May we have some traction control help?

[Doug Leppard]

Our drivers are happy with our traction control. We have the driven wheel encoder and a vex Omni wheel on the floor called the undriven wheel.

We found 20% slippage is the best. Our moving algorithm follows the joystick either increasing power or decreasing power according to the joystick position and wheel slippage.

But you have the 0 or little speed situation, for instance you may be in a pushing war and going almost 0.

For that we don’t do a ratio of slippage because it does not make sense. But we allow a certain number of rpms of the wheel which is slippage at a standstill.

It is very simple.

BTW we put a toggle switch on the driver’s station that allows the drivers to turn off and on the traction control; sometimes the drivers use the large amount of slippage to their advantage especially in turning.

[marccenter]

Originally Posted by Doug Leppard

Our drivers are happy with our traction control. We have the driven wheel encoder and a vex Omni wheel on the floor called the undriven wheel.

We found 20% slippage is the best. Our moving algorithm follows the joystick either increasing power or decreasing power according to the joystick position and wheel slippage.

But you have the 0 or little speed situation, for instance you may be in a pushing war and going almost 0.

For that we don’t do a ratio of slippage because it does not make sense. But we allow a certain number of rpms of the wheel which is slippage at a standstill.

It is very simple.

BTW we put a toggle switch on the driver’s station that allows the drivers to turn off and on the traction control; sometimes the drivers use the large amount of slippage to their advantage especially in turning.

Doug,
In order of implementing a traction control algorithm I have proposed for a FRC conference presentation paper with VEX and Easy-C Pro implementation: 1) rate-limiting joystick command input to motor command output - solves a multitude of problems, 2) control maximum motor speed command as a function of undriven wheel speed (non-feedback based slip control) Joystick position can be independent of the maximum motor speed command but you have indicated that you did
add joystick dependence. Can you indicate why? 3) feedback based slip control (driven wheel speed based to undriven
wheel speed)

[windell747]

Yes, labview already has a block called the PID output rate limiter. It can be found in Addons->PID Control->PID. BTW, what does the EGU/min input mean physically. I know the greater it is the faster the output response, but I want to calculate what this means to the rate limiter so that I can get a ballpark without doing a lot of testing.

simulink rocks!

[Doug Leppard]

Originally Posted by marccenter

Doug,
In order of implementing a traction control algorithm I have proposed for a FRC conference presentation paper with VEX and Easy-C Pro implementation: 1) rate-limiting joystick command input to motor command output - solves a multitude of problems, 2) control maximum motor speed command as a function of undriven wheel speed (non-feedback based slip control) Joystick position can be independent of the maximum motor speed command but you have indicated that you did
add joystick dependence. Can you indicate why? 3) feedback based slip control (driven wheel speed based to undriven
wheel speed)

Not sure if I follow what you have asked, so I may not be answering your question. Case below is when the robot is moving.

On the joystick. It would seek the power setting of the joystick. If the joystick was at 3/4 power then the power would increase (or decrease) to 3/4 power but without slipping more than 20%. So if the driver moves the power from 0 to 3/4 power then it will keep increase power until it reaches 3/4 power, but it will be much less power to the wheels until it reaches that power.

If you are going at 3/4 forward power and shove the robot into reverse, it will decrease power without more than 20% slippage so it will not go into full skid.

I hope this makes sense.