Maryna Lishchynska

Energy-Based Approach to Adaptive Pulse Shaping for Control of RF-MEMS DC-Contact Switches

This paper presents a closed-form analysis to design a pre-shaped open-loop driving actuation waveform to reduce the bouncing effect while maintaining fast switching of a microelectromechanical system contact switch. A single-degree-of-freedom model and the principle of energy conservation were utilized to design a shaped voltage waveform to close the switch with low impact speed. The method can easily adapt the voltage waveform to the variance of pull-in voltages due to imperfect manufacturing and to observed pull-in voltage drift during operation. The analytical calculation of the actuation pulse and the closure time of the switch with near zero velocity agree with simulation and are validated experimentally on the set of cantilever switches. It is shown that the analysis is also applicable for electrostatically actuated devices with more general geometries.

Modeling, simulation and validation of the dynamic performance of a single-pole single-throw RF-MEMS contact switch

This work presents a low-complexity dynamic model of a single-pole single-throw (SPST) ruthenium contact radio frequency (RF) MEMS switch. The model is based on a fabricated switch geometry and relies on dynamic Euler-Bernoulli beam theory incorporating the squeeze-film damping effect and contact mechanics interaction. Hertz theory and the JKR adhesion model are used in contact mechanics with a Gaussian probability surface asperity height distribution to model the interaction between the contact tip and drain. The simulated results for switch closing time, number and duration of bounces, contact deformation, settling time and dual-pulse control strategy are in good agreement with measured experimental results. The experimental validation proves that the proposed modeling framework can accurately simulate the dynamic behavior of the MEMS switch and serve as a design tool for dynamic optimization and development of control strategies that maximize the reliability of the MEMS switches.

Model-based analysis of switch degradation effects during lifetime testing

The paper reports on the transient analysis of the observed decrease in the actuation voltage of MEMS ohmic switches, under a stress condition. A finite difference model (FDM) is developed that provides insight into the contributions of various mechanical factors to the measured changes in switch performance. In particular, the proposed method allows us to investigate the effects of spring constant reduction and plastic deformation of the switch. Such an analysis cannot be done on the basis of an empirical fitting or existing analytical models. The presented method can be used in the lifetime evaluation of the switch and this application is demonstrated.

Integrated modeling of nonlinear dynamics and contact mechanics of electrostatically actuated RF-MEMS switches

In this work, a novel nonlinear dynamic model is developed to investigate the bouncing and deformation behaviors of an electrostatically actuated, ohmic-contact RF-MEMS switch. The model accounts for a real geometry, the electrostatic actuation, squeeze-film damping effect, and the nonlinear elastic-plastic contact mechanics using Hertz theory. A low-complexity formulation based on finite differential analysis is employed to solve the model equations in the time-domain. The proposed methodology is validated using a real four-contact RF-MEMS switch with complex geometry. The simulation results of the switch performance in the on-stage (closure) are in good agreement with experimental measurements demonstrating that the model is very effective in capturing the bouncing and contact deformation phenomena accurately. It is foreseen that the proposed approach will be instrumental in providing a better insight into the reliability of MEMS switches and will, ultimately, found a basis of developing and implementing control strategies to maximize their lifetime.

Distributed Adaptive Networked System for Strain Mapping

Separately, context-aware sensing and networked sensing systems have been fast progressing research domains. The emergence of wireless sensor networks (WSN) has introduced a way of implementing a distributed self-organized intelligence in myriads of sensing applications. In this work, WSN and sensing technologies are combined to monitor behavior of a target object. The paper presents design and implementation of a distributed adaptive networked system for strain mapping in a wooden table. The system is intended to provide real-time data on strain development in the target object. The strain gauge deployment layout is designed based on comparison between simulated strain results and strain interpolation on various numbers of sensors. Clustering of densely deployed strain sensors, data collection and processing is organized using tiered wireless network. Experiments on capturing the evolution of strain distribution in an object subject to various loading conditions were carried out and results are reported.

Optimising dynamic behaviour of electrostatically actuated MEMS contact switch

The reliability of the electrostatically actuated MEMS contact switches is known to be significantly undermined by the unstable dynamic behaviour of devices. High impact forces, bouncing at the contact and oscillations upon release result in substantial mechanical damage to the contacts and the switch compromising the functionality of the switch and reducing its lifetime. Certain effects become more pronounced, such as stiction causing ‘fail-to-open’ malfunctions, resistance increases leading to degraded performance, as well as fracture. To address the issue of the dynamic instability of the switch behaviour this work employs Finite Element Analysis (FEA), linear and nonlinear system identification techniques and optimal control theory to study the dynamic performance of the switch and optimise (soften) its dynamic behaviour by establishing an actuation input voltage that substantially reduces or eliminates the instabilities.

A multi-modular approach for design and evaluation of context information interactive systems

In the pervasive environment, the context, the data/information processing system and the human being comprise an information chain, along which the information from the context is conducted to the user in a comprehensive way. However, current context-aware systems and methodologies are more concerned about the processing systems without sufficient consideration about the relationships between all three parties on the chain, causing a lack of comprehensiveness. Therefore, a high level design and evaluation approach is proposed in this paper targeted towards providing an abstract design guideline for context-aware systems development and an evaluation method assessing eight selected parameters related to all three parties on the information chain and their relationships. Three typical modular systems are demonstrated, which present more intuitive and comprehensive representation by following the proposed design guideline. These three systems are also evaluated with an overall consideration of the whole information lifecycle, using the proposed method.