After carefully analyzing the design concepts selected from the morphological charts for technical feasibility, functional feasibility, and buildability by using evaluation criteria and Go/No Go analysis, the six concepts have been reduced to two concepts. It is important to have two concepts, rather than just one, because one is the primary choice and one serves as a back-up design. In the event the primary choice is not feasible in some unforeseen way, having a back-up design on standby will allow our team to quickly jump into the next design concept, helping us to stay on track and meet deadlines.
Referencing the PMI lists for each design, which can be found in assignment 2, we were able to narrow our designs from six to two.
We first eliminated the design that had the highest ratio of minuses to plusses. This was Concept 6-Kite. We decided that a design for which the negatives outweigh the positives two to one was not worth the effort. It also had many possible modes of failure. In terms of functional feasibility, a kite is an inefficient way to capture wind energy, and it is doubtful that a compressor could get enough power to increase the pressure inside the pressure vessel by even 1 Pa. In terms of buildability, robotic legs are complex systems that are difficult to build.
We then eliminated the design that utilized a capacitor to store energy. This was Concept 2-Capacitor. It also had a large ratio of disadvantages to advantages. Two disadvantages caused us to dismiss this design, though. In terms of functional feasibility, it is hard to regulate capacitor discharge rate, and belts are unreliable in that they can slip. In terms of technical feasibility, it would be difficult as we would need a very large capacitor, which would be very expensive. These lead to possible modes of failure. The capacitor could discharge almost instantaneously, which would fry our circuitry and leave us with no more stored energy to run the course. With belt slippage, we could see loss of navigational ability as the commands the brain is giving fail to reach the wheels as intended.
We eliminated Concept 4-Pulleys, because it has the same problem with pulleys as Concept 2-Capacitor. Looking at the PMI list, it is a good design. It has a lot of advantages, and is technically feasible, functionally feasible, and buildable. However, as navigating the course is such an important part of this assignment, the potential to lose steering is not worth the risk.
Likewise, we eliminated Concept 5-Winding Drum. This design was interesting in that it is purely mechanical, and that makes for a much simpler device. It has a possible mode of failure that Concept 4-Pulleys does not, though. Its technical feasibility is limited, because of the energy storage solution, the amount of energy it can store is limited by the height of the pulley over which the falling weight is hoisted. This means that either the weight could reach the top and we would store a sub-optimal amount of energy. In terms of functional feasibility, having a weight this high also raises the center of gravity a lot, which increases the chance that the device will tip over. As for buildability, it would have to contain a very large gear ratio to be functional. This could be difficult to achieve, as it would either require a huge gear, or a complex gear chain.
Concept 1-Sonar and Concept 3- Alternator fulfill all parts of the Go/No Go Matrix, including both demands and wishes. However, it is to be noted that in terms of functional feasibility, the success of both systems navigation is completely dependent on the quality of its programming. This could be a potential mode of failure. Neither has a substantial problem with buildability.
We chose Concept 1-Sonar as our primary design because the generator produces DC voltage, which is what the rest of the system need. If we use Concept 3-Alternator, it will be necessary to add a rectifier. In the interest of upholding the KISS principle, it is better to use Concept 1-Sonar.
This process of whittling down our concepts to a primary and secondary concept is useful in that it allows us to come to a plan of action, by making informed decisions regarding the ways in which various designs might fail. It is also important to have a primary and secondary concept, in case we come to a point where we decide we would be more successful abandoning our current design for our secondary design. While we do know the potential problems with our primary design, we cannot know the future and it is possible we will come upon an unforeseen, insurmountable problem.