【導(dǎo)讀】的運(yùn)動軌跡有最小的橫向位移。滿意的液壓支架。所選擇的參數(shù)是最優(yōu)的。數(shù)伴隨著一個合適的系統(tǒng)的數(shù)學(xué)模型的出現(xiàn)而出現(xiàn)。有了這種數(shù)學(xué)函數(shù)模型，加上一臺好的計算機(jī)的支持，一定能找。分，它用來支護(hù)采煤工作面的巷道。它由兩組四連桿機(jī)構(gòu)組成，如圖2所示．四。如果不是這種情況，液壓支架將不能很好的工作，因?yàn)?。支架工作在運(yùn)功的地層上。實(shí)驗(yàn)室測試了一液壓支架的原型。因此，重新設(shè)計很有必要。這會減少支架的承受能力。AEDB改變這種設(shè)計方案。首先，有必要進(jìn)一步研究適當(dāng)?shù)囊簤褐Ъ艿臋C(jī)械模型。的兩個四連桿機(jī)構(gòu)FEDG和AEDB的運(yùn)動來模擬。因此，設(shè)計任務(wù)就是通。理想的連接長度值。相應(yīng)復(fù)數(shù)a3，a5，a6的尺寸是確定的。給出了設(shè)計變量的上下約束條件。然而端點(diǎn)C的計算軌跡L可能有些偏離，因?yàn)樵谶\(yùn)動中存在一些干擾因。樣，函數(shù)h用來考慮參數(shù)以a1，a2，a4的誤差值△a1，△a2，△a4的最大允許值。矢量，也就是意味著響應(yīng)變量的矢量v=[v1…

　　

【正文】 based hydraulic systems also have obvious cost advantages over oilbased fluid. First， nontoxic， biodegradable synthetic additives for water cost ＄ 5 to ＄ 6 per gallon. One gallon of concentrate can make 20 gallons of a 5% solution， so the cost of waterbased hydraulic fluid actually can be less than 30 cents per gallon. Considering the costs associated with preventing and cleaning up environmental contamination， waterbased hydraulic systems hold the potential for tremendous cost saving at the plant level. Oil that has leaked already bees a very important problem. It must be collected ， properly contained. Water containing synthetic additives， however， can by dumped into plant effluent systems. Costs saving at the plant level don’t stop at the lower cost of the fluid and its disposal. Because waterbased hydraulic fluid consists of 10 parts water and one part synthetic additives， 5 gallons of additive mixes with water to make 100 gallons of waterbased fluid. A 50 gallon container is certainly easier to handle than two 55 gallon drums， so warehousing is simple， cleaner， and less cluttered. Transportation costs also are lower. Other potential plantwide saving include improved safety for workers because the waterbased fluid is nontoxic as well as nonflammable. These attributes can reduce plant insurance rate. Spills cost less to clean up because granular absorbents or absorbent socks are unnecessary. Water is “hot” again. The oil embargo in the 1970s sparked interest in waterbased fluids as a lesscostly alternative to oils. Even the most expensive water additives became attractive when designers learned that one gallon of concentrate would make 20 gallons of fluid. As oil prices gradually dropped， so did interest in waterbased hydraulics. In retrospect， interest in waterbased fluids centered around their cost saving potential. Most designers lost interest when they discovered that they could not just change the fluid in their systems from oil to water without making other substantial changes. They then bee reluctant to accept other “disadvantages”， read substantial changes of switching over to waterbased hydraulics. What were viewed as disadvantages were really different rules that apply to waterbased hydraulic systems? Designers probably resisted learning more about waterbased hydraulic because they were intimated by all the work required to lean about how to design a new system or retrofit an older system. By closing their minds to this different technology， they missed the many other advantage of waterbased fluid beyond initial cost. Now that environment concerns have added disposal costs to the price of hydraulic fluids， waterbased hydraulics has again bee a hot topic. Fighting freeze Waterbased hydraulic systems do， of course， have limits to their applications. One limitation is the potential of freezing. This possibility is probably the most significant blockade to more widespread application of waterbased systems，especially in the mobile equipment industry. Longwall mining is by far the largest sector of mobile equipment that has been able to take advantage of waterbased systems. Temperatures underground do not approach the freezing point of water， and fire resistance is essential. Mobile and even marine equipment used in temperature climates could cash in one the advantages of waterbased systems， but there is no guarantee that such equipment always will be used in abovefreezing temperatures. Nevertheless， adding an antifreeze to a waterbased fluid can depress its freezing temperature to well below 32 F. Ethylene glycolused in automotive antifreeze is toxic and is not biodegradable， so its use for antifreeze in waterbased hydraulic fluid would defeat the environmental advantage waterbased fluid has. There is an alternative. Propylene glycol is not toxic and is biodegradable. It costs more than ethylene glycol and is not quite as effective antifreeze， so it must be used in slightly higher concentrations. Two more techniques to reduce freezing potential are to keep fluid circulating continuously and use hose where practical. Sealing the system A sealed reservoir eliminates another problem suffered by many hydraulic systems: water ingression. This addresses another misconception about waterbased system: waterbased system not sealed from the atmosphere must be closed monitored to ensure that the additive concentration stays within than tolerance. That is because water evaporates from the reservoir more readily than the additive does. Consequently， water evaporation cause the additive concentration to increase. When new fluid is added to a system， samples of the existing fluid must be taken to determine the concentration of additive in solution. These results then reveal the ratio of additive to fluid that must be added so that fluid concentration is correct. With a system that seals fluid from the atmosphere, the evaporation problem is virtually eliminated. Fluid that escapes by leakage is a solution containing water and additive. Therefore， the quantity of fluid in the system changes， but concentration does not. System fluid is replenished simply by adding a premixed solution of water and additive to the reservoir.