During Lab 3 we were presented with design screening and scoring methods to be used to filter out design options and get closer to the goal of an optimized final design. Specifically we looked at our four preliminary design concepts as provided in the Lab 1 Executive Summary and as well an alternative design involving 3D printed parts. This alternative design ended up scoring the highest after assessed through the concept screening and scoring matrices. This design became our primary focus following Lab 3. A copy of the Executive Summary is provided below:
Michael Ahlbeck-Fetch, Chenchao Jin, Thinh Tran, Bolong Zhang Lab 3: Concept Scoring
Group J – Instr. Kadri Parris, GTA Hossein Qarib February 18th, 2015
Executive Summary
Purpose: In order to evaluate each design provided by team members before and become familiar with techniques for design decision-making and a method to screen and score methods, a concept screening sheet was created to scoring each design. The behavior of the sample AEV is observed and concept-screening method was practiced with the references of sample AEV.
Background:4 designs were provided by team members previously and the final design need to be determined. The skill of writing code to control the AEV was practiced in Lab 2.During the lab the sample AEV kit was assembled and a sample program code was load to Arduino chipset. The sample AEV was installed on the track.
Objectivity: Each team member will express his or her opinion about a specific design to avoid subjectivity. The same Arduino code will be used on different designs to insure objectivity. The masses of the major components were weighed to make the balance of the kit precisely.
AEV behavior: After the AEV started to execute the code it accelerated for 3 seconds and continued going forward for about 5 seconds. Then two motors reversed and the AEV started to decelerate. It just stopped on the track when the deceleration period ended.
For our final design AEV, we extended the time period in commands in order to observe it carefully. It accelerated for about 8 seconds and keeps going for about 3 seconds, and then it hit the sensor on the track and stopped. After about 4 seconds its motors reversed and start to accelerate to the opposite direction. It decelerates for 4 seconds before completely stopped on the track.
Pros and Cons for Each Design:
After our teams discussed we get the following results.
Design A
Compare to reference design, design A is better at Minimal blockage and cost.
Almost even at Maintenance and Environmental. It’s not so good at Balanced, Center of gravity and Durability.
Design B
Compare to reference design, design A is better at Environmental. Almost even at Minimal blockage, Balanced, Center of gravity, Durability and cost. It’s not so good at Maintenance
Design C
Compare to reference design, design A is better at Balanced and center of gravity. Almost even at Minimal blockage, maintenance, durability, cost, and environment. There’s no thing worse than the reference design.
Design D
Compare to reference design, design A is better at center of gravity and cost. Almost even at maintenance, durability, balanced, and environment. It’s not so good at Minimal blockage.
Design E
Compare to reference design, design A is better at Balanced, minimal blockage, center of gravity. Almost even at maintenance, durability, cost, environmental. There’s no thing worse than the reference design.
So, Design E will be proceed in the lab on account of better weight balance and weight reduction. It also has a better usability since the Arduino chipset was installed at the bottom of the kit.
Resolving Error: All our own designs are not good enough, so we discussed all the problems our AEV designs have. We realized we need a new design. It must be better than all these 4 designs.
Recommandations: We don’t feel like the first four designs are what we want. So I recommended finding a new one. So we discussed and come up with our final design. Design E, we used concept of screening. It was also get the best score.
Analysis and Conclusion: The screen method was used to evaluate each design since it is easy for calculation. The pros and cons of each design were listed and another design, which created, by all team members was listed on the screening sheet as well. The factors that we especially care about are the balance issue and the weight issue. Also, we want to make it easy to operate.
Design E will be proceed in the lab on account of better weight balance and weight reduction. It also has a better usability since the Arduino chipset was installed at the bottom of the kit. Also, as what was showed in the concept-screening sheet, this design is well organized at minimal blockage with a better design of center of gravity. The Net score showed that this is the best blue print that could be proceed.
Appendix
Arduino code
// Accel all motors 0-25% in 3s
celerate(4,0,25,3);
// Run all motors at 25% for 2s
motorSpeed(4,25);
goFor(2);
// Run all motors at 20% for 2s
motorSpeed(4,25);
goFor(2);
// Reverse all motors
reverse(4);
// Run all motors at 20% for 2s
motorSpeed(4,20);
goFor(2);
// Brake all motors
brake(4)
Concept screening sheet
| Success Criteria | Reference | Design A | Design B | Design C | Design D | Design E |
| Balanced | 0 | – | 0 | + | 0 | + |
| Minimal blockage | 0 | + | 0 | 0 | – | + |
| Center- of-gravity | 0 | _ | 0 | + | + | + |
| Maintenance | 0 | 0 | – | 0 | 0 | 0 |
| Durability | 0 | _ | 0 | 0 | 0 | 0 |
| Cost | 0 | + | 0 | 0 | + | 0 |
| Environmental | 0 | 0 | + | 0 | 0 | 0 |
| Sum +’s | 0 | 2 | 1 | 2 | 2 | 3 |
| Sum 0’s | 7 | 2 | 5 | 5 | 4 | 4 |
| Sum –‘s | 0 | 3 | 1 | 0 | 1 | 0 |
| Net Score | 0 | -1 | 0 | 2 | 1 | 3 |
| Continue? | Combine | No | No | No | No | Yes |
Concept scoring sheet
Figure 1: Design A
Figure 2: Design B
Figure 3: Design C
Figure 4: Design D