【導(dǎo)讀】液壓泵站概述及液壓泵站油箱容量系列標(biāo)準(zhǔn)????????§液壓缸主要零件的結(jié)構(gòu)、材料及技術(shù)要求???????傳遞原理、18世紀(jì)末英國(guó)制成世界上第一臺(tái)水壓機(jī)算起，也已有二三百年歷史了。年內(nèi)出現(xiàn)的新事物。動(dòng)化技術(shù)，使它在國(guó)民經(jīng)濟(jì)的各方面都得到了應(yīng)用。液壓傳動(dòng)在某些領(lǐng)域內(nèi)甚至已占有。因此采用液壓傳動(dòng)的程度現(xiàn)在已成為衡量一個(gè)國(guó)家工業(yè)水。平的重要標(biāo)志之一。此外，在液壓元件和液壓系統(tǒng)的計(jì)算機(jī)輔助設(shè)計(jì)、計(jì)算機(jī)仿真和優(yōu)化以及微。機(jī)控制等開(kāi)發(fā)性工作方面，更日益顯示出顯著的成績(jī)。才用到拖拉機(jī)和工程機(jī)械上。自1964年從國(guó)外引進(jìn)一些液壓元件生產(chǎn)技術(shù)、同時(shí)進(jìn)行

　　

【正文】 s for the transfer of the sensor and actuator data between the test stand and the control puter (with realtime operating system) is also installed. The hydraulic cylinders include position and pressure sensors that are used as controller inputs. Thus dynamic tests can be carried out to examine the cooperation between the mechanical and hydraulic ponents and the electronic control system. The hip plate of the experimental setup is mounted on a pair of linear bearings, and thus is mobile in vertical direction. When bined with the foot, as shown in Fig. 3, or the passive wheel used on the hind leg of the bined legged and wheeled system, this allows loading tests on the leg while performing walking motions. Mechanical stops below the hip plate allow the foot to be lifted in the swing phase of the walking motion. The first (unloaded) tests have shown the mobility of the anthropomorphic leg mechanism to be very good, and the optical fieldbus system has also proven to be reliable. . . 3. SPEED ADAPTATION Insufficient Hydraulic Flow As already mentioned, the weight and size of the onboard power pack is limited and has to be kept low. When moving several cylinders simultaneously or with a high speed the hydraulic supply can bee insufficient and the pressure will collapse. In this case the resulting movement depends mainly on the sizes of the proportional valves and external loads on the cylinders. The trajectories of the feet and platform bee erratic. When ALDURO is near limit of its stability such behaviors can lead to instability and toppling of the system. As the safety issue is a very important one (people could be harmed) this pressure collapse has to be prevented. To investigate this behavior, a circular movement (radius m, velocity m/s) of the foot in the horizontal plane 1m below the hip was chosen as a reference. This trajectory has the advantage that it actuates all three unlocked cylinders. With a typical vertical stepping movement of the foot the sideways cylinder (no. 2 in Fig. 4) is nearly stationary. The inverse kinematics for the mapping of the . . foot coordinate into the coordinate space for the three cylinders has been developed in the C++ programming environment Ma a a aBILE [3]. When implemented on the test stand the resulting trajectory of the foot . . degenerated to a rounded rectangle (Fig. 5). To increase the hydraulic consumption, both sets of hydraulic cylinders have been used (. leg cylinders and set of four cylinders on the ground). As we can see in Fig. 6, cylinder no. 2 lags far behind its sinusoidal setpoint curve. The linear movement of the cylinder indicates a fully open proportional valve. The available hydraulic volume flow is clearly insufficient. Trajectory Speed Reduction The problem of uncontrollable movements can be approached from different directions: Redimensioning of pump and valves, Predict insufficient flow/pressure with detailed model of hydraulics and recalculate critical movements with lower velocities, Detect position errors due to pressure drop and slow down all movements, while maintaining trajectories. The first approach increases the weight of the hydraulic system and is thus undesirable. The second is undesirable because of puting power required and inaccuracy in the hydraulic model. Therefore, detection of the position error and slowing down the movement was chosen and implemented here. Instead of recalculating all trajectories for the case of a necessary deceleration, the time variable on which all trajectories depend is slowed down. To this end a new time variable is introduced. This trajectory time or model time t* can be expressed as a function of realtime t and the error dependent factor for the time increment All trajectories are functions of this t* For the control system running on a real time operating system we need the discrete relationship between t and t* for time step i. As all trajectories are functions of t* they will all be simultaneously slowed . . down or sped up, depending on k mt。 i. As an indicator for insufficient hydraulic flow, a function of the position errors of the cylinders is chosen. The vector s j contains the setpoint positions for the cylinders in each leg and i j the vector of measured positions. The difference is the error in meters. Where fl stands for front left, hr for hind right and so forth. With the weight matrix W, the influence of the four cylinders in each leg on the foot position can be adjusted. We take the normalized weighed sum of the squares of the errors for all cylinders e and its first time derivation de and normalize both with the admissible errors (thresholds e thr and de thr). If the sum of e and de exceeds the upper limit, the model time is slowed down. As both e and de are normalized with a threshold, this upper limit can be . . fixed. In this case it is 2. The third threshold (lower limit) is used to decide when to increase the speed again. To prevent a decrease in error triggering a stop in deceleration or even an acceleration, even if the error is still too large, de is only added if it is positive. where ?k mt,dec is the rate of change of k mt for deceleration and ?k mt,acc is the same for acceleration. K mt has to stay inside the limit [k mt,min? 1]. Results Values for thresholds, acceleration and decelerationrates of model time and cylinder weights are set empirically. The cylinders at the hip joint have a higher influence on the foot position than cylinder no. 4 at the knee. The corresponding weighing is set to 2:1. As the system has to react very quickly to errors,the deceleration rate ?k mt,dec is high. To prevent too much oscillation, the acceleration rate ?k mt,acc is set lower than ?k mt,dec.] . . Fig. 7: Cylinder positions for sp