| Engineering design starts with the definition of design requirements. These requirements define the design problem and must be satisfied for a solution to be acceptable. While many design methodologies exist for defining design requirements, none presently provides a systematic approach for designers to challenge requirements. Yet, Pahl and Beitz, Hazelrigg, and Suh all argue that a designer should continually question the need for each requirement and refine them as the product evolves. Thus, there exists a need to develop a comprehensive method that enables a designer to verify, review/question, and revise requirements throughout the design process. This research uses the design of a combined trash and recycling collection vehicle for Environmental America Inc. (EAI) as a case study to illustrate the positive impact of challenging customer requirements, offer examples of why requirements should be challenged, and describe the successful process used. Two unique design concepts are compared and the catalyst for challenging requirements is created when the seemingly superior concept does not satisfy one of the design requirements. The process of challenging requirements results in the development of three guiding principles. Three concepts, physical testing, defining more customers and refining their needs, and tracing a requirement to its original design decision, form the basis for the development of a systematic design method. Ultimately, this thesis provides the foundation for the development of a formal design method to challenge requirements that can be adopted to different types of design problems and accepted by both academia and industry. |
