【作者】 赵晓红；

【导师】 宫文斌；

【作者基本信息】 吉林大学 ， 机械电子工程， 2004， 硕士

【摘要】 推土机是以土方为作业对象的循环作业机械，其作业工况比较恶劣，在工作过程中驾驶员需要不断调整工作装置的位置，经常变换推土机的速度和改变行进方向。目前国内外生产的推土机转向和制动系统主要采用集中连杆杆件和软轴操纵机构，将推土机的变速、转向和制动操纵集中在操纵杆上进行。这种结构需要的操纵杆件较多，而且操纵力较大，这在频繁转向、制动的场合下，分散了驾驶员的注意力，影响了作业质量，同时劳动强度较大，系统可靠性较低。推土机驾驶室内空间狭小，在简化结构和各操纵杆合理布置方面存在突出矛盾。此外，现有推土机的转向、制动系统主要采用机械联动和液压联动两种方式，无论是哪种方式，都必须调整与转向制动有关的各连杆、调整螺栓等，如果有尺寸不符合要求或者调整不当的情况，就会出现转向、制动失灵。 由于长时间的相对运动，各拉杆也会出现磨损，造成尺寸异常，也会导致转向、制动失灵。由于上述因素的影响，推土机的作业性能、可靠性、操作性能和维修方便性大大降低。因此，有必要对原有推土机的转向、制动控制系统进行改进，使其成为便于安装、操纵的电控单手柄集中控制柔性系统。开发研制推土机单手柄转向、制动控制系统，可以大大地提高产品的控制性能、可靠性及自动化水平，也对将来特殊现场的遥控操作奠定基础。在不改变推土机原有传动结构的基础上，本系统采用电液比例控制方案，即通过控制电液比例阀来控制推土机的转向和制动，将电控的灵活性与液控的简单、方便性结合起来。控制原理如图1所示。图1 控制系统原理框图依据图中所示的控制原理，本文设计了系统液压控制回路。利用两个油缸来控制推土机左右两侧的转向制动阀，用电磁换向阀来选择控制侧，并用比例<WP=72>减压阀控制油缸内油液的压力。同时，本文以PIC16C73B型单片机为核心，设计开发了系统控制器。系统通过控制器输出不同占空比的PWM信号，来控制比例阀上比例电磁铁上的电流，进而控制比例减压阀输出的压力。设计硬件电路时，本文尽可能多地采用可靠的成熟电路，并进行了必要的抗干扰处理。 为了使系统有良好的控制效果，文中建立了系统的数学模型，然后对系统进行仿真，根据仿真结果，研究了系统的控制算法。本文首先推导了积分分离PID控制算法，在参数整定方面，根据系统的特点，选用了基于ITAE原则的自整定策略，这样可以保证系统在时变的情况下仍然有良好的控制效果。此外文中还设计了对系统数学模型不敏感的模糊控制算法，建立了隶属度函数，制定了模糊控制规则，并求取了模糊控制表。依据控制要求，及采用的控制算法，本文设计了系统的控制软件，编制了单片机控制程序。为验证系统的控制效果，本文对积分分离PID参数自整定算法和模糊控制算法进行了仿真和试验。结果表明，自整定积分分离PID具有比普通PID调节时间短、超调量小等优点，且该算法结构简单、易于实现；模糊控制对系统也能起很好的控制作用，增强了控制系统的柔性、鲁棒性；两种算法的控制效果都可以改善系统的静、动态特性，均达到设计要求，能够保证油缸的位移与手柄给定信号之间有良好的跟随特性。在进行系统整体设计和软、硬件设计时，本文充分考虑了系统的实际工况，设置了手柄信号中位死区，以消除系统的误动作；同时，为适应比例阀的工作频率，利用单片机对PWM输出信号进行了分频处理，保证了通过比例阀的平均电流值不变。本控制系统，已在TY230型推土机上进行了装机试验，试验效果良好，实现了推土机转向制动的单手柄控制，大大地提高了推土机的操纵性能，改善了驾驶员的工作条件。本文的研究成果可以直接应用于实际，具有较高的实用价值，在实现单手柄集中控制方面，可供其它机型借鉴。更多还原

【Abstract】 Bulldozer is one of earthwork engineering machine, and its working environment is atrocious. During working period, the driver needs to adjust the position of working device, and change the speed and the direction of bulldozer continually. At present, centralized connecting lever and flexible shaft manipulating mechanism is used in most steering and barking system of bulldozers which are produced at home and abroad. This kind of structure needs more joy sticks, each of which need biggish force to move. In the case of frequently steering and barking, the driver has to pay more attention to change the joy sticks, which will affect the working quality, and make the driver more tired. For the narrow space of cab, simplifying structure is against to setting all joy sticks reasonable. Furthermore, connecting levers and adjusting bolts related to the steering and braking system must be adjusted. If there is any nonconformance in dimension and adjustment, steering or braking failure may be caused. Also the failure may be caused by the abnormal dimension of pull lever for long time relative movement. So it is necessary to improve the steering and barking system of bulldozers and make it be electric control single stick system which is easier to be installed and manipulated. Developing new type steering and barking system will improve the control performance, reliability and automation of bulldozers, and make basis for future distance control of special occasion.In this system, electro-hydraulic proportional control technology is adopted without change the transmission system of bulldozer, and steering or braking can Fig. 1 Control principles block diagrambe realized by controlling the current through the proportional valve. The control principles refer to Fig.1. <WP=74>Based on the above control principles, system hydraulic loop is designed in this article. In the system, two hydraulic rams are used to control the steering and braking valves in both sides of bulldozer, one electromagnetic direction valve to select controlling side, and proportional reduced valve to control the pressure of hydraulic ram. At the same time, PIC16C73B single chip processor is used in the controller which can produce PWM signals. By adjusting the duty factor of PWM signals, the pressure output by the proportional reduced valve is controlled. For hardware design, reliable and well-rounded circuit is adopted as much as possible, to make the electric unit have high reliability.In order to have good control performance, mathematical model is established, and the system is simulated in the article. According to the result, we analyze and research the algorithm of the control system. According to feature of the system, the integral separation PID control algorithm is deduced, and self-adjusting method based on ITAE principle is adopted. So in the case of time variation, good control performance can be obtained. Furthermore, we design fuzzy control algorithm, build up the membership functions, establish fuzzy control regulation, and get the fuzzy control table in chapter 5. Based on the control requirements and algorithm, system software is designed and control program is worked out.Integral separation PID control algorithm with self-adjusting parameter and fuzzy control algorithm have been simulated and experimented in the article to test their control effect. And the results show that Integral separation PID control algorithm with self-adjusting parameter has shorter adjusting time and lower overshoot than conventional PID control algorithm and it has simple structures which make it realized, and the fuzzy control algorithm enhances the flexibility and robustness of the system and has good control effect too. Both kinds of algorithms can improve the static and dynamitic characteristics of the system, and meet the design requirements.Considering the actual operating condition, mid position dead zone of the stick angle is set in the software and hardware to avoid false operation. In order to meet the frequency requirement of valve, the freq更多还原