It is about digital signal processing based on motor control technology

1. DIGITAL SIGNAL PROCESSING
BASED ON MOTOR CONTROL
PREPARED BY
B MANISHA
ECE
1

2. Contents
• Introduction
• What is DSP ?
• Why and how the digital platform ?
• Motor control trend
• DSP Controllers
• TMS320 Family overview
• TMS320C24X DSP Controller
• AC Induction motor
• The scalar control
• The vector control
• Application
• Conclusion
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3. Introduction
• Motor Control industry is a strong aggressive sector.
• We have major problems in this industry are Power
consumption reduction and EMI Radiation reduction
imposed by Government and power plant lobbies.
• This results lead to need of enhanced algorithms.
• DSP technology allows to achieve the high level
performance as well as system cost reduction.
• Texas instruments launches a new DSP , referenced
TMS320C240, specifically designed for the digital
motor control segment.
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4. What is DSP ?
• DSP stands for Digital Signal Processing, deals with
processing on signals to get desired output/response on
digital processors.
• some of basic processes/operations on signals involves
1. Filtering,
2. Scaling(Amplification/Attenuation),
3. Addition or Substraction of two or more signals,
4. Integration/differentiation,
5. Modulation(Amplitude/Angle), etc.
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5. Why and how the digital platform ?
• Why Digital ?
• Advantage
1. Flexibility
2. Accuracy
3. Storage
4. Low cost
5. Compact size
6. Reliability
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6. Cont...
• Disadvantages
1. Limitation of A/D
2. Expensive
3. Quantisation error
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7. Motor control trend
• Market analysis shows that most of all industrial motor
applications use induction motor.
• Traditionally motor control was designed with analog
components. However there are several drawbacks with
analog systems.
• Digital systems offer improvements over analog design.
They are:
1. Drift is eleminated.
2. Upgrades can easily be made in software.
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8. Cont.....
• Digital signal processors go on further to provide high
speed and high resolution in order to reduce system costs.
• Generally fixed point DSPs are preferred for motor control
for two reasons
1. Less cost.
2. Dynamic ranfe is 16 bit.
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9. DSP Controllers
• DSP controllers are known as
Digital signal controllers(DSC).
• Digital signal controllers are
hybrid of microcontrollers and
DSPs.
• In DSCs, DSP is used as control
element.
• The top three DSC vendors are
Texas Instruments,Freescale, and
Microchip Technology.
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10. cont....
A Large Range of Applications
Ø Appliances
Ø Appliances
Ø Industrial servo drives
Ø Automotive control
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11. Cont...
Benfits of DSCs
• favours system cost reduction by an efficient control in
all speed range implying right dimensioning of power
device circuits.
• enables a reduction of harmonics using enhanced
algorithms, to meet easier requirements and to reduce
filters cost.
• removes speed or position sensors by the implementation
of sensorless algorithms.
• provides single chip control system.
• enables a reduction of harmonics using enhanced
algorithms, to meet easier requirements and to reduce
filters cost.
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12. cont....
DSPs controllers may also performs the following:
• enables control of multi-variable and complex systems.
• performs adaptive control.
• provides diagnostic monitoring with FFT of spectrum
analysis.
• produces sharp-cut-off notch filters that eliminate narrow-
band mechanical resonance.
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13. TMS320 Family overview
• This family consists of fixed point,multiprocessor digital
signal processors (DSPs), and fixed-point DSP
controllers.
• TMS320 DSPs have an architecture designed specifically
for real-time signal processing.
• The TMS320 supports the power switching device
commutation, control algorithm processing,data
communications and system monitoring functions.
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14. History of the TMS320 family
• The TMS320 family currently includes
five generations of DSP.
• TMS320C25, a CMOS 40-MHz digital
signal capable of twice the performance
of the TMS320C1x devices.
TMS320C1x,
TMS320C2x,
TMS320C3x,
TMS320C4x,
and
TMS320C5x
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15. TMS320C24X DSP Controller
• The TMS320C24x is a member of the TMS320 family
of digital signal processors(DSPs).
• The ’C24x is designed to meet a wide range of digital
motor control(DMC) and embedded control applications.
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16. cont.....
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17. Cont....
TMS320C240
• Texas Instruments launches a new DSP, referenced
TMS320C240, specifically designed for the Digital
Motor Control segment.
• The TMS320C240 device combining a 16 bit fixed-
point DSP core with microcontroller peripherals in a
single chip solution is part of a new generation of DSPs
called the DSP controllers.
• These systems lack the ability to execute advanced
algorithms fast enough for real-time control.
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18. cont...
TMS320C240 Architecture
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19. AC Induction motor
• The motor studied in this note is
part of the Alternative Current
supplied motors. It is the squirrel
cage asynchronous motor,
named AC induction motor.
• The least expensive and most
widely spread induction motor is
the squirrel cage motor.
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20. cont.....
• There are several ways to control an induction motor in
torque, speed or position, they can be categorized into two
groups they are :
1) Scalar control
2) Vector control
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21. The scalar control
• Scalar control means that variables are controlled only in
magnitude and the feedback and command signals are
proportional to dc quantities.
• A scalar control method can only drive the stator
frequency using a voltage or a current as a command.
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22. cont...
Advantages
Ø Its simplicity,
Ø It is easy and fast to program,
Ø Requires only few calculation capabilities.
Drawbacks
Ø Very poor reaction time,
Ø In this both flux and torque are the function of
voltage/current and frequency. This tends the system
into instability due to higher order harmonics.
Ø This method needs some characteristic plots to
describe part of the control.
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23. The vector control
• The vector control is referring not only to the magnitude
but also to the phase of these variables.
• This method takes into consideration not only successive
steady-states but real mathematical equations that
describe the motor itself.
• Though the induction motor have a very simple structure,
its mathematical model is complex due to the coupling
factor between a large number of variables and then on-
linearities.
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24. cont...
• The Field Oriented Control (FOC) offers a solution to
circum vent the need to solve high order equations and
achieve an efficient control with high dynamic.
• There are two approaches to vector control:
1. Direct field oriented current control
2. Indirect field iriented current control
24

25. cont....
Principles of Vector Control
• The basic conceptual implementation of vector control is
illustrated in the below block diagram:
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26. Field oriented control
• The FOC consists of controlling
the stator currents represented
by a vector.
• The goal of the FOC (also
called vector control) on the
asynchronous machine is to
control the torque producing
and magnetizing the flux
components seperately.
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cont...

27. cont...
• Advantages of vector control
1. Transient response will be fast,
2. Vector control allows for speed control in all four
quadrants (without additional control elements),
3. Reduction in size of motor, cost and power consumption.
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28. Applications
• Refrigerators,
• Washing machine,
• Dryers,
• Pumps,
• Fans,
• Blowers, etc.
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29. Conclusion
• The DSPController TMS320C240 combines the
performance of a DSP architecture with the optimized
peripherals of a Microcontroller in a single chip
solutions for the control of an induction motor.
• With the DSP controller an intelligent control approach
is possible to reduce the overall system costs and to
improve the reliability of the drive system.
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