UM7 Calibration Procedure

[Michael]

Hi All,

We have updated some info on the Redshift web site.

UM7 datasheet (2MB pdf)
Datasheet V1.6, released 1 October 2016, for the Redshift Labs UM7 orientation sensor
https://www.redshiftlabs.com.au/media/documents/UM7%20Datasheet_v1-6_10.1.2016.pdf
UM7 Quick-Start Guide
https://www.redshiftlabs.com.au/um7-quick-start-guide
UM7 U71D, U72A Calibration Procedure explained
https://www.redshiftlabs.com.au/um7-calibration-procedure

Please let us know if you have any issues.

Regards
The Redshift Team

[Benjamin]

Hi,

Thanks for this documentation !

It required to calibrate the sensor at each power on ? or we can calibrate the sensor one time and never recalibrate them ?

Thanks in advance,
Best regard,

[Michael]

Hi Benjamin,
Usually you wont need to calibrate a unit if its been factory calibrated.
However because the unit is factory calibrated either in Australia or the USA, the magnetic field will be different in your locality, I assume France?
I would test the unit and see if it is working as expected if you are getting some strange results, definitely re calibrate.
Once you have done a successful calibration you shouldn’t need to do it again. One thing to note is: I would recommend resetting the EKF upon boot from within your application.
When a reset of EKF is performed make sure the robot and or sensor if attached to robot, is not moved until the EKF converges this can take about 20-30 seconds. 
You do not necessarily have to reset the EKF upon boot but it may help especially if the sensor has been exposed to ferrous materials.

some useful information.

If you are seeing a saw-tooth waveform on the yaw output from within the serial interface software, then the magnetic field has been disturbed and this can blow the yaw errors out exponentially. I would recommend re-calibrating your unit following the steps outlined here:
https://www.redshiftlabs.com.au/um7-calibration-procedure

When you first start the unit up (after calibration), make sure you don’t bump the unit, allow a small amount of time (20 – 30 seconds) for the kalman filters to converge, if you move the unit upon boot or after resetting the EKF, it can also loose its heading and go haywire for up to 60 seconds until the Kalman filter re-converges.

Tuning the Kalman filter.
You can minimize dynamic distortions (i.e. cables carrying variable current loads) that will affect the yaw data and if they can be accounted for. You can lower the magnetometer variance and bump up the gyro variance (i.e. gyro:1, acc=0.01, mag=0.0002) to rely less on the magnetometer.

To do this fire up the serial interface software.
Connect to your device.
Click In the configurations tab, now press Read
Now tick the checkbox named Show advanced settings
There should be a drop down list called Sensor variance settings
You can tune the EKF from here using the instructions mentioned above.

To enable the Magnetometer.
Click In the configurations tab, now press Read
Locate the Filter Settings drop down list.
Make sure that Magnetometer Updates Enabled is set to Enabled

Videos
https://www.redshiftlabs.com.au/um7-calibration-procedure
File downloads
Resources
UM7 datasheet (2MB pdf)
•        Datasheet V1.6, released 1 October 2016, for the Redshift
Labs UM7 orientation sensor
https://www.redshiftlabs.com.au/media/documents/UM7%20Datasheet_v1-6_10.1.2016.pdf

UM7 Quick-Start Guide
https://www.redshiftlabs.com.au/um7-quick-start-guide

UM7 U71D, U72A Calibration Procedure explained
https://www.redshiftlabs.com.au/um7-calibration-procedure

Recommended links
https://www.redshiftlabs.com.au/serial-interface-software

Redshift Labs UM7 orientation sensor product page
•        Additional information and resources for the UM7
orientation sensor can be found on its product page on the Redshift
Labs website.

https://www.redshiftlabs.com.au/sensors/um7-orientation-sensor

UM7 Content library
•        The UM7 content library provides some background on how
their orientation sensors work, including the principles and
mathematics behind their operation.

https://www.redshiftlabs.com.au/um7-content-library

Support Forum
Redshift Labs is presently supporting the CH Robotics support forum,
the best place to get in-depth technical support for the UM7.

Regards,
Michael Malloy
http://www.redshiftlabs.com.au

[Author]

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