Advanced Materials Research Vols. 463-464

Abstract: Electric power quality, which is a current interest to several power utilities all over the world, is often severely affected by harmonics and transient disturbances. There is no unique model which can assess the power quality problem and to identify and classify them properly. Existing automatic recognition methods need improvement in terms of their versatility, reliability, and accuracy. The FUZZY LOGIC based tools have been applied for the PQ classification. This paper addresses Power quality problem classification by wavelet and fuzzy expert system. Major Key issues and challenges related to these advanced techniques in automatic classification of PQ problems are highlighted. New intelligent system technologies using DSP, expert systems, AI and machine learning provide some unique advantages in intelligent classification of PQ distortions

Abstract: The most powerful methods of systems analysis have been developed for linear control systems. For a linear control system, all the relationships between the variables are linear differential equations, usually with constant coefficients. Actual control systems usually contain some nonlinear elements. In the following we show how the equations for nonlinear systems may be linearized. But the result is only applicable in a sufficiently small region in the neighbourhood of equilibrium point. The table in this paper includes the nonlinear equations and their the linear approximation. Then it is easy to find out if the nonlinear system is or is not stable; the task that usually ranks among the difficult tasks in engineering practice.

Abstract: The main aim of this paper is to discuss the general design considerations for contractible water-jet propulsion system for mini underwater robot locomotion. The motivation of this paper is the problems that occurred to the motorized turbine blade propeller for a lower than centimeter scale underwater robot. Contractile water-jet propulsion mechanism is proposed to counter the turbine blade problem. In this research, active materials had been proposed as the actuator for the contractile function. The integration of active material structure and passive structure caused significant consequence on the kinematic and dynamic of the robot. This including the dimension variation, stress distribution as well as contraction force which affects the hydrodynamic efficiency of the propulsion. Several essential design considerations were highlighted and discussed.

Abstract: This paper presents the virtual prototype of the mono-axis tracking system used for improving the efficiency of a string of photovoltaic modules. The solar tracker simultaneously changes the daily position of the modules, using a linear actuator that drives a rack-pinion mechanism. The key in optimizing the tracking system is to maximize the received solar radiation and to minimize the energy consumption for tracking. The virtual prototype is developed using a digital platform which integrates the following software solutions: CATIA - for the solid modeling of the components, ADAMS - for developing the mechanical model in MBS (Multi-Body Systems) concept, and MATLAB/Simulink - for the control system design.

Abstract: The paper deals with an electronic interface built on Arduino electronics. The interface allows controlling several pneumatic grippers using a PC. The grippers are connected to the PC using the mentioned interface which is connected to PC through USB port. The authors are continuing a work developed since 2005 when a LPT electronic interface was developed.

Abstract: The operational fault of diesel engine caused by losing the required function in running is a random phenomenon. It needs to collect a large number of fault samples and reliability data to reveal the fault occurrence rule and describe it with mathematical method. In this paper, the fault law and mechanism of the engine connecting rod were researched by the physical and chemical analysis of the fault samples. The fault reasons and the fault mechanism can be found through the analysis of the organization structure, material properties, process features, heat treatment process and other reliability information of the fault sample. It can provide scientific basis for the failure exclusion as well as the optimization and improvement of connecting rod structure.

Abstract: The present study demonstrates the use of optimization technology in improving the bolted joint design. Design exploration from ANSYS Workbench is used in the study. The objective of the study was to minimize the bolted joint deformation in order to optimize the joint. Variations of the parameters such as bolt pretension force, friction coefficient and pressure were studied. The optimization study provided response charts of the different design variables on the output. Sensitivity analysis of the input variables helped in identifying the importance of each design variable and their respective effects on the output. Finally the different design points were rated based on a goal-driven optimization study and the best design is chosen. Single Graphical User Interface allowed quick learning and ease-of-use.

Abstract: With the large-scale direction development of wind turbine, the vibrations of wind turbines, which are rigid-flexible coupled multi-body systems, can be easily excited. Control system can be improved to reduce the vibration amplitude and load levels. Fluctuation-suppression pitch control strategy has been improved in this paper. The reference input rotation speed, which is normally constant, is required to change with rotation acceleration in pitch control in this new control strategy. Theory and simulation show that Fluctuation-suppression pitch control (FSPC) strategy can improve the vibration characters of wind turbine and suppress rotation speed and power fluctuation, and it is also quite effective for gust situation

Abstract: NERVA small space launcher under development in Romania by Politehnica University is based on the solution of hard take-off with three strep-on SRM boosters. Due to the very high thrust enhancement a lift-off loading of more than 40 g-s appears, which is quite challenging. The main challenge is connected with the possible uneven thrust and burn duration of the three SRE-s of the first stage, which we call fuzzy thrust. Experimental data show variations of up to 0.5 seconds in the duration of the powered phase of SRE-s, from a total of 3.0 seconds of a mean burn. Yet undetermined variations in the total ignition delay between individual motors are a stronger concern. While for the unique booster of the standard SA-2 vehicle the ignition delay has no impact, when those engines are forced to work in parallel the individual differences become catastrophic. Severe imbalance between the two lateral engines may occur, ending in a potentially severe damage of the launching rail, possible loss of flight stability along the boost phase and damage of the second stage structure. The problems regarding the efficiency of the propulsion system that accompany this project are considered and solutions are proposed for the high thrust augmentation of the booster stage. Cryogenic vs storable propellants are studied for thrust augmentation of the boosters.

Abstract: As for traditional sliding mode control (SMC) with linear sliding surface and the tracking error can’t convergent to zero in finite time, fast terminal sliding mode control (FTSMC) designed with introduction nonlinear function into sliding hyper-plane, which makes tracking error converge to zero in finite time. A global fast terminal sliding mode control (GFTSMC) was designed with SMC and FTSMC, the sliding surface of GFTSMC was designed and the control law was deduced, also the convergence time was computed and stability proved by Lyapunov theory. With simulation, the optimal sliding mode parameters was selected and applied this control strategy for wind energy conversion system (WECS), the simulation result shows this control system can realize optimal power tracking control for wind energy conversion system.