KoP Gyro and Accelerometer Placement

[DavidB]

My question in regards to the KoP Gyro and Accelerometer. Basically I want

to know how close the center of the rotation of the robot do they need to be

to be accurate? Does it need to be dead center or can it be to the side at all?

Basically what is the optimal location to place them. Also is it best to have

them lower on the robot, at about drive train level? Thank you for any help you

can provide.

DavidB

[Alan Anderson]

The accelerometer will falsely sense rotation as acceleration more strongly as it is mounted farther from the center of rotation of the robot.

The yaw rate sensor (gyro) will be increasingly inaccurate as centrifugal force from rotation affects its response.

Mounting the accelerometer higher will result in slightly less stable readings as the robot rocks.

We're mounting ours kind of low, reasonably close to the robot center line, near the rear of the robot.

[nathanww]

It depends on what you're doing with them--our accelerometer is way off to the side, but the only thing we use it for is traction control and if we have enough traction to turn fast enough to affect the reading, we don't really need the traction control.

Another consideration is electrical noise--avoid putting it next to something that spits out a lot of EM(like the motors or PDU), as this can really noise up your readings.

[Wicked]

So what would be a good gyro placement for detecting the angular position of the robot?

Our gyro's giving incorrect readings; for example, if we turn the robot 90 degrees, the gyro gives us 45.

[Alan Anderson]

Originally Posted by Wicked

Our gyro's giving incorrect readings; for example, if we turn the robot 90 degrees, the gyro gives us 45.

The 2010 kit gyro has an output of 6 mv/deg/s. I believe the default value in the program is 12.5 mv/deg/s. You need to change the program to match the actual device you're using.

[DarKCroNo]

Should the sensors also be as parallel to the floor as possible? specifically the accelerometer?

[omalleyj]

Originally Posted by DarKCroNo

Should the sensors also be as parallel to the floor as possible? specifically the accelerometer?

Yes. If either isn't parallel they will sense gravity as acceleration. This can be compensated for by setting the zero point with the actual at-rest readings. The gyro does this automatically on instantiation now.