Fuel cell anode supply control method based on non-singular terminal sliding mode, medium

Abstract

The application discloses a fuel cell anode supply control method and medium based on a non-singular terminal sliding mode, and belongs to the field of power supply devices. The method comprises the following steps: for a fuel cell system, a spatial state equation of a fuel cell stack and an anode supply system based on mass conservation and electrochemical principles is established; based on the spatial state equation, a solenoid valve controller based on a sliding mode is designed, and a hydrogen circulating pump controller based on a non-singular terminal sliding mode is designed; and the solenoid valve controller and the hydrogen circulating pump controller are coupled into a composite sensor to cooperatively control anode supply of the fuel cell system. Through accurate regulation of hydrogen supply and hydrogen recirculation of the fuel cell anode, the application effectively improves the efficiency, stability and service life of the fuel cell.

Description

Technical Field

[0001] This invention relates to the field of power supply device technology, and more specifically, to a fuel cell anode supply control method and medium based on non-singular terminal sliding mode. Background Technology

[0002] In recent years, with the acceleration of the global energy transition, hydrogen energy and fuel cell technology have become an important path for the low-carbon development of the transportation sector. Hydrogen is abundant in the universe, and its high energy density and zero-carbon emission characteristics during utilization have made it widely regarded as a key direction for addressing climate change and promoting a clean energy structure transition. Compared to traditional fossil fuels, hydrogen fuel cells offer low emissions, low noise, and high energy conversion efficiency during operation, giving them significant advantages in applications such as transportation power systems and distributed power generation.

[0003] Despite the advantages of hydrogen fuel cells, they still face numerous technical challenges in practical applications, especially at the system control level. Hydrogen fuel cell systems exhibit strong nonlinearity, multivariable coupling, and complex dynamic responses, posing significant difficulties for control system design. As a critical component of the system, the performance of the hydrogen supply subsystem directly affects the stack's operating efficiency, output performance, and lifespan.

[0004] In existing technologies, anode hydrogen supply systems mainly operate in three modes: direct emission mode, dead-end mode, and recirculation mode. Direct emission mode has been gradually phased out due to its low hydrogen utilization rate and significant waste. Dead-end mode achieves partial reuse of unreacted hydrogen through exhaust valves, but it struggles to effectively remove impurities such as nitrogen and liquid water during long-term operation, easily leading to flow channel blockage and affecting system performance. Therefore, research focus has gradually shifted to recirculation mode. This mode uses auxiliary components such as hydrogen circulation pumps or ejectors to return unreacted hydrogen to the anode inlet of a proton exchange membrane fuel cell (PEMFC), thereby significantly improving hydrogen utilization efficiency and enhancing the stack's hydrothermal management capabilities and output stability.

[0005] Optimizing hydrogen recirculation and purging strategies plays a crucial role in improving the fuel economy and operating efficiency of fuel cell systems. However, the anode hydrogen recirculation system is itself a multiple-input multiple-output (MIMO) system with strong coupling and nonlinear characteristics, making it difficult for traditional distributed control methods to achieve coordinated control of hydrogen flow and pressure. Furthermore, uncertainties in the system's internal state and external load disturbances further increase control complexity, impacting the system's dynamic response performance and operational stability.

[0006] In summary, improvements to existing technologies are needed to enhance the dynamic response and operational stability of hydrogen circulation systems. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a fuel cell anode supply control method and medium based on non-singular terminal sliding mode.

[0008] According to a first aspect of the present invention, a method for controlling the anode supply of a fuel cell based on non-singular terminal sliding mode is provided. The method includes the following steps:

[0009] For fuel cell systems, a space state equation for the fuel cell stack and anode supply system is established based on the principles of mass conservation and electrochemistry.

[0010] Based on the aforementioned spatial state equation, a sliding mode-based electromagnetic valve controller and a non-singular terminal sliding mode-based hydrogen circulation pump controller are designed. The electromagnetic valve controller is used to maintain steady-state control of the internal chemical reaction, and the hydrogen circulation pump controller is used to control the ratio of hydrogen entering the anode to hydrogen consumed.

[0011] The electromagnetic valve controller and the hydrogen circulation pump controller are coupled into a composite sensor to collaboratively control the anode supply of the fuel cell system.

[0012] According to a second aspect of the present invention, a computer-readable storage medium is provided having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the steps of the above-described fuel cell anode supply control method based on non-singular terminal sliding mode.

[0013] Compared with the prior art, the advantages of the present invention are mainly reflected in the following aspects:

[0014] 1) In the solenoid valve control stage, due to its relatively relaxed requirements for dynamic response accuracy, the sliding mode control method still exhibits significant advantages over traditional PID control, specifically including stronger robustness, lower response delay, and better noise suppression capabilities, while requiring less computational resources from the controller. For the hydrogen circulation pump, the controlled object, its control system possesses complex characteristics such as multivariable coupling and nonlinearity, making it difficult for traditional motor control strategies to meet its accuracy and stability requirements. Therefore, the circulation pump controller designed in this invention adopts a non-singular terminal sliding mode structure as its core control algorithm. Compared to traditional terminal sliding mode control, this structure, while inheriting its advantages such as finite-time convergence and high-precision tracking, effectively solves the problem of singular control variables, further improving the system's adaptability and control robustness under parameter uncertainty and external disturbance conditions.

[0015] 2) This invention constructs a hydrogen supply control architecture suitable for dynamic load conditions, which can efficiently coordinate hydrogen supply and anode recirculation processes, significantly improving system response speed and operational stability. This framework has good environmental adaptability and can be widely applied to fuel cell systems in extreme environments such as high altitudes, low temperatures, and confined spaces, demonstrating strong engineering practical value.

[0016] 3) This invention establishes a voltage mechanism model for fuel cell stacks, and the accuracy of the model has been verified by experimental data.

[0017] Other features and advantages of the invention will become clear from the following detailed description of exemplary embodiments of the invention with reference to the accompanying drawings. Attached Figure Description

[0018] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments of the invention and, together with their description, serve to explain the principles of the invention.

[0019] Figure 1 This is a flowchart of a fuel cell anode supply control method based on non-singular terminal sliding mode according to an embodiment of the present invention;

[0020] Figure 2 This is a structural diagram of a fuel cell system according to an embodiment of the present invention;

[0021] Figure 3 This is a voltage model polarization curve verification diagram according to an embodiment of the present invention;

[0022] Figure 4 This is a schematic diagram of a fuel cell anode supply control method based on non-singular terminal sliding mode according to an embodiment of the present invention.

[0023] Figure 5 This is a schematic diagram of the input current according to an embodiment of the present invention;

[0024] Figure 6 This is a schematic diagram of the pressure control error signal of a solenoid valve according to an embodiment of the present invention;

[0025] Figure 7 This is a schematic diagram of the hydrogen peroxide ratio control error signal according to an embodiment of the present invention;

[0026] Figure 8 This is a schematic diagram of the output voltage according to an embodiment of the present invention. Detailed Implementation

[0027] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention.

[0028] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the invention or its application or use.

[0029] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0030] In all the examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0031] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.

[0032] See Figure 1 As shown, the provided fuel cell anode supply control method based on non-singular terminal sliding mode includes the following steps:

[0033] Step S1: Establish the spatial state equations of the fuel cell stack and anode supply system based on the principles of mass conservation and electrochemistry.

[0034] For example, firstly, a fuel cell stack mechanism model is established based on the principles of electrochemical reaction and heat and mass transfer. Then, based on the gas law of state and the law of conservation of energy, a state model of the anode supply system and its auxiliary systems is constructed (see [reference]). Figure 2 As shown.

[0035] The ideal voltage of a single fuel cell is defined as:

[0036] (1)

[0037] In the formula a and b It is a constant. P H2 and P O2 These represent the partial pressures of hydrogen and oxygen inside the PEMFC. T st This refers to the internal temperature of the fuel cell stack.

[0038] The activation loss voltage is defined as:

[0039] (2)

[0040] In the middle of the formula , , and These are the empirical coefficients of the corresponding terms. I st It is the input current. C O2 It is the concentration of oxygen at the anode. This refers to the internal temperature of the fuel cell stack.

[0041] The expression for the ohmic loss voltage is:

[0042] (3)

[0043] In the formula R C and R M The equivalent resistances of the electron channel and the proton channel are respectively. ).

[0044] The concentration gradient voltage loss can be expressed as:

[0045] (4)

[0046] In the formula I st,max This is the maximum input stack current; c 2=2 is the concentration voltage loss constant; c 1. The calculation is related to the internal temperature and oxygen partial pressure of the fuel cell stack. A is the area of ​​the proton exchange membrane.

[0047] Based on this, the output voltage of a single fuel cell can be expressed as:

[0048] (5)

[0049] like Figure 3 As shown, the established voltage model polarization curve is consistent with the experimental data from the University of Electronic Science and Technology of China. Zhu,Y.; Zou, J.; Li, S.; Peng, C. An Adaptive Sliding Mode Observer Based Near- Optimal OER Tracking Control Approach for PEMFCunderDynamicOperation Condition. Int. J. Hydrogen Energy 2022, 47, 1157–1171. The model error is within an acceptable range.

[0050] The output voltage of the fuel cell stack is:

[0051] (6)

[0052] In the formula n This represents the number of fuel cell units per stack.

[0053] 2) The state model of the anode supply system and its auxiliary systems is constructed as follows:

[0054] The internal pressure of the anode in a fuel cell can be expressed as:

[0055] (7)

[0056] (8)

[0057] In the formula The hydrogen pressure at the anode of the fuel cell stack. This refers to the steam pressure at the anode of the fuel cell stack. For the anode flow channel volume, , These are the molar masses of hydrogen gas and water vapor, respectively. The mass flow rate of hydrogen entering the anode, To determine the hydrogen mass flow rate at the anode, The mass flow rate of water vapor entering the anode, To discharge the anode water vapor mass flow rate, This represents the mass flow rate of water in the internal membrane of the fuel cell stack. F It is Faraday's constant. R is the ideal gas constant.

[0058] The pressure in the fuel cell anode supply line can be expressed as:

[0059] (9)

[0060] (10)

[0061] In the formula To supply hydrogen pressure to the anode manifold, To supply steam pressure to the anode in the manifold, Supply manifold volume to the anode, T sm To supply manifold temperature to the anode, To determine the hydrogen mass flow rate entering the anode supply manifold, To discharge the hydrogen mass flow rate from the anode supply manifold, The mass flow rate of hydrogen gas entering the anode supply manifold via the circulating pump, To discharge the mass flow rate of water vapor supplied to the anode manifold, The mass flow rate of water vapor supplied to the anode manifold via the circulating pump.

[0062] The pressure in the fuel cell anode discharge line can be expressed as:

[0063] (11)

[0064] (12)

[0065] In the formula The hydrogen pressure in the anode discharge pipeline. The pressure of water vapor in the anode discharge pipeline. This represents the volume of the anode discharge pipeline. T rm To supply manifold temperature to the anode, The mass flow rate of hydrogen entering the anode discharge pipeline, The mass flow rate of water vapor entering the anode discharge pipeline, To discharge the hydrogen mass flow rate of the fuel cell system, To determine the mass flow rate of water vapor discharged from the fuel cell system.

[0066] The hydrogen circulation pump model can be represented as:

[0067] (13)

[0068] (14)

[0069] In the formula This refers to the recirculation pump motor speed. For the circulation pump flow rate ( ), P sm To supply manifold pressure ( ), P rm To release pipeline pressure ( ), This indicates the input voltage of the circulating pump motor. It is the mechanical efficiency of the electric motor. It refers to compressor efficiency. R cm It is the internal resistance of the compressor motor. It is the compressor inertia. C p , , , 、k t 、k v These are parameters related to the circulating pump. , , , It is a function related to circulating pumps. γ It is a constant related to air.

[0070] The solenoid valve model can be represented as:

[0071] (15)

[0072] In the formula A T and C D It is a constant related to air. u v For the solenoid valve opening, The pressure after depressurization of the hydrogen storage tube.

[0073] Based on this, the equation of state for the anode supply of a fuel cell can be expressed as follows:

[0074] (16)

[0075] In the formula x 1. x 2. x 3. x 4. x 5. x 6. x 7 represents the hydrogen and water vapor pressure in the anode supply manifold, the hydrogen and water vapor pressure in the anode, the hydrogen and water vapor pressure in the anode discharge line, and the speed of the circulating pump motor, respectively. f 1 and f 2 is a function related to state variables. W purge It is a pulse shut-off valve model. c 1 to c 17 These are system-dependent constants.

[0076] Furthermore, the space state equation can be expressed as:

[0077] (17)

[0078] In the formula, u =( u c , u v ) is the control input matrix, x It is a state variable. y 1= P sm It is supply manifold pressure, y 2= The excess hydrogen ratio is defined as the ratio of hydrogen entering the anode to hydrogen consumed. y Indicates the output. t Indicates the time.

[0079] Step S2: Based on the state equation of the anode supply system, design a sliding mode-based electromagnetic valve controller.

[0080] First, the sliding surface of the solenoid valve controller is:

[0081] (18)

[0082] In the formula For sliding mode gain, and , y 1,ref This indicates the pressure reference value. e 1 indicates the error of the electromagnetic valve controller.

[0083] Since the first derivative of the sliding surface of the solenoid valve controller is 0, the solenoid valve controller can be solved inversely:

[0084] (19)

[0085] in, and This indicates the set coefficient for the corresponding item.

[0086] In the formula m ( x )and n ( x ) is related to state x The relevant functions are represented as follows:

[0087] (20)

[0088] Step S3: Design a hydrogen circulation pump controller based on non-singular terminal sliding mode.

[0089] Step S3 is based on the constructed state equation of the supply system and designs a circulating pump controller based on non-singular terminal sliding mode. The introduction of nonlinear terms in the non-singular terminal sliding mode allows the system state to converge precisely to zero in a finite time, while avoiding the singularity problem that may be caused by general terminal sliding mode.

[0090] The sliding mode variable design of the hydrogen circulation pump controller is as follows:

[0091] (twenty one)

[0092] In the formula, , i and j It is a positive odd number and satisfies ,and This is the non-singular terminal sliding mode gain. This represents a reference value for the ratio of hydrogen entering the anode to hydrogen consumed. e 2 indicates the error of the hydrogen circulation pump controller.

[0093] Similarly, by setting the first derivative of the non-singular terminal sliding surface of the hydrogen circulation pump controller to 0, the hydrogen circulation pump controller can be solved inversely:

[0094] (twenty two)

[0095] In the formula, and This indicates the set coefficient for the corresponding item. p ( x )and q ( x ) is a state variable x The relevant functions are expressed as follows:

[0096] (twenty three)

[0097] In the formula .

[0098] Step S4: Couple the circulating pump controller and the solenoid valve controller into a stable composite controller to coordinate the control of the fuel cell anode supply.

[0099] In step S4, the circulating pump controller and the solenoid valve controller are coupled into a composite controller for coordinated control of the fuel cell anode supply. Furthermore, a stability assessment can be performed on this composite controller.

[0100] Lyapunov function v Designed as follows:

[0101] (twenty four)

[0102] right v Differentiating, we get:

[0103] (25)

[0104] Obviously v >0, dv< 0, therefore the control law satisfies Lyapunov's stability theorem, meaning the proposed coordinated controller is theoretically stable, and the final control architecture is as follows. Figure 4 As shown.

[0105] In the simulation, the step input current is as follows: Figure 5 As shown, the corresponding solenoid valve pressure control error signal is as follows: Figure 6 As shown, even ordinary sliding mode controllers exhibit strong response speed and ultra-low response delay in the face of sudden current changes. The corresponding hydrogen ratio control error signal is as follows: Figure 7As shown, the designed solenoid valve controller based on a conventional sliding mode controller and a non-singular terminal sliding mode controller effectively ensures the anode hydrogen supply during fuel cell stack operation, especially under conditions of sudden current changes. Figure 7 The medium-pulse overshoot is caused by the opening and closing of the pulse cutoff valve. It is precisely because the designed composite controller possesses strong performance and robustness that... Figure 8 As shown, the anode supply control method established by this invention effectively ensures that the stack voltage can be effectively changed to the corresponding steady-state voltage output under the condition of sudden current change.

[0106] In summary, this invention provides a fuel cell anode supply control method based on non-singular terminal sliding mode, involving coordinated control technology of solenoid valves and circulating pumps in the fuel cell anode supply circuit. Compared with existing technologies, this invention effectively solves the problem of rapid response adjustment of anode hydrogen supply under power variation conditions, while improving hydrogen utilization efficiency and overcoming the shortcomings of existing control strategies such as response lag and low hydrogen utilization. This invention significantly enhances the control accuracy and robustness of the system, effectively improving the efficiency, stability, and service life of the fuel cell through precise regulation of fuel cell anode hydrogen supply and hydrogen recirculation.

[0107] This invention can be a system, method, and / or computer program product. A computer program product may include a computer-readable storage medium having computer-readable program instructions loaded thereon for causing a processor to implement various aspects of the invention.

[0108] Computer-readable storage media can be tangible devices capable of holding and storing instructions for use by an instruction execution device. Computer-readable storage media can be, for example, but not limited to, electrical storage devices, magnetic storage devices, optical storage devices, electromagnetic storage devices, semiconductor storage devices, or any suitable combination thereof. More specific examples (a non-exhaustive list) of computer-readable storage media include: portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static random access memory (SRAM), portable compact disc read-only memory (CD-ROM), digital multifunction disc (DVD), memory sticks, floppy disks, mechanical encoding devices, such as punch cards or recessed protrusions storing instructions thereon, and any suitable combination thereof. The computer-readable storage media used herein are not to be construed as transient signals themselves, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through waveguides or other transmission media (e.g., light pulses through fiber optic cables), or electrical signals transmitted through wires.

[0109] The computer-readable program instructions described herein can be downloaded from computer-readable storage media to various computing / processing devices, or downloaded via a network, such as the Internet, local area network, wide area network, and / or wireless network, to an external computer or external storage device. The network may include copper transmission cables, fiber optic transmission, wireless transmission, routers, firewalls, switches, gateway computers, and / or edge servers. A network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards them to the computer-readable storage media in the respective computing / processing device.

[0110] The computer program instructions used to perform the operations of this invention may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, state setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Smalltalk, C++, Python, etc., and conventional procedural programming languages ​​such as "C" or similar languages. The computer-readable program instructions may be executed entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving a remote computer, the remote computer may be connected to the user's computer via any type of network—including a local area network (LAN) or a wide area network (WAN)—or may be connected to an external computer (e.g., via the Internet using an Internet service provider). In some embodiments, electronic circuitry, such as programmable logic circuitry, field-programmable gate arrays (FPGAs), or programmable logic arrays (PLAs), is personalized by utilizing state information from the computer-readable program instructions. This electronic circuitry can execute the computer-readable program instructions to implement various aspects of the invention.

[0111] Various aspects of the present invention are described herein with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It should be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer-readable program instructions.

[0112] These computer-readable program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing apparatus to produce a machine such that, when executed by the processor of the computer or other programmable data processing apparatus, they create means for implementing the functions / actions specified in one or more blocks of the flowchart and / or block diagram. These computer-readable program instructions can also be stored in a computer-readable storage medium that causes a computer, programmable data processing apparatus, and / or other device to operate in a particular manner; thus, the computer-readable medium storing the instructions comprises an article of manufacture that includes instructions for implementing aspects of the functions / actions specified in one or more blocks of the flowchart and / or block diagram.

[0113] Computer-readable program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other device to cause a series of operational steps to be performed on the computer, other programmable data processing apparatus, or other device to produce a computer-implemented process, thereby causing the instructions executed on the computer, other programmable data processing apparatus, or other device to perform the functions / actions specified in one or more boxes of a flowchart and / or block diagram.

[0114] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of an instruction containing one or more executable instructions for implementing a specified logical function. In some alternative implementations, the functions marked in the blocks may occur in a different order than those marked in the drawings. For example, two consecutive blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, can be implemented using a dedicated hardware-based system that performs the specified function or action, or using a combination of dedicated hardware and computer instructions. It will be known to those skilled in the art that implementation in hardware, implementation in software, and implementation using a combination of software and hardware are equivalent.

[0115] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, and are not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or technical improvements to the embodiments in the market, or to enable others skilled in the art to understand the embodiments disclosed herein. The scope of the invention is defined by the appended claims.

Claims

1. A fuel cell anode supply control method based on non-singular terminal sliding mode, characterized in that, Includes the following steps: For fuel cell systems, a space state equation for the fuel cell stack and anode supply system is established based on the principles of mass conservation and electrochemistry. Based on the aforementioned spatial state equation, a sliding mode-based electromagnetic valve controller and a non-singular terminal sliding mode-based hydrogen circulation pump controller are designed. The electromagnetic valve controller is used to maintain steady-state control of the internal chemical reaction, and the hydrogen circulation pump controller is used to control the ratio of hydrogen entering the anode to hydrogen consumed. The electromagnetic valve controller and the hydrogen circulation pump controller are coupled into a composite sensor to collaboratively control the anode supply of the fuel cell system. The spatial state equation is expressed as: in, y It is the output. u =( u c , u v ) is the control input signal matrix, y 2= It is the ratio of hydrogen entering the anode to hydrogen consumed. y 1= P sm It is the pressure of the supply manifold. x Represents state variables. u c It's a signal from the hydrogen circulation pump controller. u v It is a signal from the solenoid valve controller. t Indicates time; The signal of the electromagnetic valve controller is represented as follows: in, and It is related to state quantity x The relevant functions, and This indicates the set coefficient for the corresponding item. s 1 is the sliding surface of the electromagnetic valve controller; The signal of the hydrogen circulation pump controller is represented as follows: in, p ( x )and q ( x ) is a state variable x Related functions, and This indicates the set coefficient for the corresponding item. s 2 is the sliding mode variable of the hydrogen circulation pump controller; Wherein, the sliding surface of the electromagnetic valve controller s 1 is represented as: in, It is the sliding mode gain. e 1 represents the error of the electromagnetic valve controller; Among them, the sliding mode variable of the hydrogen circulation pump controller s 2 is represented as: in, e 2 is the error of the hydrogen circulation pump controller. i and j It is a positive odd number and satisfies , It is the non-singular terminal sliding mode gain.

2. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the method according to claim 1.

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