Mixed Signal Modelling Comp
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Transcript of Mixed Signal Modelling Comp
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VHDL AMS DESIGN FOR AN
EMBEDDED CONTROLLER
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Agenda
Introduction
Need for mixed signal modeling
VHDL AMS
Features ,Advantages and applications
Digital flight controller
QFT
QFT design
References
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Introduction
Mixed signal system modeling
HDL programming language used for modeling.
3 types of HDL
1. analog ( spectre HDL)
2.digital (VHDL, Verilog)
3. mixed signal (VHDL AMS, Verilog AMS)
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Introduction to VHDL AMS
IEEE Std. 1076-1993
description and simulation of event-driven systems.
IEEE Std. 1076.1-1999
support the description and simulation ofanalog and
mixed-signal circuits and systems.
IEEE Std. 1076.1-1999 together with IEEE Std. 1076-1993 is VHDL-AMS.
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Extension of VHDL standard
Adds support for DAEs and conservative quantities
Supports description and simulation of analog, digital,mixed signal, multi-physics devices
Encourages device modeling at various architecturelevels (ideal, non-linear, transistor)
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Features
It has a well-defined simulation cycle
It can model continuous and discontinuous behaviour
Equations are solved using conservation laws
Represents complex models directly.
High efficiency.
Describes non electrical physical phenomenon.
Easy to model.
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VHDL AMS language architecture
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Basic concepts
A VHDL-AMS model consists of an entity and one or
more architectures.
The entity specifies the interface of the model to theoutside world.
The architecture contains the implementation of the
model.
Packages define collections of re-usable declarations
and dfinitions, types, constants, functions etc.
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Advantages
Readable documentation of discontinuous behavior
Facilitates model exchange
Facilitates model reuse
Facilitates tool substitution
Competition will strengthen capabilities of the tools and
will reduce tool cost
Modeling concepts have proper semantics
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VHDL Vs VHDL AMS
VHDL
IEEE 1076-1993
digital domain
model only electrical
parameters
single domain simulation
Time discrete system
VHDL AMS
IEEE 1076.1-1999+1076-
1993
Mixed domain
model electrical and non
electrical parameters
Multi domain simulation
Time continous system
Conservative and non
conservative systems
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Digital flight controller
Digital control system transfers all pilot commands to the
control surface actuators through electrical wires
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Robust control
Fundamental issues in the design, analysis andevaluation of control systems.
Stability
Performance Stability
In the absence of external excitation, all signals inthe system decay to zero.
It is an absolute requirement.
Its absence causes signals to grow without bound,eventually destroying and breaking down the plant.
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Performance
Ability to track reference signals closely
Reject disturbances.
Robust Control system
Should preserve stability in the presence ofvarious classes of uncertainties.
Should be capable of tracking all reference
signals belonging to a class of signals, withoutexcessive error, despite various types ofuncertainties.
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QFT
Developed by Horowitz and Houpis in 1960
QFT is an extension of frequency domain
approaches.
QFT is a method for practical design of feedbackcontrol systems.
controller can be obtained to satisfy performanceand stability specifications over a range of plant
uncertainty.
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Main objectives of QFT
Get simple low order controllers
Get minimum bandwidth controllers To avoid noise amplification
To avoid resonance
To avoid high frequency dynamics
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Characteristics of QFT
Amount of feedback depends on
Amount of plant
Magnitude of disturbance
Level of performance specifications
QFT offers direct tradeoff between
Stability and performance specifications
plant uncertainity and disturbance uncertainity
controller complexity
controller bandwidth
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Feedback Design with QFT
Define frequencies
Create frequency response data
Define sampling time
Define nominal response
Define controller type
Define phase array for bounds.
Compute bounds
Loop shaping
Compare design to
specifications
End
Define
problem data
Compute and
manipulate
bounds.
Design
Analysis
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QFT CONTROLER STRUCTURE
y(t) is required to track the input r(t) and reject
disturbances.
controller is designed so that variations are within
tolerance range
Filter is the input filter transfer function
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Plant as a second order system
Actuators and flight control surface are modelled as
second order systems
F=PA
FA - Fp = Mps2Xp+BpsXp Torque due to hydraulic force imbalance is
Tr= kh/Rh (xp-xL)
torque on actuator is
TR - TL = J Ls2L +BLsL
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Final transfer function is
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Future work
Digital flight controller is converted in to VHDL AMS
hardware description language.
The design technique is to control transmission aroundthe feedback loop within certain specifications.
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Expected simulation result
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[l] Peter J Ashended,Gregory D Peterson and Darell A Teegarden, SYSTEMDESIGNERSGUIDETO VHDL AMS2nd edition Morgan Kaufmann
Publishers September 2002.
[2] Robert L. Ewing, John W. Hines, Greg D. Peterson, & Maya Rubeiz,VHDLAMS design for flight control system IEEE proceedings,Aerospace
conference,vol 1;pp 223-229;march 1998.
[3] Alex Doboli,Ranga Vemuri,Behavioural modeling of high level synthesis
of analoge and mixed signal system from VHDL AMS IEEE transactions
on computer aided design of integrated circuits and
systems,vol.22,No:11,nov 2003.
[4] VHDL-AMSA hardware description language for analog and
mixed-signal applications, IEEETrans. Circuits Syst. II, vol. 46, pp.
12631272, Oct. 1999.
[5] The Institute of Electrical and Electronics Engineer, IEEE Standard 1076.1-
1999,IEEE, 1999.
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[6] Isaac M. Horowitz. Quantitative Feedback Design Theory (QFT),volume 1.
QFT Publications, 1993.
[7I C.H. Houpis and R.L. Ewing. TOTAL-PC Users Manual.Air Force Institute
of Technology, 1997.
[8] Constantine H. Houpis and Gary B. Lamont. Digital ControlSystems.
McGraw-Hill Book Company, 2nd edition, 1992.
[9] KI- Ho Kang. Electro-hydrostatic actuator controller design using
quantitative feedback theory. Masters thesis, Air Force Institute ofTechnology, December 1994.
[10] Giovanni De Micheli. Synthesis andOptimization ofDigital Circuits.
McGraw-Hill Book Company, 1994.[11] A lain V achoux. Analog and mixed-signal extensions to VHDL. Analog
Integrated Circuits and Signal Processing, 1998.
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THANK YOU