【作者】 胡静波；

【导师】 张子达；

【作者基本信息】 吉林大学 ， 机械设计及理论， 2008， 博士

【摘要】 线控转向是指通过微电子技术连接并控制转向系统的元件来代替传统的机械或液压连接,用传感器记录驾驶者的转向数据和车辆转角、车速、转向阻力等数据并传送给车载控制器,车载控制器按照给定的控制算法计算输出控制信号,控制车辆的转向角度实现转向控制。装载机线控转向系统具有转向传动比可调、路感清晰、便于整机布置等优点,而且还可以自由设计车辆转向的力传递特性和角传递特性,是车辆转向系统的重大革新。但线控转向系统能否替代现有的装载机流量放大转向系统,取决于线控转向系统的可靠性、安全性和系统成本等方面。其中,最为重要的是系统的可靠性,这决定于系统容错能力的高低。容错是指所研究的对象能容许系统发生故障,不会因故障而发生失控或者崩溃;容错控制是指在传感器、控制器、执行器或系统其他元部件发生故障时,控制系统仍然是稳定的,并具有较理想的特性。本文立足于国内技术水平,追踪国外的先进技术,开发了装载机容错线控转向系统,并围绕该系统进行了较为深入的理论与实验研究。首先,应用有限状态机(FSM)系统动态行为建模工具,建立装载机容错线控转向系统的故障诊断模型,并根据该模型提出元件与系统的故障诊断算法。其次,应用马尔柯夫(Markov)过程理论建立系统的可靠性分析模型,并计算得出系统的可靠性。再次,对线控转向系统转向控制算法进行了研究,通过MATLAB仿真,对比分析数字PID控制算法、混合模糊控制算法,仿真及实验结果显示混合模糊控制算法响应时间较快、抗干扰能力强,可以较好地满足实际转向系统的需要。最后,对装载机容错线控转向系统进行了部分台架实验,包括转向液压系统性能实验、故障诊断算法及容错性能验证实验、转向控制算法及转向性能验证实验。实验及仿真结果表明本文开发的的装载机容错线控转向系统具有较高可靠性,能够满足转向系统的实时性、稳定性和准确性要求。更多还原

【Abstract】 The continuous development of modern science and technology pushed the overlapping and penetrating between different subjects greatly. And due to the application of the microelectronic technique, computer technology and the electromechanical integration to wheel loader, the comprehensive technique of wheel loader leap onto a new step. The integration of electronic technique, micro-computer, sensor, electro-hydraulic servo and control system remakes the traditional wheel loader. The modern wheel loader is more preponderant in work efficiency, task quality, environmental protection, serviceability and automation. And it is moving forward to further intellectualized direction. The steer-by-wire technology replaces the traditional mechanical or hydraulic juncture by connecting and controlling all the component of steering system through micro-electronics technology, using sensors to collect the data of steering , vehicle corner, vehicle speed, turning resistance and transfers them to the controller on the vehicle. Then the controller processes these signals according to the given control algorithm and outputs actuating signals to control the steering degrees of vehicle so as to realize the steering. The steer-by-wire system on wheel loader has advantages in transmission ratio tunable, road sense clever and vehicles assembly simply. Besides, the design of force and angle transfer characteristics becomes freely. It is a significant innovation in the vehicles steering system. But the steer-by-wire system can replace the existing whole hydraulic pressure steering system or not lies on the reliability, stability and system cost of the steer-by-wire system. And the most important is the reliability and stability of the system that lies on the fault-tolerance capability. Fault-tolerance means that the researched object allow system failure and won’t be out of control or breakdown for fault, fault-tolerance control is that the closed-loop control system can remain stable and has perfect characteristic when sensors, controllers, actuators or other parts of the system is wrong. The design of fault-tolerance control system mainly includes two parts: fault diagnosis and fault-tolerance controller design. The former checks the kinds and position of fault (failure separation), degrees and occurrence time(failure recognize). Generally speaking, fault diagnosis methods involve: based on mathematical model, based on signal processing and knowledge. The latter includes hardware fault-tolerance design, software fault-tolerance design, and other fault-tolerance design. Among them, the most important and effective method is the hardware fault-tolerance design that rely on adopting multiple hardware. In this paper, the fault-tolerance steer-by-wire system on wheel loader uses hardware redundancy fault-tolerance technology. Steering wheel corner sensors and vehicle corner sensors have triple modular redundancy, controller and its communication adopts duplication redundancy. At the same time, the system takes software fault-tolerance technology and resolution redundancy technology to ensure the fault-tolerance capability and reliability of the system.This Ph.D. dissertation is funded by the project (No.2005083) named "Application of Steer-By-Wire technology in wheel loader" from JILIN Education Department and the project named "Research of Steer-By-Wire technology and Application on Wheel Loader" funded by corporation. Based on domestic technology level and tracking foreign advanced technology, the fault-tolerance steer-by-wire system on wheel loader is researched and designed. The system integrates electro-hydraulic proportion control technology, computer technology and fault-tolerance control technology etc., realized the transform between two steering sensitivity modes in the light of the wheel loader actual operating modes. At the same time the system has a high reliability and safety.This dissertation fulfilled research objective as following: 1、The research achievements of turning technology of wheel loader and steer-by-wire technology domestic and abroad were surveyed and worked up, and the characteristics, operating principle, the feasibility and progress of the technology applied to the articulated wheel loader steering system is analyzed.2、The design proposal of“fault-tolerance steer-by-wire system on wheel loader "was put forward. This system adopted fault-tolerance control technology with high reliability, adjustable steering ratio and steering sensitive.3、Finite state machine (FSM)was used to establish the system dynamic behavior model, and it was applied to fault diagnosis of the system.4、The control algorithms for steer-by-wire system were researched.MATLAB simulation results showed that Fuzzy control algorithm has quick response time, high stability and control precision.5、. Markov state transition diagram was applied to establish the steer-by-wiresystem reliability analysis model which was used to analysis the system reliability and calculated the reliability of the system.6、Embedded controller of the fault-tolerance steer-by-wire on wheel loader was developed, contains hardware design and software design. Because of the complicated operating modes and the bad working conditions, the wheel loader will be influenced by all sorts of disturbances and the system failure will occur, therefore the system anti-jamming design was done to guarantee the system stabability and reliability under the complex working conditions.7、Some experiments were done for the fault-tolerance steer-by-wire system, including fault diagnosis algorithm and fault-tolerant performance verification test ,the control algorithms verification test. Test and simulation results showed that the fault-tolerance steer-by-wire system on wheel loader has high reliability, and it can satisfy the requirements of real-time, stability and accuracy requirements.8、summarized the steer-by-wire technology on wheel loader , and put forward the research expectation in the future.The main innovations of this dissertation are as follows:1、The fault-tolerance control technology was applied to the steer-by-wire system on wheel loader for the first time domestically.Researches on the steer-by-wire technology on vehicles are fewer in our country than others. Especially, the reliability study is almost blank. The fault-tolerance control technology and the steer-by-wire technology were integrated for the first time domestically. The design scheme of the fault-tolerance steer-by-wire system on wheel loader was put forward in this dissertation, and the theory and experiment researches were taken about it. The results showed that the system has high reliability, and can satisfy the requirements of real-time, stability and accuracy requirements.2、The fault-tolerance steer-by-wire system fault diagnosis algorithm was put forward.In this article, the fault state of the fault-tolerant steer-by-wire system were researched and classified in detail. Finite state machine was used to establish the system dynamic behavior model, and according to the model, fault diagnosis algorithm was proposed. Test results verified the correctness of the algorithm.3、Researches on the steering control algorithm of the steer-by-wire system.Fuzzy control algorithm was chosen through MATLAB simulation results compare. Simulation and test results showed that Fuzzy control with faster response time and the strong anti-interference capability can satisfy the requirement of actual steering system. Research expectation of the future is proposed in this dissertation:1、Take more experimental study to verify the performance including real-time, accuracy and stability of the steer-by-wire system in different operating conditions. Set various fault conditions comprehensively by the fault injection method to certify the fault tolerance and reliability of the system.2、Analysis the infection of the speed, tire pressure and bucket height .Make the system control model and the actual operating mode more closer, and improve the system performance further.3、Research the road sense feedback control to enhance the controllability of the vehicle.4、Carry out the integration control study, and take the steer-by-wire as a part of the entire vehicle control system. Prepare for the integration of the engine control, speed changing, steering, braking, remote fault diagnosis, remote machine cluster operating and so on.5、Strengthen the applied research, optimize the system and reduce the cost in order to prepare full for the production.更多还原