Structural Optimization Design Of Rotary Platform Of Rotary Drilling Rig

As a kind of basic construction equipment for hole-forming operations,rotary drilling rigs play an important role in infrastructure construction such as roads and bridges.As the main component,the rotary platform must not only have sufficient bearing capacity,but also have enough weight to resist the large bending moment and large torque generated during operation.Therefore,the volume and mass of the rotary platform are often too large,which not only increases the requirements for system driving force and braking force,but also has an important impact on the stability of the whole vehicle,the safety of use,the reliability of work and the production cost.Therefore,this paper optimizes the structure design of the rotary platform to find the optimal structure to meet the performance requirements.The main research contents of this article is as follows.Firstly,based on the structure composition and workflow of rotary drilling rig,the dangerous postures of four typical working conditions of pressure drilling,drill lifting,lifting and displacement were determined.Based on the force path of the rotary platform,the mathematical model of force analysis of drilling mast assembly,luffing mechanism and other components is established.The load at the hinged holes of the rotary platform and rocker arm,luffing cylinder and mast cylinder under each working condition is calculated,and the load input of the simulation analysis is combined with the counterweight,main winch,gravity of the engine system and main winch pull.Secondly,the geometric model of the rotary platform was reasonably simplified and the finite element model was established based on the shell unit;then the static mechanical performance analysis and modal analysis of the typical working conditions in hazardous positions were carried out after setting constraints,loads and analysis steps for the rotary platform according to the mechanical model analysis results,and the results were used as the performance reference for subsequent optimization.Then,to ensure the performance of the rotary platform while reducing its mass,the topology optimization of its inner and outer double longitudinal beams is carried out based on Opti Struct.A multi-objective function with maximum stiffness,maximum average frequency and minimum mass for multiple working conditions was constructed based on the compromise planning method,where the weight of each working condition was determined by the analytic hierarchy process.The topology results show that there is a small reduction in the maximum displacement for each condition,i.e.,the stiffness performance is improved,and the design space weight is reduced by 6.35%.Finally,in order to further improve the stiffness and reduce the quality,so that each part has a reasonable thickness,taking the plate thickness of key parts as the design variable,the multi-objective parameter optimization was carried out.Firstly,the optimal Latin Hypercube was used to carry out the experimental design for the sensitivity analysis of 16 initial variables,and 7 optimization variables were selected by weighted contribution degree and main effect diagram of each factor in the analysis results to the target response;then,based on the fitting accuracy,the radial basis function neural network approximate model of optimization variables and objective function was established,and NSGA-Ⅱ algorithm was used to optimize parameters to obtain Pareto optimal solution set;Combined with entropy weight method and analytic hierarchy process,the combined weight of each design objective is obtained,and the comprehensive score of each Pareto solution is calculated to select the best scheme;According to the values of design variables of this scheme and Isight recommended scheme,every optimization model is generated respectively and simulation analysis is carried out.The results show that the optimal scheme based on combinatorial weight screening has better performance than the scheme recommended by Isight.Compared with the original model,the maximum displacement of the final scheme is reduced by4%~10% in each working condition,and the overall weight is reduced by 9.63%.In conclusion,the topology optimization and parameter optimization of the rotary platform based on the dangerous pose in typical working conditions have achieved a certain lightweight effect on the basis of improving the structural performance.This is beneficial to vehicle stability,safety and reliability,and can reduce the production cost and the design complexity of rotary drive system.It has certain practical application value and guiding significance to the design of rotary platform of rotary drilling rig.