Encoders and Rover Wheels

[nathanww]

The only ting we're using encoders for is detecting slipping wheels. The actual navigation is being handled by a combination of vision processing(for obstacle avoidance) and inertial nav(for absolute position)

[whitetiger0990]

Plain and simple, if you put an encoder an a drive wheel and it slips, the encoder reading will be inaccurate. It's next to impossible to just throw code at it to deal with slippage.

If you're dead set on using encoders to measure robot velocity and distances and etc, then it's best to put the encoder on a nondrive wheel that will be pulled along with the bot. If the bot rolls, the wheel rolls, the encoder gets an accurate count.

If the bot doesn't roll, the wheel doesn't roll, the encoder still gets an accurate count. This means it doesn't matter if the drive wheels are slipping.

[Ryan O]

In direct answer, yes, if the wheels slip then the encoder will be wrong. An encoder measures a number of revolutions, and has no way of "knowing" how much traction a wheel has. For traction control, you could look at either an idle wheel, current sensors on the motors, or an accelerometer. Encoders are a good choice to see what the wheels are doing in terms of speed - it will allow comparison to another sensor - and the comparison could provide the slip/no slip info you want.

[Freeztech]

Originally Posted by Ryan O

In direct answer, yes, if the wheels slip then the encoder will be wrong. An encoder measures a number of revolutions, and has no way of "knowing" how much traction a wheel has. For traction control, you could look at either an idle wheel, current sensors on the motors, or an accelerometer. Encoders are a good choice to see what the wheels are doing in terms of speed - it will allow comparison to another sensor - and the comparison could provide the slip/no slip info you want.

yeah, my team was thinking about that, this would allow you to have a comparison between what your robot is doing and what it thinks its doing, allowing you to work this into an automatic acceleration code. because of how tricky the acceleration is going to be, this would help out loads.

[kamocat]

In this case, would it be legal to use two omniwheels? Would this be considered using items other than the rover wheels for traction, even if they are designed not to mechanically affect the slippage or traction of the robot?

[Andy L]

Originally Posted by kamocat

In this case, would it be legal to use two omniwheels? Would this be considered using items other than the rover wheels for traction, even if they are designed not to mechanically affect the slippage or traction of the robot?

Check the Q&A for this, there is a large amount of posts on that, but in general they say it is ok but provide more specifics than just that

[EncodersRUS]

Thank you for all of your input and suggestions. I will approach our legal dept. tommorow to see exactly what wheela we can use but will probably end up listening to mechanical. Thanks!