Monika Kwiecien

Control of an electromechanical hydrocephalus shunt--a new approach.

Hydrocephalus is characterized by an excessive accumulation of cerebrospinal fluid (CSF). Therapeutically, an artificial pressure relief valve (so-called shunt) is implanted which opens in case of increased intracranial pressure (ICP) and drains CSF into another body compartment. Today, available shunts are of a mechanical nature and drainage depends on the pressure drop across the shunt. According to the latest data, craniospinal compliance is considered to be even more important than mean ICP alone. In addition, ICP is not constant but varies due to several influences. In fact, heartbeat-related ICP waveform patterns depend on volume changes in the cranial vessels during a heartbeat and changes its shape as a function of craniospinal compliance. In this paper, we present an electromechanical shunt approach, which changes the CSF drainage as a function of the current ICP waveform. A series of 12 infusion tests in patients were analyzed and revealed a trend between the compliance and specific features of the ICP waveform. For waveform analysis of patient data, an existing signal processing algorithm was improved (using a Moore machine) and was implemented on a low-power microcontroller within the electromechanical shunt. In a test rig, the ICP waveforms were replicated and the decisions of the ICP analysis algorithm were verified. The proposed control algorithm consists of a cascaded integral controller which determines the target ICP from the measured waveform, and a faster inner-loop integral controller that keeps ICP close to the target pressure. Feedforward control using measurement data of the patients position was implemented to compensate for changes in hydrostatic pressure during change in position. A model-based design procedure was used to lay out controller parameters in a simple model of the cerebrospinal system. Successful simulation results have been obtained with this new approach by keeping ICP within the target range for a healthy waveform.

Correct processing of impedance spectra for lead-acid batteries to parameterize the charge-transfer process

Electro-chemical impedance spectroscopy is widely used to analyze electro-chemical systems. Most attention is paid to the double-layer capacitance and the charge-transfer resistance as they describe the electro-chemical process on the surface of the electrode. Both values can provide specific information about aging mechanisms, which diminish the surface area. This is of interest when capacity tests are restricted to determine the aging. For lead-acid batteries, for example, this is the case in applications like micro-hybrid vehicles or uninterruptible power supply systems. However, the interpretation of impedance spectra of lead-acid batteries necessitates proper measurements, elaborated verification of measurement validity, and a sufficient model of electro-chemical processes. In this work, impedance spectra, recorded on lead-acid test cells, are processed to identify the ohmic resistance, the double-layer capacitance, and the parameters of the charge-transfer reaction of the negative electrode. This electrode suffers from sulfation, a common aging mechanism in current applications. The aim of the paper is to define a correct processing of impedance spectra for lead-acid batteries, and to depict challenges. Furthermore, possible equivalent electrical circuit models for the negative electrode are evaluated regarding their dependencies on state of charge and current rate. Many of these aspects can be transferred to other electro-chemical systems.Graphical Abstract

Adaptive battery steering and management system for the optimized operation of stationary battery energy storage systems in multi-use applications

In stable electrical networks, such as the German one, the service of uninterruptible power supply (UPS) systems is only rarely called. Consequently the battery lifetime in this application is mostly restricted by calendar aging. The concept of multi-use describes here the delivery of additional services with a UPS during stable grid operation. The overall goal is to allocate the battery capacity and power according to the current state of health (SoH). Therefore, the Battery Steering and Management System (BSMS) was designed to allow for an optimal operation strategy over the full lifetime of a battery energy storage system (BESS). The BSMS combines a diagnostic unit with a management system that withholds an electrical and an aging model. The system is conceptualized to secure short term functionality as well as to predict long-term behavior and allow for operation planning. Over the lifetime of the battery the operation recommendation will adapt according to the batterys current status and its history. In addition, the paper presents briefly the basic concept of multi-use applications and the currently attractive markets for further services by a UPS.

Current research topics for lead-acid batteries

Abstract Since the lead–acid battery has been the predominant energy storage device in the automotive market for a long time, it is usually considered to be a mature commodity both for original equipment and for the aftermarket. Consequently, there has been little investment in research in this technology by the battery and car industries, by universities or by governments, in comparison with the rather large research effort that has been put into exploring alternative battery chemistries. Nevertheless, it is often overlooked that lead–acid automotive batteries have experienced many innovations continuously in response to new requirements in terms of functionality, durability, fuel economy and cost. The recent mainstream introductions of absorbent glass mat batteries (AGM), enhanced flooded batteries (EFBs) and battery monitoring sensors (BMS) are obvious examples of a continuous improvement. Moreover, collaborative industry research projects as well as venture capital–funded start-up companies have been addressing new applications such as the use of 48-V mild‐hybrid traction batteries. Whilst the emerging original equipment manufacturer (OEM) markets for hybrid propulsion batteries are dominated by advanced storage technologies, lead–acid batteries are also challenged in the established core business of 12-V starting–lighting–ignition (SLI) batteries. The reason for this development is that advanced storage technologies are progressing from the initial niche markets like luxury sports cars that can afford a very high price for weight reduction despite significant performance degradation at extreme temperatures. Challenges to the position of lead–acid from both new vehicle requirements and competing technologies will continue to grow over the next two decades. To defend the larger part of their established 12-V core business, and even more urgently to compete for new automotive applications like 48-V storage systems, lead–acid battery companies will need to accelerate the pace of innovation.

Analysis of characteristics for the identification of lead-acid battery technologies used in micro-hybrid vehicles

Due to advanced fuel-saving features, used in micro-hybrid vehicles, stresses on automotive batteries have significantly increased. To ensure a safe operation and avoid overloading the battery, its state has to be monitored constantly. However, due to the availability of different technologies of lead-acid batteries with distinct behavior, for a correct state estimation the battery type has to be known by the system. In this work, lead-acid batteries of different types and from different manufacturers are tested to find differentiating factors that can be used for on-line identification. This includes the analysis of both transient stress phases like starting the engine as well as rest periods. From the results of these tests, characteristics for the three battery types can be derived based on which identification can be performed.

FIRST RESULTS OF A NEW ELECTROMECHANICAL CONTROLLED EXTERNAL VENTRICULAR DRAINAGE IN A PORCINE MODEL

Acute increase of intracranial pressure (ICP) usually has to be treated with an external ventricular drainage (EVD). Current standard mechanical EVD carry a lot of disadvantages, which hypothetically could be bet- ter managed by a newly developed electromechanical EVD. In this report our first preliminary results of such an elec- tromechanical EVD applied in a porcine animal model are presented. The drainage was demonstrated to be both suc- cessful in monitoring and controlling elevated ICP, and able to detect slit ventricles due to overdrainage, if the indented target ICP was set too low.