Paulus P.L. Regtien

Modeling Battery Behavior for Accurate State-of-Charge Indication

Li-ion is the most commonly used battery chemistry in portable applications nowadays. Accurate state-of-charge (SOC) and remaining run-time indication for portable devices is important for the users convenience and to prolong the lifetime of batteries. A new SOC indication system, combining the electromotive force (EMF) measurement during equilibrium and current measurement and integration during charge and discharge, has been developed and implemented in a laboratory setup. During discharge, apart from simple Coulomb counting, the effect of the overpotential is also considered. Mathematical models describing the EMF and the overpotential functions for a Li-ion battery have been developed. These models include a variety of parameters whose values depend on the determination method and experimental conditions. In this paper the battery measurement and modeling efforts are described. The method of implementing the battery model in an SOC indication system is also described. The aim is an SOC determination within 1% inaccuracy or better under all realistic user conditions, including a wide variety of load currents and a wide temperature range. The achieved results show the effectiveness of our novel approach for improving the accuracy of the SOC indication.

Battery aging and its influence on the electromotive force

Li-ion is currently the most commonly used battery chemistry in portable applications. Accurate state-of-charge (SOC) and remaining run-time indication for portable devices is important for user convenience and to prolong the lifetime of batteries. The actual SOC algorithms, which the main companies use in practice, make use of the so-called electromotive force (emf). In these SOC systems it is assumed that the emf of an Li-ion battery only depends on aging to a limited extent. In this paper, novel emf measurement and modeling efforts are presented as a function of battery aging. As will be shown, a better understanding of this dependence is useful for improving SOC accuracy.

Heat transfer in a MEMS for microfluidics

Paper presents an 1D model for the heat transfer in a limited but significant region of an actuator?sensor structure for the determination of fluid and flow characteristics. As an essential step for the design of this structure, the usefulness of the model in the framework of the structure?s functionality is underlined. In the first part of the work, the main heat transfer mechanisms are detailed by qualitative and quantitative evaluations. The 1D model is derived from the heat rate balance of the region we are interested in. In the second part of the work, we compare the data obtained by simulating the 1D model with the experimental data. Also, some full 3D simulations of the fluid flow and heat transfer are made using a commercial software package. Part of these numerical results are compared with the corresponding experimental data. The modeling errors are discussed for both sets of comparisons. Finally, we comment the merits of the 1D model versus the 3D approach. The results obtained herein might be directly used for various thermally based actuators and sensors for flow control and measurement both in micro and macro world.

A 3 × 1 integrated pyroelectric sensor based on VDF/TrFE copolymer

Abstract This paper presents an integrated pyroelectric sensor based on a vinylidene fluoride—trifluoroethylene (VDF/TrFE) copolymer. A silicon substrate that contains field-effect transistor (FET) readout electronics is coated with the VDF/TrFE copolymer film using a spin-coating technique. On-chip poling of the copolymer has been applied using a step-wise poling at room temperature. The copolymer deposition and polarization are compatible with semiconductor technology. An array of 3 × 1 integrated pyroelectric sensor has been realized. The current and voltage sensitivities and noise of this sensor have been measured. Voltage noise decreases with increasing frequency, and it is 2 nV (Hz) −1 2 at 100 kHz.

Time-of-flight estimation based on covariance models

We address the problem of estimating the time-of-flight (ToF) of a waveform that is disturbed heavily by additional reflections from nearby objects. These additional reflections cause interference patterns that are difficult to predict. The introduction of a model for the reflection in terms of a non-stationary auto-covariance function leads to a new estimator for the ToF of an acoustic tone burst. This estimator is a generalization of the well known matched filter. In many practical circumstances, for instance beacon-based position estimation in indoor situations, lack of knowledge of the additional reflections can lead to large estimation errors. Experiments show that the application of the new estimator can reduce these errors by a factor of about four. The cost of this improvement is an increase in computational complexity by a factor of about seven.

Poiseuille number for the fully developed laminar flow through hexagonal ducts etched in silicon

This paper focuses on a main subject encountered in the design process of the hexagonal ducts etched in silicon, namely, the achievement of the Poiseuille number Po for the velocity field of the fully developed laminar flow. The particular shape of the duct is determined by silicon technology. This type of duct is the main part of a structure for the determination of fluid and flow parameters. We develop a procedure for obtaining Po versus the aspect ratio of the hexagonal cross section. The validity of this procedure is proven using different shapes of cross sections. We underline the merit of this procedure, namely, its applicability using a commercial software package in a rather straightforward manner. The results presented in this paper might be adapted for many other situations encountered both in micro and macro world where devices containing ducts having various non-circular cross sections are present.

A VDF/TrFE copolymer on silicon pyroelectric sensor: design considerations and experiments

For an optimal design of a VDF/TrFE (vinylidene fluoride trifluoroethylene) copolymer-on-silicon pyroelectric sensor, the one-dimensional diffusion equation is solved for the pyroelectric multilayer structure. Output current and voltage of the sensor are calculated. Improvement of the sensor can be obtained by: (a) etching the silicon substrate under the sensor element and (b) an additional VDF/TrFE copolymer layer as thermal isolation. Different noise sources for a pyroelectric sensor have been calculated. The dielectric noise dominates the noise sources. This conclusion has been verified by measured values.

Smart and Accurate State-of-Charge Indication In Portable Applications

Accurate state-of-charge (SoC) and remaining run-time indication for portable devices is important for the user-convenience and to prolong the lifetime of batteries. However, the known methods of SoC indication in portable applications are not accurate enough under all practical conditions. The method presented in this paper aims at designing and testing an SoC indication system capable of predicting the remaining capacity of the battery and the remaining run-time with an accuracy of 1 minute or better under all realistic user conditions, including a wide variety of load currents and a wide temperature range. At the moment Li-ion is the most commonly used battery chemistry in portable applications. Therefore, the focus is on SoC indication for Li-ion batteries. The basis of the proposed algorithm is current measurement and integration during charge and discharge state and voltage measurement during equilibrium state. Experimental results show the effectiveness of the presented novel approach for improving the accuracy of the SoC indication

Velocity field of the fully developed laminar flow in a hexagonal duct

The paper presents a study concerning the velocity field of the fully developed laminar flow in a hexagonal duct. This duct is the main part of an actuator–sensor structure used for the determination of fluid and flow parameters. The particular shape of the duct is determined by silicon technology. The central subject detailed herein is the building of an approximative analytical formula for the velocity field inside hexagonal ducts. We detail two approaches for this subject and we discuss their limitations in the practical circumstances by using the CFD-ACE+ software package for the fluid flow simulation. One approach is based on the point-matching method and another one is based on the generalised integral transform method. The both approaches are offering similar credibility, namely the maximum errors produced by using these formulae are, respectively, 5 and 12% for the middle part of the cross-section where the actuators and sensors are usually placed. The second approach is more suitable for flatter ducts or when the designer is interested in a small central region of the cross-section. The simple applicability of the inferred formulae contrasts with the classical and huge time consuming numerical approaches, these formulae being suitable tools in the design process of the structure operating in the micro-world. The results presented in this paper might be adapted for similar structures operating in the macro-world where devices containing ducts having various non-circular cross-sections are present and where the fully developed laminar flow of the incompressible and Newtonian fluids is concerned.

Measurement concepts: from classical transducers to new MEMS

In this paper a formalization of the measurement concept (mc) is presented. Based on this formalization, a classical measurement concept (cmc) supported by classical transducers is derived. Restrictions and inconveniences of the cmc are exposed when the evaluation of more characteristics is concerned (the so-called multi-measurement process). Using a new measurement concept (nmc) developed in this work, the main drawbacks of the cmc can be removed. The core of the nmc is an actuator–sensor structure. Some basic principles regarding the design of this new structure as a MicroElectroMechanical System (MEMS) are also mentioned. Developing a state-space representation of the classical transducer and the new structure, the practical implementations of both concepts are compared and the superiority of the nmc is proven. Finally, the nmc is illustrated with an example concerning the determination of fluid and flow parameters using MEMS.