Efficient Physical Modeling of MEMS Energy Harvesting Devices With VHDL-AMS

In this paper, we propose a VHDL-AMS implementation of a physical model of a microelectromechanical systems (MEMS) piezoelectric microgenerator. Such an executable model acts as a bridge between specifications and fabricated devices. Usually, physical and geometrical parameters of electromechanical parts of a system are only considered in lower levels of the design flow, typically using finite-element tools, which, despite their accuracy, do not allow efficient optimization of the structure properties and dimensions. Thus, it would be very interesting to have a model of the entire harvesting system (the MEMS piezoelectric microgenerator cascaded with the electronic circuit) to perform efficient optimization. Some features like damping effects and process fluctuations have considerable impact on the performance of MEMS, especially the resonant structures. We propose a method of integrating such features early in the design flow, while keeping the simulation time reasonable. The resulting model is reusable, predictive (comparable to experimental results) and respects Kirchhoff laws. Consequently, it can be integrated in global simulation of multidomain and mixed signal systems like wireless sensor nodes.