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Unread 01-18-2009, 03:07 AM
tuna.and.cheese tuna.and.cheese is offline
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Car Steering...

Hi everyone. I am trying to implement direct drive where all four motors are connected directly to all four wheels. I also want these wheels to each turn like a car would to make turns. If the joystick is in the upper left position, the robot will turn left and go forward and if in the right position, the same but turn right. The drive train is already built and the electronics are on the robot, but I am yet to attempt to program this and am just in the research stage.

Would anyone know how I could go about attempting this? I could get the robot to go foward and back, but to do this while at the same time rotating motors to turn left or right is not making too much sense.

Any help will be great. Thanks. Justin.
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Unread 01-18-2009, 11:42 PM
TimCraig TimCraig is offline
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Re: Car Steering...

Car style steering is called Ackerman steering. If you search for that there are a number of useful articles on the web. A number of teams used this in 2008. A team I worked with some used it and one problem they had was coming up with a way of "holding" the steering position. The natural tendency of these systems is to "want" to return to driving straight. Let go of the steering wheel of a car while it's moving and see what happens.

Quote:
Originally Posted by tuna.and.cheese View Post
Hi everyone. I am trying to implement direct drive where all four motors are connected directly to all four wheels. I also want these wheels to each turn like a car would to make turns. If the joystick is in the upper left position, the robot will turn left and go forward and if in the right position, the same but turn right. The drive train is already built and the electronics are on the robot, but I am yet to attempt to program this and am just in the research stage.

Would anyone know how I could go about attempting this? I could get the robot to go foward and back, but to do this while at the same time rotating motors to turn left or right is not making too much sense.

Any help will be great. Thanks. Justin.
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Unread 02-03-2009, 10:15 PM
gokul gokul is offline
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Re: Car Steering...

Quote:
Originally Posted by tuna.and.cheese View Post
Hi everyone. I am trying to implement direct drive where all four motors are connected directly to all four wheels. I also want these wheels to each turn like a car would to make turns. If the joystick is in the upper left position, the robot will turn left and go forward and if in the right position, the same but turn right. The drive train is already built and the electronics are on the robot, but I am yet to attempt to program this and am just in the research stage.

Would anyone know how I could go about attempting this? I could get the robot to go foward and back, but to do this while at the same time rotating motors to turn left or right is not making too much sense.

Any help will be great. Thanks. Justin.

Are you using additional motors to steer? Your post says all 4 motors are connected to the 4 wheels.

The functionality you are describing seems similar to the Arcade Drive provided by the WPILib classes.

You may want to look in to the details of the Tank and Arcade Drive options provided in LabView and WPILib C++ classes and figure out how your motors should be paired and connected to achieve what you are trying to do.

Steering individual wheels would need steering motors/servos or some such mechanisms in addition to your drive motors.

Try fixing/locking your drive wheels in "straight" configuration and experimenting with the above drive options.

Please post your findings.
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Unread 02-25-2009, 08:51 PM
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Re: Car Steering...

Sorry I didn't see this post earlier. We're also implementing 4WD, car steering, and hopefully will able able to do ASR. Ackerman and differential are calculated. I did the theory and math stuff and the controls guys handled the actual code (though I haven't seen a full demo yet). Do you still need this info?

Cheers,
-Neil.
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