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The conventional aftertreatment systems to meet the stringent ULEV-II emission regulation are usually composed of warm-up catalytic converter (WCC) and underfloor catalytic converter (UCC). However, those systems bring high cost, high back pressure, the limit of engine room for package design, and other side effects.[4] The new optimized system needs to solve these problems and to meet ULEV-II emission regulation efficiently. There are many technologies and design parameters in exhaust catalytic converter systems; exhaust manifold structure[9], exhaust gas flow distribution, location of catalytic converter, PM coating technologies[1], substrate characteristics, and volume of catalysts. It is a key factor to make a optimized robust system with those parameters and technologies described. The new optimized exhaust and Integrated Close-coupled Catalytic Converter (ICCC) system can meet ULEV-II regulation and can solve those problems of conventional system by a robust design.

Dynamic characteristics of a line regulator and ratio control valve for an electronic controlled metal belt CVT are investigated by considering the CVT shift dynamics. Based on the dynamic models of the variable force solenoid valve, line regular valve and ratio control valve, simulations are performed and compared with the test results. It is seen that the ratio control valve has a on-off characteristics, which may result in a pressure pulsation in the primary actuator. In addition, the effects of the orifice size at the ratio control valve exhaust port are investigated. It is found that as the orifice size is decreased, magnitude of the residual pressure increases, which ensures the belt clamping force to transmit a large torque during the downshift at the cost of slow shifting. It is expected that the dynamic models of the CVT hydraulic system obtained in this study can be used in design of a prototype CVT

A CVT ratio control algorithm is proposed to improve the engine performance by considering the powertrain response lag. In the CVT powertrain, there exists a response lag, which results from the throttle response, engine torque dynamics, CVT filling time, CVT shift dynamics, and the drive shaft dynamics including the tire. This response lag causes the deviation of the engine operation from the optimal operation line for the minimum fuel consumption. In the CVT ratio control algorithm suggested in this paper, the desired CVT speed ratio is modified from the vehicle velocity, which is estimated after the time delay due to the powertrain response lag. In addition, the acceleration map is constructed to estimate the vehicle acceleration from the throttle pedal position and the CVT ratio. Using the CVT ratio control algorithm and the acceleration map, vehicle performance simulations and experiments are performed to evaluate the engine performance and fuel economy.

An electronic-hydraulic controlled rig type CVT(Continuously Variable Transmission) system was developed and its performance tests were carried out for the optimal operation. As a control algorithm, torque control strategy was suggested considering the engine simulator characteristics. Also, a real time control and operation program called CVTCON consisting of (1)CVT test rig operation, (2) system test, (3)system control and (4)data management modules was developed for the electronic-hydraulic CVT system. By using the CVTCON and the CVT test rig, performance tests were carried out for the optimal operation in case of (1) constant throttle and (2) acceleration driving modes. Experimental results showed that the electronic-hydraulic CVT system and the control software developed in this study made the engine simulator run following the optimal operating line closely, which was set arbitrarily representing the best fuel economy or the maximum power mode.

A regenerative braking algorithm is proposed to make maximum use of regenerative brake for improvement of fuel consumption. In the regenerative braking algorithm, the regenerative torque is determined by considering the motor capacity, battery SOC and vehicle velocity. The regenerative braking force is calculated from the brake control unit by comparing the demanded brake force(torque) and the motor torque available. The wheel pressure that is reduced by the amount of the regenerative braking force is supplied form the hydraulic brake module. In addition, CVT speed ratio control algorithm is suggested during the braking. The optimal operation line is obtained to operate the motor in the most efficient region. It is found from the simulation that the regenerative braking algorithm including the CVT ratio control provides improved fuel economy as much as 4 percent for federal urban driving schedule.

To meet the target of the CO2 regulations, it is mandatory to replace high-carbon fossil fuels with low-carbon fuels. Diesel/Natural Gas (NG) reactivity-controlled compression ignition (RCCI) can reduce CO2 emission, which stratifies two types of fuels with different reactivity. And also, RCCI produces less NOx and particulate matter emissions by reducing the in-cylinder temperature. However, RCCI must still be enhanced in terms of the thermal and combustion efficiencies at low and medium loads. In this work, a modified piston geometry was applied to improve the RCCI combustion. The piston geometry was designed to minimize heat loss and reduce flame quenching in an RCCI engine. Experiments were conducted using a single-cylinder engine with a displacement volume of 1,000 cc. Diesel was directly injected into the cylinder, and NG was fed through the intake port.

A fuzzy logic ratio control algorithm for a metal belt CVT is suggested considering the on-off characteristics of the ratio control valve and the nonlinear characteristics of the CVT shift dynamics. In the fuzzy logic, variable computation time for the error of the ratio and the rate of the error is suggested depending on the velocity of the rate of the CVT ratio. Experimental results show that a desired speed ratio can be achieved at a steady state by the fuzzy logic in spite of the fluctuating primary pressure. In addition, it was found that a faster response and better robustness can be obtained when compared with those of the PID control. It is expected that the ratio control algorithm suggested in this study can be implemented in a prototype CVT.

In this paper, a new formula for calculating primary and secondary thrusts for metal belt CVT's will be proposed considering variation of band tension, block compression and active arc for each of the primary and secondary pulleys. For the secondary thrust, an effective friction coefficient is introduced considering the effect of flange deflection. Nondimensional primary and secondary thrust of the metal belt CVT by the new formula agree well with the experimental results except for low torque range, 0 <λ< 0.2 at a speed ratio i=1.0. The new formula can be used in design of the primary and secondary thrusts control system with sufficient accuracy.

A new fuel economy optimization method for parallel hybrid electric vehicles with continuously variable transmission( CVT) is proposed in this paper. The method maximizes overall system efficiency while meeting desired performances. Firstly, effective specific fuel consumption (ESFC) is defined as effectively consumed fuel per output power-hour from a hybrid propulsion system, in which battery output power is transformed into an equivalent amount of fuel. Hence, hybrid optimal operation line(HOOL) is derived based on ESFC as optimal operation line(OOL) is found based on specific fuel consumption( SFC) in a conventional internal combustion engine(ICE) vehicle with CVT. From HOOL, optimal combinations of control variables, CVT gear ratio, motor torque and engine throttle, are obtained versus vehicle velocity, battery state of charge and required power. A simulation study with the proposed optimization method is performed to prove its validity.