A method and control unit for controlling use of an electric energy storage

Abstract

A method (100) performed by a master control unit (ECU1) for controlling use of an electric energy storage of a vehicle, the vehicle comprising at least two control units (ECU1, ECU2), each control unit (ECU1, ECU2) being associated with an energy consuming user (101, 102; 301 -304), the master control unit (ECU1) being selected as a control unit of the at least two control units (ECU1, ECU2), wherein any additional control unit (ECU2) of the at least two control units (ECU1, ECU2) in addition to the master control unit (ECU1) form slave control unit(s) the method comprising:receiving (220), from a slave control unit (ECU2) a request for an energy storage resource to be used by its associated user (101, 102; 301-304);transmitting (240), to the slave control unit (ECU2) from which the request was received, an energy storage resource usage limit allocated to the user (101, 102; 301-304) associated with that slave control unit (ECU2).

Description

Aspects of the invention relate to a method and a control unit for controlling use of an electric energy storage of a vehicle. Aspects of the invention also relate to a computer program, a computer-readable medium and a vehicle comprising a control unit.BackgroundThe following background description does not necessarily constitute prior art.It is becoming increasingly common that vehicles, not only land vehicles but also sea and air vehicles, are designed as at least partially electrified vehicles. Such vehicles may comprise one or more electric energy users, where such users may be configured to consume energy from an electric energy storage, such as a high-voltage battery. The users may alternatively, or in addition, be configured to charge the electric energy storage.The electric energy storage users, such as high-voltage battery users, may be configured to be independently powered by separate electric energy storages, or be configured to share a common electric energy storage. For example, a plurality of users may share a high-voltage battery. In case a plurality of users share a single energy storage, the energy storage resources, e.g. available power / current for consumption, and / or capacity to receive charging, may be controlled by a control unit, where the control unit may be responsible for all battery users, and where the control unit together with the users may form an integrated system.SummaryIt is an object of the invention to provide a method for controlling use of an electric energy storage, such as a high-voltage battery, that allows independent energy storage users to efficiently share a common energy storage.According to aspects of the invention, it is provided a method performed by a master control unit for controlling use of an electric energy storage of a vehicle, the vehicle comprising at least two control units, each control unit being associated with an energy consuming user, the master control unit being selected as a control unit of the at least two control units, wherein any additional control unit of the at least two control units in addition to the master control unit form slave control unit(s), the method comprising:receiving, from a slave control unit a request for power to be used by its associated user;transmitting, to the slave control unit from which the request was received, an energy storage resource usage limit allocated to the user associated with that slave control unit.Solutions where a plurality of energy resource users share a common energy resource, such as a high-voltage battery, are frequently occurring. The energy resource, however, can in general only be controlled by a single controller. That is, a single controller, in the following denoted control unit, is then responsible for the operation of the energy storage. It is not feasible to have a system where a plurality of control units simultaneously share the responsibility for distributing energy storage resources of a single energy storage among various users, and thereby simultaneously attempt to control the energy storage, with potentially conflicting control as result.Systems may therefore be designed such that a single control unit is responsible for controlling power consumption of all users. This forms an integrated system, where a particular control unit is dedicated and designed for the control, and where all users belong to the integrated system. The master control unit thereby also controls the various users. This is a common method of designing electric vehicles.There exist, however, situations where it may be desirable to have a plurality of normally independently controlled energy resource users, in particular users that may be individually controlled by a vehicle operator. This may be accomplished by using separate energy storages for each user. Still, it may be desirable, e.g. from cost or design reasons, that also independently controlled users share a common energy resource. This may be accomplished by providing the energy resource itself with a control unit that is configured to carry out the desired control, and hence be responsible for the distribution of available energy storage resources among the various connected users. This, however, may provide a solution that is less optimal.According to the invention, a different way of controlling a shared electric energy storage is provided, where still individually controlled users are utilised in the vehicle. The users are associated with a particular control unit, respectively, where control unit and user may form part of an integrated assembly or system, where each such user may form an individual solution of such kind. The vehicle comprises at least two control units, and each control unit is associated with an energy consuming user. There may hence be a plurality of independent systems in the vehicle.The control according to the invention is accomplished by a method performed by a master control unit controlling use of an electric energy storage of a vehicle. The master control unit is selected as a control unit of the at least two control units, and any additional control unit of the at least two control units in addition to the master control unit is controlled to form slave control unit(s). Hence the roles of the control units are not predestined, but selected from the at least two control units that are associated with, and control, a user. The control unit being selected as master control unit receives, from a slave control unit, a request for power to be used by the user associated with the slave control unit, and the master control unit transmits, to the slave control unit from which the request was received, an energy storage resource usage limit allocated to the user associated with that slave control unit.In this way, the master control unit can be selected from among the control units that are associated with a user. This provides a solution where the energy storage, such as high-voltage battery, is controlled by a single control unit without the need for the use of a control unit of the energy storage to be used for handling power requests of a plurality of energy storage users.This furthermore provides a solution to situations where there are more than one independent user that needs to use a common, i.e. shared, energy storage, and where there would be a need to establish a control unit that is responsible for energy storage resource allocation. The selected master control unit is responsible not only for the associated user, but also for dividing the available energy resources between users that request resources. In this way resources may be more efficiently used. As was mentioned, the electric energy storage may be a high-voltage electric energy storage, such as a high-voltage battery.According to aspects of the invention, the vehicle comprises at least three energy storage users, where the control unit of one of the at least three energy storage users is selected to operate as master control unit, and the control units of the others of the at least three energy storage users are controlled to form slave control units. Hence any number of users with associated control units may share a common resource such as a high-voltage battery, but where only one of the control units is selected to operate as master, and the other control units assume the role of slave control units.According to aspects of the invention, the method comprises to select the master control unit among the at least two control units. In this way, a single control unit need not be designed to be master, and the other one or more control units be designed to always be slaves. Instead, a selection can be made, where different control units may be selected as master control units, although only one at a time.According to aspects of the invention, the energy storage resource usage limit is allocated based on the received request. The master may hence receive a request, which may be a request for, e.g., a power or current to be drawn from the energy storage resource. The master control unit may then determine whether the request is to be allowed, or whether, e.g., only a portion, or nothing at all, of the requested resources can be allocated. This may be the case, for example, when a plurality of users request an aggregated usage that exceeds the capacity of the energy storage. In such situations the resources may be allocated such that all users receive a portion of the requested resources, or one or more users receive the requested resources while others receive no resource at all for the time being. This may be determined, for example, based on priorities, where users that are more critical for the operation of the vehicle may be prioritised over less critical functions. The resources may also be allocated on a time basis, where the users are allocated time slots for access to the energy storage resources.According to aspects of the invention, the request for a resource, and the energy resource usage limit that the master control unit communicates to a slave control unit, may be a request for, and limit regarding, a maximum power and / or current consumption that the user requests to use from the electric energy storage, where hence the limit may be the full requested power / current or a portion thereof. The request and limit may also, e.g., in case the user operates as generator, be a maximum charging power and / or current for charging the electric energy storage. When determining the resources to be allocated the master control unit will also take the own requests into consideration, since the master control unit also is associated with a user that may request resources.According to aspects of the invention, the request for an energy storage resource to be used by a user is determined based on user individual vehicle operator manoeuvrable means for requesting power from the user. The master control unit may thereby regularly receive requests for resources from a slave control unit, where the requests may change for each change a vehicle operator is carrying out using the operator manoeuvrable means.According to aspects of the invention, the method further comprises, when selecting a control unit as the master control unit among the at least two control unit, that at least one of the at least two control units detect whether there is a presence of a master control unit. The control unit commences operation as a slave control unit when detecting presence of a master control unit, and commences operation as a master control unit when presence of a master control unit is not detected. The control unit may detect presence, e.g., by detecting a presence of predetermined messages that a master control unit is expected to transmit. This procedure may ensure that there will always be a control unit that assumes the role of master control unit and hence the control of the energy resource.According to aspects of the invention, wherein the control units of the at least two users are configured to detect whether there is a presence of a master control unit when powered up. This may further ensure that there will always be a master, since the control units will check presence as soon as they are powered up.The selection of a control unit as a master control unit may be carried out utilising unique identities of the users associated with the control units, respectively, and / or unique identities of the control units. A control unit may then be selected as master control unit based on the unique identities. The unique identities may constitute software encoded identities and / or hardware encoded unique identities. The selection may thereby, e.g., be based on rules that determine the selection based on how the identities relate to each other.The selecting may further comprise that the control units communicate the unique identities to each other, and the control units determining the selecting of a control unit as master control unit based on the communicated unique identities. For example, in case predetermined rules are utilised, all control units may determine its own role following reception of the identities of the other control units. The identities may also be used by a single control unit to determine the roles, where the determination of which control unit to select master may be determined from manner in which the identities relate to each other.According to aspects of the invention the unique identities may be used in a manner such that a same control unit is selected as master control unit each time the control units are simultaneously powered up. This, too, may be determined based on the manner in which the identities relate to each other. For example, a highest or lowest number representation of the identity may be selected as master, where the number representation may be determined in any suitable way through suitable calculation in case the identities are not fully numerical.According to aspects of the invention, the master control unit regularly communicate master messages. This may provide an indication that the master is operational and controls the energy resource. The at least one slave control unit may regularly receive the master messages, and take over operation as master control unit in case the master control unit stops regularly communicating the master messages. In this way it can be ensured that there will always be a master control unit present. In case there are more than one control unit operating as slaves, the selection of the new master can be carried out according to the same principles as the first selection of master.According to aspects of the invention, the previous master control unit commence operation as slave control unit when resuming operation. It is hence not necessary to reselect master only because a previous master become operative again.According to aspects of the invention the method comprises, when the master control unit ceases operation as master control unit, to communicate a change of master to the at least one other control unit. A control unit operating as a slave control unit may then commence operation as master control unit. In this way a master control unit may signal that it is about to cease operation, so that either a new master can be selected according to the above, or the master signalling which control unit that is assume the role of master.According to aspects of the invention, the control units of the energy storage users are identical control units, or comprises partially the same software portions regarding the invention. In this way, the control units may be designed to comprise the same software, and operate in the same way, so that the control units thereby may also provide redundancy in terms of, e.g., selecting control unit to operate as master control unit.According to aspects of the invention, the energy storage users comprise at least two vehicle propulsion systems, each comprising at least one power source in the form of an electrical machine using the energy storage, and the vehicle operator manoeuvrable means comprise throttle means, where each of the vehicle propulsion systems comprise separate throttle means to allow for separate operator controlled power requests from the vehicle propulsion systems. The invention is hence highly usable in vehicles where two or more separate propulsion systems are present, and where the vehicle propulsion systems are individually controllable by an operator of the vehicle. Such propulsion systems are common in sea and air vehicles.According to aspects of the invention, the vehicle propulsion system comprises, in addition, at least one internal combustion engine, where the at least one electrical machine and the at least one internal combustion engine are configured to be selectively connectable for propulsion of the vehicle, e.g., through selectable connection to an output shaft. In this way, the at least one electrical machine of a vehicle propulsion system may independently provide for the propulsion. Also, the at least one internal combustion engine may independently provide for the propulsion. As a further alternative the at least one electrical machine and the at least one internal combustion engine may simultaneously be connected to, e.g., an output shaft to cooperate in the propulsion of the vehicle.According to aspects of the invention, an energy storage user in the form of a vehicle propulsion system according to the above may further provide for a charging of the electric energy storage system by applying a load on the at least one internal combustion engine using the at least one electrical machine so that the at least one electrical machine may charging the electric energy storage through generator operation when driven by the at least one internal combustion engine.According to aspects of the invention, the master control unit is further configured to control activation and deactivation of the energy storage for use as power source for the electric energy users. The master control unit may hence control all functions of the energy storage, such as turning on or off the energy storage.According to aspects of the invention, the electric energy storage is controlled by a control unit that is not associated with a user, where this control unit may determine maximum total charging and discharging limits that apply to the energy storage. This data may then be communicated to the master control unit which performs the actual allocation of resource based on the received maximum total charging and discharging limits. In this way it can be ensured in an efficient manner that the total charging and discharging applied to the energy storage by the plurality of energy storage users will not violate the determined limits for the energy storage, while still providing for a more efficient control than if the control unit controlling the energy resource would carry out the allocation.According to aspects of the invention, the energy storage users comprise one or more from: vehicle propulsion system, battery heater, PTO (Power Take-off), air-conditioning system, or any other type of user that may use a shared energy storage resource and be independently controlled in relation to other users or by operator controllable means.According to aspects of the invention, information regarding the control units participating in the energy storage control according to the invention, and associated load, may be stored beforehand, e.g., in a central database in the vehicle, which the master control unit may interrogate to obtain the desired knowledge of a specific control unit and the load that is associated with its user. Data of this kind may also already be available by being stored in the control units.The master control unit may then utilise information of this kind in order to, e.g., properly prioritize loads that are to be assigned resources from the energy storage. For example, a vehicle propulsion system may be prioritized over a heating function. The stored knowledge of the control units may also be utilized in the selection of master control unit.According to aspects of the invention, the master control unit requests information that is required to properly assign resources from the control units from the other control units, to thereby get the necessary knowledge of the users of the energy storage.According to a further aspect, the invention relates to a master control unit for controlling use of an electric energy storage of a vehicle. It will be appreciated that all that has been described for the method aspects of the invention is applicable also to master control unit aspects of the invention. Thus, all the aspects described for methods according to the invention may be performed by the master control unit, which may be a device. The master control unit and its aspects have advantages corresponding to the advantages discussed above with regard to the various aspects of methods according to the invention.According to another aspect of the invention, aforementioned and further objectives are achieved through a vehicle comprising a master control unit according to aspects of the invention.According to a further aspect, the invention relates to a computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method according to aspects of the invention.According to an aspect, the invention relates to a computer-readable medium comprising instructions which, when executed by a computer, cause the computer to carry out the method according to aspects of the invention.Further advantageous aspects of the method, the control arrangement, the vehicle, the computer program, and the computer-readable medium according to the invention will emerge from the detailed description.Brief description of the drawingsAspects of the invention will be illustrated in more detail below, along with the enclosed drawings, and where:Fig. 1A shows a schematic view illustrating an exemplary vehicle comprising energy resource users in which aspects of the invention may be implemented;Fig. 1B illustrates aspects of the energy resource users of Fig. 1A more in detail;Fig. 2A shows a flow chart illustrating an exemplary method according to aspects of the invention;Figure 2B shows a flow chart illustrating methods according to further aspects of the invention;Fig. 3 illustrates a further example of energy resource users of a vehicle;Fig. 4 shows a control arrangement, in which a method according to any one of the aspects described herein may be implemented.Detailed descriptionFig. 1A illustrates a first exemplary aspect of parts of a vehicle 100 in which aspects of the invention may be utilised. According to the disclosed example, the vehicle is a sea vehicle such as a boat or a ship, but the vehicle may also be, e.g., a land or an air vehicle. The invention is applicable for various types of energy storage users, but will first be exemplified with reference to a vehicle comprising two energy storage users in the form of vehicle propulsion systems.According to the particular illustrated example, the vehicle is a hybrid vehicle comprising a first and a second vehicle propulsion system 101, 102. Each of the first and second vehicle propulsion systems 101, 102 provides power to an output shaft 103, 104, respectively. The output shafts are, according to the present example, propelling propellers 105, 106 for propulsion of the vehicle 100. According to aspects of the invention, the vehicle propulsion systems 101, 102 may provide the propulsion power through other means than propellers, such as, e.g., jet engines, water jets etc.Each of the vehicle propulsion systems 101, 102 comprises an internal combustion engine 111, 112 and an electrical machine 121, 122. The propulsion systems 101, 102 are independently controlled propulsion systems, where each propulsion system comprises vehicle operator controllable means, such as, in the present example, separate throttles 107, 108 for requesting power from the vehicle propulsion systems 101, 102. The vehicle operator may hence request different powers from the two propulsion systems using the separate throttles. Such power requests may be common in particular in sea and air vehicles.The first and second vehicle propulsion systems 101, 102 share an energy storage, according to the present example a high-voltage battery, 130. The vehicle propulsion systems 101, 102 may utilize resources of the battery 130 to provide for propulsion of the vehicle 100 through the use of power drawn from battery 130. The electrical machines 101, 102 may also be used to charge the battery 130 by acting as a load on the internal combustion engines 111, 112, respectively. The vehicle 100 hence comprises two individual vehicle propulsion systems 101, 102 that share a common energy resource 130.Further according to the specific illustrated example, the vehicle propulsion systems 101, 102 may be configured such that power may be provided to the output shaft of the vehicle propulsion system selectively using the internal combustion engine 121, 122 or the electrical machine 101, 102 only, so that hence any one of the power sources of a vehicle propulsion system may be utilized in the propulsion of the vehicle 100. According to aspects of the invention, and according to the present example, both power sources of a vehicle propulsion system may also simultaneously provide power to the output shaft 103. According to the example, the electrical machines 121, 122 may also be utilized as generators for charging by acting as a load on the internal combustion engines 111, 112, respectively.This is further illustrated in Fig. 1B, which shows an exemplary coupling mechanism for providing the selective connection of the power sources 111, 121 of vehicle propulsion system 101 to the output shaft 103, and also each other. The internal combustion engine 111 is schematically illustrated, as well as an output shaft 111 A of the internal combustion engine 111. Furthermore, the figure also schematically illustrates the stator 121 A and rotor 121 B of the electrical machine 121. The electrical machine 121 can be connected to the output shaft 103 using coupling sleeve 124. The coupling sleeve 124 is used to selectively connect the rotor of 121 B of the electrical machine 121 to the output shaft 103. The figure illustrates the coupling sleeve 124 in the disconnected state, hence not connected to the output shaft 103 or the internal combustion engine 111, whereas dotted lines indicate the position of the coupling sleeve 124 when the electrical machine 121 is connected to the output shaft 103.Similarly, the output shaft 111 A of the internal combustion engine 111 can be selectively connected to the output shaft 103 using coupling sleeve 114. The figure illustrates the coupling sleeve 114 in the connected state, and dotted lines indicate the position of the coupling sleeve 114 when the internal combustion engine 111 is disconnected from the output shaft 103.Consequently, the electrical machine 121 can be configured to solely power the output shaft 103 by engaging coupling sleeve 124 and disengaging coupling sleeve 114. Correspondingly, the internal combustion engine 111 can be configured to solely power the output shaft 103 by engaging coupling sleeve 114 and disengaging coupling sleeve 124, i.e. the situation in the figure. The two power sources 111, 121 may also simultaneously be used to power the output shaft 103 by engaging both coupling sleeves 114, 124. It is also possible to charge the battery 130 by operating the electrical machine 121 as a generator. In this case the coupling sleeves 114, 124 are also both in connected state as when both power sources are used for propulsion, but where instead the electrical machine 121 is controlled to apply a load on the output shaft of the internal combustion engine 111.As was explained above, the sharing of a common energy storage, such as a battery in the present example, may give rise to problems when independently controlled systems are to share the same battery resources. This is because each of the vehicle propulsion systems 101, 102 are controlled by individual control units, where vehicle propulsion system 101 is controlled by a control unit ECU1 and the vehicle propulsion system 102 is controlled by a control unit ECU2, and where in addition separate throttles 107, 108 are used for the propulsion systems 101, 102. As was also mentioned above, the solution to problems of this kind is to design the complete system, that is, battery and vehicle propulsion systems according to the present example as one integrated system being controlled by a single control unit. This, however, may not always be desirable but it may, instead, as in the illustrated example, be preferred to use independent systems, such as vehicle propulsion systems according to the present example where each vehicle propulsion system is controlled by its designated control unit, i.e. control units ECU1, ECU2 in the figure. It is to be noted that control unit ECU1 may be integrated with the first vehicle propulsion system 101 and the control unit ECU2 may be integrated with the second vehicle propulsion system 102.One alternative would be to have a battery control unit that would be responsible for allocating the battery resources to the various battery users of the vehicle it has been realized, however that system performance may be improved if a control unit other than a battery control unit is responsible for controlling which battery resources that are to be allowed to be used by a particular battery user.According to the invention, it is therefore provided a solution where a control unit of one of the users of the battery is selected as a master control unit that is assigned the task of controlling the battery resources. Hence, a control unit that is responsible for controlling a battery user is used as master control unit for controlling their battery resources and hence how these battery resources are to be distributed between various users of the battery that may request such resources. The master control unit is hence selected among control units that are associated with battery users. Control units that are associated with other battery users and that are not selected as master control unit form slave control units, e.g. by being assigned the role of the slave control unit when another control unit has been assigned as master control unit. A first example of a method according to the invention is illustrated in figure 2A.The method according to Fig. 2A starts in step 220, where a request for an energy storage resource, such as power / current from the high-voltage battery 130, is received from a slave control unit where the requested battery resource is to be used by the user associated with the control unit. According to the present example, control unit ECU1 is selected as master control unit and consequently the control unit ECU2 form a slave control unit. Hence, control unit ECU1 may receive a request from control unit ECU2, where the request may comprise a request for battery resources from the battery 130 to be used by vehicle propulsion system 102.In step 240, following the reception of the request from control unit ECU2, the master control unit ECU1 transmits to the slave control unit ECU2 a battery resource usage limit that limits the battery resources that the second vehicle propulsion system may use with regard to the battery 130. The control unit ECU1 hence determines what resources may be used by the second vehicle propulsion system. Evidently, the master control unit ECU1 also controls the first vehicle propulsion system and hence which battery resources that may be used by this vehicle propulsion system as well. The control unit ECU2 may then control the battery usage of vehicle propulsion system 102 such that the usage is kept within the received limit.According to the invention it is hence provided a solution that may utilize a control unit associated with a battery user as a master control unit that controls battery resources for all users that utilize resources of the battery. In this way, separate independent energy resource users, such as battery users may share an energy resource, such as a battery while still ensuring efficient and reliable control of the battery.According to the illustrated example of Fig. 1A, two battery users share a common battery, and the battery users are illustrated as vehicle propulsion systems. It is to be understood that any number of users may share a common battery, where each user may be associated by a control unit, and where all users may be associated with different control units. In such cases one control unit is still selected as master control unit and the two or more, in such cases, additional control units form slave control units that may send requests for resources to the master control unit, which then transmits resource usage limits to the slave control units limiting the resources that the users may use.Fig. 3 schematically illustrates a general example in this regard, where four energy resource users 301-304 share a common electrical energy storage, such as a highvoltage battery 330. Each of the users 301-304 are controlled by a control unit ECU1-ECU4, respectively. These users 301-304 may be of a same or different kind, where each of the users comprises operator manoeuvrable means for requesting power from the user, respectively. Any of the control units ECU1-ECU4 may be selected as master control unit, and the remaining control units may operate as slave control units. For example, control unit ECU1 may be selected as master control unit and control units ECU2-ECU4 thereby form slave control units.Further to the invention, a request for battery resource may comprise, for example, a request for power to be drawn from the battery and / or a current to be drawn from the battery. The request may also, in case the battery user comprises generator capabilities as explained above, comprise a request for charging the battery, where, again, the request may comprise a request for charging using a certain power, or charging current.When the battery users form individual, independent users, that is, users that do not depend on the other users, they may, as illustrated, comprise vehicle operator manoeuvrable means for allowing the vehicle operator to request, e.g. a power to be applied by the user. For example, in case the battery users are vehicle propulsion systems, the user may request different power levels from the vehicle propulsion systems. It is to be noted that according to aspects of the invention, each battery user comprises separate vehicle operator manoeuvrable means for requesting power from the users, respectively. Hence, with regard to the example of Fig. 3, each of the users may comprise separate vehicle operator manoeuvrable means, where such means may be any kind of control that allows the user to adjust the power of the user with a resulting request for power to be transmitted by the associated control unit. It is also to be noted that the battery users need not be vehicle propulsion systems, but may consist of any other type of user where a vehicle operator may request certain power to be applied by the user using operator manoeuvrable means. Such users may comprise, for example, vehicle propulsion systems, battery heaters, PTO (Power Takeoff), air-conditioning systems, or any other type of user that may use a shared energy storage resource and be independently controlled in relation to other users or be individually controlled by a vehicle operator. The users may also form a combination of vehicle propulsion systems and other users.According to aspects of the invention, the method also comprises the step of selecting a control unit as master control unit. A further exemplary method is illustrated in Fig. 2B, which comprises an additional step 210 prior to step 220 in Fig. 2A, wherein the control unit to act as master control unit is selected.The selection of the control unit as master control unit in step 210 may be carried out in various different ways. For example, one or more of the control units of associated energy storage users may be configured to detect whether there is already a master control unit present. The control units may communicate using any suitable communication means, where such means are exemplified below in the discussion of Fig. 4. This detection may be configured to be carried out, e.g., each time a control unit is powered up, or when the control unit for some reason has lost connection or otherwise lost knowledge of the current system status. A control unit may commence operation as a slave control unit when presence of a control unit already operating as master control unit is detected. Conversely, in case no master control unit is detected, the control unit may instead commence operation as a master control unit. The role of master control unit may hence switch between control units, in dependence on, e.g., the order in which the control units are powered up.The control units may also be configured to select a master control unit among themselves. This may be carried out, for example, by providing the users associated with the control units with unique identities, or alternatively or in addition, provide the control units with unique identities. The control units may then signal the unique identities to each other, and the control unit to form master control unit may be selected based on the unique identities. For example, rules regarding selection based numbering or other types of identities may be used in this regard. The unique identities may be software encoded identities, but may also be hardware encoded unique identities, where this may be carried out, e.g., by jumpers, switches such as, e.g., DIP switches or similar means.The control units may hence communicate the unique identities to each other, and the control units may be configured to carry out the selecting of a control unit as master control unit based on the communicated unique identities, where this may be carried out according to a set of rules, so that each control unit will assume the role of master or slave in dependence of the unique identity of the control unit in relation to the received identities of the one or more other control units. According to another example, one of the control units may be configured to perform the selecting, where this may be carried out also based on the identities, and where the control unit may signal the roles to the other control units that are associated with users of the energy storage.According to aspects of the invention, the unique identities are utilised in the selection of master control unit such that a same control unit is selected as master control unit each time the control units are simultaneously powered up. This may provide for a simple way of performing the selecting. Still, the role of master may switch between control units as exemplified below, and also, e.g., if the control unit that is predestined to be master for some reason is not in operation.According to aspects of the invention, the master control unit regularly communicate master messages, which may comprise, e.g., the resource limits that the various users are to apply, or simply be messages that indicates that the master is present and in operation. The one or more slave control units may thereby also regularly receive the master messages, and if the master for some reason stop communicating the messages a slave control unit may take over the operation as master control unit, where the selection of a new master may be carried out according to the same principles as was first applied.Furthermore, in case the control unit that previously operated as master control unit resumes operation there will already be a master control unit present, and the previous master may thereby resume the operation in the role of slave control unit instead.There may also exist situations when a master control unit needs to stop operation, where this may then be carried out in a controlled manner where the master control unit may signal to a slave control unit to take over operation, whereupon the slave control unit starts operating as master.With further regard to the energy storage usage limit that the master control unit transmits to the one or more slave control units in step 240, the method may also comprise a step 230, where an energy storage resource usage limit is determined for a user based on the received request for resources. The request for an energy storage resource by a slave control unit to be used by a user may be determined based on user individual vehicle operator manoeuvrable means such as the throttles exemplified above.In case only one user requests resources, the case may be that the requested resources may be allowed. On the other hand, in case there are a plurality of users that request resources, and where the overall request exceeds the capacity of the energy storage the master control unit may determine that the users can only use a portion of the requested resources. The master control unit may also determine that one user at a time may use the energy store. The resource usage limit may, for example, limit the maximum power and / or current that the user may consume from the energy storage, where different users may be assigned different limits. In case the user operates as generator, the limit may also, e.g., comprise a maximum charging power and / or current that the user must respect when charging the electric energy storage.According to an aspect of the invention, it is provided a control unit for carrying out the methods according to the invention. The control unit is configured to receive, from a slave control unit a request for an energy storage resource to be used by its associated user, and to transmit, to the slave control unit from which the request was received, an energy storage resource usage limit allocated to the user associated with that slave control unit.The control unit ECU1, e.g. a device or a control device, according to the invention may be configured to perform all aspects that have been described with regard to methods.Hence the control arrangement ECU1 is provided with the above-described advantages for the various aspects of the invention. The invention also relates to a vehicle 100 including the control arrangement ECU1.Fig. 4 illustrates a control arrangement 400 / ECU1, which may be utilized to carry out the invention. The control arrangement 400 / ECU1 comprises a computing unit 401, which can be constituted by essentially any suitable type of processor or microcomputer, e.g., a circuit for digital signal processing (Digital Signal Processor, DSP), or a circuit having a predetermined specific function (Application Specific Integrated Circuit, ASIC). The computing unit 401 is connected to a memory unit 402 arranged in the control arrangement 400 / ECU1, which memory unit provides the computing unit 401 with, e.g., the stored program code and / or the stored data which the computing unit 401 requires to be able to perform computations. The computing unit 401 is also arranged to store partial or final results of computations in the memory unit 402.In addition, the control arrangement 400 / ECU1 is provided with devices 411, 412, 413, 414 for receiving and transmitting input and output signals. These input and output signals can contain waveforms, impulses, or other attributes which, by the devices 411, 413 for the reception of input signals, can be detected as information and can be converted into signals which can be processed by the computing unit 401. These signals are then made available to the computing unit 401. The devices 412, 414 for the transmission of output signals are arranged to convert signals received from the computing unit 401 in order to create output signals by, e.g., modulating the signals, which can be transmitted to other parts of and / or systems in the vehicle 100.Each of the connections to the devices for receiving and transmitting input and output signals can be constituted by one or more of a cable; a data bus, such as a Controller Area Network CAN bus, a Media Orientated Systems Transport MOST bus, or some other bus configuration; or by a wireless connection. A person skilled in the art will appreciate that the above-stated computer can be constituted by the computing unit 401 and that the above- stated memory can be constituted by the memory unit 402.Control systems in modern vehicles commonly comprise communication bus systems consisting of one or more communication buses for linking a number of electronic control units, ECU's, or controllers, and various components located on the vehicle. Such a control system can comprise a large number of control units and the responsibility for a specific function can be divided amongst more than one control unit. Vehicles of the shown type thus often comprise significantly more control units than are shown in Figs. 1A, 3 and 4, which is well known to the person skilled in the art within this technical field.The invention may be implemented by the one or more above mentioned control units ECU1-ECU4, and in particular in more than one control unit, e.g., all control units participating in the control of the energy storage resources. The invention can also, however, be implemented wholly or partially in one or more other control units being present in the vehicle 100, or in one or more control unit dedicated to the invention.Here and in this document, units are often described as being arranged for performing steps of the method according to the invention. This also includes that the units are designed to and / or configured to perform these method steps.Control units and other units may be logically separated but physically implemented in the same unit or can be both logically and physically arranged together. These units may, e.g., correspond to groups of instructions, which can be in the form of programming code, that are input into, and are utilized by a processor / computing unit 401 when the units are active and / or are utilized for performing its method step, respectively.The person skilled in the art will appreciate that the aspects described herein for controlling energy storage resources may also be implemented in a computer program, which, when it is executed in a computer, instructs the computer to execute the method. The computer program is usually constituted by a computer program product 403 stored on a non-transitory / non-volatile digital storage medium, in which the computer program is incorporated in the computer-readable medium of the computer program product. The computer-readable medium comprises a suitable memory, such as, e.g.: Read-Only Memory ROM, Programmable Read-Only Memory PROM, Erasable PROM EPROM, Flash memory, Electrically Erasable PROM EEPROM, a hard disk unit, etc.Finally, the invention is not limited to the above-described aspects, but the invention relates to, and encompasses, all of the different aspects that are included within the scope of the independent claims.

Claims

1. A method (100) performed by a master control unit (ECU1) for controlling use of an electric energy storage of a vehicle, the vehicle comprising at least two control units (ECU1, ECU2), each control unit (ECU1, ECU2) being associated with an energy consuming user (101, 102; 301-304), the master control unit (ECU1) being selected as a control unit of the at least two control units (ECU1, ECU2), wherein any additional control unit (ECU2) of the at least two control units (ECU1, ECU2) in addition to the master control unit (ECU1) form slave control unit(s) the method comprising:receiving (220), from a slave control unit (ECU2) a request for an energy storage resource to be used by its associated user (101, 102; 301-304);transmitting (240), to the slave control unit (ECU2) from which the request was received, an energy storage resource usage limit allocated to the user (101, 102; 301-304) associated with that slave control unit (ECU2).

2. A method (100) according to claim 1, further comprising:selecting (110) the master control unit (ECU1) among the at least two control units.

3. A method (100) according to claim 1 or 2, further comprising:allocating (130) the energy storage resource usage limit based on the received request.

4. A method (100) according to any one of the claims 1-3, wherein:the request for an energy storage resource to be used by a user (101, 102; 301-304) is determined based on user individual vehicle operator manoeuvrable means for requesting power from the user (101, 102; 301 -304).

5. A method (100) according to any one of the claims 1-4, further comprising: the master control unit communicating an electric energy storage resource usage limit to the slave control unit from which the request was received an energy storage resource usage limit that limits one or more from:maximum power and / or current consumption from the electric energy storage;maximum charging power and / or current for charging the electric energy storage.

6. A method (100) according to any one of the claims 1 -5, further comprising, when selecting a control unit as the master control unit:at least one of the at least two control units detecting whether there is a presence of a master control unit, wherein the control unit commences operation as a slave control unit when detecting presence of a master control unit; and wherein the control unit commences operation as a master control unit when presence of a master control unit is not detected.

7. A method (100) according to claim 6, wherein the control units of the at least two users (101, 102; 301-304) are configured to detect whether there is a presence of a master control unit when powered up.

8. A method (100) according to any one of the claims 1 -7, further comprising, when selecting a control unit as a master control unit:utilising unique identities of the users (101, 102; 301-304) associated with the control units, respectively, and / or unique identities of the control units, and selecting a control unit as master control unit based on the unique identities.

9. A method (100) according to claim 8, wherein the unique identities are software encoded and / or hardware encoded unique identities.

10. A method (100) according to claim 8 or 9, further comprising, when selecting a control unit as a master control unit:the control units communicating the unique identities to each other, and the control units determining the selecting of a control unit as master control unit based on the communicated unique identities.

11. A method (100) according to any one of the claims 8-10, further comprising: utilising the unique identities such that a same control unit is selected as master control unit each time the control units are simultaneously powered up.

12. A method (100) according to any one of the claims 1-11, further comprising:the master control unit regularly communicating master messages; the at least one slave control unit regularly receiving the master messages; andthe at least one slave control unit taking over operation as master control unit when the master control unit stops regularly communicating master messages.

13. A method (100) according to claim 12, further comprising:the previous master control unit commencing operation as slave control unit when resuming operation.

14. A method (100) according to any one of the claims 1-13, further comprising, when the master control unit ceases operation as master control unit:communicate a change of master to the at least one other control unit; and a control unit operating as a slave control unit commencing operation as master control unit.

15. A method (100) according to any one of the claims 1-14, wherein the energy storage users (101, 102; 301-304) comprise at least two vehicle propulsion systems comprising at least one power source as load, and the vehicle operator manoeuvrable means are throttle means, each of the vehicle propulsion systems comprising separate throttle means to allow for separate power requests from the vehicle propulsion systems.

16. A master control unit (ECU1) for controlling use of an electric energy storage of a vehicle, the vehicle comprising at least two control units (ECU1, ECU2), each control unit (ECU1, ECU2) being associated with an energy consuming user (101, 102; 301-304), the master control unit (ECU1) being selected as a control unit of the at least two control units (ECU1, ECU2), wherein any additional control unit (ECU2) of the at least two control units (ECU1, ECU2) in addition to the master control unit (ECU1) form slave control unit(s) the master control unit being configured to:receive (220), from a slave control unit (ECU2) a request for an energy storage resource to be used by its associated user (101, 102; 301-304);transmit (240), to the slave control unit (ECU2) from which the request was received, an energy storage resource usage limit allocated to the user (101, 102; 301-304) associated with that slave control unit (ECU2).

17. A vehicle (100) comprising a control unit according to claim 16.

18. A computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method according to any one of the claims 1 to 15.

19. A computer-readable medium comprising instructions which, when executed by a computer, cause the computer to carry out the method (200) according to any one of the claims 1 to 15.