Method for fault diagnosis in a battery system, as well as a control unit and a computer program for carrying out this method

Abstract

Method for fault diagnosis in a battery system (100), the battery system (100) comprising a battery (101), a control unit (103), a disconnecting element (104) configured to disconnect an electrical connection between the battery (101) and at least one consumer (110), and a discharge circuit (106) configured to discharge at least one energy storage device (111) of the at least one consumer (110), the method comprising the following steps: - Receiving a trigger signal (120) by means of the control unit (103) and subsequent triggering of the separating element (104); - Activating the discharge circuit (106) to perform a discharge process of the at least one energy storage device (111); - Determining a characteristic quantity for separation (121); and - Detecting whether an error occurred during separation using an evaluation criterion based on the characteristic quantity for separation (121), where the quantity characteristic for separation (121) correlates with the discharge process, wherein the characteristic quantity (121) correlated with the discharge process is determined by at least one of the following parameters: a battery temperature; a pressure, in particular a pressure within the battery management system (102) and / or a battery pressure.

Description

TECHNICAL AREA

[0001] The present disclosure relates to methods for fault diagnosis in a battery system and corresponding control units. Specifically, methods and control units are described for detecting whether a connection between a battery and a consumer is properly or incorrectly disconnected, particularly in a motor vehicle. BACKGROUND OF THE INVENTION

[0002] Modern electric vehicles and hybrid electric vehicles have high safety requirements in the event of a crash. Due to the high voltages in the high-voltage system, the battery, and the intermediate circuit, it is crucial to ensure that no dangerous, touchable voltages remain after an accident. This is achieved by rapidly disconnecting the high-voltage battery, usually mechanically via a pyrotechnic fuse, and quickly discharging the remaining energy in the system. However, if there is a problem with the mechanical disconnection of the battery and it remains connected despite the fuse being triggered, performing the rapid discharge can lead to a critical situation, as this essentially constitutes a short circuit in the battery. Possible consequences include arcing, high temperatures, and even fire.

[0003] From WO 2011 / 128 046 A1, a high-voltage system for a motor vehicle is known, comprising (i) a high-voltage battery supplying at least one load, in particular an inverter, via cables, wherein at least one switching device is provided for disconnecting the high-voltage supply, (ii) a capacitor connected in parallel with the load, and (iii) a discharge circuit for discharging the capacitor with a discharge resistor and a discharge switching device closing the discharge circuit. A diagnostic device is provided with a measuring device for measuring a voltage profile describing the voltage across the capacitor, in particular during the discharge process, and a control device for evaluating this voltage profile with regard to a malfunction of the high-voltage system.

[0004] From DE 10 2012 204 862 A1, a safety device for a high-voltage system is known, comprising (i) a coupling device which connects high-voltage components of the high-voltage system to external components in a switchable manner and which is designed to electrically disconnect the high-voltage components from the external components depending on the actuation of a safety switch, (ii) a discharge circuit which is designed to electrically discharge the high-voltage components depending on the actuation of the safety switch, and (iii) a monitoring device which is designed to monitor electrical parameters of the discharge circuit or the high-voltage components and to release the locking mechanism of a housing for the high-voltage components if at least one of the electrical parameters of the discharge circuit or the high-voltage components falls below a predetermined threshold.

[0005] German patent DE 10 2016 222 340 A1 discloses a safety method for use in a vehicle with high-current and high-voltage components, in particular a hybrid or electric vehicle. To increase safety in a crash, in addition to physically separating the battery from the HV intermediate circuit, this HV intermediate circuit is discharged.

[0006] From DE 10 2020 216 327 B3, a method for operating an inverter arranged between at least one vehicle battery and a drive motor of an electrically powered vehicle is known. The inverter can be connected to the at least one vehicle battery via an intermediate circuit, and the intermediate circuit includes at least one storage device for electrical energy as well as a discharge circuit for rapid discharge of the intermediate circuit. At the beginning of a rapid discharge of the intermediate circuit via the discharge circuit, the voltage and / or current profile at the discharge circuit is checked, and the rapid discharge is terminated if the voltage and / or current do not change as expected. SUMMARY AND FORMS OF EXECUTION

[0007] It is therefore an objective of the present disclosure to provide a reliable method for fault diagnosis of a battery system, in particular for detecting proper and / or faulty opening of a separating element arranged between the battery and a consumer.

[0008] This problem is solved by a method for fault diagnosis in a battery system, by a control unit, and by a computer program according to the independent patent claims. Advantageous embodiments and further developments are described in the respective dependent claims, the following description, and the drawings.

[0009] Thus, according to a first aspect, a procedure for fault diagnosis in a battery system is provided. The battery system comprises: (i) a battery, (ii) a control unit, (iii) a disconnecting element configured to disconnect an electrical connection between the battery and at least one load, and (iv) a discharge circuit configured to discharge at least one energy storage device of the at least one load.The method comprises the following steps: (a) receiving a trigger signal via the control unit and subsequently triggering the disconnecting element, for example, using a control signal; (b) activating the discharge circuit to perform a discharge operation of the at least one energy storage device; (c) determining a characteristic value for disconnection; and (d) detecting whether a disconnection error has occurred using an evaluation criterion based on the characteristic value for disconnection. The characteristic value for disconnection correlates with the discharge operation. The characteristic value correlated with the discharge operation is determined by at least one of the following parameters: a battery temperature; a pressure, in particular a pressure within the battery management system and / or a battery pressure.

[0010] According to another aspect, a control unit is provided which is configured to carry out the previously described procedure. The control unit can be a battery management system, or a battery management system can incorporate the control unit.

[0011] According to another aspect, a computer program is provided which includes commands that, when executed by a computer, cause it to carry out the procedure described above.

[0012] According to another aspect, a storage medium is provided with a computer program, wherein the computer program includes instructions which, when the computer program is executed by a computer, cause it to carry out the procedure described above.

[0013] In the context of this disclosure, a battery management system (BMS) is defined, for example, as a component connected to the battery that performs at least one of the following functions: monitoring, regulating, and protecting the battery and / or components connected to the battery. The battery management system includes the control unit. The battery management system may also include the disconnect element and / or the discharge circuit. The battery management system may be part of the battery system.

[0014] In the context of the present disclosure, a battery is defined, for example, as a storage device for electrical energy, particularly on an electrochemical basis. In one embodiment, the battery is an accumulator, i.e., a rechargeable battery. The battery can be a motor vehicle battery, in particular a high-voltage battery of a motor vehicle.

[0015] In the context of this disclosure, a disconnecting element is defined, for example, as a component configured to disconnect an electrical connection. The disconnection can be mechanical. The disconnecting element can be, for example, a pyrotechnic fuse, a contactor, or a relay. Advantageously, the disconnecting element can be arranged at an electrical connection to the positive terminal of the battery, particularly between the battery and the load. Alternatively or additionally, a disconnecting element can be arranged at a connection to the negative terminal of the battery, particularly between the battery and the load.

[0016] In the context of the present disclosure, a discharge circuit is defined, for example, as an electrical circuit configured to discharge at least one energy storage device. The discharge circuit may include a discharge resistor. The discharge resistor may be configured to convert at least some of the discharged electrical energy into heat. The discharge resistor may be encased, in particular with a plastic. This can prevent, in the event of the discharge resistor bursting, parts of the discharge resistor from impairing the functionality of other components, for example, by causing short circuits.

[0017] The discharge circuit may include a switch to activate the discharge process. When the switch is closed, the electrical conductors leading to the positive and negative terminals of the battery are electrically connected via the discharge resistor, and / or the conductors leading to the positive and negative terminals of an external connection to the battery system are electrically connected via the discharge resistor. An electrical connection between the battery system and at least one load can be established via the external connection. Furthermore, the discharge circuit may include an intervention device to interrupt or at least reduce the current through the discharge circuit. Such an intervention device could be, for example, a switchable resistor or a stop mechanism. The stop mechanism can also be implemented by the aforementioned switch.

[0018] The discharge circuit can be located inside the battery management system or externally, for example, on a housing wall of the battery management system. The discharge circuit may be necessary in certain situations, such as an accident, to dissipate any remaining electrical energy from the at least one consumer, particularly to prevent uncontrolled discharges, short circuits, or fires.

[0019] In the context of this disclosure, a consumer is defined, for example, as an electrical component that draws energy from the battery for its operation. Consumers can be, for example, high-voltage components of a motor vehicle, such as an electric motor, an inverter, or an air conditioner. The energy storage device can be, for example, a capacitor of the at least one consumer, such as a DC link capacitor or an interference suppression capacitor. The at least one energy storage device can comprise the energy storage devices of all consumers connected to the battery.

[0020] The described method and the corresponding control unit can be advantageous for reliably detecting the opening of the disconnect element and the disconnection of the electrical connection between the battery and the load. If the discharge circuit is activated when the connection is not completely disconnected, this can lead to a short circuit in the battery. Short-circuiting the battery can impair the functionality of the battery management system and / or the at least one load, including the failure of individual components. It can also lead to increased heat generation and even fire. Finally, the proper discharge of the at least one energy storage device can also be impaired. Energy remaining in the energy storage devices can pose a risk to operators of the loads or the battery system with regard to contact protection.

[0021] According to the invention, the characteristic parameter for disconnection is correlated with the discharge process. This characteristic parameter can be based exclusively on measurements that are already detected by the battery system and / or by the at least one consumer connected to the battery system. Such an embodiment can be advantageous because the discharge process varies depending on whether the electrical connection is properly disconnected or not. Fault analysis based on the discharge process can be implemented simply and cost-effectively because it can be carried out entirely using software.

[0022] According to one embodiment, the evaluation criterion is based on the maximum energy that can be stored in the at least one energy storage device of the at least one consumer. Additionally, energy storage devices of the battery management system and / or a charging device can be taken into account. The maximum energy can, for example, be derived from a contact protection device for operators of the at least one consumer and / or the battery system. Such an embodiment can be advantageous because the limiting behavior of the discharge circuit when the electrical connection is properly disconnected can be determined from the maximum energy.If the characteristic value correlated with the discharge process deviates from the limiting behavior in such a way that the discharged energy exceeds the maximum energy stored in the at least one energy storage device, it can be concluded that the electrical connection is not completely broken. The additional energy is then supplied by the battery.

[0023] According to one embodiment, the characteristic quantity correlated with the discharge process is based on a time course of at least one of the following parameters: a current through the discharge circuit, a voltage across the discharge circuit, and a DC-link voltage.

[0024] The intermediate circuit voltage can be a voltage supplied by the battery system to at least one electrical load. Specifically, it is the voltage at the positive and negative terminals in the vehicle. When the battery is connected to the vehicle, the intermediate circuit voltage and the battery voltage can be identical. However, when the vehicle's high-voltage (HV) system is disconnected, the intermediate circuit voltage should be zero or at a safe level. Therefore, when connected, electrical loads in the HV system are supplied via the intermediate circuit voltage, as this is the battery voltage in this case.

[0025] Such an embodiment can be advantageous because the aforementioned parameters are particularly suitable for characterizing the discharge process of the discharge device, especially with regard to whether the previously described limit behavior is exceeded. Furthermore, the aforementioned parameters may already be recorded by the battery system for other purposes and thus be available to the control unit anyway.

[0026] According to one embodiment, the evaluation criterion is based on at least one of the following conditions: that the current through the discharge circuit does not fall below a predetermined fraction of an output current value within a predetermined time period; and that the voltage across the discharge circuit and / or the DC link voltage does not fall below another predetermined fraction of an output voltage within a further predetermined time period. If at least one of these criteria is met, a disconnection fault can be inferred. The corresponding output values ​​can be acquired at or shortly after the time the discharge circuit is activated. The respective time periods and fractions can be determined by the discharge behavior of the discharge circuit, particularly taking into account the maximum energy that can be discharged during proper disconnection.This maximum discharged energy can be the maximum energy that can be stored in the at least one consumer. Thus, the respective time intervals and fractions can be determined by the limiting behavior described above. Such an embodiment can be advantageous because it ensures reliable error detection with minimal storage and computational effort.

[0027] According to the invention, the characteristic value correlated with the discharge process is determined by at least one of the following parameters: a battery temperature; a pressure, in particular a pressure within the battery management system and / or a battery pressure. According to one embodiment, the characteristic value correlated with the discharge process is determined by at least one of the following parameters: a temperature, in particular a temperature within the battery management system; and one or more voltages of individual battery cells. One or more of these parameters can be used for fault diagnosis, either alternatively or in addition to the current through the discharge circuit, the voltage across the discharge circuit, and / or the DC link voltage.

[0028] For example, a limit value can be set for the battery temperature and / or battery pressure, the exceeding of which indicates high power output from the battery. High power output can be an indication of a short circuit in the battery via the discharge circuit and thus of an improper disconnection of the electrical connection between the battery and the load.

[0029] Similarly, a limit value can be set for the temperature and / or pressure within the battery management system, the exceeding of which indicates high power output from the battery. Here, too, high power output can be an indication of a short circuit in the battery via the discharge circuit and thus of an improper disconnection of the electrical connection between the battery and the load. Temperature and / or pressure within the battery system could, for example, affect the discharge circuit or a spatial area near the discharge circuit.

[0030] Furthermore, one or more individual battery cells may exhibit unexpected behavior in the event of a fault. Such information can be easily retrieved because the battery management system typically has access to the voltages of the individual cells.

[0031] According to one embodiment, the disconnecting element is a pyrotechnic fuse. In the context of this disclosure, a pyrotechnic fuse can, for example, be defined as a device which, triggered by a control signal, causes an explosion to disconnect an electrical connection. The explosion can be caused, for example, by a detonator. It can disconnect the electrical connection by mechanical action, for example, by means of a wedge driven by the explosion. Such an embodiment can be advantageous because pyrotechnic fuses disconnect the electrical connection quickly and reliably, for example, faster and more reliably than a contactor. According to one embodiment, the pyrotechnic fuse is controlled by hardware, which enables even faster triggering of the pyrotechnic fuse.

[0032] Alternatively or additionally, one or more contactors can be used as separating elements. This can be particularly advantageous with regard to redundancy and compliance with safety requirements.

[0033] According to one embodiment, if a disconnection fault is detected, at least one of the following measures is taken: (i) adding an additional discharge resistor to the discharge circuit; (ii) intermittent discharge by the discharge circuit; (iii) termination of the discharge process. Intermittent discharge can be controlled, for example, based on temperature monitoring, such as battery temperature. In particular, discharge can be interrupted whenever the battery temperature exceeds a threshold. Such an embodiment can be advantageous to prevent overheating and even fire due to an uncontrolled short circuit of the battery in the event of a fault in an incompletely disconnected electrical connection.

[0034] According to one embodiment, the characteristic value for disconnection correlates with a mechanical opening process of the disconnecting element. Such a characteristic value can be considered for fault diagnosis, either as an alternative or in addition to the characteristic value correlated with the discharge process. An advantage of such an embodiment is that the mechanical opening process directly indicates the disconnection of the electrical connection. On the other hand, this might require additional sensors, which are currently unavailable in at least some pyrotechnic fuses. Analyzing both the opening and discharge processes could be particularly advantageous for reliably detecting an incompletely disconnected electrical connection.

[0035] According to one embodiment, the characteristic quantity correlated with the mechanical opening process is determined by at least one of the following parameters: (i) the existence of an electrical contact established during separation; (ii) an optically detected quantity that characterizes movement of the separating element; (iii) a quantity that characterizes mechanical deformation during separation, in particular the mechanical deformation of a strain gauge; and (iv) a quantity that detects a vibration associated with the mechanical opening process, for example, caused by an explosion capsule of the pyrotechnic device. This may require appropriate sensors, which are advantageously already used for other purposes: for example, sensors that check for current flow across the contact established during separation, optical sensors such as a camera or a photodiode, or an accelerometer that detects the vibration.

[0036] According to one embodiment, the evaluation criterion is based on a reference value determined for proper disconnection, against which the characteristic value for disconnection is compared. The reference value is based, for example, on a stored time-dependent profile of the current through the discharge circuit or the voltage across the discharge circuit in the case of proper disconnection of the electrical connection. The reference value can additionally or alternatively be determined using a neural network trained with reference data. A tolerance window can be taken into account.

[0037] According to one embodiment, the battery system is part of a motor vehicle, and in the event of an accident, the trigger signal is sent to the control unit. This trigger signal can therefore be a crash signal. Such an embodiment can be advantageous because vehicle occupants, rescue workers, or first responders at the accident scene do not come into contact with live components if the battery is safely disconnected and the energy storage device is safely discharged. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Further advantages and beneficial designs and further developments of the method, the control unit and the computer program result from the following exemplary embodiment shown in conjunction with the figure.

[0039] It shows: Fig. 1 a battery management system with connected consumer and connected battery according to an exemplary embodiment.

[0040] Identical, similar, or similarly effective elements are marked with the same reference symbols in the figures. In some figures, individual reference symbols have been omitted for clarity. The figures and the relative sizes of the elements depicted within them are not to be considered to scale. Rather, individual elements may be exaggerated for better representation and / or comprehensibility. DETAILED DESCRIPTION OF EXAMPLES OF EXECUTION

[0041] Fig.Figure 1 shows a battery system 100, which includes a battery management system 102 with a control unit 103 and a battery 101, here a high-voltage battery. The battery management system 102 also includes a disconnecting element 104, here a pyrotechnic fuse, which is configured to disconnect an electrical connection between the battery 101 and at least one load 110. The disconnecting element 104 is arranged at an electrical connection to the positive terminal of the battery 101.

[0042] Furthermore, the battery management system 102 includes a discharge circuit 106, which is configured to discharge at least one energy storage device 111 of at least one consumer 110. The discharge circuit 106 comprises a discharge resistor 107 and a switch with which the discharge circuit can be activated. When the switch is closed, conductors leading to the positive and negative terminals of the battery 101 are electrically connected to each other via the discharge resistor 107. The discharge circuit 106 also has an intervention device (not shown) with which the current through the discharge circuit 106 can be reduced or even interrupted. Such an intervention device can, for example, be a switchable resistor or a stop mechanism.

[0043] Finally, the battery management system 102 comprises further isolating elements 105, each a contactor, arranged at the respective connections to the positive and negative terminals of the battery 101. At the connection to the positive terminal, viewed from the battery 101, the contactor 105 is arranged first, followed by the pyrotechnic fuse 104.

[0044] The control unit 103 of the battery management system 102 is configured to receive a trigger signal 120, in this case a crash signal, which causes the control unit 103 to send a control signal to the pyrotechnic fuse 104 to trigger it. Furthermore, the control unit 103 is configured to activate the discharge circuit 107 by means of another control signal, for example, by closing the corresponding switch of the discharge circuit 107. The control unit is also configured to receive measurement signals from the battery 101 and a consumer 110, for example, current, voltage, temperature, and / or pressure, as well as measurement signals from the pyrotechnic fuse 104, which, for example, characterize an opening or disconnection process of the fuse 104, and measurement signals from the discharge circuit 106, which, for example, characterize a discharge process.The latter could be, for example, a corresponding current through the discharge circuit 106 or a voltage at the discharge circuit 106, or respective time profiles.

[0045] A consumer 110, here a high-voltage system, is connected to the battery system 100, with the battery management system 102 connected between battery 101 and consumer 110. The high-voltage system 110 comprises several high-voltage components, for example, an electric motor and an inverter of a motor vehicle. The high-voltage system and / or the high-voltage components include one or more energy storage devices 111, for example, a DC link capacitor.

[0046] The fault diagnosis procedure then comprises the following steps: (i) receiving a trigger signal 120, here a crash signal indicating a detected crash, by means of the control unit 103 and subsequently triggering the disconnect element 104, here the pyrofuse; (ii) activating the discharge circuit 106 to perform a discharge of the at least one energy storage device 111; (iii) determining a characteristic quantity 121 for disconnection by means of a discharge observer, wherein the characteristic quantity 121 may, for example, take into account a battery current, a battery voltage, a DC link voltage, various temperatures, a battery management system pressure, or a battery pressure; (iv) detecting whether a fault has occurred during disconnection by means of an evaluation criterion based on the characteristic quantity 121 for disconnection; and (v) in the event of a fault, reducing the current by the discharge circuit 107 or stopping the discharge.

[0047] In other words, a system or procedure is described that checks the disconnection of battery 101 from the signals already present in the system and stops the discharge if it could lead to a critical situation. In the event of a crash, a so-called crash signal 120 is sent to the battery management system 102. The crash signal 120 is evaluated, and if a crash is detected, the pyrotechnic fuse 104 is triggered. Immediately afterward, the discharge circuit 106 for the intermediate circuit 111 is activated. Simultaneously, an observer evaluates the various available signals, such as current, voltage, temperature, pressure, etc., and looks for characteristic features of proper discharge, e.g., voltage curve, current curve, temperature curve at the discharge circuit 106. Characteristic features of proper discharge can be measured and stored beforehand.Alternatively or additionally, they can be designed as a neural network and trained with appropriate data. If no proper discharge pattern is detected, it is assumed that battery 101 has not been disconnected, and the observer can trigger a stop to the discharge or slow it down by adding an additional discharge resistor to protect battery 101 from a critical situation.

[0048] An alternative design would be to generate an additional signal in the pyrotechnic fuse 104, for example, that an additional contact is closed when a clean separation has been achieved, an optical measurement of the movement, or a strain gauge on the busbar to be separated.

[0049] The invention is not limited to the exemplary embodiments described therein. Rather, the invention encompasses every new feature as well as every combination of features, which in particular includes every combination of features in the exemplary embodiments and claims. REFERENCE MARK 100 battery system 101 Battery 102 Battery Management System 103 Control unit 104 Separating element 105 additional separating element 106 Discharge circuit 107 Discharge resistor 110 consumers 111 Energy storage 120 Trigger signal 121 characteristic size for separation

Claims

[1] A method for fault diagnosis in a battery system (100), the battery system (100) comprising a battery (101), a control unit (103), a disconnecting element (104) configured to disconnect an electrical connection between the battery (101) and at least one consumer (110), and a discharge circuit (106) configured to discharge at least one energy storage device (111) of the at least one consumer (110), the method comprising the following steps: - Receiving a trigger signal (120) by means of the control unit (103) and subsequent triggering of the separating element (104); - Activating the discharge circuit (106) to perform a discharge process of the at least one energy storage device (111); - Determining a characteristic quantity for separation (121); and - Detecting whether an error occurred during separation using an evaluation criterion based on the characteristic quantity for separation (121), where the quantity characteristic for separation (121) correlates with the discharge process, wherein the characteristic quantity (121) correlated with the discharge process is determined by at least one of the following parameters: a battery temperature; a pressure, in particular a pressure within the battery management system (102) and / or a battery pressure. [2] Method according to the preceding claim, wherein the evaluation criterion is based on an energy that can be stored at most in the at least one energy storage device (111) of the at least one consumer (110). [3] Method according to one of the preceding claims, wherein the characteristic quantity (121) correlated with the discharge process is based on a time course of at least one of the following parameters: a current through the discharge circuit (106); a voltage across the discharge circuit (106); and an intermediate circuit voltage. [4] Method according to the preceding claim, wherein the evaluation criterion is based on at least one of the following conditions: that the current through the discharge circuit (106) does not fall below a predetermined fraction of an initial value of the current within a predetermined time period; and that the voltage across the discharge circuit (106) does not fall below a further predetermined fraction of an initial value of the voltage within a further predetermined time period. [5] Method according to one of the preceding claims, wherein the characteristic quantity (121) correlated with the discharge process is determined by at least one of the following parameters: a temperature, in particular a temperature within a battery management system (102); and one or more voltages of individual cells of the battery (101). [6] Method according to any of the preceding claims, wherein the separating element (104) is a pyrotechnic safety device. [7] Method according to any of the preceding claims, wherein, if an error is detected during separation, at least one of the following measures is taken: - Adding an additional discharge resistor to the discharge circuit (106); - intermittent discharge through the discharge circuit (106); and - Canceling the unloading process. [8] Method according to one of the preceding claims, wherein the characteristic size (121) for separation correlates with a mechanical opening process of the separating element (104). [9] Method according to the preceding claim, wherein the characteristic quantity (121) correlated with the mechanical opening process is determined by at least one of the following parameters: the existence of an electrical contact that is established during separation; an optically detected quantity that characterizes a movement of the separating element (104); a quantity that characterizes a mechanical deformation during separation, in particular the mechanical deformation of a strain gauge; and a quantity that detects a vibration associated with the mechanical opening process. [10] Method according to one of the preceding claims, wherein the evaluation criterion is based on a reference quantity determined for proper separation, with which the quantity characteristic for separation is compared. [11] Method according to one of the preceding claims, wherein the battery system (100) is part of a motor vehicle and wherein the trigger signal (120) is sent to the control unit (103) in the event of an accident. [12] Control unit (103) which is configured to carry out a method according to one of the preceding claims. [13] Computer program comprising instructions which, when executed by a computer, cause the computer to perform a method according to any one of claims 1 to 11.

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