Prognostic performance evaluation has gained significant attention in the past few years. * Curre... more Prognostic performance evaluation has gained significant attention in the past few years. * Currently, prognostics concepts lack standard definitions and suffer from ambiguous and inconsistent interpretations. This lack of standards is in part due to the varied enduser requirements for different applications, time scales, available information, domain dynamics, etc. to name a few. The research community has used a variety of metrics largely based on convenience and their respective requirements. Very little attention has been focused on establishing a standardized approach to compare different efforts. This paper presents several new evaluation metrics tailored for prognostics that were recently introduced and were shown to effectively evaluate various algorithms as compared to other conventional metrics. Specifically, this paper presents a detailed discussion on how these metrics should be interpreted and used. These metrics have the capability of incorporating probabilistic uncertainty estimates from prognostic algorithms. In addition to quantitative assessment they also offer a comprehensive visual perspective that can be used in designing the prognostic system. Several methods are suggested to customize these metrics for different applications. Guidelines are provided to help choose one method over another based on distribution characteristics. Various issues faced by prognostics and its performance evaluation are discussed followed by a formal notational framework to help standardize subsequent developments. * This is an open-access article distributed under the terms of the Creative Commons Attribution 3.0 United States License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Page 1. EVect of fuel type on morphology and reactivity of combustion synthesised MgAl2 O4 powder... more Page 1. EVect of fuel type on morphology and reactivity of combustion synthesised MgAl2 O4 powders I. Ganesh, B. Srinivas, R. Johnson, BP Saha, and YR Mahajan were rst calcined at around 1400°C to obtain an appreci-able ...
Prognostic performance evaluation has gained significant attention in the past few years. * Curre... more Prognostic performance evaluation has gained significant attention in the past few years. * Currently, prognostics concepts lack standard definitions and suffer from ambiguous and inconsistent interpretations. This lack of standards is in part due to the varied enduser requirements for different applications, time scales, available information, domain dynamics, etc. to name a few. The research community has used a variety of metrics largely based on convenience and their respective requirements. Very little attention has been focused on establishing a standardized approach to compare different efforts. This paper presents several new evaluation metrics tailored for prognostics that were recently introduced and were shown to effectively evaluate various algorithms as compared to other conventional metrics. Specifically, this paper presents a detailed discussion on how these metrics should be interpreted and used. These metrics have the capability of incorporating probabilistic uncertainty estimates from prognostic algorithms. In addition to quantitative assessment they also offer a comprehensive visual perspective that can be used in designing the prognostic system. Several methods are suggested to customize these metrics for different applications. Guidelines are provided to help choose one method over another based on distribution characteristics. Various issues faced by prognostics and its performance evaluation are discussed followed by a formal notational framework to help standardize subsequent developments. * This is an open-access article distributed under the terms of the Creative Commons Attribution 3.0 United States License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
The term Automated Contingency Management (ACM) has been used to describe intelligent systems cap... more The term Automated Contingency Management (ACM) has been used to describe intelligent systems capable of mission re-planning and control reconfiguration in the presence of a current health state diagnosis. While a diagnostics driven ACM capability designed to optimize multi-objective performance criteria remains a significant technical challenge, it cannot hope to overcome the fact that it will always be a reactive paradigm. This paper, therefore, introduces an automated contingency management paradigm based on both current heath state (diagnosis) and future health state estimates (prognosis). Including Prognostics in the control loop poses at least two additional challenges to ACM. First, future state prediction will, in general, have uncertainty that increases as the prediction horizon increases so adaptive prognosis routines that manage uncertainty are critical. Secondly, a warning period afforded by prognosis allows ACM to be split into a realtime "reactive" component and a non-real time "planning" component that considers temporal parameters and the potential impact of being proactive with mitigating action. The proactive ACM paradigm was developed and evaluated in the context of a generic mono-propellant system model in Simulink/Stateflow with diagnostics, prognostics and an optimal reconfigurable control system. Applications of Artificial Intelligence (AI) technologies in prognostics enhanced ACM system are briefly discussed. Preliminary results from the on-going research work are presented and the paper is concluded with remarks on future work.
Slip cast Y 2 O 3 stabilized Zirconia (8YSZ) ceramics was subjected to Conventional Ramp and Hold... more Slip cast Y 2 O 3 stabilized Zirconia (8YSZ) ceramics was subjected to Conventional Ramp and Hold (CRH), Rate Controlled (RCS) and Two Stage Sintering (2SS) methodologies. Sintered samples were characterized for their densities and grain size analysis by Scanning Electron Microscopy. The slip cast samples sintered by CRH and 2SS have achieved 98 -99 % of theoretical densities while RCS samples have exhibited a low density of 97 %. The samples exhibited an average grain size of 2.64 µm by 2SS sintering in comparison to 8.83 µm in case of CRH and 3.45 µm in case of RCS. Controlled pore growth associated with RCS, when compared to CRH methodology is mainly responsible for the relatively smaller grain size observed with RCS. A four fold decrease in grain size i.e. 2.64 µm observed with the two step sintering can be attributed to the fact that the first heating step to high temperature of 1550°C for a shorter duration closes the porosity without significant grain growth. The second step at 1375°C for a longer period of time imparts densification with limited grain growth.
Cordierite honeycombs with oxide compositions of 49.5-51 wt.% SiO 2 , 35.5-36 wt.% Al 2 O 3 and 1... more Cordierite honeycombs with oxide compositions of 49.5-51 wt.% SiO 2 , 35.5-36 wt.% Al 2 O 3 and 14-14.5 wt.% MgO were prepared from clay, talc, and alumina using conventional extrusion process. Effects of sintering parameters such as heating rate, soaking time, cooling rate as well as amount of calcined clay in the raw material compositions on the overall coefficient of thermal expansion (CTE) as well as thermal anisotropy in terms of CTE difference between the extrusion direction and across the extrusion direction of the cordierite honeycombs were studied. For this purpose, extruded honeycombs were sintered with various heating and cooling rates varying from 80 to 180 • C h −1 up to a peak temperature of 1420 • C for various soaking times ranging from 4 to 8 h. All the sintered cordierite honeycombs were characterized with respect to phase composition (XRD), morphology (SEM), bulk density, water absorption, apparent porosity, and CTE (dilatometric studies). XRD studies reveal that all the investigated sintered honeycombs contain >90% cordierite phase with smaller quantities of mullite, spinel and ␣-Al 2 O 3 . Raw materials compositions containing 60% calcined clay of total clay yielded crack free honeycombs with lower thermal anisotropy. Among the various parameters studied, honeycombs sintered with heating rate of 80 • C h −1 , soaking time of 8 h and cooling rate of 180 • C h −1 showed minimum thermal anisotropy.
This paper presents a novel model abstraction and representation approach for the application of ... more This paper presents a novel model abstraction and representation approach for the application of model-based reasoning (MBR) to helicopter powertrain diagnostics. Although the basic principles of MBR are well understood, its application to specific domains, especially in mechanical systems, has been restricted due to insufficient model fidelity. The traditional vibration analysis approach has been the main stay of powertrain diagnosis since accelerometers have proven to be the primary viable choice for gearbox instrumentation and monitoring. However, a suitable logical representation of mechanical components so as to facilitate diagnostic reasoning about their vibration characteristics is difficult to achieve. This paper exploits the physics behind the vibration signatures of gearbox components both in nominal and faulty operational modes, and attempts to extract and represent that knowledge in an MBR-friendly formulation. Based on these model constructs a complete, integrated, MBR methodology for fault diagnosis based on behavioral characteristics of system components is introduced in this paper. Finally, the implementation of this architecture on the intermediate gearbox (IGB) module of a helicopter powertrain is presented. Simulation results show the successful application of this methodology in the detection of input gear pinion damage in the intermediate gearbox of an H-60 helicopter.
Ceramic honeycombs have found diversified applications for thermo-structural implementations main... more Ceramic honeycombs have found diversified applications for thermo-structural implementations mainly due to their unique configuration and outstanding combination of mechanical & thermal properties. However, their potential for energy absorption based ...
The application of the Bayesian theory of managing uncertainty and complexity to regression and c... more The application of the Bayesian theory of managing uncertainty and complexity to regression and classification in the form of Relevance Vector Machine (RVM), and to state estimation via Particle Filters (PF), proves to be a powerful tool to integrate the diagnosis and prognosis of battery health. Accurate estimates of the state-of-charge (SOC), the state-of-health (SOH) and state-oflife (SOL) for batteries provide a significant value addition to the management of any operation involving electrical systems. This is especially true for aerospace systems, where unanticipated battery performance may lead to catastrophic failures.
Uncertainty management has always been the key hurdle faced by diagnostics and prognostics algori... more Uncertainty management has always been the key hurdle faced by diagnostics and prognostics algorithms. A
ABSTRACT Recently implemented Euro norms for pollutants from diesel operated vehicles necessitate... more ABSTRACT Recently implemented Euro norms for pollutants from diesel operated vehicles necessitates the stringent control of carbon monoxide (CO), unburned hydrocarbons (HC), nitrogen oxides (NOx) as well as particulates. Out of the various technological options available for the control of these pollutants, catalytic converter in combination with catalyzed diesel particulate filter is identified as one of the available practical systems to achieve the desired emission limits. However, the successful operation of this system, based on catalyst technology, requires the use of low sulphur content diesel. Hence in India, this technology becomes much complicated due to high sulphur content (0.25—0.3 wt%) diesel in use. This is because reduction in one pollutant can result in the increase of the other especially in the case of particulates. In an effort to provide a practical solution through the catalytic control for a high sulphur containing diesel exhaust, a convertor system consisting of reticulated foam coated with a combustion catalyst in combination with indigenously developed honeycombs with a selective three way catalyst has been developed. The convertor has been evaluated for its performance using high speed, medium duty diesel engine at Automotive Research Association of India, Pune. The convertor has indicated a simultaneous decrease in CO, HC, NOx and particulates as presented in this paper.
Transactions of the Indian Institute of Metals, 2010
... 7. Roy Johnson, Jain Vipin, Kamat SV, Ganesh I, Saha BP and Mahajan YR, Studies on energy Ab... more ... 7. Roy Johnson, Jain Vipin, Kamat SV, Ganesh I, Saha BP and Mahajan YR, Studies on energy Absorption Characteristics of Cordierite-Mullite Honeycombs, Journal of Advanced Materials 35, 3 (2003) 3. 8. Jain Vipin, Roy Johnson, Ganesh I, Saha BP and Mahajan YR, Mater ...
Prognostic performance evaluation has gained significant attention in the past few years. * Curre... more Prognostic performance evaluation has gained significant attention in the past few years. * Currently, prognostics concepts lack standard definitions and suffer from ambiguous and inconsistent interpretations. This lack of standards is in part due to the varied enduser requirements for different applications, time scales, available information, domain dynamics, etc. to name a few. The research community has used a variety of metrics largely based on convenience and their respective requirements. Very little attention has been focused on establishing a standardized approach to compare different efforts. This paper presents several new evaluation metrics tailored for prognostics that were recently introduced and were shown to effectively evaluate various algorithms as compared to other conventional metrics. Specifically, this paper presents a detailed discussion on how these metrics should be interpreted and used. These metrics have the capability of incorporating probabilistic uncertainty estimates from prognostic algorithms. In addition to quantitative assessment they also offer a comprehensive visual perspective that can be used in designing the prognostic system. Several methods are suggested to customize these metrics for different applications. Guidelines are provided to help choose one method over another based on distribution characteristics. Various issues faced by prognostics and its performance evaluation are discussed followed by a formal notational framework to help standardize subsequent developments. * This is an open-access article distributed under the terms of the Creative Commons Attribution 3.0 United States License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Page 1. EVect of fuel type on morphology and reactivity of combustion synthesised MgAl2 O4 powder... more Page 1. EVect of fuel type on morphology and reactivity of combustion synthesised MgAl2 O4 powders I. Ganesh, B. Srinivas, R. Johnson, BP Saha, and YR Mahajan were rst calcined at around 1400°C to obtain an appreci-able ...
Prognostic performance evaluation has gained significant attention in the past few years. * Curre... more Prognostic performance evaluation has gained significant attention in the past few years. * Currently, prognostics concepts lack standard definitions and suffer from ambiguous and inconsistent interpretations. This lack of standards is in part due to the varied enduser requirements for different applications, time scales, available information, domain dynamics, etc. to name a few. The research community has used a variety of metrics largely based on convenience and their respective requirements. Very little attention has been focused on establishing a standardized approach to compare different efforts. This paper presents several new evaluation metrics tailored for prognostics that were recently introduced and were shown to effectively evaluate various algorithms as compared to other conventional metrics. Specifically, this paper presents a detailed discussion on how these metrics should be interpreted and used. These metrics have the capability of incorporating probabilistic uncertainty estimates from prognostic algorithms. In addition to quantitative assessment they also offer a comprehensive visual perspective that can be used in designing the prognostic system. Several methods are suggested to customize these metrics for different applications. Guidelines are provided to help choose one method over another based on distribution characteristics. Various issues faced by prognostics and its performance evaluation are discussed followed by a formal notational framework to help standardize subsequent developments. * This is an open-access article distributed under the terms of the Creative Commons Attribution 3.0 United States License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
The term Automated Contingency Management (ACM) has been used to describe intelligent systems cap... more The term Automated Contingency Management (ACM) has been used to describe intelligent systems capable of mission re-planning and control reconfiguration in the presence of a current health state diagnosis. While a diagnostics driven ACM capability designed to optimize multi-objective performance criteria remains a significant technical challenge, it cannot hope to overcome the fact that it will always be a reactive paradigm. This paper, therefore, introduces an automated contingency management paradigm based on both current heath state (diagnosis) and future health state estimates (prognosis). Including Prognostics in the control loop poses at least two additional challenges to ACM. First, future state prediction will, in general, have uncertainty that increases as the prediction horizon increases so adaptive prognosis routines that manage uncertainty are critical. Secondly, a warning period afforded by prognosis allows ACM to be split into a realtime "reactive" component and a non-real time "planning" component that considers temporal parameters and the potential impact of being proactive with mitigating action. The proactive ACM paradigm was developed and evaluated in the context of a generic mono-propellant system model in Simulink/Stateflow with diagnostics, prognostics and an optimal reconfigurable control system. Applications of Artificial Intelligence (AI) technologies in prognostics enhanced ACM system are briefly discussed. Preliminary results from the on-going research work are presented and the paper is concluded with remarks on future work.
Slip cast Y 2 O 3 stabilized Zirconia (8YSZ) ceramics was subjected to Conventional Ramp and Hold... more Slip cast Y 2 O 3 stabilized Zirconia (8YSZ) ceramics was subjected to Conventional Ramp and Hold (CRH), Rate Controlled (RCS) and Two Stage Sintering (2SS) methodologies. Sintered samples were characterized for their densities and grain size analysis by Scanning Electron Microscopy. The slip cast samples sintered by CRH and 2SS have achieved 98 -99 % of theoretical densities while RCS samples have exhibited a low density of 97 %. The samples exhibited an average grain size of 2.64 µm by 2SS sintering in comparison to 8.83 µm in case of CRH and 3.45 µm in case of RCS. Controlled pore growth associated with RCS, when compared to CRH methodology is mainly responsible for the relatively smaller grain size observed with RCS. A four fold decrease in grain size i.e. 2.64 µm observed with the two step sintering can be attributed to the fact that the first heating step to high temperature of 1550°C for a shorter duration closes the porosity without significant grain growth. The second step at 1375°C for a longer period of time imparts densification with limited grain growth.
Cordierite honeycombs with oxide compositions of 49.5-51 wt.% SiO 2 , 35.5-36 wt.% Al 2 O 3 and 1... more Cordierite honeycombs with oxide compositions of 49.5-51 wt.% SiO 2 , 35.5-36 wt.% Al 2 O 3 and 14-14.5 wt.% MgO were prepared from clay, talc, and alumina using conventional extrusion process. Effects of sintering parameters such as heating rate, soaking time, cooling rate as well as amount of calcined clay in the raw material compositions on the overall coefficient of thermal expansion (CTE) as well as thermal anisotropy in terms of CTE difference between the extrusion direction and across the extrusion direction of the cordierite honeycombs were studied. For this purpose, extruded honeycombs were sintered with various heating and cooling rates varying from 80 to 180 • C h −1 up to a peak temperature of 1420 • C for various soaking times ranging from 4 to 8 h. All the sintered cordierite honeycombs were characterized with respect to phase composition (XRD), morphology (SEM), bulk density, water absorption, apparent porosity, and CTE (dilatometric studies). XRD studies reveal that all the investigated sintered honeycombs contain >90% cordierite phase with smaller quantities of mullite, spinel and ␣-Al 2 O 3 . Raw materials compositions containing 60% calcined clay of total clay yielded crack free honeycombs with lower thermal anisotropy. Among the various parameters studied, honeycombs sintered with heating rate of 80 • C h −1 , soaking time of 8 h and cooling rate of 180 • C h −1 showed minimum thermal anisotropy.
This paper presents a novel model abstraction and representation approach for the application of ... more This paper presents a novel model abstraction and representation approach for the application of model-based reasoning (MBR) to helicopter powertrain diagnostics. Although the basic principles of MBR are well understood, its application to specific domains, especially in mechanical systems, has been restricted due to insufficient model fidelity. The traditional vibration analysis approach has been the main stay of powertrain diagnosis since accelerometers have proven to be the primary viable choice for gearbox instrumentation and monitoring. However, a suitable logical representation of mechanical components so as to facilitate diagnostic reasoning about their vibration characteristics is difficult to achieve. This paper exploits the physics behind the vibration signatures of gearbox components both in nominal and faulty operational modes, and attempts to extract and represent that knowledge in an MBR-friendly formulation. Based on these model constructs a complete, integrated, MBR methodology for fault diagnosis based on behavioral characteristics of system components is introduced in this paper. Finally, the implementation of this architecture on the intermediate gearbox (IGB) module of a helicopter powertrain is presented. Simulation results show the successful application of this methodology in the detection of input gear pinion damage in the intermediate gearbox of an H-60 helicopter.
Ceramic honeycombs have found diversified applications for thermo-structural implementations main... more Ceramic honeycombs have found diversified applications for thermo-structural implementations mainly due to their unique configuration and outstanding combination of mechanical & thermal properties. However, their potential for energy absorption based ...
The application of the Bayesian theory of managing uncertainty and complexity to regression and c... more The application of the Bayesian theory of managing uncertainty and complexity to regression and classification in the form of Relevance Vector Machine (RVM), and to state estimation via Particle Filters (PF), proves to be a powerful tool to integrate the diagnosis and prognosis of battery health. Accurate estimates of the state-of-charge (SOC), the state-of-health (SOH) and state-oflife (SOL) for batteries provide a significant value addition to the management of any operation involving electrical systems. This is especially true for aerospace systems, where unanticipated battery performance may lead to catastrophic failures.
Uncertainty management has always been the key hurdle faced by diagnostics and prognostics algori... more Uncertainty management has always been the key hurdle faced by diagnostics and prognostics algorithms. A
ABSTRACT Recently implemented Euro norms for pollutants from diesel operated vehicles necessitate... more ABSTRACT Recently implemented Euro norms for pollutants from diesel operated vehicles necessitates the stringent control of carbon monoxide (CO), unburned hydrocarbons (HC), nitrogen oxides (NOx) as well as particulates. Out of the various technological options available for the control of these pollutants, catalytic converter in combination with catalyzed diesel particulate filter is identified as one of the available practical systems to achieve the desired emission limits. However, the successful operation of this system, based on catalyst technology, requires the use of low sulphur content diesel. Hence in India, this technology becomes much complicated due to high sulphur content (0.25—0.3 wt%) diesel in use. This is because reduction in one pollutant can result in the increase of the other especially in the case of particulates. In an effort to provide a practical solution through the catalytic control for a high sulphur containing diesel exhaust, a convertor system consisting of reticulated foam coated with a combustion catalyst in combination with indigenously developed honeycombs with a selective three way catalyst has been developed. The convertor has been evaluated for its performance using high speed, medium duty diesel engine at Automotive Research Association of India, Pune. The convertor has indicated a simultaneous decrease in CO, HC, NOx and particulates as presented in this paper.
Transactions of the Indian Institute of Metals, 2010
... 7. Roy Johnson, Jain Vipin, Kamat SV, Ganesh I, Saha BP and Mahajan YR, Studies on energy Ab... more ... 7. Roy Johnson, Jain Vipin, Kamat SV, Ganesh I, Saha BP and Mahajan YR, Studies on energy Absorption Characteristics of Cordierite-Mullite Honeycombs, Journal of Advanced Materials 35, 3 (2003) 3. 8. Jain Vipin, Roy Johnson, Ganesh I, Saha BP and Mahajan YR, Mater ...
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