Robots:Which wheel design is better-Base or gimbal?

Jonah Chang Form A

Hypothesis

• I believe that the base wheel design will be more stable and will have better braking and that the gimbal wheel design will be faster.

• Materials:I used2 NXT lego robots(with appropriate pieces) 1 stopwatch1 piece of paper with marked increments1 ruler1 Lego NXT software program1 computer1 pencil1 flat surface area1 level

Procedure

• Procedure: First, I needed to find a type of robot that would work for my purposes. I decided to use a Lego NXT Robot as it was easy to construct and use. I used two lego NXT robots and I built one with a gimbal wheel design and the other with a base wheel design. Second, I needed to find a flat surface area to perform my experiment. Using a level, I found a counter that was completely level to use. I placed my two robots on this flat space, I lined them up on a piece of paper marked with increments of 1 centimeter

Procedure cont.

• measurements.On the computer, I wrote four programs that commanded the wheels to move at 1 rotation , each with a different speed. I then downloaded the four programs to each of the robots. As, I mentioned before, each program had different speeds. One had 100% capacity speed. I then started the program with 100% capacity speed on the Robot with the base wheel design. One rotation of the wheel is equal to the length of the circumference of the wheel. To find the circumference of the wheel, I multiplied the

Procedure con.t

• diameter by pi. (For my purposes I have pi as 3.14). The diameter of the wheel was 4.1 cm, so 4.1 x3.14 = 12.874. So, when the robot goes 1 rotation it should go 12.874 cm. I then did each of the other 3 programs (at 75% speed, 50% speed and 25% speed). I then repeated the process with the robot with the gimbal wheel design. These eight runs were the end of my first trial. The next day, I repeated the four programs on each robot. These performances consisted of my second trial and the end of my brake testing. Next, I

Procedure cont.

• did my accuracy tests. On the same large piece of paper with the centimeter increments, I drew two parallel lines. The space between them equalled the width of the robot. If the robot strayed from the two parallel lines, I could tell how accurate the robotís direction was. Using different programs that commanded the robot to go three rotations, I performed the eight runs for my first trial. Then, the next day I performed the second trial.Following that I did my speed trials. I used different programs, telling the robot to

Procedure cont.

• go a longer distance, for four rotations, each at 100, 75 50, and 25% capacity speed. I then performed these four programs, with a timer. To find how fast they went, I did distance divided by time. I performed each of these eight times on each robot, for my first and second trial. Once I finished these, I finished my testing.

Observation

Observation

Braking

Speed

Accuracy

• Programming:Programming a lego NXT robot can be done many ways. It can be done by java

script, the program labview, or using the Lego programming softare (Programming)to name a few ways. I chose to use the last method, as it was the cleanest method for my purposes. Above exists a picture of what the lego program software looks like. It is quite easy to use to do simple tasks. For example, to get the robot to go one rotation, I needed to do was set the duration to 1. One may also see on the picture, the two motors which powered the wheels, the robotís speed and the direction.

(Programming)

Background Information

• What is the Gimbal Wheel design?A gimbal wheel is a wheel that is not fixed. It rotates around a stationary axis. This allows the wheel to maneuver whichever way the robot is going. A traditional gimbal wheel uses gyros so the wheel is always facing one way. I am not using this hemispherical omnidirectional gimbaled wheel. The gimbal wheel I am using rotates around a stationary pole, not an inside ring. As a result, the gimbal wheel may fishtail when it moves. Fishtailing occurs when an objectís back wheels lose traction due to movement and can cause the robot to slip off a determined path. Fishtailing is not only common to robots or vehicles with gimbal wheels. Any car that loses traction with the back two wheels fishtails. What is the Base Wheel design?The Base wheel design is a design where all the wheels are fixed and there are no turning wheels. This design allows for greater stabilization but needs more power for turning due to the non-turning wheels. This design can fishtail also, but the chances are less. Strickland, Jonathan. "What is a gimbal." How Stuff Works. How Stuff Work, n.d. Web. 29 Mar 2013. <http://science.howstuffworks.com/gimbal1.htmhttp://science.howstuffworks.com/gimbal1.htmhttp://science.howstuffworks.com/gimbal1.htm>.

Conclusion

• Conclusion/Conclusion Analysis:As I predicted, the gimbal wheel robot was faster than the base wheel robot. However, as the robot got faster, the differences between the two decreased. At 100%, the difference was only .1-.2 seconds. I believe this is because the ratio of seconds difference stays the same as you get faster. In brake and accuracy testing I was also correct in hypothesizing. The base wheel design, due to itís non-swerving wheels, could brake with more efficiency. The gimbal wheel robot strayed off itís course due to fishtailing in the accuracy trials, so the base wheel design was more accurate. Overall, I would use the base wheel design, because even though the gimbal wheel could go faster,the base wheel design could go almost as fast, and was

more accurate and better at braking.