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用集中参数把子系统之间的作用关系抽象地表示为阻性元R、容性元C和感性元I的三种作用元。采用这种方法建模物理概念清晰，结合状态空间分析法可以较准确地描述和分析线性系统，该方法在时域中研究复杂非线性系统动态特性的一种有效的方法。

根据自调背压调速系统各元件的主要特性和建模规则[1]，得出了图3所示的系统的功率键合图。图中每根键上的半箭头表示功率流向，构成功率的两个变量是力变量（油压P或作用力F）和流变量（流量q或速度v）。O结点表示在系统中属于并联连接，各键上的力变量相等而流变量之和为零；1结点表示在系统中属于串联连接，各键上流变量相等而力变量之和为零。TF表示不同能量形式间的变换器，TF下标注的字母表示力变量或流变量的转换比值。键上的短横杠表示该键上两变量间的因果关系。全箭头表示控制关系。在三种作用元中容性元和感性元的力变量与流变量之间具有积分或微分关系，因此，根据图3可推导出具有九个状态变量的复杂非线性状态方程。本文对滑台动态特性的研究是从滑台的前冲和运动平稳性两方面入手，用四阶定步长Runge-Kutta法在IBM-PC微型计算机上进行数字仿真,仿真结果分别如图4和图5所示。

2.3滑台前冲

滑台前冲现象是作用在滑台上的负载突然消失（如钻削工作的情况)引起的。在此过程中，滑台的负载F、运动速度V、油缸两腔压力P3和P4的变化可从图4仿真结果看出。当滑台在负载的作用下匀速运动时，油缸无杆腔油液压力较高．油液中聚集了大量的能量。当负载突然消失时，该腔油压随之迅速降低，油液从高压态转入低压态的过程中向系统释放很多能量，致使滑台高速向前冲击。然而，滑台的前冲使油缸有杆腔油液受压引起背压升高，从而消耗掉系统中的一部分能量，对滑台的前冲起到一定的抑制作用。应当看到，在所研究的系统中，自调背压阀的入口压力要受到油缸两腔油压的综合性作用。在负载消失的瞬间，自调背压阀的压力将会迅速地上升，并稳定地处在高于初始背压的数值以上。从图中可见，自调背压调速系统在负载消失瞬间油缸背压力升高的幅度大于传统的调速系统，所以，其油缸有杆腔中油液吸收的能量就多；结果，滑台的前冲量比传统调速系统要小大约20%。可见采用自调背庄调速系统作为驱动系统的滑台在抑制前冲方面具有良好的特性，其中自调背压阀起了很大作用。

2.4滑台的运动平稳性

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当作用于滑台上的负载作周期变化时（比如说铣削加工的情况），滑台的运动速度将要产生一定的波动。为于保证加工质量的要求，必须尽可能地减小其速度波动的范围。而从讨论问题的方便性出发来说，假设负载按正弦波的规律变化，从而得到的数字仿真结果如图5所示。由此可见这个系统与传统的调速系统有着相同的变化规律以及非常接近的数值数字。其中的原因是负载的变化幅度不大，油缸两腔的压力也就没有较大变化，从而最终导致自调背压阀的作用不够明显显示。

2.5 改善措施

通过研究的结果表明，以自调背压调速系统作为驱动系统的滑台，其动态特性要比传统的调速系统好的。要减少滑台的前冲量，就必需在负载消失的瞬间时候迅速提高油缸有杆腔的背压力；要提高滑台的运动平稳性就需增加系统的刚性，主要措施在于减小油液的体积。从系统的结构得知，油缸有杆腔与排油管之间有一很大的容积，如图6a所示。它的存在方面延迟和衰减了自调背压阀的作用，另一方面也降低了系统的刚性，它会限制了前冲特性和运动平稳性的进一步改善。因此，改善滑台动态特性可从两个方法进行处理：即改变油缸容积和改变自调背压阀结构尺寸。通过一系统结构性参数的仿真计算以及结果的比较可以得出这样的结果：当把油缸有杆腔与排油管间容积V4同无杆腔与进油管间容积V3之比由原来的5.5改为1时，如图6b所示，同时，把自调背压阀阀芯底端直径由原来的10mm增加为13mm,阻尼三角槽边长从原来的lmm减小到0.7mm时，可使滑台的前冲量减小30%,过渡过程时间明显缩短了，滑台的运动平稳性也将会得到很大的改善。

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Hydraulic system

Chapter 1 Introduction

Hydraulic Pump Station also known as the stations are independent h- ydraulic device.

It requested by the oil gradually. And controlling the hydraulic oil flow direction, pressure and flow rate, applied to the mainframe and hy- draulic devices separability of hydraulic machinery.

Users will be provided after the purchase hydraulic station and host of implementing agencies (motor oil or fuel tanks) connected with tubing, Hydraulic machinery can be realized from these movements and the work cycle.

Hydraulic pump station is installed, Manifold or valve combination, t- anks, a combination of electrical boxes. Functional components :

Pump device -- is equipped with motors and pumps, hydraulic station is the source of power. to mechanical energy into hydraulic oil pressure can be.

Manifold -- from hydraulic valve body and channel assembled. Right direction for implementation of hydraulic oil, pressure and flow control.

Valve portfolio -- plate valve is installed in up board after board conn- ects with the same functional IC.

Tank -- plate welding semi-closed containers, also loaded with oil filtering network, air filters, used oil, oil filters and cooling.

Electrical boxes -- at the two patterns. A set of external fuse terminal plate; distribution of a full range of electrical control.

Hydraulic Station principle : motor driven pump rotation, which pump oil absorption from the oil tank. to mechanical energy into hydraulic pressure to the station, hydraulic oil through Manifold (or valve combinations) realized the direction, pressure, After adjusting flow pipe and external to the cylinder hydraulic machinery or motor oil, so as to control the direction of the motive fluid transformation force the size and speed the pace of promoting the various acting hydraulic machinery.

1.1 A development course

China Hydraulic (including hydraulic, the same below), pneumatic and seals industrial development process can be broadly divided into three phases, namely : 20 early 1950s to the early 1960s, the initial stage; 60's and 70 for specialized production system ;80~90's growth stage for the rapid development stage. Which, hydraulic industry in the early 1950s from the machine tool industry production of fake Su-grinder, broaching machine, copying lathe, and other hydraulic drive started, Hydraulic Components from the plant hydraulic machine shop, self-occupied. After entering the 1960s, the application of hydraulic technology from the machine gradually extended to the agricultural machinery and mechanical engineering fields, attached to the original velocity of hydraulic shop some stand out as pieces of hydraulic professional production. To the late 1960s, early 1970s, with the development of mechanized production, especially in the second automobile factory in providing efficient, automated equipment, along with the Hydraulic Components manufacturing has experienced rapid development of the situation, a group of SMEs have become professional hydraulic parts factory. 1968

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China's annual output of hydraulic components have nearly 200,000 in 1973, machine tools, agricultural machinery, mechanical engineering industries, the production of hydraulic parts factory has been the professional development of more than 100 and an annual output more than one million. an independent hydraulic manufacturing industry has begun to take shape. Then, hydraulic pieces of fake products from the Soviet Union for the introduction of the product development and technical design combining the products to the pressure, Hypertension, and the development of the electro-hydraulic servo valves and systems, hydraulic application areas further expanded. Aerodynamic than the start of the industrial hydraulic years later, in 1967 began to establish professional pneumatic components factory, Pneumatic Components only as commodity production and sales. Sealed with rubber and plastics, mechanical seals and sealing flexible graphite sealing industry, the early 1950s from the production ordinary O-rings. rubber and plastics extrusion, such as oil seal sealing and seal asbestos products start to the early 1960s, begun production of mechanical seals and flexible graphite sealing products. 1970s, the burning of the former Ministry, a Ministry, the Ministry of Agricultural Mechanization System, a group of professional production plants have been established, and the official establishment of industries to seal industrial development has laid the foundation for growth.

Since the 1980s, in the country's reform and opening up policy guidelines, with the development of the machinery industry, based mainframe pieces behind the conflicts have become increasingly prominent and attracted the attention of the relevant departments. To this end, the Ministry of the original one in 1982, formed the basis of common pieces of Industry, will be scattered in the original machine tools, agricultural machinery, mechanical engineering industries centralized hydraulic, pneumatic and seals specialized factories, placing them under common management infrastructure pieces Bureau, so that the industry in the planning, investment, technology and scientific research and development in areas such as infrastructure pieces Bureau of guidance and support. Since then entered a phase of rapid development, has introduced more than 60 items of advanced technology from abroad, including more than 40 items of hydraulic, pneumatic 7. After digestion and absorption and transformation, now have mass production, and industry-leading products. In recent years, the industry increased the technological transformation efforts, in 1991, Local enterprises and the self-financing total input of about 20 billion yuan, of which more than 1.6 billion yuan Hydraulic. Through technological transformation and technology research, and a number of major enterprises to further improve the level of technology, technique and equipment to be greatly improved. In order to form a higher starting point, specialization, and run production has laid a good foundation. In recent years, many countries in the development of common ownership guidelines, under different ownership SMEs rapid rise showing great vitality. With the further opening up, three-funded enterprises rapid development of industry standards for improving and expanding exports play an important role. Today, China has and the United States, Japan, Germany and other countries famous manufacturers joint ventures or wholly-owned by foreign manufacturers to establish a piston pump / motor, planetary reduction gears, steering gear, hydraulic control valve, hydraulic system, hydrostatic transmission, hydraulic Casting. pneumatic control valve, cylinder, gas processing triple pieces, mechanical seals, rubber and seal products more than 50 production enterprises, attracting foreign investment over 200 million U.S. dollars.

1.2 the current situation

1.21Basic Profiles

After 40 years of efforts, China hydraulic, pneumatic and sealing industry has formed a relatively complete categories. a certain level of technical capacity and the industrial

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system. According to the 1995 Third National Industrial Census statistics, hydraulic, Pneumatic seals and industrial 370,000 annual sales income of 100 million yuan in state-owned, village-run, private and cooperative enterprises, individual, \capital\enterprises with a total of more than 1,300, of which about 700 hydraulic, Pneumatic seals and the approximately 300 thousand. By 1996 with the international trade statistics, the total output value of China's industry hydraulic 2.348 billion yuan, accounting for the world's 6; Pneumatic industry output 419 million yuan, accounting for world No. 10. 1.22 the current supply and demand profiles

Through the introduction of technology, independent development and technological innovation, and high-pressure piston pump, gear pumps, vane pump, General Motors hydraulic valves, tanks, Non-lubricated aerodynamic pieces and various seals of the first large technology products has increased noticeably. stability of the mass production may, for various mainframe products provide a level of assurance. In addition, hydraulic and pneumatic components of the CAD system, pollution control, proportional servo technology has scored some achievements, and is already in production. Currently, hydraulic, pneumatic and seals products total about 3,000 species, more than 23,000 specifications. Among them, there are 1,200 hydraulic varieties, more than 10,000 specifications (including hydraulic products 60 varieties 500 specifications); Pneumatic are 1,350 varieties, more than 8,000 specifications; Rubber seal 350 species more than 5,000 specifications have been basically cater to the different types of mainframe products to the general needs, complete sets of equipment for major varieties of matching rate was over 60%, and started a small amount of exports.

1998 pieces of homemade hydraulic output 4.8 million. sales of about 28 billion (of which about 70% mechanical systems); aerodynamic pieces yield 3.6 million. sales of about 5.5 billion (of which about 60% of mechanical systems); Seals output of about 800 million. sales of about 10 billion (of which about 50% mechanical systems). According to the China Hydraulic Pneumatic Seals Industry Association 1998 annual report, hydraulic product sales rate of 97. 5% (101% for hydraulic), pneumatic 95.9%, 98.7% sealed. This fully reflects the basic marketing convergence.

My hydraulic, pneumatic and sealing industry has attained a great deal of progress, but with mainframe development needs, and the world's advanced level, there are still many gaps, mainly reflected in the product variety, performance and reliability, and so on. Hydraulic products as an example, products abroad only one-third, life for half abroad. In order to meet key mainframe, and mainframe imports of major technology and equipment needs, every year a large number of hydraulic, pneumatic and sealing products imports. According to customs statistics and the analysis of data, in 1998 hydraulic, pneumatic and seals in the import about 200 million U.S. dollars, Hydraulic which about 1.4 billion dollars, aerodynamic nearly 030 million U.S. dollars, sealed about 030 million U.S. dollars. compared with a slight decline in 1997. By sums, currently imported products on the domestic market share of about 30%. 1998 pieces of the domestic market demand for hydraulic total of about six million, the total sales of nearly 40 billion; aerodynamic pieces of the total demand of about 5 million, with sales more than 700 million yuan; Seals total demand of about 1.1 billion. total sales of about 1.3 billion.

1.3 the development trend of the future

1.31 affect the development of the main factors

(1) product development ability, and the level of technological development and speed can not completely meet the advanced mainframe products, major equipment and technology imported equipment and maintenance support;

(2) the number of enterprises manufacturing technology, the level of equipment and