DIGITAL CONTROL SYSTEMS

bustlingdivisionElectronics - Devices

Nov 15, 2013 (3 years and 10 months ago)

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© 2009 HBUT
Hubei University of Technology
CHAPTER 13
CHAPTER 13
DIGITAL CONTROL
SYSTEMS
© 2009 HBUT
Hubei University of Technology
13.1 Introduction
13.1 Introduction
A digital control system uses digital signals and a digital
computer to control a process. The measurement data
are converted from analog form to digital by means of
the analog-to-digital converter shown in the figure
below:
A block diagram of a computer control system, including the signal
converters. The signal is indicated as digital or analog.
© 2009 HBUT
Hubei University of Technology
13.2 Digital Computer Control System Applications
13.2 Digital Computer Control System Applications
The development of INTEL microprocessors measured in
millions of transistors. (Source: INTEL)
© 2009 HBUT
Hubei University of Technology
© 2009 HBUT
Hubei University of Technology
© 2009 HBUT
Hubei University of Technology
© 2009 HBUT
Hubei University of Technology
13.2 Digital Computer Control System Applications
13.2 Digital Computer Control System Applications
The advantages of using digital control include:
improved measurement sensitivity; the use of
digitally coded signals, digital sensors and
transducers, and microprocessors; reduced
sensitivity to signal noise; and the capability to
easily reconfigure the control algorithm in
software.
© 2009 HBUT
Hubei University of Technology
13.3 Sampled-Data Systems
13.3 Sampled-Data Systems
Sampled data (or a discrete signal) are data
obtained for the system variables only at
discrete intervals and are denoted as x (k T).
© 2009 HBUT
Hubei University of Technology
13.3 Sampled-Data Systems
13.3 Sampled-Data Systems
A digital control system
© 2009 HBUT
Hubei University of Technology
13.3 Sampled-Data Systems
13.3 Sampled-Data Systems
An ideal sampler with an input r (t).
© 2009 HBUT
Hubei University of Technology
© 2009 HBUT
Hubei University of Technology
13.3 Sampled-Data Systems
13.3 Sampled-Data Systems
A sampler and zero-order hold circuit.
© 2009 HBUT
Hubei University of Technology
13.3 Sampled-Data Systems
13.3 Sampled-Data Systems
The transfer function of the zero-order hold
is:
Precision is the degree of exactness or
discrimination with which a quantity is stated.
The precision of the computer is limited by a
finite word length.
© 2009 HBUT
Hubei University of Technology
13.3 Sampled-Data Systems
13.3 Sampled-Data Systems
The response of a sampler and zero-order
hold for a ramp input r (t) = t.
© 2009 HBUT
Hubei University of Technology
13.3 Sampled-Data Systems
13.3 Sampled-Data Systems
The response of a sampler and zero-order hold to an input
r (t) = e
–t
for two values of sampling period T.