Kyongsu Yi

Nonlinear brake control for vehicle CW/CA systems

A brake control law for vehicle collision warning/collision avoidance (CW/CA) systems has been proposed in the paper. The control law has been designed for optimized safety and comfort. A solenoid-valve-controlled hydraulic brake actuator system for the CW/CA systems has been investigated. A nonlinear computer model and a linear model of the hydraulic brake actuator system have been developed. Both models were found to represent the actual system with good accuracy. Uncertainties in the brake actuator model have been considered in the design of the control law for the robustness of the controller. The effects of brake control on CW/CA vehicle response has been investigated via simulations. The simulations were performed using a complete nonlinear vehicle model. The results indicate that the proposed brake control law can provide the CW/CA vehicles with an optimized compromise between safety and comfort.

An investigation into differential braking strategies for vehicle stability control

Abstract This paper presents a differential braking strategy for vehicle stability control. The controller has been designed using a three-degree-of-freedom (3DOF) yaw plane vehicle model, and a simulation study has been performed using a full non-linear three-dimensional vehicle model. The brake control inputs have been directly derived from the sliding control law based on a 3DOF yaw plane vehicle model with differential braking. The performance of the sliding controller has been compared with that of the direct yaw moment controller (DYC). Simulation results have shown that the proposed controller can provide a vehicle with superior performance with respect to brake actuation and system smoothness and can minimize the acceleration and jerk without compromising stability at high speed and large steering angle input.

Estimation of Turbine Torque of Automatic Transmissions Using Nonlinear Observers

This paper presents an adaptive sliding observer-based method for estimation of turbine torque. The estimated turbine torques can be used for the closed-loop control of vehicle power train for better shift quality. A sliding observer structure including saturation functions and boundary layers is applied to adapt torque converter parameters. The proposed method has been investigated via simulation and laboratory experimental studies. It has been shown via simulation and experiments that the proposed methodology is promising for the estimation of turbine torques since it uses only inexpensive angular velocity measurements and is not sensitive to parametric uncertainties.

Vehicle-to-vehicle distance and speed control using an electronic-vacuum booster

A vehicle-to-vehicle distance and speed control algorithm using an electronic-vacuum booster (EVB) has been presented. The EVB has been used as a brake actuator. The performance characteristics of the EVB have been investigated via computer simulations and experiments. Mathematical models of the electronic-vacuum booster developed in this study and a two-state dynamic engine model have been used in the simulations. Linear optimal control theory has been used to design optimal acceleration for the vehicle-to-vehicle distance control. A throttle/brake control law has been proposed. The throttle/brake controller forces the vehicle acceleration to converge to the desired acceleration. It has been shown via the simulations and vehicle tests that the control law can provide a vehicle equipped with the electronic-vacuum booster with good distance control performance in both high speed and low speed stop and go driving situations.

A driver-adaptive stop-and-go Cruise control strategy

A driver-adaptive stop-and-go (SG) cruise control strategy is proposed. The control strategy has been designed to incorporate the driving characteristics of the human drivers and to achieve natural vehicle behavior of the SG controlled vehicle that would feel comfortable to the human driver. Vehicle following characteristics of the SG vehicle with the driving behavior parameter estimation have been investigated using real-world vehicle driving test data and a validated simulation package. The vehicle following behavior of the SG vehicle with the adaptive control strategy is quite close to that of manual driving. It can be expected that a more natural and more comfortable vehicle behavior would be achieved by the use of the driver-adaptive SG control strategy.

A multi-target tracking algorithm for application to adaptive cruise control

This paper presents a Multiple Target Tracking (MTT) Adaptive Cruise Control (ACC) system which consists of three parts; a multi-model-based multi-target state estimator, a primary vehicular target determination algorithm, and a single-target adaptive cruise control algorithm. Three motion models, which are validated using simulated and experimental data, are adopted to distinguish large lateral motions from longitudinally excited motions. The improvement in the state estimation performance when using three models is verified in target tracking simulations. However, the performance and safety benefits of a multi-model-based MTT-ACC system is investigated via simulations using real driving radar sensor data. The MTT-ACC system is tested under lane changing situations to examine how much the system performance is improved when multiple models are incorporated. Simulation results show system response that is more realistic and reflective of actual human driving behavior.

A vehicle-to-vehicle distance control algorithm for stop-and-go cruise control

A vehicle-to-vehicle distance control algorithm for stop-and-go cruise control has been proposed. The control algorithm consists of a distance control algorithm and throttle/brake control algorithm for acceleration tracking. A vehicle desired acceleration for vehicle-to-vehicle distance control has been designed using linear quadratic optimal control theory. Performance of the control algorithm has been investigated via computer simulations. It has been shown that the proposed control algorithm can provide satisfactory performance.

A driver-adaptive range policy for adaptive cruise control

Abstract A driver-adaptive range policy for adaptive cruise control is presented. Driver range policies have been analysed using real-world driving data on normal road conditions obtained from 125 participants. A vehicle longitudinal control algorithm has been developed on the basis of the analysis to incorporate the range policy of human drivers into the control strategy. An estimation and adaptation method for characteristic parameters of driver range policy has been investigated. Driver tendency parameters have been estimated during manual driving by means of the recursive least-squares algorithm and then these estimated parameters have been used in the controller adaptation. The vehicle-following characteristics of the cruise-controlled vehicle have been investigated via simulations using real driving radar sensor data and a validated vehicle simulator. The vehicle-following characteristics of cruise-controlled vehicles have been compared with those of manually driven vehicles. The vehicle-following behaviour of cruise-controlled vehicles with the proposed adaptive control strategy is quite close to that of manually driven vehicles. Vehicle-following characteristics that are acceptable to drivers may be achieved by using the driver-adaptive range policy.

Side Slip Angle Based Control Threshold of Vehicle Stability Control System

Vehicle Stability Control (VSC) system prevents vehicle from spinning or drifting out mainly by braking intervention. Although a control threshold of conventional VSC is designed by vehicle characteristics and centered on average drivers, it can be a redundancy to expert drivers in critical driving conditions. In this study, a manual adaptation of VSC is investigated by changing the control threshold. A control threshold can be determined by phase plane analysis of side slip angle and angular velocity which is established with various vehicle speeds and steering angles. Since vehicle side slip angle is impossible to be obtained by commercially available sensors, a side slip angle is designed and evaluated with test results. By using the estimated value, phase plane analysis is applied to determine control threshold. To evaluate an effect of control threshold, we applied a 23-DOF vehicle nonlinear model with a vehicle planar motion model based sliding controller. Controller gains are tuned as the control threshold changed. A VSC with various control thresholds makes VSC more flexible with respect to individual driver characteristics.

A Supervisor-Based Neural-Adaptive Shift Controller for Automatic Transmissions Considering Throttle Opening and Driving Load

Recently, many passenger cars have adopted automatic transmissions for shifting gears, and thus the smooth and precise control of gear shifts of passenger car automatic transmissions has become more and more essential for the riding comfort of vehicles equipped with automatic transmissions. In this article, a neural network-based supervisor for an automotive shift controller considering the throttle opening, variations in throttle opening, and the driving load is presented. For using the driving load information, an, observer-based driving load estimation algorithm is proposed. A proportional-integral-derivative controller along with an open loop controller is used as a low level controller for controlling the gear shifts, and a supervisory controller for properly adapting the shift control parameters of the low level shift controller is designed using ANFIS. To evaluate the control performance of the proposed supervisor-based shift controller, both simulation studies and experimental studies are performed for various shifting situations.