Improving μ-wire electro-discharge machining operation of polished silicon wafer by conductive coating

Micro-Wire Electro-discharge machining (-WEDM) is a nonconventional machining technology which is extensively used for metal based micro fabrication process. This is a non-contact machining process where material removal is taken place by electro-thermal action. -WEDM process is difficult to be applied for semiconductor material like Silicon (Si). In this paper a new approach is proposed for machining polished Si (p-type, resistivity 1-50 -cm) wafer. In this method, initially Si workpiece is coated with a conductive material (gold for this study) and then -WEDM operation is carried out. Finally, after WEDM operation, the conductive layer is removed from the polished Si substrate without damaging the substrate. WEDM process stability was found to be improved (up to 60 times for certain machining condition) if coated Si wafer is used as compared to uncoated Si workpiece. Material removal rate was also found to be increased by a good margin (~ 100% maximum) for coated Si wafer. Overall this new method of -WEDM operation of polished Si wafer has been found to be more efficient and useful

Voltage supply and voltage regulation

A stable voltage supply is important for the proper operation of electronic devices. Stability is characterized by the ability of the voltage output to stay constant and ripplefree regardless of how much load is connected to the circuit. There is a brief discussion on how much inaccuracy is caused by voltage supplies which are prone to voltage fluctuations due to switching phenomenon taking place in the circuit, load fluctuations or temperature change

Machine condition monitoring and fault diagnosis using spectral analysis techniques

There is need to continuously monitor the conditions of complex, expensive and process-critical machinery in order to detect its incipient breakdown as well as to ensure its high performance and operating safety. Depending on the application, several techniques are available for monitoring the condition of a machine. Vibration monitoring of rotating machinery is considered in this paper so as develop a selfdiagnosis tool for monitoring machines’ conditions. To achieve this a vibration fault simulation rig (VFSR) is designed and constructed so as to simulate and analyze some of the most common vibration signals encountered in rotating machinery. Vibration data are collected from the piezoelectric accelerometers placed at locations that provide rigid vibration transmission to them. Both normal and fault signals are analyzed using the singular value decomposition (SVD) algorithm so as to compute the parameters of the auto regressive moving average (ARMA) models. Machine condition monitoring is then based on the AR or ARMA spectra so as to overcome some of the limitations of the fast Fourier transform (FFT) techniques. Furthermore the estimated AR model parameters and the distribution of the singular values can be used in conjunction with the spectral peaks in making comparison between healthy and faulty conditions. Different fault conditions have been successfully simulated and analyzed using the VFSR in this paper. Results of analysis clearly indicate that this method of analysis can be further developed and used for self-diagnosis, predictive maintenance and intelligent-based monitoring

Fuzzy-PID controller for semi-active vibration control using magnetorheological fluid damper

Magnetorheological (MR) dampers are considered as excellent prospect to the vibration control in automotive engineering. To overcome the effect from road disturbances many control algorithms have been developed and opted to control the vibration of the car. In this study, the methodology adopted to get a control structure is based on the experimental results. Experiments have been conducted to establish the behaviour of the MR damper. In this paper, the behavior of MR damper is studied and used in implementing vibration control. The force-displacement and force-velocity response with varying current has been established for the MR damper. The force for the upward motion and downward motion of damper piston is found increasing with current and velocity. In the cycle mode which is the combination of upward and downward motion of the piston, the force having hysteresis behaviour is found increasing with current. Results of this study may serve to aid in the modelling of MR damper for control applications

Self-powered solar tracking system part 3 : system integration and testing

Solar energy is the least polluting and most inexhaustible of all known energy sources. The sun bathers the earth with more energy each minute then the world consumes in one year. In Malaysia, the sun intensity does not vary with season. It is a suitable place to develop the solar cell system. To make solar energy more efficient, the solar panel system must be optimized. This project is regarding the development of a sun tracking solar system [1, 2]. This system is a simple tracking solar system using linear actuator, motor and light sensor. The solar tracking system used in this method could increase the power collection efficiency by developing a device that can track the sun to keep the panel at normal to its rays. To utilize the power, this system is made self-powered using the mechanism of battery charging. The design of the tracking system consists of both mechanical and electrical parts. For mechanical part, we need to control the tilt angle of the panel according to the elevation angle of the sun [3-5]. The movement of the panel controlled by the actuators must be accurate according to the sun position. There are several types of actuators and motors those are commonly used for tracking system. For the electrical part, we need to affix the functions of autonomous using electronics components such as Arduino microcontroller [6], motor driver. The self-powered feature need electrical component that can integrate between photovoltaic panel, batteries and load supply. The system modelling is discussed in chapter 2 and system design is discussed in chapter 3. This chapter discusses the system integration and testing with a discussion on results

Active vibration control using piezoelectric actuator: implementation of ant colony optimization technique in virtual experimentation

This paper demonstrates the implementation of virtual experiment using COMSOL Mutiphysics – MATLAB integration for optimization in active vibration control system. The benchmark model is a simply supported thin plate excited and attenuated by two piezoelectric patches. Instead of using equation-based modeling to represent the system, optimization of the sensor-actuator location and controller gains are conducted directly on the finite element model in COMSOL Multiphysics via Livelink for MATLAB function. The optimization is based on the average energy reduction across a frequency range between 11 Hz to 50 Hz, which covers the first three modes. It is found that the maximum attenuation achieved is 68.31% using optimal values of ensor -actuator location and controller gains

Active vibration control of a beam with piezoelectric patches: real-time implementation with xPC target

Active control of a vibrating beam using smart materials such as piezoelectric materials is examined in this paper. A model based on Euler-Bernoulli beam equation has been developed a n d . then extended with bonded three piezoelectric patches which act as sensor, actuator and exciter. The sensor and actuator are collocated to achieve a minimum phase. The aim of this research work is to control the first three resonant modes. To achieve this, a compensated inverse PID controller is developed and- tuned to damp these modes using MATLAB. The designed controller for damping each mode is then combined in parallel to damp any of the three modes. Finally, the simulation results are verified experimentally and the real-time implementation is carried out with XPC target toolbox in MATLAB

Parallel manipulator for auto tracking system: virtual prototyping using LabVIEW- Solidworks

Free-space optics (FSO) communication is a technology that uses light to transmit data through free space. The most important in FSO communication is the alignment between transmitter and receiver telescope. However, since the transmission medium of FSO is atmosphere, it will give misalignment between transceivers. Hence, tracking system is required to solve the problem between the transmitter and receivers. The 3-RPS parallel manipulator has been designed as a tracking system for the alignment between transceivers. First, a prototype of the system is designed in SolidWorks and integrated with LabVIEW software to perform virtual prototyping. Then, the result of virtual prrotyping is discusse

Study on micro-patterning process of vertically aligned carbon nanotubes (VACNTs)

Vertically aligned carbon nanotubes (VACNTs) have drawn significant attention by the researchers because of their nanometric size and favorable material properties. Patterning of CNT forests in the micrometric domain is very important for their application in the area of microelectromechanical system (MEMS). For the first time this paper reports, detailed experimental investigation on a post growth m-patterning process of VACNT forests. The micromechanical bending (M2B) process was locally applied at the targeted area in order to change the alignment of VACNT forests. Interestingly, the VACNT forest was transformed from typical black body absorber to reflective mirror as the M2B process was applied. Several parameters were identified that govern the resultant patterns such as rotational spindle speed, lateral bending speed, step size, tool morphology, and total depth of bend. Optimization of the parameters was carried out experimentally to obtain the best surface roughness and integrity of the microstructure. A minimum average surface roughness of Ra D 15 nm was achieved with 2000 rpm spindle speed, 1 mm/min bending speed and 1 mm step size