Lab 1: Motor Quantity
Objectives-
Determine the quantity of motors that will give the biggest battery efficiency.
Background:
Because the motors are in the parallel circuit so no matter how many motor used in the AEV, the energy output from the battery(W1) will be the same. What determine the battery efficiency is the rate to transfer the battery energy to kinetic energy of the AEV(W2). The battery efficiency is ƞ=W2/W1.
The motor will directly affect the rate to transfer the energy so to find out the most proper motor quantity make the battery efficiency biggest. Based on that, in this experiment, one quantity motor and two motors AEV will be tested.
Method:
Use Arduino code to control the AEV movement. To see the code please read the code part in the website.
In this experiment, there are two parameters should be controlled, one is the battery output power, the other is the mass of the AEV. By coding the battery output power can be controlled. As to the mass of the AEV, when testing the one motor AEV one motor should be leave on the AEV but not attach to the battery. After testing five times of each type of AEV, using the analysis tool to draw the figure Power vs. Time and Power vs. Distance respectively.
Result and Data:
Power vs. Time
Figure 1
In figure 1, it can be shown that the power of two-motor AEV is approximately twice of the one-motor AEV, because W=P*t so the battery energy usage of two-motor AEV is approximately two times as the one-motor AEV. W2,output=W1,output.
Power vs. Distance
Figure 2
As shown in this figure, during the same time, the two-motor AEV travels six times distance as the one-motor AEV so the speed of the two-motor AEV is six times as the one-motor AEV. Because the mass of two AEVs are the same, so the force to push the AEVs are the same: F1=F2. P=F*V, the power of the two-motor AEV is six times as the one-motor AEV, as well as the kinetic energy of AEVs. W2,AEV=6W1,AEV. From the equation ƞ=Woutout/Winput, the battery efficiency of the two-motor AEV is three times as the one-motor AEV.
Conclusion
From the data and analysis part, the battery efficiency of the two-motor AEV is three times as the one-motor AEV. So to get bigger speed and greater battery efficiency the two-motor AEV should be taken into the design.
Takeaways
In this experiment, the battery voltage are assumed to be a constant, however, in the practice the battery voltage will decrease as it moveing. It can be potential problem in this experiment. To tackle with thisproblem, two ways could use: change a full charged battery before each test or use the distance change to draw the graph. Further more, in this experiment, only the motor quantity is been tested, the motor configuration does not take into consideration, to get further data the motor configuration should be tested in the next step.
Code Used
//1 Accelerate all motors from start to 45% in 3 seconds
// Run motor one at a constant speed (23% power) for 2.5 second.
reverse(4);
motorSpeed(4,45);//
goFor(2.5);
//Accelerate all motors from start to 50% in 3 seconds.
celerate(4,0,50,3);
// Run all motors at a constant speed (50% power) for 1 second
motorSpeed(4,50);
goFor(2);
//Run all motors at 35% power for 2 seconds.
motorSpeed(4,35);
goFor(3);
//Reverse all motors.
reverse(4);
//Run all motors at a constant speed (45% power) for 2 second.
motorSpeed(4,45);
goFor(3);
Lab 2: Battery Testing
Figure 1. Power vs. Distance
Figure 2.Power vs. Time runs
Conclusion:
(1)The volatage of the Li-Po battery decrease as times of runs increase.
(2)The distance the AEV travels decrease as the voltage of the Li-Po battery decrease.
Recommendation :
(1)Use fully charged battery to ensure the stability
(2)Use position commands instead of power command when a precise position for the AEV to take certain actions is needed.(i.e., stop)
Next steps:
Do further testing to find a method to decrease the influence the voltage of battery have on the stability of the speed of AEV and the distance it travels.
Code Used
//1 Accelerate all motors from start to 45% in 3 seconds
// Run motor one at a constant speed (23% power) for 2.5 second.
reverse(4);
motorSpeed(4,45);//
goFor(2.5);
//Accelerate all motors from start to 50% in 3 seconds.
celerate(4,0,50,3);
// Run all motors at a constant speed (50% power) for 1 second
motorSpeed(4,50);
goFor(2);
//Run all motors at 35% power for 2 seconds.
motorSpeed(4,35);
goFor(3);
//Reverse all motors.
reverse(4);
//Run all motors at a constant speed (45% power) for 2 second.
motorSpeed(4,45);
goFor(3);