Airbags are designed to protect passengers from frontal or near-frontal crashes. Their designs and performance have improved dramatically since their introduction in the 1980s. Exhibit 5.19 shows a diagram of an airbag system. Modern airbag systems consist of seven basic parts: crash sensors (either two behind the bumper or one inside the engine and a second inside the passenger area), an inflator unit that determines the force of a collision and whether or not to inflate the airbag, the airbag itself (the inflator unit and airbag together is called the airbag module), a diagnostic unit that runs a test on the airbag system to ensure that it is functioning correctly, a wiring harness that connects all components of the system together, a clock spring that connects the steering wheel with the airbag system, allowing the steering wheel to be turned while maintaining an electrical connection with the airbag and other electronics in the steering wheel, and an indicator lamp on the dashboard that lights and remains lit if there is a problem with the system.23 Airbag reliability is an important concern. Several types of failures can occur: failure to deploy (sensor failure, inflator unit failure, or clock spring failure), which can result in serious injury or death, deploys at the wrong time (inflator unit failure causing a delay in deployment), faulty wiring in the wiring harness, short circuits in the diagnostic unit (showing correct functioning when it does not or a false indication of a failure), a clock spring failure (in which the airbag may not deploy or cruise control bay be disabled), or an indicator lamp failure (most often, a false indication of a problem, which requires costly labor. The vehicle manufacturer, Astro Automotive, has several options for procuring the parts from suppliers that are needed to build the airbag system for a new vehicle model. Three suppliers manufacture sensors and two suppliers build airbag modules and also sell compatible wiring harnesses and clock springs. Astro Automotive’s Research and Development department has designed its own diagnostic unit to ensure compatibility with other electronic systems in the vehicles. The indicator lamp can be purchased from two suppliers who also provide headlamps, taillights, and other illumination accessories for vehicle interiors. Exhibit 5.20 shows the costs and tested reliabilities of each component from the suppliers. 

Case Questions for Discussion: 

1. Using the data presented, identify the supplier configuration that results in the lowest cost and highest cost airbag systems.

2. Using your calculations for question 1, what would be the reliability of the low- and high-cost systems?

3. What is the highest reliability that can be achieved? What would this cost?

4. Astro Automotive does not feel that the highest reliability that can be achieved from the existing components is acceptable, primarily because of the relatively low reliabilities of the airbag module and clock spring. The R&D department estimates that developing these new components with higher reliabilities will cost \($1.2\) million and that the unit manufacturing cost for the airbag module will be \($650,\) and the cost for the clock spring will be \($130.\) If the reliabilities for these components can be increased to 0.9999, how much can the system reliability be improved?

5. Compare the cost and reliability of the four design options (low cost, high cost, high reliability, and Astro-developed airbag module and clock spring). If Astro Automotive estimates selling 10 million vehicles, how many airbag systems will fail for each option? What design should the company choose? What are the risks that Astro Automotive might face? Explain your reasoning.

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EXHIBIT 5.20 Costs and Reliabilities of Airbag Components from Suppliers Astro Western Automotive Controls Cost/ Reliability Cost unit Eastern Electronics Shanghai Firmware Victor Dayton illumination Lighting Reliability Cost/ Reliability Cost/ Reliability Cost/ Reliability Cost Reliability unit unit unit unit unit Sensors $85 09991 $100 0.9996 $50 0.9846 Airbag module $500 09886 $325 0.9761 $425 0.9828 Diagnostic unit $385 0,9962 $225 09714 $275 0.9816 $300 0.9907 Wiring harness $30 09989 $50 0.9992 $25 0.9845 Clock spring $75 09804 $90 0.9822 $100 0.9866 Indicator lamp $40 0.9983 $60 0.9954