Changes in accessing inertial data

[Nicogene]

Hi @robotology/all-robotology-developers ,

This issue is to inform about the new "canonical" way for accessing the inertial data.

Preface

robotology/yarp#1586 introduced multiple analog sensors interfaces and related devices. In particular the devices are:

• multipleanalogsensorsserver
• multipleanalogsensorsclient
• multipleanalogsensorsremapper

In a few words, they have been designed for exposing and accessing the multiple analog sensors over a network, and for combining multiple devices in a single device (remapper).

In the past the inertial sensors (e.g the IMU in the head) was wrapped by the ServerInertial, that publish the data as a Vector of 12 elements:

0  1   2  = Euler orientation data (X, Y, Z)  global frame representation.
3  4   5  = Calibrated 3-axis (X, Y, Z) acceleration data
6  7   8  = Calibrated 3-axis (X, Y, Z) gyroscope data
9 10  11  = Calibrated 3-axis (X, Y, Z) magnetometer data

One of the major headache was to remember every time which was the indices of the vector corresponding to a certain type of data. Instead, the multipleanalogsensors devices allow to retrieve the specific type of data the client code needed.

Example of usage in user code

To retrieve the inertial data through this new family of devices it is needed to instantiate in the code a Polydriver of type multipleanalogsensorsclient and then call the view of the interfaces regarding the inertial data you need, e.g.:

// Open the device driver and view the interfaces
IThreeAxisGyroscopes* iGyro;
IThreeAxisLinearAccelerometers* iAccel;
Property mas_conf{{"device", Value("multipleanalogsensorsclient")},
	         {"remote", Value(remoteInertialName)},
                 {"local",  Value(localInertialName)},
                 {"timeout",Value(imuTimeout)}};

if (!(mas_client.open(mas_conf)))
{
	yError("Unable to connect to %s!",remoteInertialName.c_str());
	yError("Unable to open the MAS client");
	return false;
}

if (!(mas_client.view(iGyro)) ||
   !(mas_client.view(iAccel))) {

	yError("View failed of the MAS interfaces");
	return false;
	}

// Retrieve the data

bool ok = true;
Vector gyro, acc;
double ts{0.0};
ok &= iGyro->getThreeAxisGyroscopeStatus(0) == MAS_OK;
ok &= iGyro->getThreeAxisGyroscopeMeasure(0, gyro, gyroTs);

if (!ok) {
    yError()<<"unable to get gyro";
    return false;
}

ok &= iAccel->getThreeAxisLinearAccelerometerStatus(0) == MAS_OK;
ok &= iAccel->>getThreeAxisLinearAccelerometerMeasure(0, acc, ts);

if (!ok) {
    yError()<<"unable to get acceleration";
    return false;
}

This example accesses only to the gyro and accelerometer data, but there are other interfaces to retrieve also the euler angles, magnetometer etc (see here)

Note that for the remote parameter of the multipleanalogsensorsclient you have to specify the same name used as local parameter in the multipleanalogsensorsserver that exposes the inertial data

Changes in icub-related software

⚠️ The changes affect for now only the devel branches.

This new paradigm has been adopted in iKinGazeCtrl and imuFilter.

iKinGazeCtrl

The iKinGazeCtrl if the imu::mode parameter is set to on, tries by default to attach the multipleanalogsensorsclient to the multipleanalogsensorsserver with the prefix port name /icub/head/inertials, according to the convention used for the imu of other parts.

In alternative, as before, it is possible to specify the imu::source_port_name to attach to a different publisher of inertial data.
For example the source_port_name of the imuFilter is simply /imuFilter.

imuFilter

For its nature of "man-in-the-middle" that takes the data, filter it, and then publish them filtered, to adopt this new paradigm it has been converted as device driver (robotology/icub-main@9a46fb2).

In this comment is explained how to run it through yarprobotinterface through the yarpdev executable.

Changes in robots-configuration

This PR added the required changes in the xml files in order to wrap the inertial sensors with the multipleanalogsensors and run the new version of imuFilter.

How this impacts my work

Actually the "old" /icub/inertial of the ServerInertial is still exposed, then your application can still get the imu data in the old way(see http://wiki.icub.org/wiki/Inertial_Sensor).
The only problem you may have is if you update robots-configuration and then not icub-main, yarprobotinterface would fail since it has not the imuFilter device. To solve this, simply update also icub-main.

Moreover imuFilter is not anymore a module, and it is opened by the yarprobotinterface, then it may be possible that you have to remove it from the xml files of your yarpmanager applications.

For any further questions or doubts, feel free to contact me or the author of the MultipleAnalogSensorsInterfaces, @traversaro .