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obtaining IMU linear acceleration without activating a GNSS

asked 2018-07-13 06:06:56 -0500

updated 2018-07-18 03:55:15 -0500

Hi everyone,

I'm using ROS Indigo on Ubuntu 14.04 LTS and advanced_navigation_driver. I used the command

rostopic echo /an_device/Imu

to see the sensor_msgs/Imu messages published by my IMU device and noticed that the linear acceleration (x,y,z) is always zero when I don't activate a GNSS previously -- and always non-zero otherwise.

I wonder if there is a way to obtain the real, non-zero linear acceleration without activating any GNSS. If so, how?

Thanks in advance!

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Did you check to make sure this behavior is NOT a hardware problem? E.g, imu measurements are triggered by GPS signal (for synchronizing timestamp?)

tuandl gravatar image tuandl  ( 2018-07-13 07:48:23 -0500 )edit

Indeed it's a hardware problem. My IMU device requires the navigation filter to be initialised so that position, velocity and acceleration values can be obtained

laizwithzed gravatar image laizwithzed  ( 2018-07-16 06:03:53 -0500 )edit

If it's a hardware problem (i.e., not something related to the an_driver) I'm not sure how much we can help. I'd be surprised if there wasn't a way to send packets with the raw IMU data when no GNSS is present, though.

stevejp gravatar image stevejp  ( 2018-07-16 08:25:24 -0500 )edit

In fact, the device requires the navigation filter to be initialised so that position, velocity and acceleration values can be obtained, but it can also be manually initialised when a GNSS fix is not available using the Spatial Manager manual initialisation dialogue

laizwithzed gravatar image laizwithzed  ( 2018-07-16 10:53:26 -0500 )edit

@stevejp mentioned this is a hardware problem then there is nothing much that we can do to help. Maybe you should try to look at the SDK to see if there is any function that captures raw IMU stream without invoking anything else. Good luck! (or just email the manufacturer for help :d)

tuandl gravatar image tuandl  ( 2018-07-18 04:16:08 -0500 )edit

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answered 2018-07-18 04:27:30 -0500

updated 2018-07-18 04:54:02 -0500

I found out that there are two ways of initialising my IMU device (Spatial) when a GNSS fix is not available:

  1. using the Spatial Manager manual initialisation dialogue
  2. writing a code to send the position to the device inside the External Position package

The company's webpage provides a Reference manual and an SDK with example code.

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Asked: 2018-07-13 06:06:56 -0500

Seen: 125 times

Last updated: Jul 18 '18