ELG4112 Electromechanical Systems and Mechatronics 1
Introduction Based on Electromechanical Systems, Electric Machines, and Applied Mechatronics Electromechanical systems integrate the following: Electromechanical motion devices (actuators and sensors) Transducers (analog and digital) Power Electronics and Converters Controllers (analog and digital) Data Acquisition Systems The term mechatronics is used to denote a rapidly developing, interdisciplinary field of engineering based on a concurrent integrated concept, and used to perform analysis and design, optimization and control, implementation and deployment of electromechanical systems. It deals with the design of products whose function relies on the integration of mechanical and electronic components coordinated by a control architecture. 2
Electromechanics Actuators/Sensors Electrical Engineering Mechanical Engineering Analysis/ Electronics Mechatronics (Intelligent Electro-Mechanical Systems) Modeling Computer/Software Engineering 3
Mechatronics Main Elements Simulation and Modeling + Automatic Control + Optimization + Actuators D/A Mechanical Systems Electrical Systems Computer Systems Sensors A/D Electromechanical Real Time Interfacing 4
Mechanical Systems Most mechatronic applications involve rigid-body systems, and the study of such systems relies on the following laws: Newtons s First Law: If the resultant force acting on a body is zero, then the body will remain at rest if originally was at rest or will move with constant speed in a straight line if originally in motion. Newton s Second Law: If the force acting on a body is not zero, then the body will have an acceleration proportional to the magnitude of the force. Newton s Third Law: The forces of action and reaction between bodies in contact have the same magnitude, line of action, and opposite sense. Newton s Law of Gravitation: Two bodies are attracted with equal and opposite forces and inversely proportional to the distance between them. Parallelogram Law: Two forces acting on a body may be replaced by a single resultant force obtained by drawing the diagonal of the parallelogram with sides equal to each of the two forces. Principle of Transmissibility: The equilibrium or motion of a rigid body remains unchanged if a force acting at a given point is replaced by a force of the same magnitude and direction but acting at a different point, provided that the two forces have the same line of action. 5
Electrical Systems The following electrical components are found in mechatronic applications: Motors and generators Sensors and actuators (transducers) Solid state devices Circuits (signal processing and conditioning; impedance matching; and amplifiers) Contact devices (relays; circuit breakers; switches; slip rings; fuses; and others Also mechatronic requires full understanding of DC and AC analysis Kirchhoff s voltage law (KVL) Kirchhoff s current law (KCL) Phasors Natural and forced response 6
Additionally We need Computer systems Sensors and actuators Sensors are required to monitor the performance of machines and processes. Sensing systems may be used to assess operations, inspect work, and identify parts and tools. These devices measure physical variables such as temperature, pressure, speed, force, torque, and acceleration. Actuators are another important component in mechatronic systems. Actuation means physical acting on the process. Actuators are usually electrical, mechanical, fluid power or pneumatic based. They transform electrical inputs into mechanical outputs such as force, angle, and position. Actuators may be Electromagnetic actuators (AC and DC motors, stepper motors, electromagnets) Fluid power actuators (hydraulics, pneumatics) Unconventional actuators (piezoelectric, for example) 7
Real Time Interfacing The main reason for the real-time interface is to provide data acquisition and control functions for the computer. The purpose of the acquisition function is to reconstruct a sensor waveform as a digital sequence and make it available to the computer software for processing. There are two types of real-time interface: external and internal bus systems. An internal bus system is computer specific and consists of a board, which plugs into the internal computer bus. The external bus system is computer independent system which is connected to the host computer through its serial port. This type of system is slow compared with the internal type. 8
Basic Foundations Mathematics: Basic principles of classical mathematics for computation of electrodynamic fields and its analogies in physics: Vector analysis with grad; div; curl; Laplace transform; and more! Mechanics: Motion of systems with the corresponding analysis of forces that cause motion. This is accomplished through the application of Newton s second law of motion, the net force (the vector sum of all forces) on an object of mass m is related to its acceleration vector: In the equation, m is the mass in kilogram (kg) of the body and a is the acceleration in meters per second square (m/s 2 ). Electromagnetics: Field theory; Maxwell equations in differential and integral form for wave applications; F = F = m a F 0 (a body is at equilibrium) q1q2 4πε x = 2 0 a x 9
Free Body Diagrams Creating the free body diagram is important step in the solution of problems in engineering mechanics. Any structure (or part of a structure) so defined may be characterized as a free-body diagram (FBD). The freebody diagram shows all the external loads acting on the FBD; all the unknown external moments or forces at the points where the FBD is connected to other structural elements (for example the reactions); and all the unknown internal moments or forces at points where a FBD is sectioned. If the free body diagram is completed, the unknown forces can be solved by using the equations of equilibrium. These are a set of equations, derived directly from Newton s second law. These equations state that the sum of forces in a system that is in static equilibrium must be zero. For a two dimensional system, the summation of forces in x- and y-axes equals to zero. 10
Mechanics Mechanics may be defined as a branch of the physics that deals with the state of bodies at rest or motion when subjected to action of forces. Generally, this subject is subdivided into three branches: rigid-body mechanics, deformable-body mechanics, and fluid mechanics. Rigidbody mechanics (known as engineering mechanics) is divided into two areas: static and dynamic. Static deals with the equilibrium of bodies, which are either at rest or move with constant velocity. However, dynamic is concerned with the accelerated motion of bodies. Although static might be considered as a special case of dynamics, in which the acceleration is zero, static deserves a particular handling in engineering education since many objects are designed with the desire that they remain in equilibrium. 11
Mechanics The study of the motion of systems with the corresponding analysis of forces that cause motion is of interest. Newtons s second in terms of the linear momentum, which is found as p = mv, is given by, where v is the vector of the object velocity. F = d p dt = d mv dt For rotational motion, the net torque and angular acceleration must be used. In particular the torque vector T T = r F The rotational analog of Newton s second law for a rigid body is, J is the moment of inertia (rotational inertia), α is the angular acceleration vector - T = J α 12
Electromagnetics Wherever electricity is generated, transmitted, distributed, or used, electric and magnetic fields are created, often at significant intensities, due to the presence and motion of electric charges. These artificial fields are generally seen around electric utilities, telecommunication facilities, consumer appliances, industrial and medical equipment, and other common sources. Fields also occur in nature, as in lightning, and in other phenomena such as the northern lights caused by the interaction of solar wind and the earth s magnetic field. Usually, electric and magnetic fields cannot be seen or felt, but they can be measured. Surrounding any wire or conductor that carries electricity, there exists both electric and magnetic fields. These fields often extend for substantial distances around the wire. Today, many man-made sources generate electric and magnetic energy as collective energy in the form of EM waves. These waves consist of oscillating electric and magnetic fields, which may interact differently with matters including biological materials. 13
Electric Fields E, also called electric field intensity, denotes electric field. Electric field exists whenever electric charges are present, which means, whenever electricity is in operation, or when positive and negative charges are separated. The potential difference due to this separation is called voltage. The voltage means work measured in joules per coulomb (J/C) needed to move a unit of electric charge between two points. It may be defined by the electric potential difference between two points. The voltage increases as more charges are separated; however, greater energy is released when the charges come together again. E fields are intensified by increasing the potential difference or by moving the opposing charges closer together. 14
Magnetic Fields The E field was explained by means of force between charges that act on a line between the charges. With the movement of charges, another kind of force on one another is exerted along the line between the charges. This force stands for the magnetic field intensity, denoted as H, which is a vector quantity created due to moving charges in free space or within conductors. Magnetic fields run perpendicular to the electric current. This means, while electric current runs in a straight line, magnetic fields surround the line in a circular fashion. They control the motion of moving charges. The unit of magnetic field is amperes per meter (A/m). If we have direct current (DC), the magnetic field will be steady, like that of a permanent magnet. If we have AC, the magnetic field will fluctuate at the same frequency as the E field; it becomes an EM field, because it contains both E and H fields. 15
Electromagnetic Induction In 1831, Michael Faraday in London found that a magnetic field could produce current in a closed circuit when the magnetic flux linking the circuit is changing. This phenomenon is known as electromagnetic induction. Faraday concluded from his experiment that the induced current was proportional, not to the magnetic flux itself, but to its rate of change. dψ dφ E induced = = N dt dt Ψ is the flux linkage Φ is the magnetic flux Φ = ε E 16
On Mathematical Modeling and Simulation In mathematical modeling, we try to establish functional relationships between entities which are important. A model imitates or reproduces certain characteristics of the actual-possibly on different scale. Any modeling task requires formulation of mathematical models suitable for computer simulation. Simulation is a technique that involves setting up a model of a real situation and performing experiments on the model. Or in other words, simulation is the process of solving any block diagram model on a computer Mathematical models may be classified in many ways: Linear or nonlinear Lumped or distributed parameters Static or dynamic Continuous or discrete. Modeling and simulation have important uses. They are good in situations where the actual system does not exist or is too expensive, or hazardous to build. 17