Multi-objective Optimization Design Of Luffing System Of Mobile Harbor Crane

Mobile harbor crane is a multi-purpose lifting equipment with good mobility, nice adaptability and excellent economy, which has been widely used in port container, cargo and bulks lifting fields. And it has a history of nearly sixty years in overseas. The luffing system, the core component of the mobile harbor crane, has been playing an important role in design indicators and performance of the mobile harbor crane.In this paper, on the research basis of luffing jib crane’s luffing system, taking the luffing system of harbor mobile crane as research object, the composition and working principle are analyzed and a multi-objective optimization mathematic model is established. Furthermore, two key problems of multi-objective optimization are explored based on grey system theory. The main research work and results of this paper are as follows:(1) The principle of load level luffing during the luffing process is studied, a mathematic model, which is composed of load level luffing, the boom’s stress and the force of the luffing cylinder, is built. Then, with the change of the coordinates of the pulley block in the tower, the changing trends of the difference of the hook trace, the stress of the boom and the difference of the luffing cylinder force during the luffing process are researched.(2) Taking the difference of the hook trace, the boom’s stress and the difference of the luffing cylinder force as objectives, a multi-objective optimization mathematic model is established. And take YHC280harbor mobile crane for example, the multi-objective optimization problem of the luffing system is settled by using linearity weighted method.(3) Faced with the problem that how to achieve the most reasonable Pareto solution and the optimal and worse order of several Pareto solutions of a multi-objective optimization problem, take YHC280harbor mobile crane for example, by adopting ideal point method, linearity weighted method and weight-square method, three Pareto solutions are obtained of the multi-objective optimization problem of the luffing system. Then based on grey clustering method, the most reasonable Pareto solution and the optimal and worse order of three Pareto solutions are achieved.(4) Faced with the drawbacks when using traditional weighting methods to solve the multi-objective optimization problem, an experts evaluation method of weighting coefficient based on grey system theory is introduced. With the application of it to solve the multi-objective optimization problem of YHC280harbor mobile crane’s luffing system, it shows that the method is more reasonable and effective than traditional weighting methods when dealing with the multi-objective optimization problem.In this paper, a multi-objective optimization mathematic model of harbor mobile crane’s luffing system has been established. Then, take YHC280mobile harbor crane’s luffing system for example, two key problems of multi-objective optimization design have been researched based on grey clustering method and experts evaluation method of weighting coefficient. The results show that two methods are effective and can boost the validity of the design when solving the multi-objective optimization problems.