Method for controlling meso-position function oil cylinder of six-axis horizontal machining center

Abstract

The invention relates to a six-axis horizontal machining center meso-position function oil cylinder control method which comprises the following steps: step 1, initializing the position of an oil cylinder piston rod, moving the position of the piston rod to a right limit position, constructing a moving path initial solution of a first piston, and taking the moving path initial solution as a current global optimal solution; 2, traversing the moving path of the piston rod, and calculating the moving distance of the first piston when the piston rod moves each time; 3, traversing the moving path of the piston rod, generating a current solution of the moving path of the first piston, and calculating a target function value of the current solution of the moving path of the first piston; 4, comparing the current solution of the moving path of the first piston with the current global optimal solution; and step 5, repeating the steps 2-4 until a termination condition is met, and finally returning the recorded global optimal solution. According to the method, the optimal moving path of the first piston is obtained through rapid solving, the moving distance of the first piston is shortest, abrasion of the first piston is reduced to the maximum extent, and the service life of the oil cylinder is prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of oil cylinder control, and in particular to a method for controlling a center-position oil cylinder of a six-axis horizontal machining center. Background Art

[0002] A cylinder, also known as a hydraulic cylinder, is a hydraulic actuator that converts hydraulic energy into mechanical energy. It is mainly used to achieve linear reciprocating motion or swinging motion. Conventional cylinders only have two extreme positions, left and right. When the system pressure is released, the cylinder piston will be in a free state, resulting in low stop position accuracy of the actuator, and a sense of impact when starting, and poor starting stability. Therefore, a cylinder with a neutral position function has been developed, such as Figure 1 shown.

[0003] The oil cylinder with a neutral position function comprises a cylinder body, a first piston and a second piston.

[0004] The cylinder body has a first piston accommodating chamber and a second piston accommodating chamber that are interconnected. The cylinder body includes a cylinder barrel, a left end cap, and a right end cap. A stepped through hole is axially opened in the middle of the cylinder barrel. The stepped through hole includes a first through hole section for forming the first piston accommodating chamber and a second through hole section for forming the second piston accommodating chamber. The left and right end caps are respectively mounted at both ends of the cylinder barrel. The left end cap covers the second through hole section, and the inner end surface of the left end cap forms a left extreme position limit surface. The right end cap covers the first through hole section, and the inner end surface of the right end cap forms a right extreme position limit surface. The inner diameter of the second through hole section is smaller than that of the first through hole section, and the first and second through hole sections cooperate to form an intermediate position limit step surface.

[0005] The first piston is movably arranged in the first piston accommodating chamber, and the outer wall of the first piston is sealed and connected to the inner wall of the first through-hole section. The second piston is movably arranged in the second piston accommodating chamber, and the outer wall of the second piston is sealed and connected to the inner wall of the second through-hole section. The first piston and the second piston separate the interior of the cylinder body into a first oil chamber, a second oil chamber and a third oil chamber. The first oil chamber is located on the side of the first piston away from the second piston, the second oil chamber is located between the first piston and the second piston, and the third oil chamber is located on the side of the second piston away from the first piston. Three oil inlets are opened on the cylinder body, namely a first oil inlet connected to the first oil chamber, a second oil inlet connected to the second oil chamber, and a third oil inlet connected to the third oil chamber. An intermediate push rod is provided between the first piston and the second piston, one end of the intermediate push rod is fixed to the first piston, and the other end extends into the second piston accommodating cavity. A piston rod is provided on the side of the second piston away from the first piston, one end of the piston rod is fixed to the second piston, and the other end extends out of the cylinder body through the through hole of the front end cover. The moving stroke of the first piston is smaller than the axial length of the intermediate push rod, and the sum of the moving stroke of the first piston and the axial length of the intermediate push rod is smaller than the moving stroke of the second piston.

[0006] This type of oil cylinder with a neutral position function is usually used in complex working conditions. The movement stroke of the cylinder piston rod is complex and diverse. Since the first piston and the second piston are designed separately, the piston rod needs to cooperate with the first piston when switching between the left extreme position, the middle position and the right extreme position. How to optimize the movement path of the first piston according to the required movement path of the piston rod, minimize the movement distance of the first piston as much as possible, and reduce the wear of the first piston is the difficulty of the automatic control of the oil cylinder.

[0007] Therefore, the present invention proposes a method for controlling a center-position hydraulic cylinder of a six-axis horizontal machining center to solve the above-mentioned problem. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a method for controlling the center functional cylinder of a six-axis horizontal machining center, which can quickly solve and obtain the optimal first piston movement path, shorten the first piston movement distance, minimize the wear of the first piston, and extend the service life of the cylinder.

[0009] In order to solve the above technical problems, the technical solution of the present invention is as follows: a method for controlling a center-position function oil cylinder of a six-axis horizontal machining center, the oil cylinder with a center-position function includes a cylinder body, a first piston and a second piston, the cylinder body has a first piston accommodating chamber and a second piston accommodating chamber that are interconnected, an intermediate position limiting step surface is formed between the first piston accommodating chamber and the second piston accommodating chamber, the first piston accommodating chamber has a right extreme position limiting surface on the side away from the second piston accommodating chamber, and the second piston accommodating chamber has a left extreme position limiting surface on the side away from the first piston accommodating chamber, the first piston and the second piston are movably arranged in the first piston accommodating chamber and the second piston accommodating chamber respectively, and the cylinder body is divided into three oil chambers with oil inlets, the first piston has an intermediate push rod on the side close to the second piston, and the second piston has a piston rod on the side away from the first piston, the moving stroke of the first piston is less than the axial length of the intermediate push rod, and the sum of the moving stroke of the first piston and the axial length of the intermediate push rod is less than the moving stroke of the second piston, its innovation lies in: the control method includes the following steps: Step 1: Initialize the position of the cylinder piston rod and move the piston rod to the right limit position d 00 , construct the initial solution S0 of the movement path of the first piston, and use S0 as the current global optimal solution S * ; Step 2: The required moving path of the piston rod is V={N01, N02.....N0 n}, traverse the piston rod movement path, if the constraints are met, select the movement stop position of the first piston each time the piston rod moves according to the constraints. If the constraints are not met, randomly select the movement stop position of the first piston and calculate the movement distance of the first piston each time the piston rod moves , the calculation formula is as follows: ; in, Indicates the moving stop position of the first piston when the piston rod stops for the i-th time, Indicates the movement stop position of the first piston when the piston rod stops moving for the i-1th time; Step 3: traverse the piston rod movement path, generate the current solution S of the movement path of the first piston, and calculate the objective function value of the current solution S of the movement path of the first piston , the calculation formula is: ; Step 4: Compare the current solution S of the first piston's moving path with the current global optimal solution S * Compare, if the current solution S is better than the current global best solution S * ,Right now < , then update S*; Step 5: Repeat steps 2-4 until the termination condition is met, and finally return the recorded global optimal solution S*.

[0010] Furthermore, the control method includes the following definitions: The cluster N1 of the first piston movement stop position = {d 10 ,d 11}, wherein when the first piston is against the right limit position limit surface, the first piston is at position d 10 When the first piston is against the intermediate position limit step surface, the first piston is at position d 11 ; The cluster N2 of the second piston movement stop position = {d 20 ,d 21 ,d 22}, wherein when the first piston is against the right limit position limit surface and the second piston is against the end of the middle push rod, the second piston is in position d 20 When the first piston is against the intermediate position limit step surface and the second piston is against the end of the intermediate push rod, the second piston is in position d 21 When the second piston is against the left limit position limit surface, the second piston is at position d 22 ; The piston rod movement stop position cluster N0={d 00 ,d 01 ,d 02}, where d 00 ,d 01 ,d 02 Corresponding to the right limit position, the middle position and the left limit position respectively, the movement path of the piston rod n times is V={N01, N02.....N0n}, the moving stop position N0 of the piston rod after the i-th movement i ={N1 i , N2 i},N0 i ∈N0, i∈N, N={1,2,.......,n}, n is the total number of piston rod movements, N1 i ∈N1,N2 i Indicates the second piston movement stop position corresponding to the piston rod's i-th movement stop, N2 i ∈N2.

[0011] Furthermore, when the initial solution S0 of the movement path of the first piston is constructed in step 1, the piston rod movement path V={N01, N02.....N0 n If the constraints are met, the first piston's moving stop position is selected according to the constraints. If the constraints are not met, the first piston's moving stop position is randomly selected. After the piston rod moving path is traversed, an initial solution of the first piston's moving path S0 = {N11, N12.....N1 n}.

[0012] Furthermore, the constraints include: The i-th moving stop position of the piston rod N0 i The following constraints exist: Constraint 1: If N0 i =d 00 , then N2 i =d 20 , and N1 i =d 10 ; Constraint 2: If N0 i =d 01 , then N2 i =d 21 , and N1 i =d 11 ; Constraint 3: If N0 i =d 02 , then N2 i =d 22 ; The following constraints exist during the movement of the piston rod: Constraint 4: If N0 i-1 =d 00 , N0 i =d 02 And N0 i+1 =d 00 When N1i =d 10 ; Constraint 5: If N0 i-1 =d 00 , N0 i =d 02 And N0 i+1 =d 01 When N1 i =d 11 ; Constraint 6: If N0 i-1 =d 01 , N0 i =d 02 And N0 i+1 =d 00 When N1 i =d 10 ; Constraint 7: If N0 i-1 =d 01 , N0 i =d 02 And N0 i+1 =d 01 When N1 i =d 11 ; Constraint 8: If N1 i =N1 i-1 , then the i-th movement distance of the first piston is L i is 0.

[0013] Furthermore, the termination condition of step 5 is that the total calculation time reaches a preset time upper limit, or the number of traversals reaches a preset number upper limit.

[0014] The advantages of the present invention are: (1) The control method of the present invention adopts a combination of constraint conditions and random selection according to the required moving path of the piston rod to solve the total moving distance of the first piston as the objective function value. By comparing the objective function value of the current solution with the objective function value of the current global optimal solution, the solution with the smaller objective function value is selected to update the current global optimal solution, thereby quickly obtaining the optimal moving path of the first piston with the shortest moving distance, minimizing the wear of the first piston to the greatest extent and extending the service life of the cylinder.

[0015] (2) The control method of the present invention not only sets the constraints on the stop position of the piston rod according to the characteristics of the oil cylinder, but also constrains the movement timing and movement process of the first piston to improve the response speed of the piston rod and reduce the interference of the first piston movement on the piston rod movement, thereby improving the control accuracy of the oil cylinder piston rod. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0017] Figure 1 It is a structural schematic diagram of the oil cylinder with a neutral position function of the present invention.

[0018] Figure 2 The figure is a flow chart of the center-position function cylinder control method of the six-axis horizontal machining center according to the present invention. DETAILED DESCRIPTION

[0019] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the specific implementation methods, structures, features and effects of the present invention are described in detail below in conjunction with the accompanying drawings and preferred embodiments.

[0020] Cylinders with neutral position function, such as Figure 1 As shown, it includes a cylinder, a first piston 21 and a second piston 22.

[0021] The cylinder body has a first piston accommodating chamber and a second piston accommodating chamber that are interconnected. In this embodiment, the cylinder body includes a cylinder barrel 11, a left end cap 12, and a right end cap 13. A stepped through hole is axially opened in the middle of the cylinder barrel 11. The stepped through hole includes a first through hole section 51 for forming the first piston accommodating chamber and a second through hole section 52 for forming the second piston accommodating chamber. The left end cap 12 and the right end cap 13 are respectively mounted at both ends of the cylinder barrel 11. The left end cap 12 covers the second through hole section 52, and the inner end surface of the left end cap 12 forms a left extreme position limit surface 43. The right end cap 13 covers the first through hole section 51, and the inner end surface of the right end cap 13 forms a right extreme position limit surface 41. The inner diameter of the second through hole section 52 is smaller than that of the first through hole section 51. The first through hole section 51 and the second through hole section 52 cooperate to form an intermediate position limit stepped surface 42.

[0022] The first piston 21 is movably disposed within the first piston accommodating chamber, with the outer wall of the first piston 21 sealingly connected to the inner wall of the first through-hole section 51. The second piston 22 is movably disposed within the second piston accommodating chamber, with the outer wall of the second piston 22 sealingly connected to the inner wall of the second through-hole section 52. The first piston 21 and the second piston 22 separate the interior of the cylinder body into a first oil chamber, a second oil chamber, and a third oil chamber. The first oil chamber is located on the side of the first piston 21 away from the second piston 22, the second oil chamber is located between the first piston 21 and the second piston 22, and the third oil chamber is located on the side of the second piston 22 away from the first piston 21. The cylinder body is provided with three oil inlets: a first oil inlet 31 communicating with the first oil chamber, a second oil inlet 32 ​​communicating with the second oil chamber, and a third oil inlet 33 communicating with the third oil chamber.

[0023] An intermediate push rod 23 is provided between the first piston 21 and the second piston 22. One end of the intermediate push rod 23 is fixed to the first piston 21, and the other end extends into the second piston accommodating cavity. A piston rod 24 is provided on the side of the second piston 22 away from the first piston 21. One end of the piston rod 24 is fixed to the second piston 22, and the other end extends out of the cylinder body through the through hole of the front end cover 12. The moving stroke of the first piston 21 is smaller than the axial length of the intermediate push rod 23, and the sum of the moving stroke of the first piston 21 and the axial length of the intermediate push rod 23 is smaller than the moving stroke of the second piston 22.

[0024] The oil cylinder is equipped with two independent pistons in different cavities of the cylinder body. The three oil inlets are used to control the pressure in the three oil cavities respectively, thus controlling the smooth movement of the two pistons. When the third oil inlet 33 is opened to oil, and the first and second oil inlets 31 and 32 are free of pressure, the second piston 22 drives the piston rod 24 to move rightward under the action of pressure, and pushes the first piston 21 to move rightward via the intermediate push rod 23. When the first piston 21 abuts against the right limit position limit surface 41, the cylinder piston rod 24 reaches the right limit position and stops. When the first oil inlet 31 and the third oil inlet 33 are connected to each other and oil is fed in by pressure, while the second oil inlet 32 ​​is free of pressure and the pressure at the third oil inlet 33 is lower than the pressure at the first oil inlet 31, the first piston 21 moves leftward under the action of the pressure and pushes the piston rod 24 leftward via the intermediate push rod 23 and the second piston 22. When the first piston 21 abuts against the intermediate position limit step surface 42, the piston rod 24 moves to the intermediate position and stops. When oil is fed into the second oil inlet 32 ​​under pressure and there is no pressure at the third oil inlet 33, the second piston 22, under pressure, drives the piston rod 24 to move leftward. When the second piston 22 contacts the left limit stop surface 43, the piston rod 24 moves leftward to the left limit position. During this process, the first piston 21 can selectively remain contacted with the intermediate limit step 42 (where the pressure at the first oil inlet 31 is greater than that at the second oil inlet), or move rightward and contact the right limit stop surface 41 (where there is no pressure at the first oil inlet 31). The position of the first piston 21 not only affects the response speed of the piston rod's next movement, but also, if the first piston is improperly positioned, can cause a cluttered travel, exacerbating wear on the first piston and shortening the service life of the cylinder.

[0025] The method for controlling the center-position functional cylinder of the six-axis horizontal machining center provided in this embodiment aims to quickly solve and obtain the optimal first piston movement path, shorten the first piston movement distance, minimize the wear of the first piston, and extend the service life of the cylinder.

[0026] Example Define the cluster N1 of the first piston movement stop position = {d 10 ,d 11}, wherein when the first piston 21 abuts against the right limit position limit surface 41, the first piston is at position d 10 When the first piston 21 abuts against the intermediate position limiting step surface 42, the first piston is at position d 11 .

[0027] The cluster N2 of the second piston movement stop position = {d 20 ,d 21 ,d 22 When the first piston 21 abuts against the right limit position limit surface 41 and the second piston 22 abuts against the end of the middle push rod, the second piston is in position d 20 When the first piston 21 abuts against the intermediate position limit step surface 42 and the second piston 22 abuts against the end of the intermediate push rod, the second piston is at position d 21 When the second piston 22 abuts against the left limit position limit surface 43, the second piston is at position d 22 .

[0028] The piston rod movement stop position cluster N0={d 00 ,d 01 ,d 02}, where d 00 ,d 01 ,d 02 Corresponding to the right limit position, the middle position and the left limit position respectively, the movement path of the piston rod n times is V={N01, N02.....N0 n}, the moving stop position N0 of the piston rod after the i-th movement i ={N1 i , N2 i},N0 i ∈N0, i∈N, N={1,2,.......,n}, n is the total number of times the piston rod moves. N1 i Indicates the first piston movement stop position corresponding to the piston rod's i-th movement stop, N1 i ∈N1,N2 i Indicates the second piston movement stop position corresponding to the piston rod's i-th movement stop, N2 i ∈N2.

[0029] The i-th moving stop position of the piston rod N0 i The following constraints exist: Constraint 1: If N0 i =d 00 , then N2 i =d 20 , and N1 i =d 10 ; Constraint 2: If N0i =d 01 , then N2 i =d 21 , and N1 i =d 11 ; Constraint 3: If N0 i =d 02 , then N2 i =d 22 ; The following constraints exist during the movement of the piston rod: Constraint 4: If N0 i-1 =d 00 , N0 i =d 02 And N0 i+1 =d 00 When N1 i =d 10 , which means that when the piston rod moves in the order of right limit position, left limit position, and right limit position, the position d of the first piston 10 Stay still; Constraint 5: If N0 i-1 =d 00 , N0 i =d 02 And N0 i+1 =d 01 When N1 i =d 11 , which means that when the piston rod moves in the order of right limit position, left limit position and middle position, the first piston moves from position d to left limit position during the process of the piston rod moving from right limit position to left limit position. 10 Move to position d 11 , then remain stationary; Constraint 6: If N0 i-1 =d 01 , N0 i =d 02 And N0 i+1 =d 00 When N1 i =d 10 , which means that when the piston rod moves in the order of the middle position, left limit position, and right limit position, during the process of the piston rod moving from the middle position to the left limit position, the first piston moves from position d 11 Move to position d 10 , then remain stationary; Constraint 7: If N0 i-1 =d 01 , N0 i =d 02 And N0i+1 =d 01 When N1 i =d 11 , which means that when the piston rod moves in the order of middle position, left limit position, and middle position, the position d of the first piston 11 Stay still; Constraint 8: If N1 i =N1 i-1 , then the i-th movement distance of the first piston is L i When it is 0, it means that when the first piston stops at the same position for two consecutive movements, the first piston does not make any additional movement and directly keeps the position fixed.

[0030] The embodiment provides a method for controlling the center-position hydraulic cylinder of a six-axis horizontal machining center. Figure 2 As shown, the following steps are included: Step 1: Initialize the position of the cylinder piston rod and move the piston rod to the right limit position d 00 , construct the initial solution S0 of the movement path of the first piston, and use S0 as the current global optimal solution S * ; When the initial solution S0 of the movement path of the first piston is constructed, the piston rod movement path V={N01, N02.....N0 n If the constraints are met, the first piston's moving stop position is selected according to the constraints. If the constraints are not met, the first piston's moving stop position is randomly selected. After the piston rod moving path is traversed, an initial solution of the first piston's moving path S0 = {N11, N12.....N1 n}.

[0031] Step 2: The required moving path of the piston rod is V={N01, N02.....N0 n}, traverse the piston rod movement path, if the constraints are met, select the movement stop position of the first piston each time the piston rod moves according to the constraints. If the constraints are not met, randomly select the movement stop position of the first piston and calculate the movement distance of the first piston each time the piston rod moves , the calculation formula is as follows: ; Step 3: traverse the piston rod movement path, generate the current solution S of the movement path of the first piston, and calculate the objective function value of the current solution S of the movement path of the first piston , the calculation formula is: ; Step 4: Compare the current solution S of the first piston's moving path with the current global optimal solution S* Compare, if the current solution S is better than the current global best solution S * ,Right now < , then update S*; Step 5: Repeat steps 2-4 until the termination condition is met, that is, the total calculation time reaches the preset time limit, or the number of traversals reaches the preset number limit, and finally return the recorded global optimal solution S*.

[0032] The control method of this embodiment adopts a combination of constraints and random selection based on the required movement path of the piston rod to solve the total movement distance of the first piston as the objective function value. By comparing the objective function value of the current solution with the objective function value of the current global optimal solution, the solution with the smaller objective function value is selected to update the current global optimal solution, thereby obtaining the optimal movement path of the first piston with the shortest movement distance, minimizing the wear of the first piston to the greatest extent and extending the service life of the cylinder.

[0033] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can, without departing from the scope of the technical solution of the present invention, make some changes or modifications to equivalent embodiments using the technical contents disclosed above. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for controlling a center-position oil cylinder of a six-axis horizontal machining center, wherein the oil cylinder with a center-position function comprises a cylinder body, a first piston and a second piston, the cylinder body having a first piston accommodating chamber and a second piston accommodating chamber that are interconnected, an intermediate position limiting step surface being formed between the first piston accommodating chamber and the second piston accommodating chamber, the first piston accommodating chamber having a right extreme position limiting surface on a side away from the second piston accommodating chamber, and the second piston accommodating chamber having a left extreme position limiting surface on a side away from the first piston accommodating chamber, the first piston and the second piston being movably arranged in the first piston accommodating chamber and the second piston accommodating chamber, respectively, and dividing the cylinder body into three oil chambers with oil inlets, the first piston having an intermediate push rod on a side close to the second piston, and the second piston having a piston rod on a side away from the first piston, the moving stroke of the first piston being less than the axial length of the intermediate push rod, and the sum of the moving stroke of the first piston and the axial length of the intermediate push rod being less than the moving stroke of the second piston, characterized in that: The control method comprises the following steps: Step 1: Initialize the position of the cylinder piston rod and move the piston rod to the right limit position d 00 , construct the initial solution S0 of the movement path of the first piston, and use S0 as the current global optimal solution S * ; Step 2: The required moving path of the piston rod is V={N01, N02.....N0 n }, traverse the piston rod movement path, if the constraints are met, select the movement stop position of the first piston each time the piston rod moves according to the constraints. If the constraints are not met, randomly select the movement stop position of the first piston and calculate the movement distance of the first piston each time the piston rod moves , the calculation formula is as follows: ； in, Indicates the moving stop position of the first piston when the piston rod stops for the i-th time, Indicates the movement stop position of the first piston when the piston rod stops moving for the i-1th time; Step 3: traverse the piston rod movement path, generate the current solution S of the movement path of the first piston, and calculate the objective function value of the current solution S of the movement path of the first piston , the calculation formula is: ； Step 4: Compare the current solution S of the first piston's moving path with the current global optimal solution S * Compare, if the current solution S is better than the current global best solution S * ,Right now < , then update S*; Step 5: Repeat steps 2-4 until the termination condition is met, and finally return the recorded global optimal solution S*.

2. The method for controlling the center-position hydraulic cylinder of a six-axis horizontal machining center according to claim 1, characterized in that: The control method includes the following definitions: The cluster N1 of the first piston movement stop position = {d 10 ,d 11 }, wherein when the first piston is against the right limit position limit surface, the first piston is at position d 10 When the first piston is against the intermediate position limit step surface, the first piston is at position d 11 ; The cluster N2 of the second piston movement stop position = {d 20 ,d 21 ,d 22 }, wherein when the first piston is against the right limit position limit surface and the second piston is against the end of the middle push rod, the second piston is in position d 20 When the first piston is against the intermediate position limit step surface and the second piston is against the end of the intermediate push rod, the second piston is in position d 21 When the second piston is against the left limit position limit surface, the second piston is at position d 22 ; The piston rod movement stop position cluster N0={d 00 ,d 01 ,d 02 }, where d 00 ,d 01 ,d 02 Corresponding to the right limit position, the middle position and the left limit position respectively, the movement path of the piston rod n times is V={N01, N02.....N0 n }, the moving stop position N0 of the piston rod after the i-th movement i ={N1 i , N2 i },N0 i ∈N0, i∈N, N={1,2,.......,n}, n is the total number of piston rod movements, N1 i ∈N1,N2 i Indicates the second piston movement stop position corresponding to the piston rod's i-th movement stop, N2 i ∈N2.

3. The method for controlling the center-position hydraulic cylinder of a six-axis horizontal machining center according to claim 2, wherein: When the initial solution S0 of the movement path of the first piston is constructed in step 1, the piston rod movement path V={N01, N02.....N0 n If the constraints are met, the first piston's moving stop position is selected according to the constraints. If the constraints are not met, the first piston's moving stop position is randomly selected. After the piston rod moving path is traversed, an initial solution of the first piston's moving path S0 = {N11, N12.....N1 n }.

4. The method for controlling the center-position hydraulic cylinder of a six-axis horizontal machining center according to claim 3, wherein: The constraints include: The i-th moving stop position of the piston rod N0 i The following constraints exist: Constraint 1: If N0 i =d 00 , then N2 i =d 20 , and N1 i =d 10 ; Constraint 2: If N0 i =d 01 , then N2 i =d 21 , and N1 i =d 11 ; Constraint 3: If N0 i =d 02 , then N2 i =d 22 ; The following constraints exist during the movement of the piston rod: Constraint 4: If N0 i-1 =d 00 , N0 i =d 02 And N0 i+1 =d 00 When N1 i =d 10 ; Constraint 5: If N0 i-1 =d 00 , N0 i =d 02 And N0 i+1 =d 01 When N1 i =d 11 ; Constraint 6: If N0 i-1 =d 01 , N0 i =d 02 And N0 i+1 =d 00 When N1 i =d 10 ; Constraint 7: If N0 i-1 =d 01 , N0 i =d 02 And N0 i+1 =d 01 When N1 i =d 11 ; Constraint 8: If N1 i =N1 i-1 , then the i-th movement distance of the first piston is L i is 0.

5. The method for controlling the center-position hydraulic cylinder of a six-axis horizontal machining center according to claim 4, wherein: The constraint conditions include: the termination condition of step 5 is that the total calculation time reaches a preset time upper limit, or the number of traversals reaches a preset number upper limit.

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