| When crawler crane unloads suddenly, especially under primary luffing working condition, it is probably going to make boom structure backward-tipping because of the flexibility of truss boom and luffing system, which could be prevented in advance by installing anti-backward-tipping system at bottom boom section. Because of the specialty of crane unloading working-condition, however, it is much too expensive to build real crane prototype and carry out destruction experiment, which all together makes anti-backward-tipping hard to be designed in order to protect the boom system. In addition, before the boom reaches the maximum elevation angle, the contact of boom and anti-backward-tipping system already exists, which makes minus moment on boom by anti-backward-tipping system inevitable when boom system under operation. Based on above all, virtual prototype simulations of crane unloading and regular operation are of great significance for construction engineering and can be used be discuss the effect of anti-backward-tipping system as well as minus moment on boom system.Based on the project of QUY500 crawler crane developed by Construction Machinery Center of DUT, the structure form and working principle of Hydro-Pneumatic anti-backward tipping system was studied in the paper, in which specifically virtual prototype simulation software- ADAMS was used to build up flexibility coupling virtual prototype for crawler crane. In addition, the hydraulic module in ADAMS was also applied to build up hydro-pneumatic anti-backward-tipping cylinder model to realize the hydro-mechanical coupling simulation for crawler crane.With the help of added loads, the unloading working condition was simulated and analyzed. The main findings include: the dynamic characteristics of hydro-pneumatic anti-backward-tipping and boom system were analyzed under condition of mechanical position limitation in order to figure out a reasonable angle of boom with minimum cylinder length; the effect of undamped anti-backward-tipping cylinder's inner diameter, inflation pressure on dynamic characteristics of cylinder and boom system was analyzed; the influence of diameter of damping hole on boom system and cylinder was analyzed; the comparison between with damping hole and without damping hole was made from aspect of anti-backward-tipping effect. Above findings all together provided reference in anti-backward-tipping design for crawler crane designer.The output characteristic equation built for hydro-pneumatic anti-backward-tipping system with damping hole was applied to discuss the influence of cylinder's inner diameter, inflation pressure and damping-hole diameter on output force, after which the comparison was made to find out the most powerful factor. In virtual prototype simulation, the output force curve for hydro-pneumatic anti-backward-tipping system was extracted to compare with curve from output characteristic equation, which proved the validity of virtual prototype and further confirmed that the most powerful factor influencing output force. All above work was of great instructive significance for hydro-pneumatic anti-backward-tipping system design from aspect of technical support. |
