Numerical modeling of 3-D comb drive electrostatic accelerometers structure (method of levitation force reduction) Slawomir Wiak and Krzysztof Smo ´lka Institute of Mechatronics and Information Systems, Technical University of Lodz, Lodz, Poland Abstract Purpose – The purpose of this paper is to discuss the numerical modelling of 3D structure of micro-electro-mechanical systems (MEMS) accelerometers. The general idea being discussed is the method of levitation force reduction, as the main source of incorrect mathematical model of comb drive structure. Design/methodology/approach – Accelerometers design is a highly interdisciplinary area and, therefore, different methods and tools have to be exploited. Dynamic accelerometer behaviour modelling has been performed by use of a new object-oriented model (NOOM), based on complex computer field and mechanical models. Findings – The paper describes methods of levitation force reduction in electrostatic comb drive structures based on electrostatic structural models and finite elements method. Research limitations/implications – In the present work, the authors limit themselves to the electrostatic energy domains. Practical implications – Both, mechanical and electric models of accelerometers give the input data for defining the object-oriented model, based on Matlab-Simulink platform, fulfilling the general demand of dynamic behaviour simulation of comb drive structure. The proposed by authors methodology could give valuable contribution to MEMS design methodology. Originality/value – A new methodology has been successfully applied to calculation of levitation force in different geometries of comb drive. This methodology could be useful for multidisciplinary MEMS systems. Keywords Object-oriented methods, Modelling, Vectors, Force measurement Paper type Research paper Introduction Actually, the task of the designer is complicated by the evidence that different energy domains, in general being mutually coupled, are involved when modelling micro-electro-mechanical devices, in the frame of more general micro-electro-mechanical systems (MEMS). Some specific codes based on finite element method (FEM) could be successfully applied to MEMS designing while microdomain physics are also taken into account. This paper deals with the methods of analysis of electrostatic accelerometers with comb drive structure. In surface micromachining, comb drives are the most commonly used actuators for moderate in-plane micro-displacements and micro-forces (van Spengen and Heeres, 2007). They are also often used as motion sensing in accelerometers. Accelerometers are important devices in the range of variety applications such as air bag actuation (by Analog and Sandia), microrobots, etc. The comb-drive accelerometers, The current issue and full text archive of this journal is available at www.emeraldinsight.com/0332-1649.htm Numerical modeling of 3-D comb drive 593 COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering Vol. 28 No. 3, 2009 pp. 593-602 q Emerald Group Publishing Limited 0332-1649 DOI 10.1108/03321640910940864