For task 11, we put together a weighted decision matrix in order to determine what would be the best concept for us to continue with.  The only difference between the two concepts that we had coming into the weighted decision matrix were the way that the overcharge protection for the batteries was handled.  Design concept 1 utilized the over charge protection that is built into the batteries, while design concept 2 makes the use of an onboard computer to manage the batteries.

For generating the weighing factors, we used the relative customer importance rankings and the highest priority engineering characteristics from our QFD diagram.  This allowed us to make the best design decision possible, as our criteria weighting was based on the most important customer/stakeholder needs and the most relevant engineering characteristics.  Many of the metrics that would have been included in the weighted decision matrix were either estimated or omitted (if we felt we could not provide and accurate guess).  Had the time period of the project been longer, we would have been able to gather more information from Ford about the current battery pack and possible conduct some experiments to gather operational data (such as the noise level of the cooling in the stock battery pack).  This would have given us a much better idea of what values to use for marginal and optimal metrics t throughout the matrix.

The evaluation criteria for the weighted decision matrix were taken from the customer/stakeholder requirements and the engineering characteristics from our QFD.  We felt this was the best method because we were using the importance rankings from the QFD, and we felt that our QFD contained the most relevant issues to design selection.

Each design concept was given a score of 1 – 2 if the design did not meet the criteria well, 3 if the design was average, and 4 if the design excelled in the area.

Due to the fact that our final design concepts were so similar, they received similar scores from the weighted decision matrix.  As a result changing the weighting of the various evaluation criteria is not likely to change the results.  In the end, design concept 2 (with the onboard computer system) was selected.  Our weighted decision matrix can be found here.

For the most part, changing the relative wieghts of the evaluation criteria would not change the end result.  The only areas that design concept 1 received a higher score than concept 2 is in manufacturing time and assembly time.  While these are important factors, the group benefits gained in terms of battery life and reliability that are gained from an onboard computer system would always be more important to the product.  However, it should be noted that if manufacturing time and assembly time were the ONLY evaluation criteria used, then design concept 1 would come out on top.

Continue to Task 12