【正文】 at the same time to determine the optimal control parameters ?such as the control gains shown in Fig. 6.. . Effects of feedforward control In the case of position feedback only, increasing gain K 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 can decrease error without increasing K as shown by AONB in the figure. p . Effects of pensation in attitude Level crowding is apt to bee oscillatory at the raised position or when crowding is almost pleted. This oscillation can be prevented by changing gain K according to the attitude, as has been p discussed in Section . The effect is shown in . This shows the result when the level crowding was done at around 2 m above ground. Compared tothe case without the pensation, denoted by OFF in the figure, the ON case with the pensation provides stable response. Fig. 14. Effect of adaptive gain control on control error of Z. . Effects of control inter213。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。 and 2. when the control interval is less than 50 ms, control performance cannot be improved so much. Consequently, taking calculation accuracy into account, the control interval of 50 ms was selected for this control system. . Effects of load A shovel with this control system carried out actual digging to investigate the effects of loading. No significant difference was found in control accuracy from that at no load. 8. Conclusions This paper has shown that bining state feedback and feedforward controls makes it possible to accurately control the hydraulic shovel, and also showed that nonlinear pensation makes it possible to use ordinary control valves for automatic controls. 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 be operated easily by anyone. References [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。D Kobe Steel Engineering Reports 37 2 1987 74–78. [6] . Vaha, . Skibniewski, Dynamic model of excavator, Journal of Aerospace Engineering 6 2 1990 April. [7] H. Hanafusa, Design of electrohydraulic servo system for articulated robot, Journal of the Japan Hydraulics and Pneumatics Society 13 7 1982 1–8. [8] . Kuntze et al., On the modelbased control of a hydraulic large range robot, IFAC Robot Control 1991 207–212. 液壓挖掘機的半自動控制系統(tǒng) 摘要 :開發(fā)出了一種應用于液壓挖掘機的半自動控制系統(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。構造出了具有控制器的液壓挖掘機的精確數學控制模型，同時通過模擬實驗研發(fā)出了其控制算法，并將其應用在液壓挖掘機上，由此可以估算出它的工作效率。依照此法，可通過正反饋及前饋控制、非線性補償、狀態(tài)反饋和增益調度等各種手段獲得較高的控制精度和穩(wěn)定性能。 關鍵詞：施工機械；液壓挖掘機；前饋；狀態(tài)反饋；操作 1．引言 液壓挖掘機，被稱為大型鉸接式機器人，是一種施工機械。采用這種機器進行挖掘和裝載操作，要求司機要具備高水平的操作技能，即便是熟練的司機也會產生相當大的疲勞。另一方 面，隨著操作者年齡增大，熟練司機的數量因而也將會減少。開發(fā)出一種讓任何人都能容易操控的液壓挖掘機就非常必要了 [15]。 液壓挖掘機之所以要求較高的操作技能，其理由如下。 ，至少有兩個操作手柄必須同時操作并且要協(xié)調好。 。 例如，液壓挖掘機的反鏟水平動作，必須同時操控三個操作手柄（動臂，斗柄，鏟斗）使鏟斗的頂部沿著水平面（圖 1）運動。在這種情況下，操作手柄的操作表明了執(zhí)行元件的動作方向，但是這種方向與工作方向不同。 如果司機只要操控一 個操作桿，而其它自由桿臂自動的隨動動作，操作就變得非常簡單。這就是所謂的半自動控制系統(tǒng)。 開發(fā)這種半自動控制系統(tǒng)，必須解決以下兩個技術難題。 1. 自動控制系統(tǒng)必須采用普通的控制閥。 2. 液壓挖掘機必須補償其動態(tài)特性以提高其控制精度。 現已經研發(fā)一種控制算法系統(tǒng)來解決這些技術問題，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。而且我們已采用這種控制算法，設計出了液壓挖掘機的半自動控制系統(tǒng)。具體闡述如下。 2．液壓挖掘機的模型 為了研究液壓挖掘機的控制算法 ,必須分析液壓挖掘機的數學模型。液壓挖掘機的動臂、斗柄、鏟斗都是由液壓力驅動，其模型如圖 2 所示。模型的具體描述如下。 動態(tài)模型 [6] 假定每一臂桿組件都是剛體，由拉格朗日運動方程可得以下表達式： 其中 g 是重力加速度； θi鉸接點角度； τi是提供的扭矩； li 組件的長度； lgi轉軸中心到重心之距； mi組件的質量； Ii是重心處的轉動慣量 (下標 i=13。依次表示動臂，斗柄，鏟斗 )。 挖掘機模型 每一臂桿組件都是由液壓缸驅動，液壓缸的流量是滑閥控制的，如圖 3 所示?？勺魅缦录僭O： 。 。 。 。 在這個問題上，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 時； 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是供給壓力 。P1i是液壓缸的頂邊壓力； P2i