Norhafizan Ahmad

Modeling, Control, and Simulation of Battery Storage Photovoltaic-Wave Energy Hybrid Renewable Power Generation Systems for Island Electrification in Malaysia

Today, the whole world faces a great challenge to overcome the environmental problems related to global energy production. Most of the islands throughout the world depend on fossil fuel importation with respect to energy production. Recent development and research on green energy sources can assure sustainable power supply for the islands. But unpredictable nature and high dependency on weather conditions are the main limitations of renewable energy sources. To overcome this drawback, different renewable sources and converters need to be integrated with each other. This paper proposes a standalone hybrid photovoltaic- (PV-) wave energy conversion system with energy storage. In the proposed hybrid system, control of the bidirectional buck-boost DC-DC converter (BBDC) is used to maintain the constant dc-link voltage. It also accumulates the excess hybrid power in the battery bank and supplies this power to the system load during the shortage of hybrid power. A three-phase complex vector control scheme voltage source inverter (VSI) is used to control the load side voltage in terms of the frequency and voltage amplitude. Based on the simulation results obtained from Matlab/Simulink, it has been found that the overall hybrid framework is capable of working under the variable weather and load conditions.

A fuzzy controller for lower limb exoskeletons during sit-to-stand and stand-to-sit movement using wearable sensors

Human motion is a daily and rhythmic activity. The exoskeleton concept is a very positive scientific approach for human rehabilitation in case of lower limb impairment. Although the exoskeleton shows potential, it is not yet applied extensively in clinical rehabilitation. In this research, a fuzzy based control algorithm is proposed for lower limb exoskeletons during sit-to-stand and stand-to-sit movements. Surface electromyograms (EMGs) are acquired from the vastus lateralis muscle using a wearable EMG sensor. The resultant acceleration angle along the z-axis is determined from a kinematics sensor. Twenty volunteers were chosen to perform the experiments. The whole experiment was accomplished in two phases. In the first phase, acceleration angles and EMG data were acquired from the volunteers during both sit-to-stand and stand-to-sit motions. During sit-to-stand movements, the average acceleration angle at activation was 11° – 48° and the EMG varied from −0.19 mV to +0.19 mV. On the other hand, during stand-to-sit movements, the average acceleration angle was found to be 57.5°–108° at the activation point and the EMG varied from −0.32 mV to +0.32 mV. In the second phase, a fuzzy controller was designed from the experimental data. The controller was tested and validated with both offline and real time data using LabVIEW.

Prospect of wave energy in Malaysia

In developing country like Malaysia, the demand for electricity is expected to rise with increasing urbanization and rapid industrialization. Currently energy production is mainly dependent on fossil fuel but in the near future fossil fuels will not be sustainable because of the depletion of existing reserves and their impact on the environment. Wave energy is an environmentally friendly and fastest growing renewable energy source for a sustainable electrical power generation of the future. Unlike others renewable energy resources, wave energy can produce electric power all over the year. As Malaysia has a total coastline of 4,675 kilometers so there is a great potential for utilization of wave energy in Malaysia especially along the coast and the islands. This paper presents a feasibility study of wave energy at different locations in Malaysia including the estimation of the total power available from the seas surroundings Malaysia. Furthermore, the analysis of investment, operation and maintenance cost for a wave farm is also presented.

Application of Data Acquisition and Telemetry System into a Solar Vehicle

The Center for Product Design and Manufacturing (CPDM) of University Malaya going to take part in the World Solar Challenge (WSC) 2009. It is a biannual solar powered car race over 3021 km from Darwin to Adelaide. The aim of this project is to build a system for monitoring performance of the solar vehicle during testing and race, a data acquisition and telemetry (DaqT) system is needed. In this project, a DaqT system will be developed using National Instruments’ (NI) LabVIEW, compactRIO (cRIO) and MaxStream Xstream Radio Frequency modules. The DaqT is able to measure signals from sensors which are thermocouples, current transducers, battery storage and tachometer. Experiment is conducted to investigate the capability of the DaqT system to process signals from essential sensors, transmit data with wireless communication and data logging. The results of this project from the experiment, the DaqT manage to transmit data in open space up to 700 meters and the percentages of the error is below 5%.

Technical Study of a Standalone Photovoltaic–Wind Energy Based Hybrid Power Supply Systems for Island Electrification in Malaysia

Energy is one of the most important factors in the socioeconomic development of a country. In a developing country like Malaysia, the development of islands is mostly related to the availability of electric power. Power generated by renewable energy sources has recently become one of the most promising solutions for the electrification of islands and remote rural areas. But high dependency on weather conditions and the unpredictable nature of these renewable energy sources are the main drawbacks. To overcome this weakness, different green energy sources and power electronic converters need to be integrated with each other. This study presents a battery storage hybrid standalone photovoltaic-wind energy power supply system. In the proposed standalone hybrid system, a DC-DC buck-boost bidirectional converter controller is used to accumulates the surplus hybrid power in the battery bank and supplies this power to the load during the hybrid power shortage by maintaining the constant dc-link voltage. A three-phase voltage source inverter complex vector control scheme is used to control the load side voltage in terms of the voltage amplitude and frequency. Based on the simulation results obtained from MATLAB/Simulink, it has been found that the overall hybrid framework is capable of working under variable weather and load conditions.

Robotic System Development for Cooperative Orthopedic Drilling Assistance

This paper describes a robotic bone drilling and screwing system for applications in orthopedic surgery. The goal is to realize two robot manipulators performing cooperative bone drilling. The proposed cooperative bone drilling system can be divided into hardware and software development. The hardware development section consists of two robot manipulator arms, which perform drilling and gripping of the bone, and operates using two joysticks. The software section assists the surgeon in visual and navigation control of those robot manipulators. Controller used in this system can be included in the hardware and software sections. Disturbance observer based position control was used in the robot manipulator maneuver and reposition controller (cooperative control) was used in cooperative drilling operation to maintain the alignment of the drill bit during drilling. A mathematical model for the control system was designed and a real environment mimicking simulation for bone drilling was designed. The result of the simulation shows that the cooperative robot system managed to perform cooperative drilling when misalignment occurs during bone drilling. The bone gripping robot managed to restore the drill bit to its ideal alignment in every event of misalignment in the drilling axis. Therefore this cooperative system has potential application in experimental orthopedic surgery.

Prospect of stand-alone wave-powered water desalination system

AbstractOur earth is a water planet; nearly two thirds of the earth’s surface is covered by ocean water. But the shortage of fresh water is a major problem in many areas, especially in rural villages near to the sea or islands. Now, renewable energy-based desalination system is rising around the world due to the adverse environmental effect and high-energy requirements of the conventional fuel-based desalination system. This paper describes the prospect of an off-grid stand-alone wave-powered reverse osmosis desalination system for those areas. A simulation model for the prediction of the wave power delivered for a given value of the wave height and period is adopted. Based on the availability of the wave data, the amount of the water produced at different sites of Malaysia can be calculated in this paper. In addition, this paper deals with an economical analysis of wave energy production for reverse osmosis desalination system.

An off-grid stand-alone wave energy supply system with maximum power extraction scheme for green energy utilization in Malaysian Island

AbstractEnergy is one of the most important factors in the socioeconomic development of a country. In a developing country like Malaysia, the development of islands is mostly related to the availability of electric power. As an island surrounded by sea, power generated by wave energy source will become one of the most promising solutions for the electrification of island areas. But, the unpredictable nature of the wave energy source is the main drawback. This paper presents a novel stand-alone wave energy supply system modeling with maximum power tracking and an energy storage-based power management algorithm in MATLAB/Simulink environment. The main contributions of this research work are eliminating the intermittent power generation nature of wave energy and efficiently extract the maximum wave power. In the proposed stand-alone system, a DC–DC bidirectional buck-boost converter controller is used to maintain the constant dc-link voltage. It also accumulates the surplus wave power in the battery bank and...

A study on muscle activities through surface EMG for lower limb exoskeleton controller

The motion of human body is complex but perfect and integrated effort of brain, nerves and muscles. Exoskeleton is a promising idea for human rehabilitation of the lower limb that is weak enough to move. EMG signal contains the information of human movement and can be considered as one of the most powerful input to exoskeleton controller. In this research, the activity of the lower limb muscles that are responsible for human sit to stand and stand to sit movement has been studied. In this regard, the activities of three muscles viz. rectus femoris, vastus lateralis and biceps femoris have been observed and recorded to perceive their activation pattern. The experimental results show that the maximum voltage of vastus lateralis at activation moment is greater or equal to +0.1 mV or lesser or equal to -0.1 mVduring sit to stand and stand to sit movement whereas same throughput was found for biceps femoris during sit to stand and for rectus femoris during stand to sit movement only.

Exoskeleton robot control for synchronous walking assistance in repetitive manual handling works based on dual unscented Kalman filter

Prolong walking is a notable risk factor for work-related lower-limb disorders (WRLLD) in industries such as agriculture, construction, service profession, healthcare and retail works. It is one of the common causes of lower limb fatigue or muscular exhaustion leading to poor balance and fall. Exoskeleton technology is seen as a modern strategy to assist worker’s in these professions to minimize or eliminate the risk of WRLLDs. Exoskeleton has potentials to benefit workers in prolong walking (amongst others) by augmenting their strength, increasing their endurance, and minimizing high muscular activation, resulting in overall work efficiency and productivity. Controlling exoskeleton to achieve this purpose for able-bodied personnel without impeding their natural movement is, however, challenging. In this study, we propose a control strategy that integrates a Dual Unscented Kalman Filter (DUKF) for trajectory generation/prediction of the spatio-temporal features of human walking (i.e. joint position, and velocity, and acceleration) and an impedance cum supervisory controller to enable the exoskeleton to follow this trajectory to synchronize with the human walking. Experiment is conducted with four subjects carrying a load and walking at their normal speed- a typical scenario in industries. EMG signals taken at two muscles: Right Vastus Intermedius (on the thigh) and Right Gastrocnemius (on the calf) indicated reduction in muscular activation during the experiment. The results also show the ability of the control system to predict spatio-temporal features of the pilots’ walking and to enable the exoskeleton to move in concert with the pilot.