Maulana Azad National Institute of Technology Bhopal-462051

Dept. of Mechanical Engineering

Assignment OnElectrical Discharge Machining (EDM)

Subject- Advanced Production EngineeringBy

Mohit Chetwani and Palash SahuScholar No – 111116044, 45

VIIth Semester, 4th Year

Introduction

Purpose of the project is to perform certain modifications in our previously undertaken project that was to make a simulation of the system and develop controls for the Self Balancing Robot. In this project we will be actually constructing one such model of our robot using an extra wheel in place of costly gyroscopes for the purpose of balancing our robot which will save the cost and will increase the stability of the robot.

Project-Aim

With the constantly increasing need for mobility, particularly in urban areas, various problems arise including the urban space and energy consumption. In addition, exhaust and noise emissions have to be mentioned. In order to be able to satisfy the mobility needs in the future, new solutions are required. The project aims at improving urban transport, whilst minimizing the negative environmental impacts caused by increased mobility. Therefore, it is necessary to develop new concepts for individual urban transport to close the gap between conventional individual transport and public transport.

ABSTRACT

Electrical discharge machining (EDM) is one of the earliest non-traditional machining processes. EDM process is based on thermoelectric energy between the work piece and an electrode. Material removal rate (MRR) is an important performance measure in EDM process. Since long, EDM researchers have explored a number of ways to improve and optimize the MRR including some unique experimental concepts that depart from the traditional EDM sparking phenomenon. Despite a range of different approaches, all the research work in this area shares the same objectives of achieving more efficient material removal coupled with a reduction in tool wear and improved surface quality. In the end of the assignment scope for future research work has been outlined.

INTRODUCTION

Electrical discharge machining is basically a non-conventional material removal process which is widely used to produce dies, punches and moulds, finishing parts for aerospace and automotive industry, and surgical components [1]. This process can be successfully employed to machine electrically conductive parts irrespective of their hardness, shape and toughness [2-4].

INTRODUCTION

INTRODUCTION

Electrical discharge machining is basically a non-conventional material removal process which is widely used to produce dies, punches and moulds, finishing parts for aerospace and automotive industry, and surgical components [1]. This process can be successfully employed to machine electrically conductive parts irrespective of their hardness, shape and toughness [2-4].

Working Principle of EDMThe working principle of EDM process is based on the thermoelectric energy. This energy is created between a workpiece and an electrode submerged in a dielectric fluid with the passage of electric current. The workpiece and the electrode are separated by a specific small gap called spark gap. Pulsed arc discharges occur in this gap filled with an insulating medium, preferably a dielectric liquid like hydrocarbon oil or de-ionized (de-mineralized) water [5-8]. Schumacher [9] described the technique of material erosion employed in EDM as still arguable. This is because ignition of electrical discharges in a dirty, liquid filled gap, when applying EDM, is mostly interpreted as ion action identical as found by physical research of discharges in air or in vacuum as well as with investigations on the breakthrough strength of insulating hydrocarbon liquids.

Inverted pendulum & Two Wheeled Robots

Inverted pendulum is commonly described as a pendulum or a rigid rod with bob on one end mounted by a hinge to a cart which can be translated along a track by an input force. The pendulum itself however is not actuated it is free to swing about its point of marginal stability in vertical position only by properly actuating the cart and using the reaction force of pendulum against the cart can the pendulum be positioned.

In this feature lies the significance of inverted pendulum. It is an indirectly actuated system that is the object of interest the pendulum can be controlled only by exerting a force on the secondary object the cart. The nobility and challenges of such a controller in real world has attracted attention from many partiesperhaps because of fame of segway two wheeled balancing robot has became a prominent project for students it is certainly a topic of interest to anyone involved in the study of control system and there application to robotic.

Literature review

• Despite of the many studies on self balancing human transporter, only few studies addressed the modelling of human transporter, but the interest is on the rise. Mi-Ching Tsai, Jia-Sheng Hu, Feng-Rung Hub employs a PI observer to detect abnormal information in an auto-balancing two-wheeled cart caused by actuator faults and steering load torques. Analysis and design of the PI observer are then discussed in detail. They Verified that It has been verified that the proposed control system has benefits such as detecting possible failures of the ABTWC. The experimental results have substantiated that the proposed fault diagnosis strategy has the ability, in practice, to improve the ABTWC’s safety.

• Ronald Ping Man Chan , Karl A. Stol, C. Roger Halkyard found that

there has been much more research in two-wheeled robots which actively stabilize themselves. Various models and controllers have been applied both to explain and control the dynamics of two-wheeled robots. We explore the methods which have been investigated and the controllers which have been used, first for balancing and movement of two-wheeled robots on flat terrain, then for two wheeled robots in other situations, where terrain may not be flat.

They got the result that A number of controllers have also been applied to the two wheeled robot, showing varying performance. However, it is quite clear that simple linear controllers can effectively control the two wheeled robot, even for a largely un-modelled system.

Methodology

1. Derived the governing equation of motion of inverted pendulum by using elementary mechanics

2. By using an appropriate control technique, like PD(proportional derivative) control, we have determined the control input (Force on the cart) as a function of control output (angle of tilt).

3. Applying the above technique to a Segway using Autodesk motion analysis. Proper assumptions have to be taken while doing this.

4. Choosing appropriate sensors to measure control output (angle of tilt) of the system. (accelerometer & gyroscope)

5. Determining the control strategy for turning.

Principle of Self balancing inverted Pendulum

Equations of Motion & Control Techniques

Parts & Components of a Three Wheeled

Robot:-

Handlebar/Controls/User Interface

Chassis

Permanent-magnet brushed DC motor

Microcontroller (CPU)

Power source (Multiple rechargeable Lithium-Ion batteries)

Wheels etc.

The system consists of dual motor controllers and motors, one for each rear wheel. The drive system and electrical system are activated by a "power key," similar to an automobile's "ignition" key.

Motors• Each rear wheel is independently driven by a high-speed

brushless electric • Motor that is quiet, efficient, and does not require periodic

maintenance to replace consumable parts. Each Motor is microprocessor controlled to precisely regulate drive motion.

Drive/Electrical System

3-D Model of the Human Transporter

Created using Autodesk 3ds Max 2013

Introduction to PID Control

This introduction will show you the characteristics of the each of proportional (P), the integral (I), and the derivative (D) controls, and how to use them to obtain a desired response. In this, we will consider the following unity feedback system:

Plant: A system to be controlled Controller: Provides the excitation for the plant; Designed to control the

overall system behavior

PID controller generates the following responses to change

Inverted Pendulum TechniqueThis human transporter is built to stay balanced in one place (balancing of IP)

Changes from the balanced state are first detected (in terms of tilt angle)

Signals are then passed to a PID controller

The PID controller then directs the motors to regain the balance

the feedback is sent to controller again to detect any further changes from the balanced state

Graphical results obtained using MATLAB

Explanation-

The above graph is the initial condition of the pendulum when we are not using PID controller. Graph shows that as the time increases the angle with vertical also increases continuously and after some time pendulum will lay down or on the floor thin means the angle with the vertical become 90 degree.This is the case of pendulum alone in the cart without control unit. Now our aim is to control the movement of cart by balancing the pendulum. For these we uses PID controller and for that the basic equation has been derived and then converted to the Laplse form and then with the help of MATLAB software we plotted the graph between angle of twist and variation in velocity for balancing it with respect to time. The variation is shown in below graph and important conclusion taken from the graph.

Graphical results obtained using MATLAB

Explanation-

The Above graph shows the variation in pitch angle with the use of PID control. It is clear from the graph that pendulum will come in balance position after some time (for this 0.5 sec) as it is tilted slightly. And at the same time when we look into the graph of variation of velocity with time.It shows that for balancing the pendulum cart initially moves forward with fast rate and as the angle decreases velocity also decreases and comes to constant position. Now from these two graph it is understood that as we tilt the pendulum for certain angle, the cart will move in the same direction for balancing the pendulum.

Graphical results obtained using MATLAB

Conclusion

• The variation in pitch angle with the use of PID control. It is clear from the graph that pendulum will come in balance position after some time (for this 0.5 sec) as it is tilted slightly. And at the same time when we look into the graph of variation of velocity with time.

• It shows that for balancing the pendulum cart initially moves forward with fast rate and as the angle decreases velocity also decreases and comes to constant position. Now from these two graph it is understood that as we tilt the pendulum for certain angle, the cart will move in the same direction for balancing the pendulum.

• Since control of Segway was successfully achieved using Autodesk, a small scale prototype of the same could be manufactured as per the above CAD model.