Study On The Key Design Technologies Of Multi-Crawler Travelling Gear

In recent years, the engineering applications of continuous mining complete set of equipments including bucket wheel excavators, such as in the large lignite and metal open-pit mine, show the advantages of high efficiency, short construction period and low cost. The bucket wheel excavators move toward high production capacity and large-scale direction. The multi-crawler devices are used to carry the huge weight of large bucket wheel excavators, and to drive and steer the entire machine. Their performance and reliability directly influence work efficiency and operational safety of the bucket wheel excavators. Therefore, developing for large multi-crawler bucket wheel excavators is one of the main tasks in mining machinery industry at present. Combining with the project of research cooperation, the key design technologies of multi-crawler devices such as driving theory, determination methods of the main parameters, virtual prototype simulation, driving experiment and design calculation platform development have been studied in this paper.This paper comprehensively analyzed the structure features, steering method and steering mechanism, driving device and control method of the multi-crawler. Additionally, the theoretical study and the development trend of large-scale crawler are also reviewed.Stress analysis of crawler during steering is the basis of studying the theory of multi-crawler device. In this paper, the stress of various crawlers when multi-crawler device on steering has been studied, considering factors like crawler width, longitudinal and lateral deviations of the rotation center in the instant of the crawler contacts to the ground. And the influence of various factors on crawler stress has been analyzed. Mathematical model and the solution method of steady steering analysis suitable for all kinds of multi-crawler devices have been putted forward. Taking three-crawler device as an example, the non-steady steering property has been analyzed, and the dynamic model and the numerical solution method of non-steady steering movement have been proposed.Based on the steering theory of multi-crawler, the commonly used calculation formulas of turning resistance, theoretical turning radius, sweep turning radius and the turning radius of each of the tracks on multi- crawler vehicles are provided. The main calculation methods of the critical parts are also proposed. Using the classical Newtonian mechanics, the mathematical equations of hanging chains for the ideal flexible chain have been deduced, based on which the calculation formula of the discrete track-chain is studied. And then, the calculation formula of the tension force of the steady track chain is deduced. According to the issues on disconnection of the chain that will affect the safety of the vehicle, four quantifiable indicators for judging the risk of disconnection have been put forward.A digital prototype of multi-crawler device is established and virtual tests on the performance of the three-point-six-track under multiple operating conditions were simulated. Both of the numerical simulation method and the virtual prototype simulation method can be employed to forecast the driving performance of the multi-crawler. The accuracy of simulation results should be verified by experiments, and according to the largest six-track bucket wheel excavator operated in Yuanbaoshan mine of China, the driving parameters were tested. The test results and virtual prototype simulation were compared to verify whether the numerical simulation and virtual prototype simulation results are reasonable or not.This paper explored the design and computation platform of the multi-crawler. It includes the following contents concretely: (1) Based on Solidworks (3D modeling software) and MATLAB, the digital design platform of the three-point multi-crawler was researched and developed; (2) Based on MATLAB/GUI, the design and computation platform of three-point-six-track was established. Finally, the calculation module of steering was verified by the lateral force, power and turning speed. And also the interplay relationship among pressure and force of supporting wheels, the ball hinge force and other design parameters were analyzed comprehensively.In short, this thesis obtained the important progress for the large-scale multi-crawler research in the force imposed on the crawler device when steering, steering performance analysis in steady and nonsteady cases, virtual prototyping simulation and development of the design platform. It not only provided the advanced analysis methods and software, but also provided the scientific basis of independent research and development of a large-scale crawler device for our country. So it achieved significant the theoretical value and the practical application.