| Summary: | Thesis (MScEng)--Stellenbosch Universit, 2004. === ENGLISH ABSTRACT: The requirements regarding the quality of engines and vehicles have increased
constantly, requiring more and more sophisticated engine testing. At the same time,
there is a strong demand to reduce lead time and cost of development. For many years
steady state engine testing was the norm using standard principles of power
absorption. Since the mid 1980's increasing importance has been attached to the
optimisation of transient engine characteristics and the simulation of dynamic real
world driving situations on engine test stands. This has led to the use of bi-directional
DC or AC regenerative dynamometers a practice now known as dynamic engine
testing.
Interfacing a computer with vehicle simulation software to an engine on a dynamic
test stand and using "hardware in the loop" techniques, enables the simulation of real
world driving situations in a test facility. In dynamic engine testing a distinction can
be made between simulation testing and transient testing. In simulation testing the set
point values are predetermined whereas in transient testing a model generates set
point values in real time. Speeds and loads are calculated in real time on the basis of
real time measurements. The model can be in the form of a human or driver
simulation.
This project involved the application of dynamic engine testing to simulating a racing
application. It is termed Real Time Full Circuit Driving Simulation System due to the
simulation of a race car circling a race track, controlled by a driver model and running
the engine on a dynamic test bench in real time using "hardware in the loop"
techniques. By measuring the simulated lap times for a certain engine configuration
on the test bench in real time, it is possible to select the optimal engine set-up for
every circuit. The real time nature of the simulation subjects the engine on the test
bench to similar load and speed conditions as experienced by its racing counterpart in
the race car yielding relevant results. The racing simulation was achieved by finding a
suitable dynamic vehicle model and a three dimensional race track model, developing
a control strategy, programming the software and testing the complete system on a
dynamic test stand.
In order to verify the simulation results it was necessary to conduct actual track
testing on a representative vehicle. A professional racing driver completed three
flying laps of the Killarney racing circuit in a vehicle fitted with various sensors
including three axis orientation and acceleration sensors, a GPS and an engine control
unit emulator for capturing engine data. This included lap time, vehicle accelerations,
engine speed and manifold pressure, an indicator of driver input. The results obtained
from the real time circuit simulation were compared to actual track data and the
results showed good correlation.
By changing the physical engine configuration in the hardware and gear ratios in the
software, comparative capabilities of the system were evaluated. Again satisfactory
results were obtained with the system clearly showing which configuration was best
suited for a certain race track. This satisfies the modem trend of minimizing costs and
development time and proved the value of the system as a suitable engineering tool
for racing engine and drive train optimisation. The Real Time Full Circuit Driving Simulation System opened the door to further
development in other areas of simulation. One such area is the driveability of a
vehicle. By expanding the model it would be possible to evaluate previously
subjective characteristics of a vehicle in a more objective manner. === AFRIKAANSE OPSOMMING: Die vereistes om die kwaliteit van enjins en voertuie te verhoog, word daagliks hoër.
Meer gesofistikeerde enjintoetse word daarom vereis. Terselfdertyd is dit 'n groot
uitdaging om die tydsduur en koste van ontwikkeling so laag as moontlik te hou.
Gestadigde toestand enjintoetse, wat op die prinsiep van krag absorpsie werk, was vir
baie jare die norm. Vanaf die middel tagtigerjare het die optimering van dinamiese
enjinkarakteristieke en die simulasie van werklike bestuursituasies op enjintoetsbanke
van al hoe groter belang geword. Die gevolg was die gebruik van twee rigting wisselof
gelykstroomdinamometers en staan vandag bekend as dinamiese enjintoetsing.
Deur 'n rekenaar met simulasiesagteware aan 'n enjin op 'n dinamiese toetsbank te
koppel, word die moontlikheid geskep om enige werklike bestuursituasies van 'n
voertuig te simuleer in die enjintoetsfasiliteit. Dinamiese enjintoetse kan opgedeel
word in simulasietoetse en oorgangstoestandtoetse. By laasgenoemde genereer 'n
"bestuurdersmodel" die beheerwaardes intyds deur te kyk na intydse metings terwyl
by simulasietoetse die beheerwaardes vooraf bepaal word. Die "bestuurder" kan in die
vorm van 'n persoon of rekenaarsimulasie wees.
Die projek behels die toepassing van dinamiese enjintoetse vir renbaansimulasie en
staan bekend as'n Intydse, Volledige Renbaansisteem weens die simulasie van 'n
renmotor om 'n renbaan, onder die beheer van 'n bestuurdersmodel. Dit geskied
terwyl die enjin intyds op 'n dinamiese enjintoetsbank loop en gekoppel is aan die
simulasie. Deur die intydse, gesimuleerde rondtetye te analiseer, word die
moontlikheid geskep om die enjinkonfigurasie te optimeer vir 'n sekere renbaan. Dit
is bereik deur die keuse van 'n gepaste dinamiese voertuigmodel, 'n driedimensionele
renbaanmodel, ontwikkeling van 'n beheermodel, programmering van die sagteware
en integrasie van die dinamiese enjintoetsstelsel.
Die simulasieresultate verkry is gestaaf deur werklike renbaantoetse. 'n Professionele
renjaer het drie rondtes van die Killarney renbaan voltooi in 'n verteenwoordigende
voertuig wat toegerus was met verskeie sensors o.a. drie as versnellings- en
orientasiesensors, GPS en 'n enjinbeheereenheidemmuleerder vir die verkryging en
stoor van enjindata. Die sensors het data versamel wat insluit rondtetyd,
voertuigversnellings, enjinspoed en inlaatspruitstukdruk. Die korrelasie tussen die
simulasie waardes en werklik gemete data was van hoë gehalte.
Deur die fisiese enjinkonfigurasie te verander in die hardeware en ratverhoudings in
die sagteware, is die vergelykbare kapasiteite van die renbaansimulasie geevalueer.
Die resultate was weer bevredigend en die simulasie was in staat om die beste
enjinkonfigurasie vir die renbaan uit te wys. Dit bevredig die moderne neiging om
koste en ontwikkelingstyd so laag as moontlik te hou. Sodoende is bewys dat die
stelsel waarde in die ingenieurswêreld het. 'n Intydse, Volledige Renbaansisteem die skep die geleentheid vir verdere
ontwikkeling op verskeie terreine van simulasie. Een so 'n veld is die bestuurbaarheid
van 'n voertuig. Deur die model verder te ontwikkel word die moontlikheid geskep
om voorheen subjektiewe karakteristieke van 'n voertuig meer wetenskaplik te
analiseer.
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