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Shukor A.Z.,Yokohama National University | Shukor A.Z.,University Technical Malaysia Melaka | Fujimoto Y.,Yokohama National University
IEEE Transactions on Industrial Electronics | Year: 2014

This paper presents the direct-drive position control verification of a spiral motor in monoarticular configuration. The spiral motor is a newly developed high-thrust high-backdrivable direct-drive three-phase permanent-magnet motor with a unique 3-D structure. One of the possible uses of the spiral motor is to actuate musculoskeletal-like structure which is shown in animals and humans. This is achieved by indirectly actuating the elbow/shoulder joints via pulling/pushing the links by using a linear actuator. We describe the control methods for the direct drive of the spiral motor which are the decoupling control and independent control. Next, simulations were performed to assess the control parameter variation effects. Then, the experimental results confirm the validity of the control method in monoarticular position. The key element of the linear motion control of the spiral motor is the magnetic levitation (air gap between the stator and rotor) control and simultaneous angular motion control via vector d- and q-axis currents. © 1982-2012 IEEE. Source

Sutikno T.,Ahmad Dahlan University | Sutikno T.,University of Technology Malaysia | Idris N.R.N.,University of Technology Malaysia | Jidin A.,University Technical Malaysia Melaka | Cirstea M.N.,Anglia Ruskin University
IEEE Transactions on Industrial Informatics | Year: 2013

This paper presents a novel direct torque control (DTC) approach for induction machines, based on an improved torque and stator flux estimator and its implementation using field-programmable gate arrays (FPGA). The DTC performance is significantly improved by the use of FPGA, which can execute the DTC algorithm at higher sampling frequency. This leads to the reduction of the torque ripple and improved flux and torque estimations. The main achievements are: 1) calculating a discrete integration operation of stator flux using backward Euler approach; 2) modifying a so called nonrestoring method in calculating the complicated square root operation in stator flux estimator; 3) introducing a new flux sector determination method; 4) increasing the sampling frequency to 200 kHz such that the digital computation will perform similar to that of the analog operation; and 5) using two's complement fixed-point format approach to minimize calculation errors and the hardware resource usage in all operations. The design was achieved in VHDL, based on a Matlab/Simulink simulation model. The Hardware-in-the-Loop method is used to verify the functionality of the FPGA estimator. The simulation results are validated experimentally. Thus, it is demonstrated that FPGA implementation of DTC drives can achieve excellent performance at high sampling frequency. © 2005-2012 IEEE. Source

Ifayefunmi O.,University Technical Malaysia Melaka
Thin-Walled Structures | Year: 2016

This paper examines the buckling of short mild steel cylindrical shells subjected to axial compression. Cylinders were joined together using Metal Inert Gas (MIG) welding process with radius-to-thickness ratio, R/t, ranging from 25 to 100. The axial length of the specimens were assumed to be 111.8 mm. Past result on axially compressed cylinder machined using Computer Numerically Controlled (CNC) machining is compared with fresh experimental results on MIG manufactured axially compressed cylinder. The paper contains a comparison between theoretical predictions, ABAQUS FE results and experimental data for axially compressed cylinder. Details about material testing and collapse test are provided. As compared to the CNC machined specimen, results indicates that there is a good agreement between theoretical prediction, ABAQUS FE results and experimental data for MIG manufactured cylinder with radius-to-thickness ratio, R/t ranging from 25 to 100, with difference ranging between -7% and +2%. © 2015 Elsevier Ltd. All rights reserved. Source

Khamis A.,National University of Malaysia | Khamis A.,University Technical Malaysia Melaka | Shareef H.,National University of Malaysia | Bizkevelci E.,Tubitak Uzay | Khatib T.,National University of Malaysia
Renewable and Sustainable Energy Reviews | Year: 2013

Islanding detection of distributed generations (DGs) is one of the most important aspects of interconnecting DGs to the distribution system. Islanding detection techniques can generally be classified as remote methods, which are associated with islanding detection on the utility sides, and local methods, which are associated with islanding detection on the DG side. This paper presents a survey of various islanding detection techniques and their advantages and disadvantages. The paper focused on islanding detection using a conventional and intelligent technique. A summary table that compares and contrasts the existing methods is also presented. © 2013 Elsevier Ltd. All rights reserved. Source

Ramli M.Z.,University Technical Malaysia Melaka | Salam Z.,University of Technology Malaysia
IEEE Transactions on Power Electronics | Year: 2014

This paper proposes a simple circuit to recover the energy that otherwise would be lost due to the partial shadings on photovoltaic (PV) modules. Since the circuit can be readily retrofitted to an existing PV system, no modification on the central inverter is required. The main idea of the scheme is that, during partial shading, parts of the current from the nonshaded modules are harvested by an energy recovery circuit using power electronic switches and storage components. In doing so, the current of the PV string is maintained at the level generated by the shaded module. There is no need for the shaded module to be short-circuited; as a result, it can still actively produce output power (despite being partially shaded). To investigate the idea, the proposed circuit is retrofitted to a prototype PV system using eight modules. The partial shading conditions are emulated using a solar simulator with a controllable irradiance capability. The results are validated by a good agreement between the experimental and simulation works. © 2014 IEEE. Source

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