Journal of Mechanical Science and Technology 26 (1) (2012) 31~37 www.springerlink.com/content/1738-494x DOI 10.1007/s12206-011-1205-2 Development of multiple performance indices and system parameter study for the design of a MEMS accelerometer † Yong Il Kim, Chan Kyu Choi and Hong Hee Yoo * Department of Mechanical Engineering, Hanyang University, Seoul, 133-791, Korea (Manuscript Received May 12, 2011; Revised August 19, 2011; Accepted August 26, 2011) ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Abstract For the design of a MEMS accelerometer, proper performance indices should be defined and employed. Performance indices are ob- tained using either an experimental method or a numerical method. In the present study, a vibration analysis model of a MEMS acceler- ometer is introduced to calculate three performance indices: sensitivity, measurable acceleration range, and measurable frequency range. The accuracy of the vibration analysis model is first validated by comparing its modal and transient results with those of a commercial finite element code. Measurable acceleration and frequency ranges versus allowable errors for electrical and mechanical sensitivities are obtained and the effects of system parameter variations on the three performance indices are investigated. Keywords: Measurable acceleration range; Measurable frequency range; MEMS; Vibration analysis model ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- 1. Introduction MEMS accelerometers are frequently used to activate the safety system (air-bags) and the stability system (suspensions) [1] for automobiles. They are also frequently used for several mobile devices such as cellular phones, MP3 players, and portable game consoles. In such mobile devices, MEMS ac- celerometers are often employed for motion sensing. Since only small space is allowed for the mobile devices, MEMS accelerometers are widely used in those devices. Therefore, design technology for the MEMS accelerometer needs to be established in a systematic way. Since a micro machined accelerometer was first fabricated at Stanford University [2] in 1979, early stage research on MEMS accelerometers mainly focused on manufacturing technologies until 1990’s. Various kinds of bulk and surface micromachining technologies were introduced by several researchers (see, for instance, Refs. [3, 4]) and performances of various MEMS accelerometers were validated with ex- perimental results. From the late 1990’s, some results based on analysis models began to be reported. Static and dynamic behaviors of MEMS accelerometers employing single and multiple beam structures were analyzed [5]. Effects of geo- metric and inertial parameters on the sensitivity of MEMS accelerometers were analyzed [6]. The performance of more advanced MEMS structures measuring 3 angular acceleration components as well as 3 translational acceleration components was also analyzed [7, 8]. In spite of various research results published so far, the performance of a MEMS accelerometer has been characterized mostly by single index such as sensi- tivity. The functional limit of the device such as measurable acceleration or frequency range has rarely been investigated in the literature so far. Even if bandwidth is often employed as a performance index, it is far larger than practical measurable frequency. The purpose of the present study is to introduce proper indi- ces to measure the performance of a MEMS accelerometer using a reliable vibration analysis model. In addition to sensi- tivity which is widely used as the principal performance index, two more performance indices are introduced: measurable acceleration range and measurable frequency range. The rela- tion between measurable acceleration or frequency range and the measuring accuracy of the MEMS accelerometer (named as allowable error) is obtained and the effects of system pa- rameter variations on the variations of the three performance indices are investigated for the design of the MEMS acceler- ometer. 2. Modeling of a MEMS accelerometer A capacitive MEMS accelerometer which consists of a sin- gle beam and a proof mass is employed in the present study. Fig. 1 shows the configuration of a MEMS accelerometer. The mean values of material and geometric properties of the MEMS accelerometer are given in Table 1. When a body to † This paper was recommended for publication in revised form by Editor Yeon June Kang * Corresponding author. Tel.: +82 2 2220 0446, Fax.: +82 2 2293 5070 E-mail address: hhyoo@hanyang.ac.kr © KSME & Springer 2012