Pulsed Digital Oscillators for Electrostatic MEMS

This paper introduces a new actuation scheme for implementing Pulsed Digital Oscillators (PDOs) for electrostatic MEMS resonators. In this scheme, the capacitance of the device is biased with a voltage and it is periodically sampled. Short pulses of zero voltage are applied depending on the decisions taken by the oscillator loop. The paper discusses in detail the implementation of such electrostatic PDO (e-PDO) through a prototype and links the e-PDO to the conventional PDO theory. As an example, it is shown that with this actuation scheme it is possible to excite different resonances of the mechanical structure simply by changing the parameters of the feedback filter of the oscillator.Science Foundation Irelan

Sigma Delta Effects and Charge Locking in Capacitive MEMS under Dielectric Charge Control

This work investigates, analytically and experimentally, the effects induced by the use of a first-order sigma-delta feedback loop as a control method of dielectric charging for capacitive MEMS. This technique allows one to set a desired level of net charge in the dielectric of a MEMS device by continuously alternating the polarity of the actuation voltage. This control system displays a number of interesting effects, inherited from sigma-delta modulation, and not usually found in conventional MEMS applications, with the charge locking phenomenon being the most relevant. The convergence time and the effectiveness of the control method are also investigated and discussed

Dielectric charge control in electrostatic MEMS positioners / varactors

A new dynamical closed-loop method is proposed to control dielectric charging in capacitive MEMS positioners/ varactors for enhanced reliability and robustness. Instead of adjusting the magnitude of the control voltage to compensate the drift caused by the dielectric charge, the method uses a feedback loop to maintain it at a desired level: the device capacitance is periodically sampled and bipolar pulses of constant magnitude are applied. Specific models describing the dynamics of charge and a control map are introduced. Validation of the proposed method is accomplished both through discrete-time simulations and with experiments using MEMS devices that suffer from dielectric charging.Science Foundation Irelandti, ab - TS 24.04.1

Control of MEMS vibration modes with pulsed digital oscillators : part II — simulation and experimental results

This paper extends our previous work on the selective excitation of mechanical vibration modes in MEMS devices using Pulsed Digital Oscillators. It begins by presenting extensive simulation results using the set of iterative maps that model the system and showing that it is possible to activate two or three spatial modes (resonances) of the mechanical structure with a Pulsed Digital Oscillator (PDO). The second part of this paper presents experimental results corroborating the theory and simulation results. It is shown that it is possible to separately excite vibration modes of the device by setting a few parameters of the PDO structure such as the sampling frequency and the sign of the feedback loop.Science Foundation IrelandOther funderSpanish government, TEC2007-67951/MIC (FEDER) projectti, sp, ke, ab - TS 28.02.1

3Cat-1 project: a multi-payload CubeSat for scientific experiments and technology demonstrators

This article introduces 3Cat-1, the first project of the Technical University of Catalonia to build and launch a nano-satellite. Its main scope is to develop, construct, assemble, test and launch into a low Earth orbit a CubeSat with seven different payloads (mono-atomic oxygen detector, graphene field-effect transistor, self-powered beacon, Geiger radiation counter, wireless power transfer (WPT), new topology solar cells and WPT experiment), all fitted in a single-unit CubeSat. On one hand, this is mainly an educational project in which the development of some of the subsystems is carried out by undergraduate and postgraduate students. The satellite demonstrates its capabilities as a cost-effective platform to perform small scientific experiments and to demonstrate some of the new technologies that it incorporates