DIFFERENTIAL EVOLUTION FOR OPTIMIZATION OF PID GAIN IN ELECTRICAL DISCHARGE MACHINING CONTROL SYSTEM

ABSTRACT PID controller of servo control system maintains the gap between Electrode and workpiece in Electrical Dis- charge Machining (EDM). Capability of the controller is significant since machining process is a stochastic phenomenon and physical behaviour of the discharge is unpredictable. Therefore, a Proportional Integral Derivative (PID) controller using Differential Evolution (DE) algorithm is designed and applied to an EDM servo actuator system in order to find suitable gain parameters. Simulation results verify the capabilities and effectiveness of the DE algorithm to search the best configuration of PID gain to maintain the electrode position. Keywords: servo control system; electrical discharge machining; proportional integral derivative; con- troller tuning; differential evolution

Micro-crack characterization for metal-on-metal hip implant of textured surface using electrical discharge machining

In hip implant, it has been proven that surface texturing which is also known as dimples can improve the lubrication performance and reduce friction. However, little attention is paid to the effect of textured surface by assessing the crack formation on the dimple areas. This research focuses on the formation of cracks on dimple edges during manufacturing process using electrical discharge machining (EDM) as higher stress is produced in this area. The crack formation then was observed during operational use of metal-on-metal (MoM) hip implant in the case that the dimples parameters are not fully optimized. For dimple manufacturing on a S45C mild steel material, machining angles was varied at 50°, 70° and 90° using developed workpiece positioning system in this research. The pulse currents were set at 1 A, 2 A and 3 A. Cracks formed on the dimple edge after the machining were observed using Scanning Electron Microscope (SEM) and measured in terms of its length. Then, nine dimples were machined on the samples of acetabular cup part using the chosen EDM parameters. Friction screening on the hip implant samples with femoral head of 28 mm diameter and radial clearance of 30 pm was carried out using four-ball bearing machine. The loads varied up to 250 N, 500 N and 1000 N representing the loading gait in the hip joint. The formation of cracks on the dimple edges for each load was then observed. The experimental results showed that when lowest current 1A was applied, the micro-cracks total length appeared during EDM process increased substantially. For MoM hip implant, it was found that the optimal setting for the EDM machining was 3 A at 90° machining angle, taking into account the curved hip implant surface. However, more than 50% of the cracks formed during machining were removed after loading due to surface grooving. It is suggested that it is suitable to machine the dimples on the hip implant surface using EDM in terms of crack formation. While new cracks formed after the loading were found to be far more dominant than the original cracks due to EDM machining. The cracks were found to be much wider and longer especially with the imposition of the maximum load of 1000 N. The contribution of this study is on the effect of crack formation on hip implant improvement, as well as providing basic data of textured surface in hip implant. This is because the crack formed can cause wear and friction which can lead to wear fatigue in hip implant thus shorten lifespand its lifespan

Potential Neuroprotective Effect of Apis dorsata Honey Against Morphine Tolerance: An in-vivo Study

Background: To determine the effects of Apis dorsata honey on the development of morphine tolerance and oxidative stress in rats. Materials and Methods: A total of 40 male Sprague Dawley rats were injected (subcutaneous) with 10 mg/kg of morphine following oral administration of A. dorsata honey (0.5, 1.5, and 2.5g/kg). On day 15, the rats were euthanized, and the thalamus, spinal cord, and hippocampus were homogenized to assess iNOS and MDA using ELISA kits.Results: The honey of A. dorsata significantly prevented morphine tolerance to analgesia in the hotplate test on Day 14 (p<0.05). The biochemical assessment showed that A. dorsata honey significantly reduced MDA formation in the brain regions compared to the morphine control group at dose 2.5g/kg. Elevation of iNOS caused by chronic morphine intake was reduced in A. dorsata honey co-treatment. Conclusion: This study suggests the therapeutic role of A. dorsata honey in preventing morphine tolerance via inhibition of oxidative stress

MDMA-induced BV2 microglial cell activation in vitro

Background: 3,4-Methylenedioxymethamphetamine (MDMA) is a psychostimulant drug that induces neurotoxicity. Even though several psychostimulant substances activate microglia, little is known about MDMA's effects on these cells, and evidence of MDMA-induced microglial activation is equivocal. Materials and Methods: This study employed a murine microglial cell line, BV2, to examine the effects of MDMA on the microglia morphological changes and the survival of microglia in vitro. MDMA was incorporated into the media at the time of plating, and cell number and mitochondrial dehydrogenase activity (MTT) levels were determined in vitro. The level of pro-inflammatory cytokine TNF-α was also determined. Results: Treatment of BV2 cells with MDMA resulted in morphological changes, reduced cell viability after 24h incubation with the inhibitory concentration (IC50) value of 243.6 µg/mL, and increased TNF-α level in a dose-dependent manner. Conclusion: These findings proposed that MDMA could induce BV2 microglial cell activation in vitro and suggested that it has an essential role in developing MDMA use disorder

Design and implementation of flyback converter for electrical discharge machining power generator

Electrical Discharge Machining process has been widely used for manufacturing micro components due to its contactless process. Its application has also been introduced in machining micro pits on hip implant. In this paper, a new design of power generator is proposed in order to reduce micro crack while machining take place. Flyback Switch Mode Power Supply has been chosen because of its high efficiency. The simulation of Flyback converter using LT Spice is presented. The result shows that the system achieves 95.9% of efficiency. Experimental results show that flyback converter able to produce DC voltage up to 111.6

PID controller tuning by differential evolution algorithm on EDM servo control system

Maintaining gap between Electrode and workpiece in Electrical Discharge Machining (EDM) is very important since the capability of control system to keep the gap will improve the performance of this machine. Therefore to maintain the gap, a Proportional Integral Derivative (PID) controller is designed and applied to EDM servo actuator system. The objective of this work is to obtain a stable, robust and controlled system by tuning the PID controller using Differential Evolution (DE) algorithm. The controller for EDM die sinking is verified by simulation of the control system using MATLAB/Simulink program. Simulation results verify the capabilities and effectiveness of the DE algorithm to search the best configuration of PID parameters controller to control the electrode position

Modeling of flyback converter for micro machining biomedical component

Electrical Discharge Machining is a controlled process where pulsed electrical discharge is used to erode metal in a workpiece. A number of EDM power supplies utilizing different topologies have been widely developed for various applications. Nowadays, EDM process has been given a significant amount of research focus in manufacturing micro components with new low power topologies being utilized. Recently, a demand in micro machining has also extended into biomedical applications. In this paper a current mode flyback converter is implemented for micro machining biomedical component. A MATLAB/SIMULINK modeling technique of flyback converter is presented and the effectiveness of the flyback converter topology is evaluated through the simulation results obtained by varying the value of primary inductance

Some emerging opportunities of nanotechnology development for soilless and microgreen farming

Global food demand has increased in tandem with the world’s growing population, prompting calls for a new sustainable agricultural method. The scarcity of fertile soil and the world’s agricultural land have also become major concerns. Soilless and microgreen farming combined with nanotechnology may provide a revolutionary solution as well as a more sustainable and productive alternative to conventional farming. In this review, we look at the potential of nanotechnology in soilless and microgreen farming. The available but limited nanotechnology approaches in soilless farming include: (1) Nutrients nanoparticles to minimize nutrient losses and improve nutrient uptake and bioavailability in crops; (2) nano-sensing to provide real-time detection of p H, temperature, as well as quantifying the amount of the nutrient, allowing desired conditions control; and (3) incorporation of nanoparticles to improve the quality of substrate culture as crop cultivation growing medium. Meanwhile, potential nanotechnology applications in soilless and microgreen farming include: (1) Plant trait improvement against environmental disease and stress through nanomaterial application; (2) plant nanobionics to alter or improve the function of the plant tissue or organelle; and (3) extending the shelf life of microgreens by impregnating nanoparticles on the packaging or other preservation method

Simulation of PSO-PI controller of DC motor in Micro-EDM System for biomedical application

An Electrical Discharge Machining is one off the non-traditional machining processes. It is now b been used widely in many applications due to its ability to machine maaterials with good surface finish. This paper presenteed a new Micro-Electrical Discharge Machining controller model using Particle Swarm Optimization algorithm for efficient ssearch and optimization of Proportional-Integral controller parameters in order to achieve a better positioning system especially in biomedical application. This control method was simula ated using MATLAB/SIMULINK to control DC moto or. From the simulation, it was found that the proposed method gives be etter performance with improved step response for pre ecise positioning system in micro-EDM as the settling time and overshoo ot are reduced.^

Influence of dimple depth on lubricant thickness in elastohydrodynamic lubrication for metallic hip implants using fluid structure interaction (FSI) approach

Introduction: The lubricant thickness in clearance between bearing surfaces for metallic hip implants are currently incapable of accommodating the motion experienced (high load and low entraining motion) in hip walking cycle. Thus, micro-dimpled surfaces were introduced onto surfaces of metallic acetabular cups to improve lubricant thickness. Micro-dimpled surface is a method of advanced surface improvement to increase the lubricant thickness in various tribological applications, such as hip implants. However, the application of micro-dimpled surfaces in hip implants has not yet been explored adequately. Therefore, this study aims to identify the influence of micro-dimpled depth on lubricant thickness elastohydrodynamically for metallic hip implants using Fluid-Structure Interaction (FSI) approach. Methods: Fluid-Structure Interaction (FSI) approach is an alternative method for analysing characteristics of lubrication in hip implant. Dimples of radius 0.25 mm and various depths of 5ìm, 45ìm and 100ìm were applied on the cup surfaces. The vertical load in z-direction and rotation velocity around y-axes representing the average load and flexion-extension (FE) velocity of hip joint in normal walking were applied on Elastohydrodynamic lubrication (EHL) model. Results: The metallic hip implants with micro-dimpled surfaces provided enhanced lubricant thickness, namely by 6%, compared to non-dimpled surfaces. Furthermore, it was suggested that the shallow depth of micro-dimpled surfaces contributed to the enhancement of lubricant thickness. Conclusion: Micro-dimpled surfaces application was effective to improve tribological performances, especially in increasing lubricant thickness for metallic hip implants