Seat Comfort Analysis

Tesla

Mentors: Adrian Lew (Stanford) and Hussein Sanaknaki (Tesla)

Students: Ryan Cohen, Saige Manier, Jiawei Zhang 

Goal:

To build a framework to estimate the comfort of a seat with foam and a human occupant through Finite Element Analysis. 

Problem:

According to a feature piece published by the New York Times, the average driver spends 38,000 hours behind the wheel over the course of their lifetime. Throughout these nearly 800,000 miles of driving, the automobile seat is the key point of physical interaction between the vehicle and its occupant. Design of an automobile seat, therefore, must balance concerns of comfort, safety, and mass. Comfort specifically can be considered as a combination of static comfort, which concerns pressure distributions of an occupant seated in a stationary vehicle, and dynamic comfort, which comprises the transmission of road and vehicle vibrations to the occupant. Consequently, the cost of seat production in a typical automobile is second only to the engine, so there is significant value to optimizing this process. This drives the need to create a computational engineering analysis tool to guide the design.

What did the team do?

The team set up a model of a dummy with a seat and a foam cushion in LS-Dyna. The dummy was first sat on the cushion to obtain the static load distribution on the dummy and the seat, and then a strucutural modal analysis was performed, so as to make it possible to obtain the transient response of the dummy and the seat for an entire minute of driving; time-stepping through such time interval would take a lot longer computing time. The team then researched current trends and existing standards to translate a vibration spectrum into comfort, such as the Seat Effective Amplitude Transmissibility (SEAT) value and the Vibration Dose Value (VDV). The comfort then was quantified through these two quantities and through the oscillations in the pressure distribution on the cushion. Three different cushion foams were considered, finding that, out of the three, the cushion with the less dense foam was the most comfortable.

The metrics shown here are in reference to a generic seat case, and NOT to an actual Tesla seat.