Using Failure Mode and Effects Analysis to design a comfortable automotive driver seat.
Given enough time and use, all designs will fail. There are no fail-free designs. This is especially true when it comes to automotive seating comfort where the characteristics and preferences of individual customers are many and varied. To address this problem, individuals charged with automotive seating comfort development have, traditionally, relied on iterative and, as a result, expensive build-test cycles. Cost pressures being placed on today's vehicle manufacturers have necessitated the search for more efficient alternatives. This contribution aims to fill this need by proposing the application of an analytical technique common to engineering circles (but new to seating comfort development), namely Design Failure Mode and Effects Analysis (DFMEA). An example is offered to describe how development teams can use this systematic and disciplined approach to highlight potential seating comfort failure modes, reduce their risk, and bring capable designs to life.
Three-dimensional vibration transmission through the upper limb when performing reaching movements in vehicle
Whole body vibration (WBV) transmission to vehicle occupants is a function of both vibration characteristics and human posture/movement. The majority of earlier studies investigating biomechanical responses to WBV have considered only a static posture. However, vibration transmission can be affected by dynamic movements when reaching in vehicle and may be transmitted in three-dimension (3D). This study investigates vibration transmission to the upper extremities with changes in posture/movement along the intended reach trajectory under selected sinusoidal WBV conditions. In biodynamic WBV experiments, 21 subjects performed a reaching task to targets located in the right hemisphere under vibration exposure. Intermediate targets were also placed in the expected trajectories of hand movements. 3D biodynamic responses are characterised as a function of upper body posture. This study establishes the empirical database necessary to support a biodynamic model taking into consideration human activity to predict r...
Pressure Induced Discomfort in Seated Human Back Regions
A study of interface pressure discomfort on seated human back regions was conducted using the category production method. Twelve subjects, six men and six women, took part in the experiment. When a subject was seated and supported with the seat cushion and backrest, stimulus pressure on the back was generated by a wooden block from behind the components of a car seat backrest. Disregarding the effect of backrest padding, the exposure area of the pressure was approximately 148.5 an2. The pressure level was regulated when the block was mechanically driven forward by a motor andor when a block of different thickness ranging from 5 to 35 mm at a 5 mm interval was used. Each stimulus exposure lasted 60 seconds. The subject’s task was to regulate the pressure stimulus to match a discomfort level designated using a five-category 50-point rating scale. Six back regions, from the sacral up to the shoulder, were tested to match two discomfort levels, “very slight” and “medium”. The produced pressures for equal discomfort differ significantly among back regions and between two discomfort levels. In matching a discomfort level, the produced pressure in the lower scapular region was the highest while that in the shoulder region the lowest. At “very slight” discomfort the lumbar region produced a pressure of 38 mmHg, and at “medium” discomfort about 52 mmHg. Female subjects produced significantly less pressure than male subjects. The results indicate that the lumbar region is more sensitive to interface pressure than the scapular region. Any measures to promote lumbar support in automotive seats should not inadvertently incur excessive lumbar pressure. As criterion for avoiding pressure discomfort, 25th percentile pressures at “very slight” discomfort are provided. The work contributes to the knowledge of human pressure perception, and it also has practical applications for setting industrial standards of automotive seat evaluation.