Профессионально-коммуникативная подготовка студентов

V. Read and try to understand the texts given below.

THE D.C. MOTOR PRINCIPLE

In the simple single-loop d.c. motor the magnetic field system is fixed to the frame of the motor, and the rotating part or armature supports the current-carrying conductors. The current in the field coils is known as the excitation current or field current, and the flux which the field system produces reacts with the armature current to produce the useful mechanical output power from the motor armature via carbon brushes and the commutator. It is worthwhile at this point to remind ourselves of the functions of the commutator. First, it provides an electrical connection between the armature winding and the external circuit and, second, it permits reversal of the armature current whilst allowing the armature to continue to produce a torque in one direction.

When the armature winding reaches the horizontal position, the gap in the commutator segments passes under the brushes so that the current in the armature begins to reverse. When the armature has rotated a little further, conductor WX passes under the S-pole and YZ passes under the N-pole. However, the current in these conductors has reversed. In this way it is possible to maintain continuous rotation.

Summary of important facts:

Motor action is caused by the force acting on a current-carrying conductor in a magnetic field. The direction of the force can be predicted by Fleming's left-hand rule.

A d.c. motor consists of a rotating part (the armature) and a fixed part (the frame). Electrical connection to the armature is made via carbon brushes and the commutator. The torque produced by the armature is proportional to the product of the field flux and the armature current. When the armature rotates, a back e.m.f. is induced in the armature conductors (this is by generator action) which oppose the applied voltage.

The four main types of d.c. motor are the separately excited, the shunt wound, the series wound and compound wound machines.

A d.c. machines experience commutation problems; that is, sparking occurs between the brushes and the commutator. These problems can be overcome, in the main, by using brushes which have a finite resistance and which span several commutator segments (wide

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carbon brushes) together with the use of interpoles or compoles.

D.c. motors larger than about 100 W rating need a starter in order to limit the current drawn by the motor under starting conditions to a safe value.

PRINCIPLE OF THE A.C. MOTOR

Imagine that you are looking at the end of the conductor when the S-pole of a permanent magnet is suddenly moved from left to right across the conductor. By applying Fleming’s right-hand rule, you can determine the direction of the induced e.m.f. and current in the conductor. You need to be careful when applying Fleming’s rule in this case, because the rule assumes that the conductor moves relatively to the magnetic flux (in this case it is the flux that moves relatively to the conductor, so the direction of the induced e.m.f. is determined by saying that the flux is stationary and that the conductor effectively moves to the right). You will find that the induced current flows away from you.

You now have a current-carrying conductor situated in a magnetic field. There is therefore force acting on the conductor, and you can determine the direction of the force by applying Fleming’s lefthand rule. Application of this rule shows that there is force acting on the conductor in the direction of movement of the magnetic field.

That is, the conductor is accelerated in the direction of the moving magnetic field.

This is the basic principle of the a.c. motor. An a.c. motor therefore provides a means for producing a “moving” or “rotating” magnetic field which ÅcutsÆ conductors on the rotor or rotating part of the motor. The rotor conductors have a current induced in them by the rotating field, and are subjected to a force which causes the rotor to rotate in the direction of movement of the magnetic field.

VI. Write out the key words from the text “The d.c. motor principle”.

VII. Using your key words describe the basis of a d.c. motor.

VIII. Work in pairs. Ask each other questions on the text

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“Principles of the a.c. motor”. Answering the questions, use introductory phrases: certainly; to my mind; if I am not mistaken; as far as I know.

IX. Read and try to understand the text without a dictionary.

ROTATING AND “LINEAR” A.C. MOTORS

Most electrical motors have a cylindrical rotor, that is, the rotor rotates around the axis of the motor shaft. This type of motor generally runs at high speed and drives its load through a speed-reduction gearbox. Applications of this type of motor include electric clocks, machines in factories, electric traction drives, steel rolling mills, etc.

Another type of motor known as a linear motor produces motion in a straight line (known as rectilinear motion); in this case the mechanical output from the motor is a linear movement rather than a rotary movement. An application of this type of motor is found in railway trains. If you imagine the train to be “sitting” above a single metal track (which is equivalent to the “conductor”) and the “moving magnetic field” is produced by an electromagnetic system in the train then, when the “magnet” is made to “move” by electrical means, it causes the system to produce a mechanical force between the electromagnet and the track. Since the track is fixed to the ground, the train is “pulled” along the conductor.

X. Make up dialogues on the following situations: a) types of motors and their application; b) advantages and disadvantages of a.c. and d.c. motors.

UNIT XII

MINING ROBOTICS

I. Study the following words and word combinations to be ready to read and speak about mining robotics.

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1. Оценивать: evacuate, evaporate, evaluate, evermore. 2. Добывать: to wind, to win, to widen, to wish. 3. Гибкий: flexible, flammable, floating, fluorescent. 4. Горнодобывающий: missing, mineral, milestone, mining.

III. Use the words and word combinations from exercise I in the following sentences. 1. Mining conditions … over years. 2. Computers are used … the coal reserves. 3. Computers evaluate … of robotics application. 4. Up-to-date mining machines … coal nowadays. 5. In hard and cnanging environment … systems are used. 6. … of the mining machine must be robust and reliable.

IV. Read the text given below and find the answers to the questions: a) What are the reasons of robotics in mines? b) Where is mining robotics expanding? c) What views are there on what constitutes a mining robot? d) How is a robot defined in this text? e) In what environment has a robot to work in mines?

PREFACE

The deterioration of mining conditions, the rising cost of labour, the limited potential of both humans and traditional mining machines and the lock of skilled workers are some of the reasons to consider robots in mining. The history of mining robotics since 1967 is analyzed. Six criteria for using robots are presented and evaluated. Three possible shapes for mining robotics are presented. Several examples of ro- botics-based mining ore suggested. Functional modeling and Petri nets are used in. order to simulate mining robotic systems. To evaluate о profitability of robotics for mining, a simple method using both direct and indirect sources of robotics efficiency is proposed.

Mining robotics is expanding between mining and machine built robotics. There are two opposite views on what constitutes a mining robot: some experts consider one must use a person who is actually

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manipulating the robot, but other experts use a robot by connecting it to mining machines. For the purpose of this paper, a robot is defined as a self-propelled mining machine with a flexible control for multifunctional use of the working head during mining. In addition to working with well-known robots as found in other industries, in mining one has to work with high loading by changing environment and limited working space. In addition, robotics-based mining must give a good economic return. More than 160 world publications about possible applications of robotics in mining (1975–1995) were found.

In general, most papers predicted a great future for mine robotisation, especially dating back to 1982. Some publications presented high-automated mining machines as robots. The main problems of robotics for mining such as the overall aims and different fields of use, correct terminology, their social role, robotics-based technologies, integration with other technologies during mining, man-machine control, and adaptation to environment state have not yet been defined.

V. Retell the text given above using the questions of exercise IV as a plan. Don’t consult the text. Express your own opinion using the following introductory phrases: as far as I know, to my mind, if I’m not mistaken, it’s worth mentioning.

VI. Study the following words and word combinations.

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VII. Translate the sentences in written form. 1. The first unmanned railhaulage was used at the underground mine “General Blumental”. 2. Some drill carriages with re-programmable positioning of drill boom were created. 3. The time of movement between blastholes was reduced by a factor of two. 4. Application of mining robotics was repaid after 400 working cycles. 5. Professor M. Thring constructed a model of remote-controlled manipulator for use in the extraction of thin coal seams. 6. The guidance of LHD-machine, an inspector robot NUMBAT, a shotcreting manipulator, an automatic manipulator for the mounting of drill string, a roof bolt setter were developed. 7. The remote-control of shearer macnines from the surface, robotised drilling rigs, continuous miner and rock bolters were developed. 8. It was difficult to both sense any efforts on a remote manipulator and keep an eye on a service zone inside a limited space. 9. The use of on-board technical vision system allowed the selective extraction of multi-layer seams by a heading machine, automatic scooping from any stockpile, automatic shotcreting and charging of blastholes, recognition of the coal interface. 10. It is now possible to unite automated machines by a mine-wide information network that is connected with a computer on the surface.

VIII. Read the text given below. Find the following facts about mining robotics: 1) new possibilities for mining robotics in future; 2) stages of mining robotics development; 3) modern technology pro-

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jects and their aims.

PRECONDITIONS AND HISTORY

A multifactor model of manual labour relating to both during winning the coal and driving was developed using to statistical reports from 72 underground mines in the Kuznetzki Coal Basin that supplies 70% of the coal output in Russia:

The divergence between this model and reality for 1985–1990 is 10%. The comparison of the opposite factors has shown that the influence of traditional mechanization will not be able to compensate for the increase of manual labour owing to deterioration of mining conditions. In addition, the cost of a miners’ labour continually increases. Mining employers have a considerable amount of money to pay for non-productive human factors such as safety, insurance, ventilation, idle times, movement to у working place, training, etc. At the same time, the cost of robotics is decreasing. That is why, robotics for mining is one satisfactory way to remove miners out of dangerous underground mining situations.

Development of mining robotics can be divided into three stages. In 1967, the first unmanned rail haulage was used at the underground mine “General Blumenthal” (Germany). The same systems were developed for the ore mines “Tashtagol” (Russia, 19-72); “Kiruna” (Sweden, 1975), “Henderson” (USA, 1974), and “Stashiz” (Poland, 1975). Later locomotives without drivers were classified as rail transport robots. Some drill carriages with re-programmable positioning of drilling boom were created in France, Japan, and Norway. The time of movement between blastholes was reduced by a factor of two. Then, remote control of LHD-machines in dangerous places was introduced. In spite of time losses from using mining robotics at the ore mine “Vihanti” (Finland) this was repaid after 400 working cycles owing to the increased extraction of ore. Such mining machines with repetition of simple operations were found to be suitable for robotization.

In 1976 Prof. M. Thring from the Queen Mary College (Great Britain) constructed a model of remote-controlled manipulator for use in the extraction of thin coal seams. The robot consisted of two bodies with three jacks, two manipulators, and two TV cameras that were connected with four operators on a surface.

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Since 1980, many of the world experts discussed the many possibilities for robotics in mining. It was expected that the first mining robots will be working instead of miners in the American coal industry by 1995. National programs for mine robotisation were formed in the Great Britain (NGB), Canada (CCARM), France (RAM), Australia and the USSR. After 1985, the remote control of a shearer machine from the surface (CER-CHAR, Eickhoff), robotized drilling rigs (Montabert, Atlas Copco), robotized continuous miner, and rockbolters (USBM) were developed. At the same time, some unsuccessful attempts to use a remotely-controlled manipulator for auxiliary actions during mining took place. It was difficult, to both sense any efforts on a remote manipulator and keep an eye on a service zone inside a limited space. Also, the use of manipulator during traditional mining was not effective because many of the intermediate actions such as assembling are inaccessible for robotics but are intended for a miner.

Lately, the guidance of LHD-machine along a reflecting belt, an inspection robot NUM-BAT, a shotcreting manipulator “Stabilator”, automatic manipulator “Scanska” for the mounting of drill string, a roof-bolt setter “Robolt” were developed for use at different mines were all introduced. Other advances include: the use of on-board technical vision systems allowed the selective extraction of multi-layer seams by a heading machine, automatic scooping from any stockpile, automatic shotcreting and charging of blastholes, recognition of the coal interface. The control of underground LHD-machines from the surface in Canada can be considered as a great advance in mining robotics.

It is now possible to unite automated machines by a mine-wide information network that is connected with a computer on surface. The Scandinavian technology program “Intelligent Mine” is aimed to increase the working time by information change in real time apply high technologies to mining, form of mining machinery for the 21st century and robotize mobile mining machines. One project consists of 28 projects such as navigation of mobile machines, robotized LHDmachines, automatic charging, shotcreting, and drilling, high-speed information network, computer control of mining from surface in realtime.

The same program “KUJ 2000” is being applied at the giant ore mine “Kiruna” in Sweden. Germany has developed the project “Par-

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tially Automated Mine” that consists of five levels: on-board automation of machines, dispatching of several automated machines from surface, dispatching of mining, computer planning of mining and analysis of mining for optimum planning. The Canadian “Mining Automated Plan” is aimed to replace of miners by automated and robotized machines. Lately, robotics for mining on other planets is being studied. Some results of one project are considered to have applications for mining on Earth.

IX. Find in the text given above the sentences proving the following statesments in Russian. 1. Скандинавская технологическая программа предназначена для увеличения рабочего времени сменой информации в реальном времени. 2. Традиционная механизация не способна компенсировать увеличение ручного труда в шахте. 3. Работодателям на шахтах приходится тратить значительные средства на непроизводительный человеческий фактор. 4. Недавно разработан целый ряд робототехники для использования на различных шахтах. 5. Один план состоит из 28 проектов. 6. Развитие горнодобывающей робототехники можно разделить на три стадии. 7. Трудно одновременно следить за дистанционным манипулятором и рабочей зоной в ограниченном пространстве. 8. Профессор Фринг сконструировал модель манипулятора для дистанционного управления для работы в тонких угольных пластах.

X. Write out the key words for retelling the text given above.

XI. Retell the text using your key words. Organize the competition: the winner is the student who can give more main facts from the text given above during one minute.

XII. Read the given below text. Express its main idea in Rus-

sian.

POTENTIALITY OF ROBOTICS FOR MINING

It is not effective for a robot to imitate miner’s actions for traditional mining. The full potential of robotics is not realized in this case.

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Generally speaking, well known functions of robotics such as kinematics of manipulators, re-programmable control, sensors, masterslave control, etc. can be transferred into mining. Well known robotic systems are adapted to changing targets by the stable environment, whereas mining robotics systems are adapted to the changing environment by the stable target. Mining robots must reduce hard manual labour, work in dangerous and inaccessible places for miners, and apply high technologies to mining.

There are three types of robotisation in mining: the use of re- mote-controlled manipulators for mechanization of miner’s actions, the creation of technological robots on the basis of mining machines with adaptive control, and the introduction of information robots in case of mine disasters.

Replacing a miner with a remotely-controlled manipulator is one obvious type of robotisation. The technology is not changed but a miner has to keep an active participation for every working cycle.

The main problem here is how to ensure the telepresence of an operator in a working space. A manipulator must be equipped with a TV – camera and force sensors. High-speed actions of the manipulator, work in an invisible environment, rotary and telescopic movements cannot be realized because an operator is limited by new possibilities of the manipulator.

Multifunctional technological robots for robotics-based mining can be considered as the second type of mining robotics. This provides a working tool for a direct processing, such as drum, cutting head, or drilling boom. One type of the robot may be a mining machine with sensors and adaptive control that can work without a miner. Several technological robots can cooperate during mining with a local area network. These form a robotics-based mining system. The main problems here are to create non-traditional technologies of mining, removing manual actions, and recognize unpredictable technological situations during mining.

As the third type of mining robotics, a mine rescue robot can be considered. This remotely-controlled robot must have a mover for hard conditions, on-board accumulators, TV-camera, and sensors for some types of gas, temperature, fire, pressure, and water invasion. One must transmit or store information about the conditions in dangerous areas for the mine rescue team. In addition, a mine rescue robot can

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