Electronic Systems Design Group
University of Southampton, UK
School of Electronics and Computer Science
BMAS 2005BMAS 2005
VHDLVHDL--AMS based genetic optimization of AMS based genetic optimization of a fuzzy logic controller for a fuzzy logic controller for
automotive active suspension systemsautomotive active suspension systems
Leran Wang and Tom KazmierskiLeran Wang and Tom Kazmierski{lw04r,tjk}@ecs.soton.ac.uk{lw04r,tjk}@ecs.soton.ac.uk
BMAS, San Jose, CA, 22-23 Sep 2005 2
Electronic Systems Design Group
University of Southampton, UK
School of Electronics and Computer Science
OutlineOutline
•• Introduction and system modelIntroduction and system model•• Shape optimization of fuzzy logic membership functionsShape optimization of fuzzy logic membership functions•• Integrated GA optimiser in VHDLIntegrated GA optimiser in VHDL--AMS AMS testbenchtestbench
implemented as a state machine implemented as a state machine •• Experimental results Experimental results •• ConclusionConclusion
BMAS, San Jose, CA, 22-23 Sep 2005 3
Electronic Systems Design Group
University of Southampton, UK
School of Electronics and Computer Science
Introduction and system modelIntroduction and system model•• VHDLVHDL--AMS recommended by a European automotive AMS recommended by a European automotive
consortium as a unified automotive consortium as a unified automotive modelingmodeling language language •• Automotive active suspension systemAutomotive active suspension system
• Active suspension• Actuator controller
Fuzzy logic controller
BMAS, San Jose, CA, 22-23 Sep 2005 4
Electronic Systems Design Group
University of Southampton, UK
School of Electronics and Computer Science
Fuzzy logic controller (FLC)Fuzzy logic controller (FLC)
• Based on the general principles of fuzzy set theory (L. Zadeh, 1965)• Input and output variables are similar to a conventional controller• Handling uncertain and complex systems, e.g. active suspension system
BMAS, San Jose, CA, 22-23 Sep 2005 5
Electronic Systems Design Group
University of Southampton, UK
School of Electronics and Computer Science
Fuzzy logic controller (FLC)Fuzzy logic controller (FLC)•• Regular membership functionsRegular membership functions
• Triangular
BMAS, San Jose, CA, 22-23 Sep 2005 6
Electronic Systems Design Group
University of Southampton, UK
School of Electronics and Computer Science
Fuzzy logic controller (FLC)Fuzzy logic controller (FLC)•• Regular membership functionsRegular membership functions
• Trapezoidal
BMAS, San Jose, CA, 22-23 Sep 2005 7
Electronic Systems Design Group
University of Southampton, UK
School of Electronics and Computer Science
Genetic algorithm (GA)Genetic algorithm (GA)
•• Optimization method based on natural Optimization method based on natural selection (D. Goldberg, 1989)selection (D. Goldberg, 1989)
•• A GA usually has the following elementsA GA usually has the following elements• Population of chromosomes• Selection according to fitness• Crossover to produce new offspring• Random mutation of new offspring
BMAS, San Jose, CA, 22-23 Sep 2005 8
Electronic Systems Design Group
University of Southampton, UK
School of Electronics and Computer Science
Active suspension modelActive suspension model
BMAS, San Jose, CA, 22-23 Sep 2005 9
Electronic Systems Design Group
University of Southampton, UK
School of Electronics and Computer Science
Sprung and Sprung and unsprungunsprung mass equationsmass equations
BMAS, San Jose, CA, 22-23 Sep 2005 10
Electronic Systems Design Group
University of Southampton, UK
School of Electronics and Computer Science
FLCFLC
••Inputs: sprung mass velocity and accelerationInputs: sprung mass velocity and acceleration••Output: actuator forceOutput: actuator force••Three linguistic variables: Three linguistic variables: PositivePositive (P), (P), ZeroZero (Z) and (Z) and NegativeNegative (N)(N)••Fuzzy rules setFuzzy rules set••MaxMax--product inferenceproduct inference••CenterCenter of gravity of gravity defuzzificationdefuzzification
PPPPZZNN
PPZZNNZZ
ZZNNNNPP
VelocityVelocity
NNZZPP
AccelerationAcceleration
BMAS, San Jose, CA, 22-23 Sep 2005 11
Electronic Systems Design Group
University of Southampton, UK
School of Electronics and Computer Science
Shape optimization of fuzzy logic membership functionsShape optimization of fuzzy logic membership functions
••Fuzzy logic membership functionFuzzy logic membership function• Graphical representation of input’s degree of participation in a
fuzzy set• Shapes may affect FLC performance (A. Barr and J. Ray, 1996)• Shape optimization using a GA
BMAS, San Jose, CA, 22-23 Sep 2005 12
Electronic Systems Design Group
University of Southampton, UK
School of Electronics and Computer Science
Shape optimization of fuzzy logic membership functionsShape optimization of fuzzy logic membership functions
BMAS, San Jose, CA, 22-23 Sep 2005 13
Electronic Systems Design Group
University of Southampton, UK
School of Electronics and Computer Science
Integrated GA optimizer in VHDLIntegrated GA optimizer in VHDL--AMS AMS testbenchtestbench
••Integrated hardware system performance optimizer wholly Integrated hardware system performance optimizer wholly implemented in VHDLimplemented in VHDL--AMSAMS
• Active suspension system• FLC• GA optimization
BMAS, San Jose, CA, 22-23 Sep 2005 14
Electronic Systems Design Group
University of Southampton, UK
School of Electronics and Computer Science
Block diagram of one chromosome (VHDLBlock diagram of one chromosome (VHDL--AMS entity) AMS entity)
BMAS, San Jose, CA, 22-23 Sep 2005 15
Electronic Systems Design Group
University of Southampton, UK
School of Electronics and Computer Science
Flow chart of a parallel GAFlow chart of a parallel GA
BMAS, San Jose, CA, 22-23 Sep 2005 16
Electronic Systems Design Group
University of Southampton, UK
School of Electronics and Computer Science
• Evaluation – using peak-to-peak value of xs(t) as fitness• Tournament selection – chromosomes with small xpp are more
likely to be selected to produce offspring• Elitism – artificially inserting the best solution into each new
generation• Arithmetic crossover – generate new offspring for real number
genes• Gene mutation – introduce new solutions into the next population
••VHDLVHDL--AMS finite state machine controls the optimizerAMS finite state machine controls the optimizer
GA features:GA features:
BMAS, San Jose, CA, 22-23 Sep 2005 17
Electronic Systems Design Group
University of Southampton, UK
School of Electronics and Computer Science
Experimental resultsExperimental results••GA optimized membership functions with irregular shapesGA optimized membership functions with irregular shapes
• Velocity
BMAS, San Jose, CA, 22-23 Sep 2005 18
Electronic Systems Design Group
University of Southampton, UK
School of Electronics and Computer Science
Experimental resultsExperimental results••GA optimized membership functions with irregular shapesGA optimized membership functions with irregular shapes
• Acceleration
BMAS, San Jose, CA, 22-23 Sep 2005 19
Electronic Systems Design Group
University of Southampton, UK
School of Electronics and Computer Science
Simulation waveformsSimulation waveforms
BMAS, San Jose, CA, 22-23 Sep 2005 20
Electronic Systems Design Group
University of Southampton, UK
School of Electronics and Computer Science
PeakPeak--toto--peak and RMS values of peak and RMS values of xxss(t)(t)
6.46.436.036.0TrapezoidalTrapezoidal
6.26.235.735.7TriangularTriangular
4.64.628.028.0GA optimizedGA optimized
RMS (mm)RMS (mm)PeakPeak--toto--peak (mm)peak (mm)FLC typesFLC types
BMAS, San Jose, CA, 22-23 Sep 2005 21
Electronic Systems Design Group
University of Southampton, UK
School of Electronics and Computer Science
ConclusionConclusion
•• A novel way to improve FLC performance developed and A novel way to improve FLC performance developed and successfully implemented in an HDLsuccessfully implemented in an HDL•• Novel approach to hardware performance optimisation Novel approach to hardware performance optimisation proposed and implemented proposed and implemented
• Integrated VHDL-AMS optimiser using parallel GA•• New type of FLC with irregular membership functions proposed New type of FLC with irregular membership functions proposed for automotive active suspension systemfor automotive active suspension system
• Superior performance to conventional FLCs with triangular or trapezoidal membership functions
• More than 20% improvement in the peak-to-peak value of sprung mass displacement
BMAS, San Jose, CA, 22-23 Sep 2005 22
Electronic Systems Design Group
University of Southampton, UK
School of Electronics and Computer Science
Thank you!Thank you!
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