Akademik Veri Yönetim Sistemi
Tezin Türü: Yüksek Lisans
Tezin Yürütüldüğü Kurum: İstanbul Teknik Üniversitesi, Lisansüstü Eğitim Enstitüsü, Türkiye
Tezin Onay Tarihi: 2023
Tezin Dili: Türkçe
Öğrenci: ALP EREN ÇALICIOĞLU
Danışman: Mehmet Turan Söylemez
Özet:
Motors are also needed in every area where there is movement. They are used in
most areas that come to mind, especially in general sectors (such as production,
transportation, energy) and routine life (such as household appliances,white goods).
The need for motors is increasing day by day with the increasing world population and
modernization.
The motor is the machine that converts the energy it uses into the energy of motion
in a rough term. The used energy can be various types such as solid fuel, liquid fuel,
and electricity. These engines using different fuels have divergent usage areas; also,
every types have different advantages. Environmental pollution is a serious problem,
and it increases considerably today and continues to increase day by day, so it is very
important that the motors are harmless in terms of environmental pollution because the
motors are widely used in today.
Among all these motors, electric motors find a wide usage area due to their advantages.
The main advantages of electric motors are high efficiency, wide torque and speed
characteristics, absence of gas emissions (environmental friendliness), silent operation,
easy running, and basic structure.
There are different types of electric motors, and these types have different usage areas,
advantages and disadvantages. Electric motors can be classified according to working
principle (induction motor, syncronous motor, DC motor, and special types), rotor type
(inner, outer), working trajectory (linear, circular), current type (AC, DC), and so on.
The induction motor or asynchronous motor is one of the oldest type of electric motors
working with three-phase alternating current. There are two types of asynchronous
motors as follows; slip ring and squirrel cage. In this thesis, a squirrel cage
asynchronous motor is used for simulations. The asynchronous motors have a very
simple structure, so they are a very cheap, small-sized and stable electric motors.
Similarly, they do not cause safety problems such as sparks, since there are no brushes
and commutators in their structures; moreover, they do not require maintenance.
Asynchronous motors are very common in industry, especially in the transportation
and manufacturing sectors.
Asynchronous motors are fed with a single alternating current thanks to their working
logic, and the rotor part can rotate with the help of rotating field of stator. Therefore,
asyncronous motor is also called induction motor. Asyncronous motors have very
basic structure, so they have lots of advantages. However, asyncronous motors have
also some disadvantages because of their working principle. These disadvantages are
having nonlinear mathematical model and having one fed currents. Having nonlinear
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model brings the uncertainty and using complex controllers. Also, there is no seperated
fed currents, so the moment and speed cannot be controlled seperately that means
controlling of asyncronous motor is more difficult than other types of electric motors
that fed with two currents such as DC motors.
There are different control methods of induction motors. Scalar and vector control
are the leading ones. These two methods have different purposes and advantages.
Scalar control is a basic control method which control the speed to keep the ratio of
voltage and frequency. However, scalar control is very weak in low and high speeds.
In general, it is not preferred in precise applications. In this study, vector control,
which can give more precise control results, is studied. Vector control is also divided
into two types as direct and indirect vector control. Indirect vector control method,
which does not directly need flux value and position, is preferred in this study. The
induction motor is controlled with two separated currents like a DC motor with the
help of some transformations in the vector control; therefore, the control process is
more simplified and easier. Direct vector control is expensive solution because it need
sensors to measure flux value and position in the rotor side. However, it has also
advantages against indirect vector control such as indirect vector is very depend on
model, and it is affected by changing the mathematical model.
The number of vehicles in the transportation sector is increasing day by day; therefore,
it is very important that the motors used in the transportation sector are environmentally
friendly and highly efficient. When considering railway transportation vehicles, high
working hours and long-term lifetime are at the forefront, so the efficiency of the
motor, which is the most important part of the propulsion system, is very important.
Permanent magnet electric motors are a good alternative in all areas where efficiency is
high, but due to the magnet supply problems, the usage of permanent magnet electric
motors is decreasing day by day.
Subways are a good transportation alternative for big cities because they which use
the railways and go underground do not occupy an additional lane of roads. In
addition, in big cities where there is a high density of people, usage volume of subways
is increasing in big cities where have a high density of people because traffic-free
solutions are preferred.
The asynchronous motor model is prepared in MATLAB Simulink environment, and
the motor is designed to be used in a subway vehicle. Since subways generally work in
cities due to their working principles and advantages, they are not required to operate
above a certain speed for safety reasons, and they are prevented from exceeding a
certain acceleration due to passenger comfort and safety. These limits were taken into
account while modelling; besides, the model has different limits that are created from
the structure of the asyncronous motor such as maximum torque, maximum voltage,
and maximum power.The simulations are done under the whole saturations.
The acceleration should be kept under control considering the asynchronous motor
control due to the safety and comfort issues mentioned above. However, the
acceleration is not controlled directly. Besides, the speed should be controlled
precisely because it is expected from the subways keep in safe speeds. In addition,
overshoot is not desirable for speed control. These performance criteria are taken into
account for the control structures.
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Asynchronous motors, like other electric motors, get warm while working, so the
changing of motor parameters as resistance and inductance occur as a result of heating.
Moreover, as mentioned above, certain assumptions are made in the model due to
the nonlinear structure of asynchronous motors. In addition to, all these model
related obscurities and parametric changes, the uncertainty and changes caused by
the way of the subway, and the changing of total weight owing to the passengers
requires the control structure to be robust. For this reason, the robustness of the
designed control structure and the ability to successfully control the system under
different conditions are also considered as a performance criterion. Uncertainty is
added to motor resistances, inductances, total weight, angle of path, and path (tunnel)
coefficients after that whole controller performances is examined, and compared each
other.
While controlling the speed of asyncronous motor, the current controllers are firstly
designed. After that, the speed is controlled.d and q axes of currents are controlled
with the help of PI controllers in order to vector control of asyncronous motor. The
current controllers are designed in the linear model, and they are used in the non-linear
model.The simulation results of the linear and non-linear models are very similar
according to current control because there is no saturation and it is very simple control
structure.The design criterias of these PI controllers are selected as rise time and
settling time because the most important thing for currents is following the desired
current as fast as possible.
PID, PI-PD, fuzzy control, sliding mode control and non-linear dynamic inversion
methods are used to control of the induction motor. These control methods are
designed for speed controls which are designed in the non-linear model. The designed
control structures are compared according to the desired performance criteria such as
overshoot, ISE and settling time.
The results of PID and PI-PD control methods are similar; however, PI-PD controller
has lower control signal and lower overshoot. Besides, PI type fuzzy controller is used
to control the induction motor.
Under the influence of parametric uncertainities, fuzzy control and sliding mode
control have robust behaviour. Also, non-linear dynamic inversion have limited robust
behaviour under some spesific uncertainities. Nevertheless, PID and PI-PD controllers
are not robust.
While designing the control methods, the big bang big crunch optimization method
which is found by Osman Kaan Erol and ˙Ibrahim Eksin is used. KP, KI and
KD coefficients for PID and PI-PD controllers, scaling coefficients for fuzzy logic
controller, gain coefficients for sliding mode control and nonlinear dynamic inversion
controllers are found and optimised with the help of this optimization method. Biggest
advantage of big bang-big crunch method is finding optimum value very fast.
The comparative results of the whole controllers are shared in the study. These results
are for nominal values and modified values with the parametric uncertainties.