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)-wenkub
2023-01-30 03:47:08 本頁(yè)面
【正文】 Adding this factor, the coefficient of s2 bees larger, thus, the system bees stable. In this way,acceleration feedback is effective in improving the response characteristics. However, it is generally difficult to detect acceleration accurately. To overe this difficulty, cylinder force feedback was applied instead of acceleration feedback the lower loop in Fig. 4.. In this case, cylinder force is calculated from detected cylinder pressure and filtered in its lowerfrequency portion[]. This is called pressure . Servo control system When one joint is manually operated and another joint is controlled automatically to follow the manual operation, a servo 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. . Feedforward 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。 Bi sspool width。Psi ssupply pressure。 and gsgravitational acceleration. 3 3 g 3 θi is the joint angle, τi 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 is1–3。 Hydraulic shovel。 Feedforward。 mean boom arm, and bucket, respectively.) . Hydraulic model Each 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 pressure 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 this problem, for each joint, we have thefollowing equation from the pressure flow characteristics of the cylinder: when, where, Ai seffective crosssectional area of cylinder。 Pi scylinder headside pressure。 γ soil density。e gain scheduling according to the attitude In articulated machines like hydraulic shovels,dynamic characteristics are greatly susceptible to the attitude. Therefore, it is difficult 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. means how the arm is extended, and Z means the height of the bucket. 5. Simulation results The 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 SK16 hydraulic shovel was employed.. Fig. 8 shows one of the results. Fiveseconds after the control started, load disturbance Fig. 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. Semiautomatic control system Based on the simulation, a semiautomatic control system was manufactured for trial, and applied to the SK16 shovel. Performance was then ascertained by field tests. This section will discuss the configuration and functions of the control system. . Configuration As illustrated in Fig. 10, the control system consistsof a controller, sensors, man–machine interface,and hydraulic control system. The controller is based on a 16bit microputer which receives angle input signals of the boom, arm, and bucket from the sensor。idual attachments For each attachment of the boom, arm, and bucket, the reference angle was changed 58 stepwise from the initial value, and the responses were measured。 and 2. when the control interval is less than 50 ms, control
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