Multi-channel solenoid valve current acquisition method and system

Abstract

This invention provides a method and system for acquiring current in a multi-channel solenoid valve, relating to the field of solenoid valve control technology. The method includes: determining the sampling duty cycle of a target PWM signal based on amplitude monitoring; the target PWM signal being a pulse signal controlling a target multi-channel solenoid valve; acquiring the sampling temperature value of the environment where the target multi-channel solenoid valve is located; determining a target functional relationship based on the sampling temperature value and a preset correspondence table; the target functional relationship being a function between the current value of the target PWM signal and the duty cycle; the target functional relationship including temperature-related target parameters; and the preset correspondence table being a table showing the correspondence between the sampling temperature value and the target parameters. Based on the sampling duty cycle and the target functional relationship, the method determines the sampling current value of the multi-channel solenoid valve. This invention alleviates the technical problems of low reliability, high cost, and difficult operation in existing technologies.

Description

Technical Field

[0001] This invention relates to the field of solenoid valve control technology, and in particular to a method and system for acquiring current in a multi-channel solenoid valve. Background Technology

[0002] Solenoid valves are key components in the hydraulic control systems of automotive transmissions. They change the control pressure by altering the magnitude of the control current, which in turn moves the valve spool. The spool displacement or thrust is positively correlated with the current. Therefore, accurately acquiring the control current value of the solenoid valve is crucial for analyzing changes in control pressure. The solenoid valve is an inductive load, controlled using PWM (Pulse Width Modulation) technology.

[0003] Existing current sampling technology for multi-channel solenoid valves requires disrupting the internal structure of the original gearbox and solenoid valve, and installing voltage or resistance measurement circuits inside the solenoid valve. This is prone to failure, has low reliability, high cost, and is difficult to operate. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a method and system for acquiring current of a multi-channel solenoid valve, so as to alleviate the technical problems of low reliability, high cost and difficult operation in the prior art.

[0005] In a first aspect, embodiments of the present invention provide a method for acquiring current of a multi-channel solenoid valve, comprising: determining the sampling duty cycle of a target PWM signal based on amplitude monitoring; the target PWM signal being a pulse signal controlling a target multi-channel solenoid valve; acquiring the sampling temperature value of the environment in which the target multi-channel solenoid valve is located; determining a target functional relationship based on the sampling temperature value and a preset correspondence table; the target functional relationship being a functional relationship between the current value of the target PWM signal and the duty cycle; the target functional relationship including temperature-related target parameters; the preset correspondence table being a correspondence table between the sampling temperature value and the target parameters; and determining the sampling current value of the multi-channel solenoid valve based on the sampling duty cycle and the target functional relationship.

[0006] Furthermore, based on the amplitude monitoring of the target PWM signal, the sampling duty cycle of the target PWM signal is determined, including: monitoring the amplitude of the negative PWM signal of the target multi-channel solenoid valve, and the time interval from the occurrence of the rising edge to the occurrence of the falling edge is the first time interval; the ratio of the first time interval to the period of the target PWM signal is used as the sampling duty cycle.

[0007] Furthermore, the objective function relationship is a linear function relationship; the objective parameters include slope and intercept; the preset correspondence table is a correspondence table between the sampled temperature value and the slope and intercept; the method further includes: determining the objective function relationship and the preset correspondence table through temperature change experiments.

[0008] Furthermore, after determining the sampling current value of the multi-channel solenoid valve, the method further includes: filtering the sampling current value based on the dithering period of the target PWM signal to obtain a filtered average current value; and correcting the filtered average current value to obtain a corrected current value.

[0009] Further, based on the dithering period of the target PWM signal, the sampled current value is filtered to obtain a filtered average current value, including: calculating the maximum and minimum values ​​of the sampled current value in each dithering period in the n dithering periods before the current time, to obtain n maximum current values ​​and n minimum current values; n is a preset positive integer; calculating the average of the n maximum current values ​​and the average of the n minimum current values, to obtain a first average current value and a second average current value; and taking the average of the first average current value and the second average current value as the filtered average current value.

[0010] Further, error correction is performed on the filtered average current value to obtain a corrected current value, including: determining the filtered average current value of the solenoid valve in the multi-channel solenoid valve that is in the maximum current operating state as the maximum filtered current value; determining the ratio of the preset theoretical current value to the maximum filtered current value as the error correction coefficient; and performing error correction on the filtered average current value based on the error correction coefficient to obtain the corrected current value.

[0011] Secondly, embodiments of the present invention also provide a multi-channel solenoid valve current acquisition system, comprising: a monitoring module, an acquisition module, a first determination module, and a second determination module; wherein, the monitoring module is used to determine the sampling duty cycle of the target PWM signal based on amplitude monitoring of the target PWM signal; the target PWM signal is a pulse signal controlling the target multi-channel solenoid valve; the acquisition module is used to acquire the sampling temperature value of the environment where the target multi-channel solenoid valve is located; the first determination module is used to determine a target function relationship based on the sampling temperature value and a preset correspondence table; the target function relationship is a function relationship between the current value of the target PWM signal and the duty cycle; the target function relationship includes temperature-related target parameters; the preset correspondence table is a correspondence table between the sampling temperature value and the target parameters; the second determination module is used to determine the sampling current value of the multi-channel solenoid valve based on the sampling duty cycle and the target function relationship.

[0012] Furthermore, it also includes: a filtering module and a correction module; wherein, the filtering module is used to filter the sampled current value based on the jitter period of the target PWM signal to obtain a filtered average current value; the correction module is used to correct the error of the filtered average current value to obtain a corrected current value.

[0013] Thirdly, embodiments of the present invention also provide an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the method described in the first aspect above.

[0014] Fourthly, embodiments of the present invention also provide a computer-readable medium having processor-executable non-volatile program code, the program code causing the processor to perform the method described in the first aspect above.

[0015] This invention provides a method and system for acquiring current from a multi-channel solenoid valve. By measuring the duty cycle of the solenoid valve's PWM signal and then utilizing the duty current relationship of the solenoid valve at different temperatures, the sampling current value of the multi-channel solenoid valve is determined. The solution provided by this invention is simple in principle, low in cost, easy to install, and does not damage the original structure of the gearbox, alleviating the technical problems of low reliability, high cost, and difficult operation in existing technologies. Attached Figure Description

[0016] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 A flowchart of a multi-channel solenoid valve current acquisition method provided in this embodiment of the invention;

[0018] Figure 2 A schematic diagram of a PWM signal provided in an embodiment of the present invention;

[0019] Figure 3 This is a schematic diagram of the connection of a monitoring device provided in an embodiment of the present invention;

[0020] Figure 4 A flowchart of an error correction method provided in an embodiment of the present invention;

[0021] Figure 5 A schematic diagram of a multi-channel solenoid valve current acquisition system provided in an embodiment of the present invention;

[0022] Figure 6 This is a schematic diagram of another multi-channel solenoid valve current acquisition system provided in an embodiment of the present invention. Detailed Implementation

[0023] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Example 1:

[0025] Figure 1 This is a flowchart illustrating a multi-channel solenoid valve current acquisition method according to an embodiment of the present invention. Figure 1 As shown, the method specifically includes the following steps:

[0026] Step S102: Based on the amplitude monitoring of the target PWM signal, determine the sampling duty cycle of the target PWM signal; the target PWM signal is the pulse signal that controls the target multi-channel solenoid valve.

[0027] Specifically, the amplitude of the negative PWM signal of the target multi-channel solenoid valve is monitored, and the time interval from the appearance of the rising edge to the appearance of the falling edge is the first time interval; the ratio of the first time interval to the period of the target PWM signal is used as the sampling duty cycle.

[0028] Step S104: Collect the sampling temperature value of the environment where the target multi-channel solenoid valve is located.

[0029] Optionally, in this embodiment of the invention, the collected temperature signal of the solenoid valve lubricating oil is used as the current sampling temperature value of the solenoid valve.

[0030] Step S106: Determine the target function relationship based on the sampled temperature value and the preset correspondence table; the target function relationship is the function relationship between the current value and the duty cycle of the target PWM signal; the target function relationship includes target parameters related to temperature; the preset correspondence table is the correspondence table between the sampled temperature value and the target parameters.

[0031] Optionally, in this embodiment of the invention, the objective function relationship is a linear function relationship; the objective parameters include the slope and the intercept; the preset correspondence table is a correspondence table between the sampled temperature value and the slope and the intercept; the method further includes: determining the objective function relationship and the preset correspondence table through a temperature change experiment.

[0032] Step S108: Determine the sampling current value of the multi-channel solenoid valve based on the sampling duty cycle and the objective function relationship.

[0033] This invention provides a method for acquiring current from a multi-channel solenoid valve. By measuring the duty cycle of the solenoid valve's PWM signal and then utilizing the duty current relationship of the solenoid valve at different temperatures, the sampling current value of the multi-channel solenoid valve is determined. The solution provided by this invention is simple in principle, low in cost, easy to install, and does not damage the original structure of the gearbox, alleviating the technical problems of low reliability, high cost, and difficult operation in existing technologies.

[0034] In this embodiment of the invention, a dedicated development board is used to convert the PWM waveform into a duty cycle signal. Figure 2 This is a schematic diagram of a PWM signal provided according to an embodiment of the present invention. Figure 2 As shown, the amplitude of the PWM signal at the negative terminal of the solenoid valve is monitored. Timing begins when a rising edge is detected, and time t1 is recorded when a falling edge is detected. Given that the PWM signal period is t2, the duty cycle at the current moment is t1 / t2. A dedicated development board converts the PWM waveform into duty cycle data and acquires it via CAN signal (but not limited to CAN signal) to the computer. The device connection method is as follows: Figure 3 As shown, where, Figure 3 This is a schematic diagram of a monitoring device connection according to an embodiment of the present invention.

[0035] Because the resistance of a solenoid valve changes significantly with temperature, the duty cycle also changes with temperature under the same current. To obtain an accurate duty cycle-current relationship, it is necessary to test the duty cycle-current relationship of the solenoid valve at different temperatures through temperature change experiments.

[0036] Specifically, the solenoid valve and temperature sensor are immersed together in lubricating oil and placed in a temperature change test chamber, where the temperature is slowly increased from -30℃ to 80℃. As the lubricating oil temperature, as shown by the temperature sensor, rises from -30℃ to 80℃ with the ambient temperature, the solenoid valve's duty cycle is controlled by a microcontroller to increase from 5% to 50%, and the current value is recorded. This results in a table showing the duty cycle-current relationship of the multi-channel solenoid valve at different temperatures. Based on this table, the duty cycle data acquired and processed by the dedicated development board used in this invention can be converted into current values. Specifically, the process includes the following steps:

[0037] Step 1: Calculate Temp for each temperature i Down current I i PWM with duty cycle i The changing trend of I can be observed through experiments to be a linear function relationship (i.e., the objective function relationship mentioned above): i =k i ×PWM i +bi Among them, I i Represents current, PWM i k represents the duty cycle. i b represents the coefficient (i.e., the slope). i Representing the intercept, we obtain Temp. i —k i —b i Correspondence table (i.e., the aforementioned preset correspondence table);

[0038] Step 2: Based on the collected lubricating oil temperature signal Temp ATF Temperature (Temp) of current multi-channel solenoid valves x (i.e., the sampled temperature value), perform one interpolation on the table above, but not limited to one interpolation method, to obtain the current temperature Temp. x The coefficient k x and intercept b x The sampled current value is calculated as: I x =k x ×PWM x +b x Among them, PWM x This refers to the sampling duty cycle.

[0039] Optionally, the multi-channel solenoid valve current acquisition method provided in this embodiment of the invention further includes filtering and correction of the sampled current.

[0040] The filtering of the sampled current includes: filtering the sampled current value based on the dithering period of the target PWM signal to obtain the filtered average current value.

[0041] Specifically, the maximum and minimum values ​​of the sampled current values ​​are calculated in each of the n flutter cycles prior to the current time, resulting in n maximum current values ​​and n minimum current values; n is a preset positive integer; the average of the n maximum current values ​​and the average of the n minimum current values ​​are calculated to obtain the first average current value and the second average current value; the average of the first average current value and the second average current value is used as the filtered average current value.

[0042] In this embodiment of the invention, since the solenoid valve control includes chatter control, the sampled current value has a chatter period Freq_Hz and a chatter amplitude Ampl_mA. The actual current value fluctuates based on the chatter period and the chatter amplitude. The collected data needs to be filtered.

[0043] Specifically, the filtering method proposed in this embodiment of the invention is as follows: calculate the average of the n maximum values ​​within the most recent n periods. The average of the minimum and minimum values Then calculate the average value I of the two. avg =(I max +I min )÷2, and I avg This serves as the average current value for filtering. In this embodiment of the invention, the number of cycles n is 5, but not limited to 5. Too many cycles result in small fluctuations in the filtered value but poor tracking performance, while too few cycles result in large fluctuations in the filtered value but good tracking performance.

[0044] The filtering method provided in this embodiment of the invention has poor tracking performance when the duty cycle change rate is large. To address this issue, this invention proposes a solution: setting a threshold value Thr for the duty cycle change rate. PWM When the rate of change of the duty cycle does not exceed the threshold value Thr PWM When the threshold Thr is exceeded, the filtering method provided in this embodiment of the invention is applied; PWM When the current period's maximum value I is reached, it is directly taken. max and minimum value I min The average value I avg =(I max +I min )÷2.

[0045] Finally, the average current value of the filter is corrected for error to obtain the corrected current value.

[0046] Specifically, the average filtered current value of the solenoid valve in the multi-channel solenoid valve operating at maximum current is determined as the maximum filtered current value; the ratio of the preset theoretical current value to the maximum filtered current value is determined as the error correction coefficient; the average filtered current value is corrected based on the error correction coefficient to obtain the corrected current value.

[0047] In this embodiment of the invention, there is a difference between the actual temperature of the solenoid valve and the lubricating oil temperature. Therefore, this embodiment also provides a method to eliminate the error, such as... Figure 4 As shown, Figure 4 This is a flowchart of an error correction method provided according to an embodiment of the present invention. First, the filtered average current value I of the current solenoid valve current is calculated using the method provided in the embodiment of the present invention. avg Then, set the current theoretical current value I. bench (i.e., the aforementioned preset theoretical current value), based on engineering experience, the maximum control current varies among different types of solenoid valves, and the theoretical current value I... bench The current can be set to 850mA, but is not limited to 850mA; in this invention, at least one of the solenoid valves is always in the maximum current operating state, and the maximum current value I is taken. max Calculate the theoretical current value I bench With the maximum current value I max The ratio R = I bench ÷Imax Finally, this ratio is used as a correction factor to multiply all current values ​​I. avg The corrected current value I can then be obtained. final =I avg ×R.

[0048] As described above, the multi-channel solenoid valve current acquisition device provided in this embodiment of the invention takes into account the influence of temperature on the resistance of the multi-channel solenoid valve, calculates the sampling current value of the solenoid valve by utilizing the direct relationship between the duty cycle of the PWM signal and the current, and finally filters and corrects the sampling current value based on the chatter control cycle of the solenoid valve, so that the final current value obtained is more accurate.

[0049] Example 2:

[0050] Figure 5 This is a schematic diagram of a multi-channel solenoid valve current acquisition system according to an embodiment of the present invention. Figure 5 As shown, the system includes: a monitoring module 10, a data acquisition module 20, a first determination module 30, and a second determination module 40.

[0051] Specifically, the monitoring module 10 is used to determine the sampling duty cycle of the target PWM signal based on the amplitude monitoring of the target PWM signal; the target PWM signal is a pulse signal that controls the target multi-channel solenoid valve.

[0052] Specifically, the amplitude of the negative PWM signal of the target multi-channel solenoid valve is monitored, and the time interval from the appearance of the rising edge to the appearance of the falling edge is the first time interval; the ratio of the first time interval to the period of the target PWM signal is used as the sampling duty cycle.

[0053] The acquisition module 20 is used to acquire the sampling temperature value of the environment where the target multi-channel solenoid valve is located.

[0054] The first determining module 30 is used to determine the target function relationship based on the sampled temperature value and the preset correspondence table; the target function relationship is the function relationship between the current value and the duty cycle of the target PWM signal; the target function relationship includes target parameters related to temperature; the preset correspondence table is the correspondence table between the sampled temperature value and the target parameters.

[0055] Optionally, in this embodiment of the invention, the objective function relationship is a linear function relationship; the objective parameters include the slope and the intercept; the preset correspondence table is a correspondence table between the sampled temperature value and the slope and the intercept; the method further includes: determining the objective function relationship and the preset correspondence table through a temperature change experiment.

[0056] The second determining module 40 is used to determine the sampling current value of the multi-channel solenoid valve based on the sampling duty cycle and the objective function relationship.

[0057] This invention provides a multi-channel solenoid valve current acquisition system. By measuring the duty cycle of the solenoid valve's PWM signal and then utilizing the duty current relationship of the solenoid valve at different temperatures, the sampling current value of the multi-channel solenoid valve is determined. The solution provided by this invention is simple in principle, low in cost, easy to install, and does not damage the original structure of the gearbox, alleviating the technical problems of low reliability, high cost, and difficult operation in existing technologies.

[0058] Optionally, Figure 6 This is a schematic diagram of another multi-channel solenoid valve current acquisition system provided according to an embodiment of the present invention. Figure 6 As shown, the system also includes a filtering module 50 and a correction module 60.

[0059] Specifically, the filtering module 50 is used to filter the sampled current value based on the dithering period of the target PWM signal to obtain the filtered average current value.

[0060] Optionally, the filtering module 50 is further configured to calculate the maximum and minimum values ​​of the sampled current values ​​in each of the n flutter cycles prior to the current time, to obtain n maximum current values ​​and n minimum current values; n is a preset positive integer; calculate the average of the n maximum current values ​​and the average of the n minimum current values, to obtain a first average current value and a second average current value; and use the average of the first average current value and the second average current value as the filtered average current value.

[0061] The correction module 60 is used to correct the error of the filtered average current value to obtain the corrected current value.

[0062] Optionally, the correction module 60 is also used to determine the average filtered current value of the solenoid valve in the multi-channel solenoid valve that is in the maximum current operating state, which is the maximum filtered current value; to determine the ratio of the preset theoretical current value to the maximum filtered current value as the error correction coefficient; and to perform error correction on the average filtered current value based on the error correction coefficient to obtain the corrected current value.

[0063] This invention also provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the steps of the method in Embodiment 1 described above.

[0064] This invention also provides a computer-readable medium having processor-executable non-volatile program code that causes the processor to perform the method described in Embodiment 1 above.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A multi-channel solenoid valve current acquisition method, characterized by, The method comprises the following steps: determining a sampling duty cycle of a target PWM signal based on monitoring of an amplitude of the target PWM signal; the target PWM signal is a pulse signal for controlling a target multi-channel electromagnetic valve; acquiring a sampling temperature value of an environment in which the target multi-channel electromagnetic valve is located; determining a target function relationship based on the sampling temperature value and a preset corresponding relationship table; the target function relationship is a function relationship between a current value and a duty cycle of the target PWM signal; the target function relationship comprises a target parameter related to temperature; the preset corresponding relationship table is a corresponding relationship table between the sampling temperature value and the target parameter; The method for determining the objective function relationship includes: immersing the target multi-channel solenoid valve and temperature sensor together in lubricating oil, placing them in a temperature change test chamber, and slowly increasing the chamber temperature from -30℃ to 80℃; as the lubricating oil temperature displayed by the temperature sensor rises from -30℃ to 80℃ with the ambient temperature, controlling the solenoid valve's duty cycle from 5% to 50% via a microcontroller, recording the current value, and obtaining a table showing the correspondence between the duty cycle and current of the multi-channel solenoid valve at different temperatures; calculating the trend of current change with duty cycle at each temperature, and obtaining the objective function relationship: I i =k i ×PWM i +b i Among them, I i Represents current, PWM i k represents the duty cycle. i b represents the coefficient. i Indicates the intercept; determining a sampling current value of the multi-channel electromagnetic valve based on the sampling duty cycle and the target function relationship.

2. The method of claim 1, wherein, The method comprises the following steps: monitoring an amplitude of a negative PWM signal of the target multi-channel electromagnetic valve; a time interval from the occurrence of a rising edge to the occurrence of a falling edge is a first time interval; taking a ratio of the first time interval to a period of the target PWM signal as the sampling duty cycle.

3. The method of claim 1, wherein, After determining the sampling current value of the multi-channel electromagnetic valve, the method further comprises the following steps: filtering the sampling current value based on a dithering period of the target PWM signal to obtain a filtered average current value; performing error correction on the filtered average current value to obtain a corrected current value.

4. The method of claim 3, wherein, The method comprises the following steps: respectively calculating a maximum value and a minimum value of the sampling current value in each dithering cycle in n dithering cycles before the current time to obtain n maximum current values and n minimum current values; n is a preset positive integer; respectively calculating an average value of the n maximum current values and an average value of the n minimum current values to obtain a first average current value and a second average current value; taking an average value of the first average current value and the second average current value as the filtered average current value.

5. The method of claim 3, wherein, The method comprises the following steps: determining a filtered average current value of an electromagnetic valve in a maximum current working state in the multi-channel electromagnetic valve as a maximum filtered current value; determining a ratio of a preset theoretical current value to the maximum filtered current value as an error correction coefficient; performing error correction on the filtered average current value based on the error correction coefficient to obtain the corrected current value.

6. A multi-channel solenoid current acquisition system, characterized by, The method comprises the following steps: a monitoring module, an acquisition module, a first determining module and a second determining module; wherein the monitoring module is configured to determine a sampling duty cycle of a target PWM signal based on monitoring of an amplitude of the target PWM signal; the target PWM signal is a pulse signal for controlling a target multi-channel electromagnetic valve; the acquisition module is configured to acquire a sampling temperature value of an environment in which the target multi-channel electromagnetic valve is located; The first determination module is configured to determine a target function relationship based on the sampling temperature value and a preset corresponding relationship table. The target function relationship is a function relationship between a current value and a duty cycle of the target PWM signal. The target function relationship includes a target parameter related to temperature. The preset corresponding relationship table is a corresponding relationship table between the sampling temperature value and the target parameter. The determination method of the target function relationship includes: immersing a target multi-channel electromagnetic valve and a temperature sensor in lubricating oil together, placing them in a temperature change experiment box, and setting the temperature in the box to slowly increase from -30 DEG C to 80 DEG C; in the process that the temperature sensor displays that the temperature of the lubricating oil increases from -30 DEG C to 80 DEG C along with the ambient temperature, increasing the duty cycle of the electromagnetic valve from 5% to 50% through a single-chip microcomputer, recording the current value, and obtaining a corresponding relationship table of the duty cycle and the current of the multi-channel electromagnetic valve at different temperatures; calculating the change trend of the current with the duty cycle at each temperature, and obtaining the target function relationship as: I = k * PWM + b; wherein I represents the current, PWM represents the duty cycle, k represents a coefficient, and b represents an intercept. i =k i ×PWM i +b i ; wherein I i represents the current, PWM i represents the duty cycle, k i represents the coefficient, and b i represents the intercept. the second determining module is configured to determine a sampling current value of the multi-channel electromagnetic valve based on the sampling duty cycle and the target function relationship.

7. The system of claim 6, wherein, The method further comprises the following steps: a filtering module and a correction module; wherein The filter module is configured to filter the sampling current values based on a dithering period of the target PWM signal to obtain a filtered average current value. The correction module is configured to perform error correction on the filtered average current value to obtain a corrected current value.

8. An electronic device comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, The processor executes the computer program to implement the steps of the method in any one of claims 1 to 5.

9. A computer readable medium having a non-transitory program code executable by a processor, the program code comprising instructions for: The program code causes the processor to execute the method in any one of claims 1 to 5.

Images