電液比例控制的雙缸液壓升降機外文翻譯

1、electro-hydraulic proportional control of twin-cylinder hydraulic elevatorsabstractthe large size of the cab of an electro-hydraulic elevator necessitates the arrangement of two cylinders located symmetrically on both sides of the cab. this paper reports the design of an electro hydraulic system whi

2、ch consists of three flow-control proportional valves. speed regulation of the cab and synchronization control of the two cylinders are also presented. a pseudo-derivative feedback (pdf) controller is applied to obtain a velocity pattern of the cab that proves to be close to the given one. the non-s

3、ynchronous error of the two cylinders is kept within 2mm with a constrained step proportional-derivative (pd) controller. a solenoid actuated non-return valve, i.e. a hydraulic lock, is also developed to prevent cab sinking and allow easy inverse-fluid flow. keywords: hydraulic elevator; velocity tr

4、acking; synchronization; hydraulic lock1. introductionthe modern hydraulic elevator is currently an excellent and low-cost solution to the problem of vertical transportation in low or mid-rise buildings, and in those applications requiring very large capacities, slow speeds and short travel distance

5、s. these include scenic elevators in superstores or historical buildings, stage elevators, ship elevators and elevators for the disabled, etc. in most cases, hydraulic elevators can be adapted to architectural design requirements without compromising energy saving and efficiency requirements.in addi

6、tion, the use of fire-resistant fluid makes the hydraulic elevator a suitable choice when elevators have to operate near hazards such as furnaces or open fires.hydraulic drives are used preferably in elevators where large payloads need to be carried, such as for car elevators or marine elevators. in

7、 heavy load cases, an elevator cab usually has directly acting or side-acting hydraulic cylinders. the direct-acting arrangement involves a deep pit, substantial risk of corrosion of the buried cylinders and the difficulty of replacing failed cylinder parts. thus, in many situations the side-acting

8、hydraulic cylinder is preferred, despite the fact that it probably increases rail wear due to insufficient cab stiffness. in the extreme conditions, i.e. when large cab sizes and uneven payloads are involved, the cabs flexibility may even cause the guide shoes to stick to the rails, which is very da

9、ngerous. therefore, in such cases, a feasible solution is to arrange two directly acting cylinders symmetrically on each side of the cab, as shown in fig. 1. it should be noted that smooth running cannot be ignored because people may be part of the payloads that accompany the freight. the major issu

10、e when designing a control system is to ensure the synchronous motion of the two cylinders.the error due to the non-synchronous motion of the two cylinders caused, by an uneven load under equal pressure-control, which is generally used for elevator control with multiple hydraulic cylinders, is schem

11、atically shown in fig. 2. it is obvious from fig. 2 that equal pressure-control is not suitable for a synchronized hydraulic elevator. when the payload is located on the right side of the cab, the left cylinder, with a lighter load, will move upward faster than the right one. the speed disparity bet

12、ween the two cylinders will not cease until the reaction forces actuated by the rails on both the lower left and upper right guide shoes attached on the cab are balanced by the hydraulic force difference. the non-synchronisation of the two cylinders can only be reduced by flow control, i.e. by ensur

13、ing that the fluid flows into the two cylinders per unit time are the same.this paper presents an electro-hydraulic system for the control of an elevator with twin cylinders that are located on each side of the elevator cab. the designed system consists of three flow-control proportional valves. a p

14、df controller is applied to velocity control whereas a constrained step pd controller guarantees the minimum non-synchronous error between the motion of two cylinders. the design of a newly developed solenoid-actuated non-return valve i.e. a hydraulic lock is also presented in this paper. in this pr

15、oject, experiments are conducted with a normal size passenger cab instead of building a new large-size cab due to cost limitations. in order to achieve the flexible condition of a larger cab, the distance between the rails and their corresponding guide shoes in the side direction is extended so that

16、 the cab has no constraints in this direction. meanwhile, in the forward and backward direction, the cab is constrained by the rails just like a general passenger elevator. the synchronous motion control of the two cylinders in such an assembly is analogous to and even more difficult than that of a

17、larger cab with normal constraints.2. electro-hydraulic control system design there are two different fluid power systems generally used in hydraulic elevators. the flow-restriction speed-regulation system and variable-delivery speed-regulation system. in the former system, the pump runs at a consta

18、nt speed and the valve regulates the speed of the cylinder in both the upward and downward directions. in the latter case, the cab is operated by varying the speed of the pump, which is driven by a speed-controlled induction motor.the hydraulic system employed in this twin-cylinder elevator works ac

19、cording to the flow-restricted speed regulation principle, in which the fluid flow into and out of the two cylinders is controlled by appropriate valve settings, with the output of the pump kept at a fixed level. in this system, there are three flow-control proportional valves -5-7 as shown in fig.

20、3. flow-control proportional valves act as throttle valves that restrict the fluid flow to a single direction. they can give a smooth stepless variation of flow control from near zero up to the valves maximum capacity. the flow rate through valve 5 remains almost invariable because a combination hyd

21、rostat maintains a constant level of pressure difference across the proportional valve, irrespective of system or load pressure changes. in the case of throttle valves, 6 and 7 in fig. 3, their fluid flows will change with system or load pressure changes. valve 5, here called velocity valve, control

22、s the velocity of the elevator. the upward motion of the cab is driven by fixed-displacement piston pump 1. when motor 2 starts to work, the solenoid-actuated twin-position relief- valve 4 unloads the output from pump 1 to tank 20 and the opening of velocity valve 5 is kept at its maximum value. the

23、 solenoid of valve 4 is automatically energised, shifting the valve to its closed position and thus setting a relief pressure for the system. at this stage, the regulation of the cab velocity is achieved by adjusting the electric current through the coil of valve 5. at the closing of valve 5, all th

24、e fluid flows into cylinders 12 and 13 and thus the cab velocity reaches its maximum value. the downward motion is caused by the dead load of the cab and its payloads. when the control panel receives a downward call, solenoid-actuated non-return valves 10 and 11 open and the cab velocity is controll

25、ed by valve 5. the larger the opening of valve 5, the higher the cab velocity. velocity valve 5 directs pressurised fluid from the cylinders to tank 20 to lower the cab. check valve 3 prevents pressurised fluid from driving the pump in its reverse working direction. synchronous motion of cylinders 1

26、2 and 13 depends on the combined adjustment of the flow control valves 6 and 7. the steady-state flow through a throttle valve can be represented as where q denotes the flow, xv the spool displacement, p the pressure drop across the valve and k0 is a constant. if the pressure drop p remains constant

27、, q is in direct proportion to xv, which is in direct proportion to the electric current through the solenoid coil. the flow variations that are caused by the pressure drop variations can thus be compensated for by changing xv. as mentioned above, fluid flows through the flow control proportional va

28、lves in only one direction. valve groups 8 and 9, each of which consists of four check valves, are used to ensure that valves 6 and 7 work in their normal directions. solenoid-actuated non-return valves 10 and 11 are specially designed to prevent the cab from sinking, which is normally caused by the

29、 leakage of the hydraulic components when the cab stops at a landing. the working principle of the solenoid-actuated non-return valve will be further expanded later in this paper. they lock the cab when the pump stops and thus can be called hydraulic locks here. only when their solenoids are energiz

30、ed will the cab move downward. in case of power breaks or other hydraulic element failures, emergency valve 14 lowers the cab at a lower speed.3. electro-hydraulic proportional controla suitable velocity curve, preset according to design specifications such as maximum acceleration, maximum rate of a

31、cceleration change and maximum running velocity, etc., is usually used to describe the running pattern of an elevator. if the cab velocity follows the given curve well, good riding comfort is assured. open-loop control cannot achieve sufficient tracking accuracy because of variations in payloads, fl

32、uid volume in cylinders and fluid viscosity. therefore, speed feedback is needed to attenuate the influence of the various disturbances on the performance of an elevator. furthermore, without closed-loop control, the non-synchronous motion of the two cylinders is inevitable due to the differences in

33、 payload, friction and hydraulic flow resistance between the two cylinders. consequently, two closed loops are required to attain speed regulation and synchronization control at the same time. the control block diagram of the whole system is shown in fig. 4, which represents the elevator motion in u

34、pward direction. a similar block diagram can easily be deduced for downward motion. the cab velocity is measured by an encoder. the translational movement of the cab is transferred to rotation of the rotor of an encoder by a pulley. a two-element synchro-system is used to measure the relative angles

35、 between the rotors of control transmitter cx and control transformer ct. thus, the relative angle measured by the synchro-system is proportional to the height error between the two cylinders. as discussed above, the cab velocity is only determined by velocity valve 5 in fig. 3, provided the synchro

36、nization valves 6 and 7 work in strict proportion to valve 5. in turn, under the same condition, the adjustment of valves 6 and 7 will not influence the cabs velocity. hence, speed regulation and synchronization control can be realized separately, i.e. velocity controller 1 and synchronization contr

37、oller 2 can work independently. a pseudo-derivative feedback (pdf) controller, i.e. controller 1 as shown in fig. 4 is applied to suppress the adverse effects of internal parameter changes such as fluid volume in cylinders and external disturbances such as payload and fluid-temperature variations. a

38、s shown in fig. 5, the pdf controller is easy to realize and insensitive to system-parameter changes and external disturbances . when m1(t) is small enough, the saturated non-linearity can be simplified as working in its linear segment, then the pdf controller parameters can easily be obtained.suppo

39、se the system can be described bythen the three controller parameters are:where is 7.5167/ts, ts the settling time and kh the constant for adjusting the output amplitude of the controller. in situ tuning of controller parameters is required to ensure the optimal performance. figs. 6 and 7 show the t

40、racking performance of the cabs velocity following the given velocity curve with a full payload and with no payload, respectively. the difference between the desired velocity pattern and the actual velocity pattern is mainly due to the non-linear characteristics of the electro-hydraulic proportional

41、 valve 5. however, the whole velocity pattern is very close to the designed pattern, and thus satisfactory riding comfort can still be guaranteed. a constrained step proportional-derivative (pd) controller, i.e. controller 2 in fig. 2, is used to obtain synchronous motion of the two cylinders. the i

42、dea behind this pd controller is similar to the steering of a boat. when rowing a boat to keep it along a straight line, the rower exerts force on oars each time according to how far and how fast the boat is getting away from the line. because of the rowers unavoidably delayed response, the disparit

43、y between the boats real route and the given route cannot be kept small. an effective alternative method involves the rower applying a fraction of the estimated forces each time the oars are operated. the boat will thus approach the given route step by step till the route error approaches an accepta

44、ble value. cylinder 12 is taken as the reference cylinder, whose movement has to be followed by cylinder 13, say, the fig.8. non-synchronous height error curve under void payload. fig.9. non-synchronous height error curve under one ton unevenly placed payloadfollowing cylinder. the backlash of valve

45、s 6 and 7 is similar to the rowers delayed response to the boats route error. in each adjustment period of controller 2, its real output is only a fraction of the required value calculated by the pd controller. that is, the large error is reduced in each sampling period at a constrained step until a

46、n acceptable height error is reached. this control scheme has proven to be effective in keeping the non-synchronous error within 2mm, as shown in figs. 8 and 9. it should be noted that if the initial non-synchronous error during a sampling period is rather large, it would take some time to reach an

47、acceptable level of error. if the non-synchronous error at the end of one elevator run can be retained at the beginning error of the next run, this process can be avoided and the non-synchronous error will remain at small values throughout all the runs. to attain this goal, a sink-proof device is ne

48、eded since the different leakage rates of the two cylinders will directly increase the initial error of an elevator. 4. conclusion an electro-hydraulic control system with three flow control proportional valves has been proposed for the control of elevator velocity and non-synchronous error between

49、the cylinders of a twin cylinder hydraulic elevator. a pseudo-derivative feedback control scheme has shown to be an appropriate technique to achieve a desired velocity pattern. furthermore, this system guarantees low non-synchronous error by applying a constrained step pd controller. the test result

50、s show that the non-synchronous error can be kept within 2 mm. a certain discrepancy between the desired pattern and the actual velocity pattern is due mainly to the hysteresis of the electro-hydraulic proportional valves. a new solenoid actuated non-return valve has been designed, fabricated and te

51、sted, and proves to be a good hydraulic device for preventing cab sinking. 電液比例控制的雙缸液壓升降機 摘要:一個電液控制的液壓升降機的大型機車需要在這個機車的兩邊安裝兩個對稱的油缸。摘要報道了一種電液系統(tǒng)的設計主要包括三個流體控制比例閥。機車的速度調節(jié)和兩油缸的同步控制也是呈遞的。一個假微分反饋(pdf)控制器以獲得一個機車的速度模式來證實和給定的這個接近。兩油缸的非同步性的誤差范圍在2之內由于有比例控制器來拘泥每一步。一個電磁鐵操縱的單向閥,即液壓鎖,被發(fā)明以防止機車下沉并允許反方向流體容易流動。關鍵詞:液壓升降機

52、;速度跟蹤;同步化;液壓鎖1、引言現(xiàn)代液壓升降機目前有一個很優(yōu)秀的和低成本的方法來解決垂直運輸在低或中高層建筑物的這一問題,在這些應用需要非常大的容量,緩慢的速度和短的行進距離。這些包括風景名優(yōu)美的在超市連鎖店或歷史建筑電梯、舞臺升降機、船電梯和為殘疾人用的電梯等。在大多數情況下,液壓升降機能適應建筑設計要求的前提下實現(xiàn)節(jié)能增效要求。另外,耐高溫流體的應用使液壓電梯有一個適當的選擇當電梯不得不操縱在附近有的危險場合時如熔爐或明火。液壓傳動最好應用于需要進行大負荷運輸的電液升降機,比如車輛升降機或船舶升降機。在重負荷情況下,升降機的駕駛室通常有直接運行和輔助液壓缸。這直接的布置涉及一個大的凹陷,

53、埋藏油缸腐蝕的大量危險和更換缸體出現(xiàn)故障的零件困難。因此,在很多情形下輔助液壓缸是首選,盡管事實是它可能增加軌道的磨損由于機車剛度不足。在極端的條件下,即當投入大型機車尺寸和不均勻載荷時,機車的彈性甚至導致滑塊粘住兩橋底板的兩個邊,這是很危險的。因此,在這種情況下,一種可行的解決方案是直接安排兩個對稱的油缸在機車的每一邊如圖1所示。應該指出的是,運轉平穩(wěn)不容忽視,因為人們可能是部分有效載荷伴隨著貨運。在設計控制系統(tǒng)時的主要問題是確保兩油缸的同步運動。這個錯誤由于兩油缸運動的非同步性造成，被相等壓力控制下的不均勻荷載,這通常用于電梯的控制與多個液壓缸,如圖2所示。很明顯,同等的壓力控制不適合一個

54、同步的液壓電梯。當載荷位于機車的右側,左邊的油缸有輕負荷,會比右面的那個向上運動的速度快。兩油缸速度的不一致將不會停止,直到反作用力驅動通過欄桿上兩個比較低的左邊和右上方的導塊附著于機車來平衡液壓力的差異。兩油缸的非同步性只能用流量控制降低,即確保流體流入兩油缸的單位時間是相同的。 圖1 兩個油缸安排一起運動圖2 相同壓力控制:不均勻放置靜載荷導致非同步性本文提出了一種電液控制電梯有兩缸,位于升降機駕駛室的兩邊。該系統(tǒng)包括三個流體控制比例閥。一個pdf控制器應用于速率控制然而一個約束一步的pd控制器可保證兩油缸運動不同步的最小誤差。一種新開發(fā)的設計電磁單向閥即液壓鎖也進行了介紹。在這個項目中,

55、實驗被引導用標準性機車代替大型建筑機車,由于費用的局限性。為了實現(xiàn)大型機車的靈活條件,軌道之間的距離與相應的導塊側向延伸,使機車在這個方向沒有約束。與此同時,在前方向和后方向,機車被軌道制約,就像一個通用的乘客電梯。同步運動控制的兩油缸在這里裝配,就好比是比大的駕駛室有正常的約束更困難。2、電液控制系統(tǒng)設計有兩種比較難的液壓傳動系統(tǒng)通常應用于液壓升降機中。節(jié)流調速系統(tǒng)和容積調速系統(tǒng)。 在第一個系統(tǒng)中,泵運行以一個恒定的速度并且由閥門來控制和調節(jié)油缸上升和下降的速度。在后一種情況下,機車被變速泵操縱,這由速度控制的異步電機驅動。 圖3 雙缸液壓升降機原理圖液壓系統(tǒng)應用兩缸升降機的動作,根據節(jié)流調

56、速,流體流入和流出兩缸的多少是通過適當的閥門的設置來控制,與輸出的泵保持在一個固定的水平。在這個系統(tǒng)中,有三種流體控制比例閥-5-7,如圖3所示。流量控制比例閥就像節(jié)流閥,限制流體朝單一方向流動。他們能給一個平滑無級變化的流量控制從近零到閥門的最大容量。通過閥門5的流量恒定不變,因為水壓調節(jié)器的組合能保持恒定壓差穿過流量閥,不管系統(tǒng)或負載壓力的變化。節(jié)流閥門6和7的情況下,如圖3所示。他們流量將會改變如果系統(tǒng)或負載壓力發(fā)生變化。閥5,這里被稱為調速閥可控制升降機的速度。機車的向上的運動是由定量柱塞泵1來控制。 當電機2開始工作時,二位電磁換向閥解除閥4對輸出泵1輸出的卸荷，到油箱20和打開的速

57、度保持在閥門5它的最大價值。閥4的電磁閥的自動供給能量,關閉閥門,并且安裝一個減壓系統(tǒng)。在這一階段,機車的速度調節(jié)的校準的完成是通過調節(jié)通過閥5線圈的電流。在關閉的閥5時,所有的流體流動進入油缸12和13，并且機車的速度達到最大值。下行運動是由機車的靜載和它的有效載荷所引起。當控制面板收到一個向下的動作的信號,電磁控制單向閥10和11開啟，機車的速度控制是通過閥門5來實現(xiàn)。閥5開口越大，機車獲得的速度就越快。閥門5引導高壓流體從油缸到油箱20再到較低的機車。單向閥3阻止高壓流體反向流回。同步運動的油缸12和13取決于流量控制閥6和7的組合調整。通過節(jié)流閥調節(jié)穩(wěn)態(tài)流動可以用下式表示為上式的q代表流量,xv 活塞桿的位移、p通過閥門的壓降和k0是c常數。如果壓力降的p不變,流量和活塞桿的位移成正比,這也正比通過電磁閥線圈的電流。流量變化所引起的壓降的變化也能因此得到補償,通過改變活塞桿的位移。如上所述,流體流過的流量控制比例閥只有一個方向。閥組8和9,其中的每一個都由四個單向閥,用于確保閥門6和7