The Helicopter Rotor Aeroelastic Research Of Multi-Objective Vibration Reduction Optimization By Modal Shaping

Helicopter plays an important role in national defence and economic construction. The design of helicopter especially the rotor system design is the essence of the dynamics de-sign. The dynamic of rotor system has three problems including the vibratory loads, vibra-tion, and dynamic stability. The aeroelastic optimization of a helicopter rotor is currently one of the hot researches at home and abroad. The aeroelastic properties of helicopter rotor directly affect the performance and flying security. The dynamic design of helicopter rotor has many factors influencing, relating to the aerodynamics and noise, structural dynamics, vibration and control of science and knowledge and various disciplines coupling. In the past the conventional blade design process was controlled mainly by the designer's experience and by trial and error. Since the 1980s with improved understanding of helicopter analyses and efficient optimization schemes, attempts are being made to apply design optimization techniques and eliminate the expensive man-in-the-loop iterations. In recent twenty years, the designers carried out an extensive and intensive research in helicopter dynamics opti-mization, because of the helicopter rotor dynamics optimization having itself particularities and complexity, it being not yet mature. The dissertation aims at analyzing the rotor aeroe-lastic model, providing the solutions of the rotor dynamics strategies and plans problems, establishing engineering applications the optimum design of the rotor dynamics.The dissertation first analyzed the dynamics design problems existing, the situation research of the helicopter dynamics, rotor aeroelastic and the helicopter rotor aeroelastic optimization, the aeroelastic stability optimization and the optimization of the hub vibration reduction research. Then it packed up rotor aeroelastic model, analyzing helicopters vibra-tion reduction methods and the effectiveness and feasibility of modal shaping for vibration reduction. It deduces the hub vibration loads with the superposition of the root shear force. It presents the methods and strategies of multi-objective optimizations with the objective functions of hub and pitch links vibration loads and many constrains. At last, it sets exam-ples to verify the model being right, the method of vibration reduction being effective and the methods and strategies of optimization being robust.The dissertation is based on the principle of Hamilton to pack up the coupling rotor system of aeroelastic model, and then use the finite element method for the element discrete of structural models, packing up the structural systems finite element model. Through the solution of aeroelastic finite element model of rotor system, it is verified that the estab-lishing model is effective and robust by giving the examples.Based on the solution of the mode frequencies and mode shapes, the dissertation use the method of modal superposition to derive for the rotor blade root force and the hub loads computation. It gives the example to verify the modal shaping method for vibration reduc-tion and the computation of the hub load being the right and effectiveness. With the rotor aeroelastic and the loads computation models, the dissertation brought forward to definitions of multi-objectives optimization, the problem of the solution, the optimal strategy and optimal process. It uses a perturbation method and chain rule of the sensitivity analysis and analyzes the sensitivity of the objective functions and constraint functions about variables. It uses the polynomial response and kriging model for surrogate model in the rotor with the aeroelastic and load computation models, using the suited im-prove genetic algorithm of the annealing algorithm for multi-objective optimization.The dissertation defines the multi-objective optimization based on the helicopter rotor aeroelastic model and modal shaping for vibration reduction of the hub load. Constraints are imposed on blade rotating frequencies, aeroelastic stability and autorotational inertia et al. The objective functions are minimum hub loads, minimum pitch link force and minimum mass of the rotor blades. The examples are the articulated rotor of sa349/2 helicopters and model of bearingless rotor. With a different type of rotor, the dissertation uses the different border conditions, presents specific constraint functions, objectives functions and design variables, using the corresponding optimal strategies of the models for multi-objective op-timization. Through the contrast of optimization and experiment results at home and abroad, it verifies that the aeroelastic model, model of modal shaping for vibration reduction and the method of multi-objective optimization and optimization strategy are right and robust.The dissertation has some obvious invotiations with the hub vibration loads and pitch links forces calculating by modal shaping method, the integrated use with the sensitivity analysis methods of helicopter rotor aeroelastic vibration reduction by multi-objective op-timization, polynomial and kriging approximate agency model, the improvement genetic and simulated annealing algorithm and the advanced bearingless rotor section optimization. The deduction and calculation of dynamics model and the solution of multi-objective opti- mization and the optimum strategy have some engineering meaning, and the research pro-ject on the other flight situation and other structures optimized design has some reference.