中英文文献翻译-旋转泵

英文原文

Rotary pump

These are built in many different designs and are extremely popular in modern fluid-power system. The most common rotary-pump designs used today are spur-gear, generated-rotary , sliding-vane ,and screw pump ,each type has advantages that make it the most suitable for a given application .

Spur-gear pumps. these pumps have two mating gears are turned in a closely fitted casing. Rotation of one gear ,the driver causes the second ,or follower gear, to turn . the driving shaft is usually connected to the upper gear of the pump .

When the pump is first started ,rotation of gears forces air out the casing and into the discharge pipe. this removal of air from the pump casing produces a partial vacuum on the pump inlet ,here the fluid is trapped between the teeth of the upper and lower gears and the pump casing .continued rotation of the gears forces the fluid out of the pump discharge .

Pressure rise in a spur-gear pump is produced by the squeezing action on the fluid ad it is expelled from between the meshing gear teeth and casing ,.a vacuum is formed in the cavity between the teeth ad unmesh, causing more fluid to be drawn into the pump ,a spur-gear pump is a constant-displacement unit ,its discharge is constant at a given shaft speed. the only way the quantity of fluid discharge by a spur-gear pump of type in figure can be regulated is by varying the shaft speed .modern gear pumps used in fluid-power systems develop pressures up to about 3000psi.

Figure shows the typical characteristic curves of a spur-gear rotary pump. These curves show the capacity and power input for a spur-gear pump at various speeds. At any given speed the capacity characteristic is nearly a flat line the slight decrease in capacity with rise in discharge pressure is caused by increased leakage across the gears from the discharge to the suction side of the pump. leakage in gear pumps is sometimes termed slip. Slip also increase with arise pump discharge pressure .the curve showing the relation between pump discharge pressure and pump capacity is often termed the head-capacity or HQ curve .the relation between power input and pump capacity is the power-capacity or PQ curve .

Power input to a squr-gear pump increases with both the operating speed and discharge pressure .as the speed of a gear pump is increased. Its discharge rate in gallons per minute also rise . thus the horsepower input at a discharge pressure of 120psi is 5hp at 200rpm and about 13hp at 600rpm.the corresponding capacities at these speed and pressure are 40 and 95gpm respectively, read on the 120psi ordinate where it crosses the 200-and 600-rpm HQ curves .

Figure is based on spur-gear handing a fluid of constant viscosity , as the viscosity of the fluid handle increases (i.e. ,the fluid becomes thicker and has more resistance to flow ),the capacity of a gear pump decreases , thick ,viscous fluids may limit pump capacity t higher speeds because the fluid cannot into the casing rapidly enough fill it completely .figure shows the effect lf increased

fluid biscosity on the performance of rotary pump in fluid-power system .at 80-psi discharge pressure the pp has a capacity lf 220gpm when handling fluid of 100SSU viscosity lf 500SSU . the power input to the pump also rises ,as shown by the power characteristics.

Capacity lf rotary pump is often expressed in gallons per revolution of the gear or other internal element .if the outlet of a positive-displacement rotary pump is completely closed, the discharge pressure will increase to the point where the pump driving motor stalls or some part of the pump casing or discharge pipe ruptures .because this danger of rupture exists systems are filled with a pressure –relief valve. This relief valve may be built as of the pump or it may be mounted in the discharge piping.

Sliding-Vane Pumps

These pumps have a number of vanes which are free to slide into or out of slots in the pup rotor . when the rotor is turned by the pump driver , centrifugal force , springs , or pressurized fluid causes the vanes to move outward in their slots and bear against the inner bore of the pump casing or against a cam ring . as the rotor revolves , fluid flows in between the vanes when they pass the suction port. This fluid is carried around the pump casing until the discharge port is reached. Here the fluid is forced out of the casing and into the discharge pipe.

In the sliding-vane pump in Figure the vanes in an oval-shaped bore. Centrifugal force starts the vanes out of their slots when the rotor begins turning. The vanes are held out by pressure which is bled into the cavities behind the vanes from a distributing ring at the end of the vane slots. Suction is through two ports A and AI, placed diametrically opposite each other. Two discharge ports are similarly placed. This arrangement of ports keeps the rotor in hydraulic balance, reliving the bearing of heavy loads. When the rotor turns counterclockwise, fluid from the suction pipe comes into ports A and AI is trapped between the vanes, and is carried around and discharged through ports B and BI. Pumps of this design are built for pressures up to 2500 psi. earlier models required staging to attain pressures approximating those currently available in one stage. Valving , uses to equalize flow and pressure loads as rotor sets are operated in series to attain high pressures. Speed of rotation is usually limited to less than 2500rpm because of centrifugal forces and subsequent wear at the contact point of vanes against the cam-ring surface..

Two vanes may be used in each slot to control the force against the interior of the casing or the cam ring. Dual vanes also provide a tighter seal , reducing the leakage from the discharge side to the suction side of the pump . the opposed inlet and discharge port in this design provide hydraulic balance in the same way as the pump, both these pumps are constant-displacement units. The delivery or capacity of a vane-type pump in gallons per minute cannot be changed without changing the speed of rotation unless a special design is used. Figure shows a variable-capacity sliding-vane pump. It dose not use dual suction and discharge ports. The rotor rums in the pressure-chamber ring, which can be adjusted so that it is off-center to the rotor. As the degree of off-center or eccentricity is changed, a variable volume of fluid is discharged. Figure shows that the vanes create a vacuum so that oil enters through 180 of shaft rotation. Discharge also takes

place through 180 of rotation. There is a slight overlapping of the beginning of the fluid intake function and the beginning of the fluid discharge.

Figure shows how maximum flow is available at minimum working pressure. As the pressure rises, flow diminishes in a predetermined pattern. As the flow decreases to a minimum valve, the pressure increases to the maximum. The pump delivers only that fluid needed to replace clearance floes resulting from the usual slide fit in circuit components.

A relief valve is not essential with a variable-displacement-type pump of this design to protect pumping mechanism. Other conditions within the circuit may dictate the use of a safety or relief valve to prevent localized pressure buildup beyond the usual working levels.

For automatic control of the discharge , an adjustable spring-loaded governor is used . this governor is arranged so that the pump discharge acts on a piston or inner surface of the ring whose movement is opposed by the spring . if the pump discharge pressure rises above that for which the by governor spring is set , the spring is compressed. This allows the pressure-chamber ring to move and take a position that is less off center with respect to the rotor. The pump theb delivers less fluid, and the pressure is established at the desired level. The discharge pressure for units of this design varies between 100 and 2500psi.

The characteristics of a variable-displacement-pump compensator are shown in figure. Horsepower input values also shown so that the power input requirements can be accurately computed. Variable-volume vane pumps are capacity of multiple-pressure levels in a predetermined pattern. Two-pressure pump controls can provide an efficient method of unloading a circuit and still hold sufficient pressure available for pilot circuits.

The black area of the graph of figure shows a variable-volume pump maintaining a pressure of 100psi against a closed circuit. Wasted power is the result of pumping oil at 100psi through an unloading or relief valve to maintain a source of positive pilot pressure. Two-pressure –type controls include hydraulic, pilot-operated types and solenoid-controlled, pilot-operated types. The pilot oil obtained from the pump discharge cannot assist the governor spring. Minimum pressure will result. The plus figure shows the solenoid energized so that pilot oil assists compensator spring. The amount of assistance is determined by the small ball and spring, acting as a simple relief valve. This provides the predetermined maximum operating pressure.

Another type of two-pressure system employs what is termed a differential unloading governor. It is applied in a high-low or two-pump circuit. The governor automatically, Through pressure sensing, unloads the large volume pump to a minimum deadhead pressure setting. Deadhead pressure refers to a specific pressure level established as resulting action of the variable-displacement-pump control mechanism. The pumping action and the resulting flow at deadhead condition are equal to the leakage in the system and pilot-control flow requirements. No major power movement occurs at this time, even though the hydraulic system may be providing a clamping or holding action while the pump is in deadhead position

The governor is basically a hydraulically operated, two-pressure control with a differential piston that allows complete unloading when sufficient external pilot pressure is applied to pilot

unload port.

The minimum deadhead pressure setting is controlled by the main governor spring A. the maximum pressure is controlled by the relief-valve adjustment B. the operating pressure for the governor is generated by the large-volume pump and enters through orifice C.

To use this device let us assume that the circuit require a maximum pressure of 1000psi, which will be supplied by a 5-gpm pump. It also needs a large flow (40gpm) at pressure up to 500psi; it continues to 1000pso at the reduced flow rate. A two-pump system with an unloading governor on the 40-gpm pump at 500psi to a minimum pressure setting of 200psi (or another desired value) , which the 5-gpm pump takes the circuit up to1000psi or more.

Note in figure that two sources of pilot pressure are required. One ,the 40-gpm pump, provides pressure within the housing so that maximum pressure setting can be obtained. The setting of the spring, plus the pressure within the governor housing, determines the maximum pressure capacity of the 40-gpm pump. The second pilot source is the circuit proper, which will go to 1000psi. this pilot line enters the governor through orifice D and acts on the unloading piston E . the area of piston E is 15 percent greater than the effective area of the relief poppet F. the governor will unload at 500psi and be activated at 15percent below 500psi, or 425psi. By unloading, we mean zero flow output of the 40-gpm pump.

As pressure in the circuit increases from zero to 500psi, the pressure within the governor housing also increases until the relief-valve setting is reached, at which time the relief valve cracks open, allowing flow to the tank.

The pressure drop in the hosing is a maximum additive value, allowing the pump to deadhead. Meanwhile, the system pressure continues to rise above 700psi, resulting in a greater force on the bottom of piston E than on the top. The piston then completely unseats poppet F, which results in a further pressure drop within the governor horsing to zero pressure because of the full-open position of the relief poppet F. flow entering the housing through orifice is directed to the tank pass the relief poppet without increasing the pressure in housing. The deadhead pressure of the 40-gpm pump then decreases to the lower set value. Thus , at the flow rate to the unloading governor ,the 40gpm pump goes to deadhead. The flow rate to the circuit decreases to 5gpm as the pressure to 1000psi, the 5-gpm pump is also at its deadhead setting, thus only holding system pressure.The 4-gpm pump unloads its volume at 500psi. It requires a system pressure of 600psi to unload the 40-gpm pump to its minimum pressure of 200psi. the 600-psi pilot supply enters through orifice D and acts on the differential piston E. The pumps volume is reduced to zero circuit-flow output at 500psi. The additional 100-psi pilot pressure is required to open poppet F completely and allow the pressure within the housing to decrease to zero.As circuit pressure decreases ,both pumps come back into service in a similar pattern.

CNC machine tools

While the specific intention and application for CNC machines vary from one machine type to another, all forms of CNC have common benefits. Here are but a few of the more important benefits offered by CNC equipment.

The first benefit offered by all forms of CNC machine tools is improved automation.The operator intervention related to producing work pieces can be reduced or eliminated. Many CNC machines can run unattended during their entire machining cycle, freeing the operator to do other tasks. This gives the CNC user several side benefits including reduced operator fatigue, fewer mistakes caused by human error, and consistent and predictable machining time for each workpiece. Since the machine will be running under program control, the skill level required of the CNC operator (related to basic machining practice) is also reduced as compared to a machinist producing workpieces with conventional machine tools.

The second major benefit of CNC technology is consistent and accurate workpieces. Today's CNC machines boast almost unbelievable accuracy and repeatability specifications. This means that once a program is verified, two, ten, or one thousand identical workpieces can be easily produced with precision and consistency.

A third benefit offered by most forms of CNC machine tools is flexibility. Since these machines are run from programs, running a different workpiece is almost as easy as loading a different program. Once a program has been verified and executed for one production run, it can be easily recalled the next time the workpiece is to be run. This leads to yet another benefit, fast change over. Since these machines are very easy to set up and run, and since programs can be easily loaded, they allow very short setup time. This is imperative with today's just-in-time (JIT) product requirements.

Motion control - the heart of CNC

The most basic function of any CNC machine is automatic, precise, and consistent motion control. Rather than applying completely mechanical devices to cause motion as is required on most conventional machine tools, CNC machines allow motion control in a revolutionary manner2 . All forms of CNC equipment have two or more directions of motion, called axes. These axes can be precisely and automatically positioned along their lengths of travel. The two most common axis types are linear (driven along a straight path) and rotary (driven along a circular path).

Instead of causing motion by turning cranks and handwheels as is required on conventional machine tools, CNC machines allow motions to be commanded through programmed commands. Generally speaking, the motion type (rapid, linear, and circular), the axes to move, the amount of motion and the motion rate (feedrate) are programmable with almost all CNC machine tools.

A CNC command executed within the control tells the drive motor to rotate a precise number of times. The rotation of the drive motor in turn rotates the ball screw. And the ball screw drives the linear axis (slide). A feedback device (linear scale) on the slide allows the control to confirm that the commanded number of rotations has taken place3.

Though a rather crude analogy, the same basic linear motion can be found on a common table vise. As you rotate the vise crank, you rotate a lead screw that, in turn, drives the movable jaw on

the vise. By comparison, a linear axis on a CNC machine tool is extremely precise. The number of revolutions of the axis drive motor precisely controls the amount of linear motion along the axis.

How axis motion is commanded - understanding coordinate systems .

It would be infeasible for the CNC user to cause axis motion by trying to tell each axis drive motor how many times to rotate in order to command a given linear motion amount4. (This would be like having to figure out how many turns of the handle on a table vise will cause the movable jaw to move exactly one inch!) Instead, all CNC controls allow axis motion to be commanded in a much simpler and more logical way by utilizing some form of coordinate system. The two most popular coordinate systems used with CNC machines are the rectangular coordinate system and the polar coordinate system. By far, the more popular of these two is the rectangular coordinate system.

The program zero point establishes the point of reference for motion commands in a CNC program. This allows the programmer to specify movements from a common location.If program zero is chosen wisely, usually coordinates needed for the program can be taken directly from the print.

With this technique, if the programmer wishes the tool to be sent to a position one inch to the right of the program zero point, X1.0 is commanded. If the programmer wishes the tool to move to a position one inch above the program zero point, Y1.0 is commanded. The control will automatically determine how many times to rotate each axis drive motor and ball screw to make the axis reach the commanded destination point . This lets the programmer command axis motion in a very logical manner.All discussions to this point assume that the absolute mode of programming is used. The most common CNC word used to designate the absolute mode is G90. In the absolute mode, the end points for all motions will be specified from the program zero point. For beginners, this is usually the best and easiest method of specifying end points for motion commands. However, there is another way of specifying end points for axis motion.

中文译文

旋转泵

旋转泵应用于不同的设计中，在流体动力系统中极其常用。今天最常用的旋转泵是外齿轮泵、内齿轮泵、摆线转子泵、滑动叶片泵和螺旋泵。每种类型的泵都有优点，适合于特定场合的应用。

直齿齿轮泵，这种泵有两个啮合的齿轮在密封壳体内转动。第一个齿轮即主动轮的回转引起第二个齿轮即从动轮的回转。驱动轴通常连接到泵上面的齿轮上。

当泵首次启动时，齿轮的旋转迫使空气离开壳体进入排油管。这种泵内空气运动使泵吸入口处形成了真空，于是外部油箱的液体在大气压的作用下，由泵的入口进入，聚集在上下齿轮和泵壳体之间，齿轮连续的旋转使液体流出泵的出口。

直齿齿轮泵的压力的升高是由挤压啮合齿轮和腔体内的液体产生的。当齿轮脱开啮合时，腔内形成真空，使更多的液体被吸入泵内。直齿齿轮泵是定排量的元件，当轴转速不变时，输出流量恒定。只有一种方法即改变输入轴的转速，能调节这种直齿齿轮泵的排量。现代应用在流体动力系统的齿轮泵的压力可达3000psi。

图示为直齿齿轮泵的典型特性曲线。这些曲线表明了泵在不同速度下的流量和输入功率。当速度给定时，流量曲线接近于一条水平的直线。泵的流量随出口压力的升高而稍有降低，这是由于泵的出油口到吸油口的齿轮径向泄漏所增加而造成的。渗漏有时定义为泄漏，泵出口压力的增加也会使泄漏增加。表征泵的出口压力和流量之间关系曲线常叫做水头流量曲线或泵的HQ曲线；泵的输入功率和泵流量关系曲线叫做功率流量特性曲线或PQ曲线。

直齿齿轮泵的输入功率随输入速度和出口压力的增加而增加。随着齿轮泵速度的增加，流量（加仑/分）也增加。于是在出口压力为120psi，转速为200rpm时，输入功率是5马力。在转速为600rpm时，输入功率是13马力。纵坐标压力是120psi，横坐标是200rpm和600rpm 时，在HQ曲线上可以读出相应的流量分别为40gpm和95gpm。

图示是直齿齿轮泵在粘度不变时的情况。随着流体粘度的增加（即流体变稠，不易流动），齿轮泵的流量降低。粘稠的流体在油泵高速运转时，因为这种流体在油泵中不能迅速进入泵体完全充满真空区，所以油流量受到限制。图示为在流体动力系统中流体粘度的增大对旋转泵工作情况的影响。当流体的粘度值为100SSU，出口压力为80psi时，泵流量为220gpm。当流体的粘度值为500SSU时，泵流量减少到150gpm。由功率特性曲线可知，泵输入功率也会增加。

可以用齿轮或其他内部元件每转一圈输出多少加仑来表示泵的流量。如果封闭定量泵的出口，则出口压力将会增加，直至驱动马达停止或泵内其他部分或排油管破裂。由于存在着破裂的危险，几乎所有的流体动力系统都安装压力溢流阀。这种溢流阀可安装在泵内，也可安装在排油管路。

滑动式叶片泵

这些泵有大量的叶片，叶片能在转子的槽内自由的滑进滑出。当驱动转子时，离心力，弹簧或压力油使叶片伸出槽子，顶在泵壳体的内腔或凸轮环上。随着转子的旋转，叶片之间的流体经过吸油口时，完成吸油。流体顺着泵壳体到达排出口。在排出口，流体被排出，进入排油管。

图示的滑动式叶片泵中的叶片安装在椭圆形的腔内。当转子开始旋转时，离心力使叶片伸出槽子。同时叶片又受到其底部腔内压力油的作用力，压力油来源于槽子端部的配流盘。吸油口通过A和A1口相通，他们位于直径的相对位置。同样两排油口位于类似的位置。油口这样配置，使叶片转子保持压力平衡，从而使轴承不受重载影响。当转子逆时针旋转时，

从吸油管出来的流体进入A和A1口，聚集在叶片之间，沿周向流动后，通过B和B1口排出。这样设计的泵压力可达2500psi。的泵必须分级才能达到这么大的压力，而现在用一级泵即可达到。在转子上应用均流均压阀可以达到高压。转速通常限制在2500rpm这是因为考虑到离心力和凸轮环表面叶片之间的磨损。图示为泵在转速为1200rpm粘度在100F的条件下的特性曲线。

每个槽内安装两个叶片可以控制其作用于壳体内部和凸轮环上的力。双叶片会产生更紧的密封，能减少从排油口到吸油口之间的泄漏这种入口和出口相对应的设计也能维持液压平衡。这些都是定量泵。

不改变转速就不能改变叶片泵的流量，除非油泵采用特殊设计。图示为滑动式变量叶片泵。它不用双吸油和排油口。转子在压力腔内转动，转子形成的偏心量是可调的。随着偏心的程度或偏心率的变化，流体的流量也随着变化。图示为转子在旋转180°范围内，产生一真空度以便于油液进入，同时压油区也在180°范围内旋转。吸油区和压油区的起始段梢有重叠。

图示，在最小的工作压力下可以得到最大的流量。随着压力的升高，流量按预设的规律减少。当流量减到最小值，压力增大到最大值。泵只需要提供补充回路中元件滑动配合间隙中泄漏流体。

这种变量泵的设计可以保护管路，溢流阀不是必须的。其他回路中，为阻止局部压力超过正常压力水平，可以用安全阀或溢流阀来控制。

为了自动控制流量，采用可变弹簧负载调节器。安装这种调节器，泵的出口压力作用于活塞或定子内表面，压缩的弹簧产生位移。如果泵的出口压力高于调节器弹簧的设定值时，弹簧被压缩。这使压力环（定子）移动，减少相对于定子的偏心量，于是，泵的流量减少，得到所需的压力。这种油泵设计的出口压力在100psi和2500psi之间。

图示为变量泵补偿器的特性，标出输入功率值，可以准确计算所需的输入功率。变量泵可以预先设定不同压力值的变化规律。高低压泵控制既能提供有效的卸荷回路，也能为先导控制回路提供足够压力。

图示阴影区域为变量泵在背压100psi压力下的闭式回路。油液以100psi卸荷阀或溢流阀排出，可以维持正常的控制回路压力，这些是消耗的功率。两级压力控制回路包括：先导液压控制和电磁控制。图示负号表示电磁铁不带电，先导控制油回油箱。于是泵排出的控制油的力小于调节器弹簧力，所以得到最小压力。图示正号为电磁铁带电，控制油的力大于调节器弹簧力。与简单的溢流阀原理一样，小球和弹簧决定控制力的大小。这样预先设定最大工作压力。

另一种两级压力控制系统是利用所谓的差动卸荷调节器。它应用于高低压或双泵回路中。调节器通过压力传感器自动卸荷大流量泵以达到最小的空载压力设定值。空载压力指的是由于变量泵控制机构工作所形成的特定压力。泵的实际空载流量等于系统的泄漏量与控制流量之和。当泵空载时，即使液压系统在提供加紧或保压作用，也不会需要较大的功率。

调节器是液压操纵的，差动活塞带有双压力控制，当外部控制压力作用于控制卸荷口时，差动活塞允许完全卸荷。

空载压力的最小设定值由调节器主弹簧A控制。最大压力由溢流阀调节点B控制。调节器的操作压力由大容积泵提供，从小孔C进入。

为了说明如何使用这种装置，假设回路需要1000psi的最大压力，由一个5-gpm来提供。在压力达到500psi时，需要大流量（40gpm），继续上升到1000psi，流量减少。由流量为40-gpm的带有卸荷调节器的泵组成的双泵系统可满足要求。我们可以把40-gpm的泵从500psi卸荷压力调整至200psi最小设定压力（或另一需求值），这样5-gpm泵可以使回路达到1000psi或更高压力。

图中为双泵系统控制压力源。由一个40-gpm的泵提供调节器腔内压力，就可以达到最大设定压力。弹簧设定力加上调节器的腔内压力共同决定了40-gpm泵的最大压力。第二个控制源是特殊的回路，它能达到1000psi。控制油通过小孔D进入调节器作用于卸荷活塞E。活塞E面积比安全阀中提动阀F的有效面积大15％。因此卸荷差动力大约为15％。调节器将在500psi卸荷，会在500psi以下15％或425psi时起作用。这里所谓的卸荷，指的是40-gpm 的泵无输出量。

随着回路中压力从0到500psi的增加，调节器腔内的压力也随着增加，直到溢流阀的设定值时，溢流阀打开，流体流出油箱。

调节器腔内的压力降是最大的叠加值，允许油泵达到卸荷状态。同时，当系统压力继续增加超过700psi时，导致活塞E最底部的压力比顶部的压力大。活塞使提升阀F完全打开，溢流提升阀全部开启导致调节器腔内压力进一步下降至零。流体通过小孔C进入调节器腔，经过溢流提升阀直接回油箱，不增加调节器腔内的压力。40-gpm的泵卸荷压力可以减小至更低的设定值。调整卸荷调节器，40-gpm的泵达到卸荷。随着压力到1000psi，回路的流量减至5gpm。在1000psi时，5-gpm泵也达到卸荷设定，于是流量仅仅维持系统压力。在500psi 时，40-gpm的油泵卸荷。需要600psi的系统压力把40gpm的泵卸荷到最小压力200psi。600psi 的先导控制油通过孔D进入并作用于差动活塞E。在500psi时，泵流量减少到零。100psi 的附加压力需要完全打开提升阀，使调节器腔内的压力减小至零。当回路压力减小时，两个泵以同样的方式来工作。

数控机床

虽然各种数控机床的功能和应用各不相同，但它们有着共同的优点。这里是数控设备提供的比较重要的几个优点。

各种数控机床的第一个优点是自动化程度提高了。零件制造过程中的人为干预减少或者免除了。整个加工循环中，很多数控机床处于无人照看状态，这使操作员被解放出来，可以干别的工作。数控机床用户得到的几个额外好处是：数控机床减小了操作员的疲劳程度，减少了人为误差，工件加工时间一致而且可预测。由于机床在程序的控制下运行，与操作普通机床的机械师要求的技能水平相比，对数控操作员的技能水平要求（与基本加工实践相关）也降低了。

数控技术的第二个优点是工件的一致性好，加工精度高。现在的数控机床宣称的精度以及重复定位精度几乎令人难以置信。这意味着，一旦程序被验证是正确的，可以很容易地加工出2个、10个或1000个相同的零件，而且它们的精度高，一致性好。大多数数控机床的第三个优点是柔性强。由于这些机床在程序的控制下工作，加工不同的工件易如在数控系统中装载一个不同的程序而己。一旦程序验证正确，并且运行一次，下次加工工件的时候，可以很方便地重新调用程序。这又带来另一个好处—可以快速切换不同工件的加工。由于这些机床很容易调整并运行，也由于很容易装载加工程序，因此机床的调试时间很短。这是当今准时生产制造模式所要求的。

任何数控机床最基本的功能是具有自动、精确、一致的运动控制。大多数普通机床完全运用机械装置实现其所需的运动，而数控机床是以一种全新的方式控制机床的运动。各种数控设备有两个或多个运动方向，称为轴。这些轴沿着其长度方向精确、自动定位。最常用的两类轴是直线轴（沿直线轨迹）和旋转轴（沿圆形轨迹）。普通机床需通过旋转摇柄和手轮产生运动，而数控机床通过编程指令产生运动。通常，几乎所有的数控机床的运动类型（快

速定位、直线插补和圆弧插补）、移动轴、移动距离以及移动速度（进给速度）都是可编程的。

数控系统中的CNC指令命令驱动电机旋转某一精确的转数，驱动电机的旋转随即使滚珠丝杠旋转，滚珠丝杠将旋转运动转换成直线轴（滑台）运动。滑台上的反馈装置（直线光栅尺）使数控系统确认指令转数已完成。

普通的台虎钳上有着同样的基本直线运动，尽管这是相当原始的类比。旋转虎钳摇柄就是旋转丝杠，丝杠带动虎钳钳口移动。与台虎钳相比，数控机床的直线轴是非常精确的，轴的驱动电机的转数精确控制直线轴的移动距离。

轴运动命令的方式--理解坐标

对CNC用户来说，为了达到给定的直线移动量而指令各轴驱动电机旋转多少转，从而使坐标轴运动，这种方法是不可行的。（这就好像为了使钳口准确移动1英寸需要计算出台虎钳摇柄的转数！）事实上，所有的数控系统都能通过采用坐标系的形式以一种较为简单而且合理的方式来指令轴的运动。数控机床上使用最广泛的两种坐标系是直角坐标系和极坐标系。目前用得较多的是直角坐标系。

编程零点建立数控程序中运动命令的参考点。这使得操作员能从一个公共点开始指定轴运动。如果编程零点选择恰当，程序所需坐标通常可从图纸上直接获得。

如果编程员希望刀具移动到编程零点右方1英寸（25.4毫米）的位置，则用这种方法指令X1.0即可。如果编程员希望刀具移动到编程零点上方1英寸的位置，则指令Y1.0。数控系统会自动确定（计算）各轴驱动电机和滚珠丝杠要转动多少转，使坐标轴到达指令的目标位置。这使编程员以非常合理的方式命令轴的运动。

理解绝对和相对运动

至此，所有的讨论都假设采用的是绝对编程方式。用于指定绝对方式的最常用的数控代码是G90。绝对方式下，所有运动终点的指定都是以编程零点为起点。对初学者来说，这通常是最好也是最容易的指定轴运动终点的方法，但还有另外一种指定轴运动终点的方法。

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利用神经网络预测轴向柱塞泵的性能 Mansour A Karkoub a, Osama E Gad a, Mahmoud G Rabie b a--就读于科威特的科威特大学工程与石油学院 b--就读于埃及开罗的军事科技大学 摘要 本文推导了应用于轴向柱塞泵（斜轴式）的神经网络模型。该模型采用的数据是由一个实验装置获得的。这个正在进行的研究的目的是降低柱塞泵在高压下工作时的能量损耗。然而，在最初我们要做一些研究来预测当前所设计的泵的响应。神经网络模型具有前反馈的结构，并在测验过程中使用Levenberg-Marquardt优化技术。该模型能够准确地预测柱塞泵的动态响应。 1、简介 可变排量轴向柱塞泵是在流体动力系统中经常要用到的重要设备，如液压动力供应控制和静液压传动驱动器的控制。本装置具有变量机制和功率-重量比特性，使其最适合于高功率电平的控制。所设计的这种轴向柱塞泵拥有可靠性和简便的特点，然而其最重要的特征是可以变量输出。 人们在轴向柱塞泵领域已经做了很多研究，但是本文将只论述一下少数几人所做的贡献。 Kaliafetis和Costopoulos[5]用调压器研究了轴向柱塞变量泵的静态和动态特性。所提出的模型的精确度依赖于制造商提供的动态运行曲线等数据。他们得出结论，运行条件对泵的动态行为是非常关键的，而泵的动态行为可以通过减小压力设定值进行改善。Harris等人[4]模拟和测量了轴向柱塞泵的缸体压力和进油流量脉动。Kiyoshi和Masakasu[7]研究了斜盘式变量输送的轴向柱塞泵在运行时刻的实验上和理论上的静态和动态特性。并提出了一种新的方法来预测泵在运行过程中的响应。也对研究泵特性的新方法的有效性进行了实验验证，实验中使用了一个有宽、短而深的凹槽的配流盘。Edge和Darling[2]研究了液压轴向柱塞泵的缸体压力和流量。这个得出的模型经过了实验检验。对于配流盘、缸体上设计的退刀槽和泵的流量脉动对泵特性的影响都进行了验证。 人们已证实了一种可替代的建模技术——神经网络（NN）能取得良好的效果，特别是对于高度非线性的系统。这种技术是模仿人脑获取信息的功能。Karkoub 和Elkamel[6]用神经网络模型预测了一个长方形的气压轴承的压力分布。所设计的这种模型在预测压力分布和承载能力方面比其他可用的工具更加精确。Gharbi 等人[3]利用神经网络预测了突破采油。其表现远远优于常见的回归模型或有限差分法。李等人[8]用神经网络模型NNS和鲍威尔优化技术对单链路和双链路的倒立摆进行了建模和控制。研究者们取得了理想的结果。Panda等人[9]应用NNS在普拉德霍湾油田对流体接触进行了建模。所得到的模型预测的目标油井中的流量分配比传统的以回归为基础的技术更准确。Aoyama等人[1]已经推导出一个神经网络模型来预测非最小相系统的响应。所开发出的的模型被应用于Van de Vuss反应器和连续搅拌式生物反应器，所得到的结果是令人满意的。 本文研究利用神经网络解决轴向柱塞泵（斜轴式）在一定的供油压力下的建模。本文首先会描述用于收集实验数据的实验装置，然后将会简要介绍神经网络建模程序。 2、实验装置

英文文献及中文翻译

毕业设计说明书 英文文献及中文翻译 学院：专 2011年6月 电子与计算机科学技术软件工程

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外文翻译中英对照版

VOLUME 30 ISSUE 2 October 2008 Journal of Achievements in Materials and Manufacturing Engineering Copyright by International OCSCO World Press. All rights reserved.2008 151 Research paper 2008年十月期2卷30 材料与制造工程成果期刊 版权所有：国际OCSCO 世界出版社。一切权利保有。2008 ？？151研究论文 1. Introduction Friction stir welding (FSW) is a new solid-state welding method developed by The Welding Institute (TWI) in 1991 [1]. The weld is formed by the excessive deformation of the material at temperatures below its melting point, thus the method is a solid state joining technique. There is no melting of the material, so FSW has several advantages over the commonly used fusion welding techniques [2-10]. 1.导言摩擦搅拌焊接（FSW）是焊接学？会于1991年研发的一种新型固态焊接方法。这种焊接？是由材料在低于其熔点的温度上过量变形形成，因此此技术是一种固态连接技术。材料不熔化，所以FSW 相比常用的熔化焊接技术有若干优势。例如，在焊接区无多孔性或破裂，工件（尤其薄板上）没有严重扭曲，并且在连接过程中不需要填料、保护气及昂贵的焊接准备there is no significant distortion of the workpieces (particularly in thin plates), and there is no need for filler materials, shielding gases and costly weld preparation during this joining process. FSW被认为是对若干材料例如铝合金、镁合金、黄铜、钛合金及钢最显著且最有潜在用途的焊接技术FSW is considered to be the most remarkable and potentially useful welding technique for several materials, such as Al-alloys, Mg-alloys, brasses, Ti-alloys, and steels [1-16]. 然而，在FSW过程中，用不合适的焊接参数能引起连接处失效，并且使FSW连接处的力学性能恶化。However, during FSW process using inappropriate welding parameters can cause defects in the joint and deteriorate the mechanical properties of the FSW joints [2, 3]. 此技术起初就主要是为低熔点材料如铝合金、镁合金及铜合金而广泛研究的。The technique has initially been widely investigated for mostly low melting materials, such as Al, Mg and Cu alloys. 此技术已被证明是很有用的，尤其在连接用于航空航天用途的如高合金2XXX及7XXX系列铝合金等难熔高强度的铝合金。It has proven to be very useful, particularly in the joining of the difficult-to-fusion join high strength Al-alloys used in aerospace applications, such as highly alloyed 2XXX and 7XXX series aluminium alloys. 做出Al-5086 H32型板摩擦搅拌对焊的高强度、抗疲劳及断裂的力学性能？。The difficulty of making high-strength, fatigue and fracture resistant Mechanical properties of friction stir butt-welded Al-5086 H32 plate G. .am a,*, S. Gü.lüer b, A. .akan c, H.T. Serinda. a a Mustafa Kemal University, Faculty of Engineering and Architecture, 31040 Antakya, Turkey a 土耳其安塔卡亚31040，Mustafa Kemal大学建筑工程系 b General Directorate of Highways of Turkey, Ankara, Turkey b 土耳其安卡拉土耳其高速公路总理事会？ c Abant Izzet Baysal University, Faculty of Engineering an d Architecture, 14280 Bolu, Turkey c 土耳其Bolu 14280 Abant Izzet Baysal 大学建筑工程系 * Corresponding author: E-mail address: gurelcam@https://www.wendangku.net/doc/1718132112.html, *相关作者电子邮箱地址：gurelcam@https://www.wendangku.net/doc/1718132112.html, Received 30.06.2008; published in revised form 01.10.2008

分子生物学文献翻译

在旱地土壤中产甲烷古菌活性对养牛业的影响 维维安radl1,5，安德烈亚斯gattinger1,5，艾莉卡时ˇ一′可娃′2,3，安娜NEˇmcova′2,3，Jiri Cˇuhel2,3，米洛斯拉夫的ˇimek2,3，让查尔斯munch1,4，迈克尔schloter4和Dana elhottova′2 1土壤生态学，慕尼黑工业大学，上施莱斯海姆，慕尼黑，德国；2生物中心，土壤生物学研究所，Cˇ艾斯克′不得ˇjovice，捷克共和国；3生物科学，南波西米亚州大学，Cˇ艾斯克′不得ˇjovice，捷克共和国；4gsf国家研究中心环境与健康，土壤生态，Neuherberg学院，德国。 在本研究中，我们测试的假设是动物的行走与作为越冬牧场土壤中的甲烷有机物有关。因此，捷克共和国指出，在波西米亚南部的一个农场中，甲烷排放量和产甲烷菌种群对牛有不同程度的影响。在春天，甲烷排放与动物影响的梯度相一致。分析应用磷脂，该古细菌量最高的影响，发现部分（SI）对其有影响，其次是温和的影响（MI）没有影响。对于产甲烷菌的实时显示甲基辅酶M还原酶（MCRA）基因的定量PCR分析观察到了相同的趋势。检测单不饱和脂肪酸异戊烯基侧链的碳氢化合物（i20:1）表示的乙酸分解的存在影响牛产甲烷菌。这个结果是由mcrA基因序列分析证实得到的，这表明，所分析的克隆的33%属于甲烷。克隆序列的大部分（41%）与未培养瘤胃有关。由此可得到的假设是，相当大的一部分来自放牧本身产生甲烷的区域。相比于春天采样，在秋天，古细菌的生物量和mcrA数显著减少主要用于截面MI基因观察。可以得出结论，5个月后没有牛的影响，严重影响了部分保持其产甲烷的潜力，而在温和的冲击后甲烷生产潜力。期刊名称（2007）1，443，452–；DOI: 10.1038/ismej.2007.60；网上公布19七月2007 学科类别：微生物生态学和自然栖息地的功能多样性 关键词：多样性；甲烷排放；甲基辅酶M还原酶 引言 农业对于在土壤和植物生物量的二氧化碳（OCA，2006）气体减排和系统隔离提供了巨大的潜力。在这方面，山地草原在低投入农业系统中被认为是作为温室气体甲烷（CH4）（胡¨tsch等人。，1994）和只有微弱的来源的氧化亚氮（N2O）（莫西尔等人。，1991）。 然而，当草原用作牧场放牧时这些减排潜力可以改变。例如，克莱顿等人（1994）发现， 一个放牧的牧场的N2O排放量比不放牧的草地高三倍，并且推测踩踏和排泄的相互作用会刺激这个过程。动物踩踏时通过土壤压实造成土壤通气减少，从而增强的反硝化率（menneer等人，2005）。此外，踩踏可以使丰富的有机碳物质从粪便进入土壤，刺激微生物代谢，从而增加在较低的土壤深度氧的需求（Sˇimek 等人，2006）。厌氧环境和可用的有机碳可能有利于甲烷碳。事实上，一些研究表明，在施用有机肥后，甲烷排放量的时间会增加。

仪表板外文文献翻译、中英文翻译、外文翻译

Dashboard From Wikipedia, the free encyclopedia This article is about a control panel placed in the front of the car. For other uses, see Dashboard (disambiguation). The dashboard of a Bentley Continental GTC car A dashboard (also called dash, instrument panel (IP), or fascia) is a control panel located directly ahead of a vehicle's driver, displaying instrumentation and controls for the vehicle's operation. Contents 1.Etymology 2.Dashboard features 3.Padding and safety 4.Fashion in instrumentation 5.See also 6.References Etymology Horse-drawn carriage dashboard Originally, the word dashboard applied to a barrier of wood or leather fixed at the front of a horse-drawn carriage or sleigh to protect the driver from mud or other debris "dashed up" (thrown up) by the horses' hooves.[1] Commonly these boards did not perform any additional function other than providing a convenient handhold for ascending into the driver's seat, or a small clip with which to secure the reins when not in use. When the first "horseless carriages" were constructed in the late 19th century, with engines mounted beneath the driver such as the Daimler Stahlradwagen, the simple dashboard was retained to protect occupants from debris thrown up by the cars' front wheels. However, as car design evolved to position the motor in front of the driver, the dashboard became a panel that protected vehicle occupants from the heat and oil of the engine. With gradually increasing mechanical complexity, this panel formed a convenient location for the placement of gauges and minor controls, and from this evolved the modern instrument panel,