1) Background of the Alibaba
Alibaba is an e-commerce company from china. Alibaba was the biggest IPO in the world. The founder of the company is jack ma and penh Lei. This company set up on since 1999 and since 2001 they start to earning profit. In 2012 alibaba group handle sale of 170 bilion.

Nowadays, Alibaba company is successful than Ebay and Amazon. In 2003, Alibaba found taobao as direct to competition to Ebay. In the year of 2004, Alibaba group ofer Alipay. Alipay give customer to receiver good before payment was released to the sellers.

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Before that, in july 2011 the group initiate a mobile operating system and develop by their cloud computing system. Jack ma was CEO of the group till 2013, because lack of technical knowledge, Jack ma never a typical CEO. Now have the one of the person, he is the main pillar of Alibaba. The present CEO is Jonathan Lu.

In September of 2014, Alibaba is the first time took the US markets by the storm. Then, It propelled the founder Jack Ma to became a richest man in the china. In 2013, have 231 million of customer spent the sum of 2480 billion on the Alibaba web portals. And the more sale than ebay and amazon combined. Jonathan Lu attribute the success to the customer. Therefore, service the customer in their company be a important thing.

Lastly, the Alibaba of the successful are inspiring to several internet business all over the world. So a company need to be successful, persistence is victory.

In the first, The Alibaba company have say the mission make them successful in the
company in the world, so the mission is to make it easy to do business anywhere and can
communication with different type people of business. After that, The Alibaba company have
operation leading online and mobile markets in the retail and wholesale sectors. Alibaba have
provide technology, usage, payment platforms and implementation to enable consumers and
businesses to conduct business activities in the most convenient and reliable manner.

In Alibaba the first vision is became the first platform to share data and become a company
with at least 102 years of happiest people. After that, Alibaba company prepare to solve the
challenges of small businesses in procurement, sales and marketing, management and
financing through information technology. Therefore, The Alibaba have say that the goal is
to became a pioneer in the global trade revolution. Then, Alibaba envisage to their unique
team will establish the future business infrastructure and serve their customers in the three
different centuries.
Service offered
The Alibaba company have make many of offer to the people to start their business life in
there. The first is the company of Alibaba have provided the people to get free register in
one year, and the people can start the business to sell the thing they want and also the
customer need. Before that, when the seller wants to start a business but does not know what
to do, so the Alibaba company have think of this solution is was provide the skill to let the
people to learn in step by step before to start a business or half sell the product and half learn
same as like training. After that, The Alibaba company have provided the service of
e-commerce learning to the people who was interested to be suppliers or need to understand
about the global suppliers, And the Alibaba company has separate different level of e-
commerce to let the people have more understanding and the people can know what level you
understand in the learning. Example, Basic of E-commerce, Basic of foreign trade and
industry analysis. Therefore, The Alibaba have provided membership package to the seller
and let the seller have continue to their business, and Alibaba like the seller can be success in
the business and can let the customer buying their product can feel more satisfaction.

Critical success factor
Unique Business Model
The first, Alibaba have mainly provided service to small businesses and individuals. This
provides a unique business opportunity for liberating the productivity of small businesses and
provides consumer with more diversified spending options. After that, in 1688 in B2B e-
commerce platform, Taobao or e-Tac in China’s largest professional import and export agent,
Alibaba’s the three core of important businesses are focused on providing services for small
businesses and accumulate value that cannot be create individually. And the Alibaba need to
represent a complete e-commerce ecosystem. Therefore, more focusing on small businesses,
the various target consumer of groups can have a variety of good. In 2014, the total of
transaction of Alibaba platform, is reach 2.3billion yuan is 330 billion euros, 340 million US
Reliable credit model
Into the first, Alibaba is good to credit model to helps build a trustworthy reputation among its
costumers. All the seller in the e-commerce platform need to required and pass through the
online certification tests to verify their identity information. This action can decrease illegal
trades because seller are always supervised on the platform. After that, The record of the
transactions can be traced back by the seller and the customer. Therefore, this action can
protects the legitimacy of each transaction and helps customers choose more reliable sellers.
Thus, The function of the Alipay have make the most of people receive the good product from
the seller because the protected is good. And the use of the Alipay is reached 300 million and
the number of transaction reached 900 billion euros is 1280 billion euros, 135 billion US dollars.
So the number of active users of mobile terminals reached 100 million more than the number
of paypal user. In addition, This system have receive the people feedback highly encouraged.
Then, the customer can have the discount coupons when they get feedback to the system. This
action is reducing post-purchase regret.

Unconventional Profit Model
The first, the Alibaba have charge for marketing and technical support services, not admission fees. This action can improve the largest market of loyal customers. Before that, The Alibaba of profit is come from the advertising and the keyword bidding, and the account of total profit is 57%. The second largest of profit is 25%is come from the technical service and also based on consumer behaviour in big data. Thus, the Alibaba have give the free register and also let the people learn trading in online, and ebay china charge fees for its platform transactions. To collect many of sellers, Taobao is success to attracted more customer. In addition, The total of people register in Alibaba platform have 500million people. And also including 230 million active buyers more than 8 million if seller, and the annual orders exceeding 11 billion. Alibaba can use the advertising, keyword bidding and the customer data to make money.
Support customer satisfaction services
In the first, Alibaba service provide a comfortable shopping environment and a positive onlone customer experience, and also increase the user engagement. Before that, Alibaba have provides a good set of support service to ensure optimal customer satisfaction by helping sellers to maintain positive interaction for sellers. In the support service have including online business training for sellers, introducing specialized coding system to manage the large number of stores on the platform, development the good of messaging tools to achieve better communication between buyer and seller and the product must be refunds in 7 days. In addition, these support service can help generate more transactions.
Implemented Fun Culture At Work, Rather Than Hard Work
The first, Ma Yun is not a performance –oriented person. And he does not believe in digital games. He believes the business is a part of life. He never forces the employees to achieve goals. And he is focus on funny culture at work. He always freedom to share knowledge of employees and listen to their suggestions and opinions. Thus, In his opinion. The first is try to think of customer, Into the second is the employee. The third is shareholder. Ma Yun give motivate to employees by his speech, and he with the each of employees have a good relationship, and many of employees at work think that is his own company. In addition, having though emotional touch have bring good of the result to the company.


1.1 Theoretical Background
Participating in sports or other physical activity is recommended for children and youth due to the physical and mental health benefits in short-term and long-term. In addition to learn-ing sport specific skills, sports can also teach various essential life skills and has a positive effect on health later in life (Baron, 2007, Weiss, 2004, Van Langendonck & Al, 2003 in Kaleth & Mikesky, 2010, 1).

Sport specialization means that athlete is participating in intense training only in one sport while excluding other sports. Starting to specialize before puberty or in the beginning of puberty is getting increasingly common. Some level of sport specialization is needed to attain elite level in sports, but the timing of specialization is a common subject of debate. The biggest concern is that starting intense training in early childhood may be detrimental to the athlete (Jayanthi, Pinkham, Dugas, Patrick & LaBella, 2012). The potential risks in-cluded in early specialization are higher rate of injuries and overtraining, potential complica-tions in growth and maturation especially with females, burnouts, dropouts, social isolation and health issues later in life. There’s no evidence that intensive training and exclusion of other sports is necessary to attain elite level in late specialization sports.

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The trend in youth sport participation has developed from recreational free play to highly structured sport specific training with emphasis to develop skills required to succeed in sports. (Malina, 2010, 365; Vaeyens, Gullich, Warr, 2009, in Jayanthi ; Al, 2012). Jayanthi ; Al (2012) suggest that “This evolution in youth sports may have developed as a result of society’s increasing regard for successful athletes, who enjoy significant recognition and financial rewards for their achievements”.

“Sports specialization is defined as intense, year-round training in a single sport with the exclusion of other sports”.
However, there is variations on this theme. There is disagreement on what volume of train-ing is intense and does the athlete have to exclude all other sports to be classified as spe-cialized. Some suggest that there’s a minimum amount of training that has to be done to be specialized and others think that specialization means participating in one sport year round regardless of training volume (Hill & Simons, 1989 in Jayanthi & Al, 2012).

Ericsson et al “proposed 3 stages in becoming a specialist or expert musician: 1. start at an early age, 2. specialize and increase participation and 3. dedicate full-time commitment” (Ericsson, Krampe & Tesch-Romer, 1993, in Jayanthi & Al, 2012). This definitions doesn’t take into account athletes who participate in one sport year round training in high volumes, but still competes in other sports and those athletes who participate in only one sport with changing participation during the year (Jayanthi ; Al, 2012).

It’s hard to say what would be best way to define specialization, but probably it would be participating in one sport more than 8 months in a year, practicing more hours in a week than the athletes age’s in organized sports and more than 16 hours a week in intense physical activity. The common guidelines for the amount of training young athletes should do is maximum 8 months of training a year in one sport, practicing maximum the same amount of hours a week that the athletes age is in organized sports and maximum of 16 hours in a week of physical activity. Which is recommended by modern long-term devel-opment models (Côté ; Al, 2009, Lloyd ; Oliver, 2012 in Blagrove ; Al, 2017; 1).

Early Specialization Sports: “Early specialization sports (mostly acrobatic and artistic sports such as diving, figure skating, and gymnastics) are defined as sports in which early sport-specific training (by ages 5 to 7) is necessary for future excellence. In these sports, complex movement and sport skills should be acquired before the onset of the adolescent growth spurt (or peak height velocity, or PHV), which is approximately 12 years of age for females and 14 years of age for males” (Balyi, Way ; Higgs, 2013). Common between early specialization sports is also the very young age when athletes peak. This might hap-pen as early as in the beginning of puberty.

Late Specialization Sports: “Late specialization sports are practically all other sports, in-cluding team sports, racket sports, combative sports, and gliding sports” (Balyi ; Al, 2013). Common between late specialization sports is that the athletes peak after puberty.

Deliberate Practice: “Effortful practice that lacks inherent enjoyment done with the sole purpose of improving current levels of performance” (Starks ; Ericsson 2003, in Malina 2010, 366).

Deliberate Play: Training that has age appropriate rules which are set by children and su-pervised by children or an adult (Côté, Lidor ; Hackfort, 2009). Games like street hockey, street basketball or tag in swimming pool are considered as deliberate play.

Sampling, diversification, multisport background: Athlete has participated in multiple sports until mid- or late puberty.
Athlete Pathway: “An athlete pathway spans the entire continuum of athletic development, from initiation of fundamental movement and participation in physical activity through to
lifelong engagement and proficiency at a senior, elite, and/or international level” (Cameron ; Porter, 2017).

2 Literature Review

2.1 Roots Of Early Specialization
To get a better picture of the issue we first have to take a look at where and when has ear-ly specialization has started and what are the things which influence us to choose early specialization.

2.1.1 Eastern Europe
The relative success of the former communist countries of Eastern-Europe in sports es-pecially in former German Democratic Republic and Soviet Union (Malina 1994, 389, has been seen as a contributing factor to a perceived need for early specialization. In the west, it’s commonly seen that systematic training in Eastern-Europe started at early ages and involved year-round participation. The quite young age of the athletes in several sports were highlighted in the media and reinforced the early specialization being need for suc-cess. Eastern European talent identification and development programs varied to some extent by sport and emphasized participation to a variety of activities and skills in early sport experiences (multilateral training). Specialization in most sports started after or late puberty, but there was some exceptions like gymnastics, diving, figure skating and some-what also swimming. In these sports, specialization started much earlier (Bompa, 1995, Bompa 1985, Drapik, 1996, Hartley 1988, Rost and Schon in Malina, 2010; 364). It’s be-lieved that early specialization was reinforced by sport experts from Eastern-Europe who moved to western countries and started working with elite athletes (Malina, 2010; 364).

2.1.2 Role of parents
Parents play a big role when it comes to specializing in sports and other hobbies or activi-ties in young people’s life. “In the study Developing Talent in Young People (Bloom, 1985 in Malina, 2010; 365) talented individuals in sport (tennis, swimming), art (pianists, sculptors), and science (research neurologists, mathematicians), fields in which success (elite status) was attained at relatively young ages were studied.” The home environments of these tal-ented individuals had three common characteristics:
– The parents pushed their own interest into the activities of their children and they were really involved in the children’s hobbies
– The parents concentrated in development in that hobby the child was participating in
– The parents valued and emphasized achievement (Sloane, 1985 in Malina, 2010; 365).

So the parents in this study were really results-oriented and involved in their children’s hobbies. This kind of behavior has at least been influenced by stories like Tiger Woods who was introduced to Golf at the age of two and Williams sisters who have a similar background with a lot of deliberate performance-oriented practice, a very involved parent end highly-regulated life since childhood which has lead to high success (Malina, 2010; 365). Although parents are often the driving influence on the initiation of sports, multiple studies suggest that the coach is the primary driving influence on the decision to specialize in a single sport Feeley, Agel & LaPrade, 2015, 2).

Showing interest in your children’s hobbies and pushing them to achieve things is a good thing, but in children’s sports the emphasis should be on the enjoyment of sport. There’s of course other people who affects children’s specialization like coaches, friends and other people close to or meaningful to them.

2.1.3 Labeling
“Children often are labeled as gifted or talented at an early age in sport, arts and academ-ics. Such labeling probably encourages specialization (Malina, 2010).” We all have proba-bly seen some videos, heard about or seen a really young child who seems to be extreme-ly talented in his sport or playing an instrument or whatever the activity is. These children are often called (labeled) as the next superstar like the next Michael Phelps etc. This label-ing can have an effect on specialization, but to what extent is still unclear.

2.1.4 Economic benefits
Some parents and children may be affected by the possible financial benefits of sports. The mentality they have is that if you start earlier than others, they will get an edge over others by accumulating more training hours and the possibility to get scholarships, even though this is a bit unrealistic because only 2.2% of girls and 2% of boys who participate in sports in high school will get a full or partial scholarship (Pennington, 2008 in Malina, 2010, 365), sponsor deals or professional contract which is again unrealistic since only small part of children who participate in sports will ever become a professional athlete (Coté, Horton, MacDonald & Wilkes, 2009). It has been suggested that the sporting goods indus-try has affected early specialization due to increased demand for sport products and ad-vertisement aimed for parents and young people (Malina 2010, 366).

2.1.5 10 000 hour rule
There’s plenty of evidence that 10 000 hour of deliberate practice and/or 10 years of expe-rience is needed to achieve level of expertise and international success in multiple disci-plines such as music, chess and sports. Deliberate practice is described by Ericsson as “effortful practice that lacks inherent enjoyment done with the sole purpose of improving current levels of performance” (Starks ; Ericsson 2003, in Malina 2010, 366; Ericsson 1993, Sosniak 1985, Gustin, 1985, Kalinowski, 1985, Wallingford, 1975 in Baker, 2003, 86).

However, there’s also plenty of evidence proving that 10 000 hour of deliberate practice and focusing in single sport isn’t needed to achieve international level in sports. It has been studied and suggested that elite level in sports can be achieved with only 3000-4000 hours of practice (Côté, Lidor ; Hackfort 2009, 10; Moesch, Elbe, Hauge, ; Wikman 2011).

Now that 10 000 hours of deliberate practice in 10 years comes down to close to 3 hours (~2.7 hours) of practice a day every day during the 10 year period of time. That is a lot of practice which isn’t necessarily enjoyable (deliberate practice) to achieve especially for young people.

This kind of time commitment will exclude children from other activities and to achieve these training amounts, parents might see essential for their children to start specializing early in single sport (Malina 2010, 366).

2.2 Physical impact
There can also be physiological consequences to early specialization. Most commonly discussed in literature are injuries, overtraining, limited motor skills and concerns about the effect of excessive training on childrens growth and maturation, especially with females.

2.2.1 Motor skills and coordination
One of the most discussed benefits supporting specialization is learning skills for the spe-cific sport the children are participating in and it’s probably true. Athletes who practice more frequently and more hours, are more proficient than the athletes who practice less. Some adults believe that if children isn’t involved in organized sports by the age of 7, they will be behind in their skill development (Wiersma, 2000 in Buhrow, Digmann, Waldron, Gienau, Thomas & Sigler 2017, 46). However, it has been speculated that limited range of skills practiced during early specialization will harm overall skill development, which may affect involvement in physical activity and health in long-term by decreasing the likelihood of par-ticipating in other physical activities (Wiersma, 2000).

When studying about the differences in physical and gross motor coordination in boys aged 6-12 years specializing in one versus sampling more than one sport they found that children who participate in more than one sport showed better test results in strength (knee push-ups, sit-ups, hand grip strength and standing broad jump), in flexibility (sit and reach performance), speed and agility (10x5m shuttle run), cardiovascular endurance (endurance shuttle run) and in gross motor coordination (walking backwards on a balance beam, moving sideways on boxes, hopping for height on one foot and jumping sideways) (Fransen, Pion , Vandendriessche , Vandorpe , Vaeyens , Lenoir & Philippaerts 2012, 381).
(Lidor, Côté & Hackfort, 2009, 139) found that tests on same physical qualities worked as a predictor for future success in team and individual sports. While some researchers note that critical periods may exist when a sport is learned, but “Scientific evidence does not support the belief that specific skills must be learned and perfected before the onset of puberty” (Hecimovich, 2004, 35).

2.2.2 Growth and maturation
Complications in growth and maturation have been occasionally said to be as a possible result from early specialization. Especially who has a short stature and later maturation are examples of these complications (Malina 1994),

When studying the effects of training to growth and maturations, gymnastics seems to be the sport that is most affected by training at young age. In a two year comparison period of adolescent gymansts and swimmers, results showed that gymnasts had much lower growth velocity and their predicted height dropped over time (Theintz et al in Goodway & Robinson, 2015, 274). Swimming didn’t have any negative impact on the swimmers. Same findings were made by Malina (1994) and Baxter-Jones, Helms, Maffulli, Baines-Preece ; Preece (1995, 390). Malina’s research showed that swimmers were above median in height and weight and the latter study found out that male swimmers matured earlier and male gymnasts matured later than average.

There’s some findings that indicate that girls who do sports get their menarche later than girls who don’t do sports. This brings up concern that intensive training might affect girls sexual maturation. There’s hypothesis that poor nutrition, training stress and low levels of body fat is responsible for this delay. Some gymnasts might feel the pressure to have cer-tain kind of appearance and this can lead to eating disorders. (Hecimovich, 2004, 35-36).

All though this is a risk in other sports as well and not only because the pressure felt from having certain kind appearance in sports, but because of societal pressure.

“Interestingly, a slower rate of maturation has been suggested to play a role in the devel-opment of elite athletes in some sports” (Peltenburg, Erich, Zonderland, Bernink, VanDen-Brande ; Huisveld, 1984).

The research of this subject is still limited, but there’s some research showing that physical training can affect the growth and maturation of physically active children. Most of the evi-dence however, shows that sport participation doesn’t affect growth and maturation (Ma-lina, 1994 in Kaleth, Mikesky, 2010, 30).

Based on the research made for this work, it seems that gymnasts seems to be to most affected by training on their growth and maturation. Since gymnastics is an early speciali-zation sport, we can hypothesize that the cause is the intensive training gymnasts go un-der at very young age. Swimmers on the other hand seems to be safe from this.

There is concerns that physical training may cause cardiac problems, but it’s based on limited data and there’s no indication that athletic training will cause heart injury (Heci-movich 2004, 36).

2.2.3 Injuries and overtraining
As the participation in youth organized sports keep increasing, so does injuries. More and more children are participating in organized sports year-round and sometimes in multiple sports simultaneously, is the reason for increasing amount in overuse injuries. Overuse is the most common factor that leads to injuries in young athletes (Brenner, 2007).

Same findings were made by (Post, Trigsted, Riekena, Hetzel, McGuine, Brooks ; Bell 2017, 1408) in their study; the association of sport specialization and training volume with injury history in youth athletes they reported that “highly specialized athletes were more likely to report a previous injury of any kind or an overuse injury in the previous year com-pared to athletes in the low specialization group.”


The human problem our thesis work will solve is to reduce backlash in induction motor. Backlash been described as a mechanical form of dead band that can lead to error on hole location, if the motion required to machine the holes causes a reversal in axis direction it also causes loses of motion between reducer input and output shafts, making it difficult to achieve accurate positioning in equipment such as instruments, machines tools etc. The main problem electrically are vibrations from motor as a result of high ripple torque in the induction motor.
An induction motor is a kind of an AC machine in which alternating current is supplied to the stator directly and to the rotor by induction from the stator. Induction motor can appear in a single phase or a poly phase. (Toufouti, et al, 2013).
In construction, the motor has a stator which is the stationary portion consisting of a frame that houses the magnetically active angular cylindrical structure called the stator lamination. It stack punched from electrical steel sheet with a three phase winding sets embedded in evenly spaced internal slots.
The rotor which is the rotatory parts of a motor is made up of a shaft and cylindrical structure called the rotor lamination. It stack punched from electrical steel sheet with evenly spaced slots located around the periphery to accept the conductors of the rotor winding (Ndubisi, 2006).
The rotor can be a wound type or squirrel cage type.
in a poly phase motor, the three phase windings are displaced from each other by 120 electrical degrees in space around the air-gap circumference when excited from a balanced poly phase source, those windings (stator winding) will produce a magnetic field in the air-gap rotating at synchronous speed as determine by the number of stator poles and the applied stator frequency (Bimal, 2011).
In the controlling of electrical motor; the introduction of micro-controllers and high switching frequency semiconductor devices, variable speed actuators where dominated by DC motors.
Today, using modern high switching frequency power converters controlled by micro-controllers, the frequency phase and magnitude of the input to an AC motor can be changed and hence the motor’s speed and torque can be controlled. AC motors combined with their drives have replaced DC motors in industrial applications because they are cheaper, better reliability, less in weight, and lower maintenance requirement. Squirrel cage induction motors are most generally used than all the rest of the electric motors as they have all the advantages of AC motors and they are easy to build.
The main advantage is that motors do not require an electrical connection between stationary and rotating portion of the motor. Therefore, they do not need any mechanical commutators to the fact that they are maintenance free motors. The motors also have lesser weight and inertia, high efficiency and high over load capability. Therefore, they are cheaper and more robust, and less proves to any failure at high speeds.
Furthermore, the motor can be used to work in explosive environments because no sparks are produced.
Taking into account all the advantages outlined above, induction motors must be considered as the perfect electrical to mechanical energy converter. However, mechanical energy is more than often required at variable speeds, where the speed control system is not a trivial matter. The effective way of producing an infinitely variable motor speed drive is to supply the motor with three phase voltage of variable amplitude.
A variable frequency is required because the rotor speed depends on the speed of the rotating magnetic field provided by the stator. A variable voltage is required because the motor impedance reduces at low frequencies and the current has to be limited by means of reducing the supply voltage. (Schauder, 2013).
Before the days of power electronics, a limited speed control of the motors was achieved by switching the three stator windings from delta connection to star connection, allowing the voltage at the motor windings to be reduced. Induction motors also available with more than three stator windings to allow a change of the number of pole pairs.
However, a motor with several windings is very costly because more than three connections to the motor are needed and only certain discrete speeds are available. Another method of speed control can be realized by means of a wound rotor induction motor, where the rotor winding ends are brought out to slip rings (Malik, 2013). However, this method obviously removes the main aim of induction motors and it also introduces additional losses by connecting resistor or reactance in series with the stator windings of the motors, poor performance is achieved.
With the enormous advances in converters technology and the development of complex and robust control algorithms, considerable research effort is devoted for developing optimal techniques of speed control for the machines. The motor control has traditionally been achieved using field oriented control (FOC). This method involves the transformation of stator currents in a such manner that is in line with one of the stator fluxes. The torque and flux producing components of the stator currents are decoupled, such that the component of the stator current controlling the rotor flux magnitude and the component controls the output torque will differ (Kazmier and Giuseppe, 2013).
The implementation of this system however is complicated. The FOC is also well known to be highly sensitive to parameter variations. It also based on accurate parameter identification to obtain the needed performance.
Another motor control techniques is the sensor less vector control. This control method is only for both high and low speed range. Using the method, the stator terminal voltages and currents estimate the rotor angular speed, slip angular speed and the rotor flux. In this case, around zero speed, the slip angular velocity estimation becomes very difficult.
Motivation for the work
When we were on training in machine in our office, we are told gave us a drawing to produce a machine shaft. During the process, when we feed in a cut of 10mm to the machine, it would cut 9.5mm and when we wanted to drill a hole at the center of the job, it would drilled it off centered, we called on our supervisor after we have wasted much time, power and materials. Surprisingly, after his supervision, he told us that backlash in the machine is responsible for that and he instructed us to use another machine which we did and got what we need immediately. Therefore, that ugly experience motivated us to research on how to reduce high ripple torque in induction motor which is the main causes of vibrations that lead to the backlash in the industrial machine.

• The statement of the human problem our research work will solve is to reduce backlash in industrial machine.
• Explanation of the problem

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Backlash can be defined as the maximum distance or angle through which any part of a mechanical system may be moved in one direction without applying appreciable force or motion to the next part in mechanical sequence and is a mechanical form of dead band. More so, it is any non-movement that occurs during axis reversals. For instance, when x – axis is commanded to move one inch in the positive direction, immediately, after this x – axis movement, these x-axis is also commanded to move one inch in the negative direction if any backlash exists in the x-axis, then it will not immediately start moving in the negative direction and the motion departure will not be precisely one inch.
So, it can cause positioning error on holes location, if the motion required to drill the holes causes a reversal in axis direction, it also causes loses ofmotion between reducer input and output shafts, making it difficult to achieve accurate positioning in equipment such as machines tools etc.
The main cause of this problem electrically is vibrations from electric motor as a result of high ripple torque in the induction motor.

• Benefits of solving the problem
1. High quality products will be produce.
2. Productivity will increase because adjustment and readjustment of machine feeding handle or feeding screw to eliminate backlash have been reduced.
3. Operational cost will reduced.
4. Greater efficiency will be guaranteed.
5. Greater accuracy and precision of product will be guaranteed.
6. Wasting of materials will be highly reduced.
1. To develop a model that will control the error to achieve stability using DTC and fuzzy logic with duty ratio.
2. To determine the error in the torque of the machine that causes vibration which lead to backlash that result in production of less standard products.
3. To determine the position of the stator flux linkage space vector in the poles of the induction motor.
4. To determine the stator linkage flux error in the induction motor that also causes vibration.
5. To simulate the model above in the Simulink environment and validate the result.

This project work is limited to the use of fuzzy logic controller with duty ratio to replace the torque and stator flux hysteresis controllers in the conventional DTC techniques. The controllers have three variable inputs, the stator flux error, electromagnetic torque error and position of stator flux linkage vector. The inference method used was the Mamdam fuzzy logic inference system. The deffuzzification method adopted in this work is the maximum criteria method.

The importance of this work in industry where induction motor drives are mainly in application cannot be over emphasis.
As earlier noted, induction motors because of their ruggedness simple mechanical structure and easy maintenance; electrical drives in industries are mostly based on them.
Also, a wide range of induction motor applications require variable speed, therefore induction motor speed, if not accurately estimated will affect the efficiency of the overall industrial processes. Equally, the harmonic losses if not put in check will shorten the life span and efficiency of the motor inverter.
Based on the above, it is aimed at reducing the principle causes of the inefficiency in the DTC induction motor and improves the performance of the system.
The work is organized into five chapters. Various control techniques were discussed in chapter two, in chapter three, we discusses the methodology, design and implementation of the direct torque control of induction motor using fuzzy logic with duty ratio controller.
Chapter four discusses data collection, analysis and the simulated results showing the system using conventional method of control and the proposed fuzzy logic with duty ratio method of control under applied load torque conditions.
Conclusion, recommendations and suggestion for further work are mentioned in chapter five.


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