Search Results

In this paper, a method for directional control of articulated heavy vehicles is proposed. The tractor yaw rate, the tractor lateral velocity and the articulation angle are selected as the control variables. The desired values of these states are defined in such way to improve the maneuverability and the stability of the articulated vehicle. A linear quadratic regulator controller is designed based on the linear model of the articulated vehicle to make the control variables follow the desired responses. Furthermore, a nonlinear 14 Degrees of freedom (DoF) model is developed to evaluate the proposed control method. The significant effect of the proposed method on improving the directional behavior of the articulated vehicle is proved through the simulations of the high speed lane change maneuver on a slippery road.

The aim of this research is to develop a new electronic braking system based on an electric powered controlled friction brake with high self-reinforcement capability which has performance advantages over the conventional electromechanical brake systems. To avoid jamming, a special control technology was developed. Thus, by intelligently controlling a brake wedge, the kinetic energy of a vehicle is transformed into braking power. The physical effects involved, lead to a significant reduction of energy consumption of the brake actuator compared to “conventional” brake-by-wire systems. The performance of the “Electronic Wedge Brake” (EWB) in a vehicle was studied using a quarter vehicle model. A sliding mode controller was designed for an optimum wheel slip control, and the control simulation results show significant shorter braking distance in comparison to other conventional braking systems.

In this paper, an integrated vehicle dynamics control system is designed to improve vehicle yaw stability by coordinating control of Active Front Steering (AFS) and Direct Yaw-moment Control (DYC) based on a new concept. The control system has a hierarchical structure and consists of two controlling layers. A fuzzy logic controller is used in the upper layer (Yaw Rate Controller) to keep the yaw rate in its desired value. The yaw rate error and its rate of change are applied to upper controlling layer as inputs, where the direct yaw moment control signal and the steering angle correction of the front wheels are built as the outputs. In the lower layer (Fuzzy Integrator), a fuzzy logic controller is designed based on the working region of the lateral tire forces to determine percentage of usage of upper layer controlling inputs.

A novel driver-assist stability system for all-wheel-drive Electric Vehicles is introduced. The system helps drivers maintain control in the event of a driving emergency, including heavy braking or obstacle avoidance. The system comprises a Fuzzy logic that independently controls wheel torques to prevent vehicle spin. A neural network is trained to generate the required yaw rate reference. Another Fuzzy system for each wheel controls the slip to ensure vehicle stability and safety. Furthermore a new vehicle speed estimator is employed for slip estimation. The intrinsic robustness of fuzzy controllers allows the system to operate in different road conditions successfully. Moreover, the ease to implement fuzzy controllers gives a potential for vehicle stability enhancement.

This paper presents a novel method for motion control and driver stability assist system of an electric vehicle with independently driven wheels. A combination of two controllers for yaw rate and wheel slip is used to improve yaw stability of a two-wheel-drive electric vehicle. Vehicle speed is estimated using a multi-sensor data fusion method. To overcome the uncertainties in tire-road friction, a Fuzzy logic approach is employed for both controllers. The effectiveness of the proposed control method is evaluated by simulation.

The goal of this research was to find the effects of the most important design parameters on passenger cars during “Untripped On-Road Rollover” maneuvers. This work involved studies of vehicle behavior under severe maneuvering conditions include rollover, which was done by using a computer simulation. In order to get a good insight into the effects of design parameters and sensitivity of vehicle rollover to each parameter, a 16 degree of freedom vehicle dynamic model with Pacejka tire model and necessary submodels were developed. Validation was done using standard test results for a passenger car. In order to simulate severe maneuvers, some of suggested test procedures of related organizations were studied. Finally, the J-Turn and Obstacle Avoidance tests were selected. According to the results of this study, some design comments for better vehicle on-road rollover stability were specified.

Nowadays a lot of car manufactures are switching to electric power steering. Regarding to packaging, cooling, performance and cost, they use different types of electric power steering such as column assisted, pinion assisted and rack assisted steering. This paper investigates to find out the effects of these differences in position of applied assisting torque on performance of electric power assisted steering. For this purpose three different EPS system models with PID controller are constructed. Seven and eight degrees of freedom models of EPS system are used to obtain system state equations. MATLAB/Simulink software is used to simulate steering models to investigate the effect of the position of applied assisting torque on steering efficiency and sensitivity in parking maneuvers, and obtain both open and closed loop system responses.

The stability of a four motor-wheel drive electric vehicle is improved by independent control of wheel torques. An innovative Fuzzy Direct Yaw Control method together with a novel wheel slip controller is used to enhance the vehicle stability and safety. Also a new speed estimator is presented in this paper, which is used for slip estimation. The intrinsic robustness of fuzzy controllers allows the system to operate in different road conditions successfully. Moreover, the ease to implement fuzzy controllers gives a practical solution for vehicle stability enhancement.

In this paper, a control law is developed based on the sliding mode control for electrohydraulic active suspension. The law is derived from simulation of hydraulic system, which contains valve and actuator dynamics. Controller is designed in such a way that the displacement and acceleration (as two independent set points) to approach to zero. When the acceleration is controlled, the displacement deviates from set point, therefore new control approach has been developed. The input servovalve voltage is determined in such a way that, actuators apply required force to sprung mass in order to increase ride comfort. At first the dynamic equations for vehicle are derived. Sliding mode control is applied for derivation of control equations. Then the equations have been solved by simulink and finally the results have been presented.

In this paper a vehicle model including the steering, the tire and the suspension systems is presented. Assuming one out-of-balance wheel, the response of the system is obtained and the vibration characteristics of the steering system are analyzed. Based on the analysis conducted, two of the steering system parameters are selected and optimized. This is achieved by performing a sensitivity analysis with respect to various system parameters.