Robotic Cars

On Thursday, September 20, 2012, we were given an unassembled robotic car to do an experiment with it. The objectives of the experiment were to assemble the car, program it to run for a short period of time, and study the results of that command. It took most of us two class periods to achieve these objectives. Each period was seventy-five minutes. In the first period, we assembled the car. In the second one, we did the rest of the objectives.

Assembling the car was the most time-consuming task, not because it was difficult, but because it was my first time building such a car. When my partner and I, with some help from another student, finished building the car, we discovered that the the wheels were not in place properly. So, we had to spend some extra time fixing that. After assembling the car, we made a small test just to make sure that the car ran properly. It did ran properly.

Programming the car did not require as much time as assembling it. Though, we had to do some mathematical calculations in order to program it.

How Does the Car Work and How is it Programmed?

Users give instructions to the car through a program called Labviwe. The car is connected to the computer using a USB cable so all the instructions are transferred to the car via the cable. Although we had the instructions ready, we had to specify them with some numbers such as the duration we want it travel for, the circumference of the wheels, and the how fast we want it to move. When we specify that, we run the car. Once the car stops, Labviwe will output the distance the car traveled with some other information. We were to measure the actual distance it traveled and compare that with Labview’s output to see how accurate is the program.

Calculations:

Distance is measured by the number of turns the wheels make. That means, one turn = the circumference of the wheel * 1, two turns equal the circumference * 2 and so on. The calculation we had to make in order to program the car was to find the circumference of the wheels. That can be found by measuring the diameter of the wheels then plug it in the following equation:

C = circumference.

R = Radius = diameter/2.

The circumference of the car’s wheel was 15.71 cm. But since the program requires all measures to be in meters, we had to convert this number into meters which equals 0.1571 m.

Accuracy:

The accuracy of the program can be determined by the following formula:

We made several trials to see what is the percentage error of the program.

Trials:

Trial 1:

Actual distance = 62 cm = .62 m

Program’s output = .53 m

Percent Error = 14%

Trial 2:

Actual distance = 42 cm = .42 m

Program’s output = .24 m

Percent Error = 75%

In this trial we changed the power from 75 to 50. Maybe that is why the percent error is high.

Trial 3:

Actual distance = 45 cm = .45 m

Program’s output = .31 m

Percent Error = 31%

In this one, we increased the power 50 to 60

The average percent error = 40%

I really had fun building and programming the car. I had gain some experience in building such cars.