Heading as a function of wheel rotations

AI Thread Summary
The discussion revolves around calculating the change in heading for a robot with two motorized wheels and a skid wheel. The user proposes a formula for ΔHeading based on wheel rotations but questions its accuracy due to varying axes of rotation. A response clarifies that the concerns about the axis of rotation are unfounded, as the effects cancel out when considering the movement of both wheels. Specifically, when one wheel is stationary, the effective radius of the turn remains consistent, allowing for accurate heading calculation. The conversation emphasizes that the derived formula can still be valid despite initial doubts.
fishingspree2
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Hello, I have a three robots which consists of two motorized wheels and a skid wheel. The two motorized wheels are on the front of the robot. I am trying to find the change in heading of the robot based on the previous state.

I have found out that ΔHeading = [(ΔDL-ΔDR)*radius of wheels]/wheelbase. where ΔD is the difference in wheel rotations between ti and ti-1. I have a feeling that this is not correct, since the axis of rotation changes depending on the angular velocity of each wheel. For example, if one of the wheels is at rest while the other rotates, then the axis of rotation of the robot is the wheel at rest. If the two wheels are rotating in opposite direction, then the axis of rotation of the robot is halfway between the two wheels. The formula I have derived does not take this into account.

Can anyone point me in the right direction?
Thank you
 
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fishingspree2 said:
Can anyone point me in the right direction?
The effect you are concerned about is not a problem because it actually cancels.

When the radius of the turn is in the midway between the wheels, one wheel moves forward half the distance, while the other moves backwards half the distance. The difference is still the true heading.
 

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