Instability control method for coal mine underground suspended roof fracturing mechanism

Abstract

A method for controlling instability of a suspended roof fracturing mechanism in coal mines is disclosed. The suspended roof fracturing mechanism includes a static platform, a dynamic platform, a first telescopic component, a second telescopic component, a third telescopic component, a central support column, and a roof-breaking column. The lower end of the central support column is connected to the static platform by a first ball joint, and the roof-breaking column is installed at the upper end of the central support column. The dynamic platform is fixedly connected to the upper end of the central support column. The first, second, and third telescopic components are arranged circumferentially along the central support column. A coordinate system is created on the static platform, with the first ball joint as the origin. The lengths of the first, second, and third telescopic components are: , ...

Description

Technical Field

[0001] This invention relates to the field of underground roof breaking technology in coal mines, and in particular to a method for controlling the instability of an underground suspended roof fracturing mechanism in coal mines. Background Technology

[0002] In fully mechanized coal mining faces, the roof of the goaf in the roadway is generally supported by active methods such as anchor bolts and cables, tightly anchoring the immediate roof and the main roof into a unified load-bearing structure. This makes it difficult for the roof of the goaf behind to collapse naturally and in a timely manner as the working face advances, resulting in a large-scale, high-strength, long overhanging roof structure. Existing techniques for inducing overhanging roof collapse, such as manual anchor unwinding, hydraulic fracturing, and blasting weakening, generally suffer from significant problems such as high randomness in the collapse range and difficulty in precisely controlling the timing of collapse, posing a great threat to safe production.

[0003] Due to its simple structure and flexible movement, the S / 3-SPS parallel mechanism is widely used for attitude adjustment and positioning operations. A top plate cracking mechanism based on the 3SPS-S parallel mechanism was designed. For example, patent CN103056869A discloses an S / 3-SPS attitude adjustment and positioning three-axis drive parallel mechanism. This mechanism uses three SPS branches and a central ball joint branch chain. By controlling the lengths of the three prismatic joints, it achieves multi-degree-of-freedom motion of the upper platform, aiming to expand the robot's attitude working range.

[0004] However, existing research and applications of S / 3-SPS parallel mechanisms mainly focus on robot operating environments with no impact or small loads. In such applications, the three SPS branches are usually allowed to be non-coplanar, and even actively pursued to expand the attitude space. Non-coplanarity does not lead to mechanism instability or serious consequences; therefore, there is no technical motivation to force the SPS branches to be coplanar in existing technologies, nor are there quantitative analyses and control strategies for instability conditions.

[0005] In contrast, underground roof-fracturing mechanisms in coal mines must withstand strong impact loads during operation, such as the impact force at the moment of roof breaching, which places extremely high demands on the stability of the mechanism. Studies have shown that... (See...) Figure 2 When the three SPS branches are not coplanar, the mechanism is prone to instability under impact loads, which manifests as loss of attitude control, overturning, or even structural damage, seriously affecting operational safety. Summary of the Invention

[0006] In view of this, and to address the above-mentioned shortcomings, it is necessary to propose a method for controlling the instability of the roof-suspended fracturing mechanism in underground coal mines.

[0007] A method for controlling the instability of a suspended roof fracturing mechanism in a coal mine, the suspended roof fracturing mechanism comprising a static platform, a dynamic platform, a first telescopic member, a second telescopic member, a third telescopic member, a central support column, and a roof-breaking column. The lower end of the central support column is connected to the static platform by a first ball joint, and the roof-breaking column is installed at the upper end of the central support column. The dynamic platform is fixedly connected to the upper end of the central support column. The first, second, and third telescopic members are arranged circumferentially along the central support column. The telescopic end of the first telescopic member is connected to the dynamic platform by a second ball joint, and the fixed end of the first telescopic member is connected to the static platform by a fifth ball joint. The telescopic end of the second telescopic member is connected to the dynamic platform by a third ball joint, and the fixed end of the first telescopic member is connected to the static platform by a sixth ball joint. The telescopic end of the third telescopic member is connected to the dynamic platform by a fourth ball joint, and the fixed end of the third telescopic member is connected to the static platform by a seventh ball joint. A coordinate system is created on the static platform, with the first ball joint as the origin. The length of the first telescopic member is... The length of the second telescopic component is The length of the third telescopic component is ,control , , Satisfying Constraint Model:

[0008] ,

[0009] ,

[0010] ,

[0011] in: The point is the connection point between the moving platform and the central support column, and the second, third, and fourth ball joints are connected to... The distance between the points is The distances from the fifth, sixth, and seventh ball joints to the first ball joint are all... The length of the central support pillar is The coordinates of the point , , .

[0012] Preferably, the second, third, and fourth ball joints are the three vertices of an isosceles right triangle.

[0013] Preferably, the fifth, sixth, and seventh ball joints are the three vertices of an isosceles right triangle.

[0014] Preferably, the roof-breaking column includes a fourth telescopic member and a roof-breaking cone. The fixed end of the fourth telescopic member is connected to the upper end of the central support column, the central support column is coaxially connected to the fourth telescopic member, and the telescopic end of the fourth telescopic member is equipped with the roof-breaking cone.

[0015] Preferably, the top-piercing cone is used to penetrate the suspended ceiling.

[0016] Preferably, the fourth telescopic component is a jack.

[0017] Preferably, the first telescopic component, the second telescopic component, and the third telescopic component are jacks.

[0018] Preferably, , , .

[0019] Preferably, =450mm, =450mm, h=900mm.

[0020] Preferably, =301mm, =395mm, h=1180mm.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] By adjusting , , ,control , , By satisfying the constraint model, at least the first and second telescopic components among the first, second, and third telescopic components always remain coplanar, effectively preventing mechanism instability and providing reliable safety assurance for downhole roof-suspended fracturing operations. Attached Figure Description

[0023] Figure 1 This is an isometric view of the suspended crack-inducing mechanism in a stable state.

[0024] Figure 2 This is an isometric view of the suspended crack-causing mechanism in an unstable state.

[0025] In the diagram: static platform 10, moving platform 20, telescopic component 30, central support column 40, and roof-breaking column 50. Detailed Implementation

[0026] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] See Figure 1 , Figure 2 This invention provides a method for controlling the instability of a suspended roof fracturing mechanism in coal mines. The suspended roof fracturing mechanism includes a static platform 10, a dynamic platform 20, a first telescopic member 30, a second telescopic member 30, a third telescopic member 30, a central support column 40, and a roof-breaking column 50. The lower end of the central support column 40 is connected to the static platform 10 by a first ball joint, and the roof-breaking column 50 is installed on the upper end of the central support column 40. The dynamic platform 20 is fixedly connected to the upper end of the central support column 40. The first telescopic member 30, the second telescopic member 30, and the third telescopic member 30 are arranged circumferentially along the central support column 40. The telescopic end of the first telescopic member 30 is connected to the moving platform 20 by a second ball joint; the fixed end of the first telescopic member 30 is connected to the stationary platform 10 by a fifth ball joint; the telescopic end of the second telescopic member 30 is connected to the moving platform 20 by a third ball joint; the fixed end of the first telescopic member 30 is connected to the stationary platform 10 by a sixth ball joint; the telescopic end of the third telescopic member 30 is connected to the moving platform 20 by a fourth ball joint; and the fixed end of the third telescopic member 30 is connected to the stationary platform 10 by a seventh ball joint. A coordinate system is created on the stationary platform 10, with the first ball joint as the origin. The length of the first telescopic member 30 is... The length of the second telescopic component 30 is The length of the third telescopic component 30 is ,control , , Satisfying Constraint Model:

[0028] ,

[0029] ,

[0030] ,

[0031] in: The point is the connection point between the moving platform 20 and the central support column 40, and the second ball joint, third ball joint, and fourth ball joint are connected to... The distance between the points is The distances from the fifth, sixth, and seventh ball joints to the first ball joint are all... The length of the central support pillar 40 is , coordinates of the point , , .

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] By adjusting , , ,control , , By satisfying the constraint model, at least the first telescopic component 30 and the second telescopic component 30 among the first telescopic component 30 and the third telescopic component 30 always remain coplanar, effectively avoiding mechanism instability and providing reliable safety assurance for downhole roof-suspended fracturing operations.

[0034] See Figure 1 , Figure 2 Furthermore, the second, third, and fourth ball joints are the three vertices of an isosceles right triangle.

[0035] See Figure 1 , Figure 2 Furthermore, the fifth, sixth, and seventh ball joints are the three vertices of an isosceles right triangle.

[0036] See Figure 1 , Figure 2 Furthermore, the top-breaking column 50 includes a fourth telescopic member 30 and a top-breaking cone. The fixed end of the fourth telescopic member 30 is connected to the upper end of the central support column 40. The central support column 40 and the fourth telescopic member 30 are coaxially connected. The telescopic end of the fourth telescopic member 30 is equipped with a top-breaking cone.

[0037] See Figure 1 , Figure 2 Furthermore, the top-piercing cone is used to penetrate the suspended ceiling.

[0038] See Figure 1 , Figure 2 Furthermore, the fourth telescopic component 30 is a jack.

[0039] See Figure 1 , Figure 2 Furthermore, the first telescopic component 30, the second telescopic component 30, and the third telescopic component 30 are jacks.

[0040] Constraint model derivation:

[0041] Step 1: Create a static coordinate system O-XYZ on the static platform 10, with the direction of the central support 40 as the Z-axis. The center point of the fifth, sixth, and seventh ball joints connecting the first, second, and third telescopic components 30 to the static platform 10 is A. i (i=1,2,3), the center point of the second, third, and fourth ball joints connected to the moving platform 20 is B. i(i=1,2,3), the center point of the first ball joint is P, A i and B i The figure formed by the connection is an isosceles right triangle, point Q is the free end of the top-breaking column 50, PM = Points P, M, and Q are collinear. Let A be the collinear point. i = B i = , coordinates of the point , , Point P has coordinates (0, 0, 0), and points A0, A1, and A2 are fixed.

[0042] Step 2: ψ is the rotation angle of the moving platform 20 about the PM axis, rotation matrix R(θ, φ, ψ), B i The coordinates in the static coordinate system are: , Rotation matrix The Line number Column elements;

[0043] Step 3: A0, A1, B0, and B1 are coplanar. cosθ≈1, Substitute the constraint relationship obtained in step three into the coordinate expression in step two and rearrange it to obtain the expression described in step four.

[0044] Step 4: Inverse solution, ,

[0045] ,

[0046] ,

[0047] .

[0048] like Figure 2 As shown, when points A0, A1, B0, and B1 are not coplanar, interference will occur in the first expansion joint 30, causing the cracking mechanism to become unstable.

[0049] like Figure 1 As shown, to ensure that A0A1 and B0B1 lie in the same plane, the constraint model is as follows: , , The relationship between them only requires , , The constraint model is satisfied, with points A0, A1, B0, and B1 being coplanar, to prevent the fracturing mechanism from being in an unstable state.

[0050] The S / 3-SPS parallel mechanism, exemplified by patent CN103042521A, is primarily used for attitude adjustment and positioning operations in general industrial environments, where strong impact loads are absent. It aims for the largest possible workspace and motion flexibility, allowing and even actively pursuing non-coplanar states of the branches to expand the attitude range. Those skilled in the art have no incentive to study the instability of S / 3-SPS mechanisms under impact loads, let alone to actively restrict the degrees of freedom of the branches or impose coplanar constraints.

[0051] A review of existing S / 3-SPS related patents (such as CN103042521A and CN103056869A) reveals that their specifications all emphasize "expanding the attitude range," "increasing the workspace," and "improving flexibility," without ever mentioning "restricting branch degrees of freedom" or "forcing coplanarity." Patent CN103042521A sacrifices stability for a larger workspace. The control objective of this application is completely opposite to the prior art, actively sacrificing workspace for stability. The prior art provides a reverse teaching for this application.

[0052] In conventional control, to implement constraints, either over-driving or passive constraints are used. This application directly embeds constraints by changing the inverse solution expression itself, representing a fundamental breakthrough in conventional control.

[0053] See Figure 1 , Figure 2 ,further, , , .

[0054] Example 1: =450mm, =450mm, h=900mm.

[0055] Example 2: =301mm, =395mm, h=1180mm.

[0056] The following four indicators are defined for the fracturing mechanism: global motion performance index E, global motion performance fluctuation index σ, global operability index δ, and actual working space proximity index W. These four indicators are based on the quantitative calculation of the working space V of the fracturing mechanism. The working space V refers to the set of all spatial positions and attitudes that the fracturing mechanism Q point can reach.

[0057] Workspace V: The volume V of the reachable workspace of the fracturing mechanism is solved using the Monte Carlo method and the convex hull algorithm. The solution method is well known.

[0058] Global motion performance index E: k = 1 / K In the formula Jacobian matrix Maximum singular value, Jacobian matrix Minimum singular value.

[0059] Global motion performance fluctuation index σ: .

[0060] Overall operability index δ: , .

[0061] Actual workspace proximity index W: , H is the sum of the lengths of the top support column 50 and the central support column 40. For example, 30°.

[0062] Example 2 is the optimized result of Example 1. The optimization calculation process is as follows:

[0063] Step 1: Settings , , The range of values ​​for , 3 , ;

[0064] Step 2: Establish 4 sub-objective functions. , , , ,use Representing E, using To represent σ, use To represent δ, use W represents;

[0065] Step 3: Combining the reference target distance method and the linear weighting method, assuming that the four indicators are equally important, the weights are... Take 1 / 4 and construct the objective function model. In the formula Reference value for sub-objective function;

[0066] Step 4: Solve the model using a genetic algorithm. The optimization results are shown in Table 1.

[0067] Table 1. Optimization results of the genetic algorithm

[0068] Parameter Before optimization After optimization r A / mm]] 450 301 r B / mm]] 450 395 h / mm 900 1180 E 0.0674 0.1106 σ 0.0455 0.0442 δ 0.2822 0.4714 W 0.6398 0.9834

[0069] Compared to Example 1, Example 2 shows that, with a smaller change in the overall motion performance fluctuation index σ, the overall motion performance index E is improved by 64%, the overall operability index δ is improved by 67%, and the actual workspace proximity index W is improved by 53%, resulting in a significant improvement in multiple indicators through synergy.

[0070] There is an inherent contradiction among these four indicators. When studying S / 3-SPS mechanisms, those skilled in the art typically focus only on "expanding the attitude range" or "improving dexterity," without any motivation to simultaneously consider all four specific indicators, let alone address and resolve their contradictions. This is because only with a deep understanding of downhole roof-breaking conditions can these engineering requirements be translated into appropriate performance indicators. The optimization goal is no longer to maximize a single indicator, but rather for all indicators to simultaneously approach their respective ideal values. This approach is uncommon in the field of parallel mechanism optimization.

[0071] When faced with such an optimization problem, those skilled in the art need to understand both the characteristics of the problem and the features of the algorithm when choosing a genetic algorithm from among many optimization algorithms. If existing literature does not provide guidance on applying genetic algorithms to this specific four-indicator collaborative equilibrium optimization, then the choice itself constitutes part of the technical contribution.

[0072] The steps in the method of this invention can be adjusted, combined, or deleted according to actual needs.

[0073] The modules or units in the device of this invention can be merged, divided, or deleted according to actual needs.

[0074] The above-disclosed embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of the invention. Those skilled in the art will understand that implementing all or part of the above-described embodiments and making equivalent changes in accordance with the claims of the present invention are still within the scope of the invention.

Claims

1. A method for controlling the instability of a suspended roof fracturing mechanism in an underground coal mine, characterized in that: The suspended roof-crack mechanism includes a static platform, a dynamic platform, a first telescopic member, a second telescopic member, a third telescopic member, a central support column, and a roof-breaking column. The lower end of the central support column is connected to the static platform by a first ball joint, and the roof-breaking column is installed at the upper end of the central support column. The dynamic platform is fixedly connected to the upper end of the central support column. The first, second, and third telescopic members are arranged circumferentially along the central support column. The telescopic end of the first telescopic member is connected to the dynamic platform by a second ball joint, and the fixed end of the first telescopic member is connected to the static platform by a fifth ball joint. The telescopic end of the second telescopic member is connected to the dynamic platform by a third ball joint, and the fixed end of the first telescopic member is connected to the static platform by a sixth ball joint. The telescopic end of the third telescopic member is connected to the dynamic platform by a fourth ball joint, and the fixed end of the third telescopic member is connected to the static platform by a seventh ball joint. A coordinate system is created on the static platform, with the first ball joint as the origin. The length of the first telescopic member is... The length of the second telescopic component is The length of the third telescopic component is ,control , , Satisfying Constraint Model: ， ， ， in: The point is the connection point between the moving platform and the central support column, and the second, third, and fourth ball joints are connected to... The distance between the points is The distances from the fifth, sixth, and seventh ball joints to the first ball joint are all... The length of the central support pillar is The coordinates of the point , , .

2. The method for controlling the instability of a suspended roof fracturing mechanism in coal mines as described in claim 1, characterized in that: The second, third, and fourth ball joints are the three vertices of an isosceles right triangle.

3. The method for controlling the instability of the suspended roof fracturing mechanism in coal mines as described in claim 1, characterized in that: The fifth, sixth, and seventh ball joints are the three vertices of an isosceles right triangle.

4. The method for controlling the instability of the suspended roof fracturing mechanism in coal mines as described in claim 1, characterized in that: The roof-breaking column includes a fourth telescopic component and a roof-breaking cone. The fixed end of the fourth telescopic component is connected to the upper end of the central support column. The central support column is coaxially connected to the fourth telescopic component. The telescopic end of the fourth telescopic component is equipped with the roof-breaking cone.

5. The method for controlling the instability of the suspended roof fracturing mechanism in coal mines as described in claim 4, characterized in that: The top-piercing cone is used to penetrate the suspended ceiling.

6. The method for controlling the instability of the suspended roof fracturing mechanism in coal mines as described in claim 4, characterized in that: The fourth telescopic component is a jack.

7. The method for controlling the instability of a suspended roof fracturing mechanism in coal mines as described in claim 1, characterized in that: The first, second, and third telescopic components are jacks.

8. The method for controlling the instability of a suspended roof fracturing mechanism in coal mines as described in claim 1, characterized in that: ， ， 。 9. The method for controlling the instability of a suspended roof fracturing mechanism in coal mines as described in claim 8, characterized in that: =450mm, =450mm,h=900mm。 10. The method for controlling the instability of a suspended roof fracturing mechanism in coal mines as described in claim 8, characterized in that: =301mm, =395mm,h=1180mm。

Images