A fixed-time sliding mode based tension control method and system for multi-wire saw

Abstract

The application belongs to the technical field of multi-wire saw tension, and provides a multi-wire saw tension control method and system based on fixed-time sliding mode. The method comprises the following steps: an equivalent model of the multi-wire saw tension system is established, and transformation processing is performed on the equivalent model to obtain a direct tension control model; based on the direct tension control model, fixed-time sliding mode surfaces are respectively established for a main motor, a wire feeding motor and a wire collecting motor, corresponding fixed-time sliding mode approaching laws are designed, fixed-time sliding mode control laws of the motors are derived and the stability thereof is verified; and the tension of the multi-wire saw during operation is cooperatively controlled according to the fixed-time sliding mode control laws. Through the method provided by the application, the angular velocity of the main motor and the wire feeding and collecting tension can be converged to given values within fixed time, and the convergence time is independent of the initial state of the system, so that the response speed and stability of the tension control are improved.

Description

Technical Field

[0001] This invention belongs to the field of tension technology for multi-wire cutting machines, specifically relating to a tension control method and system for multi-wire cutting machines based on a fixed-time sliding mode. Background Technology

[0002] With economic development and social progress, people's demand for energy is constantly increasing, and the development and utilization of new energy sources has become an important issue that urgently needs to be addressed. Solar energy, due to its advantages such as abundant resources, wide distribution, safety, cleanliness, and sustainable utilization, has become one of the important energy forms for the future. Solar power generation typically achieves photoelectric conversion through solar cells.

[0003] Multi-wire dicing machines for solar silicon wafers are crucial equipment in solar cell production. They are typical electro-tension systems integrating mechanical, electrical, pneumatic, and lubrication systems. During high-speed, high-load operation, variations in wire tension and speed, as well as the effects of vibration and friction, significantly impact the system's operational stability and tension control accuracy, thus limiting cutting efficiency and processing quality. Tension control is a key technology in silicon wafer dicing; unstable tension control can easily lead to problems such as wire marks, edge chipping, and even wire breakage, resulting in substantial economic losses.

[0004] Currently, tension control methods for multi-wire cutting machines mainly include direct tension control and indirect tension control. Direct tension control, while maintaining the spindle's operating speed, measures the tension values ​​on the take-up and pay-off sides. Based on the deviation between the set tension and the actual tension, it adjusts the operating status of the corresponding motors, thereby adjusting the wire speed in real time to keep the tension within the target range. Compared to indirect tension control, direct tension control has advantages such as faster system response, more intuitive control process, and higher tension visualization.

[0005] In existing technologies, various control algorithms have been applied to the direct tension control of multi-wire cutting machines, such as PID control, H ∞ Methods such as control and sliding mode control are used. However, most of the above control methods can only achieve asymptotic or exponential convergence of tension with respect to the target value, focusing mainly on the stability of the system and less on the controllability of the convergence time.

[0006] Fixed-time control is a type of control method that uses pre-designed control parameters to enable the system state to converge to the equilibrium point within a finite time. Its upper bound on the convergence time is independent of the initial state of the system, and it has strong robustness and anti-interference ability.

[0007] Therefore, it is necessary to provide a tension control method that combines fixed-time control theory with sliding mode control method to solve the problem of uncontrollable convergence time in the existing technology, thereby improving the dynamic performance and stability of tension control in multi-wire cutting machines. Summary of the Invention

[0008] This invention addresses the problems of slow response speed, convergence time dependence on initial state, poor robustness, and difficulty in achieving fast and stable tension control in existing multi-wire cutting machine tension control. It provides a tension control method and system for multi-wire cutting machines based on fixed-time sliding mode, which achieves fast, accurate, and stable tension control of multi-wire cutting machines, thereby improving cutting accuracy and equipment operational reliability.

[0009] To achieve the above objectives, the present invention adopts one or more of the following technical solutions: In a first aspect, the present invention provides a tension control method for a multi-wire cutting machine based on a fixed-time sliding mode, the method comprising the following steps: S1. Establish an equivalent model of the tension system of the multi-wire cutting machine, and transform the equivalent model to obtain the direct tension control model of the multi-wire cutting machine. S2. Based on the direct tension control model, a fixed-time sliding surface of the main motor is introduced, and a fixed-time sliding mode approaching law of the main motor is designed. Combining the fixed-time sliding surface of the main motor and the fixed-time sliding mode approaching law of the main motor, the control law of the main motor is obtained. S3. Based on the direct tension control model, a fixed-time sliding surface of the wire feeding motor is introduced, and a fixed-time sliding mode approaching law of the wire feeding motor is designed. Combining the fixed-time sliding surface of the wire feeding motor and the fixed-time sliding mode approaching law of the wire feeding motor, the control law of the wire feeding motor is obtained. S4. Based on the direct tension control model, a fixed-time sliding surface of the take-up motor is introduced, and a fixed-time sliding mode approaching law of the take-up motor is designed. Combining the fixed-time sliding surface of the take-up motor and the fixed-time sliding mode approaching law of the take-up motor, the control law of the take-up motor is obtained. S5. The tension of the multi-wire cutting machine is controlled by the coordinated control of the main motor, the wire feeding motor and the wire taking-up motor.

[0010] Furthermore, corresponding Lyapunov functions are constructed for the fixed-time sliding surfaces of the main motor, the pay-off motor, and the take-up motor, and their derivatives are calculated to ensure that each sliding surface converges to zero within a fixed time, thereby achieving stable tension control.

[0011] Furthermore, the equivalent model expression of the tension system of the multi-wire cutting machine is as follows:

[0012]

[0013]

[0014]

[0015]

[0016] In the formula, , and These represent the equivalent moments of inertia of the pay-off motor, the main motor, and the take-up motor, respectively. , and v1, v2, and v3 represent the angular velocities of the pay-off motor, main motor, and take-up motor, respectively; v1, v2, and v3 represent the linear velocities of the pay-off motor, main motor, and take-up motor, respectively. , and These represent the output torques of the pay-off motor, main motor, and take-up motor, respectively. , and Indicates the radius of the thread reel; and Indicates the tension during wire release and take-up; , and These represent the viscous friction coefficients of the pay-off motor, the main motor, and the take-up motor, respectively. Indicates the cross-sectional area of ​​the line; and Indicates the length of the line laid out and retrieved. It is Young's modulus.

[0017] Furthermore, the process of transforming the equivalent model of the tension system of the multi-wire cutting machine to obtain the direct tension control model of the multi-wire cutting machine is as follows: First, establish the basic constraint relationship between linear velocity and angular velocity. The linear velocity and angular velocity of the wire-laying motor, main motor, and take-up motor satisfy the following: Linear velocity of the wire feeding motor ; Main motor linear speed ; Linear speed of the take-up motor ; Secondly, it was determined that the radius of the pay-off reel decreases with running time, while the radius of the take-up reel increases with running time; that is, the time-varying law of the radius is as follows: ,

[0018] ,

[0019] In the formula, Indicates line thickness; and Indicates the initial radius; Then, combining the physical parameters of the yarn, the expression for the real-time rotational inertia of the take-up and pay-off reels as a function of the reel diameter is determined, i.e.

[0020]

[0021] In the formula, Indicates the density of the line; Indicates the line width; and Indicates the initial moment of inertia; Finally, the linear velocity-angular velocity constraint relationship, the time-varying law of radius, and the time-varying expression of moment of inertia are substituted into the equivalent dynamic model of the tension system. The dynamic equations are differentiated, redundant intermediate variables are eliminated, and like terms are combined. Finally, a direct tension control model that can directly realize tension closed-loop control is derived.

[0022] Furthermore, the expression for the direct tension control model of the multi-wire cutting machine is as follows:

[0023]

[0024]

[0025] in, , , , , ,

[0026]

[0027] .

[0028] Furthermore, the expression for the fixed-time sliding surface of the main motor is:

[0029] In the formula, This indicates the tracking error of the main motor; This represents the given angular velocity of the main motor; and It is a constant. and It is a constant; The expression for the fixed-time sliding mode reaching law of the main motor is:

[0030] In the formula, , and It is a constant; The expression for the control law of the main motor is: .

[0031] Furthermore, the expression for the fixed-time sliding surface of the wire-feeding motor is:

[0032] In the formula, This indicates the tracking error of the wire tension. This indicates the given number of sheets of wire to be laid out; , and It is a constant; The expression for the fixed-time sliding mode reaching law of the wire feeding motor is:

[0033] In the formula, , and It is a constant; The expression for the control law of the wire feeding motor is: .

[0034] Furthermore, the expression for the fixed-time sliding surface of the take-up motor is:

[0035] In the formula, This indicates the tracking error of the take-up tension; Indicates the given take-up tension; , and It is a constant; The expression for the fixed-time sliding mode reaching law of the take-up motor is:

[0036] In the formula, , and constant The expression for the control law of the take-up motor is: .

[0037] Secondly, the present invention provides a tension control system for a multi-wire cutting machine based on a fixed-time sliding mode, the control system comprising: The model building module is used to establish an equivalent model of the tension system of the multi-wire cutting machine, and to transform the equivalent model to obtain the direct tension control model of the multi-wire cutting machine. The main motor control module is used to introduce a fixed-time sliding surface of the main motor based on the direct tension control model, design a fixed-time sliding mode approaching law of the main motor, and obtain the control law of the main motor by combining the fixed-time sliding surface of the main motor and the fixed-time sliding mode approaching law of the main motor. The wire feeding motor control module is used to introduce a fixed-time sliding surface of the wire feeding motor based on the direct tension control model, design a fixed-time sliding surface approach law of the wire feeding motor, and combine the fixed-time sliding surface of the wire feeding motor and the fixed-time sliding surface approach law of the wire feeding motor to obtain the control law of the wire feeding motor. The take-up motor control module is used to introduce a fixed-time sliding surface of the take-up motor based on the direct tension control model, design a fixed-time sliding mode approaching law of the take-up motor, and obtain the control law of the take-up motor by combining the fixed-time sliding surface of the take-up motor and the fixed-time sliding mode approaching law of the take-up motor. The tension control execution module is used to control the tension of the multi-wire cutting machine during operation by coordinating the control laws of the main motor, the wire feeding motor, and the wire take-up motor.

[0038] Thirdly, the present invention provides a non-volatile computer storage medium, characterized in that it stores computer-executable instructions, wherein the computer-executable instructions are configured to implement the tension control method for a multi-wire cutting machine based on a fixed-time sliding mode as described in any of the above claims.

[0039] The technical solution of this invention can achieve the following beneficial effects: This invention proposes a tension control method for multi-wire cutting machines based on fixed-time sliding mode. By designing fixed-time sliding mode control laws for the main motor, the wire feeding motor, and the wire take-up motor, it can not only ensure that the angular velocity of the main motor converges to a given angular velocity within a fixed time, but also ensure that the wire feeding tension and the wire take-up tension converge to their respective given tensions within a fixed time. Moreover, the convergence time does not depend on the initial state of the system, thus effectively solving the problems of convergence speed being affected by the initial state and uncontrollable convergence time in existing tension control methods. Attached Figure Description

[0040] Figure 1 This is a flowchart of a tension control method for a multi-wire cutting machine based on a fixed-time sliding mode, provided by an embodiment of the present invention. Figure 2 This is a diagram showing the response curve of fixed-time sliding mode tension control in a undisturbed scenario of an application scenario of a multi-wire cutting machine tension control method based on fixed-time sliding mode provided in an embodiment of the present invention. Figure 3 This is a diagram showing the tension control error curve of a multi-wire cutting machine based on a fixed-time sliding mode in an application scenario without disturbance, as provided in an embodiment of the present invention. Figure 4 This is a response curve of the tension control of a multi-wire cutting machine based on a fixed-time sliding mode under disturbance in an application scenario provided by an embodiment of the present invention. Figure 5 This is a diagram showing the error curve of the fixed-time sliding mode tension control method for multi-wire cutting machines under disturbance conditions, provided by an embodiment of the present invention. Figure 6 This is a schematic diagram of a tension control system for a multi-wire cutting machine based on a fixed-time sliding mode, provided by an embodiment of the present invention. Figure 7 This is a schematic diagram of the structure of a tension control device for a multi-wire cutting machine based on a fixed-time sliding mode, provided by an embodiment of the present invention. Detailed Implementation

[0041] The technical solutions of the embodiments of the present invention will now be described in detail and completely with reference to the accompanying drawings. It should be noted that the described embodiments are merely some examples of the present invention and do not represent all possible implementations of the present invention. Any other implementations obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the protection scope of the present invention.

[0042] Example 1 Figure 1 The flowchart of a tension control method for a multi-wire cutting machine based on a fixed-time sliding mode provided by the present invention.

[0043] The method flow steps of the embodiments in this specification are as follows: S1. Establish an equivalent model of the tension system of the multi-wire cutting machine, and transform the equivalent model to obtain the direct tension control model of the multi-wire cutting machine.

[0044] Specifically, the equivalent model expression of the tension system of the multi-wire cutting machine is as follows:

[0045]

[0046]

[0047]

[0048]

[0049] In the formula, , and These represent the equivalent moments of inertia of the pay-off motor, the main motor, and the take-up motor, respectively. , and v1, v2, and v3 represent the angular velocities of the pay-off motor, main motor, and take-up motor, respectively; v1, v2, and v3 represent the linear velocities of the pay-off motor, main motor, and take-up motor, respectively. , and These represent the output torques of the pay-off motor, main motor, and take-up motor, respectively. , and Indicates the radius of the thread reel; and Indicates the tension during wire release and take-up; , and These represent the viscous friction coefficients of the pay-off motor, the main motor, and the take-up motor, respectively. Indicates the cross-sectional area of ​​the line; and Indicates the length of the line laid out and retrieved. It is Young's modulus.

[0050] During the operation of the multi-wire cutting machine, the radius of the take-up and pay-off reels is constantly changing, and the expression for this change is as follows: ,

[0051] ,

[0052] In the formula, Indicates line thickness; and This represents the initial radius.

[0053] The expression for the moment of inertia of the take-up and pay-off reels is:

[0054]

[0055] In the formula, Indicates the density of the line; Indicates the line width; and This represents the initial moment of inertia.

[0056] The expression for the relationship between linear velocity and angular velocity is: .

[0057] Specifically, based on the relationship between linear velocity and angular velocity, and the equivalent model of the tension system of a multi-wire cutting machine and the radius variation law of the take-up and untake-down reels, a direct tension control model for the multi-wire cutting machine is obtained, namely... First, establish the basic constraint relationship between linear velocity and angular velocity. The linear velocity and angular velocity of the wire-laying motor, main motor, and take-up motor satisfy the following: Linear velocity of the wire feeding motor ; Main motor linear speed ; Linear speed of the take-up motor ; Secondly, considering the change in wheel diameter caused by the continuous winding and unwinding of the wire during the continuous operation of the multi-wire cutting machine, it is determined that the radius of the unwinding wheel decreases with running time, while the radius of the take-up wheel increases with running time; that is, the time-varying law of the radius is as follows: ,

[0058] ,

[0059] In the formula, Indicates line thickness; and Indicates the initial radius; Then, combining the physical parameters of the yarn, the expression for the real-time rotational inertia of the take-up and pay-off reels as a function of the reel diameter is determined, i.e.

[0060]

[0061] In the formula, Indicates the density of the line; Indicates the line width; and Indicates the initial moment of inertia; Finally, the linear velocity-angular velocity constraint relationship, the time-varying law of radius, and the time-varying expression of moment of inertia are substituted into the equivalent dynamic model of the tension system. The dynamic equations are differentiated, redundant intermediate variables are eliminated, and like terms are combined. Ultimately, a direct tension control model that can directly achieve closed-loop tension control is derived. The expression for the direct tension control model of the multi-wire cutting machine is as follows:

[0062]

[0063] .

[0064] in, , , , , ,

[0065]

[0066] .

[0067] S2. Based on the direct tension control model, a fixed-time sliding surface of the main motor is introduced, and a fixed-time sliding mode approaching law of the main motor is designed. Combining the fixed-time sliding surface of the main motor and the fixed-time sliding mode approaching law of the main motor, the control law of the main motor is obtained.

[0068] Specifically, a corresponding Lyapunov function is constructed for the fixed-time sliding surface of the main motor, and its derivative is calculated to verify the stability of the control law of the main motor.

[0069] Specifically, firstly, in order to control the movement of the main motor, a fixed-time sliding surface for the main motor is introduced. The expression for the fixed-time sliding surface of the main motor is as follows:

[0070] In the formula, This indicates the tracking error of the main motor; This represents the given angular velocity of the main motor; and It is a constant. and It is a constant.

[0071] Secondly, by differentiating the fixed-time sliding surface of the main motor, we obtain: .

[0072] Next, the fixed-time sliding mode reaching law of the main motor is designed, and the expression of the fixed-time sliding mode reaching law of the main motor is:

[0073] In the formula, , and It is a constant.

[0074] Then, combining the fixed-time sliding surface of the main motor with the fixed-time sliding mode approach law of the main motor, the control law of the main motor is obtained, and the expression of the control law of the main motor is: .

[0075] Finally, the corresponding Lyapunov function is constructed and its derivative is calculated to verify the stability of the control law for the main motor. Selecting Lyapunov functions:

[0076] Differentiating it, we get:

[0077] According to the fixed-time stability theory, the fixed-time sliding surface of the main motor tends to zero within a fixed time, and the upper bound of the convergence time is: .

[0078] S3. Based on the direct tension control model, a fixed-time sliding surface of the wire feeding motor is introduced, and a fixed-time sliding mode approaching law of the wire feeding motor is designed. Combining the fixed-time sliding surface of the wire feeding motor and the fixed-time sliding mode approaching law of the wire feeding motor, the control law of the wire feeding motor is obtained.

[0079] Specifically, a corresponding Lyapunov function is constructed for the fixed-time sliding surface of the wire-feeding motor, and its derivative is calculated to verify the stability of the control law of the wire-feeding motor.

[0080] Specifically, firstly, a fixed-time sliding surface for the wire feeding motor is introduced, and the expression for the fixed-time sliding surface of the wire feeding motor is:

[0081] In the formula, This indicates the tracking error of the wire tension. This indicates the given number of sheets of wire to be laid out; , and It is a constant.

[0082] Secondly, by differentiating the fixed-time sliding surface of the wire feeding motor, we obtain: .

[0083] Next, the fixed-time sliding mode reaching law of the wire feeding motor is designed, and the expression of the fixed-time sliding mode reaching law of the wire feeding motor is:

[0084] In the formula, , and It is a constant.

[0085] Then, combining the fixed-time sliding surface of the wire feeding motor with the fixed-time sliding mode approach law of the wire feeding motor, the control law of the wire feeding motor is obtained. The expression of the control law of the wire feeding motor is: .

[0086] Finally, the corresponding Lyapunov function is constructed and its derivative is calculated to verify the stability of the control law for the wire-feeding motor. Selecting Lyapunov functions:

[0087] Differentiating it, we get:

[0088] According to the fixed-time stability theory, the fixed-time sliding surface of the wire-feeding motor tends to zero within a fixed time, and the upper bound of the convergence time is: .

[0089] S4. Based on the direct tension control model, a fixed-time sliding surface of the take-up motor is introduced, and a fixed-time sliding mode approaching law of the take-up motor is designed. Combining the fixed-time sliding surface of the take-up motor and the fixed-time sliding mode approaching law of the take-up motor, the control law of the take-up motor is obtained.

[0090] Specifically, a corresponding Lyapunov function is constructed for the fixed-time sliding surface of the take-up motor, and its derivative is calculated to verify the stability of the control law of the take-up motor.

[0091] Specifically, firstly, a fixed-time sliding surface for the take-up motor is introduced, and the expression for the fixed-time sliding surface of the take-up motor is:

[0092] In the formula, This indicates the tracking error of the take-up tension; Indicates the given take-up tension; , and It is a constant.

[0093] Secondly, by differentiating the fixed-time sliding surface of the take-up motor, we obtain: .

[0094] Next, the fixed-time sliding mode reaching law of the take-up motor is designed, and the expression of the fixed-time sliding mode reaching law of the take-up motor is:

[0095] In the formula, , and It is a constant.

[0096] Then, combining the fixed-time sliding surface of the take-up motor with the fixed-time sliding mode approach law of the take-up motor, the control law of the take-up motor is obtained. The expression of the control law of the take-up motor is: .

[0097] Finally, the corresponding Lyapunov function is constructed and its derivative is calculated to verify the stability of the control law for the wire-feeding motor. Selecting Lyapunov functions:

[0098] Differentiating it, we get:

[0099] According to the fixed-time stability theory, the fixed-time sliding surface of the wire-feeding motor tends to zero within a fixed time, and the upper bound of the convergence time is: .

[0100] S5. The tension of the multi-wire cutting machine during operation is controlled according to the control laws of the main motor, the wire feeding motor, and the wire take-up motor.

[0101] Specifically, the multi-wire cutting machine is controlled according to the control laws of the main motor, the wire feeding motor, and the wire take-up motor to ensure that the tension of the multi-wire cutting machine converges to the given tension value within a fixed time.

[0102] Specifically, such as Figures 2 to 5 As shown in the accompanying drawings, the application scenarios and effects of the tension control method for multi-wire cutting machines based on fixed-time sliding mode according to the embodiments of the present invention will be further described below: Taking the tension control on the wire feeding side of a multi-wire cutting machine as an example (the structure of the wire take-up side is the same as that of the wire feeding side), a simulation model of the wire feeding side and the motor of the multi-wire cutting machine is established. Tension control is adopted on the wire feeding side, and speed control is adopted on the spindle. Simulation comparison experiments are conducted using two methods: traditional sliding mode control and the fixed-time sliding mode control of the present invention. The simulation parameters of the multi-wire cutting machine model are shown in Table 1.

[0103] Table 1 Simulation Parameters of Multi-Wire Cutting Machine

[0104] The controller parameters are set as follows: , ,

[0105] and , ,

[0106] , , , ,

[0107] , , .

[0108] Figure 2 and Figure 3 The figures show the tension control response curve and tension control error curve under undisturbed conditions, respectively. Simulation results show that the tension converges to the given value more slowly with traditional sliding mode control; however, the fixed-time sliding mode control of this invention achieves faster convergence and smoother system operation. Therefore, the fixed-time sliding mode control of this invention can effectively improve the tension convergence speed.

[0109] To test the anti-interference performance of the control algorithm, in Apply a transient disturbance to the system. Figure 4 and Figure 5 The figures show the tension control response curve and tension control error curve under disturbance conditions, respectively. Simulation results show that traditional sliding mode control has poor suppression of sudden transient disturbances, resulting in a longer system recovery time. In contrast, the fixed-time sliding mode control of this invention can respond quickly and suppress disturbances, and the system recovers to a stable state much faster. Therefore, compared to traditional sliding mode control schemes, the fixed-time sliding mode control of this invention has superior anti-interference performance.

[0110] Example 2 Figure 6 A schematic diagram of a tension control system for a multi-wire cutting machine based on a fixed-time sliding mode, provided by the present invention, is shown below. The system includes: The model building module is used to establish an equivalent model of the tension system of the multi-wire cutting machine, and to transform the equivalent model to obtain the direct tension control model of the multi-wire cutting machine. The main motor control module is used to introduce a fixed-time sliding surface of the main motor based on the direct tension control model, design a fixed-time sliding mode approaching law of the main motor, and obtain the control law of the main motor by combining the fixed-time sliding surface of the main motor and the fixed-time sliding mode approaching law of the main motor. The wire feeding motor control module is used to introduce a fixed-time sliding surface of the wire feeding motor based on the direct tension control model, design a fixed-time sliding surface approach law of the wire feeding motor, and combine the fixed-time sliding surface of the wire feeding motor and the fixed-time sliding surface approach law of the wire feeding motor to obtain the control law of the wire feeding motor. The take-up motor control module is used to introduce a fixed-time sliding surface of the take-up motor based on the direct tension control model, design a fixed-time sliding mode approaching law of the take-up motor, and obtain the control law of the take-up motor by combining the fixed-time sliding surface of the take-up motor and the fixed-time sliding mode approaching law of the take-up motor. The tension control execution module is used to control the tension of the multi-wire cutting machine during operation by coordinating the control laws of the main motor, the wire feeding motor, and the wire take-up motor.

[0111] Example 3 Figure 7 A schematic diagram of a tension control device for a multi-wire cutting machine based on a fixed-time sliding mode, provided by the present invention, includes: At least one processor; and, A memory communicatively connected to the at least one processor; wherein, The memory has instructions that can be executed by the at least one processor, which enables the at least one processor to perform a tension control method for a multi-wire cutting machine based on a fixed-time sliding mode provided in Embodiment 1.

[0112] This invention also provides a non-volatile computer storage medium, characterized in that it stores computer-executable instructions, which are configured to implement the tension control method for a multi-wire cutting machine based on a fixed-time sliding mode provided in Embodiment 1.

[0113] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on describing the differences from other embodiments. In particular, the method and system embodiments are basically similar to the method embodiments, so the descriptions are relatively simple; relevant parts can be referred to the descriptions of the method embodiments.

[0114] The foregoing has described specific embodiments of this specification. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recited in the claims may be performed in a different order than that shown in the embodiments and may still achieve the desired result. Furthermore, the processes depicted in the drawings do not necessarily require the specific or sequential order shown to achieve the desired result. In some embodiments, multitasking and parallel processing are possible or may be advantageous.

[0115] The above description is merely one or more embodiments of this specification and is not intended to limit this specification. Various modifications and variations can be made to the one or more embodiments of this specification by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of one or more embodiments of this specification should be included within the scope of the claims of this specification.

Claims

1. A tension control method for a multi-wire cutting machine based on a fixed-time sliding mode, characterized in that, The method includes the following steps: S1. Establish an equivalent model of the tension system of the multi-wire cutting machine, and transform the equivalent model to obtain the direct tension control model of the multi-wire cutting machine. S2. Based on the direct tension control model, a fixed-time sliding surface of the main motor is introduced, and a fixed-time sliding mode approaching law of the main motor is designed. Combining the fixed-time sliding surface of the main motor and the fixed-time sliding mode approaching law of the main motor, the control law of the main motor is obtained. S3. Based on the direct tension control model, a fixed-time sliding surface of the wire feeding motor is introduced, and a fixed-time sliding mode approaching law of the wire feeding motor is designed. Combining the fixed-time sliding surface of the wire feeding motor and the fixed-time sliding mode approaching law of the wire feeding motor, the control law of the wire feeding motor is obtained. S4. Based on the direct tension control model, a fixed-time sliding surface of the take-up motor is introduced, and a fixed-time sliding mode approaching law of the take-up motor is designed. Combining the fixed-time sliding surface of the take-up motor and the fixed-time sliding mode approaching law of the take-up motor, the control law of the take-up motor is obtained. S5. The tension of the multi-wire cutting machine during operation is controlled by the coordinated control of the control laws of the main motor, the wire feeding motor, and the wire take-up motor. The expression for the fixed-time sliding surface of the main motor is: In the formula, This indicates the tracking error of the main motor; This indicates the actual angular velocity of the main motor; This represents the given angular velocity of the main motor; and It is a constant. and It is a constant; The expression for the fixed-time sliding mode reaching law of the main motor is: In the formula, , and It is a constant; The expression for the control law of the main motor is: in, ， In the formula, This indicates the output torque of the main motor; This represents the equivalent moment of inertia of the main motor. Indicates the radius of the thread reel; and Indicates the tension during wire release and take-up; This represents the viscous friction coefficient of the main motor; This indicates the angular velocity of the main motor.

2. The tension control method for a multi-wire cutting machine based on a fixed-time sliding mode according to claim 1, characterized in that, Lyapunov functions are constructed for the fixed-time sliding surfaces of the main motor, the pay-off motor, and the take-up motor, and their derivatives are calculated to ensure that each sliding surface converges to zero within a fixed time, thereby achieving stable tension control.

3. The tension control method for a multi-wire cutting machine based on a fixed-time sliding mode according to claim 1, characterized in that, The equivalent model expression for the tension system of the multi-wire cutting machine is: In the formula, , and These represent the equivalent moments of inertia of the pay-off motor, the main motor, and the take-up motor, respectively. , and v1, v2, and v3 represent the angular velocities of the pay-off motor, main motor, and take-up motor, respectively; v1, v2, and v3 represent the linear velocities of the pay-off motor, main motor, and take-up motor, respectively. , and These represent the output torques of the pay-off motor, main motor, and take-up motor, respectively. , and Indicates the radius of the thread reel; and Indicates the tension during wire release and take-up; , and These represent the viscous friction coefficients of the pay-off motor, the main motor, and the take-up motor, respectively. Indicates the cross-sectional area of ​​the line; and Indicates the length of the line laid out and retrieved. It is Young's modulus.

4. The tension control method for a multi-wire cutting machine based on a fixed-time sliding mode according to claim 3, characterized in that, The specific process of transforming the equivalent model of the tension system of a multi-wire cutting machine to obtain the direct tension control model of the multi-wire cutting machine is as follows: First, establish the basic constraint relationship between linear velocity and angular velocity. The linear velocity and angular velocity of the wire-laying motor, main motor, and take-up motor satisfy the following: Linear velocity of the wire feeding motor ; Main motor linear speed ; Linear speed of the take-up motor ; Secondly, it was determined that the radius of the pay-off reel decreases with running time, while the radius of the take-up reel increases with running time; that is, the time-varying law of the radius is as follows: ， ， In the formula, Indicates line thickness; and Indicates the initial radius; Then, combining the physical parameters of the yarn, the expression for the real-time rotational inertia of the take-up and pay-off reels as a function of the reel diameter is determined, i.e. In the formula, Indicates the density of the line; Indicates the line width; and Indicates the initial moment of inertia; Finally, the linear velocity-angular velocity constraint relationship, the time-varying law of radius, and the time-varying expression of moment of inertia are substituted into the equivalent dynamic model of the tension system. The dynamic equations are differentiated, redundant intermediate variables are eliminated, and like terms are combined. Finally, a direct tension control model that can directly realize tension closed-loop control is derived.

5. The tension control method for a multi-wire cutting machine based on a fixed-time sliding mode according to claim 4, characterized in that, The expression for the direct tension control model of the multi-wire cutting machine is: in, ， ， ， ， ， In the formula, h represents the line thickness.

6. The tension control method for a multi-wire cutting machine based on a fixed-time sliding mode according to claim 5, characterized in that, The expression for the fixed-time sliding surface of the wire feeding motor is: In the formula, This indicates the tracking error of the wire tension. This represents the actual value of the wire tension. This represents the given wire tension. , , and It is a constant; The expression for the fixed-time sliding mode reaching law of the wire feeding motor is: In the formula, , and It is a constant; The expression for the control law of the wire feeding motor is: 。 7. The tension control method for a multi-wire cutting machine based on a fixed-time sliding mode according to claim 6, characterized in that, The expression for the fixed-time sliding surface of the take-up motor is: In the formula, This indicates the tracking error of the take-up tension; This represents the actual value of the take-up tension; Indicates the given take-up tension; , , and It is a constant; The expression for the fixed-time sliding mode reaching law of the take-up motor is: In the formula, , and constant The expression for the control law of the take-up motor is: 。 8. A tension control system for a multi-wire cutting machine based on a fixed-time sliding mode, characterized in that, The system is used to implement the tension control method for a multi-wire cutting machine based on a fixed-time sliding mode as described in any one of claims 1-7, and the control system includes: The model building module is used to establish an equivalent model of the tension system of the multi-wire cutting machine, and to transform the equivalent model to obtain the direct tension control model of the multi-wire cutting machine. The main motor control module is used to introduce a fixed-time sliding surface of the main motor based on the direct tension control model, design a fixed-time sliding mode approaching law of the main motor, and obtain the control law of the main motor by combining the fixed-time sliding surface of the main motor and the fixed-time sliding mode approaching law of the main motor. The wire feeding motor control module is used to introduce a fixed-time sliding surface of the wire feeding motor based on the direct tension control model, design a fixed-time sliding surface approach law of the wire feeding motor, and combine the fixed-time sliding surface of the wire feeding motor and the fixed-time sliding surface approach law of the wire feeding motor to obtain the control law of the wire feeding motor. The take-up motor control module is used to introduce a fixed-time sliding surface of the take-up motor based on the direct tension control model, design a fixed-time sliding mode approaching law of the take-up motor, and obtain the control law of the take-up motor by combining the fixed-time sliding surface of the take-up motor and the fixed-time sliding mode approaching law of the take-up motor. The tension control execution module is used to control the tension of the multi-wire cutting machine during operation by coordinating the control laws of the main motor, the wire feeding motor, and the wire take-up motor.

9. A non-volatile computer storage medium, characterized in that, The device stores computer-executable instructions configured to implement the tension control method for a multi-wire cutting machine based on a fixed-time sliding mode as described in any one of claims 1-7.

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