| With the development of society and economy, vehicles have become an indispensable part of human life. Although vehicles make a significant contribution to the progress of human civilization and socio-economic, vehicle accidents are on the rise. Therefore, road traffic safety has become a global social problem. How to improve vehicle safety is currently a research hotspot. This paper focused on the lane departure assistance system(LDAS), and studied the key technologies of LDAS.A new strategy for the decision of lane departure avoidance was proposed. The performance of lane departure warning techniques was evaluated with the consideration of all kinds of objective and subjective factors. A novel approach for lane departure avoidance was presented, which applies additional yaw moment to the vehicle to correct lane departure of the vehicle by means of differential braking. A rapid prototyping test platform with the function of lane departure warning and assistance control was established. The proposed methods were validated on the platform and driver-in-loop test.The main contents of this paper are as follows:(1) A new strategy for the joint-decision of lane departure avoidance, which is based on the dynamic threshold of Time to Lane Crossing (TLC) was presented. Fixed threshold may lead to false alarm or missed alarm, even false intervention or missed intervention. A model of the dynamic threshold of TLC was proposed, which is calculated by vehicle-lane heading, vehicle speed, road adhesion and reaction time of the implementing agencies and driver in real-time. Too early intervention may produce unnecessary interference to the driver, while too late intervention may lead to lane departure. The proposed decision strategy can adjust the threshold for warning and control. A human-machine cooperation control architecture was proposed with the consideration of perception, decision-making and execution. The proposed strategy was validated in a Carsim/Simulink co-simulation platform.(2) Objective and subjective assessment criteria for lane departure warning were designed. A series of lane departure warning experiments were conducted based on a more realistic fixed-based driving simulator. In previous studies, researchers placed more emphases on the efficiency of warning system instead of driver’s subjective feeling. In this study, subjective and objective evaluation indexes were proposed. Effectiveness and drivers’ acceptance of seven types of warning techniques were further studied through a series of in-door experiments. Statistical methods were used to systematically analyze drivers’ sensitive to the auditory, visual and haptic warning technologies. A solution of warning technique to improve the effectiveness and acceptance was brought forward. The effects of pattern, amplitude and frequency of haptic warning on the effectiveness and drivers’ acceptance were studied through another series of in-door experiments. A method to improve the performance and drivers’ acceptance of haptic warning was put forward.(3) A novel approach for lane departure avoidance was proposed, which applies additional yaw moment to the vehicle to correct lane departure of the vehicle by means of differential braking. The desired yaw rate is determined by considering vehicle-lane deviation, vehicle dynamic and limitation of road adhesion. A sliding mode controller (SMC) was designed to control the additional yaw moment. The yaw moment is produced by the distribution of brake forces between the same side brakes, and lane departure avoidance is carried out by tracking the desired yaw response. In order to produce the additional yaw moment, a brake pressure close-loop control and a slip ratio balance servo control methods were presented. In terms of pressure close-loop control, fixed ratio and control allocation were used as the assignment methods for braking force distribution respectively. In terms of slip ratio balance control, a concept of equivalent slip ratio was put forward. The selection of the brake wheels is according to the additional yaw moment and yaw rate deviation. A new strategy for the balance of the equivalent slip ratio and rear wheel slip ratio was presented. The brake force is distributed in suboptimal. Two fuzzy controllers were designed to produce the additional yaw moment, and lane departure avoidance was carried out by tracking the desired yaw response. The proposed Lane departure avoidance method was evaluated in Carsim/simulink. Simulation results show that the proposed methods can restrict vehicle into the lane range and avoid lane departure accident.(4) A rapid prototyping test platform for lane departure driving assistance system was established, which is composed of CarsimRT/LabviewRT real-time platform, real steering and braking system. The methods, which were proposed in this study, are validated on the platform. The test results are conisistent with the simulation results. Several conclusions are obtained from various driving conditions. Dynamic TLC threshold can timely trigger warning and control. Brake force distribution method based on control allocation has better robustness. The slip ratio balance method has a good adaptability to the model parameters, although the control results are rougher than the braking pressure close-loop control method. The slip ratio balance method doesn’t need any additional cost, and is simple and reliable.The innovations of this paper are as follows:(1) A model of the dynamic threshold of TLC was presented, which is calculated by vehicle-lane heading, vehicle speed, road adhesion and reaction time of the implementing agencies and driver in real-time. The dynamic TLC threshold can trigger warning and control more timely.(2) Based on the in-door experiments, a solution of warning technique to improve the effectiveness and acceptance was brought forward.(3) A novel approach for lane departure avoidance was studied and designed, which applies additional yaw moment to the vehicle to correct lane departure of the vehicle by means of differential braking. The proposed control method has the following characteristics: less interference to driver, simple strategy of human-machine cooperate control, high reliability, practical and low cost. |
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