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RobotC wheel slippage problem 
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Joined: Thu Dec 18, 2014 9:55 am
Posts: 3
Post RobotC wheel slippage problem
I am observing wheel slippage making my minstorm nxt robot go off course. I have built a castor bot to observe slippage. I have done mechanical fixes to add traction. I have also played with power level, but slippage issue is not going away. Is there a way to implement traction control using RobotC APIs or is there a reference code I can find to implement traction control?
I am using sample reference code to observe slippage:
task main()
{
nSyncedMotors = synchAB;
nSyncedTurnRatio = 100;
motor[motorB] = 75;
wait1Msec(4000);
}


Thu Dec 18, 2014 10:08 am
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Professor
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Joined: Sat Aug 31, 2013 9:15 am
Posts: 256
Post Re: RobotC wheel slippage problem
So let me see if I'm interpreting your code correctly. You're trying to do a point turn with your robot, and your wheels are slipping as the robot is doing the turn, correct?

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Thu Dec 18, 2014 5:29 pm
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Joined: Thu Dec 18, 2014 9:55 am
Posts: 3
Post Re: RobotC wheel slippage problem
Nope, its just going straight on a slippery surface where wheels of bot don't have traction, even after using best traction tires I could find. As it tries to go straight, wheels slip and wonder off.

Our coach thinks programming can help solve some of these mechanical build issues.

I was researching into using Gyros with Encoders to detect slippage. But before I invest into Gyro sensor for NXT, I want to learn about what others experiences are and make sure investment will pay off.


Thu Dec 18, 2014 9:12 pm
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Guru
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Joined: Sun Nov 15, 2009 5:46 am
Posts: 1523
Post Re: RobotC wheel slippage problem
So, the ultimate goal is to have the robot go straight instead of curving to one side because one side of the wheels are slipping? If that's the case, gyro may or may not be able to help. You need to really find out the cause of the curving. If it is really because of slippage, it may do the opposite for you. Imagine when you command the robot to go straight forward. Let's say the left wheels are slipping. That means the robot will curve to the left because the right side will go faster than the slipping left side. Then the gyro controlled PID will try to compensate by giving the left wheels more power and the right side left power. If the left wheels are already slipping, giving them more power will make them slip even more. If wheels are really slipping, it means your drive train is too strong. You can remedy this by gearing the drive train differently so that the wheels will go faster with less power or simply decrease the overall power supplied to the wheels. Alternatively, if your robot is tiny and underweight, then you may want to add weight especially to the side that the wheels are slipping.
Is this happening at the end game where you need to climb the ramp? If so, it may be easier to just write code so that it will supply say 1/3 of full power to the wheels when a button is pressed. Then it will drive slowly up the hill without slipping. In general, just apply the strategy you would use when you drive a car up the hill in a snowy winter day. No sudden start or stop, drive slowly and steadily, put weight on the driving wheels, chain up (i.e. add friction to the wheels).


Thu Dec 18, 2014 10:18 pm
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