【正文】 edforward control Calculating Z from Fig. 1, we obtain Differentiating both sides of Eq.(8). with respect to time, we have the following relation, The first term of the righthand side can be taken as the expression (feedback portion) to convert Z˙ to , and the second term of the righthand side is the expression (feedforward portion)to calculate howmuch u should be changed when u is changed , 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 operatinglever condition iangle. instead of arm angular velocity, since the arm is driven at an angularvelocity nearly proportional to this lever condition. . Adapti213。al The 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 bees greater at attitudes with large moments of inertia。另一方 面，隨著操作者年齡增大，熟練司機的數(shù)量因而也將會減少。這就是所謂的半自動控制系統(tǒng)。液壓挖掘機的動臂、斗柄、鏟斗都是由液壓力驅(qū)動，其模型如圖 2 所示。 。因而，假定滑閥相對參考輸入有以下的一階延遲。因此，自動控制操作中，利 用這種關(guān)系，閥芯位移可由所要求的閥的開度反推出來。于是，液壓缸力由測出的缸內(nèi)的壓力計算而濾掉其低頻部分 [7， 8]。 采用測量斗柄操作手柄的位置（如角度）取代測斗柄的角速度，因為驅(qū)動斗柄的角速度與操作手柄的位置近似成比例。控制系統(tǒng)啟動 5 秒以后，逐步加載擾動。除此之外，在每一液壓缸上安裝壓力傳感器以便獲得壓力反饋信號。保持鏟斗角度等于其剛開始舉升時角度以阻止原材料從鏟斗中泄漏。 非線性補償?shù)淖饔? 圖 11 表明動臂下降時的測 試結(jié)果。 前饋控制作用 在只有位置反饋的情況下，增大放大系數(shù) Kp，減少 △ Z 錯誤，引起系統(tǒng)不穩(wěn)定，導(dǎo)致系統(tǒng)延時，例如圖 13所示的 “關(guān) ”，也就是 Kp 不能減小。 50ms 時，其控制操作不能作如此大提高。 參考文獻(xiàn) [1] J. Chiba, T. Takeda, Automatic control in construction machines, Journal of SICE 21 8 1982 40–46. [2] H. Nakamura, A. Matsuzaki, Automation in construction machinery, Hitachi Review 57 3 1975 55–62. [3] T. Nakano et al., Development of large hydraulic excavator,. Mitsubishi Heavy Industries Technical Review 22 2 1985 42–51. [4] T. Morita, Y. Sakawa, Modeling and control of power shovel, Transactions of SICE 22 1 1986 69–75. [5] H. Araya et al., Automatic control system for hydraulic excavator, Ramp。 8 結(jié)論 本文表明狀態(tài)反饋與前饋控制組合，使精確控制液壓挖掘機成為可能。不穩(wěn)定振蕩可根據(jù)其位置改變放大系數(shù) Kp 來消除，如第 節(jié)所討論的。以動臂為例，僅只有位置反饋時，響應(yīng)趨向不穩(wěn)定。核實本文第 4 節(jié)所闡述的控制算法的作用，如下所述。 （ 1）反鏟水平動作模式：用水平反鏟切換開關(guān)，在手控斗柄推動操作中，系統(tǒng)自動的控制斗柄以及保持斗柄底部的水平運動。 結(jié)構(gòu) 圖 10 的例子中，控制系統(tǒng)由控制器、傳感器、人機接口和液壓系統(tǒng)組成。如圖 7 所示，自適應(yīng)放大系數(shù)（ KZ 或 Kθ）作為函數(shù)的兩個變量， 2 和 Z 、 2 表示斗柄的伸長量， Z 是表示鏟斗的高度。為了獲得更精確的控制引入以下控制系統(tǒng)。 X10 是 0，給出的系數(shù)a0= 10 ,a1= 10 ,a2= 10 .加上加速度反饋放大系數(shù) Ka，因而閉環(huán)（圖 4 的上環(huán)）的傳遞函數(shù)就是 加入這個因素 ,系數(shù) S 就變大，系統(tǒng)趨于穩(wěn)定。以下詳細(xì)討論其控制算法。P1i是液壓缸的頂邊壓力； P2i是液壓缸的桿邊壓力； Vi是在液壓缸和管道的油量； Bi是滑閥的寬度； γ 是油的密度； K 是油分子的黏度； c 是流量系數(shù)。 挖掘機模型 每一臂桿組件都是由液壓缸驅(qū)動，液壓缸的流量是滑閥控制的，如圖 3 所示。 現(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，通過在實際的液壓挖掘機上試驗證實了該控制算法的作用。 。構(gòu)造出了具有控制器的液壓挖掘機的精確數(shù)學(xué)控制模型，同時通過模擬實驗研發(fā)出了其控制算法，并將其應(yīng)用在液壓挖掘機上，由此可以估算出它的工作效率。 and outputs the results from the amplifier as electrical signals. The hydraulic control system generates hydraulic pressureproportional Fig. 8. Simulation result of level crowding. to the electrical signals from the electromagic proportionalreducing valve, positions the spool of the main control valve, and controls the flow rate to the hydraulic cylinder. In order to realize highspeed, highaccuracy control, a numeric data processor is employed for the Fig. 9. Effect of feedforward control on control error of Z. Fig. 10. Schema of control system. controller, and a highresolution magic 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 munication port. . Control functions This 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 boom 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 bucket 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 the level crowding switch nor the horizontal bucket lifting switch are selected, the boom, arm, and bucket are controlled by manual operation onl