Applied Mechanics and Materials Vols. 110-116

Abstract: Five-axes machines with three translational and two rotation axes are becoming increasingly popular in serving the needs of the mass production industry due to their ability to handle geometrically complex workpieces using the rotational axes. The rotation axes lead to an inevitable non-linearity of the tool tip trajectory and the so-called kinematics errors appearing due to the specific kinematics of the machine. An interesting question is whether it is possible to compensate this error by introducing an additional rotation axis. We present an extension of an optimization algorithm developed earlier by the authors for five-axis machining based on an optimal angle sequencing (the shortest path optimization). The extension is a combination of the shortest path strategy and the use of the additional axis. The method to calculate post processor for the six-axes machine is included.

Abstract: This paper presents the design considerations and the design procedure for low and medium power electrostatic energy harvester. First, the principle of electrostatic harvester is discussed then the design considerations are analyzed and assessed. Our assessments indicate that the electrostatic generator requires motion energy at low frequency to achieve higher power generation. This motion produces a higher power per unit volume in comparison to the vibration. The best material that can be used for the electrodes is silver as it has a higher conductivity, reliability, stability and it can handle high voltage up to 100 V when compared to the other common capacitor materials. The in-plane overlap realization method can be considered to be a suitable choice when applied to variable capacitor machine. With regard to the conditioning circuits, the switched capacitor regulator is the most appropriate option as it can solve the sizing problem and provides solution for the up or down conversion of voltage when comparing it with the other conditioning circuits. Finally, we propose a general electrostatic harvester design procedure according to the addressed designed considerations.

Abstract: This paper presents a novel sensorless maximum power point tracking (MPPT) control strategy for capturing the maximum energy from the fluctuating wind speed that being used in the stand-alone small scale variable speed wind turbine generator system (VSWTGS). The generated electricity from the wind turbine systems is used to charge battery energy storage. The whole system including the wind turbine, permanent magnet synchronous generator (PMSG), power converter, filter and lead acid battery has been simulated in Matlab/SimPowerSystem simulation software. The MPPT controller is developed to function as a wind speed estimator to generate an appropriate duty cycle for controlling power MOSFET switch in of the boost converter in order to capture maximum power in variable wind speed. From the simulation results, the power converters and filters are showing good performance in charging the lead acid battery. Besides, the novel MPPT controller is capable of extracting the maximum power from the fluctuating wind speed and exhibits good performance in both steady state and transient condition.

Abstract: Capacitor bushings are one of the key components in power transformers. Although their price is a negligible part of the total price of the power transformer, their quality has a significant effect on performance and reliability of power transformers. In high voltage capacitor bushings, the intensity of voltage and electric field on bushing abacus is very high. This high intensity is also observed in flange parts. The amount of multi layer insulator among the electrodes or floating plates in capacitor bushing make equi-potential surfaces and reduction of electric field in these areas can greatly improve the capacitor bushing performance. In this paper, we investigate the reduction of field intensity and electrical tension and also improvement in voltage control by displacing floating plates which are in the form of aluminum foils stick to impregnated paper. To calculate the field intensity, we used the MAXWELL software using FEM (Finite element method). Using this new method of placing capacitor core its effect on voltage profile reduction and field electrical tension is shown. Over voltage and pollution effects are also investigate on power transformer bushings.

Abstract: The objective of this research is to control a robot arm by using Thai voice commands. (CRATVC) The research was conducted by speaking a user’s voice commands to a computer, and then the computer system converted the voice commands into digital signal. Finally, a robot arm is operated based on the Thai voice digital signal. The experiment was conducted on the robot arm with six Thai voice commands, which were: 1) gripper opened, 2) gripper closed, 3) arm up, 4) arm down, 5) turn right, and 6) turn left. The experimental precisions are 91.67%, 89.17% and 65.83% in a quiet room, an office room and a noisy room, respectively.

Abstract: Increasing application of distributed generation on distribution networks is the direct impact of development of technology and the energy disasters that the world is encountering. Using these resources in distribution network is one of the most influential solutions to reduce losses, improve voltage profile and improve power quality. To obtain these goals the resources capacity and the installation place are of a crucial importance. In this paper a new method is proposed to find the optimal and simultaneous place and capacity of these resources to reduce losses, improve voltage profile and reduce network harmonics. The proposed method is also capable of identifying the appropriate number of resources. The method is tested on actual power network of Zanjan Province, Iran and the simulation results are presented and discussed. Genetic algorithm is used to obtain the best answers.

Abstract: This paper investigates voltage stability of the power system during steady state and transient conditions. The voltage stability enhancement is achieved by utilizing FACTS devices at the best location of the system. The weakest bus in the system is the best location to implement shunt compensation device. In this paper, the weakest buses are identified via a fuzzy technique that utilizes two critical indices: Line Flow Index (LFI) and Voltage Profile Index (VPI) during normal and fault conditions. These indices are used to evaluate Criticality Index (CI) using Fuzzy rules, and thus, the system buses are ranked. Remedial actions are discussed to enhance the power system voltage stability by using FACTS devices (SVC and STATCOM) at the most vulnerable system buses. The results of this study show that the (STATCOM) performance is preferable to that of the (SVC) during fault conditions.

Abstract: This paper proposes a comparison of new evolutionary multi agent based particle swarm optimization algorithms for solving optimal power flows with security constraints (line flows and bus voltages). These methods combine the multi agents in two dimensional and cubic lattice structures with particle swarm optimization (PSO) to form two new algorithms. In both Two Dimensional Lattice Structured Multi Agent based Particle Swarm Optimization (TDLSMAPSO) and Cubic Lattice Structured Multi Agent based Particle Swarm Optimization (CLSMAPSO), an agent represents a particle in cubic lattice structure to PSO, and a candidate solution to the OPF problem. All agents live in a square and cubic lattice like environments, with agents fixed on a lattice point in the ascending order of their fitness value. In order to obtain the optimal solution, each agent in cubic and square lattice competes and cooperates with its neighbors. Making use of these agent-agent interactions, CLSMAPSO and TDLSMAPSO realizes the purpose of minimizing the objective function value. CLSMAPSO and TDLSMAPSO realizations were applied to IEEE 30 bus system. Simulation results show that proposed approaches gives better solution than earlier reported approaches in quick time.

Abstract: In this paper, modeling and simulation of Turbogenerators has been presented using artificial neural networks. The training and testing of neural network was done by MATLAB 6.5.1 software in order to find the optimum values of weights and biases. To find the optimal neural structure, training of several structures with two layers and three layers with different number of neurons in each layer has been done. Moreover, the neural network qualified with the least amount of error was presented along with their related charts.

Abstract: This paper introduces a new approach for me-chanical design of planar six-bar linkages with rotary joints which produce two dwells in each cycle of the input crank. The approach builds on the concept of function generation in a simple manner. The synthesis problem is posed as a single-objective constrained optimisation problem. A genetic algorithm-based optimisation scheme, namely the Non-dominated Sorting Genetic Algorithm-II (NSGA-II) has been used for solving the optimisation problem. The proposed method has been illustrated by means of an example problem from a recent contribution to literature. It is seen that the results compare favourably with the existing work.