The Dc Motor Speed Control Methods Engineering Essay

The Dc Motor Speed Control Methods Engineering Essay ABSTRACT This paper describes the Matlab and simulink converts into actuality of the DC motor speed control methods, namely field resistance, armature resistance control methods and armature voltage, and feedback control system for DC motor drives and this paper describes mathematical modelling, simulation of DC motor system using computer simulations Matlab and simulink, by this system response to change various parameters like system stability, disturbances, analysis and optimization of model parameters with respect to the quality of control. If simulation techniques are used for determining the control parameters a simulation model is necessary, which has to be constructed from the analytical model. INTRODUCTION DC Motor is an electrical motor and it most commonly used in an electrical device for easy to drive the instruments, steel rolling mills, electric cranes, and robotic manipulators due to precise, wide, simple, and continuous control characteristics. To control the speed of low power DC Motor rheostatic armature control method were used. The basic parts of the DC motor are- axle, rotor (armature), stator, commutator, field magnet, and brushes. In the geometry of brushes, commutator contacts, and rotor windings are arranged in such a manner so that when power is applied then polarities of the energized winding and the stator magnets are misaligned and the rotor will start to rotate until it is almost aligned with the stators field magnets. When the rotor reaches to alignment, the brushes move to next commutator contacts, and energize the next winding. There are variable types of DC Motor available in market with the good and bad qualities. Bad quality means lag in efficiency. To recover or stop this kind efficiency problem controller is introduce in the system. Brushed DC motors are most widely used in applications and its ranging from toys to push-button adjustable car seats. Brushed DC (BDC) motors are inexpensive but easy to drive. Brushed DC motors are easily available in all size and shape with the wide range from large-scale industrial models to small motors for light applications (such as 12 V DC motors). . BDC motors are most commonly used in easy to drive, with variable speed and high start-up torque applications. OBJECTIVE The Fig.1 shows the analogues electrical circuit. MODELLING The circuit which was given is drawn in the Matlab by using simulink. In the circuit diagram the flow of current BLOCK DIAGRAM Figure shows the block diagram of DC motor TRANSFER FUNCTION K/{(Ls+R)(Js+f)+K2}  Ã‚ ± 1/s Vapp Fig 4.1. Transfer Function STATE SPACE MODEL As we know that, V- .†¦. (1) †¦.. (2) Substituting equation (2) in (1) †¦. (3) .†¦ (4) †¦Ã¢â‚¬ ¦. (5) Substituting (5) in (4) †¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦ (6) Differentiating (6), we get †¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦.. (7) Putting (3) in (7), we get †¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦ (8) Now †¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦ (9) Substituting (9) in (8), we get We know that x=Ax + Bu Y=Cx + Du X= The State Space Model represents by the linear equation and it is written as. x= Ax + Bu y = Cx + Du Below figure shows the state space model (Calculation is in appendix) Figure 5.1 State Space Model PHYSICAL SYSTEM Consider a DC Motor, in this electrical circuit of the armature and free body diagram of rotor are shown in figure below. http://zone.ni.com/cms/images/devzone/tut/mpm-2-motor1.gif Fixture: DC Motor is a common actuator in control systems. Brushed DC Motor fundamentals A Brushed DC Motor consists of stationary fixed permanent magnets i.e. stator, a rotating electromagnetic i.e. rotor and flux, which is concentrated by metal. Rotor rotate by the attraction of the opposite poles and repulsion of the like poles, it cause to generate torque and torque acts on rotor and then make it turn. As the rotor start to rotate or turn then fixed brushes make and breaks the contact in such a way that with the rotating segments (commutation). The rotor coil of the brushed motor energized and de-energized in such a way so that the rotor start to turns. By transferring the power to the motor, current generate in rotor coils and therefore the north and south poles are reversed and because of the motor change the direction. From the Strength of the magnetic field, speed and torque of the motor depend Figure (1) Brushed DC Motor PRINCIPLE OPERATION Construction and operation of the Brushed DC Motor is shown below in figure (2).for the construction of the BDC motor always the same components are required i.e. Stator, rotor, commutator and brush. Figure (2) Simple two-pole brushed DC Motor Stator The rotor surrounded by the stationary magnetic field which is generated by the stator and this filed is generated by the permanent magnet or electromagnetic winding. On the construction of the stator, different types of BDC distinguish. Rotor Rotor is also known as an armature and it is made up of one or more windings. Magnetic field is produce when they energized. When the opposite pole of the magnetic poles, attract to each other which is generated by the stator, and causing the rotor to turns. The opposite poles are always attracting to each other. As the motor turns, the windings are being constantly energized. This deviation of the field in the rotor is called as an armature. Brushes and commutator There is no requirement of controller in BDC to switch current in motor winding. The commutation winding of the BDC motor is done mechanically. Reside on the axel of rotor there is a segmented copper sleeves called commutator. Carbon brushes slides over the commutator coming in a contact with the different segments of the commutator as the motor starts to turn. When the voltage is applied across the brushes of the motor then dynamic magnetic field is generated inside the motor. Brushes and commutator are the most important parts of the BDC motor that are most prone to wear because they are the sliding part to each other. SPEED CONTROL The Speed of a DC Motor is directly proportional to the voltage. By using the digital controller voltage can be control and to generate the average voltage pulse-width modulated (PWM) signal is used. In motor there is a motor winding which acts as a low pass filter so PWM develop a suitable current in the motor winding. ADVANTAGES Cheap in price because low cost of construction. Extend a life by replacing a brush. Inexpensive motor and simple control. Speed/Torque is normal at high speed. On fixed speed no control is required, Controller is required only at variable speed in this condition same controller can be used. DISADVANTAGES Maintenance is required for brushed DC Motor because of brush. If the brush friction increases, reduce the useful torque. Heat dissipation is poor because of internal rotor construction. Speed range is limited because of the mechanical limitation on brushes. Life is also shorter. Noise is generated due to brush. Application examples: moving toys, fans, printers, robots, electric bikes, -doors, -windows, -sun roofs, -seats, mixers, food processors, can openers, blenders, vacuum cleaners, toothbrushes, razors, coffee grinders, etc. Physical Parameters Moment of inertia of the motor (J) = 9.89 E-7 kg Nm s/rad Damping ratio of the mechanical system (b) = 5.84E-7 Nm s/rad Electromotive force or motor constant (K=Ke=Kt) = 0.008 Nm/-w Electric resistance (R) = 0.80 ohms Electric inductance (L) = 0.00041H Friction coefficient, f Input (V): Source Voltage Output (theta): position of shaft the rotor and shaft are assumed to be rigid CONCLUSION Brushed DC motors are very simple to use and easy to control, which makes them a short design-in item. PIC microcontrollers, especially those with CCP or ECCP modules are ideally suited for driving BDC motors. Refference Circuit Diagram for DC Motor Control by A. Collins http://www.nxp.com/documents/application_note/AN10513.pdf http://ww1.microchip.com/downloads/en/AppNotes/00905a.pdf http://www.orientalmotor.com/MotionControl101/AC-brushless-brushed-motors.html http://ww1.microchip.com/downloads/en/AppNotes/00885a.pdf http://www.dynetic.com/brushless%20vs%20brushed.htm file:///D:/matlab/index.php.htm

The Women of Umuofia in Chinua Achebes Things Fall Apart Essay

The Women of Umuofia in Chinua Achebe's Things Fall Apart    The only women respected in Umuofia are those like Chielo, the priestess of the Oracle of the Hills and Caves, who is removed from the pale of normalcy. Clothed in the mystic mantle of the divinity she serves, Chielo transforms from the ordinary; she can reprimand Okonkwo and even scream curses at him: "Beware of exchanging words with Agbala [the name of the Oracle of the Hills and Caves]. Does a man speak when a God speaks? Beware!" (95). Yet if Okonkwo is powerless before a goddess's priestess, he can, at least, control his own women. So, when Nwoye's mother asks if Ikemefuna will be staying long with them, Okonkwo bellows to her: "Do what you are told woman. When did you become one of the ndichie [clan elders]?" (18).   Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚   Perhaps Umuofia's shabby and degrading treatment of women and wives stems from unconscious fear of, rather than reverence for, the ubiquitous and capricious Earth goddess Ani or Ala, who wreaks such havoc on the townspeople s lives. She is the goddess of fertility. She also gives or withholds children; she spurns twin children who must be thrown away; she prohibits anyone inflicted with shameful diseases from burial in her soil. To the men of Umuofia, she must seem the embodiment of the two-faced Greek furies and Scylla and Charybdis joined together -- vengeful, unavoidable, and incomprehensible. Umuofia s men can compare to the ancient Greeks who were noted for similar female images such as Pandora, Circe, Medea, and Clytemnestra. In helpless, mortal dread of a fearsome divine female principle, they come down heavily indeed on ordinary women whose lives they can control as they like.   Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚   A cursory look at the place o... ...e African Novel: Essays in Analysis. London: Saros International, 1992. pages Nwapa, Flora.   Efuru.   London: Heinemann, 1966. ---.   Idu.   London: Heinemann, 1970. Ogunyemi, Chikwenye Okonjo.   "Women and Nigerian Literature." Perspectives on Nigerian Literature. Vol. 1.   Lagos, Nigeria: Guardian Books, 1988.   pages Okonkwo, Juliet.   "The Talented Woman in African Literature." African Quarterly 15.1-2: pages. Rich, Adrienne.   Of Woman Born: Motherhood as Experience and Institution.   New York: Norton, 1976. Thiong o, Ngugi   wa.   Petals of Blood.   London: Heinemann, 1977. ---.   Devil on the Cross.   London: Heinemann, 1982.   Walker, Alice.   "In Search of Our Mothers' Gardens." In Search of Our Mothers   Gardens: Womanist Prose. New York: Harcourt  Ã‚  Ã‚  Ã‚  Ã‚     Ã‚  Ã‚  Ã‚   Brace, 1983.   231-243. Weinstock, Donald, and Cathy Ramadan.  

Equality and Diversity Essay

I am writing a reflective account on how my personal beliefs and experience’s influenced my professional interaction with various groups and individuals. For example my first job in the care industry was working at a nursing home for residents with all forms of Alzheimer’s. I had never done this type of work before, so my first day for me was both a new experience and environment. I had never dealt with people who have a communication barrier, where they could not express their emotions. see more:champion equality diversity and inclusion Before having worked in the care home, and not having any knowledge on Alzheimer’s, I would have categorised them all in the same box, i. . all being the same as opposed to possibly having different stages and levels of Alzheimer’s. I also found it hard to grasp and understand how you could forget the basic aspects of what we do in everyday life i. e. eating, drinking and remembering your own name. I therefor found it hard to communicate and engage with them, as I did not understand their condition. Prior to working with Alzheimer’s patients I had never come across somebody who, not only had Alzheimer’s, but in addition was hard of hearing and/or partially sighted. I found this difficult at first because I didn’t know how to interact with them. I overcame this by learning to understand each one of their characteristics, by the way they spoke, mannerisms, their body language and by getting to know them as an individual. I learnt how I could interact with them on a one to one level and ascertain their needs and requirements. Alzheimer’s patients need a certain level of care, therefore I undertook training that was offered by my place of employment. This included a person first and dementia second course which explained how the resident should always come before the dementia and how their best interests should always be taken into account as a first priority. In addition I undertook a course on palliative care. This taught me how to care for somebody who was in their finally stages of dementia ,in terms of assisting them, improving their quality of life and by providing increased comfort by promoting their dignity towards the end of their life. I also took a course in movement and handling where I learnt how to manoeuvre my residents in a safe manner by either using sliding sheets or hoisting equipment, these techniques helped me to assist them with as little discomfort as possible. Some of our residents are unable o communicate with us and are unable to express feelings of discomfort or pain, so this course was beneficial to me because it provided a safe way for me to move my residents with ease. If i was to continue exclusively in this line of nursing, I could do NVQ courses in health and social care with my place or of work, and attend courses they provide for me. If I wanted to further my career I could potentially go onto university and train to be a mental health nurse. This will enable me to be more aware of how this disease can start and what’s involved in the long term. Following Gibbs framework on reflection (1998) stage 5; I conclude from this experience that I have gained more patience with others by understanding their different needs. I have learnt how to communicate on different levels, with residents, family members, colleagues and senior professionals i. e. doctors and nurses which I struggled with initially. I have become more compassionate as a result of dealing with the end of life process, so my personal beliefs or thought process will not influence my professional interaction with dementia patience because I have gained a better understanding of their condition.

Friendship - 1725 Words

Q1) what do you think of the company guiding principles? Describe how the company’s guiding principles would influence how a barista at a local Starbucks store does his or her job. How these principle would influence how one of the company s top executives does his or her job. Answer: Starbucks guiding principle clearly describes the mission and purpose of Starbucks existence. They describe that Starbucks is not just selling Coffee and earning profit, Starbucks is all about providing people with a second place between their home and work where they can enjoy quality coffee and a sense of community life. It is a place where the employees are not just employees but defined as Partners in business. Every partner of the company understands†¦show more content†¦Q3) what has made Starbucks culture what it is? How is that culture maintained? Answer: The culture of Starbucks is a combination of written and unwritten values, beliefs and codes of behavior which influence employees to perform their duties and the way they behave with people (employees amp; customers) in the organization. The culture of Starbucks is greatly influence by the three founders of Starbucks amp; Howard Schultz, their mission, vision and their values as coffee business was their passion. Its culture encourages innovation and risk taking is less aggressive, predicatively stable and highly customer oriented. Starbuck treat employees as their partners and employees are also given training for 24 hours, to properly educate them about Starbucks guiding principles and ethical codes, when they join Starbucks initially and this practice has become part of their culture. Starbucks maintained their culture by: * Communicating their culture to their employees (partners). * The behavior of top management clearly reflects the beliefs and values of the founders, their ethical values and communal beliefs and sets examples for the employees * Keeping track of employees consistent with organization culture. * When new recruitment takes place those people is given preference whoShow MoreRelatedFriendships : Friendships And Friendships896 Words   |  4 PagesFriendships Marlene Dietrich once said, â€Å"It is the friends that you can call at four a.m. that matter.† There are many different types of friendships. Casual friendships, opposite-sex friendships, and long term friendships are all examples of the different and common types of friendships used today. Casual friends are those you can text and hangout with every once in a while, without any sort of attachment. 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