if robot slowly roate, why imu data do not change.

[1chick]

if robot slowly roate, why lpms imu data do not change. i cannot copy with it , somebody help me please my device model is LPMS UTTL2.

[dmiklic]

Please provide some more details.

1) Which data exactly are you looking at? Velocity? Acceleration? 2) How do you know that it does not change, i.e., how are you observing the data? With rostopic echo or are you plotting it? 3) How slowly is the robot actually rotating? If it is very slow, than it is to be expected that velocity and acceleration changes will be minimal. 4) Do you observe the same behaviour when monitoring the data in the LPMS Windows GUI application?

[1chick]

@dmiklic thank your so soon reply。

1. i just look at imu_msg.orientation.w
2. i open rviz observe the imu/data topic, set box show 3.i control the robot as 0.4 rad/s rotation, but imu_msg.orientation.w data keep not change,i set 0.7 rad/s make change, 4.also i use LPMS windows GUI application check it , it got same reuslt .

i think whether or not change some params.

[dmiklic]

You should look at imu_msg.angular_velocity as that part of the message holds information about the speed of robot rotation.

Looking only at imu_msg.orientation.w is not a good indication of anything, as this is only one component of the orientation quaternion, i.e., not all changes in orientation will have a major impact on this particular component.

If the behavior is the same as when you use the Windows GUI application, I'd say that there is nothing wrong with your ROS setup. You cahn also try to visualize what is really going on using rviz_imu_plugin.

[1chick]

@dmiklic yes i look at angular_velociy is normal, the value keeps some little change,(i,e, 0.3399rad/s),maybe accelermeter is zero, but i change it keeps 0.7rad/s almost i can get orientation.w is changed, and if accelermeter change orientation.w is normal.

[dmiklic]

This sounds like normal behavior to me, but maybe there are some sensitivity issues. Maybe @TobiSchluter can share some more insight.

[TobiSchluter]

I pointed our sensor guys to this thread but please don't hesitate to contact us as indicated on our webpage. That makes it easier for us to reference the calibration documentation we kept on your sensor etc. There are a variety of settings affecting the orientation integration, please see our manual following p. 28 and let us know if any of the settings help.

In general, if you have requests concerning the sensors this is not the right place. dmiklic et al were kind enough to share their ROS driver with the world but your issue seems to be with the LpSensor library or the sensor itself. We all love it when somebody else does our work, but when we're asked to do somebody else's work our feelings usually are less bright :-)

Looking forward to hearing from you.

[TobiSchluter]

ps my colleagues seem to agree that your issue sounds like the gyroscope autocalibration kicking in because the sensor thinks it is at rest. You can turn this off in LpmsControl as indicated in the screenshot you find below: Alternatively, you can use the LpSensor library to achieve the desired effect.

Documentation for the autocalibration can be found on p. 30 of the manual.

[1chick]

@TobiSchluter yes i can check it changed when slowly move. thanks

[TobiSchluter]

@1chick Good to hear. If there are any other questions, please feel free to contact us.