Measuring accelerations on surfaces that are not parallel

We need to measure accelerations on a vehicle chassis and another structure that is attached to the chassis.

The chassis is nominally level but the surfaces of the frame on which we also measure accelerations are not. Locations at which the accelerations will be measured are marked in the attached image.

Blue = Chassis = Horizontal

Yellow = Frame location 1 = 20 degrees below horizontal

Grey = Frame location 2 = 46 degrees below horizontal

We will use an 3 axis accelerometer connected to analog inputs 1,2 and 3 on our Dewe43

We need to compare accelerations in the Z axis at each of these three locations. Obviously the chassis measurements will be easy, but is there an easy way to do this for the other two locations?

Hi,

you said that you're going to use a triaxial accelerometer for three analog inputs on your DEWE-43, but your image shows three separate locations, so I'm not sure if you actually have 3 triaxial accelerometers, or 3 single axis accelerometers. I'll assume that you have 3 separate accelerometers that can measure acceleration in one direction.

I've marked the axes of a Cartesian coordinate system on your image. Let's say that you're measuring acceleration in the direction that's marked with the orange arrows. The first signal should already be in the z direction. The signal from the yellow frame is being measured at an 20 degree angle, so we should multiply it by cos(20°) to get the z component. The same is true for the signal coming for the grey frame, only the angle is 46° this time.

DEWESoft's cos() function needs to be passed radians, so you should multiply your degrees by pi/180 to make the conversion. Would this work as a comparisson?