Design And Research Of Luffing Mechanism Of Aerial Work Platform Based On Similarity Theorem

Updating and replacing speed for Aerial work platform (AWP) is faced up to challenges raised by dramatically increasing demand of its application in various areas. International manufacturers have already mastered the capability to produce serial products which possess leading technology reliable safety and adapts to the market demand completely. Whereas the design level of domestic companies is long way behind the world top-class standard, especially for the super-high combined boom AWP design. In shortage of introduction of new design method and concept, most local company still remain at stage of simulating and trial-manufacturing.Luffing mechanism works for changing the radius of AWP to take the platform to an appointed height position, the design of which is attached with great importance in overall design. Therefore time for scheme design of the whole machine could be shortened effectively by rapidly accomplishing the design of luffing mechanism, so that updating and replacing could be accelerated. Traditional design method comprises analogy graphing and analytical method which would lead to a large amount of calculation of scheme design due to the complexity of working conditions. As a consequence, it costs much time and effort to achieve reasonable luffing mechanism using traditional means. With100m level combined-boom AWP as researched object, design method based on similarity theorem is introduced to design of luffing mechanism utilizing mature and reliable product database to realize rapid design of new luffing mechanism.Mechanical models of two representative luffing mechanisms are simplified and formulas of force for luffing cylinders are deduced in this dissertation. Influence of length of every rod and joint position on the maxim force of luffing cylinder is studied. ADAMS model of upper structure of combined-boom AWP is built and analyzed by simulation. Formulas from analytical method are verified to be correct by the comparison of results respectively from these two methods.On the foundation of determining the kinetic and static features of the two typical luffing mechanisms, similarity optimization designing method based on similarity theorem is applied in the design of luffing mechanisms to generate the similarity principles and similarity ratio of parameters. Mathematic models for similarity optimization designing of knuckle boom and main boom luffing mechanism are built. Taking the highest force of luffing cylinder and the wave value of oil pressure to be minimized as the objective function, similarity ratio of geometrical dimensions in the similarity elements as designing variable, and with similarity constraints and performance constraints of mechanism considered, Genetic Algorithm toolbox is applied to solve the optimization problem so as to fulfill the design of new luffing mechanism. Feasibility of similarity optimization designing method for the mechanism is proved from dynamics similarity and kinetics similarity. A comparison is made between similarity optimal model and scaled model, result of which shows that model design based on the similarity optimization is better than the scaled method.The similarity optimization designing method introduced in this dissertation provides significant referring value for construction machineries with the same type of luffing mechanism.