JP6929334B2 - Equipment Suspension member design method - Google Patents

Description

The present invention relates to a method for designing an equipment suspension member mounted outside an aircraft.

Conventionally, an equipment suspension member that is attached to the outside of a helicopter or the like and suspends equipment such as a speaker or a light is known. As the suspension member for this type of equipment, a tube made of an aluminum alloy is generally bent.
This tube-made equipment suspension member is excellent mainly in terms of weight and cost, but on the other hand, it requires a bending jig (tube bender) that can process only a fixed curvature, and it is bent with high precision by so-called spring back. There is a problem that it is difficult.
Therefore, in order to solve these problems, a flat plate member machined is also used (see, for example, Patent Document 1).

JP-A-2002-294999

By the way, when designing equipment suspension members, it is necessary to consider design factors such as strength to withstand various loads and wind pressure load on the airframe, but flat plate members are made of tubes with a simple shape. Compared to, these design elements are complicated.
Therefore, in the design of the equipment suspension member made of a flat plate member, it was found that it was difficult to process after completing a series of studies and determining the shape, which sometimes resulted in rework.

The present invention has been made to solve the above problems, and an object of the present invention is to suppress design rework.

In order to achieve the above object, the invention according to claim 1 is a method for designing an equipment suspension member for designing the shape of a flat plate-shaped equipment suspension member mounted outside the aircraft.
A base shape setting step of setting the flat plate-shaped base shape having no opening, which is the base shape of the equipment suspension member,
After the completion of setting the base shape by the base shape setting step, an optimization analysis step of deriving the optimum shape of the equipment suspension member provided with the opening so as to satisfy a predetermined optimization condition, and an optimization analysis step.
It is determined whether or not the optimum shape derived in the optimization analysis step can be machined in the predetermined machining equipment, and if it is determined that machining in the predetermined machining facility is difficult, the process returns to the optimization analysis step. Processability judgment process and
A detailed analysis step of performing a detailed analysis of the optimum shape when it is determined in the process of determining whether or not the optimum shape can be processed, and a detailed analysis step of performing the detailed analysis of the optimum shape.
After the detailed analysis by the detailed analysis step is completed, it is determined whether or not the equipment suspension member has a predetermined weight or less, and if it is determined that the weight is not less than the predetermined weight, the weight reduction returns to the optimization analysis step. Judgment process and
It is characterized by having.

The invention according to claim 2 is the method for designing an equipment suspension member according to claim 1.
The detailed analysis step is characterized in that it is confirmed whether or not the optimum shape satisfies the strength required for the equipment suspension member, and if the required strength is not satisfied, the shape is modified .

The invention according to claim 3 is the method for designing an equipment suspension member according to claim 1 or 2.
The optimization condition is characterized in that the stress value of each part when a predetermined load is applied is set to be equal to or less than a predetermined threshold value, and the mass density is minimized.

The invention according to claim 4 is the method for designing an equipment suspension member according to claim 3.
In the detailed analysis step, the wind pressure load is within the permissible value, the natural frequency is detuned by a predetermined ratio or more with respect to an integral multiple of the excitation frequency, and each part is detuned when the predetermined load is applied. It is characterized in that a shape having a stress value equal to or less than the predetermined threshold value is obtained.

According to the present invention, when the optimum shape of the equipment suspension member is derived as satisfying a predetermined optimization condition and it is determined that this optimum shape can be processed by a predetermined processing facility, the optimum shape is determined. Is analyzed in detail.
As a result, even if it is determined that machining is difficult, it is sufficient to perform the optimization analysis again, and it is not necessary to repeat the detailed analysis, so that it is possible to suppress design rework as compared with the conventional case.

Equipment It is a front view of a helicopter equipped with a suspension member. It is a front view of the equipment suspension member. It is a flowchart which shows the flow of the design method of the equipment suspension member. It is a flowchart which shows the flow of the detailed analysis in the design method of the equipment suspension member. It is a front view of the helicopter equipped with the equipment suspension member of the modified example.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

First, the equipment suspension member 1 in the present embodiment will be described.
FIG. 1 is a front view of a helicopter (rotorcraft) H on which the equipment suspension member 1 is mounted, and FIG. 2 is a front view of the equipment suspension member 1.

As shown in FIG. 1, the equipment suspension member 1 is mounted on both sides of the fuselage of the helicopter H and suspends equipment E such as a speaker, a camera, a searchlight, and a sensor. The equipment suspension member 1 is made of a long metal flat plate whose thickness direction is along the helicopter H's front-rear direction (vertical direction on the paper surface in FIG. 1), and is from the lower end to the side along the side surface of the helicopter H's fuselage. It is curved upward while facing, and its upper end is formed in a shape extending toward the side.
Note that FIG. 1 shows only a schematic mounting state of the equipment suspension member 1, and omits the detailed mounting state of the equipment suspension member 1 and the later-described interface member 2 to which the equipment E is mounted. ..

Specifically, as shown in FIG. 2, the equipment suspension member 1 is formed so as to gradually widen from the lower end to the upper end of the curved portion, and the height of the lower end and the middle of the curved portion. Mounting portions 11 are provided in each of the portions.
These mounting portions 11 are portions to be mounted on the helicopter H, and are formed in a shape extending from the curved portion to the helicopter H side. Although not shown, each mounting portion 11 is formed in a U-shape when viewed from above and has a through hole 11a penetrating in the thickness direction, and a fixing portion of the helicopter H is provided in the U-shaped opening. In the sandwiched state, the fixing pin is inserted into the through hole 11a together with the fixing portion, so that the helicopter H is fixed to the body of the helicopter H.

The upper tip of the equipment suspension member 1 is a suspension portion 12 on which the equipment E is suspended. Specifically, in the suspension portion 12, the interface member 2 for suspending the equipment E is bolted, and the equipment E is suspended via the interface member 2.

Further, the equipment suspension member 1 is formed with a plurality of (four in the present embodiment) openings 13, ... Penetrating in the thickness direction. These plurality of openings 13, ... Are provided for reducing weight and air resistance, and are formed at positions and shapes that do not cause a problem in terms of rigidity, as will be described later.

Subsequently, a design method of the equipment suspension member 1 for designing the shape of the equipment suspension member 1 (hereinafter, simply referred to as “suspension member design method”) will be described.
FIG. 3 is a flowchart showing the flow of the suspension member design method, and FIG. 4 is a flowchart showing the flow of detailed analysis described later in the suspension member design method.

As shown in FIG. 3, in the suspension member design method in the present embodiment, the designer first sets the base model (base shape) of the equipment suspension member 1 to be designed (step S1).
This base model is a flat plate without an opening 13, and is roughly selected from, for example, conventional equipment suspension members, or roughly based on the helicopter H's body shape (side shape and position of fixed portion). Is set.

Next, the designer selects the material of the equipment suspension member 1 (step S2).
As this material, an appropriate material is selected in consideration of strength, weight, cost and the like, but an aluminum alloy is particularly preferably used from the viewpoint of weight.

Next, the designer sets the design area for the optimization analysis (step S3).
In this step, the portion of the equipment suspension member 1 (base model) to be analyzed in the optimization analysis performed in the next step is set as the design target. In the present embodiment, substantially all parts of the equipment suspension member 1 except for the two mounting portions 11 and 11 which are the portions engaged with the helicopter H and the suspension portion 12 on which the equipment E is suspended are set.

Next, the designer performs an optimization analysis for optimizing the structure of the design area set in step S3 (step S4).
In this optimization analysis, the optimum shape of the equipment suspension member 1 that satisfies the predetermined optimization conditions and constraint conditions is derived. The optimization condition is to minimize the mass density (that is, to reduce the weight most) while keeping the stress value of each part below a predetermined threshold when the maximum assumed load (weight of equipment E, load due to wind pressure, etc.) is applied. ). Further, the constraint condition shall limit the displacement with respect to each load. The optimization condition or constraint condition may include a condition related to the wind pressure load determined in step S62 described later and a condition related to the natural frequency determined in step S65.
By this optimization analysis, the portion that can be the opening 13 is obtained as a portion that does not have a problem even if the rigidity is low, and the optimum shape including the plurality of openings 13, ... Is derived.

Next, the designer determines whether or not the optimum shape derived in step S4 can be processed (step S5).
In this step, it is determined whether or not the derived optimum shape can be processed by a predetermined processing equipment (for example, one owned by the manufacturer or one that can be used in terms of cost).
The determination of processability in this step may be included in the optimization condition of the optimization analysis in step S4 after replacing the determination condition with a shape condition or the like.

If it is determined in step S5 that the optimum shape is difficult to process (step S5; No), the designer shifts the process to step S2 described above.

If it is determined in step S5 that the optimum shape can be processed (step S5; Yes), the designer performs various detailed analyzes (detailed analysis) on the optimum shape (step S6). ).
In this detailed analysis, various requirements such as strength required for the equipment suspension member 1 are individually confirmed to see if the optimum shape is satisfied, and the shape is modified as necessary.
In the following description, "equipment suspension member 1" refers to the one having the optimum shape at that time unless otherwise specified, and if it has been modified, the modified one is used. Point to.

Specifically, in the detailed analysis, as shown in FIG. 4, the designer first calculates the wind pressure load exerted by the equipment suspension member 1 on the airframe of the helicopter H (step S61).
In this step, the resistance area (wind receiving area) of the equipment suspension member 1 when receiving wind from the front is calculated, and when the aircraft flies at a predetermined speed, the wind at a predetermined wind speed is received at the resistance area. The wind pressure load in the case is calculated.

Next, the designer determines whether or not the wind pressure load calculated in step S61 is within a predetermined allowable value (step S62), and if it is determined that the wind pressure load exceeds the allowable value (step S62; No), the wind pressure. After appropriately modifying the shape (mainly the shape of the opening 13) in order to suppress the load (step S63), the process shifts to step S61 described above, and the wind pressure load is recalculated.

If it is determined in step S62 that the calculated wind pressure load is within the permissible value (step S62; Yes), the designer performs vibration analysis of the equipment suspension member 1 (step S64).
Specifically, in this step, the eigenvalue analysis is performed to calculate the natural frequency of the equipment suspension member 1.

Next, the designer determines whether or not the natural frequency of the equipment suspension member 1 calculated in step S64 is sufficiently (for example, ± 10% or more) away from an integral multiple of the vibration frequency by the rotor of the helicopter H. Determine (step S65).
Then, when it is determined that the natural frequency of the equipment suspension member 1 is not sufficiently separated from the integral multiple of the vibration frequency (step S65; No), the designer sets the natural frequency from the vibration frequency. After appropriately modifying the shape of the equipment suspension member 1 for detuning (step S63), the process proceeds to step S61 described above.
In this step, it is more preferable to confirm the detuning from the frequency at which the Karman vortex generated in the wake of the equipment suspension member 1 is generated.

Further, in step S65, when it is determined that the natural frequency of the equipment suspension member 1 is sufficiently separated from an integral multiple of the excitation frequency (step S65; Yes), the designer determines that the equipment suspension member 1 is sufficiently separated. The strength analysis of 1 is performed (step S66).
Specifically, in this step, the stress value of each part when the maximum assumed load (weight of the equipment E, load due to wind pressure, etc.) is applied to the equipment suspension member 1 is calculated.

Next, the designer determines whether or not the stress value of each part calculated in step S66 is within a predetermined allowable value (step S67), and if it is determined that the stress value exceeds the allowable value (step S67; No. ), The shape is appropriately modified to suppress the stress value (step S63), and then the process proceeds to step S61 described above.

If it is determined in step S67 that the stress value of the equipment suspension member 1 is within the permissible value (step S62; Yes), the designer ends the detailed analysis (step S64).

When the detailed analysis is completed, as shown in FIG. 3, the designer determines whether or not the weight of the equipment suspension member 1 is sufficiently reduced, that is, whether or not the equipment suspension member 1 has a predetermined weight or less. (Step S7), if it is determined that the weight reduction is not sufficient (step S7; No), the process proceeds to step S2 described above.
Further, in step S7, when it is determined that the equipment suspension member 1 is sufficiently lightened (step S7; Yes), the designer sets the shape of the equipment suspension member 1 as the final shape. Finish the design.

As described above, according to the present embodiment, the optimum shape of the equipment suspension member 1 is derived as satisfying the predetermined optimization condition, and it is determined that this optimum shape can be processed by the predetermined processing equipment. In some cases, a detailed analysis of the optimum shape is performed.
As a result, even if it is determined that machining is difficult, it is sufficient to perform the optimization analysis again, and it is not necessary to repeat the detailed analysis, so that it is possible to suppress design rework as compared with the conventional case.

Further, when the processability determination condition is included in the optimization condition of the optimization analysis, the processability determination process itself becomes unnecessary, and the rework of the design can be further suppressed.

The embodiment to which the present invention can be applied is not limited to the above-described embodiment, and can be appropriately changed without departing from the spirit of the present invention.

For example, in the above embodiment, the equipment suspension member 1 is attached to the lower surface and the side surface of the helicopter H, but the shape of the equipment suspension member according to the present invention is not limited to such a shape, for example, FIG. Like the equipment suspension member 1A shown in 5, the helicopter H may be formed in a substantially U shape attached to the lower surface and the upper surface.

Further, the equipment suspension member according to the present invention is not limited to helicopters as long as it is mounted on an aircraft, and can be applied to, for example, unmanned aerial vehicles.

1 Equipment Suspension member 11 Mounting part 11a Through hole 12 Suspension part 13 Opening E Equipment H Helicopter

Claims (4)

It is a design method of the equipment suspension member that designs the shape of the flat plate-shaped equipment suspension member mounted outside the aircraft.
A base shape setting step of setting the flat plate-shaped base shape having no opening, which is the base shape of the equipment suspension member,
After the completion of setting the base shape by the base shape setting step, an optimization analysis step of deriving the optimum shape of the equipment suspension member provided with the opening so as to satisfy a predetermined optimization condition, and an optimization analysis step.
It is determined whether or not the optimum shape derived in the optimization analysis step can be machined in the predetermined machining equipment, and if it is determined that machining in the predetermined machining facility is difficult, the process returns to the optimization analysis step. Processability judgment process and
A detailed analysis step of performing a detailed analysis of the optimum shape when it is determined in the process of determining whether or not the optimum shape can be processed, and a detailed analysis step of performing the detailed analysis of the optimum shape.
After the detailed analysis by the detailed analysis step is completed, it is determined whether or not the equipment suspension member has a predetermined weight or less, and if it is determined that the weight is not less than the predetermined weight, the weight reduction returns to the optimization analysis step. Judgment process and
A method of designing an equipment suspension member. The detailed analysis step is characterized in that it is confirmed whether or not the optimum shape satisfies the strength required for the equipment suspension member, and if the required strength is not satisfied, the shape is modified. Item 1. The method for designing an equipment suspension member according to item 1. The equipment suspension according to claim 1 or 2, wherein the optimization condition minimizes the mass density while keeping the stress value of each part when a predetermined load is applied to be equal to or less than a predetermined threshold value. How to design parts. In the detailed analysis step, the wind pressure load is within the permissible value, the natural frequency is detuned by a predetermined ratio or more with respect to an integral multiple of the excitation frequency, and each part is detuned when the predetermined load is applied. The method for designing an equipment suspension member according to claim 3, wherein a shape having a stress value equal to or less than a predetermined threshold value is obtained.

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