CN111859564A - A design method of hydraulic buffer structure under heavy load impact - Google Patents

Abstract

The invention provides a method for designing a hydraulic buffer structure under heavy load impact, which comprises the steps of firstly segmenting a control rod and determining a variable to be designed; secondly, solving the diameter derivative of the middle section of the control rod; then obtaining a control rod outer contour shape function; then calculating a hydraulic resistance curve; then calculating the fullness of the hydraulic resistance curve according to the expected hydraulic resistance curve and the designed hydraulic resistance curve; calculating the smoothness of the hydraulic resistance curve; establishing a mathematical model of a hydraulic buffer structure design; and finally, solving the mathematical model obtained in the step 7 through an optimization algorithm to obtain the variable value of the design parameter. The hydraulic buffer device designed according to the invention can achieve a good buffer effect under heavy load impact, and meanwhile, the service life of the hydraulic buffer device is prolonged.

Description

A design method of hydraulic buffer structure under heavy load impact

technical field

The invention belongs to the field of hydraulic buffer structure design, in particular to a hydraulic buffer structure design method under heavy load impact.

Background technique

In engineering, the hydraulic buffer structure is widely used in the fields of automobile, high-speed rail, aerospace, lifting and transportation, high-speed test recovery and so on. In the actual working process of the project, there are often shocks and collisions. If no buffer is added, the working process will be unstable and the mechanism will be easily damaged. The introduction of a buffer structure can prevent hard collisions during work. Especially for special working conditions such as heavy load impact, hydraulic buffer structure needs to be designed. Otherwise, not only the expected buffering effect cannot be achieved, but the hydraulic resistance generated by the hydraulic buffering device will also have adverse effects on the buffering device itself, such as impact. Therefore, the rational design of the hydraulic buffer structure is of great significance to the buffering in the project.

The current hydraulic buffer structure is shown in Figure 1, and the purpose of controlling the changing law of hydraulic resistance is achieved by designing the outer contour shape of the control rod. The outer contour of the control rod that is widely used at present is a segmented linear shape, and the connection between the segments is not smooth. Under the impact of heavy load, when the liquid flows through the uneven part of the control rod at high speed, it will have adverse effects such as impact on the control rod. Long-term use will not only cause the buffer failure, but also lead to damage to the hydraulic buffer device.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a method for designing a hydraulic buffer structure under heavy load impact, which can achieve the purpose of controlling the variation law of hydraulic resistance during the buffering process by designing the shape of the control rod.

The technical solution that realizes the object of the present invention is:

A hydraulic buffer structure design method under heavy load impact, comprising the following steps:

Step 1. Segment the control rod to determine the variables to be designed;

Step 2. Solve the derivative of the diameter of the middle section of the control rod;

Step 3. Obtain the outer contour shape function of the control rod;

Step 4. Calculate the hydraulic resistance curve;

Step 5. Calculate the fullness of the hydraulic resistance curve according to the expected hydraulic resistance curve and the designed hydraulic resistance curve;

Step 6. Calculate the smoothness of the hydraulic resistance curve;

Step 7. Establish a mathematical model for hydraulic buffer structure design;

Step 8: Solve the mathematical model obtained in Step 7 through an optimization algorithm to obtain the design parameter variable values.

Compared with the prior art, the present invention has the following significant advantages:

(1) By designing the outer contour curve shape of the control rod, the hydraulic resistance work during the buffering process is consistent with the expected work, and at the same time, the adverse effects such as sudden changes, discontinuities, and oscillations in the hydraulic resistance change process are alleviated. good buffering effect;

(2) The contour curve of the control rod is in the shape of a segmented cubic spline, and the segments are smoothly connected, which ensures that the control rod will not have adverse effects such as impact during the liquid flow process, and improves the service life of the hydraulic buffer device.

Description of drawings

Fig. 1 is the flow chart of the design method of the present invention.

Figure 2 is a schematic diagram of the hydraulic buffer structure.

Figure 3 shows the hydraulic resistance curve.

Detailed ways

The present invention will be further introduced below in conjunction with the accompanying drawings.

2, based on a typical hydraulic buffer device, the hydraulic buffer device includes: a static chamber 3, a movement chamber 4 arranged in the static chamber 3, a control rod 5 arranged in the movement chamber 4; the rear end of the control rod 5 Two first liquid flow holes 1 are provided, and two second liquid flow holes 2 are provided at the front end; during the buffering process, the moving cavity moves along the x-axis direction in Figure 2, and the static cavity and the control rod remain stationary. The fluid flows into the left side of the moving chamber and the right side of the static chamber through the first liquid flow hole 1 and the second liquid flow hole 2 respectively, and hydraulic resistance is generated in this process.

The design method of the hydraulic buffer structure under heavy load impact of the present invention achieves the purpose of controlling the variation law of hydraulic resistance during the buffering process by designing the shape of the control rod; with reference to Figure 1, the specific design process includes the following steps:

Step 1. Divide the control rod into sections and determine the variables to be designed:

The coordinate system is established with the axis of the control rod as the x-axis, as shown in Figure 2, and the total length L of the control rod is set. Take n+1 points on the control rod to divide the control rod into n segments, the position coordinate of the i+1th point is x _i (0≤x _i ≤L, i=0,1,2,...,n), Each contour is designed in the form of a cubic spline. At the position _xi on the control rod, the diameter of the control rod section is _yi , and the derivative of the diameter of the control rod section is _mi . Among them: y ₀ , y ₁ ,…y _n , m ₀ , m _n are the parameters to be designed, a total of n+3.

Step 2. Solve the derivative of the diameter of the middle section of the control rod:

The diameter derivatives m ₁ ,m ₂ ,…m _n-1 of the middle section of the control rod are obtained by solving the following matrix equations:

表示后长度比，

表示前长度比，

表示组合差商，h_i＝x_i-x_i-1表示控制杆第i段长度，(i＝1,2,…,n-1)。In the above formula:

represents the rear length ratio,

represents the front length ratio,

Represents the combined difference quotient, hi =x _i -x _i-1 represents the length of the _i -th segment of the control rod, (i=1,2,...,n-1).

Step 3. Obtain the shape function of the outer contour of the control rod:

The control rod diameter function is expressed as:

Among them, x represents the coordinate position of any point on the control rod, and the form of each cubic spline function is:

Step 4. Calculate the hydraulic resistance curve:

In Figure 2: the inner diameter of the static cavity is D _T , the outer diameter of the moving cavity is d _T , and A ₀ represents the working area of the piston (the inner diameter cross-sectional area of the static cavity minus the outer diameter cross-sectional area of the moving cavity); the inner diameter of the moving cavity is d _j , the inner diameter cross-sectional area of the motion chamber is A _j ; the diameter of the right ring of the motion chamber is d _p , and the cross-sectional area of the right ring of the motion chamber is _Ap ; the diameter of any cross-section of the control rod is y(x), and the cross-sectional area of any cross-section of the control rod is A _x ; the liquid density is ρ; during the buffering process, the hydraulic resistance coefficient of the liquid in the static cavity flowing through the No. 2 hole in Figure 2 is K ₂ , and the minimum cross-sectional area it passes through is A ₁ ; The liquid flows through No. 1 in Figure 2 The hydraulic resistance coefficient of the hole is K ₁ . Calculate the hydraulic resistance f according to the above parameters:

表示运动腔运动速度。根据运动关系：x＝x(t)，最终可把液压阻力表示为随时间变化的函数：In the formula: t represents the movement time of the movement cavity;

Indicates the motion speed of the motion chamber. According to the motion relationship: x=x(t), the hydraulic resistance can finally be expressed as a function of time:

The curve of hydraulic resistance changing with time is called hydraulic resistance curve.

Step 5. Calculate the fullness of the hydraulic resistance curve according to the expected hydraulic resistance curve and the designed hydraulic resistance curve:

Assuming the expected hydraulic resistance curve F ₀ and the designed hydraulic resistance curve F ₁ , as shown in Figure 3, calculate the fullness of the hydraulic resistance curve:

Step 6. Calculate the smoothness of the hydraulic resistance curve:

Select the points on the hydraulic resistance curve corresponding to the connection of each segment of the control rod, and calculate the smoothness of the hydraulic resistance curve:

Step 7. Establish the mathematical model of hydraulic buffer structure design:

Based on step 1-step 6, the mathematical model of hydraulic buffer structure design is obtained:

Among them: "min" indicates the minimum value, "model" indicates the model, "s.t." indicates the constraints, eps indicates the given threshold, "Var" indicates the variable to be sought, and V indicates the parameter vector to be designed.

Step 8. Solve the mathematical model obtained in step 7 through the optimization algorithm, and obtain the design parameter variable value:

The invention adopts the method of genetic algorithm combined with sequence quadratic programming to solve the mathematical model of hydraulic buffer structure design, so as to satisfy the purpose of global search and local fine solution. First, the genetic algorithm is used to solve the problem, and the calculated result is used as the initial value, and the final solution is obtained by using the sequential quadratic programming method.

The contour curve of the control rod designed through the above steps is in the shape of a piecewise cubic spline, and the smooth connection between the segments ensures that the control rod will not have adverse effects such as impact on the control rod during the liquid flow process, and reduces the sudden change in the hydraulic resistance change process. , discontinuity, oscillation and other adverse effects. It can improve the service life of the hydraulic buffer device, and at the same time, it can play a good buffer effect under heavy load impact.

Claims (9)

1. A method for designing a hydraulic buffer structure under heavy load impact is characterized by comprising the following steps:

step 1, segmenting a control rod, and determining a variable to be designed;

step 2, solving the diameter derivative of the middle section of the control rod;

step 3, obtaining an outer contour shape function of the control rod;

step 4, calculating a hydraulic resistance curve;

step 5, calculating the fullness of the hydraulic resistance curve according to the expected hydraulic resistance curve and the designed hydraulic resistance curve;

step 6, calculating the smoothness of the hydraulic resistance curve;

step 7, establishing a mathematical model of the hydraulic buffer structure design;

and 8, solving the mathematical model obtained in the step 7 through an optimization algorithm to obtain the variable value of the design parameter.

2. The design method of a hydraulic buffer structure under heavy load impact according to claim 1, characterized in that the control rod is divided into n sections by taking n +1 points on the control rod, and the position coordinate of the (i + 1) th point is x_i(0≤x_iL, i is equal to or less than 0,1,2, …, n), and each section of contour is designed into a cubic spline curve form; position x on the control rod_iWhere the cross-sectional diameter of the control rod is y_iThe derivative of the cross-sectional diameter of the control rod is m_i(ii) a Wherein: y is₀,y₁,…y_n,m₀,m_nThe number of the design parameters is n + 3.

3. The design method of a hydraulic buffer structure under heavy load impact according to claim 1, characterized in that the derivative m of the intermediate section diameter is obtained by solving the following matrix equation ₁,m₂,…m_n-1：

It is composed of

The ratio of the lengths after the representation,

it is shown that the ratio of the front length,

represents the combined difference quotient, h_i＝x_i-x_i-1Represents a position difference; x is the number of_iIndicating the i-th position on the control lever, y_iIndicating the diameter of the ith position on the control lever.

4. The method for designing a hydraulic buffer structure under heavy load impact according to claim 2, wherein the form of each section of cubic spline function of the control rod in the step 3 is as follows:

5. the method for designing the hydraulic buffer structure under the heavy load impact according to claim 1, wherein a hydraulic resistance curve F (t) is calculated, and the change relation of the hydraulic damping force f along with the time t is as follows:

wherein: d_TIs the inner diameter of the static chamber, d_TTo the outer diameter of the motion lumen, A₀Representing the piston working area; d_jTo the inner diameter of the motion lumen, A_jIs the inner diameter section area of the motion cavity; d_pTo the diameter of the right side ring of the motion chamber, A_pIs a movementThe cross-sectional area of the right side ring of the cavity; y (x) is the arbitrary cross-sectional diameter of the control rod, A_xThe cross section area of any section of the control rod is; k₂In order to buffer the hydraulic resistance coefficient of the liquid in the static cavity flowing through the liquid flow hole at the front end of the control rod, A₁Is the minimum cross-sectional area of the pass; k₁The hydraulic resistance coefficient of the liquid flowing through the liquid flowing hole at the rear end of the control rod is shown; t represents the motion time of the motion cavity,

representing the speed of movement of the moving cavity.

6. The method for designing a hydraulic cushion structure under heavy load impact according to claim 1, wherein the hydraulic resistance curve fullness is calculated from the expected hydraulic resistance curve and the designed hydraulic resistance curve:

wherein F₀For the hydraulic resistance curve desired, F₁The hydraulic resistance curve is obtained for the design.

7. The design method of the hydraulic buffer structure under heavy load impact according to claim 1, characterized in that points on the hydraulic resistance curve corresponding to the joints of the segments of the control rod are selected to calculate the smoothness of the hydraulic resistance curve:

8. the method for designing a hydraulic buffer structure under heavy load impact according to claim 1, wherein a mathematical model of the design of the hydraulic buffer structure is obtained:

wherein: min represents the minimum value, model represents the model, s.t. represents the constraint condition, eps is a given threshold value, "Var" represents the variable to be solved, and V represents the parameter vector to be designed.

9. The method for designing the hydraulic buffer structure under the heavy load impact according to claim 1, wherein a mathematical model for designing the hydraulic buffer structure is solved by adopting a genetic algorithm combined with a sequence quadratic programming method.

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