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25,002 Article Results

An Approach to Minimising Estimated Pincushion Camera Distortions

10.12928/telkomnika.v9i3.748
Folorunso Olufemi; Universiti Teknologi Malaysia Ayinde , Mohd Shahrizal; Universiti Teknologi Malaysia Sunar , Adekiigbe; Universiti Teknologi Malaysia Adebanjo , Obasan; Universiti Teknologi Malaysia Olukayode
 Minimizing camera distortion has been a focus of recent photorealism researches. Of the several types of camera distortions, researchers concentrated on the radial distortion being the most severe part of the total lens aberrations. Often, polynomial approximations by introducing distortion-specific parameters into the camera model have been methods of evaluating distortions. Of the two types of radial distortions, barrel, is the most discussed probably because of its dominance in cheap wide-angle lenses. In this paper, an approach to estimating and minimizing pincushion distortion by using fundamental surface area properties of the distorted image is proposed. This paper is significant as it reveals the importance of the topic and its implications on the camera. Demonstrations using four camera lenses show the robustness of this technique under different focal lengths conditions. The reliability of the approach is justified by comparing the results with the physical observations using (two tailed) t-test statistic. 
Volume: 9
Issue: 3
Page: 555-564
Publish at: 2011-12-01

Multiple Moving Obstacles Avoidance of Service Robot using Stereo Vision

10.12928/telkomnika.v9i3.733
Widodo; Institute of Technology Sepuluh Nopember (ITS) Budiharto , Ari; Institute of Technology Sepuluh Nopember (ITS) Santoso , Djoko; Institute of Technology Sepuluh Nopember (ITS) Purwanto , Achmad; Institute of Technology Sepuluh Nopember (ITS) Jazidie
In this paper, we propose a multiple moving obstacles avoidance using stereo vision for service robots in indoor environments. We assume that this model of service robot is used to deliver a cup to the recognized customer from the starting point to the destination.  The contribution of this research is a new method for multiple moving obstacle avoidance with Bayesian approach using stereo camera.  We have developed and introduced 3 main modules to recognize faces, to identify multiple moving obstacles and to maneuver of robot. A group of people who is walking  will be tracked as a multiple moving obstacle, and  the speed, direction, and distance of the moving obstacles is  estimated by a stereo camera in order that the robot can maneuver to avoid the collision.  To overcome the inaccuracies of vision sensor, Bayesian approach is used for estimate the absense and direction of obstacles. We present the results of the experiment of the service robot called Srikandi III which uses our proposed method and we also evaluate its performance. Experiments shown that our proposed method working well, and Bayesian approach proved increasing the estimation perform for absence and direction of moving obstacle.
Volume: 9
Issue: 3
Page: 433-444
Publish at: 2011-12-01

Assessment of Voltage Stability Using Network Equivalent

10.12928/telkomnika.v9i3.753
Priyanath; National Institute of Technology Agartala Das , Sunita Halder; Jadavpur University nee Dey , Abhijit; Bengal Engineering and Science University Chakrabarti , Tanaya; Jadavpur University Datta
 In this paper a fast system voltage stability index (FSVSI) has been proposed to assess overall system voltage stability of a multi-bus power system at a particular operating point using the concept of two bus network equivalent.  A universal direct voltage stability index has also been explored to assess local (DVSI) as well as overall system voltage stability (DSVSI). An index called system transmission quality factor (STQF) has been developed to assess the power transmission quality of the overall system in the context of voltage stability. Two FACTS controllers, TCSC and STATCOM have also been incorporated in the present study to observe their effectiveness to ensure voltage stabilty. STATCOM has been found to be superior in order to improve voltage stability of power system as compared to TCSC. The developed concept has been validated using practical India Easten Grid (WBSEB system) and it has a high potential of on-line application.
Volume: 9
Issue: 3
Page: 595-603
Publish at: 2011-12-01

Development of Tubular Linear Permanent Magnet Synchronous Motor Used in Oil-well Field

10.12928/telkomnika.v9i3.743
Yanliang; Shandong University Xu , Xiquan; Shandong University Liu
The tubular linear permanent magnet synchronous motor (TLPMSM) is developed to constitute a new oil-well pump system named as linear motor-driven one replacing the normal beam balanced pump system mainly in order to eliminate the damageable steel pole. Its structure is determined based on the real drive demand and the corresponding analysis results are given. At last a small prototyped TLPMSM with stator outer diameter of 140mm, effective stator length of 864mm is designed and manufactured to verify the theoretical analysis and investigate the performance, and make preparation for the large practicable prototype in the future.
Volume: 9
Issue: 3
Page: 515-522
Publish at: 2011-12-01

Behaviors Coordination and Learning on Autonomous Navigation of Physical Robot

10.12928/telkomnika.v9i3.738
Handy; Petra Christian University Wicaksono , Handry; Petra Christian University Khoswanto , Son; Electronics Engineering Polytechnic Institute of Surabaya Kuswadi
 Behaviors coordination is one of keypoints in behavior based robotics. Subsumption architecture and motor schema are example of their methods. In order to study their characteristics, experiments in physical robot are needed to be done. It can be concluded from experiment result that the first method gives quick, robust but non smooth response. Meanwhile the latter gives slower but smoother response and it is tending to reach target faster. Learning behavior improve robot’s performance in handling uncertainty. Q learning is popular reinforcement learning method that has been used in robot learning because it is simple, convergent and off policy. The learning rate of Q affects robot’s performance in learning phase. Q learning algorithm is implemented in subsumption architecture of physical robot. As the result, robot succeeds to do autonomous navigation task although it has some limitations in relation with sensor placement and characteristic.
Volume: 9
Issue: 3
Page: 473-482
Publish at: 2011-12-01

Coffee Bean Grade Determination Based on Image Parameter

10.12928/telkomnika.v9i3.747
Faridah; Universitas Gadjah Mada Faridah , Gea O. F.; Universitas Gadjah Mada Parikesit , Ferdiansjah; Universitas Gadjah Mada Ferdiansjah
Quality standard for coffee as an agriculture commodity in Indonesia uses defect system which is regulated in Standar Nasional Indonesia (SNI) for coffee bean, No: 01-2907-1999. In the Defect System standard, coffee bean is classified into six grades, from grade I to grade VI depending on the number of defect found in the coffee bean. Accuracy of this method heavily depends on the experience and the expertise of the human operators. The objective of the research is to develop a system to determine the coffee bean grading based on SNI No: 01-2907-1999. A visual sensor, a webcam connected to a computer, was used for image acquisition of coffee bean image samples, which were placed under uniform illumination of 414.5+2.9 lux. The computer performs feature extraction from parameters of coffee bean image samples in the term of texture (energy, entropy, contrast, homogeneity) and color (R mean, G mean, and B mean) and determines the grade of coffee bean based on the image parameters by implementing neural network algorithm. The accuracy of system testing for the coffee beans of grade I, II, III, IVA, IVB, V, and VI have the value of 100, 80, 60, 40, 100, 40, and 100%, respectively.
Volume: 9
Issue: 3
Page: 547-554
Publish at: 2011-12-01

A Lighting Control System in Buildings based on Fuzzy Logic

10.12928/telkomnika.v9i3.732
Seno D.; Tanjungpura University Panjaitan , Aryanto; Tanjungpura University Hartoyo
Lighting generally consumed 25%-50% of total electricity consumption in a building. Nowadays, the building lighting source is dominated by the use of fluorescent lamps. The previous technical papers by other researchers had focused on power density control of incandescent lamps, which is now rarely used, unconsidered national standard as control reference value, and required a high-cost in investment. By these reasons, this paper proposes a building lighting system based on fuzzy logic scheme to automate fluorescent lamps in order to achieve illumination according to Indonesian National Standard (SNI). The input variables were indoor lighting, inference from outdoor lighting, and occupancy. The output variable was the required illumination to achieve the standard. The required illumination determined the number of lamps that had to be turned on. In the experiment result, a classroom illumination of lighting without controller in workdays was about 350 lux, while with the proposed controller it varied between 250–300 lux close to the SNI, i.e. 250 lux. Meanwhile, with the proposed controller the electricity consumption for a classroom was 75% lower than the lighting without controller. 
Volume: 9
Issue: 3
Page: 423-432
Publish at: 2011-12-01

Performance Comparison of Enterprise Applications on Mobile Operating Systems

10.12928/telkomnika.v9i3.742
Adrian; Letterkenny Institute of Technology Mullally , Nigel; Letterkenny Institute of Technology McKelvey , Kevin; University of Ulster Curran
Due to the advances in mobile phone technology, Smartphones have the ability to access web services within applications the user interacts with to retrieve and send information from and to web services. As Smartphones have grown in popularity, the utilisation of both new web services and web services already in place will also grow. This paper provides a comparison of the two main types of web services, SOAP and REST.  We evaluate the performance of using SOAP and REST on a smartphone. The tests performed include the time taken to perform a web service call, the RAM used making a web service call and the data transmitted and received while making a web service call.
Volume: 9
Issue: 3
Page: 503-514
Publish at: 2011-12-01

Deterministic and Recursive Approach in Attitude Determination for InnoSAT

10.12928/telkomnika.v9i3.752
M. Fadly; Universiti Sains Malaysia M. Fadly , Othman; Universiti Sains Malaysia Sidek , Md Azlin; Universiti Sains Malaysia Md Said , Harijono; Universiti Putra Malaysia Djojodihardjo , Adam; Universiti Sains Malaysia Ain
Attitude determination system (ADS) was indispensable in attitude control of satellite. Especially for InnoSAT due to the limitation of budget, weight, and power, the attitude was determined using onboard position sensors. Previous research has successfully implemented the attitude determination using only Earth's magnetic field sensors for small attitude angle, but the approach produced quite big error for large attitude angle. This paper presents attitude determination for InnoSAT using combination of sun sensors and earth's magnetic field for large attitude angle. The attitude was determined using a deterministic (QUEST) and recursive (EKF) approach. A problem arises when using the sun sensors while the satellite experiencing eclipse. Consequently, the accuracy of both approaches was analyzed at eclipse and no eclipse conditions. The result shows that deterministic approach produced better accuracy at no eclipse but recursive approach produced better accuracy at eclipse. The strategy to apply the both approaches and eclipse conditions also discussed in this paper.
Volume: 9
Issue: 3
Page: 583-594
Publish at: 2011-12-01

Development of a Simulated Environment for Human-Robot Interaction

10.12928/telkomnika.v9i3.737
Jochen; University of Kaiserslautern Hirth , Syed Atif; University of Kaiserslautern Mehdi , Norbert; University of Kaiserslautern Schmitz , Karsten; University of Kaiserslautern Berns
Human-robot interaction scenarios are extremely complicated and require precise definition of the environment variables for rigorously testing different aspects of robotic behavior. The environmental setup affects the behaviors of both the humans and the robots, as they respond differently under varying accoustic or lightning conditions. Moreover, conducting several experiments repeatedly with the humans as test subjects also causes behavioral changes in them and eventually the responses remain no longer similar to the already conducted experiments. Thus making it is impossible to perform interaction scenarios in a repeatable manner. Developing and using 3D simulations, where different parameters can be adjusted, is the most beneficial solution in such cases. This requires not only the development of different simulated robots but also the simulation of dynamic surroundings including the interaction partner. In this paper, we present a simulation framework that allows the simulation of human-robot interaction including the simulated interaction partner and its dynamics.
Volume: 9
Issue: 3
Page: 465-472
Publish at: 2011-12-01

A Simplfied Voltage Vector Selection Strategy for Direct Torque Control

10.12928/telkomnika.v9i3.746
Li Yaohua; Chang’an University Li Yaohua , Liu; Chang’an University Jingyu , Ma Jian; Chang’an University Ma Jian , Yu Qiang; Chang’an University Yu Qiang
The direct torque control (DTC) for permanent magnet synchronous motor (PMSM) under the control of switching table suffers from high torque ripple and variable switching frequency. For PMSM DTC system, voltage vector selection strategy as the hysteresis control principle determines the system’s performance. The angle (a) between stator flux vector and the applying voltage vector determines effect of the voltage vector on the amplitude of stator flux and torque angle. The effect of the voltage vector on toque is dependent on a, torque angle and parameters of PMSM. A voltage vector selection strategy based on the technology of space vector modulation (SVM) is proposed to control stator flux, torque angle and torque. Experimental results for a 15-kW interior PMSM show it can decrease stator current and torque ripples and fix the switching frequency.
Volume: 9
Issue: 3
Page: 539-546
Publish at: 2011-12-01

Improving Output Voltage of the Three Phase Six-Switch Inverters

10.12928/telkomnika.v9i3.741
Ebrahim; University of Tabriz Babaei , Mehdi; Islamic Azad University Mahaei
 In this paper, a simple method for selecting the best conductive angle based on power factor of load in three phase six-switch inverters is proposed. Conductive angle from 120º to 180º, and power factor from 0 to 1 are changed for lead and lag loads. Then RMS and THD values of the output voltage are studied. Simulation results show that a special conductive angle for each specific power factor has to be used to improve the mentioned indices and applying conventional conductive angles 120º, 180º and 150º in some power factors increases THD and decreases RMS of output voltage.
Volume: 9
Issue: 3
Page: 497-502
Publish at: 2011-12-01

Steady-State Stability Assessment Using Neural Network Based on Network Equivalent

10.12928/telkomnika.v9i3.731
Indar Chaerah; Universitas Hasanuddin Gunadin , Muhammad; Institut Teknologi Sepuluh Nopember Abdillah , Adi; Institut Teknologi Sepuluh Nopember Soeprijanto , Ontoseno; Institut Teknologi Sepuluh Nopember Penangsang
Power systems in all over the world have increased in size and complexity due to rapid growth of widespread interconnection. This situation will make power system operated closer to steady-state stability limit (SSSL) resulting in higher probability voltage instability or voltage collapse. This paper presents SSSL assessment in power system using Artificial Neural Network (ANN) model based on REI-Dimo method. The equivalent REI-Dimo is used to determine SSSL index of the power systems. Then, the result of REI-Dimo will be taught on ANN method via online. Studies were carried out on a Java-Bali 500kV system. The simulation showed that the proposed method could accurately predict the proximity to SSSL in power system. The method was computationally efficient and suitable for online monitoring of steady-state stability condition in the power systems.
Volume: 9
Issue: 3
Page: 411-422
Publish at: 2011-12-01

Potential of Wind Speed for Wind Power Generation In Perlis, Northern Malaysia

10.12928/telkomnika.v9i3.750
I. Daut; Universiti Malaysia Perlis (UniMAP) I. Daut , M. Irwanto; Universiti Malaysia Perlis (UniMAP) M. Irwanto , Suwarno; Universiti Malaysia Perlis (UniMAP) Suwarno , Y.M. Irwan; Universiti Malaysia Perlis (UniMAP) Y.M. Irwan , N. Gomesh; Universiti Malaysia Perlis (UniMAP) N. Gomesh , N. S. Ahmad; Universiti Malaysia Perlis (UniMAP) N. S. Ahmad
 This paper presents an analysis of the wind speed characteristics in Perlis, Northern Malaysia for the year of 2006. The characteristics consist of daily, monthly and annual mean wind speed. The Weibull distribution function is applied to analyze the wind speed characteristics and used to calculate the wind power generation potential. Potential of wind power generation is observed and analyzed during 24 hours (9th March 2011). The analysis result of monthly mean wind power and energy density show that the early (January to march) and the end (December) of year have a high wind power and energy potential, but the middle of year they are very low, it is necessary to develop  a special wind power generation capable of harnessing the little wind resource available in Perlis. Observation during 24 hours (9th March 2011), for a 24 V wind power generation gives 10% of its total output voltage.
Volume: 9
Issue: 3
Page: 575-582
Publish at: 2011-12-01

A New Classification Technique in Mobile Robot Navigation

10.12928/telkomnika.v9i3.736
Siti; Sriwijaya University Nurmaini , Bambang; Sriwijaya University Tutuko
This paper presents a novel pattern recognition algorithm that use weightless neural network (WNNs) technique.This technique plays a role of situation classifier to judge the situation around the mobile robot environment and makes control decision in mobile robot navigation. The WNNs technique is choosen due to significant advantages over conventional neural network, such as they can be easily implemented in hardware using standard RAM, faster in training phase and work with small resources. Using a simple classification algorithm, the similar data will be grouped with each other and it will be possible to attach similar data classes to specific local areas in the mobile robot environment. This strategy is demonstrated in simple mobile robot powered by low cost microcontrollers with 512 bytes of RAM and low cost sensors. Experimental result shows, when number of neuron increases the average environmental recognition ratehas risen from 87.6% to 98.5%.The WNNs technique allows the mobile robot to recognize many and different environmental patterns and avoid obstacles in real time. Moreover, by using proposed WNNstechnique mobile robot has successfully reached the goal in dynamic environment compare to fuzzy logic technique and logic function, capable of dealing with uncertainty in sensor reading, achieving good performance in performing control actions with 0.56% error rate in mobile robot speed.
Volume: 9
Issue: 3
Page: 453-464
Publish at: 2011-12-01
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