Brake engineers are very familiar with designing automotive brake systems to meet performance requirements such as those specified in FMVSS 105. However, merely complying with governmental regulations does not ensure that the resulting brake system will satisfy customers of the product. Many attributes of brake performance are characterized by our customers in very subjective terms. In many cases it is not apparent how to incorporate these subjective customer desires into our product designs. This paper describes a process for transforming customer preferences about brake system performance expressed in subjective terms into objective parameters for brake system design.
The process for converting customer preferences into design parameters involves several steps. The desires of the customer must be identified. This is often done in marketing clinics, customer interviews or surveys. Next, vehicle and brake system parameters which might relate to these subjective customer desires must be identified. A group of vehicles which demonstrate a range of values for these design parameters should then be assembled. Then a statistically significant sample group of the target customers are asked to subjectively rate these vehicles for each of the identified customer preferences. These customer evaluations should be obtained in a controlled manner, where all of the subjective ratings are done on a prescribed driving schedule which has been selected to address each area of customer preference. Finally these subjective rating data need to be correlated with the identified vehicle and brake system design parameters.
The strength of the correlation between a subjective rating and a design parameter indicates the importance of the design parameter. In addition the values for the subjective ratings can be used to identify acceptable ranges and target values for such design parameters. The lack of a statistical relationship is also valuable information for identifying where design freedoms exist.
The methodology proposed here can lead to brake systems which not only meet regulated performance requirements, but also result in systems which satisfy customers.