AHRS sensor (IMU) for outdoor antenna

Thread Starter

Tantalum

Joined Mar 12, 2023
1
Hello

I have a high directional 4G outdoor dish antenna, and I wanted to fix it on a Diseqc motor to make it rotate horizontally (~150°) and perhaps also add a small linear actuator to optimize the vertical inclination (+/-20°).

But I wanted also to add an IMU in order to get information about the orientation of the antenna.
A +/-2° accuracy is good enough.
Actually, I only need the geographical orientation (like a compass) and possibly the vertical inclination.

Now I have following questions:

1. Do I need a full AHRS sensor (= accelerometer + gyroscope + magnetometer + fusion algorithm) or a magnetometer is enough? Does the accelerometer/gyroscope/magnetometer data adds accuracy to the calculated geographical heading of the fusion algorithm?

2. Since the antenna will only be able to move (slowly) 150°H and 20°V I won’t be able to calibrate the sensors after every power-up of the device. Is that an issue with such device? Is a one-time calibration (before final mounting) good enough?

3. Is this Chinese AHRS (based on a RM3100 magnetometer, which has 3 external coil antennas) module overkill? Or is a BNO055 good enough for my purposes?


Chinese AHRS (HWT901B-RS485):
https://www.aliexpress.com/item/1005002977359131.html


Inside:


The mag sensor inside:



Alternative, the Bosch BNO055 with integrated fusion algorithm:




Thank you for your help
 

nsaspook

Joined Aug 27, 2009
13,438
For your application the Chinese AHRS sensor looks OK with a simple UART or CAN interface. If I were building a custom board I would pick the Bosch device. I've never had issues using Bosch IMU's (availability is a problem) and their datasheets are very complete with driver examples on github for custom software designs. They both have Quaternion sensor outputs that make tracking 3D movements compatible with lots of modern graphic software methods.


https://blog.endaq.com/quaternions-for-orientation

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