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How to Use Inertial-Link IMUs with the imu_node

Compiling

Start by getting the dependencies and compiling the driver.

$ rosdep install microstrain_3dmgx2_imu
$ rosmake microstrain_3dmgx2_imu

Powered On and Plugged In

Make sure that your USB imu is plugged in and the power light is on.

Configuring the IMU

Make sure that the imu_node will be able to access the imu.

Start by listing the permissions of the IMU:

ls -l /dev/ttyUSB0

You will see something similar to:

• crw-rw-XX- 1 root dialout 188, 0 2009-08-14 12:04 /dev/ttyUSB0

If XX is rw: the usb device is configured properly.

If XX is --: the usb device is no configured properly and you need to:

sudo chmod a+rw /dev/ttyUSB0

Starting a roscore

For the imu_node to work properly, a ros core must be running. In a new terminal:

$ roscore

Running the imu_node

In a new terminal, run the imu_node:

$ rosrun microstrain_3dmgx2_imu imu_node

You will see something similar to:

• [ INFO] 1250276678.466059000: Started node [/imu], pid [17125], bound on [aqy], xmlrpc port [49515], tcpros port [44773], logging to [/u/mwise/ros/ros/log/imu_17125.log], using [real] time
  [ INFO] 1250276679.540144000: Connected to IMU [    Inertia-Link] model [            4200] s/n [            3046] options [       5g 300d/s]
  [ INFO] 1250276679.540247000: Calibrating IMU gyros.
  [ INFO] 1250276689.650297000: IMU gyro calibration completed.
  [ INFO] 1250276689.650416000: Initializing IMU time with offset 0.000000.
  [ INFO] 1250276689.664184000: IMU sensor initialized.

Note: If your IMU is at a port other than /dev/ttyUSB0, you could explicitly specify the port parameter, for example:

$ rosrun microstrain_3dmgx2_imu imu_node _port:=/dev/ttyUSB1

Viewing the data

To see that everything is working and data is being published to ros, in a new terminal:

$ rostopic echo imu/data

You will see something similar to:

• header: 
    seq: 1791
    stamp: 1263496141218770057
    frame_id: imu
  orientation: 
    x: -0.00113008373396
    y: 0.00770460351395
    z: 0.379699384935
    w: 0.925077162566
  orientation_covariance: [0.0012250000000000002, 0.0, 0.0, 0.0, 0.0012250000000000002, 0.0, 0.0, 0.0, 0.0012250000000000002]
  angular_velocity: 
    x: 0.005341142416
    y: -0.00330266845413
    z: -7.2395623647e-06
  angular_velocity_covariance: [2.8900000000000004e-08, 0.0, 0.0, 0.0, 2.8900000000000004e-08, 0.0, 0.0, 0.0, 2.8900000000000004e-08]
  linear_acceleration: 
    x: 0.438507700588
    y: 0.012467633853
    z: -9.82538275752
  linear_acceleration_covariance: [0.0096040000000000014, 0.0, 0.0, 0.0, 0.0096040000000000014, 0.0, 0.0, 0.0, 0.0096040000000000014]
  ---

Move the IMU around to see the data change.

Note that the covariances have been set to values consistent with the manufacturer datasheet. These covariances are very pessimistic and you will most likely be able to use smaller values in your application.