Romesh Nagarajah - Academia.edu (original) (raw)

Papers by Romesh Nagarajah

Ultrasonic Sensing Technology

Ultrasonic Fluid Quantity Measurement in Dynamic Vehicular Applications, 2013

Ultrasonic inspection of surface roughness aluminium die castings

ABSTRACT

Development and Application of a Wireless Insole Device for the Measurement of Human Gait Kinematics

ABSTRACT

Non-destructive testing using ultrasonic measurement is used to ensure the quality of the die-cas... more Non-destructive testing using ultrasonic measurement is used to ensure the quality of the die-casting products. The quality of a casting depends on the presence of discontinuities such as porosity and on the final metallurgical structure. Discontinuities occurring in the sub-surface of the cast structure mostly have irregular surfaces which scatter the ultrasound waves and make ultrasonic testing more difficult. The effective use of ultrasonic testing for inspection of castings depends greatly upon the skills and expertise of the operator. However, the initial experimental set-up is important to develop a proper inspection procedure that is easily understood by the operators. The aim of the present work is to investigate and develop an automated ultrasonic inspection system for detecting sub-surface defects in aluminium die-casting parts. Two sample test cases were selected from the industrial partners. Ultrasonic immersion testing was carried out on the sample parts using different probes situated at different water path distances to obtain the best possible signal from the defect. The results obtained from the experiments have demonstrated the feasibility of developing an online automatic inspection system to detect sub-surface defects in aluminium die-casting components.

Measurement Technology and Intelligent Instruments, 1993

ABSTRACT The purpose of this paper is to identify the most promising methodology for an applicati... more ABSTRACT The purpose of this paper is to identify the most promising methodology for an application involving real time component inspection. The components which are of a thick high density nature are to be inspected for internal defects such as cracks, cavities and voids. The alternative methodologies to be evaluated include x-radiology, ultrasonic testing and neutron radiology. The authors of this paper contend that, due to the lengthy exposure times and the high cost of suitable generators, neutron techniques are incapable of satisfying the real time component of this application. Although ultrasonic techniques are very sensitive to the presence of defects, it is much more difficult to accurately and reliably determine their size. The authors have found that in light of the highly sensitive nature of ultrasound, it maybe suitable for the application. The paper also examines x-radiological methods in terms of hardware limitations and techniques used to overcome these problems. In terms of detecting and evaluating in real time, the extent of defects within thick high density components, the most suitable techniques have been evaluated.

Automated ultrasonic classification of defects in aluminium die castings

Effects of grain size and surface roughness on ultrasonic inspection of aluminium alloy die castings

A study on ultrasonic flaw detection of aluminium die castings

ROBUST ADAPTIVE FUZZY SYSTEMS FOR INTEGRATED LATERAL AND LONGITUDINAL CONTROL OF HIGHWAY VEHICLES

Control and Intelligent Systems, 2014

ABSTRACT

Simulation scan comparison for process monitoring using 3D scanning in manufacturing environments

The International Journal of Advanced Manufacturing Technology, 2014

ABSTRACT In order for robotics to be used in automated production facilities, the manufacturing s... more ABSTRACT In order for robotics to be used in automated production facilities, the manufacturing systems must be highly constrained. Despite the efforts of designers to generate accurate simulations, differences often occur in the real implementation. These differences are especially common in flexible manufacturing where people are required to operate in the same space as automated machines. Objects located in unexpected positions or orientations, additional objects in the area or missing objects can cause a robot to perform the designated operations incorrectly leading to wastage and loss of production. Typically, robotic systems have no information about the real environment around it and operate blind. In order to provide more information to the robot about its environment, information such as 3D scans can be provided to the system. This research compares a 3D scan of what is present in the environment to a 3D simulation of what is expected in the environment. The simulation scan comparison (SSC) process detects missing, unknown and incorrectly located objects. The results from the comparison process can be used to make decisions about how operations should be performed so that the outcome is satisfactory. For example, if an unknown object is in the path of a robot, the robot can be rerouted around the object. The surfaces of both simulation objects and 3D scan data are described using triangles, allowing triangle neighbour data to be used for more efficient identification of unknown objects, and triangle normal data to detect missing objects. In addition, occupancy grids have been employed for both the path planning and surface-matching processes further increasing the computational efficiency of the system. The SSC process was used to detect missing, unknown and incorrectly located objects in a typical robot cell to an accuracy of 98 %, thus demonstrating that the SSC process is capable of identifying unknown objects or unexpected situations and using these detections to update the original simulation or alter the manufacturing process.

A novel fuzzy PDC paradigm with multiple-adaptive fuzzy control for highway vehicles

2013 IEEE 8th Conference on Industrial Electronics and Applications (ICIEA), 2013

ABSTRACT A novel approach using multiple-adaptive fuzzy systems in a fuzzy PDC (Parallel Distribu... more ABSTRACT A novel approach using multiple-adaptive fuzzy systems in a fuzzy PDC (Parallel Distributed Compensation) based structure for integrated lateral and longitudinal control of highway vehicles for improved transient response, is presented in this paper. For comparison studies a single-adaptive fuzzy controller synthesis is also presented. These fuzzy setups are used separately for robust compensation for un-modeled dynamics, nonlinearity issues, external disturbances and uncertainties. A simulation study with veDYNA®, an industry-standard simulation package is used for validating the developed control models in the presence of robust conditions and non-catastrophic failure cases of vehicle subsystem components.

Fluid level measurement in dynamic environments using a single ultrasonic sensor and Support Vector Machine (SVM)

Sensors and Actuators A: Physical, 2010

... Signal enhancement 3. Experimental setup 4. Validation results 5. Conclusion 6. Future work .... more ... Signal enhancement 3. Experimental setup 4. Validation results 5. Conclusion 6. Future work ... of fluid contained in the tank [9]. Theoretical studies and numerical analysis have been ... The fluid measurement systems described by Kobayashi and Kita [17] employ a vehicle speed ...

Understanding Drivers for environmental practices in SMEs: A critical review

2010 IEEE International Conference on Management of Innovation & Technology, 2010

ABSTRACT The interest on environmental management has been increased significantly and now is oft... more ABSTRACT The interest on environmental management has been increased significantly and now is often considered to be a mainstream challenge for organizations. Small and Medium Enterprises (SMEs) in part can be of particular significance as their total impact towards environmental degradation is huge. Yet this sector still has not incorporated the concept of environmental sustainability into their strategic planning. The aim of this study is to explore (i) SMEs environmental initiatives and (ii) Drivers for environmental initiatives.

A novel multiple adaptive fuzzy system for robust nonlinear control

IECON 2011 - 37th Annual Conference of the IEEE Industrial Electronics Society, 2011

ABSTRACT A novel approach using multiple adaptive fuzzy systems for controlling complex nonlinear... more ABSTRACT A novel approach using multiple adaptive fuzzy systems for controlling complex nonlinear systems for improved transient response, is developed in this study. The multiple adaptive fuzzy controllers are soft-switched depending on the operating conditions using another fuzzy-based function. Apart from that, a single adaptive fuzzy controller is also developed for comparison studies. These fuzzy setups are used separately in pursuit of robust compensation for the unmodeled dynamics, nonlinearity issues, external disturbances and model uncertainties etc., thus ensuring a globally asymptotically stable system. A Lyapunov-based Kalman-Yakubovich-Popov (KYP) lemma is used to ensure closed loop robust stability of the control systems with the establishment of positive-realness of the error system. A simulation study using a passenger car model, an example of complex nonlinear system, is carried out. The results obtained from these simulation studies demonstrate that the multiple adaptive controller setup results in substantial improvements over the single adaptive system especially in the transient effects with the performance of complex systems.

Advanced Materials Research, 2011

Comparison between different sets of suspension parameters and introduction of new modified skyhook control strategy incorporating varying road condition

Vehicle System Dynamics, 2012

This study examines the uncertainties in modelling a quarter car suspension system caused by the ... more This study examines the uncertainties in modelling a quarter car suspension system caused by the effect of different sets of suspension parameters of a corresponding mathematical model. To overcome this problem, 11 sets of identified parameters of a suspension system have been compared, taken from the most recent published work. From this investigation, a set of parameters were chosen which showed a better performance than others in respect of peak amplitude and settling time. These chosen parameters were then used to investigate the performance of a new modified continuous skyhook control strategy with adaptive gain that dictates the vehicle's semi-active suspension system. The proposed system first captures the road profile input over a certain period. Then it calculates the best possible value of the skyhook gain (SG) for the subsequent process. Meanwhile the system is controlled according to the new modified skyhook control law using an initial or previous value of the SG. In this study, the proposed suspension system is compared with passive and other recently reported skyhook controlled semi-active suspension systems. Its performances have been evaluated in terms of ride comfort and road handling performance. The model has been validated in accordance with the international standards of admissible acceleration levels ISO2631 and human vibration perception.

Predicting ground reaction forces in running using micro-sensors and neural networks

Sports Engineering, 2006

Measurement of ground reaction force (GRF) in running provides a direct indication of the loads t... more Measurement of ground reaction force (GRF) in running provides a direct indication of the loads to which the body is subjected at each foot-ground contact, and can provide an objective explanation for performance outcomes. Traditionally, the collection of three orthogonal component GRF data in running requires an athlete to complete a series of return loops along a laboratory based runway,

Analysis of structured highlight stereo imaging for shape measurement of specular objects

Optical Engineering, 2007

ABSTRACT Structured highlight stereo (SHS) is a technique for the measurement of specular objects... more ABSTRACT Structured highlight stereo (SHS) is a technique for the measurement of specular objects, and is based on viewing the reflection of a structured highlight pattern from multiple directions. This paper reports the results of a simulation and experimental analysis of the approach in order to further understand the accuracy and limitations of SHS. In particular, this paper describes two important findings related to this technique. Firstly, it is shown that the search region containing a consistent set of candidate highlights may be minimized using epipolar constraints. Secondly, an analysis is presented to quantify the accuracy of the SHS approach for different surface curvatures. The results indicate that, although it is possible to accurately measure the surface height of planar specular objects, the accuracy is reduced for objects with curved surface profiles. The measurement error occurs because in general it is not possible to measure the same surface location with both cameras, which then leads to an inconsistency between the surface normal estimates for each camera. The measurement error increases in relation to both the distance between measurement locations on the surface and the surface curvature. (c) 2007 Society of Photo-Optical Instrumentation Engineers.

Neuroscience, 2010

The chakragati (ckr) mouse has been proposed as a model of aspects of schizophrenia. The mice, cr... more The chakragati (ckr) mouse has been proposed as a model of aspects of schizophrenia. The mice, created serendipitously as a result of a transgenic insertional mutation, exhibit spontaneous circling, hyperactivity, hypertone of the dopamine system, reduced social interactions, enlarged lateral ventricles, deficits in pre-pulse inhibition of acoustic startle and deficits in latent inhibition of conditioned learning. In this study, the dosedependent effects of antipsychotic drugs (haloperidol, pimozide, risperidone, clozapine, olanzapine, ziprasidone, quetiapine and aripiprazole) on the spontaneous hyperactivity of the mice were investigated. All the antipsychotic drugs tested dosedependently suppressed spontaneous hyperactivity. Aripriprazole, which is known to be a dopamine D2 receptor partial agonist, exhibited a tri-phasic dose-response, initially suppressing hyperactivity at low doses, having little effect on hyperactivity at intermediate doses, and suppressing activity again at high doses. These data suggest that the spontaneous circling and hyperactivity of the ckr mouse may allow screening of candidate antipsychotic compounds, distinguishing compounds with aripriprazole-like profiles.

A Technique For The Prediction Of Continuous Three Orthogonal Component Ground Reaction Force Records In Running

Medicine & Science in Sports & Exercise, 2007

Ultrasonic Sensing Technology

Ultrasonic Fluid Quantity Measurement in Dynamic Vehicular Applications, 2013

Ultrasonic inspection of surface roughness aluminium die castings

ABSTRACT

Development and Application of a Wireless Insole Device for the Measurement of Human Gait Kinematics

ABSTRACT

Non-destructive testing using ultrasonic measurement is used to ensure the quality of the die-cas... more Non-destructive testing using ultrasonic measurement is used to ensure the quality of the die-casting products. The quality of a casting depends on the presence of discontinuities such as porosity and on the final metallurgical structure. Discontinuities occurring in the sub-surface of the cast structure mostly have irregular surfaces which scatter the ultrasound waves and make ultrasonic testing more difficult. The effective use of ultrasonic testing for inspection of castings depends greatly upon the skills and expertise of the operator. However, the initial experimental set-up is important to develop a proper inspection procedure that is easily understood by the operators. The aim of the present work is to investigate and develop an automated ultrasonic inspection system for detecting sub-surface defects in aluminium die-casting parts. Two sample test cases were selected from the industrial partners. Ultrasonic immersion testing was carried out on the sample parts using different probes situated at different water path distances to obtain the best possible signal from the defect. The results obtained from the experiments have demonstrated the feasibility of developing an online automatic inspection system to detect sub-surface defects in aluminium die-casting components.

Measurement Technology and Intelligent Instruments, 1993

ABSTRACT The purpose of this paper is to identify the most promising methodology for an applicati... more ABSTRACT The purpose of this paper is to identify the most promising methodology for an application involving real time component inspection. The components which are of a thick high density nature are to be inspected for internal defects such as cracks, cavities and voids. The alternative methodologies to be evaluated include x-radiology, ultrasonic testing and neutron radiology. The authors of this paper contend that, due to the lengthy exposure times and the high cost of suitable generators, neutron techniques are incapable of satisfying the real time component of this application. Although ultrasonic techniques are very sensitive to the presence of defects, it is much more difficult to accurately and reliably determine their size. The authors have found that in light of the highly sensitive nature of ultrasound, it maybe suitable for the application. The paper also examines x-radiological methods in terms of hardware limitations and techniques used to overcome these problems. In terms of detecting and evaluating in real time, the extent of defects within thick high density components, the most suitable techniques have been evaluated.

Automated ultrasonic classification of defects in aluminium die castings

Effects of grain size and surface roughness on ultrasonic inspection of aluminium alloy die castings

A study on ultrasonic flaw detection of aluminium die castings

ROBUST ADAPTIVE FUZZY SYSTEMS FOR INTEGRATED LATERAL AND LONGITUDINAL CONTROL OF HIGHWAY VEHICLES

Control and Intelligent Systems, 2014

ABSTRACT

Simulation scan comparison for process monitoring using 3D scanning in manufacturing environments

The International Journal of Advanced Manufacturing Technology, 2014

ABSTRACT In order for robotics to be used in automated production facilities, the manufacturing s... more ABSTRACT In order for robotics to be used in automated production facilities, the manufacturing systems must be highly constrained. Despite the efforts of designers to generate accurate simulations, differences often occur in the real implementation. These differences are especially common in flexible manufacturing where people are required to operate in the same space as automated machines. Objects located in unexpected positions or orientations, additional objects in the area or missing objects can cause a robot to perform the designated operations incorrectly leading to wastage and loss of production. Typically, robotic systems have no information about the real environment around it and operate blind. In order to provide more information to the robot about its environment, information such as 3D scans can be provided to the system. This research compares a 3D scan of what is present in the environment to a 3D simulation of what is expected in the environment. The simulation scan comparison (SSC) process detects missing, unknown and incorrectly located objects. The results from the comparison process can be used to make decisions about how operations should be performed so that the outcome is satisfactory. For example, if an unknown object is in the path of a robot, the robot can be rerouted around the object. The surfaces of both simulation objects and 3D scan data are described using triangles, allowing triangle neighbour data to be used for more efficient identification of unknown objects, and triangle normal data to detect missing objects. In addition, occupancy grids have been employed for both the path planning and surface-matching processes further increasing the computational efficiency of the system. The SSC process was used to detect missing, unknown and incorrectly located objects in a typical robot cell to an accuracy of 98 %, thus demonstrating that the SSC process is capable of identifying unknown objects or unexpected situations and using these detections to update the original simulation or alter the manufacturing process.

A novel fuzzy PDC paradigm with multiple-adaptive fuzzy control for highway vehicles

2013 IEEE 8th Conference on Industrial Electronics and Applications (ICIEA), 2013

ABSTRACT A novel approach using multiple-adaptive fuzzy systems in a fuzzy PDC (Parallel Distribu... more ABSTRACT A novel approach using multiple-adaptive fuzzy systems in a fuzzy PDC (Parallel Distributed Compensation) based structure for integrated lateral and longitudinal control of highway vehicles for improved transient response, is presented in this paper. For comparison studies a single-adaptive fuzzy controller synthesis is also presented. These fuzzy setups are used separately for robust compensation for un-modeled dynamics, nonlinearity issues, external disturbances and uncertainties. A simulation study with veDYNA®, an industry-standard simulation package is used for validating the developed control models in the presence of robust conditions and non-catastrophic failure cases of vehicle subsystem components.

Fluid level measurement in dynamic environments using a single ultrasonic sensor and Support Vector Machine (SVM)

Sensors and Actuators A: Physical, 2010

... Signal enhancement 3. Experimental setup 4. Validation results 5. Conclusion 6. Future work .... more ... Signal enhancement 3. Experimental setup 4. Validation results 5. Conclusion 6. Future work ... of fluid contained in the tank [9]. Theoretical studies and numerical analysis have been ... The fluid measurement systems described by Kobayashi and Kita [17] employ a vehicle speed ...

Understanding Drivers for environmental practices in SMEs: A critical review

2010 IEEE International Conference on Management of Innovation & Technology, 2010

ABSTRACT The interest on environmental management has been increased significantly and now is oft... more ABSTRACT The interest on environmental management has been increased significantly and now is often considered to be a mainstream challenge for organizations. Small and Medium Enterprises (SMEs) in part can be of particular significance as their total impact towards environmental degradation is huge. Yet this sector still has not incorporated the concept of environmental sustainability into their strategic planning. The aim of this study is to explore (i) SMEs environmental initiatives and (ii) Drivers for environmental initiatives.

A novel multiple adaptive fuzzy system for robust nonlinear control

IECON 2011 - 37th Annual Conference of the IEEE Industrial Electronics Society, 2011

ABSTRACT A novel approach using multiple adaptive fuzzy systems for controlling complex nonlinear... more ABSTRACT A novel approach using multiple adaptive fuzzy systems for controlling complex nonlinear systems for improved transient response, is developed in this study. The multiple adaptive fuzzy controllers are soft-switched depending on the operating conditions using another fuzzy-based function. Apart from that, a single adaptive fuzzy controller is also developed for comparison studies. These fuzzy setups are used separately in pursuit of robust compensation for the unmodeled dynamics, nonlinearity issues, external disturbances and model uncertainties etc., thus ensuring a globally asymptotically stable system. A Lyapunov-based Kalman-Yakubovich-Popov (KYP) lemma is used to ensure closed loop robust stability of the control systems with the establishment of positive-realness of the error system. A simulation study using a passenger car model, an example of complex nonlinear system, is carried out. The results obtained from these simulation studies demonstrate that the multiple adaptive controller setup results in substantial improvements over the single adaptive system especially in the transient effects with the performance of complex systems.

Advanced Materials Research, 2011

Comparison between different sets of suspension parameters and introduction of new modified skyhook control strategy incorporating varying road condition

Vehicle System Dynamics, 2012

This study examines the uncertainties in modelling a quarter car suspension system caused by the ... more This study examines the uncertainties in modelling a quarter car suspension system caused by the effect of different sets of suspension parameters of a corresponding mathematical model. To overcome this problem, 11 sets of identified parameters of a suspension system have been compared, taken from the most recent published work. From this investigation, a set of parameters were chosen which showed a better performance than others in respect of peak amplitude and settling time. These chosen parameters were then used to investigate the performance of a new modified continuous skyhook control strategy with adaptive gain that dictates the vehicle's semi-active suspension system. The proposed system first captures the road profile input over a certain period. Then it calculates the best possible value of the skyhook gain (SG) for the subsequent process. Meanwhile the system is controlled according to the new modified skyhook control law using an initial or previous value of the SG. In this study, the proposed suspension system is compared with passive and other recently reported skyhook controlled semi-active suspension systems. Its performances have been evaluated in terms of ride comfort and road handling performance. The model has been validated in accordance with the international standards of admissible acceleration levels ISO2631 and human vibration perception.

Predicting ground reaction forces in running using micro-sensors and neural networks

Sports Engineering, 2006

Measurement of ground reaction force (GRF) in running provides a direct indication of the loads t... more Measurement of ground reaction force (GRF) in running provides a direct indication of the loads to which the body is subjected at each foot-ground contact, and can provide an objective explanation for performance outcomes. Traditionally, the collection of three orthogonal component GRF data in running requires an athlete to complete a series of return loops along a laboratory based runway,

Analysis of structured highlight stereo imaging for shape measurement of specular objects

Optical Engineering, 2007

ABSTRACT Structured highlight stereo (SHS) is a technique for the measurement of specular objects... more ABSTRACT Structured highlight stereo (SHS) is a technique for the measurement of specular objects, and is based on viewing the reflection of a structured highlight pattern from multiple directions. This paper reports the results of a simulation and experimental analysis of the approach in order to further understand the accuracy and limitations of SHS. In particular, this paper describes two important findings related to this technique. Firstly, it is shown that the search region containing a consistent set of candidate highlights may be minimized using epipolar constraints. Secondly, an analysis is presented to quantify the accuracy of the SHS approach for different surface curvatures. The results indicate that, although it is possible to accurately measure the surface height of planar specular objects, the accuracy is reduced for objects with curved surface profiles. The measurement error occurs because in general it is not possible to measure the same surface location with both cameras, which then leads to an inconsistency between the surface normal estimates for each camera. The measurement error increases in relation to both the distance between measurement locations on the surface and the surface curvature. (c) 2007 Society of Photo-Optical Instrumentation Engineers.

Neuroscience, 2010

The chakragati (ckr) mouse has been proposed as a model of aspects of schizophrenia. The mice, cr... more The chakragati (ckr) mouse has been proposed as a model of aspects of schizophrenia. The mice, created serendipitously as a result of a transgenic insertional mutation, exhibit spontaneous circling, hyperactivity, hypertone of the dopamine system, reduced social interactions, enlarged lateral ventricles, deficits in pre-pulse inhibition of acoustic startle and deficits in latent inhibition of conditioned learning. In this study, the dosedependent effects of antipsychotic drugs (haloperidol, pimozide, risperidone, clozapine, olanzapine, ziprasidone, quetiapine and aripiprazole) on the spontaneous hyperactivity of the mice were investigated. All the antipsychotic drugs tested dosedependently suppressed spontaneous hyperactivity. Aripriprazole, which is known to be a dopamine D2 receptor partial agonist, exhibited a tri-phasic dose-response, initially suppressing hyperactivity at low doses, having little effect on hyperactivity at intermediate doses, and suppressing activity again at high doses. These data suggest that the spontaneous circling and hyperactivity of the ckr mouse may allow screening of candidate antipsychotic compounds, distinguishing compounds with aripriprazole-like profiles.

A Technique For The Prediction Of Continuous Three Orthogonal Component Ground Reaction Force Records In Running

Medicine & Science in Sports & Exercise, 2007