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HOWTO

Tips on ROS for the operation of FXIMU

Load parameters

rosparam load config/fximu_params.yaml
rosparam load config/fximu_params_000.yaml

Notice: roscore must be running

Run rosserial

rosrun rosserial_python serial_node.py _port:=/dev/ttyACM0 _baud:=230400

Create /dev/fximu

If you are using more than one serial device, the ordering of the ports might change after reboot, so creating a symbolic link from /dev/fximu to actual serial port /dev/ttyACMX is useful. To accomplish this, first, obtain the USB serial id of your FXIMU by executing the following command:

udevadm info -a -n /dev/ttyACM0 | grep '{serial}'

It will return:

ATTRS{serial}=="0000000A"
ATTRS{serial}=="0000:00:14.0"

In this case, the usb serial id is 0000000A, which is a string.

Create a new rules file by:

sudo nano /etc/udev/rules.d/99-usb-serial.rules

Add the following inside the file, after replacing the FXIMU usb serial id:

KERNEL=="ttyACM*", ATTRS{idVendor}=="1cbe", ATTRS{idProduct}=="0002", ATTRS{serial}=="0000000A", SYMLINK+="fximu"

Restart the computer. You will see that once the FXIMU is attached, the udev will create a symbolic link /dev/fximu that points to the correct serial port. After that, in your launch files you can use /dev/fximu

Run static transform publisher for rviz

rosrun tf static_transform_publisher 0.0 0.0 0.0 0.0 0.0 0.0 map imu_link 100

Visualize with RVIZ

Note that rviz imu plugin is required to visualize imu data. Click Add on rviz, then select rviz_imu_plugin then type 'imu/data' as topic in the visualization window.

View IMU data

rostopic echo /imu/data

View magnetometer data

rostopic echo /imu/mag

Measure frequency of output data

rostopic hz /imu/data

Plot IMU data

rqt_plot /imu/data/linear_acceleration

linear acceleration plot

rqt_plot /imu/data/angular_velocity

angular velocity plot

rqt_plot /imu/mag/magnetic_field

magnetic field plot

Measure Gravity

First launch FXIMU, then:

roscd fximu/scripts
./measure_gravity.py

It will print the value of gravity constant. Make sure the FXIMU is fixed and does not move before running.Wait at least 1000 cycles for the averaging filter to converge.

Measure Thresholds

FXIMU detects stationary mode by using number of thresholds. Once the device is in stationary mode, it self calibrates sensor biases. To measure the thresholds for your imu follow the following procedure:

roscd fximu/scripts
./measure.thresholds.py

This will print measurements, if the thresholds are exceeded. So depending on the output, change the following lines accordingly:

self.kAccelerationThreshold = 0.19
self.kAngularVelocityThreshold = 0.055
self.kDeltaAngularVelocityThreshold = 0.033

kAccelerationThreshold is the threshold for accelerometer values.

kAngularVelocityThreshold is the threshold for the gyro values.

kDeltaAngularVelocityThreshold is the threshold for the derivative of gyro values.

Tune these manually, until the program measure_thresholds does not produce any output.

Disable Modem Manager

ModemManager service that is default on ubuntu, probes the newly added serial ports, which keeps it busy for few second. To overcome this delay turn off or uninstall the ModemManager service.

Licenses

tr000003 license