Now showing 1 - 9 of 9
  • Publication
    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.
      712Scopus© Citations 23
  • Publication
    Control of MEMS vibration modes with Pulsed Digital Oscillators : Part I — theory
    The aim of this paper is to show that it is possible to excite selectively different mechanical resonant modes of a MEMS structure using Pulsed Digital Oscillators (PDOs). This can be done by simply changing the working parameters of the oscillator, namely its sampling frequency or its feedback filter. A set of iterative maps is formulated to describe the evolution of the spatial modes between two sampling events in PDOs. With this lumped model, it is established that under some circumstances PDO bitstreams related to only one of the resonances can be obtained, and that in the antioscillation regions of the PDO the mechanical energy is absorbed into the electrical domain on average. The possibility of selecting for a given resonant frequency the oscillation and antioscillation behaviour allows one to obtain oscillations at any given resonant mode of the MEMS structure.
      375Scopus© Citations 15
  • Publication
    Modelling of a charge control method for capacitive MEMS
    Charging of dielectric materials in microelectromechanical systems (MEMS) actuated electrostatically is a major reliability issue. In our previous work we proposed a feedback loop control method that is implemented as a circuit and that allows smart actuation for switches and varactors. In this paper we discuss system-level modeling of MEMS devices including all aspects of the system: proposed control method, charging dynamics and realistic models of the mechanical components of MEMS.
      456Scopus© Citations 5
  • Publication
    Excitation of multiple spatial modes of a MEMS cantilever in the pulsed digital oscillator
    The aim of this paper is to apply an approach that will allow us to consider different mechanical modes of a MEMS cantilever in the form of separate mass-spring-damper equations with the appropriate form of an external driving. In the paper, we focus on a specific MEMS cantilever and use a Pulsed Digital Oscillator (PDO) to keep self-sustained oscillations of the mechanical structure. By applying the order-reduction procedure to a partial differential equation that describes the transversal deflections, we obtain a system of coupled ordinary differential equations that describes the excitation of multiple spatial modes. On the basis of these ordinary differential equations, we formulate a set of iterative maps to describe the evolution of the modes between two sampling events. The numerical simulations we present are focused on the most common case when the first two mechanical modes are taken into consideration
  • Publication
    On some properties of the output of a pulsed digital oscillator working with multiple resonances
    In this paper, we study the possible output of the pulsed digital oscillator (PDO) with multiple resonant modes of the mechanical resonator in the feedback loop. PDOs are simple circuits that allow linear resonators to maintain self-sustained oscillations and can work as mass-change resonant sensors. For a resonant sensor, activation of higher vibration modes of a mechanical resonator can be a way to improve its performance. We show that the location of the sensing/actuation system affects the output and can enhance higher mechanical modes.
      314Scopus© Citations 2
  • Publication
    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.
      576Scopus© Citations 11
  • Publication
    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.
      432Scopus© Citations 3
  • Publication
    Dynamics of the MEMS pulsed digital oscillator with multiple delays in the feedback loop
    In this paper we apply methods of nonlinear dynamics to examine the behavior of the pulsed digital oscillator for microelectromechanical systems (MEMS). We study the regions of existence of oscillations and demonstrate the effect on these of including additional delays into the feedback loop.
      391Scopus© Citations 4
  • Publication
    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.
      312Scopus© Citations 12