1 optimization scheme element 1.1 design variable design vector meaning = especially, fantasy is not the aircraft airfoil and fuselage shape parameters.
Since the wing shape is selected when designing the wing tail, only the plane shape parameters of the airfoil are considered; and because the profile of the concave and convex surface has good aerodynamic and stealth performance, the upper and lower convex arcs are Slope angle of the normal at the concave arc turning point The upper and lower tangential slope angles of the concave tip on both sides of the profile have a great influence on the stealth performance of the aircraft. Therefore, the selected design parameters are the outer wing of the heart wing, and the wing tip length (3) The wing is exposed to a half-length; the wing's inner wing leading edge sweep angle; the wing's outer wing leading edge sweep angle; the wing inner and outer wing breakpoint position is away from the exposed wing root; the trailing edge of the wing The frontward shift of the vertices is relatively free of vertices; the exposed chord of the XS flat tail is long and flat; the flat tail is exposed to a semi-length; the flat tail has a sweeping angle; the 12 tails are exposed and the tail is exposed. 1 vertical tail leading edge sweep angle Tu, vertical tail tilt angle, D concave and convex curved body body section upper and lower convex arc and concave arc turning point at the normal slope state; medium concave and convex curved body body side of the convex surface The upper and lower tangent slope angles of the sharp points.
These design changes are used not only because they have a large influence on the objective function, but also because they are decisive for the shape of the aircraft, the plane shape of the wing 4 can be determined, and the stereo geometric information of the wing tail is completely determined; The width of the convex surface of the concave-convex surface body and the height of the upper and lower half can determine the fuselage profile.
1.2 Objective Function The 4th generation fighters require both supersonic cruise capability and outstanding maneuverability. In addition, there are requirements for flight payload take-off and landing performance. Whether these requirements can be met depends on the aerodynamic characteristics of the aircraft's lift-to-drag ratio, the maximum lift coefficient of zero-lift resistance, and the stealth characteristics of the forward lateral average of the downtime.
Therefore, 7-inch aircraft shape parameters in this paper aerodynamic and hidden body optimization design, according to the design requirements of the 4th generation fighter, the selected objective function is the average and maximum value within f, into. Received date 19991 7=0.8 Maximum lift-to-drag ratio low speed application=0.2 Maximum lift coefficient Large angle of attack normal force coefficient.
1.3 Constraint constraints are taken as constraints on the geometric dimensions of each design variable and the parallelism of the airfoil edges. Designers can use different constraints to select + the same combination of airfoil shapes.
2 The optimization model determines the weight of each objective function by the fuzzy subset method.
According to the requirements of the overall design of the fighter, determine the ideal value and the lowest acceptable value of each target. Use the fuzzy number åž buried linear function to establish the satisfaction function of the satisfaction function and the constraint of each target respectively, 〃 4. Then. According to the same design idea, the multi-objective total satisfaction function of the multi-standard evaluation function is established as the objective function, and different optimization models are established.
2.1 The comprehensive weighting model uses the comprehensive weighting method to establish the total satisfaction function of multiple targets, 0, establish the fuzzy optimization model 1find according to the empirical formula of the variable weight, use the weighting of the weeping weighting model 2 for the weeping evaluation method The target weeping development. Give priority to improving the satisfaction of the most important goals. When the most important goals can't be changed, Ke improves other secondary sleeves. It corresponds to the design illusion of the unbalanced development of each design.
2.2 Target-type fuzzy decision model In engineering optimization design, constraints are often the objective conditions that must be met, and the goal is often the designer's subjective efforts to improve the psychological expectations of the design object. For the constraint, it can be satisfied, for the target. It is often better. To reflect this asymmetry. The model 1 fuzzy decision model optimization model can be constructed. This model focuses on improving the goal of minimum satisfaction and embodies the design idea of ​​focusing on weak links. However, when the worst goal can no longer improve the goal of the second time, the goal is often not improved. If you want to consider the difference between the different goals, you can use the weight. The corresponding optimization model 4 is that in this model, the importance index, that is, the weight, the smaller the goal, the easier it is to determine the total satisfaction function.
In this model, the weight mountain. It is not necessary to carry out the naturalization process, so that the weights are too small due to the large number of targets. , are big factories, and are filtered out.
2.3 The optimal factor highlights the model in engineering design. I hope to highlight the better indicators to make them optimal. Based on this design idea, the optimal factor prominent model can be established. 5 It can be seen from the model of the model that the total satisfaction evaluation function of multiple targets is taken as the largest product of weight and satisfaction in each target. The design idea of ​​focusing on excellence, superiority and most important factors was emerged.
In each of the above optimization models, the designer can adjust and determine the subjective wishes and design experience of the designer, and the solutions obtained for different solutions belong to the fuzzy solution set corresponding to different target satisfaction and constraint satisfaction.
3 optimize the results of the aerodynamics and 3 calculation procedures, the program after a number of measurements of the shape parameters within a reasonable range. Refer to 1.
Comparison Model 1 Model 2 Model 3 Model 4 Model 5 Plant 2 The maximum deviation of the mean; the parameters for each individual target satisfaction are theoretical. Variable weight can prevent the extreme situation of 0 from happening. In addition, from the value of the pair, the optimization result obtained by using the weighted comprehensive weighting model, the balance between the satisfaction of each single target should be optimized by using the constant weight. result.
The improvement effect of the default decision model on the worst solution is often obvious, which makes the lowest single target satisfaction much better than other models.
In the optimal factor prominent model, the satisfaction of the optimal goal is achieved to achieve the intended purpose of the model. Because the multi-objective total satisfaction in the model is the target of the goal satisfaction and the higher weight in the single goal, the impact on the multi-target total satisfaction is more likely, but the total purity of the pure fullness is determined by the uncertainty. Total target satisfaction. When using the constant right, the weight of each target is fixed, and the satisfaction of each target is related to the satisfaction interval of the target. Therefore, the total satisfaction evaluation function is affected by each one, and the total influence is larger, that is, each target The value of the satisfaction interval will determine the optimization result.
According to the above analysis, the value of the satisfaction interval of each target should be weighed against the subjective desire of the target optimization trend and the possible range of the objective function, that is, the possibility of individual desire and realization, according to the experience or the result of trial calculation. , reasonably determined.
The five optimization models given in the conclusions embody different design ideas. The optimization results of the examples prove the correctness and practicability of the optimization model. Designers can choose different optimization models according to different design ideas or design purposes. In addition, designers can choose different combinations of different types of cargo tails by applying different constraints to the design variables. The procedures developed in this article and in-depth research can be used by designers in their initial design.
The 1st modern design of the complex and complicated structure of the illusion of Chen Yue. 1 core 1 Beijing University of Aeronautics and Astronautics Press, 1992.
2; Zhuang. Fuzzy system theory;! 1 computer elbow,
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