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Analysis of Double Longitudinal spanning average beam of asphalt paver

Abstract This paper probes into the benchmark of automatic leveling of paver, compares the advantages and disadvantages of different formed average beams, makes a detailed analysis of the principle of spanning average beam, and points out the application prospect in combination with the actual situation of road construction in our country at present

key words: paver automatic leveling of spanning average beam road flatness

1 overview

at present, asphalt pavers with high technology are equipped with a set of corresponding automatic leveling system. The application of this system is the most effective way to improve road flatness. Correctly configuring, adjusting and using this system is the key to whether the automatic leveling system of paver can achieve the best effect

pavers with large operation width are equipped with two longitudinal and one horizontal automatic leveling controllers, which can realize three configuration methods: single longitudinal, one longitudinal and one horizontal, and double longitudinal, so as to adapt to different construction conditions. The single longitudinal configuration method is most commonly used to deal with longitudinal joints when paving in multiple widths; The method of one vertical and one horizontal is convenient and effective when the paving width is small (generally less than 6m). When the paving width is large (generally greater than 8m), the double longitudinal method can only be used. However, no matter which method is adopted, the longitudinal controller used to control the elevation and thickness direction error (flatness) is essential, and the use of the longitudinal controller must have an accurate and reliable benchmark. The longitudinal datum is also the reference line of the whole leveling system. Its setting and use is the guarantee of whether the whole leveling system can play its role to the greatest extent. Using the moving average beam as the benchmark is an advanced process method at present

2 basic principle of average beam

average beam has two categories: shovel type and spring floating type. Its basic principle is that the error amplitude value of the foundation height direction within the average beam length range is multi-level mathematical averaging and filtering through the geometric relationship (articulated) or mechanical relationship (spring floating), which reduces the amplitude, so that in the movement process of the paver, the motion track at the midpoint of the leveling beam becomes a transition smooth curve, and the absolute value of the curve amplitude is very small, It is within the allowable error range of the whole control system and serves as the reference standard of the automatic leveling instrument. It can be seen that the average beam is the benchmark installed on the body of the asphalt paver and moves forward randomly. Although it runs on the subgrade with large errors at the same time as the paver, it can produce an independent benchmark. This method is very suitable for road construction. It is not affected by the inherent longitudinal and transverse slopes of the road, and is not limited by the length of the road

the shovel connected average beam is then sent to the computer for data processing. The structural diagram is shown in Figure 1 (a), which generates an ideal reference point through pure geometric relations. In the figure, points a, B, C, D, e, F, G and H are the contact points between the average beam and the ground, and points K, m, N and P are the secondary hinge points, which are located at the midpoint of AB, CD, EF and GH; R. Point q is the third hinge point, which is located at the midpoint of KM and NP; Point O is the error detection point, and the position is set at the midpoint of TQ. The position shown in the figure is on the ideal ground. At this time, the heights of the second stage hinge and the third stage hinge are H1 and H2

figure a

if point a first encounters a high area during driving, the position is raised e, as shown in Figure 1 (b), at this time, because a rotates around B, d around m, R around Q, the points a, K, R move up relative to the original position, The positions of each point are:

△ ha=he △ hk= △ ha/2=he/2

△ hr= △ hk/2=he/4

△ ho= △ hr/2=he/2

this indicates that when an error occurs on the ground, the change of o point is 1/8 of this value. This can be used as the reference point of the leveling system. Theoretically, the more the number of stages of the average beam is, the more it automatically returns to the initial experiment after the experiment is completed, and the more the positions of the experimental force time curve, the experimental force, the peak value, and the yield force with obvious yield characteristics are displayed, the smaller the displacement change of the detection point is. Theoretically, the N-level average beam can obtain the reference line of 1/2n error. However, due to the limitations of the actual structure and use requirements, it can only be achieved at Level 3 or 4

figure b

because the accuracy of the articulated average beam is limited by the number of stages, and because of the structural limitations, it is easy to interfere with the horizontal and vertical straight tie rods of large pavers, so the average beam of this structure is less used in large pavers

another spring floating average beam. The average beam diagram of this structure is shown in Figure 2, which generates an ideal reference point through pure mechanical relations

figure 2

in the figure, a beam with weight g advances under the support of N springs with elastic coefficient K. When the ground is a horizontal plane, the elastic force of each spring is g/n, and the compression amount is s. according to Hooke's theorem:

s · k=g/n

s=g. (n · K)

during driving, a spring encounters a high area he, the beam changes from the original position h to the new position H1, the position of the beam is raised s>e, and the spring encounters a high area is further compressed, The compression amount becomes:

s1=s+he se

the elastic force generated by it becomes

f2=k · (s+he SE)

the compression amount of other springs decreases se, Each generated elastic force becomes

s1=k · (s-se

because g=f1 · (n-12) + f2

, it can be obtained that

gt= (n-1) · K · (s-sfont size= "1">e+k · (s+he SE)

g=ns-nse+he

combined with s=g/(n · K), it can be obtained that

this shows that for a beam mechanism composed of N springs, when an error he occurs in one of them, the position of the whole beam changes by only 1/n of this value

the above analysis is the case of the maximum error of this average beam in the uneven foundation. In fact, when the error area appears and passes under the average beam, the beam will tilt. According to the lever principle, the above maximum error he/n will occur only when the error area is below the center of gravity of the ground beam, and others are less than this value. But in general, the accuracy of the midpoint trajectory of a beam supported by a spring moving on a rough datum increases significantly with the increase of the spring. This track line can be used as the datum line of the leveling system

3 structure and characteristics of spanning average beam

average beam has a long history. The average beam used by early pavers, whether articulated or spring buffered floating, has a maximum length of less than 6m, and it can only travel on the unpaved foundation surface on the screed side of the paver, as shown in Figure 3

this usage has many shortcomings. First, since the average beam B can only drive on the unpaved road, the influence of subgrade roughness is difficult to be reduced to the lowest point; Second, when the width of screed C is close to the full width of the road, the average beam can not be used near the curb or shoulder slope; Third, when the paving width is large, the front drawbar A is too long to be used due to bending deformation; Fourth, because the flatness of the roadside area is much worse than that of the central area, and the error of the datum line is relatively large, these factors seriously restrict the use of the moving datum - average beam, so the average beam was not used as a preferred datum in the previous construction process

in order to solve the shortcomings of the old average beam, under the guidance of the above theoretical ideas, an ultra long average beam that crosses the screed and is very suitable for the whole paving operation of large pavers came into being. This average beam with unique structure is shown in Figure 4

in the figure, the spring floating average beam is driving in front of and behind the screed. The error of the midpoint a of the front beam is leveled. 7. After the tension machine is protected twice a month on average, it is less than 1/12 of the subgrade error. When the rear beam is driving on the paved road, its midpoint B error is averaged to be less than 1/8 of the error of the just paved road. Therefore, three knife points on both sides a and B form an approximately immobile reference point

the lever type superstructure composed of AO and Bo crosses the screed of the paver and is spaded on the traction arm of the paver through point O, forming two approximately stationary reference points with points a and B. the error of point O of the fuselage is reflected at point E and adjusted by the automatic leveling controller fixed at point E

the change process of this structure is shown in Figure 5

when the machine body is affected by the foundation and the screed is affected by the material, the traction arm will shift from O to o ', and the distance of the detection point of the leveling instrument will change from EF to e'f', that is, the controller detects an error signal e=e'f'-ef, so it sends a control signal until the error disappears

the main characteristics of the average beam of this structure are:

the whole set of use includes a span average beam with an installation length of nearly 18m on each side, which is very suitable for the leveling method of large width and double longitudinal. The part of the front 9m driving on the unpaved subgrade adopts slipper type surface contact, so as to reduce the impact of uneven subgrade; For the part that runs on the newly paved subgrade for the next 6m, wheel type rolling point contact is adopted to reduce the bonding resistance of the asphalt surface to the average beam

specially manufactured hollow rubber tires have good shock absorption and ground roughness absorption effects, and are very light in weight

the installation can be diversified. When the paving width is relatively narrow, the 15m average beam on one side can be decomposed into two 9m average beams (sliding shoe type) or two 6m average beams (wheel type), forming double benchmarks on both sides of the paver, which is very flexible and convenient

the installation method is flexible and has a wide range of applications. Through the connecting device and instrument installation position suitable for each kind of paving, the 15m average beam can be suitable for pavers of any width (m)

all structures are made of special aluminum alloy, which is light in weight, high in strength and non rusting, and is very suitable for the harsh environment of road construction

all components are welded and machined with special molds to ensure accuracy. The assembly error and welding quality have reached the domestic advanced level. After making a detailed analysis of the same structures of various large asphalt pavers, we studied and introduced the span average beams suitable for ABG411, agb422, ABG423, vogele1800, vogele2000, demag140 and other models. After the installation and use of several machines, the effect is good. In the construction of a bid section of Jiuhu railway, when paving the second layer of fine ingredients, the flatness was randomly checked, and almost all of them reached the mean square deviation of 0 7mm。 Practice has proved that this scheme of spanning Double Longitudinal average beam is successful and has a very broad prospect. In the current highway construction, the best way to ensure the flatness is to pave the whole width with the crossing Double Longitudinal average beam

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