Now showing 1 - 10 of 39
  • Publication
    Bifurcation Scenarios in Electrostatic Vibration Energy Harvesters
    In this paper, we present numerical bifurcation analysis of an electrostatic vibration energy harvester operating in constant-charge mode and using the in-plane gap closing transducer. We show how the system can be represented as a nonlinear oscillator and analysed using methods of nonlinear dynamics. We verify previous analytical theories and explain the behaviour of these energy harvesters, particularly in the regime between the first period doubling bifurcation and chaos.
  • Publication
    Analytical Approach to Statistical Logic Cell Delay Analysis and its Extension to a Timing Graph
    In this paper we propose a new methodology to determine the delay of combinational circuits within the framework of statistical static timing analysis (SSTA). The methodology is based on exact analytical solutions for the probability density functions of logic gate delays. Assuming initial delays of the input arrival times and operation time of gates to be normally distributed, the non-Gaussian distribution of the resulting delay of a gate is obtained, as well as its first two moments. This allowed us to propose a novel closed-loop algorithm for the calculation of delay propagation in combinational circuits. Possible extensions and future steps are discussed.
  • Publication
    Semi-Analytical Method for the Extraction of the System Parameters in Application to Kinetic Energy Harvesters
    In this paper, we propose a technique to extract system parameters of nonlinear MEMS devices using a combination of model reduction and nonlinear optimization. The model is tested on a MEMS energy harvesting device employing magnetic actuation and piezoelectric energy conversion.
  • Publication
    Mode-locking in a network of kuramoto-like oscillators
    In this paper we consider a network of phase oscillators. We develop the equations that model the time evolution of the phase of each oscillator in the network. The oscillator represents a modified Kuramoto oscillator and in this study we discuss how these modifications are obtained. In the context of this study, we use this network to model a network of PLLs for distributed clock applications. We analyse analytically and numerically the synchronisation modes of this system for different types of the coupling function. We show that depending on the properties of the coupling function, the network displays either multiple coexisting synchronisation modes or only a single synchronisation mode. While in the context of clock generation, multiple synchronisation modes coexisting in the system at the same parameters are a parasitic phenomenon. However in the context of other application such as associative memory models, mode-locking can be seen a useful phenomenon. The results provide a deeper understanding of globally synchronised clock networks with applications in microprocessor design.
      303Scopus© Citations 2
  • Publication
    Complete electromechanical analysis of electrostatic kinetic energy harvesters biased with a continuous conditioning circuit
    This paper presents a comprehensive electromechanical study of an electrostatic kinetic energy harvester (eKEH) biased with a continuous voltage. This simple circuit refers to any capacitive transducer with an in-built voltage source, such as an electret, or DC biased transducer connected directly to a resistive load. It is commonly used for the characterisation of experimental transducers. However there is a void of any unified discussion focusing on the circuits influence on the transducer, due to electromechanical coupling in the transducer. The electromechanical coupling causes numerous nonlinear effects, any of which can result in inconsistent results and disjointed conclusions of experimental devices. This article seeks to present analytic tools which can be employed for systems of this type and discusses some of the results obtained from these techniques. Along with analysis and characterisation of the circuit dynamics, the results are compared with an experimental device and presented in terms of design of the system and conclusions drawn relating to the optimum operation point.
      270Scopus© Citations 10
  • Publication
    Statistical Simulations of Delay Propagation in Large Scale Circuits Using Graph Traversal and Kernel Function Decomposition
    In this paper we propose a new methodology to determine the delay of combinational logic circuits within the framework of statistical static timing analysis (SSTA). A new algorithm for the traversing of the timing graph is created and combined with a new technique of kernel function decomposition to find delay propagation through such a circuit. Assuming initial delays of the input signals and operation time of gates to be normally distributed, the exact analytical solution for a non-Gaussian probability density functions (PDF) of the resulting delay is obtained. Then, the approximation of a non-Gaussian PDF by a linear combination of kernel functions is proposed, and the initial Gaussian assumption is relaxed. This allowed us to build a novel closed-loop algorithm for the calculation of delay propagation in combinational circuits. Possible extensions and future steps are discussed.
      308Scopus© Citations 4
  • Publication
    Semianalytical model for high speed analysis of all-digital PLL clock-generating networks
    In this paper, we propose the model of a network consisting of All-Digital Phase-Locked Loop Network in application to Clock-Generating Systems. The method is based on a solution of a system of non-linear finite-difference stochastic equations and allows us to perform high speed simulations of a distributed Clock Network on arbitrary topology. The result of our analysis show a good agreement with experimental measurements of a 65nm CMOS All-Digital Phase-Locked Loop Network.
      311Scopus© Citations 3
  • 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.
      246Scopus© Citations 2
  • Publication
    Wideband electrostatic Vibration Energy Harvester (e-VEH) having a low start-up voltage employing a high-voltage integrated interface
    This paper reports on an electrostatic Vibration Energy Harvester (e-VEH) system, for which the energy conversion process is initiated with a low bias voltage and is compatible with wideband stochastic external vibrations. The system employs the auto-synchronous conditioning circuit topology with the use of a novel dedicated integrated low-power highvoltage switch that is needed to connect the charge pump and flyback - two main parts of the used conditioning circuit. The proposed switch is designed and implemented in AMS035HV CMOS technology. Thanks to the proposed switch device, which is driven with a low-voltage ground-referenced logic, the e-VEH system may operate within a large voltage range, from a pre-charge low voltage up to several tens volts. With such a high-voltage e-VEH operation, it is possible to obtain a strong mechanical coupling and a high rate of vibration energy conversion. The used transducer/resonator device is fabricated with a batch-processed MEMS technology. When excited with stochastic vibrations having an acceleration level of 0.8 g rms distributed in the band 110-170 Hz, up to 0.75 μW of net electrical power has been harvested with our system. This work presents an important milestone in the challenge of designing a fully integrated smart conditioning interface for the capacitive e-VEHs.
      362Scopus© Citations 17
  • Publication
    Method of Equivalent Currents for the Calculation of Magnetic Fields in Inductors and Magnets with Application to Electronics
    Magnetic components are essential in many applications of electronics. Despite a very clear understanding of magnetic phenomena developed from first principles of Electromagnetics and Maxwell’s equations, modelling of the magnetic field, flux and force in a particular system can be a very challenging problem. Often, direct calculations are avoided, and a phenomenological model describing magnetic interactions is used instead. There are a number of methods which can be used for the modelling of the magnetic field due to magnetic materials and inductors and which can provide detailed and predictive information on such systems. Multi-physics scientific packages utilising finite-element methods are among the most common tools as they can solve a wide range of different problems and employ universal numerical algorithms. As a trade-off, they are very resource-intensive and have a low speed of execution. As an alternative, one can develop simulation techniques utilising magnetic dipoles or equivalent currents. These methods are less resource-intensive and very fast; however, they also have their limitations. This paper presents a method of equivalent currents developed for the fast calculation of the magnetic field and flux. We show the application of the method to inductors and permanent magnets that have a particular importance in power electronics and electromagnetic kinetic energy harvesting.