Figure 1 - Predict the result of a robot race

Requirements

• Ruler
• 2 Sniffers: http://www.ozeki.hu/index.php?owpn=6204
• Ozeki 10 installed: http://www.ozeki.hu/index.php?owpn=6066
• Snap basics: http://www.ozeki.hu/index.php?owpn=6180

In this lecture you need to know the robot's speed in meter/second. For the easier calculations you should measure the maximum speed of the Sniffer. During Lecture 4, you learned how to measure speed, so you should load the stopwatch program code and replace the power percentage of the motor to 100 as Figure 2.1 demonstrates then run it. After you measured the traveled distance, you should calculate the speed by using the measured distance and the value in the 'passed' variable.

Figure 2.1 - Measure the full speed of both robot

There is a chart about speed values at different power. If you took the previous step, the result of your calculations should be similar to the shown value at 100% power on Figure 2.2. On the chart you can see that the speed increases proportionally with the increase in performance until it reaches approximately 85% of power. Then performance increasing is very small. Keep it in your mind when you calculate with different power percentages.

Figure 2.2 - Measured speed at different power

After you got to know your Sniffer's full speed, you should place both robots on a flat surface in one direction, but they are not next to each other and there is also some distance between them. Then you should to mark the target line for your race. Finally please measure the distance between your target line and both robots. Write this two distance data down because you will need to calculate which Sniffer reaches the target line first (Figure 3). You can race with different robots if you wish.

Figure 3 - The robots look toward the target

After you calculated your Sniffer's full speed, placed your robots on a flat surface and measured the distances towards the target line, you need to calculate how much time your Sniffers need to reach the target line. To calculate the required time, you should express the time from the velocity equation. So please multiply the velocity equation by the time and divide it by the speed, as you did in Lecture 4. Finally please write the equation for both robots (using indices), because your Sniffers will move different distances with different speed. Look at Figure 4 for help.

Figure 4 - Calculate the required time for each robot racer

There are some obvious cases when you can predict the winner without any calculation. The closer Sniffer wins if it is faster or has the same speed as the further Sniffer. But if the further Sniffer is faster than the closer one, you need to calculate the racing time for each robot by using the equation from the previous step. If the further Sniffer needs less time to reach the target line, it will win the race. If the results of the calculations are equal, the race will result in a draw, otherwise the closer Sniffer will win the race. The Figure 5 demonstrates these cases. It all depends on the time towards the finish line.

Figure 5 - The time towards the finish line decides the winner

After you learned how to predict the outcome of the race, you should perform concrete calculations and test it with your program. So you should open your SNAP and load the program you coded during Lecture 7 and modify the speed values as you wish. For the real race please set bigger speed for the further Sniffer. There is an example on Figure 6. After that please calculate the required time for both Sniffers using the equation from Task #3. Finally make a prediction from the time values and test it by starting the race.

Figure 6 - Program code to control Sniffers

---

Program codes

Figure 7 - The program codes

Download the SNAP programs The first one helps you to calculate the speed of the robot by measing the passed time. The second one gives you an ability to start both robots at the same time. It is easier to follow the guide if you have the codes in front of you: Download the SNAP program files

More information

• Plan the travel distance
• Move along a path
• Measure the time of the motion
• Calculate the speed of the robot
• Measure distance
• Build a speed camera
• Determine the collision point
• Predict the result of a robot race
• Make your robot faster or slower using gears
• Make the robot more powerful using gears