METHOD FOR CONTROLLING POWER TRANSFER FROM A GRID TO A VEHICLE

Abstract

A method for controlling power transfer from a grid to a rechargeable energy storage system, RESS, and/or an auxiliary load of the vehicle, via at least one intermediate power transfer component. The method comprises providing predicted operational information of the vehicle, the predicted operational information comprising a connected time period in which the vehicle is connected to the grid, providing component data comprising power transfer characteristic of the intermediate power transfer component, the component data including at least the critical temperature limit of the intermediate power transfer component, transferring power from the grid to the RESS and/or from the grid to the auxiliary load of the vehicle according to a power transfer model, such that the temperature of the intermediate power transfer component is kept at least below the critical temperature limit.

Claims

1. A method for controlling power transfer from a grid to a rechargeable energy storage system, RESS, and/or an auxiliary load of the vehicle, via at least one intermediate power transfer component, the method comprising: providing predicted operational information of the vehicle, the predicted operational information comprising a connected time period in which the vehicle is connected to the grid, providing component data comprising power transfer characteristic of the intermediate power transfer component, the component data including at least the critical temperature limit of the intermediate power transfer component, transferring power from the grid to the RESS and/or from the grid to the auxiliary load of the vehicle according to a power transfer model, wherein the power transfer model adapts the power transfer and a power transferring time from the grid during the connected time period in response to at least the component data, such that the temperature of the intermediate power transfer component is kept at least below the critical temperature limit.

2. The method according to claim 1, wherein transferring power from the grid to the RESS is performed as charging, and the power transferring time from the grid to the RESS is referred to as charging time, and wherein transferring power from the grid to the auxiliary load is performed as auxiliary powering, and the power transferring time from the grid to the auxiliary load is referred to as auxiliary powering time, the method further comprising: setting at least one of the charging time and the auxiliary powering time based on the predicted operational information of the vehicle.

3. The method according to claim 1, wherein the predicted operational information of the vehicle comprises a predicted initialization time of propelling the vehicle ending the connected time period, and wherein the power transferring time is set based on at least the predicted initialization time.

4. The method according to claim 1, wherein the power transferring time is set based on a user-input.

5. The method according to claim 1, wherein the power transfer model adapts the power transfer from the grid during the connected time period in response to the component data, such that the temperature of the intermediate power transfer component is kept in a lower temperature interval.

6. The method according to claim 1, wherein the power transfer model adapts the power transfer from the grid during the connected time period in response to the component data, such that the power transferring time is kept at a minimum.

7. The method according to claim 1, wherein the power transfer model further adapts the power transferring time during the connected time period in response to the ambient temperature.

8. The method according to claim 1, wherein the intermediate power transfer component comprises at least one of the following components: a junction box, a contactor, a charging switching unit, an on-board charger, a charging inlet, a cable, a busbar.

9. A power transferring system for controlling power transfer from a grid to a rechargeable energy storage system, RESS, and/or an auxiliary load of the vehicle, via at least one intermediate power transfer component, the power transferring system being configured to: provide predicted operational information of the vehicle, the predicted operational information comprising a connected time period in which the vehicle is connected to the grid, provide component data comprising power transfer characteristic of the intermediate power transfer component, the component data including at least the critical temperature limit of the intermediate power transfer component, transfer power from the grid to the RESS and/or from the grid to the auxiliary load of the vehicle according to a power transfer model, wherein the power transfer model adapts the power transfer and a power transferring time from the grid during the connected time period in response to at least the component data, such that the temperature of the intermediate power transfer component is kept at least below the critical temperature limit.

10. The power transferring system according to claim 9, further comprising a user-input unit configured to receive a user-input of the power transferring time.

11. The power transferring system according to claim 9, wherein the power transfer model is configured to adapt the power transferring time during the connected time period in response to the component data, such that the temperature of the intermediate power transfer component is kept in a lower temperature interval.

12. The power transferring system according to claim 9, wherein the power transfer model is configured to adapt the power transfer from the grid during the connected time period in response to the component data, such that the power transferring time is kept at a minimum.

13. The power transferring system according to claim 9, comprising the at least one intermediate power transfer component such that the power transferring system is configured to transfer power from the grid to the RESS and/or the auxiliary load of the vehicle via the intermediate power transfer component, wherein the intermediate power transfer component comprises at least one of the following components: a junction box, a contactor, a charging switching unit, an on-board charger, a charging inlet, a cable, a busbar.

14. A control unit for a vehicle, the control unit being configured to perform the method according to claim 1.

15. A vehicle comprising a power transferring system according to claim 9.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0060] With reference to the appended drawings, below follows a more detailed description of embodiments of the invention cited as examples. In the drawings:

[0061] FIG. 1 is a side schematic view of a vehicle in accordance with an example embodiment of the invention;

[0062] FIG. 2 is a schematic view of a power transferring system for controlling power transfer from a grid to a rechargeable energy storage system, RESS, and/or an auxiliary load of the vehicle in accordance with an example embodiment of the invention;

[0063] FIG. 3 is a graph showing how the power transfer and power transferring time is set resulting in different temperatures of an intermediate power transfer component in accordance with an example embodiment of the invention; and

[0064] FIG. 4 is a flowchart illustrating the steps of a method in accordance with example embodiments of the invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

[0065] With reference to FIG. 1, a vehicle 1, here embodied as a heavy duty truck 1, is disclosed for which a method, a power transferring system 10, and/or a control unit 17 of a kind disclosed in the present invention is advantageous. However, the method, power transferring system 10 or control unit 17 may as well be implemented in other types of vehicles, such as in busses, light-weight trucks, passenger cars, marine applications (e.g. in a vessel) etc. The vehicle 1 is an electric vehicle, such as a full electric vehicle or a hybrid, comprising at least one electric machine 15, a rechargeable energy storage system, RESS, 30 comprising three energy storage devices 31, 32, 33, typically batteries, the RESS 30 being arranged and configured to power the electric machine 15. Moreover, the vehicle 1 comprises an auxiliary load 40 arranged and configured for being powered by the RESS 30, the auxiliary load 40 being e.g. a heater or a HVAC system. Thus, the RESS 30 is arranged and configured to supply at least two different loads 15, 40 with electric power, the first load being the electric machine 15, and the second load being the auxiliary load 40. The vehicle 1 typically further comprises other parts of the powertrain such as transmission, drive shafts and wheels (not shown in detail).

[0066] As seen in FIG. 1, the RESS 30 is connected to an electrical energy source, here being a power grid, or grid 80, via an energy transfer means 90, typically a cable for transferring electrical energy to the three energy storage devices 31, 32, 33 via a charging inlet 35. Thus, the charging inlet 35 is an example of an intermediate power transfer components facilitating the power transfer from the grid 80 (and/or the cable 90) to the RESS 30 and/or the auxiliary load 40. Hereby, the energy storage devices 31, 32, 33 may be charged with electrical energy. Furthermore, any one of the loads, such as e.g. the auxiliary load 40, may be powered directly via the grid 80.

[0067] FIG. 2 is a schematic view of a power transferring system 110 for controlling power transfer from a grid 80 to a rechargeable energy storage system, RESS, 130 and/or an auxiliary load 140 of the vehicle. When transferring power from the grid 80 to the RESS 130 and/or the auxiliary load 140, power is transferred via a plurality of intermediate power transfer components, which will be described in the following. The embodiment shown in FIG. 2 may be implemented in the vehicle 1 of FIG. 1.

[0068] The energy storage system 130 is in FIG. 2 connected to two loads being e.g. an electric machine 115 and the auxiliary load 140 arranged and configured for being powered by the energy storage system 130 and the grid 80. Thus, the RESS 130 is connected to the grid 80, the grid 80 supplying electrical energy to the energy storage system 130 and/or the auxiliary load 140 via a cable 90 and a charging inlet 135. Moreover, in FIG. 2, the RESS 130 comprises three energy storage devices 131, 132, 133 or batteries 131, 132, 133 arranged in a parallel configuration, an energy source interface 134 providing an interface of the three energy storage devices 131, 132, 133 with the grid 80 (and/or cable 90), and a load interface 136 providing an interface of the three energy storage devices 131, 132, 133 with each one of the two loads 115, 140. The energy source interface 134 and/or load interface 136 may for example be comprised of, or comprise, a junction box and/or a charging switching unit. In more detail, each one of the energy storage devices 131, 132, 133 comprises a respective first contactor 131A, 132A, 133A for connection to the energy source interface 134 and the grid 80, and a respective second contactor 131B, 132B, 133B for connection to the load interface 136 and the loads 115, 140. The contactors 131A, 132A, 133A, 131B, 132B, 133B are only schematically illustrated as boxes in FIG. 2, and may according to at least one example embodiment be comprised in the energy source interface 134, and the load interface 136, respectively. In other words, the first contactors 131A, 132A, 133A may be comprised in the energy source interface 134 and the second contactors 131B, 132B, 133B may be comprised in the load interface 136. The contactors 131A, 132A, 133A, 131B, 132B, 133B may e.g. be arcing contactors or circuit breakers or another type of switches.

[0069] The a power transferring system 110 comprises a control unit 117, and is arranged and configured to control at least a part of the operation of the RESS 130 and the auxiliary load 140, and is in FIG. 2 schematically illustrated to be connected to the energy source interface 134 and the load interface 136. Hereby, the power transferring system 110 may e.g. be configured to control charging of any one of the energy storage devices 131, 132, 133, and/or powering of any one of the two loads 115, 140. The power transferring system 110 is further configured to enable powering of any one of the two loads 115, 140 by the grid 80, wherein electrical energy is transferred via the RESS 130 (with or without simultaneous charging of any one of the energy storage devices 131, 132, 133). Alternatively, the power transferring system 110 comprises a junction box 137 providing an electrical connection between the grid 80 and the auxiliary load 140 in parallel to the RESS 130. Optionally, the junction box 137 further comprises an electrical connection to the RESS 130 (i.e. instead of the cable 90 being directly coupled to the charging inlet 135 as shown in FIG. 2) via the charging inlet 135 (and any charging switch units or onboard charger).

[0070] The power transferring system 110 further comprises a predictive operation unit 145 configured to directly or indirectly provide predicted operational information of the vehicle to the control unit 117. In the embodiment of FIG. 2, a parameter providing unit 150 configured to provide parameter data, such as e.g. external parameter data, to the control unit 117 is also comprised in the power transferring system 110.

[0071] The control unit 117 is configured to provide predicted operational information of the vehicle, e.g. by receiving such information by the predictive operation unit 145. Thus, the predictive operation unit 145 may according to one example embodiment supply predicted operational information of the vehicle, e.g. as scheduled operational information of the vehicle. The predicted operational information of the vehicle comprises at least a connected time period in which the vehicle is connected to the grid 80. For example, the predicted operational information of the vehicle in the form of scheduled operational information may comprise scheduled operational load of the RESS 130, scheduled operation of the electric machine 115, scheduled operation of the auxiliary load 140 and scheduled time when the vehicle, or RESS 130, is connected to the grid 80 (i.e. said connected time period). Typically, the scheduled operation is as a function of time. Thus, the power transferring system 110 is at least configured to provide or receive predicted operational information of the vehicle, the predicted operational information comprising at least a connected time period in which the vehicle (or RESS 130) is connected to the grid 80.

[0072] Moreover, the control unit 117 is configured to provide component data comprising power transfer characteristic of at least one intermediate power transfer component, the component data including at least the critical temperature limit of the intermediate power transfer component. In FIG. 2, the intermediate power transfer components are for example the cable 90, the charging inlet 135, the energy source interface 134 and any junction box or charging switching unit which may be comprised in the energy source interface 134, the first contactors 131A, 132A, 133A, the second contactors 131B, 132B, 133B, the load interface 136 and any junction box or charging switching unit which may be comprised in the load interface 136, and any cable 91 connecting the RESS 130 with the auxiliary load 140. An intermediate power transfer component may be defined as any component between the electrical energy source (e.g. the grid 80, or the cable 90 used to transfer power from the grid 80 to the vehicle) and the power target, the latter being either one of the energy storage devices 131, 132, 133, and the auxiliary load 140. Thus, an intermediate power transfer component may be defined as being a power transfer component between the grid 80 (or the cable 90 used to transfer power from the grid 80) and the energy storage devices 131, 132, 133 or the auxiliary load 140 which is taking part in the process of transferring power, and/or a component which is transferring power from the grid 80 (or the cable 90 used to transfer power from the grid 80) to the energy storage devices 131, 132, 133 or the auxiliary load 140. Thus, the at least one intermediate power transfer component may comprise one or more of the previously mentioned examples.

[0073] Moreover, the control unit 117 is configured to control the power transfer from the grid 80 to the RESS 130 and/or from the grid 80 to the auxiliary load 140 according to a power transfer model. The power transfer model is typically comprised in the control unit 117. The power transfer model is configured to adapt the power transfer and a power transferring time from the grid 80 during the connected time period in response to at least the component data, such that the temperature of the intermediate power transfer component is kept at least below the critical temperature limit.

[0074] The control unit 117 may comprise, or be configured to implement, a thermal model, or heat transfer model, of the intermediate power transfer component(s), and the temperature of each one of the intermediate power transfer components can be determined or estimated based on the thermal model together with the power transfer and power transferring time. Such estimate temperature may then be compared to the component data of the intermediate power transfer components. The thermal model may typically utilize known temperature characteristics and/or known power transfer characteristic of the intermediate power transfer components to estimate the temperature thereof. That is, the control unit 117 typically comprises a computer program comprising program code means for at least executing the thermal model, and possibly storing the thermal model. The ambient temperature may as well be used in determining the temperature of the intermediate power transfer components, and e.g. be used as input data to the thermal model. For example, the parameter providing unit 150 may e.g. be a sensor, such as a temperature sensor, configured to measure the ambient temperature of the vehicle.

[0075] The predictive operation unit 145 may e.g. be integrated into a vehicle functionality, and/or may be a user-input device configured to enable a manual functionality of providing predicted operational information of the vehicle (e.g. scheduled operational information of the vehicle). That is, the predictive operation unit 145 may be a user-input unit 145 configured to receive a user-input of the power transferring time. The user-input device may e.g. be a vehicle display or a user device, such as e.g. a mobile phone or tablet. The predictive operation unit 145 can for example be a mobile app, in vehicle cluster or an offboard vehicle management system. However, it should be noted that the predictive operation unit 145 and the parameter providing unit 150 are optional. Thus, the predicted operational information of the vehicle may be provided from something else than the predictive operation unit 145, and the temperature estimate of the intermediate power transfer component may be provided without the input from the parameter providing unit 150.

[0076] With reference to FIG. 2, the following example procedure may be carried out when transferring power from the grid 80 to the RESS 130 and/or from the grid 80 to the auxiliary load 140.

[0077] A user (not shown) uses the predictive operation unit 145 to set the usage need of the vehicle. For example, the usage need includes information to when the vehicle is to be used, corresponding to a predicted initialization time of propelling the vehicle, or a scheduled initialization time, and for what the vehicle is to be used for, corresponding to e.g. a schedule operational load over time. Hereby, said connected time period for when the vehicle is to be connected to the grid 80 may be determined. For example, the user may set a planned or scheduled route, and/or desired destination, possibly together with scheduled auxiliary actions for using the auxiliary load 140. As an example, such usage need may be that the vehicle is to be utilized for performance driving at 08:00 tomorrow, directly thereafter driving on the highway to a first destination, and when reaching the first destination the vehicle will be connected to the grid for 30 minutes, and subsequently driving to a second destination, and when reaching the second destination, the vehicle will be connected to the grid 80 overnight. Thus, a respective connected time period at the first destination may be determined, and a respective connected time period at the second destination may be determined. Possibly, use of the auxiliary load 140, e.g. by means of PTO for auxiliary actions of performing work may be included the usage input. Depending on the level of details of the usage need, it may be used as input data to determine said connected time period(s), and/or it may be used directly to determine said connected time periods(s). For example, the usage need may be pre-processed, e.g. by including topography of the scheduled route, predicted road, traffic and/or weather conditions, and other internal or external parameters e.g. parameters of the RESS, parameters of the drive cycle and/or work cycle, parameters of the environment to the vehicle, to determine destination times and correspondingly said connected time period(s). Such pre-processing may be performed by the control unit 117.

[0078] An example of how the power transfer and power transferring time is set resulting in different temperature of an intermediate power transfer component is presented in FIG. 3. FIG. 3 is a graph showing the temperature (y1-axis) and power transfer (y2-axis) as a function of time (x-axis). In the example in FIG. 3, the intermediate power transfer component is for example the inlet charger 135, which is typically only transferring power when the vehicle is connected to the grid 80. The intermediate power transfer component is operable in a temperature interval between a lower temperature limit 260 and an upper, or critical, temperature limit 262. In other words, component data of the intermediate power transfer component 135 comprises at least information of the upper, or critical, temperature limit 262. Corresponding to the usage need example given above, the vehicle initiates driving at tstart (08:00), directly thereafter drives on the highway to a first destination, and when reaching the first destination at time t11 the vehicle is connected to the grid for 30 minutes, i.e. up to the time t12. Thus, in the first connected time period between t11 and t12, the vehicle is connected to the grid 80 for a relatively short time. In this example, the vehicle is transferring power from the grid 80 to the RESS 130 during the first connected time period between t11 and t12, and is thus charging the energy storage devices 131, 132, 133 over a charging time. As the charging time is set to be relatively short, the transferred power (charging power) is adapted to be relatively high, represented by the dotted line at a level of a first power indication P1. That is, the power transfer model adapts the charging from the grid 80 during the first connected time period between t11 and t12 in response to the component data, such that the charging time is kept low, or at a minimum. Thus, the temperature 270 of the intermediate power transfer component 135 is kept in the higher temperature interval, here at the maximum temperature T1 slightly below the upper, or critical, temperature limit 262. Thus, as the charging time is low, the temperature 270 of the intermediate power transfer component 135 is allowed to be relatively high, at least up to the upper, or critical temperature limit 262. In the example of FIG. 3, the charging time is extending over the whole first connected time period between t11 and t12, but may alternatively extending during a majority, such as e.g. over at least 95%, or at least over 99% of the first connected time period between t11 and t12. Thus, the power transfer model may be configured to adapt the power transferring time during the first connected time period in response to the component data, such that the temperature of the intermediate power transfer component is kept in the lower temperature interval.

[0079] Subsequently, the vehicle drives to the second destination after t12. Thus the time t12 may represent a predicted initialization time of propelling the vehicle ending the first connected time period between t11 and tend. When reaching the second destination at time t21, the vehicle is connected to the grid 80 overnight, i.e. up to the time tend. Thus, a second connected time period between t21 and tend in which the vehicle is connected to the grid 80 is provided. The second connected time period is a relatively long time-period as it extends overnight, e.g. over at least 8 hours. In this example, the vehicle is transferring power from the grid 80 to the RESS 130 and is transferring power from the grid 80 to the auxiliary load 140, e.g. being a HVAC system. Thus, similar to during the first connected time period, charging of the energy storage devices 131, 132, 133 over a charging time is achieved. However, during the second connected time period, power is also transferred from the grid to the auxiliary load 140 by auxiliary powering over an auxiliary powering time. For example, charging may be performed prior to the auxiliary powering. Hereby charging of the energy storage devices 131, 132, 133 may be guaranteed prior to using the electrical energy to something else. Alternatively, charging and auxiliary powering are performed simultaneously. Hereby charging of the energy storage devices 131, 132, 133 may be performed simultaneously with operating the auxiliary load 140, e.g. in order to heat up the cabin of the vehicle. Hereafter in this example, the charging and auxiliary powering are commonly referred to as a power transfer over a power transferring time. As the power transferring time is set to be relatively long in the second connected time period, the transferred power (charging power and/or auxiliary power) is adapted to be relatively low, represented by the dotted line at a level of a second power indication P2. That is, the power transfer model adapts the power transfer from the grid 80 during the second connected time period between t21 and tend in response to the component data, such that the temperature 272 of the intermediate power transfer component 135 is kept in a lower temperature interval. Thus, the temperature of the intermediate power transfer component 135 is kept in the lower temperature interval, here at the maximum temperature T2 slightly above the lower temperature limit 260. Thus, in order to keep the temperature 272 of the intermediate power transfer component 135 in the lower temperature interval, the power transferring time is allowed to increase, or extend, such that the desired temperature of the intermediate power transfer component 135 can be met. In the example of FIG. 3, the power transferring time is extending from time t21 to the time t22 over only a portion of the second connected time period between t21 and tend. Thus, setting at least one of the charging time and the auxiliary powering time based on the predicted operational information of the vehicle. Thus, the power transfer model may be configured to adapt the power transfer from the grid during the second connected time period in response to the component data, such that the power transferring time is kept at a minimum.

[0080] Although only one intermediate power transfer component is exemplified in FIG. 3, more intermediate power transfer components as exemplified before may be used to adapt the power transfer from the grid. Thus, the intermediate power transfer component may be a plurality of intermediate power transfer components. The temperature adaptations of the intermediate power transfer components may then be determined as an average, or in relation to the most critical intermediate power transfer component, or in relation to the intermediate power transfer component being most sensitive to higher temperatures (i.e. having the lowest critical temperature limit). It should be noted that at least some of the intermediate power transfer components may be operated (i.e. transfer power) during operation of the vehicle, e.g. during propelling the vehicle. Thus, the temperature of such intermediate components may increase and decrease during vehicle operation depending on the usage thereof.

[0081] A method for controlling power transfer from a grid to a rechargeable energy storage system, RESS, and/or an auxiliary load of the vehicle, via at least one intermediate power transfer component, will now be described in more general terms with additional reference to FIG. 4. FIG. 4 is a flowchart describing the steps of such method. The method may e.g. be implemented in the control unit 117 of FIG. 2, and used in the vehicle 1 of FIG. 1.

[0082] In a first step S10, predicted operational information of the vehicle is provided. Such predicted operational information comprises at least a connected time period in which the vehicle is connected to the grid. The predicted operational information of the vehicle typically comprises a predicted initialization time of propelling the vehicle which ends the connected time period. Thus, the power transferring time may be set at least based on, or in response to, the predicted initialization time. The predicted operational information of the vehicle may for example be based on scheduled operational information of the vehicle, typically related to a usage need given by a user or by a system comprising scheduled information of the vehicle. Thus, the power transferring time is may be set based on, or in response to, a user-input. The scheduled operation of the vehicle may comprise a scheduled route of the vehicle comprising scheduled times when the vehicle is to be connected to the grid and possibly scheduled auxiliary actions of performing work during at least a portion of the scheduled route. Thus, the predicted operational information of the vehicle may be predicted in response to such scheduled route of the vehicle. The at least one intermediate power transfer component may be at least one of, or may comprise at least one of, the following components: a junction box, a contactor, a charging switching unit, an on-board charger, a charging inlet, a cable, a busbar. The at least one intermediate power transfer component may be a plurality of intermediate power transfer components.

[0083] In a second step S20, component data comprising power transfer characteristic of the intermediate power transfer component is provided. The component data includes at least the critical temperature limit of the intermediate power transfer component.

[0084] In a third step S30, power from the grid to the RESS and/or from the grid to the auxiliary load of the vehicle is transferred according to a power transfer model. The power transfer model is configured to adapt the power transfer and a power transferring time from the grid during the connected time period in response to at least the component data, such that the temperature of the intermediate power transfer component is kept at least below the critical temperature limit. The power transfer model may adapt the power transferring time during the connected time period in response to the ambient temperature. Hence, the ambient temperature may be used as input when adapting the power transfer such that the temperature of the intermediate power transfer component is kept at least below the critical temperature limit.

[0085] In a first optional sub-step S32 to the third step S30, the step of transferring power from the grid to the RESS is charging. Thus, the power transferring time from the grid to the RESS is referred to as charging time. In a second optional sub-step S34 of the third step S30, the step of transferring power from the grid to the auxiliary load is auxiliary powering. Thus, the power transferring time from the grid to the auxiliary load is referred to as auxiliary powering time. In a third sub-step S36 of the third step S30, at least one of the charging time and the auxiliary powering time is set based on the predicted operational information of the vehicle.

[0086] In an optional fourth step S40, the power transfer model adapts the power transfer S30 from the grid during the connected time period in response to the component data such that the temperature of the intermediate power transfer component is kept in a lower temperature interval.

[0087] In an optional fifth step S50, carried out prior, after, or at least partly simultaneously with the fourth step S40, the power transfer model adapts the power transfer from the grid during the connected time period in response to the component data, such that the power transferring time is kept at a minimum.

[0088] It should be noted that the naming of the steps not necessarily, but might according to at least one example embodiment, relate to the order in which the steps are carried out, unless explicitly stated otherwise. One or more of the steps may be combined and carried out simultaneously. The control unit 117 of FIG. 2 may be configured to carry out one or several of the steps S10-S50.

[0089] It is to be understood that the present invention is not limited to the embodiments described above and illustrated in the drawings; rather, the skilled person will recognize that many changes and modifications may be made within the scope of the appended claims.

[0090] Additionally, variations to the disclosed embodiments can be understood and effected by the skilled person in practicing the claimed inventive concept, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.