JP6606336B2 - Equipment suspension design method - Google Patents

Description

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

2. Description of the Related Art Conventionally, an equipment suspension member that is attached outside a machine such as a helicopter and suspends equipment such as speakers and lights is known. This type of equipment suspension member is generally a bent aluminum alloy tube.
This equipment suspension member made of tube is excellent mainly in terms of weight and cost, but it requires a bending jig (tube bender) that can only be processed to a fixed curvature, or it is highly accurate bending processing by so-called springback. There is a problem that it is difficult.
Therefore, what machined the flat plate member is also used as what can eliminate these problems (for example, refer to patent documents 1).

JP 2002-29499 A

By the way, when designing equipment suspension members, it is necessary to consider design elements such as strength to withstand various loads and wind pressure load on the aircraft. Compared to the above, these design elements are complicated.
For this reason, in the design of the equipment suspension member made of a flat plate member, it has been found that the processing is difficult after the completion of a series of studies and the shape is determined, which may be reworked.

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

In order to achieve the above object, the invention described in claim 1 is a design method of an equipment suspension member for designing a shape of a flat equipment suspension member mounted outside an aircraft.
An optimization analysis step for deriving an optimal shape of the equipment suspension member that satisfies a predetermined optimization condition;
A workability determination step for determining whether or not the optimum shape derived in the optimization analysis step can be processed with a predetermined processing facility,
A detailed analysis step for performing a detailed analysis on the optimum shape;
Equipped with a,
The optimization condition is to minimize the mass density while setting the stress value of each part when a predetermined load is applied to a predetermined threshold value or less,
In the detailed analysis step, the wind pressure load is within an allowable value, the natural frequency is detuned by a predetermined ratio or more with respect to an integral multiple of the excitation frequency, and the stress of each part when a predetermined load is applied Find the shape whose value is below a predetermined threshold,
The optimization analysis step is repeated until it is determined that the optimum shape is processable in the processability determination step, and when the optimum shape is determined to be processable in the processability determination step, A detailed analysis process is performed .

The invention according to claim 2 is a method of designing an equipment suspension member according to claim 1,
The determination condition of the process availability determination step is included in the optimization condition of the optimization analysis step.

The invention according to claim 3 is the design method of the equipment suspension member according to claim 1 or 2 ,
In the optimization analysis step, a portion that can set an opening that penetrates in the thickness direction is obtained as a portion that can reduce rigidity, and the optimum shape having the opening is derived. And

According to the present invention, when the optimum shape of the equipment suspension member is derived as satisfying the predetermined optimization condition, and it is determined that the optimum shape can be processed by the predetermined processing facility, Detailed analysis is performed.
Thereby, even if it is determined that the machining is difficult, it is sufficient to perform the optimization analysis again, and it is not necessary to repeat the detailed analysis. Therefore, reworking of the design can be suppressed as compared with the conventional case.

It is a front view of the helicopter carrying the equipment suspension member. It is a front view of an equipment suspension member. It is a flowchart which shows the flow of the design method of an equipment suspension member. It is a flowchart which shows the flow of the detailed analysis among the design methods of an equipment suspension member. It is a front view of the helicopter carrying the equipment suspension member of a modification.

  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 (rotary wing machine) 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 body 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 formed of a long metal plate whose thickness direction is along the longitudinal direction of the helicopter H (the vertical direction in the drawing in FIG. 1), and from the lower end to the side along the fuselage side of the helicopter H. It curves upward while facing it, and its upper end is formed in a shape extending toward the side.
In FIG. 1, only a schematic mounting state of the equipment suspension member 1 is illustrated, and a detailed mounting state to the helicopter H and an interface member 2 to be described below for mounting the equipment E are omitted. .

Specifically, as shown in FIG. 2, the equipment suspension member 1 is formed so that the width gradually increases from the lower end of the curved portion toward the upper end, and the lower end and the middle height of the curved portion. The attachment part 11 is provided in each part.
These attachment parts 11 are parts attached to the helicopter H, and are formed in shapes extending from the curved part 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 that penetrates in the thickness direction. A fixing portion of the helicopter H is provided in the U-shaped opening. In a state of being sandwiched, a fixing pin is inserted into the through-hole 11a together with the fixing portion, thereby being fixed to the body of the helicopter H.

  The upper end portion of the equipment suspension member 1 is a suspension section 12 on which the equipment E is suspended. Specifically, the suspension member 12 is configured such that 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 this embodiment) openings 13,... Penetrating in the thickness direction. The plurality of openings 13,... Are provided to reduce weight and air resistance, and are formed in positions and shapes having no problem in 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 a flow of a suspension member design method, and FIG. 4 is a flowchart showing a detailed analysis flow described later in the suspension member design method.

As shown in FIG. 3, in the suspension member design method according to the present embodiment, the designer first sets a base model (base shape) of the equipment suspension member 1 that is a design target (step S1).
This base model has a flat plate shape without an opening 13, and is selected based on, for example, a conventional equipment suspension member or a helicopter H body shape (side surface shape or fixed portion position). It is set automatically.

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

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

Next, the designer performs an optimization analysis for optimizing the structure of the design region set in step S3 (step S4).
In this optimization analysis, an optimum shape of the equipment suspension member 1 that satisfies predetermined optimization conditions and constraint conditions is derived. The optimization condition is to minimize the mass density (ie, the lightest weight) while keeping the stress value of each part under the maximum assumed load (weight of equipment E, load due to wind pressure, etc.) below a predetermined threshold value. ) Further, the constraint condition is that the displacement with respect to each load is limited. The optimization condition or constraint condition may include a condition related to 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, a portion that can be the opening portion 13 is obtained as a portion having no problem even if the rigidity is low, and an optimum shape including the plurality of opening portions 13 is derived.

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

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

When it is determined in step S5 that the optimum shape is workable (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 as to whether the optimum shape is satisfied, and the shape is corrected as necessary.
In the following description, “equipment suspension member 1” refers to a shape that is optimal at that time unless otherwise specified. Point to.

Specifically, in the detailed analysis, as shown in FIG. 4, the designer first calculates the wind pressure load that the equipment suspension member 1 exerts on the body 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 fuselage flew at a predetermined speed, the wind of the predetermined wind speed was 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). If the designer determines that the wind pressure load exceeds the allowable value (step S62; No), the wind pressure is determined. After appropriately correcting the shape (mainly the shape of the opening 13) to suppress the load (step S63), the process proceeds to step S61 described above, and the wind pressure load is recalculated.

In Step S62, when it is determined that the calculated wind pressure load is within the allowable value (Step S62; Yes), the designer performs vibration analysis of the equipment suspension member 1 (Step S64).
Specifically, in this step, 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 integer multiple of the excitation frequency of the helicopter H rotor. Determination is made (step S65).
If it is determined that the natural frequency of the equipment suspension member 1 is not sufficiently separated from the integral multiple of the excitation frequency (step S65; No), the designer determines the natural frequency from the excitation frequency. After appropriately modifying the shape of the equipment suspension member 1 to detune (step S63), the process proceeds to step S61 described above.
In this step, it is more preferable to confirm the detuning from the generation frequency of the Karman vortex generated in the wake of the equipment suspension member 1.

Further, when it is determined in step S65 that the natural frequency of the equipment suspension member 1 is sufficiently separated from the integer multiple of the excitation frequency (step S65; Yes), the designer defines the equipment suspension member. 1 is analyzed (step S66).
Specifically, in this step, the stress value of each part when the assumed maximum load (the weight of the equipment E, the load due to the 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 determines that the stress value exceeds the allowable value (step S67; No). ) After appropriately correcting the shape to suppress the stress value (step S63), 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 allowable 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 the weight of the equipment suspension member 1 is sufficient, that is, whether the equipment suspension member 1 is not more than a predetermined weight. If it is determined that the weight reduction is not sufficient (step S7) (step S7; No), the process proceeds to step S2.
If it is determined in step S7 that the equipment suspension member 1 is sufficiently lightened (step S7; Yes), the designer sets the shape of the equipment suspension member 1 to the final shape, Finish the design.

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

  In addition, when the processability determination condition is included in the optimization condition of the optimization analysis, the processability determination process itself is not necessary, and the rework of the design can be suppressed.

  The embodiments to which the present invention can be applied are not limited to the above-described embodiments, 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. However, the shape of the equipment suspension member according to the present invention is not limited to this, for example, FIG. Like the equipment suspension member 1 </ b> A shown in FIG.

  The equipment suspension member according to the present invention is not limited to a helicopter as long as it is mounted on an aircraft, and can be applied to, for example, an unmanned aircraft.

DESCRIPTION OF SYMBOLS 1 Equipment suspension member 11 Attachment part 11a Through-hole 12 Suspension part 13 Opening part E Equipment H Helicopter

Claims (3)

A design method for an equipment suspension member for designing the shape of a flat equipment suspension member mounted outside an aircraft,
An optimization analysis step for deriving an optimal shape of the equipment suspension member that satisfies a predetermined optimization condition;
A workability determination step for determining whether or not the optimum shape derived in the optimization analysis step can be processed with a predetermined processing facility,
A detailed analysis step for performing detailed analysis on the optimum shape;
Equipped with a,
The optimization condition is to minimize the mass density while setting the stress value of each part when a predetermined load is applied to a predetermined threshold value or less,
In the detailed analysis step, the wind pressure load is within an allowable value, the natural frequency is detuned by a predetermined ratio or more with respect to an integral multiple of the excitation frequency, and the stress of each part when a predetermined load is applied Find a shape whose value is below a predetermined threshold,
The optimization analysis step is repeated until it is determined that the optimum shape is processable in the processability determination step, and when the optimum shape is determined to be processable in the processability determination step, A design method for an equipment suspension member characterized by performing a detailed analysis process .   The method for designing an equipment suspension member according to claim 1, wherein the determination condition of the processability determination step is included in the optimization condition of the optimization analysis step. In the optimization analysis step, a portion that can set an opening that penetrates in the thickness direction is obtained as a portion that can reduce rigidity, and the optimum shape having the opening is derived. The design method of the equipment suspension member according to claim 1 or 2 .

Images