Customer Tailored Active Weatherstrip Design

Providing quality sealing to automobile doors is a challenging problem due to the inherent design tradeoffs between a) small closing effort for high customer satisfaction and quality perception, and b) large sealing forces to ensure effective water and noise isolation. A new paradigm to overcome this tradeoff is active seals using smart materials which provide two separate operational states; thus, decoupling closing effort and sealing force allowing for simultaneous improvement. While engineering functionality dictates that the sealing force should be high, the closing effort is governed by the human/seal interaction; making the optimal load profile harder to identify. This paper describes a methodology to synthesize active seals with closing force profiles customizable to the customer preferred feel of door closure while increasing the sealing force for improved water and noise isolation. To identify preferred closing force profiles, a formal customer behavioral study was conducted with an on-vehicle closing force profile emulator which allowed subjects to experience and select different profiles. While there are many possible embodiments to achieve the preferred load profiles, in this paper an active mechanism insert is presented which provides two operational states by leveraging a Shape Memory Alloy actuated five-bar-mechanism customized to a customer preferred closing force profile in the martensite phase and high sealing force when heated to the austenite phase. For this SMA mechanism, a model based genetic algorithm optimization method is described for synthesis generalized for any customer closing load profile. This method was utilized to design, fabricate and experimentally characterize an SMA mechanism-based active seal capable of producing the most popular closing force profile determined by the behavioral study, and when activated, generating high sealing force. The described synthesis process is applicable to a wide range of closing profiles and can be used to tailor active seal closing profiles to target groups of customers on individual vehicle platforms improving customer satisfaction and perceived qualitywhile simultaneously improving sealing performance.