title: NiMH battery forensics: Instrumentation, modelling and prognostics for identifying failure

authors: Leijen, Petrus Jozef Martinus

subjects: NiMH

abstract: Battery forensics is a growing research field that is becoming increasingly important with the introduction of hybrid-electric and electric vehicles. The need to correctly diagnose battery condition and predict signs of early failure is well recognised. Many presently used techniques are only applicable to laboratory situations where sensitive measurement is required or where complicated mathematical approaches are needed to assess battery condition. Advanced techniques are explored, such as extended Kalman filtering, to identify the challenges associated with analysis of multi-cell battery modules. Energy-recycling hardware is developed that is capable of efficiently cycling energy to and from cells connected in a series configuration. Switching a supercapacitor-bank-based energy store between series and parallel configurations, coupled with a bidirectional switch-mode power-supply, ensures that maximum energy is retained during the analysis cycle. Extended Kalman filtering (EKF) applied to three different battery models was used to quantify the internal component values of the battery equivalent circuits. The bulk-surface model was determined to be the most appropriate for the Toyota Prius battery modules as the EKF predicted component values converge to stable values, and the recovered voltage trace has a low error. However, the computational complexity when considering 12 series-connected NiMH cells, with their individual component variation with state-of-charge and state-of-health, make the EKF approach unviable. The data harvested during the energy recycling is used to calculate a new effective capacitance measure which relates directly to battery state-of-health. Not only is there a direct relationship between effective capacitance and state-of-health, but the (Q,V) coordinate of maximum effective capacitance on the charge-voltage plane, captured during battery discharge, is able to distinguish clearly between ordinary ageing and catastrophic cell failures.

text: NiMH battery forensics: Instrumentation, modelling and prognostics for identifying failure Battery forensics is a growing research field that is becoming increasingly important with the introduction of hybrid-electric and electric vehicles. The need to correctly diagnose battery condition and predict signs of early failure is well recognised. Many presently used techniques are only applicable to laboratory situations where sensitive measurement is required or where complicated mathematical approaches are needed to assess battery condition. Advanced techniques are explored, such as extended Kalman filtering, to identify the challenges associated with analysis of multi-cell battery modules. Energy-recycling hardware is developed that is capable of efficiently cycling energy to and from cells connected in a series configuration. Switching a supercapacitor-bank-based energy store between series and parallel configurations, coupled with a bidirectional switch-mode power-supply, ensures that maximum energy is retained during the analysis cycle. Extended Kalman filtering (EKF) applied to three different battery models was used to quantify the internal component values of the battery equivalent circuits. The bulk-surface model was determined to be the most appropriate for the Toyota Prius battery modules as the EKF predicted component values converge to stable values, and the recovered voltage trace has a low error. However, the computational complexity when considering 12 series-connected NiMH cells, with their individual component variation with state-of-charge and state-of-health, make the EKF approach unviable. The data harvested during the energy recycling is used to calculate a new effective capacitance measure which relates directly to battery state-of-health. Not only is there a direct relationship between effective capacitance and state-of-health, but the (Q,V) coordinate of maximum effective capacitance on the charge-voltage plane, captured during battery discharge, is able to distinguish clearly between ordinary ageing and catastrophic cell failures.

year: 2016

title: A novel two stage scheme utilizing the test set for model selection in text classification

authors: Pfahringer, Bernhard

subjects: computer science

abstract: Text classification is a natural application domain for semi-supervised learning, as labeling documents is expensive, but on the other hand usually an abundance of unlabeled documents is available. We describe a novel simple two stage scheme based on dagging which allows for utilizing the test set in model selection. The dagging ensemble can also be used by itself instead of the original classifier. We evaluate the performance of a meta classifier choosing between various base learners and their respective dagging ensembles. The selection process seems to perform robustly especially for small percentages of available labels for training.

text: A novel two stage scheme utilizing the test set for model selection in text classification Text classification is a natural application domain for semi-supervised learning, as labeling documents is expensive, but on the other hand usually an abundance of unlabeled documents is available. We describe a novel simple two stage scheme based on dagging which allows for utilizing the test set in model selection. The dagging ensemble can also be used by itself instead of the original classifier. We evaluate the performance of a meta classifier choosing between various base learners and their respective dagging ensembles. The selection process seems to perform robustly especially for small percentages of available labels for training.

year: 2005

title: HIEMPA: Hybrid Instruments from Electroacoustic Manipulation and Models of Pütorino and Aquascape

authors: Whalley, Ian

subjects: music

abstract: The HIEMPA project combined a team of people with technical, artistic, environmental and cultural expertise towards an artistic outcome aiming to extend the New Zealand sonic art tradition. The work involved collecting audio samples from the aquascape of the Ruakuri Caves and Nature Reserve in Waitomo, South Waikato, New Zealand; and samples of a variety of pütorino – a New Zealand Mäori wind instrument. Following a machine learning analysis of this audio material and an analysis of the performance material, hybrid digital instruments were built and mapped to suitable hardware triggers. The new instruments are playable in realtime, along with the electroacoustic manipulation of pütorino performances. The project takes into account the environmental and cultural significance of the source material, with the results to be released as a set of compositions. This paper discusses the background research and process of the project.

text: HIEMPA: Hybrid Instruments from Electroacoustic Manipulation and Models of Pütorino and Aquascape The HIEMPA project combined a team of people with technical, artistic, environmental and cultural expertise towards an artistic outcome aiming to extend the New Zealand sonic art tradition. The work involved collecting audio samples from the aquascape of the Ruakuri Caves and Nature Reserve in Waitomo, South Waikato, New Zealand; and samples of a variety of pütorino – a New Zealand Mäori wind instrument. Following a machine learning analysis of this audio material and an analysis of the performance material, hybrid digital instruments were built and mapped to suitable hardware triggers. The new instruments are playable in realtime, along with the electroacoustic manipulation of pütorino performances. The project takes into account the environmental and cultural significance of the source material, with the results to be released as a set of compositions. This paper discusses the background research and process of the project.

year: 2008