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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Transactions of the Korean Society of Automotive Engineers
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Journal DOI :
The Korean Society of Automotive Engineers
Editor in Chief :
Volume & Issues
Volume 14, Issue 6 - Nov 2006
Volume 14, Issue 5 - Sep 2006
Volume 14, Issue 4 - Jul 2006
Volume 14, Issue 3 - May 2006
Volume 14, Issue 2 - Mar 2006
Volume 14, Issue 1 - Jan 2006
Selecting the target year
A Study on the Characteristics of Mixture Formation and Combustion in the Premixed Charge Compression Ignition Engine
Kim, Hyung-Min ; Ryu, Jea-Duk ; Lee, Ki-Hyung ;
Transactions of the Korean Society of Automotive Engineers, volume 14, issue 3, 2006, Pages 1~9
Recently, there has been an interest in premixed diesel engines as it has the potential of achieving a more homogeneous and leaner mixture close to TDC compared to conventional diesel engines. Because this concept reduced NOx and smoke emissions simultaneously. Early studies are shown that in a HCCI(Homogeneous Charge Compression Ignition) engine, the fuel injection timing and intake air temperature affect the mixture formation. The purpose of this study is to investigate characteristics of combustion and mixture formation according to injection timing and intake air temperature in a common rail direct injection type HCCI engine using an early injection method called the PCCI(Premixed Charge Compression Ignition). From this study, we found that the fuel injection timing and intake air temperature affect the mixture formation and in turn affects combustion in the PCCI engine.
A Study on Characteristics of Performance and
Emissions in Turbo Intercooler ECU Common-rail Diesel Engines with a Combined Plasma EGR System
Bae, Myung-Whan ; Ku, Young-Jin ; Lee, Bong-Sub ;
Transactions of the Korean Society of Automotive Engineers, volume 14, issue 3, 2006, Pages 10~21
The aim in this study is to develop the combined EGR system with a non-thermal plasma reactor for reducing exhaust emissions and improving fuel economy in turbo intercooler ECU common-rail diesel engines. At the first step, in this paper, the characteristics of performance and
emissions under four kinds of engine loads are experimentally investigated by using a four-cycle, four-cylinder, direct injection type, water-cooled turbo intercooler ECU common-rail diesel engine with a combined plasma exhaust gas recirculation(EGR) system operating at three kinds of engine speeds. The EGR system is used to reduce
emissions, and the non-thermal plasma reactor and turbo intercooler system are used to reduce THC emissions. The plasma system is a flat-to-flat type reactor operated by a plasma power supply. The fuel is sprayed by pilot and main injections at the variable injection timing between BTDC
according to experimental conditions. It is found that the specific fuel consumption rate with EGR is increased, but the fuel economy is better than that of mechanical injection type diesel engine as compared with the same output. Results show that
emissions are decreased, but THC emissions are increased, as the EGR rate is elevated.
and THC emissions are also slightly decreased as the applied electrical voltage of the non-thermal plasma reactor is elevated. Thus one can conclude that the influence of EGR in
and THC emissions is larger than that of the non-thermal plasma reactor, but THC emissions are greatly influenced by the non-thermal plasma reactor as the EGR rate is elevated.
Comparative Crashworthiness Assessment of the ULSAB-AVC Model with Advance High Strength Steel and with Low Strength Steel
Yoon, Jong-Heon ; Huh, Hoon ; Kim, Se-Ho ; Kim, Hong-Kee ; Park, Seung-Ho ;
Transactions of the Korean Society of Automotive Engineers, volume 14, issue 3, 2006, Pages 22~27
As the regulation and assessment program for safety of passengers become stringent, automakers are required to develop lighter and safer vehicles. In order to fulfill both requirements which conflict with each other, automobile and steel companies have proposed the application of AHSS(Advance High Strength Steel) such as DP, TRIP and martensite steel. ULSAB-AVC model is one of the most remarkable reactions to offer solutions with the use of steel for the challenge to improve simultaneously the fuel efficiency, passenger safety, vehicle performance and affordability. This paper is concerned with the crash analysis of ULSAB-AVC model according to the US-SINCAP in order to compare the effectiveness between the model with AHSS and that with conventional steels. The crashworthiness is investigated by comparing the deformed shape of the cabin room, the energy absorption characteristics and the intrusion velocity of a car.
Development of a Real-time Driving Simulator for ACC(Adaptive-Cruise-Control) Performance Evaluation
Han, Dong-Hoon ; Yi, Kyong-Su ;
Transactions of the Korean Society of Automotive Engineers, volume 14, issue 3, 2006, Pages 28~34
An ACC driving simulator is a virtual reality device which designed to test or evaluate vehicle control algorithm. It is designed and built based on the rapid control prototyping(RCP) concept. Therefore this simulator adopt RCP tools to solve the equation of a vehicle dynamics model and control algorithm in real time, rendering engine to provide real-time visual representation of vehicle behavior and CAN communication to reduce networking load. It can provide also many different driving test environment and driving scenarios.
A Study on the Effect of Exhaust System Configuration on Scavenging Characteristic of a Four-Cylinder Turbocharged Diesel Engine
Jeong, Soo-Jin ; Chung, Jae-Woo ; Kang, Woo ; Kim, Woo-Seung ;
Transactions of the Korean Society of Automotive Engineers, volume 14, issue 3, 2006, Pages 35~43
A four-stroke four-cylinder turbocharged diesel engine can be fitted with various types exhaust system. In this paper, the impacts of exhaust system design on scavenging performance and wave action characteristic during valve overlap are investigated by using one-dimensional gas dynamic code. This work shows that a huge reflected exhaust pressure waves which reaches the exhaust port during valve overlap period is crucial design factor which determines quality and quantity of the fresh charge. Hence pressure wave that reaches the exhaust port of the cylinder during the valve overlap sequence should be weakened for good scavenging performance. This paper describes advantages and disadvantages of the various exhaust systems applied to a turbocharged and intercooled 4-cylinder diesel engine system in terms of scavenging efficiency and engine performance. To verify the computational results, experimental comparison has also performed.
A Study on the Process Development of Mono Steel Forged Piston for Diesel Engine
Yeom, Sung-Ho ; Nam, Kyoung-O ; Hwang, Doo-Soon ; Kwon, Hyuk-Sun ; Hong, Sung-In ;
Transactions of the Korean Society of Automotive Engineers, volume 14, issue 3, 2006, Pages 44~50
The mono steel forged piston was improved a mechanical strength of an aluminum piston and reduced the weight of a articulated piston. The mono steel forged piston was composed of forged crown part and forged skirt part and was completed by friction welding process of two forged parts. Forging process analysis and friction welding analysis was done by finite element simulation using numerical package DEFORM. The preform shape and the initial billet dimension were decided by maximum stress of the die, amount of the flash and filling of die. The upset length of friction welding variable was decided by the shape of the flash that was created by friction welding analysis. Through this research, we developed a forging process of the mono steel forged piston, and decided the design variables of friction welding.
Contact Pressure Analysis of a Windshield Wiperblade
Lee, Byoung-Soo ; Shin, Jin-Yong ;
Transactions of the Korean Society of Automotive Engineers, volume 14, issue 3, 2006, Pages 51~57
The contact pressure distribution between a rubber wiper blade and a glass windshield is a major factor for wiping performance. A modeling and simulation method has been developed to forecast the contact pressure distribution on a wiper blade. For modeling multi-body dynamics of an wiper linkage system and flexible nature of wiper blade, ADAMS and ADAMS/flex are employed. A simulation study has been also conducted to obtain contact pressure distribution. Comparison between simulation and measurement is provided to ensure fidelity of the model and the simulation method.
Fuzzy Logic Based Active Ventilation System with Security Function
Jung, Byung-Chan ; Kim, Hun-Mo ;
Transactions of the Korean Society of Automotive Engineers, volume 14, issue 3, 2006, Pages 58~67
In this paper, fuzzy logic based active ventilation system with security function is proposed and implemented. We can easily experience the situation that inner air is so hot to get start immediately after parking at summer day. Hot temperature is enough to explode a gas lighter or to suffocate a little chid. Proposed system has 1 blower and 2 axial fans to ventilate inner air. Based on the fuzzy logic, speed and direction of each fan are controlled. In addition to controlling fans, controller put down windows and adjust the periods of open time. In order to prevent the theft and security problems, IR sensors are used to detect objects. On detecting objects, controller put up windows. Experimental result shows that implemented system can be effectively ventilate inner air and reduce temperature. Proposed system can be applicable to commercial automobiles.
The Durability Performance Evaluation of Automotive Components in the Virtual Testing Laboratory
Kim, Gi-Hoon ; Kang, Woo-Jong ; Kim, Dae-Sung ; Ko, Woong-Hee ; Lim, Jae-Yong ;
Transactions of the Korean Society of Automotive Engineers, volume 14, issue 3, 2006, Pages 68~74
The evaluation of durability performance in Virtual Testing Laboratory(VTL) is a new concept of vehicle design, which can reduce the automotive design period and cost. In this study, the multibody dynamics model of a car is built with a reverse engineering design. Hard points and masses of components are measured by a surface scanning device and imported into CAD system. In order to simulate the non-linear dynamic behavior of force elements such as dampers and bushes, components and materials are tested with specialized test equipments. An optimized numerical model for the damping behavior is used and the hysteresis of bush rubber is considered in the simulation. Loads of components are calculated in VTL and used in the evaluation of durability performance. In order to verify simulation results, loads of components in the vehicle are measured and durability tests are performed.
A Study on Heavy-Duty Diesel Engine Performance with a CR-DPF and Cooled-EGR
Moon, Byung-Chul ; Oh, Yong-Suk ; Oh, Sang-Ki ; Kang, Kum-Won ; Ahn, Kyun-Jae ;
Transactions of the Korean Society of Automotive Engineers, volume 14, issue 3, 2006, Pages 75~80
Since air pollution has become a globally critical issue and exhaust emissions from automobiles cause a major source of air pollution, many countries including advanced countries have stipulated stringent emission regulations. Particularly in diesel vehicles, NOx and particulate matters exhaust in significant amounts even though diesel vehicles provide merits in aspects of higher thermal efficiency and lower
. To reduce Particulate matters and NOx, after-treatment technology such as filter trap, oxidation catalysts and EGR has been applied. This test was conducted on the effect of continuous regeneration diesel particulate filter and cooled-EGR, and 15ppm low sulfur diesel was used as a test fuel. Exhaust emissions, PM, NOx, CO, HC and Soots were measured and compared under D-13 and D-3 modes.
Mechanical Loss Model for a Metal Belt CVT
Ryu, Wan-Sik ; Kim, Pil-Gu ; Kim, Hyun-Soo ;
Transactions of the Korean Society of Automotive Engineers, volume 14, issue 3, 2006, Pages 81~87
In this paper, the belt-pulley mechanical loss is investigated. A bondgraph model for the mechanical loss is developed from the viewpoint of the power flow by assuming that all power losses are attributed to the torque loss. The mechanical loss model consists of transient and steady state part. The coefficients of the power loss model are obtained from the experiments. It is found from the simulations and experiments that the steady state loss depends on the line pressure, input torque and rotational speed while the transient loss depends on the rotational speed, shift speed and the inertial torque.
An Effect of Shot Peening on Corrosion Fatigue Crack Growth of Suspension Material
Park, Keyung-Dong ; An, Jae-Pil ;
Transactions of the Korean Society of Automotive Engineers, volume 14, issue 3, 2006, Pages 88~94
The compressive residual stress, which is induced by shot peening process, has the effect of increasing the intrinsic fatigue strength of surface and therefore would be beneficial in reducing the probability of fatigue damage. However, the effect of shot peening in corrosion environment was not known. In this study, investigated is the effect of shot peening on corrosion fatigue crack growth of SAE 5155 steel immersed in 6%
solution and corrosion characteristics with considering fracture mechanics. The results of the experimental study corrosion fatigue characteristics of SAE 5155 are as follows; the fatigue crack growth rate of the shot peening material was lower than that of the non-peening material. And fatigue life shows more improvement in the shot peening material than in non-peening material. This is due to the compressive residual stress of surface increases resistance of corrosion fatigue crack propagation. It is assumed that the shot peening process improve corrosive resistance and mechanical property.
A Study on Measurements of PM Size in a Single Cylinder Common-rail Diesel Engine Exhaust using LII Method
Chun, Hong-Sik ; Kim, Hui-Jun ; Ryu, Hoon-Chul ; Park, Jong-Il ; Hahn, Jae-Won ; Chun, Kwang-Min ;
Transactions of the Korean Society of Automotive Engineers, volume 14, issue 3, 2006, Pages 95~102
Recently particulate matter(PM) emission regulations are becoming more strict for diesel engines. There is increasing interest for measuring not only concentration but also size of the particles. Laser-induced incandescence (LII) has emerged as a promising technique for measuring particle volume fraction and size. In this study, the Simple Time Resolved-LII method was applied to exhaust of Ethylene diffusion flame and diesel engine exhaust for measuring soot and PM size. The particle size data from LII technique were calibrated using Field Emission Scanning Electron Microscope(FE-SEM) and Transmission Electron Microscope(TEM) photographs. In diesel engine experiments for particle size measurement, results from LII measurement are in a good agreement with those from TEM photograph, and difference between two measurements was less than 16%.
The Effects of Fuel Temperature on the Spray and Combustion Characteristics of a DISI Engine
Moon, Seok-Su ; Abo-Serie, Essam ; Bae, Choong-Sik ;
Transactions of the Korean Society of Automotive Engineers, volume 14, issue 3, 2006, Pages 103~111
The spray behavior of direct-injection spark-ignition(DISI) engines is crucial for obtaining the required mixture distribution for optimal engine combustion. The spray characteristics of DISI engines are affected by many factors such as piston bowl shape, air flow, ambient temperature, injection pressure and fuel temperature. In this study, the effect of fuel temperature on the spray and combustion characteristics was partially investigated for the wall-guided system. The effect of fuel temperature on the fan spray characteristics was investigated in a steady flow rig embodied in a wind tunnel. The shadowgraphy and direct imaging methods were employed to visualize the spray development at different fuel temperatures. The microscopic characteristics of spray were investigated by the particle size measurements using a phase Doppler anemometry(PDA). The effect of injector temperature on the engine combustion characteristics during cold start and warming-up operating conditions was also investigated. Optical single cylinder DISI engine was used for the test, and the successive flame images captured by high speed camera, engine-out emissions and performance data have been analyzed. This could give the way of forming the stable mixture near the spark plug to achieve the stable combustion of DISI engine.
An Experimental Study on Relationship of the Engine rpm and the Strength of Electro-magnetic Waves in the Engine Room
Choe, Gwang-Je ;
Transactions of the Korean Society of Automotive Engineers, volume 14, issue 3, 2006, Pages 112~118
In this paper, we presented experimental data of the strength of the electro-magnetic waves in the engine room of automobiles. Measured frequency ranges are
. Experimental studies are conducted by measuring the radiated power of the frequency spectrum for above frequency bands. The
dipoles used for measurement are fabricated to comply with the COMMISSION DIRECTIVE 95/54EC. Experimental results confirm that the level of radiated power in the engine room at idling rpm is about 3dB higher than that of 1500rpm.
Fuel Consuming Reduction by Power Steering System Optimization
Jo, Sok-Hyun ; Nam, Kyung-Woo ; Kwon, O-Sung ;
Transactions of the Korean Society of Automotive Engineers, volume 14, issue 3, 2006, Pages 119~124
This paper deals with energy-saving effort in the hydraulic power steering system. Commonly, the hydraulic power steering systems are used for passenger cars and the reduction of pumping loss under non-steering condition is important to improve fuel economy. Experiments and simulations are performed simultaneously to examine the main factors to reduce the pumping loss-pressure loss and flow rate of the power steering systems. Fuel economy effect of the optimal design of power steering system is verified by vehicle test - more than 1% fuel consuming reduction is attained.
A Study of
Adsorption/Desorption Characteristics in the Monolithic
Wang, Tae-Joong ; Baek, Seung-Wook ; Jung, Myung-Geun ; Yeo, Gwon-Koo ;
Transactions of the Korean Society of Automotive Engineers, volume 14, issue 3, 2006, Pages 125~132
Transient kinetics of
adsorption/desorption and of SCR(selective catalytic reduction) of NO with
were studied over vanadium based catalysts, such as
. In the present catalytic reaction process, NO adsorption is neglected while
is strongly chemisorbed on the catalytic surface. Accordingly, it is ruled out the possibility of a reaction between strongly adsorbed
and NO species in line with the hypothesis of an Eley-Rideal mechanism. The present kinetic model assumes; (1) non-activated
adsorption, (2) Temkin-type
coverage dependence of the desorption energy, (3) non-linear dependence of the SCR reaction rate on the
surface coverage. Thus, the surface heterogeneity for adsorption/desorption of
is taken into account in this model. The present study extends the pure chemical kinetic model based on a powdered-phase catalytic system to the chemico-physical one applicable to a realistic monolith reactor.
A Study of Low Cycle Fatigue Characteristics of 11.7Cr-1.1Mo Heat Resisting Steel with Mean Stress
Hong, Sang-Hyuk ; Hong, Chun-Hyi ; Lee, Hyun-Woo ;
Transactions of the Korean Society of Automotive Engineers, volume 14, issue 3, 2006, Pages 133~141
The Low cycle fatigue behavior of 11.7Cr-1.1Mo heat-resisting steel has been investigated under strain-controlled conditions with mean stresses at room temperature and
. For the tensile mean stress test, the initial high tensile mean stress generally relaxed to zero at room temperature, however, at
initial tensile mean stress relaxed to compressive mean stress. Low cycle fatigue lives under mean stress conditions are usually correlated using modifications to the strain-life approach. Based on the fatigue test results from different stain ratio of -1, 0, 0.5, and 0.75 at room temperature and
, the fatigue damage of the steel was represented by using cyclic strain energy density. Total strain energy density considering mean stress indicated well better than not considering mean stress at
. Predicted fatigue life using Smith-Watson-Topper's parameter correlated fairly well with the experimental life at
In-Cylinder Intake Flow Characteristics according to Inlet Valve Angle
Ohm, In-Yong ; Pak, Chan-Jun ;
Transactions of the Korean Society of Automotive Engineers, volume 14, issue 3, 2006, Pages 142~149
A PIV(Particle Image Velocimetry) was applied to measure in-cylinder velocity field according to inlet valve angle during intake stroke. Two engines, one is conventional DOHC 4 valve and the other is narrow valve angle, were used to compare real intake flow. The results show that the intake flow pattern of conventional engine is more complicated than that of narrow angle one in horizontal plane and the vertical component of in-cylinder flow is rapidly decayed at the end stage of intake. On the other hand, the flow pattern of narrow angle one is relatively well arranged in horizontal plane and the vertical velocity component remains so strongly that forms large-scale strong tumble. Two engines also form commonly three tumble; two are small and bellow the intake valve and one is large-scale. The center of large scale tumble moves to bottom of cylinder as the vertical velocity increases.
The Effect of Auxiliary use LPG on the Performance of a D.I. Diesel Engine
Bang, Joong-Cheol ;
Transactions of the Korean Society of Automotive Engineers, volume 14, issue 3, 2006, Pages 150~156
Recently, the tightening of available crude oil supplies has resulted in the development of intense consciousness for saving fuels. At the same time, some research programs have been launched to secure substitute energy sources for petroleum-derived fuels, and to reduce unhealthy products, such as CO, HC, NOx and smoke. To keep up with these trends in society, the regulation affecting diesel smoke may be greatly strengthened in a short time. In not too distant future, LPG and LNG are the most hopeful substitute fuels for automobile and truck uses. This paper discusses how to use such gaseous fuels in a diesel engine, and how to find out introducing these fuels affect the engine performance.
A Study on the Plasma Nitriding Application for the Durability Improvement of the Exhaust Decoupler
Hur, Deog-Jae ; Kim, Sang-Sik ; Chung, Tae-Jin ; Kim, Do-Hoon ;
Transactions of the Korean Society of Automotive Engineers, volume 14, issue 3, 2006, Pages 157~163
This paper described the process of improving durability performance of the exhaust decoupler by the plasma nitriding. The properties of plasma nitriding treatment of AIS1304 stainless steel were tested using specimens before applying plasma nitriding to a mesh ring. In order to analyses the effect of plasma nitriding treatment on the mechanical properties, SEM(Scanning Electron Microscopes), roughness and hardness tester were used. Based on specimen plasma nitriding, we could find appropriate condition for application to the mesh ring of decoupler. To confirm the improved durability performance, we compared the number of cycles, which reaches to fracture, of the nitrided decoupler and that of the unnitrided decoupler by the bending cyclic test. In this test, the durability and wear resistance of the mesh ring are significantly improved by plasma nitriding treatment.
Design Modification of Bearing Walkout of Water Pump by a Finite Element Analysis
Yang, Chull-Ho ; Han, Moon-Sik ;
Transactions of the Korean Society of Automotive Engineers, volume 14, issue 3, 2006, Pages 164~169
A systematic methodology has been proposed to establish a reliable design of water pump system. A simplified steady-state dynamic model of water pump system has been developed to study the response of water pump system to the dynamic load mainly due to the run-out and unbalance. Design modifications are needed to strengthen the structural integrity of existing designs. Increasing the natural frequency of system is pursued to prevent a resonance from occurring in the engine excitation range. A computational reliability methodology combined with finite element analysis is used to identify the most significant factor affecting the system performance. This method considered influence of design control parameters for the performance of design. By including control factors to the system model in a systematic way, more reliable design is expected.
Lean Operation Characteristics of a Spark Ignition Engine with Reformed Gas Addition
Oh, Seung-Mook ; Kim, Chang-Up ; Kang, Kern-Yong ; Choi, Young ;
Transactions of the Korean Society of Automotive Engineers, volume 14, issue 3, 2006, Pages 170~177
Hydrogen can extend the lean misfire limit to a large extent when it is mixed with conventional fuels for a spark ignition engine. In this study, hydrogen-enriched gaseous fuels by reforming process were simulated according to their proportions of
gases. Pure hydrogen and two different hydrogen-enriched gaseous mixtures(A-, B-composition) were tested for their basic effects on the engine performances and emissions in a single cylinder research engine. A- and B-composition showed different results from 100%
addition because air/fuel mixtures were more diluted by their additions. Even though the energy fraction of reformed gases was increased, combustion stabilities and lean misfire limits were not sensitively improved. It means that combustion augmentation by
addition was offset by the charge dilution of
. In addition, the low flammability of CO gas deteriorated thermal efficiencies. CO emission was drastically increased with B-composition which included higher CO component. However,
was reduced as energy fraction(
) rised except for the case of 100%
and was, for A-composition, lowered to a factor of ten when compared with that of
addition. HC emissions were largely influenced by
due to misfire and partial burns.
Combustion Characteristics of Gasoline HCCI Engine with DME as an Ignition Promoter
Yeom, Ki-Tae ; Jang, Jin-Young ; Bae, Choong-Sik ;
Transactions of the Korean Society of Automotive Engineers, volume 14, issue 3, 2006, Pages 178~185
This paper investigates the steady-state combustion characteristics of the Homogeneous charge compression ignition(HCCI) engine with variable valve timing(VVT) and dimethyl ether(DME) direct injection, to find out its benefits in exhaust gas emissions. HCCI combustion is an attractive way to lower carbon dioxide(
), nitrogen oxides(NOx) emission and to allow higher fuel conversion efficiency. However, HCCI engine has inherent problem of narrow operating range at high load due to high in-cylinder peak pressure and consequent noise. To overcome this problem, the control of combustion start and heat release rate is required. It is difficult to control the start of combustion because HCCI combustion phase is closely linked to chemical reaction during a compression stroke. The combination of VVT and DME direct injection was chosen as the most promising strategy to control the HCCI combustion phase in this study. Regular gasoline was injected at intake port as main fuel, while small amount of DME was also injected directly into the cylinder as an ignition promoter for the control of ignition timing. Different intake valve timings were tested for combustion phase control. Regular gasoline was tested for HCCI operation and emission characteristics with various engine conditions. With HCCI operation, ignition delay and rapid burning angle were successfully controlled by the amount of internal EGR that was determined with VVT. For best IMEP and low HC emission, DME should be injected during early compression stroke. IMEP was mainly affected by the DME injection timing, and quantities of fuel DME and gasoline. HC emission was mainly affected by both the amount of gasoline and the DME injection timing. NOx emission was lower than conventional SI engine at gasoline lean region. However, NOx emission was similar to that in the conventional SI engine at gasoline rich region. CO emission was affected by the amount of gasoline and DME.
A Study on Probabilistic Response-time Analysis for Real-time Control Systems
Han, Jae-Hyun ; Shin, Min-Suk ; Hwang, In-Yong ; SunWoo, Myoung-Ho ;
Transactions of the Korean Society of Automotive Engineers, volume 14, issue 3, 2006, Pages 186~195
In real-time control systems, the traditional timing analysis based on worst-case response-time(WCRT) is too conservative for the firm and soft real-time control systems, which permit the maximum utilization factor greater than one. We suggested a probabilistic analysis method possible to apply the firm and soft real-time control systems under considering dependency relationship between tasks. The proposed technique determines the deadline miss probability(DMP) of each task from computing the average response-time distribution under a fixed-priority scheduling policy. The method improves the predictable ability forthe average performance and the temporal behavior of real-time control systems.