推土机工作装置数字电液比例控制
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摘要
随着科学技术和微电子技术的发展，全世界进入以机电一体化为核心的设备革命阶段，未来的发展趋势是使微机超大规模集成电路和传感器技术有突破性进展，这将使推土机得到迅速的发展，使其作业性能、可靠性、维修性、安全性及燃料经济性有明显的提高。为了改造推土机工作装置的操纵性，使外国产品国产化，本文提出了用数字比例减压阀为先导阀代替原有的PPC阀，与多路阀构成数字电液比例换向阀，实现对推土机工作装置的数字化控制。
推土机的工作装置利用液压系统驱动，控制铲刀油缸来完成推土等作业。本文设计的数字电液比例控制系统由控制手柄（电位器）、电控模块（ECU）、先导阀（比例减压阀）、多路换向阀和油缸组成。
操作者作业时操纵控制手柄，发出指令信号，经电控制系统处理形成PWM（脉宽调制）信号，然后经开关式功放电路——电流放大电路放大，驱动比例减压先导阀，对主控制阀进行各工作位置的控制，以实现铲刀的升降和倾斜等动作。操作者通过控制先导阀，线性比例地向主阀两端输入压力，推动主阀左右移动实现主阀换向，由于先导阀为小流量元件，滑阀的行程和弹簧回复力都可以设计得很小，以减小操纵力矩，从而满足了PPC阀的特点（操纵手柄短）。此外，主阀与先导阀之间无刚性连接，其在主机上的布置亦同原系统的布局。
此设计系统的优点是阀芯的运动响应PWM信号的平均值，使阀芯工作时处于微振动状态，大大减小了比例阀的滞环；另外，由于PWM信号的电流放大电路为开关式放大电路，放大器只工作在导通和截止状态节能效果好。
本液压系统的主要元件是比例减压阀和多路阀，先分别进行建模和仿真，再对整个系统进行建模和特性分析。
比例减压阀的特性分析及建模
电液比例减压阀是由脉宽调制信号来进行控制的。对一理想的减压阀在一个调制周期T内，电压波形与阀芯位移波形完全相同。但由于电
液比例减压阀受电磁线圈的响应能力及阀芯运动时间的影响，实际的阀芯响应不可能实时地跟随脉宽信号的变化，并且其响应特性随脉冲调制周期（或频率）和占空比变化很大。
应用现代控制理论，获得描述比例减压阀数学模型的状态方程组：
根据以上状态方程应用MATLAB做出减压阀子系统仿真框图，可获得相应的流量与时间仿真曲线。通过对比例减压阀的特性分析可知，比例减压阀通过改变占空比可以调节多路阀控制腔的流量，从而控制其压力，因此可以用其作为多路阀的先导阀。
多路阀的特性分析及建模
在数字电液比例先导减压阀控制换向阀的结构简图中,多路换向阀是其中最重要部件之一，所以对该阀的特性进行分析具有重要意义。
据图3-9，可得描述多路阀动态特性的数学模型的状态方程组（3.19），通过仿真可得图3-11多路阀主阀口的流量与其控制腔的压力仿真曲线。在单位阶跃作用下，与呈线性关系，符合系统要求。又因为占空比与压力的变化率成一定的关系，所以流量与占空比有一空的对应关系。
（3）系统的建模
通过以上对该系统各组成部分的建模与特性分析，根据图3-2液压系统仿真框图对整个系统进行仿真，系统的输入信号为某一占空比的单位脉冲信号，在此信号的作用下可得系统终端（液压缸）的流量随时间的变化曲线，即系统的动态特性关系曲线，如图3-13所示。
通过试验检验以上三个模型，对采样所得数据进行处理后分别得到模型的试验曲线，验证了各个元件和系统的数学模型和仿真的正确性，从理论和实践上证明数字电液比例控制系统是可以实现的。
With the development of science and microelectronics technique, the trend of the future is that there are breakthroughs improvement in Grand Scale Integration of microcomputer and technology of transducer. All the world will enter the stage of equipments revolution taking the integrity of machine and electron as the core, which will make the bulldozer get quick development, such as apparent improvement in working function, dependability, maintainability, safety and fuel economy. In order to reform the maneuverability of the working device of bulldozer and make production abroad be homemade, digital proportional decompression valve which substitutes for the original PPC valve is used as pilot valve to make up of digital electro-hydraulic proportional directional valve with multiple-unit valve in this article, which fulfills digitized control of working device for bulldozer.
The working device of bulldozer takes advantage of the hydraulic system to drive and control cylinder of shovel to complete the homework, such as pushing soil, loading soil etc.
The digital electro-hydraulic proportional control system, in the article, comprises of control handlebar (electric potential device), electronic control unit (ECU), pilot valve (proportional decompression valve), multiple-unit valve and oil cylinder.
When manipulator manipulates control handlebar, it sends instruction signal that is converted into PWM signal (Pulse-Width Modulation) dealt with by electricity control system. Then this signal is amplified by the switch type of power-amplifying circuit, current-amplifying circuit, to drive pilot proportional decompression valve and control each working position of main control valve, in order to fulfill kinds of actions of shovel, such as rising and falling, pitching etc. After manipulator manipulates pilot valve, pressure outputs to the both ends of main valve according to linear proportion, which makes main valve move between two directions to realize
change of its direction. Because pilot valve is a small flux piece, the journey of slide valve and force of restitution of spring can be designed much smaller, which cuts down the manipulating moment greatly, so as to meet the character of PPC-short of manipulating handlebar. In addition, layouts of main valve and pilot one are the same as original layouts of system, for there is no rigid conjunction between them.
This designed system has two advantages: first, the movement of valve core responds the average value of PWM signal, which makes valve core work in tiny vibration situation and decreases stagnant wreath of proportional valve greatly; second, amplifier is in good economical function only working in switch (on or off) situation, for current amplifying circuit of PWM signal is a switch type of enlarging circuit.
The main parts of this hydraulic system are proportional valve and multiple units one. First, model and simulate them individually, then analyze the whole system.
The characteristic analyzing and modeling of proportional decompression valve
Electro-hydraulic proportional decompression valve is controlled by PWM signal. In a modulating period T as to an ideal decompression valve voltage wave is complete the same as the displacement wave of valve core. But, because electro-hydraulic proportional decompression valve is affected by the responding ability of electromagnetic coil and the time of valve moving, in fact it is impossible for valve core responding to follow variety of Pulse-Width signal always in time. And its respond character varies much with the period of PWM (or frequency) and the variety of occupy.
Make use of the modern control theories and conclude the following state equations about proportional compression valve:
Based above state equations, work out simulated diagram of compression valve subsystem with MATLAB and acquire simulated curve of relation between fluxes and time accordingly. Through studying characteristic analysis of proportional compression valve, we can conclude that proportion
推土机的工作装置利用液压系统驱动，控制铲刀油缸来完成推土等作业。本文设计的数字电液比例控制系统由控制手柄（电位器）、电控模块（ECU）、先导阀（比例减压阀）、多路换向阀和油缸组成。
操作者作业时操纵控制手柄，发出指令信号，经电控制系统处理形成PWM（脉宽调制）信号，然后经开关式功放电路——电流放大电路放大，驱动比例减压先导阀，对主控制阀进行各工作位置的控制，以实现铲刀的升降和倾斜等动作。操作者通过控制先导阀，线性比例地向主阀两端输入压力，推动主阀左右移动实现主阀换向，由于先导阀为小流量元件，滑阀的行程和弹簧回复力都可以设计得很小，以减小操纵力矩，从而满足了PPC阀的特点（操纵手柄短）。此外，主阀与先导阀之间无刚性连接，其在主机上的布置亦同原系统的布局。
此设计系统的优点是阀芯的运动响应PWM信号的平均值，使阀芯工作时处于微振动状态，大大减小了比例阀的滞环；另外，由于PWM信号的电流放大电路为开关式放大电路，放大器只工作在导通和截止状态节能效果好。
本液压系统的主要元件是比例减压阀和多路阀，先分别进行建模和仿真，再对整个系统进行建模和特性分析。
比例减压阀的特性分析及建模
电液比例减压阀是由脉宽调制信号来进行控制的。对一理想的减压阀在一个调制周期T内，电压波形与阀芯位移波形完全相同。但由于电
液比例减压阀受电磁线圈的响应能力及阀芯运动时间的影响，实际的阀芯响应不可能实时地跟随脉宽信号的变化，并且其响应特性随脉冲调制周期（或频率）和占空比变化很大。
应用现代控制理论，获得描述比例减压阀数学模型的状态方程组：
根据以上状态方程应用MATLAB做出减压阀子系统仿真框图，可获得相应的流量与时间仿真曲线。通过对比例减压阀的特性分析可知，比例减压阀通过改变占空比可以调节多路阀控制腔的流量，从而控制其压力，因此可以用其作为多路阀的先导阀。
多路阀的特性分析及建模
在数字电液比例先导减压阀控制换向阀的结构简图中,多路换向阀是其中最重要部件之一，所以对该阀的特性进行分析具有重要意义。
据图3-9，可得描述多路阀动态特性的数学模型的状态方程组（3.19），通过仿真可得图3-11多路阀主阀口的流量与其控制腔的压力仿真曲线。在单位阶跃作用下，与呈线性关系，符合系统要求。又因为占空比与压力的变化率成一定的关系，所以流量与占空比有一空的对应关系。
（3）系统的建模
通过以上对该系统各组成部分的建模与特性分析，根据图3-2液压系统仿真框图对整个系统进行仿真，系统的输入信号为某一占空比的单位脉冲信号，在此信号的作用下可得系统终端（液压缸）的流量随时间的变化曲线，即系统的动态特性关系曲线，如图3-13所示。
通过试验检验以上三个模型，对采样所得数据进行处理后分别得到模型的试验曲线，验证了各个元件和系统的数学模型和仿真的正确性，从理论和实践上证明数字电液比例控制系统是可以实现的。
With the development of science and microelectronics technique, the trend of the future is that there are breakthroughs improvement in Grand Scale Integration of microcomputer and technology of transducer. All the world will enter the stage of equipments revolution taking the integrity of machine and electron as the core, which will make the bulldozer get quick development, such as apparent improvement in working function, dependability, maintainability, safety and fuel economy. In order to reform the maneuverability of the working device of bulldozer and make production abroad be homemade, digital proportional decompression valve which substitutes for the original PPC valve is used as pilot valve to make up of digital electro-hydraulic proportional directional valve with multiple-unit valve in this article, which fulfills digitized control of working device for bulldozer.
The working device of bulldozer takes advantage of the hydraulic system to drive and control cylinder of shovel to complete the homework, such as pushing soil, loading soil etc.
The digital electro-hydraulic proportional control system, in the article, comprises of control handlebar (electric potential device), electronic control unit (ECU), pilot valve (proportional decompression valve), multiple-unit valve and oil cylinder.
When manipulator manipulates control handlebar, it sends instruction signal that is converted into PWM signal (Pulse-Width Modulation) dealt with by electricity control system. Then this signal is amplified by the switch type of power-amplifying circuit, current-amplifying circuit, to drive pilot proportional decompression valve and control each working position of main control valve, in order to fulfill kinds of actions of shovel, such as rising and falling, pitching etc. After manipulator manipulates pilot valve, pressure outputs to the both ends of main valve according to linear proportion, which makes main valve move between two directions to realize
change of its direction. Because pilot valve is a small flux piece, the journey of slide valve and force of restitution of spring can be designed much smaller, which cuts down the manipulating moment greatly, so as to meet the character of PPC-short of manipulating handlebar. In addition, layouts of main valve and pilot one are the same as original layouts of system, for there is no rigid conjunction between them.
This designed system has two advantages: first, the movement of valve core responds the average value of PWM signal, which makes valve core work in tiny vibration situation and decreases stagnant wreath of proportional valve greatly; second, amplifier is in good economical function only working in switch (on or off) situation, for current amplifying circuit of PWM signal is a switch type of enlarging circuit.
The main parts of this hydraulic system are proportional valve and multiple units one. First, model and simulate them individually, then analyze the whole system.
The characteristic analyzing and modeling of proportional decompression valve
Electro-hydraulic proportional decompression valve is controlled by PWM signal. In a modulating period T as to an ideal decompression valve voltage wave is complete the same as the displacement wave of valve core. But, because electro-hydraulic proportional decompression valve is affected by the responding ability of electromagnetic coil and the time of valve moving, in fact it is impossible for valve core responding to follow variety of Pulse-Width signal always in time. And its respond character varies much with the period of PWM (or frequency) and the variety of occupy.
Make use of the modern control theories and conclude the following state equations about proportional compression valve:
Based above state equations, work out simulated diagram of compression valve subsystem with MATLAB and acquire simulated curve of relation between fluxes and time accordingly. Through studying characteristic analysis of proportional compression valve, we can conclude that proportion
引文
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[2] 胡寿松：自动控制原理，国防工业出版社，1998.8
[3] 黎启柏：电液比例控制与数字控制系统，机械工业出版社，1997，55~76
[4] 李华等：MCS-51系列单片机实用接口技术，北京航空航天大学出版社，2001
[5] 路甬祥、胡大纮等：电液比例控制技术，机械工业出版社，1998.11
[6] 路甬祥等：液压气动技术手册，机械工业出版社,2002.1
[7] 张永呆：流体动力系统的计算机控制，机械工业出版社，1992
[8] 李友善：离散系统理论，国防工业邮购版社，1985
[9] 王占林：近代液压控制，机械工业出版社，1997.8
[10] 刘少军：基于高速开关阀的液压位置系统最优控制研究，机床与液压，2000（2）
[11] 宋俊、殷庆文：液压系统优化，机械工业出版社，1996.12
[12] 赵应樾：名优机械液压系统及其修理（Famous & Fine Mechanical Hydraulic System And It’s Adjustment），上海交通大学出版社，2002.3
[13] 德兰斯菲尔德：液压控制系统的设计与动态分析，科学出版社，大连工学院译，1987.3
[14] 刘能宏、田树军：液压系统动态特性数字仿真，大连理工大学出版社，1993.8
[15] 王正良：微机电液控制技术，大连理工大学出版社，1993.8，92~98
[16] 雷天觉：液压工程手册，机械工业出版社，1990
[17] 林国重、盛东初：液压传动与控制，北京工业学院出版社，1986.6
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