TABLE OF CONTENTS:
Drag
Material Testing
Cost
Current AEV Findings from Lab Testing:
Marketability
Design 5 Test 1
Coasting v. Power Braking v. Servo
Energy Analysis
Performance Test 1
Performance Test 2
Code Comparison
Performance Test 3
Drag
Drag is a force that slows something down. Without some kind of angled and/or round surface, our AEV experience intense drag. To reduce this drag, we implemented an angled round surface from our bottles to increase aerodynamics and reduce drag. With the reduction in drag, we have an increase in energy efficiency.
Source: https://www.nasa.gov/audience/forstudents/k-4/stories/nasa-knows/what-is-aerodynamics-k4.html
Material Testing
Recycling is becoming more important than ever. With the threats of global warming and the toxic chemicals of senseless waste polluting the Earth, recycling simple things like plastic bottles can help significantly. To stress the point that plastics and other material can be reused, we are using recycled materials to make the body of the AEV.
Source: https://www.thoughtco.com/benefits-of-plastic-recycling-1204142
Cost
In terms of materials to use to construct our AEV, plastic is among the cheapest. At around $0.03 to $0.05 per pound, plastic is much cheaper than other materials, such as steel, which is around $0.40 per pound. Along with that, our bottle design optimizes use of our plastic with its thin hollow shell, rather than making a thick shell. Furthermore, plastic is lightweight, which allows it to move seamlessly without weight holding it down, increasing energy efficiency. Plastic is also recyclable, which helps the environment.
Sources: https://www.plasticstoday.com/resin-pricing
https://www.capitalscrapmetal.com/prices/
Current AEV Findings from Lab Testing:
AEV Stopping Systems:
- Power Braking
- Relatively reliable
- Uses high energy
- Errors:
- Code can be improved
- We didn’t spend a significant amount of time testing different power breaking programs
- Code can be improved
- Coasting
- Unreliable
- Does not use extra energy
- Errors:
- Friction has a significant impact on where the AEV ends up stopping
- Travelled almost 50% further after cutting the motor
- Servo
- Uses little energy
- Very reliable
- Adds 259 grams
- Costs $5,950
- Errors:
- Hard to put on AEV
- Energy Consumed of systems
- Ratio of energy consumption → Power Braking : Coasting : Servo == 8 : 0 : 1
- Support
- The research provides the number used in the calculations to determine the energy efficiencies of the servo, power braking and coasting and allowed us to compare the braking accuracy of each type.
Marketability
Being able to use less money to operate over time will be huge selling point with idea that a slightly larger investment upfront costs less to run and maintain. Additionally, being able to precisely choose a stopping location is paramount when transporting people.
Design 5 Test 1 Data
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- Sample test of Design 5 (Distance (m) vs Power (watts))
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- Sample test of Design 5 (Time (s) vs. Power (watts))
Coasting v Power Braking v Servo:
Coasting
Pros:
- No additional energy used (specific energy ratio of 0 joules)
- No added cost
- No additional weight
Cons:
- Unreliable stopping distance
- Adds significant time to each run
Power Braking
Pros:
- Fairly quick stop time
- Reliable
Cons:
- Significantly more energy required (specific energy ratio of 4 joules)
Servo
Pros:
- Extremely reliable
- Very quick stop time
Cons:
- Adds weight to AEV
- Requires more energy than coasting method (specific energy ratio of 0.5 joules)
Though coasting adds no additional cost, weight, or energy, it is significantly more unreliable than power braking or the Servo. Friction and speed both impact the distance and time it takes the AEV to come to a complete stop while using the coasting method. Additionally, the coasting method adds significant time to each run as is apparent in the above graphs. Power braking offers a much quicker stopping time and there is much less variation in stopping distance when the AEV is ran at differing speeds. However, the Servo is the most reliable option and offers the quickest stop time. The fact that it adds weight and requires more energy than the coasting method are offset by the total benefit. Based on this lab, we decided to move forward with the Servo method as the stop time and reliability are the most important factors.
Energy Analysis
Potential errors include:
-
- We stopped the AEV before it stopped moving
- Different batteries with the same code traveled significantly different distances (unreliable batteries)
- The sensor count was off by 3
General confusion from analysis:
We were unsure as to why we needed to know velocity, acceleration, friction force, and propellor force.
Performance Test 1
During performance test 1 the most efficient locations to turn off the motors were identified, and the servo was first being implemented. This test provided basic knowledge on how far the AEV would coast after the servo arm was moved to the brake position and an idea on the energy usage we would be looking at in final testing.
Performance Test 2
Performance test 2 was used to improve the stoping distance once the servo arm was moved to the brake position. The code was improved to reduce time, and the energy required to move out of the gate once the caboose was attached was determined.
Code Comparison
Code comparisons against hard braking at gates vs coasting then braking proved that combining coasting and servo braking, although adding time, reduced over all cost by reducing the energy.
Performance Test 3
The final performance test implemented more coasting prior to braking to reduce overall costs and was used to determine the most accurate locations to stop the motors and drop the servo arm to the brake position to reduce energy and time while still constantly completing runs.