液壓挖掘機(jī)的半自動(dòng)控制系統(tǒng)外文翻譯-液壓系統(tǒng)

1、Semi-automatic control system for hydraulic shovelAbstractA semi-automatic control system for a hydraulic shovel has been developed. Using this system, unskilled operators can operate a hydraulic shovel easily and accurately. A mathematical control model of a hydraulic shovel with a controller was c

2、onstructed and a control algorithm was developed by simulation. This algorithm was applied to a hydraulic shovel and its effectiveness was evaluated. High control accuracy and high-stability performance were achieved by feedback plusfeedforward control, nonlinear compensation, state feedback and gai

3、n scheduling according to the attitude. Keywords: Construction machinery; Hydraulic shovel; Feedforward; State feedback; Operation1. IntroductionA hydraulic shovel is a construction machinery that can be regarded as a large articulated robot.Digging and loading operations using this machine require

4、a high level of skill, and cause considerable fatigue even in skilled operators. On the other hand, operators grow older, and the number of skilled operators has thus decreased. The situation calls forhydraulic shovels, which can be operated easily by any person w15x. The reasons why hydraulic shove

5、l requires a high level of skill are as follows.1. More than two levers must be operated simultaneously and adjusted well in such operations.2. The direction of lever operations is different from that of a shovels attachment movement.For example, in level crowding by a hydraulicshovel, we must opera

6、te three levers arm, boom,bucket. simultaneously to move the top of a bucketalong a level surface Fig. 1. In this case, the lever operation indicates the direction of the actuator, but this direction differs from the working direction. If an operator use only one lever and other freedoms are operate

7、d automatically, the operation becomes very easily. We call this system a semi-automatic control system.When we develop this semi-automatic control system, these two technical problems must be solved.1. We must use ordinary control valves for automatic control.2. We must compensate dynamic character

8、istics of a hydraulic shovel to improve the precision of control.Fig. 1. Level crowding of an excavator and frame model of anexcavator. We have developed a control algorithm to solve these technical problems and confirm the effect of this control algorithm by experiments with actual hydraulic shovel

9、s. Using this control algorithm, we have completed a semi-automatic control system for hydraulic shovels. We then report these items.2. Hydraulic shovel modelTo study control algorithms, we have to analyzenumerical models of a hydraulic shovel. The hydraulic shovel, whose boom, arm, and bucket joint

10、s are hydraulically driven, is modeled as shown in Fig.2. The details of the model are described in thefollowing. Fig. 2. Model of hydraulic shovel.2.1. Dynamic model 6Supposing that each attachment is a solid body, from Lagranges equations of motion, the followingexpressions are obtained:其中 K sm 1

11、g; and gsgravitational acceleration. 3 3 g 3i is the joint angle, i is the supply torque, li is the attachment length, lgi is the distance between g ithe fulcrum and the center of gravity, mi is the mass of the attachment, Ii is the moment of inertia around (the center of gravity subscripts is13; me

12、an boom arm, and bucket, respectively.)2.2. Hydraulic modelEach joint is driven by a hydraulic cylinder whose flow is controlled by a spool valve, as shown in Fig.3. We can assume the following:1. The open area of a valve is proportional to the spool displacement.2. There is no oil leak.3. No pressu

13、re drop occurs when oil flows through piping.4. The effective sectional area of the cylinder is the same on both the head and the rod sides.In this problem, for each joint, we have thefollowing equation from the pressure flow characteristics of the cylinder:when,where, Ai seffective cross-sectional

14、area of cylinder; hi scylinder length; Xi sspool displacement;Psi ssupply pressure; Pi scylinder head-side pressure; Pi scylinder rod-side pressure; Vi soil volume in the cylinder and piping; Bi sspool width; soil density; Ksbulk modulus of oil; and csflow coefficient.2.3. Link relationsIn the model

15、 shown in Fig. 1, the relation between the cylinder length change rate and the attachment rotational angular velocity is given as follows:(1)leg(2). arm(3). bucket當(dāng) 時(shí)，F(xiàn)ig. 3. Model of hydraulic cylinder and valve.2.4. Torque relationsFrom the link relations of Section 2.3, the supply torque t is giv

16、en as follows, taking cylinder friction I into consideration:Where, Cci is the viscous friction coefficient and Fi is kinetic frictional force of a cylinder.2.5. Response characteristics of the spoolSpool action has a great effect on control characteristics.Thus, we are assuming that the spool has t

17、he following first-order lag against the referenceinput.Where, XX is the reference input of spool displacement and T is a time constant.3. Angle control systemAs shown in Fig. 4, the angle u is basically controlled to follow the reference angle u by position feedback. In order to obtain more accurat

18、e control, nonlinear compensation and state feedback are added to the position feedback. We will discuss details of these algorithms as follows.Fig. 4. Block diagram of control system3.1. Nonlinear compensationIn the ordinary automatic control systems, new control devices such as servo valves are us

19、ed. In oursemi-automatic system, in order to realize the coexistence of manual and automatic operations, we must use the main control valves, which are used in manual operation. In these valves, the relation between spool displacement and open area is nonlinear. Then, in automatic operation, using t

20、his relation, the spool displacement is inversely calculated from therequired open area, and the nonlinearity is compensatedFig. 5. Nonlinear compensation.3.2. State feedbackBased on the model discussed in Section 2, if the dynamic characteristics for boom angle control are linearized in the vicinit

21、y of a certain standard conditionspool displacement X , cylinder differential 10 pressure P , and boom angle u ., the closed-loop transfer function can be expressed bywhere, K is position feedback gain; This system has a comparatively small coefficient , so the response is oscillatory. For instance,

22、 if in our large SK-16 hydraulic shovel, X10 is 0, the coefficients are given as a s=10y2 , 10 10 . Addingthe acceleration feedback of gain Ka , to this the upper loop in Fig. a4., the closed loop transfer function is given asAdding this factor, the coefficient of s2 becomes larger, thus, the system

23、 becomes stable. In this way,acceleration feedback is effective in improving the response characteristics. However, it is generally difficult to detect acceleration accurately. To overcome this difficulty, cylinder force feedback was applied instead of acceleration feedback the lower loop in Fig. 4.

24、 In this case, cylinder force is calculated from detected cylinder pressure and filtered in its lower-frequency portion7.8. This is called pressure feedback.4. Servo control system When one joint is manually operated and another joint is controlled automatically to follow the manual operation, a ser

25、vo control system must be required. For example, as shown in Fig. 6, in the level crowding control, the boom is controlled to keep the arm and height Z (calculated from 81 and 82 ) tor. In order to obtain more accurate control, the following control actions are introduced.4.1. Feedforward controlCal

26、culating Z from Fig. 1, we obtainDifferentiating both sides of Eq.(8). with respect to time, we have the following relation,The first term of the right-hand side can be taken as the expression (feedback portion) to convert Z to, and the second term of the right-hand side is the expression (feedforwa

27、rd portion)to calculate howmuch u should be changed when u is changed manually.Actually, u is determined using the difference value of Du . To optimize the feedforward rate, feedforward gain K is tunned. ff There may be a method to detect and use the arm operating-lever condition iangle. instead of

28、arm angular velocity, since the arm is driven at an angularvelocity nearly proportional to this lever condition.4.2. Adaptie gain scheduling according to the attitudeIn articulated machines like hydraulic shovels,dynamic characteristics are greatly susceptible to the attitude. Therefore, it is diffi

29、cult to control the machine stably at all attitudes with constant gain. To solve this problem, the adaptive gain scheduling according to the attitude is multiplied in the feedback loop Fig. 6. As shown in Fig. 7, the adaptive gain (KZ or Ku). is characterized as a function of two variables, and Z. m

30、eans how the arm is extended, and Z means the height of the bucket.5. Simulation resultsThe level crowding control was simulated by applying the control algorithm described in Section 4 to the hydraulic shovel model discussed in Section 2. In the simulation, our large SK-16 hydraulic shovel was empl

31、oyed. Fig. 8 shows one of the results. Fiveseconds after the control started, load disturbanceFig. 6. Block diagram of control system (Z).Fig. 7. Gain scheduling according to the attitude.was applied stepwise. Fig. 9 shows the use of feedforward control can reduce control error.6. Semi-automatic con

32、trol systemBased on the simulation, a semi-automatic control system was manufactured for trial, and applied to the SK-16 shovel. Performance was then ascertained by field tests. This section will discuss the configuration and functions of the control system.6.1. ConfigurationAs illustrated in Fig. 1

33、0, the control system consistsof a controller, sensors, manmachine interface,and hydraulic control system. The controller is based on a 16-bit microcomputer which receives angle input signals of the boom, arm, and bucket from the sensor; determines the condition of each control lever; selects contro

34、l modes andcalculates actuating variables; and outputs the results from the amplifier as electrical signals. The hy-draulic control system generates hydraulic pressureproportional Fig. 8. Simulation result of level crowding.to the electrical signals from the electromagnetic proportional-reducing val

35、ve, positions the spool of the main control valve, and controls the flow rate to the hydraulic cylinder. In order to realize high-speed, high-accuracy control, a numeric data processor is employed for theFig. 9. Effect of feedforward control on control error of Z.Fig. 10. Schema of control system.co

36、ntroller, and a high-resolution magnetic encoder is used for the sensor. In addition to these, a pressure transducer is installed in each cylinder to achieve pressure feedback. The measured data are stored up to the memory, and can be taken out from the communication port.6.2. Control functionsThis

37、control system has three control modes,which are automatically switched in accordance with lever operation and selector switches. These functions are the following(1). Level crowding mode: during the manual arm pushing operation with the level crowding switch,the system automatically controls the bo

38、om and holds the arm end movement level. In this case, the reference position is the height of the arm end from the ground when the arm lever began to be operated. Operation of the boom lever can interrupt automatic control temporarily, because priority is given to manual operation.(2) Horizontal bu

39、cket lifting mode: during the manual boom raising operation with the horizontal bucket lifting switch, the system automatically controls the bucket. Keeping the bucket angle equal to that at the beginning of operation prevents material spillage from the bucket.(3) Manual operation mode: when neither

40、 the level crowding switch nor the horizontal bucket lifting switch are selected, the boom, arm, and bucket are controlled by manual operation only. The program realizing these functions is primarily written in C language, and has well-structured module to improve maintainability.7. Results and anal

41、ysis of field testWe put the field test with the system. We confirmed that the system worked correctly and the effects of the control algorithm described in Chaps. 3 and 4 were ascertained as follows.7.1. Automatic control tests of indiidual attachmentsFor each attachment of the boom, arm, and bucke

42、t, the reference angle was changed 58 stepwise from the initial value, and the responses were measured; thus, the effects of the control algorithm described in Chap. 3 were ascertained.7.1.1. Effect of nonlinear compensationFig. 11. Effect of nonlinear compensation on boom angle.Because dead zones e

43、xist in the electro-hydraulic systems, steady-state error remains when simple position feedback without compensation is applied in the figure. Addition of nonlinear compensation in the figure. can reduce this error.7.1.2. Effect of state feedback controlFor the arm and bucket, stable response can be

44、 obtained by position feedback only, but adding acceleration or pressure feedback can improve fast-response capability. As regards the boom, with only the position feedback, the response becomes oscillatory. Adding acceleration or pressure feedback made the response stable without impairing fast-res

45、ponse capability. As an example, Fig. 12 shows the test results when pressure feedback compensation was applied during boom lowering.7.2. Leel crowding control test Control tests were conducted under various controland operating conditions to observe the controlFig. 12. Effect of pressure feedback c

46、ontrol on boom angle.Fig. 13. Effect of feedforward control on control error of Z.characteristics, and at the same time to determine the optimal control parameters such as the control gains shown in Fig. 6.7.2.1. Effects of feedforward controlIn the case of position feedback only, increasing gain K

47、to decrease error DZ causes oscillation due p to the time delay in the system, as shown by AOFFB in Fig. 13. That is, K cannot be increased. Applying the feedforward of the arm lever value described in Section 4.1 can decrease error without increasing K as shown by AONB in the figure. p7.2.2. Effect

48、s of compensation in attitudeLevel crowding is apt to become oscillatory at the raised position or when crowding is almost completed. This oscillation can be prevented by changing gain K according to the attitude, as has been pdiscussed in Section 4.2. The effect is shown in Fig.14. This shows the r

49、esult when the level crowding was done at around 2 m above ground. Compared tothe case without the compensation, denoted by OFF in the figure, the ON case with the compensation provides stable response.Fig. 14. Effect of adaptive gain control on control error of Z.7.2.3. Effects of control interalTh

50、e effects of control interval on control performance were investigated. The results are:1. when the control interval is set to more than 100 ms, oscillation becomes greater at attitudes with large moments of inertia; and2. when the control interval is less than 50 ms, control performance cannot be i

51、mproved so much. Consequently, taking calculation accuracy into account, the control interval of 50 ms was selected for this control system.7.2.4. Effects of loadA shovel with this control system carried out actual digging to investigate the effects of loading.No significant difference was found in

52、control accuracy from that at no load.8. ConclusionsThis paper has shown that combining state feedback and feedforward controls makes it possible to accurately control the hydraulic shovel, and also showed that nonlinear compensation makes it possible to use ordinary control valves for automatic con

53、trols. The use of these control techniques allows even unskilled operators to operate hydraulic shovels easily and accurately. We will apply these control techniques to other construction machinery such as crawler cranes, and improve the conventional construction machinery to the machines which can

54、be operated easily by anyone.References1 J. Chiba, T. Takeda, Automatic control in construction machines, Journal of SICE 21 8 1982 4046.2 H. Nakamura, A. Matsuzaki, Automation in construction machinery, Hitachi Review 57 3 1975 5562.3 T. Nakano et al., Development of large hydraulic excavator,. Mit

55、subishi Heavy Industries Technical Review 22 2 1985 4251.4 T. Morita, Y. Sakawa, Modeling and control of power shovel, Transactions of SICE 22 1 1986 6975.5 H. Araya et al., Automatic control system for hydraulic excavator, R&D Kobe Steel Engineering Reports 37 2 1987 7478.6 P.K. Vaha, M.J. Skibniew

56、ski, Dynamic model of excavator, Journal of Aerospace Engineering 6 2 1990 April.7 H. Hanafusa, Design of electro-hydraulic servo system for articulated robot, Journal of the Japan Hydraulics and Pneumatics Society 13 7 1982 18.8 H.B. Kuntze et al., On the model-based control of a hydraulic large ra

57、nge robot, IFAC Robot Control 1991 207212.液壓挖掘機(jī)的半自動(dòng)控制系統(tǒng) 摘要:開發(fā)出了一種應(yīng)用于液壓挖掘機(jī)的半自動(dòng)控制系統(tǒng)。采用該系統(tǒng)，即使是不熟練的操作者也能容易和精確地操控液壓挖掘機(jī)。構(gòu)造出了具有控制器的液壓挖掘機(jī)的精確數(shù)學(xué)控制模型，同時(shí)通過模擬實(shí)驗(yàn)研發(fā)出了其控制算法，并將其應(yīng)用在液壓挖掘機(jī)上，由此可以估算出它的工作效率。依照此法，可通過正反響及前饋控制、非線性補(bǔ)償、狀態(tài)反響和增益調(diào)度等各種手段獲得較高的控制精度和穩(wěn)定性能。關(guān)鍵詞：施工機(jī)械；液壓挖掘機(jī)；前饋；狀態(tài)反響；操作1引言液壓挖掘機(jī)，被稱為大型鉸接式機(jī)器人，是一種施工機(jī)械。采用這種機(jī)器進(jìn)行挖掘

58、和裝載操作，要求司機(jī)要具備高水平的操作技能，即便是熟練的司機(jī)也會(huì)產(chǎn)生相當(dāng)大的疲勞。另一方面，隨著操作者年齡增大，熟練司機(jī)的數(shù)量因而也將會(huì)減少。開發(fā)出一種讓任何人都能容易操控的液壓挖掘機(jī)就非常必要了1-5。液壓挖掘機(jī)之所以要求較高的操作技能，其理由如下。1.液壓挖掘機(jī)的操作，至少有兩個(gè)操作手柄必須同時(shí)操作并且要協(xié)調(diào)好。2.操作手柄的動(dòng)作方向與其所控的臂桿組件的運(yùn)動(dòng)方向不同。例如，液壓挖掘機(jī)的反鏟水平動(dòng)作，必須同時(shí)操控三個(gè)操作手柄動(dòng)臂，斗柄，鏟斗使鏟斗的頂部沿著水平面圖1運(yùn)動(dòng)。在這種情況下，操作手柄的操作說明了執(zhí)行元件的動(dòng)作方向，但是這種方向與工作方向不同。如果司機(jī)只要操控一個(gè)操作桿，而其它自由桿

59、臂自動(dòng)的隨動(dòng)動(dòng)作，操作就變得非常簡單。這就是所謂的半自動(dòng)控制系統(tǒng)。開發(fā)這種半自動(dòng)控制系統(tǒng)，必須解決以下兩個(gè)技術(shù)難題。1. 自動(dòng)控制系統(tǒng)必須采用普通的控制閥。2. 液壓挖掘機(jī)必須補(bǔ)償其動(dòng)態(tài)特性以提高其控制精度?，F(xiàn)已經(jīng)研發(fā)一種控制算法系統(tǒng)來解決這些技術(shù)問題，通過在實(shí)際的液壓挖掘機(jī)上試驗(yàn)證實(shí)了該控制算法的作用。而且我們已采用這種控制算法，設(shè)計(jì)出了液壓挖掘機(jī)的半自動(dòng)控制系統(tǒng)。具體闡述如下。2液壓挖掘機(jī)的模型為了研究液壓挖掘機(jī)的控制算法,必須分析液壓挖掘機(jī)的數(shù)學(xué)模型。液壓挖掘機(jī)的動(dòng)臂、斗柄、鏟斗都是由液壓力驅(qū)動(dòng)，其模型如圖2所示。模型的具體描述如下。2.1 動(dòng)態(tài)模型6 假定每一臂桿組件都是剛體，由拉格朗

60、日運(yùn)動(dòng)方程可得以下表達(dá)式： 其中 g是重力加速度；i鉸接點(diǎn)角度；i是提供的扭矩；li組件的長度；lgi轉(zhuǎn)軸中心到重心之距；mi組件的質(zhì)量；Ii是重心處的轉(zhuǎn)動(dòng)慣量(下標(biāo)i=1-3;依次表示動(dòng)臂，斗柄，鏟斗)。2.2 挖掘機(jī)模型每一臂桿組件都是由液壓缸驅(qū)動(dòng)，液壓缸的流量是滑閥控制的，如圖3所示?？勺魅缦录僭O(shè)：1.液壓閥的開度與閥芯的位移成比例。2.系統(tǒng)無液壓油泄漏。3.液壓油流經(jīng)液壓管道時(shí)無壓力損失。4.液壓缸的頂部與桿的兩側(cè)同樣都是有效區(qū)域。在這個(gè)問題上，對于每一臂桿組件，從液壓缸的壓力流量特性可得出以下方程：當(dāng)時(shí)；其中，Ai是液壓缸的有效橫截面積;hi是液壓缸的長度;Xi是滑芯的位置；Psi是