Jeonghoon Song

Model development and control methodology of a new electric power steering system

Abstract In this study, a new column-type electric power steering (EPS-TT) system is investigated. The remarkable features of this EPS-TT system are its opto-isolated torque sensor, which is used to make steering torque measurements, and its assist torque control methodology, which uses a unidirectional motor and two clutches. Thus it does not require a complicated motor drive system that consumes a large amount of electrical energy when the direction of rotation is reversed. This allows the new system to use a smaller and simpler assist motor. A full steering system model and a simplified model are developed to evaluate the EPS-TT system. A full car model is also used to investigate the vehicle response. A map-based control method and a proportional-integral-derivative control algorithm are designed to control the EPS-TT system. Various sinusoidal inputs are applied to the system and the resulting performance is analysed. The results show that the performance achieved by the EPS-TT system is similar to that of a conventional EPS system across the frequency domain. The results for the full steering system model are similar to those for the simplified model, but the vehicle response is slightly different. The map-based controller provided good performance without affecting the stability or controllability of the vehicle.

A study on an anti-lock braking system controller and rear-wheel controller to enhance vehicle lateral stability

Abstract This paper presents a mathematical vehicle model that is designed to analyse and improve the dynamic performance of a vehicle. A wheel slip controller for anti-lock braking system (ABS) brakes is formulated using a sliding mode controller and a proportional-integral-derivative (PID) controller for rear wheel steering is also designed to enhance the stability, steerability, and driveability of the vehicle during transient manoeuvres. The braking and steering performances of controllers are evaluated for various driving conditions, such as straight and J-turn manoeuvres. The simulation results show that the proposed full car model is sufficient to predict vehicle responses accurately. The developed ABS reduces the stopping distance and increases the longitudinal and lateral stability of both two-and four-wheel steering vehicles. The results also demonstrate that the use of a rear wheel controller as a yaw motion controller can increase its lateral stability and reduce the slip angle at high speeds.

Performance evaluation of traction control systems using a vehicle dynamic model

Abstract This study evaluates traction control systems (TCSs) composed of either a wheel slip controller or a throttle valve controller, or an integrated controller of both systems. The dynamic characteristics of a vehicle and a TCS are evaluated using a proposed full car model that can simulate the responses of both front-wheel-drive and four-wheel-drive vehicles. A driver model is also modified to control the vehicle during tests on a road with split Coefficients. The results show that the brake TCS provides more acceleration on uniform slippery and split roads, but the yaw rate and the lateral off set are larger than those obtained when an engine TCS is used. When the vehicle is cornering and accelerating with the brake or engine TCS, understeer or oversteer occur, depending on the driving conditions. An integrated TCS prevents most of these problems and improved the stability and controllability of the vehicle. Four-wheel-drive vehicles exhibit better traction control than two-wheel-drive vehicles, but their steerability is reduced.

Flame kernel formation and propagation modelling in spark ignition engines

Abstract One-dimensional, time-dependent numerical simulations of flame kernel growth produced by a spark in a combustible gasoline-air mixture are presented. This model accounts for the fundamental properties of the ignition system, the combustible mixture and flow fleld. Submodels representing the cylinder pressure and temperature, heat transfer to the cylinder wall and spark plug electrodes or ambient air, effects of the residual gas and so on. In addition, to research the effects of ignition energy, two kinds of ignition systems are used. The results show that the increased breakdown energy enlarges the plasma radius, which derives faster development of the initial flame kernel. The heat transfers to the electrodes and the cylinder wall also affect the growth of the kernel. These results appear to be coherent with previous experimental visualizations. The simulations are validated by different engine running conditions, for example air-fuel ratio, spark advance, engine speed and intake manifold pressure.

Application of a sliding mode control to anti-lock brake system

This paper presents application method of a sliding mode wheel slip controller for ABS that improves the vehicle response and increases the safety on slippery road. Sliding mode wheel slip controller receives wheel slip ratio, vehicle velocity, longitudinal acceleration, and tire forces from vehicle model to generate braking pressures. In general, two solenoid valves, so called normal open and normal close valves, have been used to generate the hydraulic pressure necessary to generate proper braking force. In this paper, the valve operating method is proposed to implement the sliding mode control output in hydraulic unit of the ABS. The control performance is verified by using a HILS System that has a vehicle braking system controlled with On/Off solenoid valves.

Nonlinear observer and robust controller design for enhancement of vehicle lateral stability

This paper describes the design of a sliding mode controller to control wheel slip. A yaw motion controller (YMC), which uses a PID control method, is also proposed for controlling the brake pressure of the rear and inner wheels to enhance lateral stability. It induces the yaw rate to track the reference yaw rate, and it reduces a slip angle on a slippery road. A nonlinear observer is also developed to estimate the vehicle variables difficult to measure directly. The braking and steering performances of the anti-lock brake system (ABS) and YMC are evaluated for various driving conditions, including straight, J-turn, and sinusoidal maneuvers. The simulation results show that developed ABS reduces the stopping distance and increases the longitudinal stability. The observer estimates velocity, slip angle, and yaw rate very well. The results also reveal that the YMC improves vehicle lateral stability and controllability when various steering inputs are applied. In addition, the YMC enhances the vehicle safety on a split-μ road.

Comparison of model reference and map based control method for vehicle stability enhancement

A map based controller method to improve a vehicle lateral stability is proposed in this study and compared with the conventional method, a model referenced controller. A model referenced controller to determine compensated yaw moment uses the sliding mode method, but the proposed map based controller uses compensated yaw moment map acquired by vehicle stability analysis. Vehicle stability region is calculated by topological method based on trajectory reversal method. A two degree-of-freedom vehicle model and Pacejkas tire model used to evaluate the proposed map based controller. The control performance of two methods are compared under various road conditions and driving inputs. Model referenced control method needs control input to satisfies linear reference model, and then generates unnecessary tire lateral forces, it may lead to worse performance than uncontrolled vehicle with step steer input in low friction road. As the results of simulation, map based controller seems to be better than model referenced in the viewpoint of stability.

Development of a Prototype New Electric Power Steering (EPS) System

This study proposes and validates a new column type electric power steering system (EPS-TT). It is driven by a uni-directional motor and two electro-magnetic clutches. The assist motor produces assist torque in only one direction and two clutches transmit the torque to the column of steering system in either left or right direction with respect to the steering input. A full order and a reduced order models are developed to evaluate the EPS-TT. Models are also used to investigate the vehicle responses. A PID control logic is designed to control the torque of the assist motor. A driver model is applied to the system and the resulting performances are analyzed. The results show that the performances of the full order model are similar to those of reduced order model. The results also prove that the performances achieved by the EPS-TT are improved compared to those of a conventional EPS-TT across the frequency domain.

Experimental Study of Ignition of a Gasoline–Air Mixture in a Constant‐Volume Combustion Chamber

The characteristics of flame‐kernel development in a premixed gasoline–air mixture in a cylindrical constant‐volume combustion chamber are measured. The experiments are performed with an initial temperature of 393 K, pressure of 6 bar, and equivalence ratio Φ = 0.8 with the use of various ignition systems and spark plugs. The schlieren pictures of the process are presented, and the measured results for flame velocity, heat‐release rate, and mass fraction of the burnt fuel are analyzed.

An Experimental and Mathematical Study on the Effects of Ignition Energy and System on the Flame Kernel Development

A constant volume combustion chamber is used to investigate the flame kernel development of gasoline air mixtures under various ignition systems, ignition energies and spark plugs. Three kinds of ignition systems are designed and assembled, and the ignition energy is controlled by the variation of the dwell time. Several kinds of spark plugs are also tested. The velocity of flame propagation is measured by a laser deflection method, and the combustion pressure is analyzed by the heat release rate and the mass fraction burnt. The results represent that as the ignition energy is increased by enlarging either dwell time or spark plug gap, the heat release rate and the mass fraction burnt are increased. The electrodes materials and shapes influence the flame kernel development by changing he transfer efficiency of electrical energy to chemical energy. The diameter of electrodes also influences the heat release rate and the burnt mass fraction.