I'm starting to get some empirical data on the MPU9150. It is part of a custom autopilot that I have developed. I had some initial settings and results, but now I'm trying to squeeze more performance out of it. Namely, I would like it to operate in a piston powered aircraft with a giant paint shaker attached to it.
My MO is to put such a sensor on a shaker table, read raw data, and then optimize filters by post processing this data. Finally, these filters, are placed into the microcontroller.
To get to the core of my question, I'm curious about how the sampling rate is tied to the cuttoff frequency, and if there is some optimal relationship there based on the order of the filter.
I would prefer in this case to just put the raw (read) data into a kalman, and not do any oversampling myself. I see the ArduPilot code uses a 98Hz c/o DLPF, with a 200 Hz sampling freq. Why set the frequency so high above that of an aircraft? I think the ArduPIlot attitude filter may run at 50Hz. I can see there the Nyquist factor going between the three stages. Maybe I just have a different approach. In the past, when using analog sensors, I've set the analog LPF c/o freq to about 10Hz or so for fixed wing aircraft.
So does anyone know the order of the cuttoff filters in this chip? Or if you potentially stifle the performance of one by matching an inappropriate sampling freq with a cutoff freq?
I will share the settings I arrive at through my analysis, but would also really appreciate any input.
A couple of examples attached
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