【作者】 罗石；

【导师】 苏清祖；

【作者基本信息】 江苏大学 ， 车辆工程， 2010， 博士

【摘要】 汽车主动安全是汽车安全设计的重要研究方向,其目的是为了消除事故隐患,在事故发生之前避免其发生。转向系统是驾驶员实现车辆操控的关键部件,它关系到车辆的操作稳定性和车辆的行驶安全。在正常的行驶工况下要求车辆有良好的操作稳定性,这就要求车辆在不同行驶工况下具备不同的灵敏度,在危险即将发生时,要求驾驶员能够及时通过转向系统、制动系统等调整车辆的姿态避免危险的发生。传统的转向系统由于方向盘和车轮之间的传动关系固定,因此很难做到通过转向系统自身的控制实现车辆的主动安全控制和操作稳定性控制,车辆操控性能和主动安全大都依靠驾驶员的经验和技巧,在遇到紧急情况时,驾驶员的本能反应往往会出现错误的操作使车辆的操纵失控,从而导致事故的发生。线控转向系统将驾驶员的操控和车辆的转向控制分为两个相对独立的系统,驾驶员不直接对车辆的转向实现操控,而是通过电控单元加以处理判断后控制车辆转向,转向盘和车轮之间的传动关系可以由控制系统根据实际情况和当前行驶姿态来改变,这样给转向特性的设计带来了很大的自由发展空间。本论文将线控转向的控制和车辆行驶姿态的测量、预测相结合,对车辆行驶安全与车辆行驶姿态的关系加以研究,提出了基于模糊决策的车辆行驶安全姿态的判别方法,利用AR预测理论对车辆的行驶安全加以预测,在此基础上研究了通过调节线控转向的传动比实现车辆操纵稳定性控制和车辆主动安全控制的理论和方法。本文研究的控制系统包含三个方面的内容：首先是转向盘系统的控制,其核心是路感和回正的控制,通过对转向盘力反馈模型的研究,以转向盘的转角和车速作为计算回正力矩的依据,通过建立转向盘控制系统数学模型,采用电流和电动机转速双反馈控制的方式,将专家模糊决策PID控制策略和最速最优控制(BANG-BANG控制)相结合,有效地实现了路感和回正控制的统一,获得较好的效果；其次是前轮转角控制系统的控制,其主要的目的是为了及时响应驾驶员对转向盘的操作,因此要求控制系统具备较快的响应,和转向盘控制系统不同,车辆在行驶过程中,路面的状态是不断变化的,在控制过程中控制对象的数学模型会不断地变化,所以应当采用鲁棒性较好的控制策略,滑模变结构控制器作为一种适应性强、性能优良的控制器,滑模变结构控制可通过控制器结构的不断调整和变化,有效地控制具有参数变化和外部扰动的被控制对象,很适合具有不确定性控制对象的前轮转角控制,本文采用基于趋近律的滑模变结构控制实现了前轮转角的快速跟踪；最后是转向盘和前轮转角之间的变传动比决策系统的设计,传动比可变作为线控转向系统区别于传统系统的最大特点,本论文通过对车身行驶姿态的测量和预测,采用模糊决策方法对车辆的安全状态加以预测,提出了采用车身侧倾角和侧倾角速度对车辆侧翻的危险评估的方法,提出了车辆质心侧偏角估计的简化模型,并通过对质心侧偏角预测估计车辆的侧滑情况,在以上对车辆的安全状态预测评估的基础上,本论文提出了通过调节传动比实现车辆操作稳定性控制以及在危险行驶姿态下主动安全控制。本论文主要研究了基于车辆行驶姿态预测的线控转向系统的控制策略,研究了线控转向路感与车辆姿态的关系,将专家模糊决策PID和最速最优控制结合,实现了线控转向系统路感和回正控制,创新性的将车辆行驶危险状态的预测和判断与线控转向系统的控制相结合,实现车辆主动安全控制,并采用基于趋近律的滑模变结构控制实现了前轮转角的快速随动控制。本文的研究为线控转向系统和车辆主动安全控制的研究提供了新的思路和方法。更多还原

【Abstract】 Automotive active safety is an important research direction of vehicle safety design, the designation is to eliminate the possibility of accident, and prevent its occurrence prior to the accident. Steering system is a key component of the vehicle control by driver, it is related to the operation of the vehicle stability and the safety of the vehicle. A good operational stability has been required under normal driving conditions, which require vehicles driving in different conditions with different sensitivity, when encountered emergency, we need the driver to adjust the posture of the vehicle to avoid the danger by steering systems, braking systems and etc.It is hard for the traditional steering wheel to realize the active safety control and wheel steering stability control of vehicle, because of the fixed Transmission between steering wheel and wheels. Vehicle handling and active safety mostly rely on the experience and skills of the driver, in an emergency situation, the driver’s instinctive react operation of the manipulation maybe error, which will make the vehicle lost control, and cause accidents.Steer-by-wire system divided the driver’s control and the vehicle steering control into two relatively independent systems. The driver’s controlling adds the judgment of the electronic control unit, instead of directly control the vehicle’s steering. The transmission relationship between steering wheel and wheels can be changed according to the actual situation and the current vehicle posture by control system, so that the design of steering characteristics but to be addressed through the electronic control unit to determine control of the vehicle after the turn, steering wheel and the relationship between the wheels by the transmission control system according to the actual situation and the current drive to change the attitude, so that it bring the design of steering characteristics lots of free space for development.This paper combining the control:of steer-by-wire with the measurement and prediction of the vehicle attitude, researching the relationship between the safety of vehicle and the vehicle attitude, proposing the judgment method based on the vehicle safety attitude by fuzzy decision. And using AR prediction theory to predicted the safety of the vehicle, on the basis of the predicated dates to research the theory and methods, which to achieve the vehicle stability control and vehicle active safety control by adjusting the steering gear ratio. In this paper, the control system consists of three aspects:The first is the steering wheel control system, the key is the road sense and the control of aligning. Research on the force feedback of steering wheel model, and take the steering wheel angle and vehicle speed as a basis for calculation of aligning torque, then to establish the mathematical model of the steering wheel control system, using two-way feedback control methods which by current and motor speed. We should combine the PID control of expert fuzzy decision control strategy with the speed optimum control(BANG-BANG control), to achieve the unity of road sense and the control of aligning effectively, and to obtain more good results;Followed by the control of the front steering angle control system, its main purpose is to timely response to the operation of the driver on the steering wheel, thus requiring the control system with fast response, and not the same with the steering wheel control systems, the state of road is changing with the processing of vehicle, the control object model will continue to change in the control process. So we should be adopted control strategy is robust, sliding mode adaptive controller has a good performance of control, sliding mode variable structure control can be continuously adjusted the controller structure, and effective prevent the parameter variations and external disturbances, it is suitable for the uncertain control of front wheel angle, this paper use sliding mode control based on reaching law to realize fast track of the front steering angle;Finally is the decision-making system design which refer to the variable transmission ratio between the steering wheel and front wheel angle, the most prominent feature of steering by wire system which to be different from traditional system is variable gear ratio. The paper take the measurement and prediction of vehicle’s body posture, predicted the vehicle’s security status by fuzzy decision method, and introduced the risk assessment by the parameter of the roll angle and the roll angular velocity of vehicle’s body. In the paper, proposed the simplified model of vehicle sideslip angle estimation, we estimated vehicle sideslip condition by the predicted of side slip angle. On the basis of the forecast evaluation of vehicle security status, we propose a method to achieve the stability steering control and active safety control in danger status by adjusting the transmission ratio.In this thesis, the research to the control strategy of wire steering system based on predicted of the parameters of vehicle attitude. We combine the expert fuzzy PID with the most rapidly decision-making optimal control to achieve the road sense and the aligning control, combined the predicament and the judgment of danger status with steering by wire control system innovatively, to achieve the active safety of vehicle control. And use sliding mode control based on the reaching law to achieve the fast follower control of front-wheel angle. This study search provides some new ideas and methods to the research of the by-wire steering system and vehicle active safety control.更多还原