Views: 2 Author: Site Editor Publish Time: 2022-07-25 Origin: Site
With the development and changes of the industrial chain, the modular construction of large-scale equipment in various industries is becoming more and more mature. In order to realize the installation of large-quality modules, in some large-scale engineering projects, cranes are used for the installation of large-volume and high-quality modular components, which is more difficult. Under the premise that SPMT hydraulic flatbed trailer is mature as a large-scale equipment transportation technology system, exploring the use of SPMT to directly install large-scale equipment in place has become a new requirement for modular construction and installation at this stage. When using SPMT for the installation of modular components, its achievable function must be analyzed, and the accuracy of its installation and positioning must be experimentally demonstrated.
The self-propelled modular flatbed truck SPMT is mainly composed of modules of different specifications, equipped with power unit PPU (Power-Pack-Unit), electrical system, control system, hydraulic system, etc. The PPU has a built-in diesel engine, hydraulic pump set, fuel tank, control panel and other components. The engine drives the hydraulic pump, outputs hydraulic power, and drives the hydraulic motors on each axle (each drive wheel can provide 60 kN of driving force) to make the vehicle run. At the same time, the PPU also provides hydraulic power for the lift of the flatbed truck, steering of all axles, and vehicle control. The combination of the PPU and the flatbed truck is shown in Figure 1.
In order to carry wide-body goods, flatbed trucks can be spliced horizontally to form a combined unit of more than 3 columns. In order to transport ultra-long goods, flatbed trucks can be longitudinally spliced into different numbers of axis modules. For the lifting and lowering of the goods, the flatbed truck can realize the lifting and lowering of 1 500 mm ± 350 mm. Linkage operation (synchronized operation) can be achieved between each independent flatbed truck by connecting the control systems of each vehicle, and the single-wheel axle can independently rotate +100°/-130°. Each axle rotates by a corresponding angle around the set rotation center, so that the whole vehicle group can achieve linear translation in any direction and 360° in-situ rotary motion.
1. SPMT degree of freedom analysis
As shown in Figure 2 (taking 6 axes and 2 longitudinal columns as an example), the SPMT vehicle group can achieve 6 degrees of freedom motion, namely translation in the X axis direction (degree of freedom 1), translation in the Y axis direction (degree of freedom 3), Lifting in the Z-axis direction (DOF 5), at the same time, it can realize the pitch around the X-axis (DOF 2), the roll along the Y-axis direction (DOF 4), and the in-situ rotation along the Z-axis direction (DOF 6).
Figure 2 Schematic diagram of the degrees of freedom of the SPMT vehicle group
2. 2, 4, 5 degrees of freedom working and control principle
As shown in Figure 2, 2, 4, and 5 degrees of freedom can be realized through SPMT support system, and precise operation control can be realized through man-machine dialogue. Each side of the hydraulic oil circuit of the SPMT flatbed support system consists of two pipelines, which supply oil to the far end (front end) and the near end (rear end) respectively. There are 4 independent support pipelines on both sides, and each pipeline is independently connected to a divided support area at the set support point, thus forming four independent support areas in the XY plane as shown in Figure 2.
Fig.3 Hydraulic principle of SPMT support system
As shown in Figure 3, through the setting of No. 2, 3, 11, and 17 valve bodies, the SPMT vehicle group can be divided into four independent support areas a, b, c, and d. Each support area is controlled independently at the same time. , the overall control can also be carried out through the man-machine dialogue interface, so as to realize the lifting operation with 5 degrees of freedom. Through the series connection of a, b, c and d support areas, the SPMT whole vehicle group can be divided into two support areas, front and rear along the Y direction, and the front and rear pitching operation with 2 degrees of freedom can be realized by the up-and-down adjustment of the front and rear areas. Through the series connection of a and d, b and c support areas, the SPMT whole vehicle group can be divided into two left and right support areas along the X direction.
As shown in Figure 4, the lifting speed of the SPMT support system can be adjusted in two levels according to actual needs. The first level adjustment is the control system setting, which can be set between 0 and 100%; the second level adjustment is potentiometer adjustment, which can be adjusted Adjust from 0 to 100. Theoretically, the lifting speed of the support system can be adjusted to infinitely small.
Fig. 4 Control mechanism of SPMT support system
To sum up, SPMT can realize the infinitely small lifting and lowering of 2, 4, and 5 degrees of freedom as shown in Figure 2 through the support system, as well as pitch and roll degrees of freedom. 3) 1, 3, and 6 degrees of freedom working and control principles 1, 3, and 6 degrees of freedom can be realized through the SPMT steering and drive system. Figure 5 shows the SPMT part of the steering mode, which can realize driving in any direction in the X-Y plane. It can also be steered at any angle with any point as the center in the plane.
Figure 5 Schematic diagram of part of SPMT steering mode
The drive wheels of SPMT drive system are evenly distributed around the geometric center of the flatbed. The driving force is provided by the hydraulic motor at the wheel side, and the buffering can be minimized during the driving process. According to the driving speed, it can be divided into normal mode and micro-travel mode. In the normal mode, the throttle (manual control) controls the engine speed to control the output pressure and flow of the hydraulic pump to control the hydraulic motor speed. In the micro-travel mode, the system input setting can be performed. At a certain speed, it can automatically control and drive at a constant speed, and theoretically, the micro-travel speed can be close to infinitely small.
To sum up, the SPMT drive and steering system can enable the vehicle group to achieve micro-translation and rotation in any direction in the plane, and can achieve 1, 3, and 6 degrees of freedom movement as shown in Figure 2.
From the above analysis, it can be seen that through the support, steering and driving system of SPMT, the motion of all degrees of freedom as shown in Figure 2 can be realized, and the theoretical driving speed of each degree of freedom can be infinitely small, combined with them in the X-Y plane, a large number of arbitrary combinations can be combined. It can install and position large-scale and large-mass modular components.