Final Report

	Software Design
	Project Results

About Us

In an attempt to reduce the amount of power needed to make our robot steer, we took a cue from our lego robot and placed a pivoting third wheel in back of our robot in place of the two rear wheels. Doing this significantly reduced the torque requirements for turning the robot, but it also increased the robot's weight by more than 15% and reduced the supplied torque by 50%. The robot could now turn, but it could no longer go straight forward or reverse.

We acquired from Corey a set of smaller wheels that would increase the amount of force applied by our motors and set about making measurements to determine if, using these smaller wheels, we could make our robot work. It was then that we discovered just how inaccurate our initial assumptions were. Our robot was more than 6 times as heavy as Corey's robot and required about seven times the force to move it in a given direction. We found that our 26 lb. robot required 156 lbs.-in. in order to turn it. Our motors should have given us 10.24 lbs.-in. each, or 204.8 lbs.-in. for turning. However, our measurements showed that each motor only gave us 6.25 lbs.-in. of torque, or 125 lbs.-in. for turning at 12V. At 24V this increased to 159 lbs.-in. of torque, matching our observation that at 12V the robot was totally unable to turn, but at 24V it was able to turn a little. At 12V, the torque provided by the motors is far below what is needed; at 24V it is just enough, but that assumes that all four motors always provide this maximum amount of torque. In reality, the motors often slipped and stalled, resulting in a loss of significant torque. Using the larger tires, we saw less than a third of the needed torque for turning, even at 24V. We now estimate that had our motors been providing the specified 10.24 lbs.-in., they would just barely be able to turn the robot, after slippage and stalling are considered.

Certain now that our motors were underpowered, we considered what to do next. We were able to find a number of motors that would have given us a considerable level of comfort that we could turn the robot, even with the larger tires, however these motors were quite expensive ($40+), neither did we have time to order them. We also realized that these motors were all at least 5 in. long...too long to fit on our robot. We decided to shift our concentration to the lego robot that had been in parallel development for the remainder of the semester.
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