1、东北大学毕业设计（论文）外文翻译 外文翻译 原文： AUTOMATING THE CONTROL OF MODERN EQUIPMENT FOR STRAIGHTENING FLAT-ROLLED PRODUCTS The company Severstal completed the successful introduction of new in-line plate-straightening machines (PSMs) on its 2800 and 5000 mills in August 2003 1, 2, 3. The main design features of th
2、e machines are as follows: each machine is equipped with hydraulic hold-down mechanisms (to improve the dynamics and accuracy of the machine adjustments and more reliably maintain a constant gap)； the machines have mechanisms to individually adjust each work roller with the aid of hydraulic cylinder
3、s (this broadens the range of straightening regimes that can be realized by providing a measure of control over the change in the curvature of the plate)； each work roller is provided with its own adjustable drive (to eliminate rigid kinematic constraints between the spindles)； the system of rollers
4、 of the PSM is enclosed in cassettes (to facilitate repairs and reduce roller replacement costs)； the PSM has a system that can be used to adjust the machine from a nine-roller straightening scheme to a five- roller scheme in which the distance between the rollers is doubled (this is done to widen t
5、he range of plate thick-nesses that the machine can accomodate). Thus, the new straightening machine is a sophisticated multi-function system of mechanisms that includes a wide range of hydraulically and electrically driven components controlled by digital and analog signals. The entire complex of P
6、SM mechanisms can be divided into two functional groups: the main group, which includes the mechanisms that partici-pate directly in the straightening operation (the hold-down mechanisms, the mechanisms that individually adjust the rollers,the mechanisms that adjust the components for different stra
7、ightening regimes, the mechanism that moves the top roller of the feeder, and the main drive)； the auxiliary group (which includes the cassette replacement mechanism, the spindle-lock-ing mechanism, and the equipment that cools the system of rollers). Although 东北大学毕业设计（论文）外文翻译 the PSM has a large nu
8、mber of mechanisms,the use of modern hydraulic and electric drives has made it possible to almost completely automate the main and auxiliary operations performed on the PSM and the units that operate with it. Described below are the features and the automatic control systems for the most important m
9、echanisms of the plate-straightening machine.The operating regimes of those mechanisms are also discussed.The hydraulic hold-down mechanisms (HHMs) of the sheet-straightening machine function in two main regimes:the adjustment regime；the regime in which the specified positions are maintained.There a
10、re certain requirements for the control system and certain efficiency criteria for each regime. In the adjustment regime, the control system for the hydraulic hold-down mechanisms must do the following: synchronize the movements of the hydraulic cylinders and keep the angular deeflection within pres
11、cribed limits； maximize speed in adjusting the machine for a new plate size； maintain a high degree of accuracy in positioning the mechanisms； Fig. 1. Block diagram of the control system of the hydraulic cylinder. The control system has the following requirements when operating in the maintenance re
12、gime: stabilize the coordinates of the top cassette and the top roller of the feeder with a high degree of accuracy； minimize the time needed to return the equipment to the prescribed coordinates when deviations occur (such as due to the force exerted by a plate being straightened). Need for synchro
13、nization. Experience in operating the plate-straightening machine in plate shop No. 3 at Severstal has shown that the most problematic factor in adjusting the machine is the nonuniformity of the forces applied to the hydraulic cylinders. This nonuniformity is due to the asymmetric distribution of th
14、e masses of the moving parts of the PSM (in particular, the effect of the weight of the spindle assembly). Displacement of the “hydraulic zero point” relative to the “electrical zero point” in the servo valves is also a contributing factor.The latter 东北大学毕业设计（论文）外文翻译 reason is more significant, the
15、smaller the volume of the hydraulic cylinder.Thus, the HHM of the top roller of the feeder is the most sensitive to drift of the zero point. There are also other factors that affect the dynamism,simultaneousness,and synchronism of the operation of the hold-down mechanisms: differentiation of the fri
16、ctional forces on parts of the hydraulic cylinders due to different combinations of deviations in the dimensions of the mated parts, despite the narrow tolerances； differences in the “springing” characteristics and the indices characterizing the inertia of the hydraulic supply channels (due to diffe
17、rences in the lengths of the pipes leading from the servo valves to the hydraulic cylinders). Thus, since the PSM is not equipped with devices to mechanically synchronize the operation of the cylinders, the ransmission of signals of the same amplitude to the inputs of the servo valves inevitably res
18、ults in a speed difference that can seriously damage the mechanisms. To minimize and eliminate the effects of the above-mentioned factors, we developed an algorithm for electrical synchronization of the hold-down mechanisms. The HHM of the top cassette, composed of four hold-down cylinders and four
19、balancing cylinders, is designed to ensure mobile adjustment of the machine to set the required size of straightening gap (in accordance with the thickness of the plate) and maintain that gap with a specified accuracy in the presence . and absence of a load on the housings from the straightening for
20、ce. The hydraulic system of the hold-down mechanism is designed in such a way that only one chamber of the hydraulic cylinders is used as the working chamber.The second chamber is always connected to the discharge channel.The top cassette is lowered when the balancing forces are overcome by the hold
21、-down cylinders.The cassette is raised only by the action of the balancing cylinders.This arrangement has made it possible to eliminate gaps in the positioning of the equipment. The HHM of the top roller of the feeder consists of two hydraulic cylinders. Hydraulic fluid is fed into the plunger chamb
22、er when the roller is to be lowered and is fed into the rod chamber when it is to be raised. Control Principles. Individual circuits have been provided (Fig.1) to control the hydraulic cylinders of the hold-down mechanisms.The control signal (Xctl) sent to the input of the servo valve is formed by a proportional-integral (PI) controller (to improve the sensitivity of
