This forum uses cookies
This forum makes use of cookies to store your login information if you are registered, and your last visit if you are not. Cookies are small text documents stored on your computer; the cookies set by this forum can only be used on this website and pose no security risk. Cookies on this forum also track the specific topics you have read and when you last read them. Please confirm whether you accept or reject these cookies being set.

A cookie will be stored in your browser regardless of choice to prevent you being asked this question again. You will be able to change your cookie settings at any time using the link in the footer.

Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
IMU WT901C by Wit-Motion
#1
Hello,

Is it possible to use the imu WT901C

This one is connected via an RS232-USB adapter to the RPi.

Pypilot seems to detect it but not stable. (Pypilot sees the IMU, click refresh it is not seen anymore, click refresh is is back ...)

Any idea ?

Regards,

Ralph

   

   
Reply
#2
pypilot detects imu on i2c, so it must have detected something previously connected.

something on a serial port especially usb is not supported. The biggest issue is lag time followed by reliability.

Despite this, it could be interesting to try for comparison purposes, but my understanding is, this just has a more sensitive compass?

The limiting factor of the imu is the quality of the gyro, not the compass sensors even though neither are all that great in the 9250 series.
Reply
#3
(2022-12-02, 01:48 PM)seandepagnier Wrote: The limiting factor of the imu is the quality of the gyro, not the compass sensors even though neither are all that great in the 9250 series.

This page lists several single- and dual-chip IMU solutions:

  https://github.com/seandepagnier/RTIMULi.../README.md

Which are suitable for PyPilot?
Reply
#4
All are supported as well as icm20948, but I have the best results and experience with icm20948
Reply
#5
(2022-12-04, 03:38 PM)seandepagnier Wrote: All are supported as well as icm20948, but  I have the best results and experience with icm20948

I would like to look at different IMUs, including one and two chip solutions.  I'm happy to write driver code.  What I need to know though, is in a black box sense, what are PyPilot's requirements?  What does it need of the IMU?  

For example (and I'm making this up), "PyPilot needs 3 axis accelerometer info (for translation), 3 axis gyroscope info (for rotation), and 3 axis magnetometer info (for heading).  The update rate needs to be at least XXXHz, with at least Y sensitivity and less than Z noise".  I'd like to be able to assess "this solution might work with PyPilot, that solution won't".

Thoughts?
Reply
#6
it is not so simple as a specific noise level.

Yes it only needs raw sensor readings for accelerometer, gyro and compass. 20 times per second but typically 100 readings are taken every second and averaged for a lower rate of 20hz.

From my testing, magneto resistors have much much higher sensitivity than the hall sensors but worse repeatability so for this reason alone, hall sensors are preferred since they are already good enough. As for noise levels, it could even be that a particular module cross couples data lines, eg: using SPI instead of I2C has higher noise. It is difficult to say without actual testing.

What I can say.. is most, if not all imu units available will work to some degree. I would prefer better gyros above better compass/accel, but to know how well it works needs testing. On a larger heavy/slow boat it may be difficult to tell the difference if the sensors aren't as good. It really depends.

It is like asking how many megapixel camera is good enough to take a picture of a person.
Reply


Forum Jump:


Users browsing this thread: 1 Guest(s)