Applied Mechanics and Materials Vols. 110-116

Abstract: This paper presents a method to solve the Evolutionary Algorithm (EA) problems for optimal tuning of the Proportional-Deferential (PD) controller parameters. The major efficiency of the proposed method is the Genetic Algorithm (GA) stuck avoidance as well an appropriate estimation for GA lower and upper bounds. Also by this method for the Particle Swarm Optimization (PSO) methodology the initial choice of the controller parameters can be fulfilled to achieve the acceptable performance accuracies. For both GA and PSO methods, the Linear Quadratic Regulator (LQR) obtained trend is used as the reference for the determination of the aforementioned bounds and initial guess. The presented algorithm was applied to regulate a PD controller for the attitude control of a virtual satellite and also with Hardware-in-the-loop (HIL) reaction wheels. Heavy burden trying and error was eliminated from the PD controller design which can be mentioned as the important merit of the presented study.

Abstract: Unexpected errors may occur in any embedded systems. An error correction circuitry is used to prevent system errors. Parity bits generated from an encoder are needed to perform an error recovery process. Therefore, to be stored in the memory space should be added. In this paper, Parity bits to be stored without a memory space that can be used to error correction circuitry are proposed. The proposed method was designed in VHDL. The proposed design used the Reed-Solomon (RS) code of an error correction method. Then, 8 bits of information symbols and a symbol error correcting RS code were designed based on the design.

Abstract: Electric power steering is developed to reduce effort by providing steering assist to the driver of a vehicle. In recent years, a research regarding returnability is performed in order to improve driver's steering feeling. Returnability is affected to friction force in EPS system and reaction force through tire and rack. Usually in the EPS system, friction and Reaction force are uncertain components which are hard to measure. This paper introduces both estimation using sliding mode observer and control algorithm using input disturbance compensation for returnability of EPS system. And simulation confirms the results of the estimation and control algorithm.

Abstract: The objective of this paper is to design a neural network-based residual generator to detect the fault in the actuators for a specific communication satellite in its attitude control system (ACS). First, a design of dynamic neural network with dynamic neurons is done, those neurons corresponds a second order linear Infinite Impulse Response (IIR) filter and a nonlinear activation function with adjustable parameters. Second, the parameters from the network are adjusted to minimize a performance index specified by the output estimated error, with the given input-output data collected from the specific ACS. Then, the designed dynamic neural network is trained and applied for detecting the faults injected to the wheel, which is the main actuator in the normal mode for the communication satellite. Then the performance and capabilities of the designed network were tested and compared with a conventional model-based observer residual, showing the differences between these two methods, and indicating the benefit of the proposed design to know the real status of the momentum wheel. Finally, the application of the methods in a satellite ground station is discussed.

Abstract: The Heat Process Trainer PT326 (Feedback UK) model is obtained by using two different techniques one by the Ziegler-Nichols approximating method and the other with the system identification method. The Data acquisition card EC641 I/O PT326 is developed and tested. it can be used as an interface between PC and any similar controlled system. The “velocity” form of the PID controller algorithm is implemented in real time where this algorithm is an ideal of solving the bump less transfer mechanism between manual and automatic control operation and the implementation of anti-reset windup algorithm. The method of back propagation neural network algorithm online gives very good results with neither steady state error nor overshoots.

Abstract: a new hybrid optimization method including of simplex method and method of design of experiments is developed. The objective of the optimization includes the minimization of the root mean square level of structure borne sound. Application of this new hybrid optimization method is experienced on a square plate. The shape modification concept is considered. The structure’s local geometry modification values at the selected surface key-points are considered as design variables. It is shown that the presented hybrid optimization method is able to reduce the value of objective function with a few number of objective function evaluations.

Abstract: - Fault detection and elimination in industrial machineries can help prevent loss of life and financial assets. In this study four common faults in rotating machineries namely: 1) Mass Unbalance 2) Angular Misalignment 3) Bearing Faults and 4) Mechanical Looseness have been considered. Each of these defects has been created separately on a test rig comprising of an electrical motor coupled to a rotor assembly. A Vibrotest 60 vibration spectrum analyzer has been used to collect velocity spectrum of the vibration on the bearings. Eleven characteristic features have been chosen to distinguish different faults. Based on the acquired data an Artificial Neural Network Multi Layer Perceptrons (MLPs) and Radial Basis Functions (RBF) Neural Network has been designed to recognize each one of the aforementioned defects. After training the Neural Network, it was checked by new data gathered by new experiments and the results showed that the designed network can predict the faults with more than 75% reliability, and it can be a good assistance to an ordinary machine operator to guess the problem and hence make a good decision.

Abstract: In an Iranian oilfield development which is under construction nowadays, it is decided to inject the separated gas in the reservoir Instead of flaring it. For this reason the injection pressure is calculated about 520 bars. The maximum rate of injection will be 280 millions cubic feet per day (330 363.215 cubic meter/hour). This gas should be injected in the reservoir to increase its pressure but the most important thing here is the injection compressor configuration. 3 units has been considered to compress the gas and each unit had 100 MMSCFD capacity. For increasing the gas pressure two compression units are foreseen: flash unit and injection unit. In flash gas unit the pressure will increase from 6 bars to 75 bars and in injection unit from 75 bars to 525 bars. But the gas which is upgraded in the flash unit should be dehydrated in dehydration package before entering to the injection unit. Due to the high flow rate of injection and other reasons which are discussed in this paper, the compressors are selected from centrifugal types. It is shown that in both flash and injection units, the compressors should be considered multistage. By the injection of associated gas instead of flaring it, the environment can be prevented from pollution and the reservoir pressure always will be maintained in a desired level. (Abstract)

Abstract: In this paper, design, analysis and simulation of microelectromechanical system (MEMS) based inertial sensor type of tuning fork micro gyroscope have been presented. CoventorWare has been used for design and simulation. The proposed design has improved the performances and structure for small vibration amplitude to minimize the mechanical crosstalk. Simulation results show that the capacitance in sense mode, which is detected by variable-gap capacitors, is equal to 2.68 pF in each side of sense mode. Oscillations in drive and sense electrodes with 1-DOF and proof mass with 2-DOF ensure that the proposed model has no common mode that causes mechanical crosstalk.

Abstract: This paper presents a current mode biquad filter, which uses multiple output OTAs. The proposed filter design has electronic tunability because of the use of OTAs and is suitable for implementation in CMOS technology because of the use of grounded capacitors.