Calibration of a Gyro

[Chris Texas]

Hey guys,

I'm trying to calibrate a Gyro, and the Gyro is located on the back of the car with 3-axis accelerometers. The problem I'm having is trying to transfer the Gyro's axis from the rear of the car to the CG of the car. I've looked through a few dynamics books and can only find out how to transfer velocity and accelerations to the center of the car. Maybe, I'm over complicating it, but has anyone every done this calibration or have an idea how to transfer a rotational acceleration from one axis to another. Thanks for any help.

Chris Drew



Junior Engineer Racers Edge Motorsports '11
Team Captain UT Formula SAE '10-11
Suspension and Chassis Lead '10-11
UT Grunt '06-11

[Chris Texas]

Hey guys,

I'm trying to calibrate a Gyro, and the Gyro is located on the back of the car with 3-axis accelerometers. The problem I'm having is trying to transfer the Gyro's axis from the rear of the car to the CG of the car. I've looked through a few dynamics books and can only find out how to transfer velocity and accelerations to the center of the car. Maybe, I'm over complicating it, but has anyone every done this calibration or have an idea how to transfer a rotational acceleration from one axis to another. Thanks for any help.

Chris Drew



Junior Engineer Racers Edge Motorsports '11
Team Captain UT Formula SAE '10-11
Suspension and Chassis Lead '10-11
UT Grunt '06-11

[Crispy]

Angular velocity and angular acceleration are constant over a rigid body. No transformation of these quantities is required when an axis system is simply translated from one point on a rigid body to another.

Search: "wiki Rigid body"
Read the "Linear and angular velocity" section

[Kirby]

This stuff is typically beyond my sphere of knowledge.

But do you mean you are trying to locate the respective centers of pitch, yaw and roll from the output of your gyro?

[Bobby Doyle]

Crispy is correct. You can assume that your frame is a rigid body - perfectly good assumption in this case. An angle at the back is the same as an angle at the front. Same goes for the time derivatives.

It should go without saying that this is not the case for your accelerometers. I suggest placing those as close to the vehicle CG as you can.

[BillCobb]

Calibration of a gyro is often best done on a machine called a rate table. This is essentially a turntable that can be operated at several rpm settings and has decent slip rings on it to transfer power and signal.. It needs to be done at several settings because gyros are notorious for nonlinearities, especially at low rates. If its a real gyro as opposed to a solid state chipset, then you need to watch drift and stiction characteristics very closely.

[flavorPacket]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Crispy:
Angular velocity and angular acceleration are constant over a rigid body. No transformation of these quantities is required when an axis system is simply translated from one point on a rigid body to another.

Search: "wiki Rigid body"
Read the "Linear and angular velocity" section </div></BLOCKQUOTE>

When the car rolls, then what?