Graphs:
Power vs. Time Plot
Power increased directly as time increased during the first three seconds because the motors were accelerating from zero to 25% during the first 3 seconds of the run. Power stayed constant while time ran from 3 to 4 seconds because the motors were spinning at a constant speed at 25% power for 1 second. Power suddenly dropped and then stayed constant while time ran from 4 to 6 seconds because the motors quickly decreased speed from 25% to 20% and then were spinning at a constant speed for 2 seconds. The sudden spike of power at 6 seconds is due to the motors being reversed. Power stayed constant while time ran from 6 to 8 seconds because the motors were spinning at a constant speed at 25% power for 2 seconds. From 8 to 12 seconds there was a brake in the motors and no power was recorded once the motors were stopped.
It is interesting to see that the power measured when the motors were running at a constant speed at 25% power in reverse was greater than the power measured when the motors were running at the same constant speed and spinning forward. This could be possible evidence that it requires more power to run the motors in reverse than forward, or that it requires more power to use the motors to push the AEV than to pull it.
Power vs. Distance Plot
This plot shows that the only time the AEV moved in these runs was when the power output was constant at around 5.5 Watts. Looking back at the Power vs. Time plot, one can see that the only time the AEV was producing this power output was when the motors were spinning in reverse at a constant speed at 25% power and were pushing the AEV. This plot also shows that each run of the AEV moved a different distance overall and coasted slightly upon braking.
This data shows that the functions used in this AEV run are not reliable when programming the AEV to run a specific distance. It is also interesting that this plot shows no evidence of movement when the AEV was being pulled by the motors as they were spinning forward and accelerating, or as they were spinning forward at a constant speed at the same power percentage of 25% as when they were in reverse. Instead, it only shows that the AEV moved when the motors were reversed and then immediately set to spin at a constant speed at 25% power. So why did the AEV move when it was run in reverse at a constant speed at 25% power and not when the motors were spinning forward at a constant speed of the same power percentage of 25%? There are a few possible answers for this that can be inferred from the data recorded in this run. One possible answer is that the motors are more effective at moving the AEV when pushing it than when pulling it. This phenomenon would require more testing to be proven true. Another possible answer is that the AEV moved when the motors were ran in reverse because once they were switched to reverse, they were immediately accelerated to a constant speed at 25% power. This immediate acceleration is important because Newton’s second law says that the force on an object is directly related to the object’s mass and acceleration, meaning that the greater the mass and acceleration, the greater the force on the object, and while the mass of the AEV remains constant when the motors are spinning forward and in reverse, the acceleration does not. When the motors are spinning forward, they have a slow acceleration from zero to 25% power over 4 seconds, causing the AEV to experience a lesser force than when the motors switch to reverse and immediately accelerate to 25% power. So why does it matter that the force needs to be greater to move the object? Well it wouldn’t if this was a frictionless system, but this is real life and there is friction in almost everything. This system experiences static friction between the wheels of the AEV and the track and this static friction must be broken by a specific force in order for the AEV to move along the track. Since the AEV did not move when accelerating from zero to 25% power when the motors were spinning forward, the force during this time was not great enough to break the static friction, which is why the AEV did not move. Since the AEV moved when the motors were reversed and immediately accelerated to 25% power, there was enough force to break the static friction and move the AEV.
Scenario 2 Code (Exercise 4):
//Accelerate all motors from start to 25% in 3 seconds
celerate(4,0,25,3);
//Run all motors at a constant speed (25% power) for 1 second
motorSpeed(4,25);
goFor(1);
//Run all motors at 20% for 2 seconds
motorSpeed(4,20);
goFor(2);
//Reverse all motors
reverse(4);
//Run all motors at a constant speed (25% power) for 2 seconds
motorSpeed(4,25);
goFor(2);
//Brake all motors
brake(4);