In this work, a general concept of the human-exoskeleton compatibility and interaction control is... more In this work, a general concept of the human-exoskeleton compatibility and interaction control is addressed. Rehabilitation, as applied to humans with motor control disorder, involves repetitive gait training in relation to lower limb extremity and repetitive task training in relation to upper limb extremity. It is in this regard that exoskeletal systems must be kinematically compatible with those of the subject in order to guarantee that the subject is being trained properly. The incompatibility between the wearable robotic device and the wearer results in joint misalignment, thus introducing interaction forces during movement. This, therefore, leads to the introduction of the need for interaction control in wearable robotic devices. Human-exoskeleton joint alignment is an uphill task; hence, measures to actualize this in order to guarantee the safety and comfort of humans are necessary. These measures depend on the types of joints involved in the rehabilitation or assistive proces...
A bounded control strategy is employed for the rehabilitation and assistance of a patient with lo... more A bounded control strategy is employed for the rehabilitation and assistance of a patient with lower-limb disorder. Complete and partial lower-limb motor function disorders are considered. This application is centered on the knee and the ankle joint level, thereby considering a user in a sitting position. A high gain observer is used in the estimation of the angular position and angular velocities which is then applied to the estimation of the joint torques. The level of human contribution is feedback of a fraction of the estimated joint torque. This is utilised in order to meet the demands for a bounded human torque; that is, τh≤N2,n≤N1,n. The asymptotic stability of the bounded control law without human contribution and the convergence analysis of the high gain observer is verified using Lyapunov-based analysis. Simulations are performed to verify the proposed control law. Results obtained guarantee a fair trajectory tracking of the physiotherapist trajectory.
2014 IEEE-RAS International Conference on Humanoid Robots, 2014
Faculty of Engineering and the Built Environment Department of …ELECTRICAL ENGINEERING / FSATI 2 ... more Faculty of Engineering and the Built Environment Department of …ELECTRICAL ENGINEERING / FSATI 2 AIMS & APPROACH • Aims: q To provide assistance and rehabilitative measures to humans with lower limb disorders. q Investigate a rehabilitation protocol method using CPGs. • Approach: q Inverse dynamics approach via adaptive coupled oscillators also known as CPGs. Faculty of Engineering and the Built Environment Department of …ELECTRICAL ENGINEERING / FSATI 3 Faculty of Engineering and the Built Environment Department of …ELECTRICAL ENGINEERING / FSATI 4 Faculty of Engineering and the Built Environment Department of …ELECTRICAL ENGINEERING / FSATI
Brain Computer Interfaces (BCI) rely on brain waves signal, such as electro-encephalogram (EEG) r... more Brain Computer Interfaces (BCI) rely on brain waves signal, such as electro-encephalogram (EEG) recording, to endow a disabled user with non-muscular communication. Given the very low signal-to-noise ratio of EEG, a signal enhancement phase is crucial for ensuring decent performances in BCI systems. Several methods have been proposed for EEG signal enhancement, such as Independent Component Analysis, Common Spatial Pattern, and Principal Component Analysis. We show that Canonical Correlation Analysis (CCA), initially introduced to SSVEP-based BCI as a feature extraction method, is a good candidate for such preprocessing state. Evaluation is performed on a recording from 5 subjects during a BCI task based on Steady-State Visual Evoked Potentials (SSVEP). We demonstrate that CCA significantly improves classification performances in SSVEP-based BCIs.
760: 761: 762: 763: The IASTED 2012 African Conferences, 2012
Research on wheelchairs is on its growing phase and assistive aids brought to wheelchair users in... more Research on wheelchairs is on its growing phase and assistive aids brought to wheelchair users in terms of adaptability to electric wheelchair have not yet been perfected. This paper presents the development of a User-Wheelchair-Environment (UWE) system in order to ease driving evaluation of wheelchair user. The system is modelled using Matlab/Simulink and it provides useful information such as linear and angular velocity and displacement in a 3D-virtual environment. The model consists of three main components (user interface, wheelchair model and virtual environment) which are individually modelled and later integrated altogether to form the UWE system. Simulation results are also presented.
This paper introduces a new methodology to assist teaching and learning in a time-constrained env... more This paper introduces a new methodology to assist teaching and learning in a time-constrained environment at the hand of two time-on-task examples. These examples are from the field of Electrical Engineering studies with a focus on firstyear studies and an advanced software design course taught at the Tshwane University of Technology in South Africa. In an endeavour to understand the timing model of the human brain to master and assimilate new information, a study was conducted to determine some of the parameters that could possibly have an influence on the timing model and how the brain perceives new information. From this study the Rope-Weaver's Principles were derived and are built on three well-known theories, comparative judgment, the Guttman scale and the learning curve, integrated into the new methodology. The Rope-Weaver's Principles are presented as an abstraction of the mathematical principles and the measures that underpin this study. The research was done from a participant-observer perspective with design research as central methodology. The research methodology involved a longitudinal study employing mixed-methods research. The results led to the observation of a toe or plateau in the infancy of the learning curve. The observed plateau has a direct influence on the order and time frame of the introduction of new study material in a formal educational programme. The results were found to adhere to the Weber-Fechner Law. This relates to other studies on animals, suggesting that the way the brain perceives stimuli or assimilate knowledge is hard-wired throughout the animal kingdom although the brain structures vary widely. It is proposed that Rope-Weaver's Principles, complementary to the current pool of teaching and learning theories, lead to a better mastery of the learning material or skills, moving persons under instruction from rule based training-behaviourism, to maxim integration-constructivism.
Leakage detection and localization in pipelines has become an important aspect of water managemen... more Leakage detection and localization in pipelines has become an important aspect of water management systems. Since monitoring leakage in large-scale water distribution networks (WDNs) is a challenging task, the need to develop a reliable and robust leak detection and localization technique is essential for loss reduction in potable WDNs. In this paper, some of the existing techniques for water leakage detection are discussed and open research areas and challenges are highlighted. It is concluded that despite the numerous research efforts and advancement in leakage detection technologies, a large scope is still open for further research in this domain. One such area is the effective detection of background type leakages that have not been covered fully in the literature. The utilization of wireless sensor networks for leakage detection purposes, its technical challenges as well as some future research areas are also presented. In a general remark, practical application of these techniques for large-scale water distribution networks is still a major concern. In this paper, an overview of this important problem is addressed.
Multi-Radio Multi-Channel (MRMC) systems are key to power control problems in WMNs. Previous stud... more Multi-Radio Multi-Channel (MRMC) systems are key to power control problems in WMNs. Previous studies have emphasized throughput maximization in such systems as the main design challenge and transmission power control treated as a secondary issue. In this paper, we present an autonomous power adaptation for MRMC WMNs. The transmit power is dynamically adapted by each network interface card (NIC) in response to the locally available energy in a node, queue load, and interference states of a channel. To achieve this, WMN is first represented as a set of Unified Channel Graphs (UCGs). Second, each NIC of a node is tuned to a UCG. Third, a power selection MRMC unification protocol (PMMUP) that coordinates Interaction variables (IV) from different UCGs and Unification variables (UV) from higher layers is proposed. PMMUP coordinates autonomous power optimization by the NICs of a node. The efficacy of the proposed method is investigated through simulations.
This paper describes a visual interface that recognizes the command request of a person by inferr... more This paper describes a visual interface that recognizes the command request of a person by inferring the intention to travel in a desired direction at a certain speed from the person’s head movements. A rotation and a vertical motion indicate the intent to change direction and speed respectively. The context for which this solution is intended is that of wheelchair
Simulation, Modeling, and Programming for Autonomous Robots, 2014
In this paper, an inverse dynamics approach by means of adaptive coupled oscillators is used in t... more In this paper, an inverse dynamics approach by means of adaptive coupled oscillators is used in the modelling and control of a lower limb orthosis applied at the knee and ankle joint level. This design is aimed at providing assistance and rehabilitative measures to humans with lower limb disorders and as such presents a platform for which their mobility performance can be improved. Adaptive oscillators are known to have the capability of learning high level parameters of sinusoidal, quasi-sinusoidal or non-sinusoidal signals (amplitude, frequency and offset). However, the later signal (non-sinusoidal) considered in this paper requires a number of oscillators in parallel to replicate the moving joint regarding filtering via adaptive oscillator. The dynamic model for the knee and ankle are considered to take the form of a damped pendulum model connected by two revolute joints. This maps the input torque of both joints (knee and ankle) to their output trajectories, hence integrating the different forces at the joint level of the different joints. The coupling effect is achieved by the use of coupled Adaptive Frequency Oscillator (AFO) for the estimation of the joint trajectories. Tracking performance for the knee-ankle orthosis is studied for non-sinusoidal reference trajectories, having a global coupling between the joints. The results obtained using SCILAB show a good performance of the controller trajectory tracking capabilities even in the presence of external disturbances.
2012 Sixth IEEE/PES Transmission and Distribution: Latin America Conference and Exposition (T&D-LA), 2012
ABSTRACT This paper seeks to identify and classify power system networks based on their inherent ... more ABSTRACT This paper seeks to identify and classify power system networks based on their inherent definitive structural property. The participation between the load buses is observable from the eigenvectors obtained from a Schur complement of the Y-admittance matrix. This is used to classify power system networks as either topologically strong or weak. Results show that in a topologically weak network, load voltages are below the nominal voltage limit. Conversely, in a topologically strong network they are above the nominal limit.
The present paper focuses on a new class of mesh filter for grayscale images, called grid smoothi... more The present paper focuses on a new class of mesh filter for grayscale images, called grid smoothing filter. The framework presented considers an image as a sampling grid associated to a set of gray levels. Furthermore, the sampling grid is seen as mesh composed by vertices and ...
The lossy image compression method described in this paper uses a graph-based approach to reduce ... more The lossy image compression method described in this paper uses a graph-based approach to reduce the image size. The presented method is based on the assumption that any image may be decomposed into a structure and detailed components. The detail part is compressed with a frequencybased scheme (transform coding used in JPEG and JPEG2000 for example) while the structure component is processed with a grid smoothing assisted by a graph decimation technique. The performance of the compression method is demonstrated on few popular images.
Multi-Radio Multi-Channel (MRMC) systems are key to power control problems in wireless mesh netwo... more Multi-Radio Multi-Channel (MRMC) systems are key to power control problems in wireless mesh networks (WMNs). In this paper, we present asynchronous multiple-state based power control for MRMC WMNs. First, WMN is represented as a set of disjoint Unified Channel Graphs (UCGs). Second, each network interface card (NIC) or radio assigned to a unique UCG adjusts transmission power using predicted multiple interaction state variables (IV) across UCGs. Depending on the size of queue loads and intra-and inter-channel states, each NIC optimizes transmission power locally and asynchronously. A new power selection MRMC unification protocol (PMMUP) is proposed that coordinates interactions among radios. The efficacy of the proposed method is investigated through simulations.
Abstract This paper describes an algorithm for a visual human-machine interface that infers a per... more Abstract This paper describes an algorithm for a visual human-machine interface that infers a person's intention from the motion of the hand. Work in progress shows a proof of concept tested on static images. The context for which this solution is intended is that of wheelchair ...
2012 Sixth IEEE/PES Transmission and Distribution: Latin America Conference and Exposition (T&D-LA), 2012
This paper seeks to identify and classify power system networks based on their inherent definitiv... more This paper seeks to identify and classify power system networks based on their inherent definitive structural property. The participation between the load buses is observable from the eigenvectors obtained from a Schur complement of the Y-admittance matrix. This is used to classify power system networks as either topologically strong or weak. Results show that in a topologically weak network, load voltages are below the nominal voltage limit. Conversely, in a topologically strong network they are above the nominal limit.
In this work, a general concept of the human-exoskeleton compatibility and interaction control is... more In this work, a general concept of the human-exoskeleton compatibility and interaction control is addressed. Rehabilitation, as applied to humans with motor control disorder, involves repetitive gait training in relation to lower limb extremity and repetitive task training in relation to upper limb extremity. It is in this regard that exoskeletal systems must be kinematically compatible with those of the subject in order to guarantee that the subject is being trained properly. The incompatibility between the wearable robotic device and the wearer results in joint misalignment, thus introducing interaction forces during movement. This, therefore, leads to the introduction of the need for interaction control in wearable robotic devices. Human-exoskeleton joint alignment is an uphill task; hence, measures to actualize this in order to guarantee the safety and comfort of humans are necessary. These measures depend on the types of joints involved in the rehabilitation or assistive proces...
A bounded control strategy is employed for the rehabilitation and assistance of a patient with lo... more A bounded control strategy is employed for the rehabilitation and assistance of a patient with lower-limb disorder. Complete and partial lower-limb motor function disorders are considered. This application is centered on the knee and the ankle joint level, thereby considering a user in a sitting position. A high gain observer is used in the estimation of the angular position and angular velocities which is then applied to the estimation of the joint torques. The level of human contribution is feedback of a fraction of the estimated joint torque. This is utilised in order to meet the demands for a bounded human torque; that is, τh≤N2,n≤N1,n. The asymptotic stability of the bounded control law without human contribution and the convergence analysis of the high gain observer is verified using Lyapunov-based analysis. Simulations are performed to verify the proposed control law. Results obtained guarantee a fair trajectory tracking of the physiotherapist trajectory.
2014 IEEE-RAS International Conference on Humanoid Robots, 2014
Faculty of Engineering and the Built Environment Department of …ELECTRICAL ENGINEERING / FSATI 2 ... more Faculty of Engineering and the Built Environment Department of …ELECTRICAL ENGINEERING / FSATI 2 AIMS & APPROACH • Aims: q To provide assistance and rehabilitative measures to humans with lower limb disorders. q Investigate a rehabilitation protocol method using CPGs. • Approach: q Inverse dynamics approach via adaptive coupled oscillators also known as CPGs. Faculty of Engineering and the Built Environment Department of …ELECTRICAL ENGINEERING / FSATI 3 Faculty of Engineering and the Built Environment Department of …ELECTRICAL ENGINEERING / FSATI 4 Faculty of Engineering and the Built Environment Department of …ELECTRICAL ENGINEERING / FSATI
Brain Computer Interfaces (BCI) rely on brain waves signal, such as electro-encephalogram (EEG) r... more Brain Computer Interfaces (BCI) rely on brain waves signal, such as electro-encephalogram (EEG) recording, to endow a disabled user with non-muscular communication. Given the very low signal-to-noise ratio of EEG, a signal enhancement phase is crucial for ensuring decent performances in BCI systems. Several methods have been proposed for EEG signal enhancement, such as Independent Component Analysis, Common Spatial Pattern, and Principal Component Analysis. We show that Canonical Correlation Analysis (CCA), initially introduced to SSVEP-based BCI as a feature extraction method, is a good candidate for such preprocessing state. Evaluation is performed on a recording from 5 subjects during a BCI task based on Steady-State Visual Evoked Potentials (SSVEP). We demonstrate that CCA significantly improves classification performances in SSVEP-based BCIs.
760: 761: 762: 763: The IASTED 2012 African Conferences, 2012
Research on wheelchairs is on its growing phase and assistive aids brought to wheelchair users in... more Research on wheelchairs is on its growing phase and assistive aids brought to wheelchair users in terms of adaptability to electric wheelchair have not yet been perfected. This paper presents the development of a User-Wheelchair-Environment (UWE) system in order to ease driving evaluation of wheelchair user. The system is modelled using Matlab/Simulink and it provides useful information such as linear and angular velocity and displacement in a 3D-virtual environment. The model consists of three main components (user interface, wheelchair model and virtual environment) which are individually modelled and later integrated altogether to form the UWE system. Simulation results are also presented.
This paper introduces a new methodology to assist teaching and learning in a time-constrained env... more This paper introduces a new methodology to assist teaching and learning in a time-constrained environment at the hand of two time-on-task examples. These examples are from the field of Electrical Engineering studies with a focus on firstyear studies and an advanced software design course taught at the Tshwane University of Technology in South Africa. In an endeavour to understand the timing model of the human brain to master and assimilate new information, a study was conducted to determine some of the parameters that could possibly have an influence on the timing model and how the brain perceives new information. From this study the Rope-Weaver's Principles were derived and are built on three well-known theories, comparative judgment, the Guttman scale and the learning curve, integrated into the new methodology. The Rope-Weaver's Principles are presented as an abstraction of the mathematical principles and the measures that underpin this study. The research was done from a participant-observer perspective with design research as central methodology. The research methodology involved a longitudinal study employing mixed-methods research. The results led to the observation of a toe or plateau in the infancy of the learning curve. The observed plateau has a direct influence on the order and time frame of the introduction of new study material in a formal educational programme. The results were found to adhere to the Weber-Fechner Law. This relates to other studies on animals, suggesting that the way the brain perceives stimuli or assimilate knowledge is hard-wired throughout the animal kingdom although the brain structures vary widely. It is proposed that Rope-Weaver's Principles, complementary to the current pool of teaching and learning theories, lead to a better mastery of the learning material or skills, moving persons under instruction from rule based training-behaviourism, to maxim integration-constructivism.
Leakage detection and localization in pipelines has become an important aspect of water managemen... more Leakage detection and localization in pipelines has become an important aspect of water management systems. Since monitoring leakage in large-scale water distribution networks (WDNs) is a challenging task, the need to develop a reliable and robust leak detection and localization technique is essential for loss reduction in potable WDNs. In this paper, some of the existing techniques for water leakage detection are discussed and open research areas and challenges are highlighted. It is concluded that despite the numerous research efforts and advancement in leakage detection technologies, a large scope is still open for further research in this domain. One such area is the effective detection of background type leakages that have not been covered fully in the literature. The utilization of wireless sensor networks for leakage detection purposes, its technical challenges as well as some future research areas are also presented. In a general remark, practical application of these techniques for large-scale water distribution networks is still a major concern. In this paper, an overview of this important problem is addressed.
Multi-Radio Multi-Channel (MRMC) systems are key to power control problems in WMNs. Previous stud... more Multi-Radio Multi-Channel (MRMC) systems are key to power control problems in WMNs. Previous studies have emphasized throughput maximization in such systems as the main design challenge and transmission power control treated as a secondary issue. In this paper, we present an autonomous power adaptation for MRMC WMNs. The transmit power is dynamically adapted by each network interface card (NIC) in response to the locally available energy in a node, queue load, and interference states of a channel. To achieve this, WMN is first represented as a set of Unified Channel Graphs (UCGs). Second, each NIC of a node is tuned to a UCG. Third, a power selection MRMC unification protocol (PMMUP) that coordinates Interaction variables (IV) from different UCGs and Unification variables (UV) from higher layers is proposed. PMMUP coordinates autonomous power optimization by the NICs of a node. The efficacy of the proposed method is investigated through simulations.
This paper describes a visual interface that recognizes the command request of a person by inferr... more This paper describes a visual interface that recognizes the command request of a person by inferring the intention to travel in a desired direction at a certain speed from the person’s head movements. A rotation and a vertical motion indicate the intent to change direction and speed respectively. The context for which this solution is intended is that of wheelchair
Simulation, Modeling, and Programming for Autonomous Robots, 2014
In this paper, an inverse dynamics approach by means of adaptive coupled oscillators is used in t... more In this paper, an inverse dynamics approach by means of adaptive coupled oscillators is used in the modelling and control of a lower limb orthosis applied at the knee and ankle joint level. This design is aimed at providing assistance and rehabilitative measures to humans with lower limb disorders and as such presents a platform for which their mobility performance can be improved. Adaptive oscillators are known to have the capability of learning high level parameters of sinusoidal, quasi-sinusoidal or non-sinusoidal signals (amplitude, frequency and offset). However, the later signal (non-sinusoidal) considered in this paper requires a number of oscillators in parallel to replicate the moving joint regarding filtering via adaptive oscillator. The dynamic model for the knee and ankle are considered to take the form of a damped pendulum model connected by two revolute joints. This maps the input torque of both joints (knee and ankle) to their output trajectories, hence integrating the different forces at the joint level of the different joints. The coupling effect is achieved by the use of coupled Adaptive Frequency Oscillator (AFO) for the estimation of the joint trajectories. Tracking performance for the knee-ankle orthosis is studied for non-sinusoidal reference trajectories, having a global coupling between the joints. The results obtained using SCILAB show a good performance of the controller trajectory tracking capabilities even in the presence of external disturbances.
2012 Sixth IEEE/PES Transmission and Distribution: Latin America Conference and Exposition (T&D-LA), 2012
ABSTRACT This paper seeks to identify and classify power system networks based on their inherent ... more ABSTRACT This paper seeks to identify and classify power system networks based on their inherent definitive structural property. The participation between the load buses is observable from the eigenvectors obtained from a Schur complement of the Y-admittance matrix. This is used to classify power system networks as either topologically strong or weak. Results show that in a topologically weak network, load voltages are below the nominal voltage limit. Conversely, in a topologically strong network they are above the nominal limit.
The present paper focuses on a new class of mesh filter for grayscale images, called grid smoothi... more The present paper focuses on a new class of mesh filter for grayscale images, called grid smoothing filter. The framework presented considers an image as a sampling grid associated to a set of gray levels. Furthermore, the sampling grid is seen as mesh composed by vertices and ...
The lossy image compression method described in this paper uses a graph-based approach to reduce ... more The lossy image compression method described in this paper uses a graph-based approach to reduce the image size. The presented method is based on the assumption that any image may be decomposed into a structure and detailed components. The detail part is compressed with a frequencybased scheme (transform coding used in JPEG and JPEG2000 for example) while the structure component is processed with a grid smoothing assisted by a graph decimation technique. The performance of the compression method is demonstrated on few popular images.
Multi-Radio Multi-Channel (MRMC) systems are key to power control problems in wireless mesh netwo... more Multi-Radio Multi-Channel (MRMC) systems are key to power control problems in wireless mesh networks (WMNs). In this paper, we present asynchronous multiple-state based power control for MRMC WMNs. First, WMN is represented as a set of disjoint Unified Channel Graphs (UCGs). Second, each network interface card (NIC) or radio assigned to a unique UCG adjusts transmission power using predicted multiple interaction state variables (IV) across UCGs. Depending on the size of queue loads and intra-and inter-channel states, each NIC optimizes transmission power locally and asynchronously. A new power selection MRMC unification protocol (PMMUP) is proposed that coordinates interactions among radios. The efficacy of the proposed method is investigated through simulations.
Abstract This paper describes an algorithm for a visual human-machine interface that infers a per... more Abstract This paper describes an algorithm for a visual human-machine interface that infers a person's intention from the motion of the hand. Work in progress shows a proof of concept tested on static images. The context for which this solution is intended is that of wheelchair ...
2012 Sixth IEEE/PES Transmission and Distribution: Latin America Conference and Exposition (T&D-LA), 2012
This paper seeks to identify and classify power system networks based on their inherent definitiv... more This paper seeks to identify and classify power system networks based on their inherent definitive structural property. The participation between the load buses is observable from the eigenvectors obtained from a Schur complement of the Y-admittance matrix. This is used to classify power system networks as either topologically strong or weak. Results show that in a topologically weak network, load voltages are below the nominal voltage limit. Conversely, in a topologically strong network they are above the nominal limit.
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Papers by Alex Hamam