Auto levelling platform

Hi everyone, I'm intending to make an auto levelling platform which is always perpendicular to the Earth and I was wondering if I could do this using gyros? But I don't know if digital gyros know which way is up or if they just know whether their orientation has changed relative to whatever it was when they were turned on.

Thanks in advance
Andrew

Most gyros only output the amount of change from one moment to the next (in degrees per second). A tri-axial accelerometer would be more appropriate for leveling as it uses gravity as a reference.

Gyros don't know which way is UP. They just tell you how fast you are rotating.

Accelerometers can tell you which way is UP when they are at rest. When accelerating they give you the sum of the gravity vector and your acceleration vector.

A magnetometer give you your orientation relative to the local magnetic field. If you get the tilt of the local magnetic field by comparing the magnetometer reading to the accelerometer reading at rest you can use that to determine which way is UP in a fairly wide area.

If you only need to know UP when not accelerating then an accelerometer alone will be sufficient. If you need to know where UP is even when going around turns, use the accelerometer and magnetometer.

Ah ok, I thought it was the other way round with accelerometers knowing the rate of change but not the actual orientation.

So with just an accelerometer, I could level the platform? Other than initially rotating in order to become level this platform won’t be moving again.

self levelling platform.png