In the last class assignment, we had to build a Basic Two-motor NXT Car, which is a basic car that can be programmed from a computer. We had a box full of detached pieces, and my teammates and I had to follow the instructions given by the professor in order to link the different pieces and build the car.
Our second task was to measure the diameter of the wheel in order to find the circumference in meters.With the aid of a ruler, we found that our diameter was about 5.6 cm. The next step was to calculate our circumference, which is equal to Pi * diameter, and in our case, it was equal to 0.167m. We can conclude from our last experience that for every rotation the car travels a distance of 0.167m. Therefore, we connected the car to the computer in order to manipulate the car through a program called VI wheel_rotation_straight.vi. The program allowed us to move the robot with a specific power for a specific time. We also needed to measure the distance traveled by the car in each trial in order to compare it with the correct answer given by the program. By doing so, we were able to figure out the percentage of error that we made in each trial. The rule of the error is equal to |d1 – d2|*100/((d1+d2)/2).
Our trials are represented in the table below:
| Power | Time(s) | Distance Measured(m) | Distance on screen(m) | Error(%) | |
| Trial 1 | 75 | 2 | 0.26 | 0.2673 | 2.77 |
| Trial 2 | 50 | 2 | 0.18 | 0.1676 | 7.135 |
| Trial 3 | 25 | 2 | 0.08 | 0.0738 | 8.0624 |
| Trial 4 | 25 | 3 | 0.245 | 0.236 | 8.1967 |
| Trial 5 | 50 | 2 | 0.36 | 0.3548 | 1.681 |
| Trial 6 | 20 | 5 | 0.27 | 0.289 | 6.79 |
| Trial 7 | 90 | 1 | 0.33 | 0.3191 | 3.39 |
As we can see in the table above, our measurements were not always accurate. In each trial we had some errors. The most “accurate” measurements were in trial number 5 where we had the least percentage of error.
Overall, I liked the robotics activity because I was asked for the first time to build a car in a class, which was a funny experience.