Simulation of a Micro Electro-Thermal Actuation System Using ADAMS

A micro electro-thermal actuation system called BETV (Bidirectional Electro-Thermal Vibrator, see Fig. 1 below) is commonly used to control the inductive property of a micro magnetic circuit (see Fig. 2 below) or as a switch to turn on/off of an optical signal through slider output displacement. BETV utilizes alternating electric input applied on the terminals as energy source to generate the oscillation of the impact head due to repetitive contraction and expansion of different cross-sectional areas of the electric path under Ohmic heating (see Fig. 3). The impact head then collides with the slider and the slider moves accordingly.

           Fig. 1 Configuration of BETV                Fig. 2 Use BETV to change inductive property

Fig. 3 Repetitive expansion-contraction process of the impact head

Earlier Prof. Shih, W.P. had proposed a simplified lumped mass mathematical model to analyze the behavior of BETV (see Fig. 4 below); nevertheless, in this project a different approach using ADAMS software package was adopted.

Fig. 4 A lumped mass mathematical model of BETV

It was crucial to obtain accurate material properties such as damping and stiffness of contact surfaces in order to construct a representative model. Also, to be more efficient, reasonable assumptions like symmetry and planar motion must be made to save computing resources. Last but not least, in order to simulate the force induced, the impact head was treated as a electric circuit (see Fig. 5). The resultant force induced can be approximated by a saw-toothed waveform based on the theory of electric science, heat transfer, and solid mechanics (see Fig. 6).

Fig. 5 The energy transformation process of BETV

Fig. 6 Schematic diagram of the resultant force 

Via construction of equivalent driving forces, masses, simple beam elements, and joints (see Fig. 7 below), BETV was successfully reproduced in the virtual world and coincided well with the experimental data (see Fig. 8 below), which showed that it is applicable to simulate MEMS using ADAMS.

Fig. 7 Quarter of BETV in ADAMS/View environment

Fig. 8 Comparison of experimental test data and virtual test data (displacement v.s. time)