also provided. Keep in mind that each sensor fusion mode has different sets of available data and produces it at different rates.

Mode	Acc	Gyro	Mag
NDoF	100Hz	100Hz	25Hz
IMUPlus	100Hz	100Hz	N/A
Compass	25Hz	N/A	25Hz
M4G	50Hz	N/A	50Hz

Also note that the units and type casting of the sensor fusion data is different for each type of data..

Data	Units	Casted Data
Acceleration	g	CorrectedCartesianFloat
Rotation	deg/s	CorrectedCartesianFloat
Magnetic Field	uT	CorrectedCartesianFloat
Quaternion	None	Quaternion
Euler Angles	degrees	EulerAngle
Linear Acc	g	CartesianFloat
Gravity	g	CartesianFloat

// stream quaternion values from the board
sensorFusion.routeData().fromQuaternions().stream("quaternion").commit()
    .onComplete(new CompletionHandler<RouteManager>() {
        @Override
        public void success(RouteManager result) {
            result.subscribe("quaternion", new MessageHandler() {
                @Override
                public void process(Message msg) {
                    Log.i("example", msg.getData(SensorFusion.Quaternion.class).toString());
                }
            });
            sensorFusion.start(SensorFusion.DataOutput.QUATERNIONS);
        }
    });