Lab #1 Deliverable:
At lower speeds the motors that we used in lab one would stick and not move. We also had some problems when trying to put them into reverse. This is interesting because the most efficient propeller is a very large, slow propeller, but we’re going to have to work around the motors not running at lower speeds.
Lab #2 Deliverable:
Today we attached the sensors to the Arduino. During the lab we actually messed up and only used one sensor, this was later rectified and we now have two fully functioning reflectance sensors.
The limited commands available to us for this project may hinder the efficiency of our vehicle because we are not able to fine tune them with our basic knowledge of C++. I don’t however think that this will hurt our efficiency more so than the inability of the motors of function under low speeds. We have to account for the AEV not being able to brake right away when we call the command. I don’t think that will be an issue — if we get the math right, we should be able to calculate with relative certainty the exact distance that the AEV will travel before stopping. This just requires a basic knowledge of physics — something that we all possess thankfully.
One of the most important sensors on the AEV is actually the reflectance sensor. This sensor tracks how far the AEV has actually traveled and allows us to plot the power usage over a certain distance. It also allows us to program the AEV to stop at certain distances traveled which is definitely a helpful feature.
Lab #3 Deliverable:
Our group came up with four great AEV designs, each with their own advantages and disadvantages. The “Flying Falcon,” designed by Hunter Durnford, used a minimal amount of parts, and seems to be the easiest to produce out of the four. However, the design by Jiaqi demonstrated advanced knowledge of aerodynamics and would most likely hold position better in any kind of turbulent cross flow; as well as using less fuel. As a team, we decided that because of the slow speeds, aerodynamics are not very important when compared to power consumption or the actual weight of the vehicle. Brian and Josh both designed very interesting AEV’s as well. Josh’s design incorporated a higher center of mass than some of the other AEV designs, which may be advantageous in some situations. Brian’s AEV, utilized an interesting central propeller design — we are not so sure that this will be the most effective positioning for the motor, and will likely change it upon secondary design review.
Lab #4 Deliverable:
Energy Vs Time Graph:
Energy Vs Distance Graph:
Explanation for Figures:
Data collected from the experiment is shown in Graph 1 above. The plot shows how the energy input changes when certain program functions are called. Starting from t (time) = 0s until t = 3s, the motors were accelerating to approximately 25%, which is why the power increases linearly as a function of time. Until t = 4s, the motors ran at 25%, which is why the power stays constant. When the motors were set to 20% for 2 more seconds, the power input dropped and stayed constant. At t = 6s, the motor reverses, and the power is set back to 25%. The large spike at this point could be a result of inductance in the circuits, forcing a large power surge to bring up the current quickly enough. From t = 6s to t = 8s, the power was kept constant at 25%. Even though the motor is running a different direction, the power stays positive. Overall, these results are in line with predictions for the AEV’s performance.
Graph 2 is the Power vs Distance graph which can be related to the Power vs Time graph by comparing the similar shapes. When the motor starts to accelerate linearly up to 25%, the AEV did not move very much, going approximately 0.02 meters in the first 3 seconds. This is also due to the propellers sticking at low speeds. In the remaining 5 seconds, the AEV moves slightly over 0.2 meters. The AEV can be observed coasting for approximately 5 cm after the power is cut at the end.
While the AEV is working on the track, the most important resistances that it is experiencing are aerodynamic drag and friction between the bearings and the wheel interior.
Aerodynamics are an important part in improving the design. Some of the designs use a single motor, and were thought to use less energy even though they produce less thrust. Due to the limited amount of energy available, a design that incorporates energy saving techniques would be more beneficial than one that produces a higher thrust. Another factor in the design of our vehicles was that they needed to be light-weight. The less weight, the less energy will be used when accelerating the AEV up to speed.
Arduino Code for Lab 4:
celerate(1,0,15,2.5); //Accelerate motor one from start to 15% power in 2.5 seconds
goFor(1); //Run motor one at a constant speed for 1 second
brake(1); //Brake motor one
celerate(2,0,27,4); //Accelerate motor two from start to 27% power in 4 seconds
goFor(2.7); //Run motor two at a constant speed for 2.7 seconds
celerate(2,27,15,1); //Decelerate motor two to 15% power in 1 second
brake(2); //Brake motor two
reverse(2); //Reverse the direction of only motor 2
celerate(4,0,31,2); //Accelerate all motors from start to 31% power in 2 seconds
motorSpeed(4,35); goFor(1); //Run all motors at a constant speed of 35% power for 1 second
brake(2); goFor(3);//Brake motor two but keep motor one running at a constant speed for 3 seconds
brake(4); goFor(1); //Brake all motors for 1 second
reverse(1); //Reverse direction on motor one
celerate(1,0,19,2); //Accelerate motor one from start to 19% power over 2 seconds
motorSpeed(2,35); goFor(2); //Run motor two at 35% power while simultaneously running motor one at 19% power for 2 seconds
motorSpeed(2,19); goFor(2); //Run both motors at 19% speed for two seconds
celerate(4,19,0,3); //Decelerate both motors to 0% power in 3 seconds
brake(4); //Brake all motors
celerate(1,0,25,3); //Accelerate motor from 0 to 25% power over 3 seconds
goFor(1); //Run at 25% power for 1 second
motorSpeed(1,20); //Set motor to 20% power
goFor(2) //Run at 20% power for 2 seconds
reverse(1); //reverse motor
motorSpeed(1,25); //Set motor to 25% power
goFor(2); //Run at 25% power for 2 seconds
brake(1); //Cut power to motor
Lab 5 Deliverables:
For lab five, we were tasked with creating a “Concept Screening Matrix,” this is a matrix which allows us to compare our individual AEV designs, along with our group AEV design to what we would consider “baseline” values. The AEV with the highest score on the concept screening matrix will likely be the first one we test, and then we will compare it with the second highest score.
Concept Screening Matrix:
Unfortunately, three of our initial designs did not hold up well against the other two. This is because either they were lacking aerodynamic efficiency, or they were likely to draw more power than required for the same task as another AEV. Design C and design D both ended up tying for first place. These two AEV designs will thus be built and analyzed in order to determine which is actually the most efficient. The key differences between the two are weight and balance. For weight, design C came in at a 1.2 on our scale, and design D only scoring a .90. Balance however, was the opposite; design D won in this category by .2 points.
