Advanced R&D
Our group had two topics for advanced AR&D. Our first topic was coasting to a stop versus power braking. This is tested by just braking the motors versus reversing the motors in the opposite direction to slow the AEV to a stop. This can be important for our future designs because of accuracy. If the AEV coast too far it could be very difficult to match up its coast with the gate, magnet, etc. However, if we can power brake the AEV, then the AEV could stop much quicker. We used the code below to test the coast of the AEV.
reverse(4); Reverses motors
motorSpeed(4,40); Runs motors at 40% power
goFor(3); Runs motors for 4 seconds
brake(4); Cuts power to motors
After we got the baseline values for just braking the motors we instilled the code below for power braking.
reverse(4); Reverses motors
motorSpeed(4,40); Runs motors at 40% power
goFor(3); Runs motors for 4 seconds
reverse(4); Reverses motors
motorSpeed(4,25); Runs motors at 25% power
goFor(3); Runs motors for 3 seconds
Now that we have both coasting to a stop and power braking we can compare their results below.(Some of these values were calculated by hand which could lead to some human error)
| Trial # | Type of Trial | Total Distance (in ft) | Braking Distance (in ft) | Power Usage (in Watts) |
| 1 | Coasting | 24.67 | 18.1 | 12.82 |
| 2 | Coasting | 25.08 | 18.52 | 12.82 |
| 3 | Braking | 11.17 | 4.93 | 9.34 |
| 4 | Braking | 11.25 | 5.02 | 9.32 |
From these results you can see where both the program stops the original 40% power, but for the reverse braking their is a second burst of power. The results show that the reverse braking is much more efficient compared to the coasting for braking distance. This can make braking the AEV much quicker and much more accurate by matching powers and seconds. This will help the AEV come closer to stopping in the correct position. This will also help avoid the AEV from running off the track making it safer for passengers. Looking forward this means that we should definitely use a design that uses power braking or possibly even look into using the servo to brake for the AEV.
Our second topic was track variance. This topic is important because it will look into how the different tracks can impact the AEV movement, power, etc. This comes into the idea that we may also need to use the absolute position instead of just running the motors for a certain time and power. Below is the code we used for track variance testing.
reverse(4); Reverses motors
motorSpeed(4,40); Runs motors at 40% power
goFor(3); Runs motors for 4 seconds
reverse(4); Reverses motors
motorSpeed(4,25); Runs motors at 25% power
goFor(3); Runs motors for 3 seconds
| Trial # | Type of Track | Total distance (in ft) | Distance Past Gate (in inches) | Energy ( in Watts) | Power Time (S) |
| 1 | Varied | 13.08 | 9.00 | 67.49 | 7 |
| 2 | Varied | 13.58 | 12.00 | 68.46 | 7 |
| 3 | Varied | 13.75 | 14.00 | 67.51 | 7 |
| 4 | Varied | 12.75 | 3.00 | 67.46 | 7 |
These results show a few things. Firstly, the power used from the AEV is going to be roughly the same (or at least very similar) if you are running the same code. Second, this test shows us that the variance in the tracks impacts how far the AEV will go. With the biggest difference almost an entire foot, this means we will need to figure out a way to make our AEV more accurate. One way we could do this would be using the servo. Another way could be using the absolute position function. Either way this test confirms that our AEV will need to become more accurate.