[archiver]

Posted by Ken Leung at 03/20/2001 10:02 PM EST


Student on team #192, Gunn Robotics Team, from Henry M. Gunn Senior High School.


In Reply to: Forward/Reverse difference in drill motors.
Posted by Joe on 03/20/2001 7:22 PM EST:



A lot of people recommend solving this problem by driver's compensation...

Usually, people use two joysticks and each control one drill motor. So, by slowing down one side of the drive train, the robot will go straight.

This method is more preferable because if you are fixing it through software, you will always end up reducing the power output to the drill motor(s). Therefore you won't be able to give full power to both motors when needed.

Of course you can always program a button so that whenever that button is pressed, you will be able to output full power to the motors. But if you are doing that way, you might as well have the drivers control the drive train themselves and let them do whatever they want without any restrictions from the software.

All it take is a bit more practice to perfect it...


But if you really want to edit the software, then all you have to do is reduce power output to the forward-spinning motor so that the two motor¡¦s speed will match up. Reduce the range of power output compare to the normal range of your joystick. Just edit the number until you feel it is as straight as you want. Also, make sure you remember that when the robot is driving backward, the forward-spinning motor is the different side.

As for a mechanical way of solving this problem, you can always rotate the motors so that the output shaft of both motor are facing the same way... However, there are few mechanical disadvantages to this solution:

Your two side of the drive train are forced to be closer together, making the robot easier to tip on its side comparing to a drive train that's as wide as possible.

You risk exposing the wire coming out of the drill motor to the side of the robot, risking unnecessary damage to the motor/wires.

Your center of mass of the base will be shifted closer to the side instead of the center.


You might be able to rotate the motors vertically so that one is pointing upward and the other downward. However, that will also risk unnecessary damage to the wiring on the pointing upward motor. You have to remember that the drill motor assembly is pretty long, so you need to leave enough room vertically to fit it in the drive train, meaning a higher center of mass for the robot. And of course, you will need some sort of Bevel gear to transfer the vertical rotational motion into horizontal motion. However, you want to use as little gears as possible because no gears have an efficiency of 100%, meaning when ever you use more gears, there will be more power lost.