A method for determining an operational characteristic of a trailing unit and control arrangement configured to perform the method

Abstract

A method, performed by a control arrangement (100) of a towing unit (2), for determining at least one operational characteristic of an electrically powered trailing unit (3) of a vehicle combination (1) comprising the towing unit (2). The method comprises a step of, when a reduction of the trailing unit's power contribution to the vehicle combination (1) is detected, estimating (S103) a total energy consumption and / or recovery of the trailing unit (3) since a point in time at which the trailing unit (3) had a predetermined first state of charge. The method further comprises a step of, based on the predetermined first state of charge and the estimated total energy consumption and / or recovery of the trailing unit (3), calculating (S104) a second state of charge of the trailing unit (3) at which the reduction of the trailing unit's power contribution to the vehicle combination (1) occurred. The method also comprises a step of, based on the calculated second state of charge of the trailing unit (3), determining (S107) a state of charge threshold for the trailing unit (3) at which the trailing unit's deliverable power is limited.

Description

[0001] A METHOD FOR DETERMINING AN OPERATIONAL CHARACTERISTIC OF A TRAILING UNIT AND CONTROL ARRANGEMENT CONFIGURED TO PERFORM THE METHOD

[0002] TECHNICAL FIELD

[0003] The present disclosure relates in general to a method for determining at least one operational characteristic of an electrically powered trailing unit of a vehicle combination, said vehicle combination further comprising a towing unit. The present disclosure further relates in general to a control arrangement configured to, when comprised in a towing unit of a vehicle combination, determine at least one operational characteristic of an electrically powered trailing unit of the vehicle combination.

[0004] The present disclosure also relates in general to a computer program and a computer-readable medium. The present disclosure also relates in general to a vehicle unit configured to, when comprised in a vehicle combination, act as a towing unit.

[0005] BACKGROUND

[0006] In modern heavy-duty vehicles, there may be different functions that rely on the ability of predicting future behavior of the vehicle. For example, a future behavior of the vehicle, if driven according to different possible driving strategies when travelling an upcoming road section, may be predicted for the purpose of identifying and selecting an appropriate driving strategy for the upcoming road section that meets various objectives. Examples of such objectives include, but are not limited to, energy efficiency, performance, road safety, and / or driver comfort. The vehicle may thereafter be controlled in accordance with the selected driving strategy as the vehicle travels said upcoming road section.

[0007] The development of electrically powered trailers, often also referred to as self-powered trailers, electric drive trailers or e-trailers, is gaining interest within the industry of heavy-duty vehicles. In contrast to a conventional trailer (which is a non-motorized vehicle unit), an e-trailer comprises its own drive unit configured to provide motive power to wheels of the trailer. Such a drive unit typically comprises at least one power unit in the form of an electrical machine, and a transmission arrangement. The transmission arrangement of the e-trailer may be a single-speedor a multi-speed transmission arrangement. An e-trailer may for example comprise one or more drive units in the form of electric drive axle(s), also known as e-axle(s). Since an e-trailer comprises its own drive unit, it can support a towing unit (such as a tractor truck), to which the e-trailer is connected, in meeting the desired total motive power demand for the vehicle combination. This can in turn lead to improved energy efficiency of the vehicle combination and / or an increase in available driving range. Some e-trailers may also be configured to recover electrical energy through regenerative braking and store this recovered energy in an energy storage device configured to power the drive unit(s) of the e-trailer. This may in turn further improve the energy efficiency and / or available driving range of the vehicle combination.

[0008] E-trailers are often developed to be used with different towing units, which in turn may be produced by different vehicle manufacturers. Therefore, e-trailers may typically be configured to be controlled according to their own control strategies. An e-trailer may, for example, be configured to be dynamically controlled with the aim of providing sufficient motive power to reach a substantially zero longitudinal force on the coupling device (e.g. a kingpin) connecting the e-trailer to the towing unit. The control strategies of e-trailers are often not, or at least not fully, integrated with the towing unit to which the e-trailers may be connected. Furthermore, a towing unit may often not have knowledge of the characteristics, such as capabilities or limitations, of an e-trailer connected thereto. This may sometimes lead to problems with some functionalities of a towing unit, especially such functionalities that rely on the ability of predicting future behavior of the towing unit. This may in turn lead to the towing unit not being controlled in the best way to meet a desired objective. Furthermore, this may affect the reliability when predicting available driving range for the towing unit based on energy stored onboard (as fuel and / or electrical energy), also known as distance-to-empty.

[0009] SUMMARY

[0010] The object of the present invention is to enable a towing unit to gain knowledge of an operational characteristic of an electrically powered trailing unit, comprised in the vehicle combination of the towing unit, also in cases where the electrically powered trailing unit is not fully integrated with the towing unit.

[0011] The object is achieved by the subject-matter of the appended independent claim(s).The present disclosure relates to a method, performed by a control arrangement of a towing unit, for determining at least one operational characteristic of an electrically powered trailing unit of a vehicle combination comprisingthe towing unit. The method comprises a step of, when a reduction of the trailing unit’s power contribution to the vehicle combination is detected, estimating a total energy consumption and / or recovery of the trailing unit since a point in time at which the trailing unit had a predetermined first state of charge. The method further comprises a step of based on the predetermined first state of charge and the estimated total energy consumption and / or recovery of the trailing unit, calculating a second state of charge of the trailing unit at which the reduction of the trailing unit’s power contribution to the vehicle combination occurred. Moreover, the method comprises a step of, based on the calculated second state of charge of the trailing unit, determining a state of charge threshold for the trailing unit at which the trailing unit’s deliverable power is limited.

[0012] The herein described method allows a towing unit to gain knowledge of a state of charge threshold for an electrically powered trailing unit, comprised in the vehicle combination of the towing unit, even if the towing unit is not fully integrated with the electrically powered trailing unit, said state of charge threshold resulting in the trailing unit’s deliverable power being limited, e.g., due to change in voltage of an energy storage device of the trailing unit, charge / discharge rate limitations, and / or control strategies of a battery management system associated with the energy storage device of the trailing unit.

[0013] Knowledge of a state of charge threshold at which the trailing unit’s deliverable power is limited facilitates planning of a suitable driving strategy for the towing unit to meet desired objective(s), such as energy efficiency, performance, and / or road safety. Furthermore, it also enables more accurate predictions of distance-to-empty for the towing unit and / or the vehicle combination.

[0014] The method may further comprise a step of monitoring of the trailing unit’s power contribution to the vehicle combination through monitoring of a difference between expected and actual power utilization of the towing unit. This allows for the towing unit, or more specifically the control arrangement of the towing unit, to detect a reduction of the trailing unit’s power contribution to the vehicle combination even though the trailing unit is not integrated, or only partially integrated with, the towing unit.

[0015] The step of determining the state of charge threshold at which the trailing unit’s deliverable power is limited may be performed when it is assessed that the calculated second state ofcharge was a reason for the reduction of the trailing unit’s power contribution to the vehicle combination. Thereby, the accuracy and reliability when determining the state of charge threshold for the trailing unit may be improved. This is because it reduces the risk of a possible reduction of the trailing unit’s power contribution, caused by a reason other than a state of charge of the trailing unit being considered when determining the state of charge threshold at which the trailing unit’s deliverable power is limited.

[0016] The method may further comprises a step of assessing whether the calculated second state of charge was the reason for the detected limitation of the trailing unit’s power contribution to the vehicle combination based on whether the calculated second state of charge falls within a predefined state of charge range and / or whether the calculated second state of charge is deemed to be consistent with previously determined values of the second state of charge for the trailing unit. Consideration of whether the calculated second state of charge falls within a state of charge range, within which it is reasonable that a limitation in deliverable power may occur due to state of charge, is an easy and reliable way to reduce the risk of errors when determining the state of charge threshold. Similarly, consideration of whether the calculated second state of charge is sufficiently close to previously determined values of the second state of charge, derived through iteration of the steps of the method, increases the accuracy when determining the state of charge threshold.

[0017] The above described step of estimating total energy consumption and / or recovery of the trailing unit since the point in time at which the trailing unit had the predetermined first state of charge may for example be performed based on a predetermined model for the trailing unit. This facilitates calculating the second state of charge and improves the accuracy thereof, and thus also the reliability of the determined state of charge threshold at which the electrically powered trailing unit’s deliverable power is limited.

[0018] The method may further comprise a step of analyzing the trailing unit’s power contribution to the vehicle combination to thereby determine characteristics of the limitation of the trailing unit’s deliverable power when the determined state of charge threshold is passed. Knowledge of the characteristics of the limitation of the trailing unit’s deliverable power facilitates the planning of suitable driving strategy for the towing unit to meet desired objective(s) and / or enables more accurate estimations of distance to empty for the towing unit and / or the vehicle combination.The present disclosure further relates to a control arrangement configured to, when comprised in a towing unit of a vehicle combination, determine at least one operational characteristic of an electrically powered trailing unit of the vehicle combination. The control arrangement is configured to, when a reduction of the trailing unit’s power contribution to the vehicle combination is detected, estimate a total energy consumption and / or recovery of the trailing unit since a point in time at which the trailing unit had a predetermined first state of charge. The control arrangement is further configured to, based on the predetermined first state of charge and the estimated total energy consumption and / or recovery of the trailing unit, calculate a second state of charge of the trailing unit at which the reduction of the trailing unit’s power contribution to the vehicle combination occurred. Moreover, the control arrangement is configured to, based on the calculated second state of charge of the trailing unit, determine a state of charge threshold for the trailing unit at which the trailing unit’s deliverable power is limited.

[0019] The control arrangement provides the same advantages as described above with reference to the corresponding method for determining at least one operational characteristic of an electrically powered trailing unit of a vehicle combination comprising the towing unit.

[0020] The control arrangement may further be configured to monitor the trailing unit’s power contribution to the vehicle combination through monitoring of a difference between expected and actual power utilization of the towing unit.

[0021] According to an embodiment of the herein described control arrangement, the control arrangement may be configured to determine the state of charge threshold for the trailing unit at which the trailing unit’s deliverable power is limited when it is assessed that the calculated second state of charge was a reason for the reduction of the trailing unit’s power contribution to the vehicle combination.

[0022] The control arrangement may for example be configured to assess that the calculated second state of charge was the reason for the detected limitation of the trailing unit’s power contribution to the vehicle combination when the calculated second state of charge falls within a predefined state of charge range and / or when the calculated second state of charge is deemed to be consistent with previously determined values of the second state of charge for the trailing unit.The control arrangement may be configured to estimate total energy consumption and / or recovery of the trailing unit since the point in time at which the trailing unit had the predetermined first state of charge based on a predetermined model for the trailing unit.

[0023] The control arrangement may further be configured to analyze the trailing unit’s power contribution to the vehicle combination to thereby determine characteristics of the limitation of the trailing unit’s deliverable power when the determined state of charge threshold is passed.

[0024] Moreover, the control arrangement may be configured to communicate with at least one of a user interface, a charger interface, a fleet management system, and a cloud service system for the purpose of determining the first state of charge of the trailing unit.

[0025] The present disclosure also provides a computer program comprising instructions which, when executed by the above described control arrangement, cause the control arrangement to perform the above described method for determining at least one operational characteristic of an electrically powered trailing unit of a vehicle combination comprising a towing unit in which the control arrangement is comprised.

[0026] Moreover, the present disclosure also relates to a computer-readable medium having stored thereon the computer program as described above.

[0027] The present disclosure also relates to a vehicle unit configured to, when comprised in a vehicle combination, act as a towing unit. The vehicle unit comprises the above described control arrangement configured to, when comprised in a towing unit of a vehicle combination, determine at least one operational characteristic of an electrically powered trailing unit of the vehicle combination. Said vehicle combination may for example be a land-based heavy-duty vehicle combination. The towing unit of the vehicle combination may for example be a tractor truck or a rigid truck, but is not limited thereto.

[0028] The vehicle unit configured to act as a towing unit when comprised in a vehicle combination may be a vehicle driven solely by a combustion engine. Alternatively, said vehicle unit may be a hybrid vehicle (such as a plug-in hybrid or a mild hybrid), a fully electric vehicle (such as a battery electric vehicle), or a fuel cell vehicle.BRIEF DESCRIPTION OF DRAWINGS

[0029] Fig. 1 schematically illustrates an example of a vehicle combination comprising a towing unit and a trailing unit,

[0030] Fig. 2 represents a flowchart schematically illustrating an exemplifying embodiment of the herein described method, performed by a control arrangement of a towing unit, for determining at least one operational characteristic of an electrically powered trailing unit of a vehicle combination comprisingthe towing unit,

[0031] Fig. 3 schematically illustrates a device that may comprise, consist of, or be comprised in the herein described control arrangement configured to, when comprised in a towing unit of a vehicle combination, determine at least one operational characteristic of an electrically powered trailing unit of the vehicle combination,, and

[0032] Fig. 4 illustrates a side view of an example of a vehicle in the form of a heavy-duty vehicle combination.

[0033] DETAILED DESCRIPTION

[0034] The invention will be described in more detail below with reference to exemplifying embodiments and the accompanying drawings. The invention is however not limited to the exemplifying embodiments discussed and / or shown in the drawings, but may be varied within the scope of the appended claims. Furthermore, the drawings shall not be considered drawn to scale as some features may be exaggerated in order to more clearly illustrate the invention or features thereof.

[0035] A vehicle is in the present disclosure considered to mean any means that may be used for transporting people and / or cargo. A vehicle may consist of a single vehicle unit. Examples of a vehicle consisting of a single vehicle unit include a car, a rigid truck, a tractor truck, a bus, an electrically powered trailer, and an electrically powered dolly, but are not limited thereto. Alternatively, a vehicle may constitute a vehicle combination comprising at least two vehicleunits which are physically linked when travelling. A vehicle combination may be a vehicle comprising a towing vehicle unit and at least one trailing vehicle unit. Examples of vehicle combinations include a semi-trailer truck, a rigid truck pulling a semitrailer using a dolly, a vehicle train comprising a rigid truck and one or more full trailers, and an electrically powered dolly pulling a semitrailer or a full trailer, but are not limited thereto.

[0036] The terms “towing unit” and “towing vehicle unit” are used interchangeably herein, and are considered to mean a vehicle unit that, when comprised in a vehicle combination, constitutes the leading vehicle unit of the vehicle combination as seen in the primary direction of travel of said vehicle combination (in other words, as seen in the forward moving direction). A towing unit may typically be a tractor unit, such as a tractor truck or a rigid truck, to which at least one trailing unit may be connected. Alternatively, a towing unit may be an electrically powered dolly in such cases where said an electrically powered dolly acts as the leading vehicle unit of a vehicle combination, for example when towing a semitrailer of its own without the use of a tractor truck.

[0037] The terms “trailing unit” and “trailing vehicle unit” are used interchangeably herein, and are considered to mean a vehicle unit which, when comprised in a vehicle combination, is either directly physically connected to the leading vehicle unit, or connected to the leading vehicle unit via one or more other intermediate vehicle units. Thus, a trailing unit may for example be a trailer or a dolly.

[0038] Moreover, an “electrically powered trailing unit” is in the present disclosure considered to mean a trailing unit which comprises at least one power unit in the form of an electrical motor, which in turn is powered by an energy storage device. The electrical motor may be comprised in a powertrain of the trailing unit, said powertrain further comprising a transmission arrangement. The transmission arrangement may be a single speed transmission arrangement or a multispeed transmission arrangement. The powertrain of the trailing unit may for example be an e-axle, but is not limited thereto.

[0039] Furthermore, in the present disclosure, the term “driver” is intended to mean a human controlling a vehicle or a vehicle unit (such as a towing unit), and is thus intended to encompass both a driver present onboard a vehicle (such as a towing unit) as well as a human controlling the vehicle or vehicle unit remotely, for example from a control center or the like.The herein described method is a method, performed by a control arrangement of a towing unit, for determining one or more operational characteristics of an electrically powered trailing unit of a vehicle combination comprising said towing unit. The method is primarily developed to be used in such cases where the electrically powered trailing unit is not fully integrated with the towing unit of the vehicle combination. In otherwords, the method is intended to be used in such cases where the towing unit is unable to determine operational characteristics of the electrically powered trailing unit through direct communication with the electrically powered trailing unit. In such situations, the electrically powered trailing unit may be described as a nonintegrated electrically powered trailing unit. It should however be noted that the herein described method may also be used in other situations, for example in cases of temporary failure in communication such that the towing unit may not retrieve desired information directly from the electrically powered trailing unit.

[0040] The one or more operational characteristics, determined through the herein described method, comprises at least one state of charge threshold (herein also denominated “SOC threshold”) for the trailing unit at which the trailing unit’s deliverable power is limited due to the state of charge of the trailing unit (or more specifically, due to the state of charge of an energy storage device of the trailing unit). More specifically, the one or more operational characteristics may comprise a first SOC threshold for the trailing unit which, if passed, results in a limitation of the trailing unit’s deliverable motive power, and / or a second SOC threshold for the trailing unit which, if passed, results in a limitation of the trailing unit’s deliverable auxiliary braking power.

[0041] Knowledge of a SOC threshold at which the trailing unit’s deliverable power is limited may e.g., allow for improvements when planning a driving strategy for the towing unit of the vehicle combination to meet desired objective(s), and also allows for more accurately determining a distance-to-empty for the towing unit and / or the vehicle combination.

[0042] In an electrically powered vehicle unit (such as an electrically powered trailing unit), the deliverable motive power of the electric motor decreases as the energy storage device approaches a low state of charge. This reduction in available power output may be due to a decline in voltage of the energy storage device, an increase in internal resistance of the energy storage device, and / or the operation of the battery management system (BMS), which imposes current limitations to prevent excessive discharge and protect energy storage device longevity. Additionally, electrochemical constraints within the energy storage device may further limit its ability to sustain high discharge rates at low state of charge. This in turn means that the motivepower that the trailing unit may provide to a vehicle combination may be limited at a certain SOC threshold (i.e. the first SOC threshold described above).

[0043] Conversely, during regenerative braking of an electrically powered vehicle unit, the ability of the energy storage device to accept charge is diminished at high SOC. As the energy storage device approaches full charge, its internal resistance increases, and the BMS may restrict (or even disable) regenerative braking to prevent overcharging, which could otherwise lead to degradation of the energy storage device, excessive heating, or safety risks. Because regenerative braking relies on converting kinetic energy into stored electrical energy within the energy storage device, the reduced capacity to absorb additional charge at high SOC will result in reduced regenerative braking power. This in turn means that the auxiliary braking power that the trailing unit may provide to a vehicle combination may be limited at a certain SOC threshold (here, the second SOC threshold described above).

[0044] The herein described method for determining one or more operational characteristics of an electrically powered trailing unit of a vehicle combination comprises a step of, when a reduction of the trailing unit’s power contribution to the vehicle combination is detected, estimating a total energy consumption and / or recovery of the trailing unit since a point in time at which the trailing unit had a predetermined first state of charge. More specifically, the step of estimating the total energy consumption and / or recovery of the trailing unit, since a point in time at which the trailing unit had a predetermined first state of charge, is performed when a non-predicted reduction of the trailing unit’s power contribution to the vehicle combination is detected. A nonpredicted reduction of the trailing unit’s power contribution is herein considered to mean a reduction which is unforeseen, at least in term of point in time at which it occurs and / orwith respect to the size thereof, reduction of the power contribution to the vehicle combination.

[0045] The above mentioned predetermined first state of charge of the trailing unit may for example be derived from a user interface, such as a user interface configured to allow a driver to input data to the towing unit. The predetermined first state of charge may alternatively, or additionally, be derived from a charger interface (which can also be denominated as a charging station interface) configured to communicate with the towing unit, a fleet management system associated with the towing unit and the trailing unit, or a cloud service system configured to communicate with the towing unit and trailing unit, but is not limited thereto. In some (rare) cases, the predetermined first state of charge of the trailing unit may be a first state of charge determined by the towing unit, e.g. through detection of an interruption of power contributionfrom the trailing unit due to the trailing unit being completely discharged or fully charged (the latter occurring as a result of regenerative braking of the trailing unit).

[0046] The above mentioned detection of a reduction of the trailing unit’s power contribution to the vehicle combination may be done while monitoring of the trailing unit’s power contribution to the vehicle combination. In other words, the method may also comprise a step of monitoringthe trailing unit’s power contribution to the vehicle combination. Said step of monitoring the trailing unit’s power contribution may be made solely forthe purpose of enabling detection of an (unforeseen) reduction of the trailing unit’s power contribution to the vehicle combination when performingthe herein described method, or may be made primarily for other purposes without departing from the present disclosure. In view of the herein described method being performed by a control arrangement of the towing unit of the vehicle combination, the step of monitoring of the trailing unit’s power contribution to the vehicle combination may be performed through monitoring of a difference between an expected power utilization of the towing unit and an actual power utilization of the towing unit. Said expected power utilization may for example be estimated based on historical data of power utilization of the towing unit when comprised in a vehicle combination comprising an electrically powered trailing unit, and / or estimated based on a predetermined model therefore. Moreover, said expected power utilization of the towing unit mayfor example be determined based on an assumption that the trailing unit is controlled in accordance with a predetermined control strategy for the trailing unit, for example a control strategy resulting in a predefined longitudinal force on a coupling device connecting the trailing unit (directly or via one or more intermediate vehicle units) to the towing unit. Furthermore, the expected power utilization of the towing unit may be determined in consideration of a selected driving strategy for the towing unit and road characteristics (including for example topography and curvature). The actual power utilization of the towing unit may in turn be determined based on sensed / measured operational parameters of the towing unit.

[0047] The above described step of estimating a total energy consumption and / or recovery of the electrically powered trailing unit (since a point in time at which said trailing unit had the predetermined first state of charge) mayfor example be performed using a predetermined model therefore. Such a predetermined model may suitably take into account factors such as road characteristics (such as topography and road curvature), mass, travelling speed, acceleration / deceleration, energy losses due to rolling resistance and / or aerodynamic drag, as well as historical data regarding energy consumption rate and energy recovery rate. Such historical data mayfor example be derived from other vehicle units having the same or similarconfiguration. Methods for determining a model for estimation of energy consumption and / or recovery of vehicle units (such as an electrically powered trailing unit of a vehicle combination) have been described elsewhere, and any previously known method for determining such a model may be utilized without departing from the present disclosure. However, as an example, the model may be determined starting from Newton’s second law of motion which defines the net force at any instant of time. It is well known in the art that the net force on a vehicle (such as a vehicle combination) is given by Equation 1 :

[0048] FJ'rac = F_acc + F_incl + F_air + F_roll (Eq. 1)

[0049] wherein F_Trac is the total motive force, F_acc is the acceleration force, F_incl is the force resulting from road inclination, F_air is the aerodynamic drag force, and F_roU is the rolling resistance force.

[0050] Both the towing unit and an electrically powered trailing unit may each contribute to the total motive force of the vehicle combination. However, since the motive force provided by the towing unit is known to the towing unit, the motive force provided by the electrically powered trailing unit may be determined according to Equation 2:

[0051] F_Trac_tr ailing = F_Trac — F_Trac_towing (Eq. 2)

[0052] wherein F_Trac_trailing represents the motive force provided by the electrically powered trailing unit to the vehicle combination and F_Trac_towing represents the motive force provided by the towing unit to the vehicle combination.

[0053] Based on the motive force provided by the electrically powered trailing unit, the (instantaneous) motive power provided by the electrically powered trailing unit, P_trailing, is given by Equation 3:

[0054] ^trailing = F_Trac _tr ailing * v (Eq. 3)

[0055] wherein v represents the travelling speed of the electrically powered trailing unit, which in turn corresponds to the travelling speed of the vehicle combination.

[0056] The total energy consumption and / or recovery, E, is in turn given by integrating the instantaneous motive power over time according to Equation 4:E = f P -trailing (t)dt (Eq. 4)

[0057] The herein described method further comprises a step of, based on the predetermined first state of charge and the estimated total energy consumption and / or recovery of the trailing unit, calculating a second state of charge of the trailing unit at which the reduction of the trailing unit’s power contribution to the vehicle combination occurred.

[0058] Moreover, the method comprises a step of, based on the calculated second state of charge of the trailing unit, determining a SOC threshold for the trailing unit at which the trailing unit’s deliverable power is limited. According to one alternative, the SOC threshold for the trailing unit at which the trailing unit’s deliverable power is limited may be determined to correspond to the calculated second state of charge of the trailing unit. According to another alternative, the SOC threshold may be determined based on a plurality of said calculated second state of charge, each derived from an iteration of the steps of (i) when a reduction of the trailing unit’s power contribution to the vehicle combination is detected, estimating a total energy consumption and / or recovery of the trailing unit since a point in time at which the trailing unit, and (ii) based on the predetermined first state of charge and the estimated total energy consumption and / or recovery of the trailing unit, calculating a second state of charge of the trailing unit at which the reduction of the trailing unit’s power contribution to the vehicle combination occurred. In such a case, the state of charge threshold may for example be determined to correspond to an average or median of said plurality of calculated second state of charge (each calculated second state of charge derived through an iteration of the above mentioned steps (i) and (ii)).

[0059] Naturally, an unforeseen reduction of the trailing unit’s power contribution to the vehicle combination may occur due to other factors than the state of charge of the electrically powered trailing unit (or more specifically, state of charge of the energy storage device of the electrically powered trailing unit). Therefore, the step of determining the SOC threshold at which the electrically powered trailing unit’s deliverable power is limited may accordingto an embodiment of the herein described method be performed when it is assessed that the calculated second state of charge was a reason for the reduction of the trailing unit’s power contribution to the vehicle combination. In other words, the method may further comprise a step of assessing whether the calculated second state of charge was the reason for the detected reduction of the trailing unit’s power contribution to the vehicle combination. Thereby, the accuracy andreliability when determining the state of charge threshold for the trailing unit may be improved. This is because it reduces the risk of a possible reduction of the trailing unit’s power contribution, caused by a reason other than a state of charge of the trailing unit (e.g. due to a temporary reduction of power contribution to avoid overheating of one or more constituent components of a powertrain of the trailing unit), being considered when determining the state of charge threshold at which the trailing unit’s deliverable power is limited.

[0060] The above described step of assessing whether the calculated second state of charge was the reason for the detected reduction may comprise ruling out possible other causes for said reduction. Alternatively, or additionally, the step of assessing whether the calculated second state of charge was the reason for the detected reduction of the trailing unit’s power contribution to the vehicle combination may comprise considering whether the calculated second state of charge falls within a predefined state of charge range (within which it is reasonable to assume that a power reduction may occur). For example, in case calculated second state of charge would be about 50%, it is unlikely that the reduction of power contribution occurred due to the state of charge of the trailing unit, whereas if the calculated second state of charge is close to an end value of the available state of charge window of the trailing unit, it is likely that the reduction of power contribution occurred due to the state of charge. Alternatively, or additionally, the step of assessing whether the calculated second state of charge was the reason for the detected reduction of the trailing unit’s power contribution to the vehicle combination may comprise consideringwhetherthe calculated second state of charge is deemed to be consistent with previously determined values of the second state of charge for the trailing unit. In such a case, the method is naturally reiterated for the purpose of determining a plurality of the calculated second state of charge, which in turn enables a comparison and / or statistical analysis of the plurality of calculated second state of charges.

[0061] The method may further comprise a step of analyzing the trailing unit’s power contribution to the vehicle combination to thereby determine characteristics of the limitation of the trailing unit’s deliverable power when the determined SOC threshold for the trailing unit is passed. This may for example comprise determining a curve of reduced deliverable power from the trailing unit as a function of state of charge, but is not limited thereto.

[0062] Accordingto a first embodiment of the herein described method, the at least one operational characteristic of the electrically powered trailing unit comprises (or constitutes) a first SOC threshold for the trailing unit at which the trailing unit’s deliverable motive power is limited.According to said first embodiment, the step of estimating a total energy consumption and / or recovery of the trailing unit since a point in time at which the trailing unit had a predetermined first state of charge is performed when a reduction of the trailing unit’s motive power contribution to the vehicle combination is detected. As previously mentioned, said reduction may be an unforeseen reduction at least in terms of the point in time and / orthe size of the reduction. Furthermore, in the first embodiment of the method, the step of calculating a second state of charge of the trailing unit comprises calculating a second state of charge of the trailing unit at which the reduction of the trailing unit’s motive power contribution to the vehicle combination occurred.

[0063] According to a second embodiment of the herein described method, the at least one operational characteristic of the electrically powered trailing unit comprises (or constitutes) a second SOC threshold for the trailing unit at which the trailing unit’s auxiliary braking power (or more specifically, regenerative braking power) is limited. According to said second embodiment, the step of estimating a total energy consumption of the trailing unit since a point in time at which the trailing unit had a predetermined first state of charge is performed when a reduction of the trailing unit’s auxiliary braking power contribution to the vehicle combination is detected. As previously mentioned, said reduction may be an unforeseen reduction at least in terms of the point in time and / or the size of the reduction. Furthermore, in the second embodiment of the method, the step of calculating a second state of charge of the trailing unit comprises calculating a second state of charge of the trailing unit at which the reduction of the trailing unit’s auxiliary braking power contribution to the vehicle combination occurred.

[0064] According to a third embodiment of the herein described method, the method comprises determining both the first SOC threshold and the second SOC threshold as described above. In general, the third embodiment comprises performing the method according to the first embodiment described above and thereafter performing the method according to the second embodiment described above, or vice versa. It should be noted that the predetermined first state of charge when initiating the method according to the first embodiment may be different from the predetermined first state of charge when initiating the method according to the second embodiment. Thus, the method according to the third embodiment may alternatively be described as comprising the following steps:

[0065] (a) when a reduction of the trailing unit’s motive power contribution to the vehicle combination is detected, estimating a total energy consumption and / or recovery of thetrailing unit since a point in time at which the trailing unit had a predetermined first state of charge,

[0066] (b) based on the predetermined first state of charge and the estimated total energy consumption and / or recovery derived from step (a), calculating a second state of charge of the trailing unit at which the reduction of the trailing unit’s motive power contribution to the vehicle combination occurred,

[0067] (c) based on the calculated second state of charge of the trailing unit as derived from step (b), determining a first state of charge threshold for the trailing unit at which the trailing unit’s deliverable motive power is limited,

[0068] (d) when a reduction of the trailing unit’s auxiliary braking power contribution to the vehicle combination is detected, estimating a total energy consumption and / or recovery of the trailing unit since a point in time at which the trailing unit had a predetermined third state of charge (wherein said predetermined third state of charge may be the same or different from the predetermined first state of charge),

[0069] (e) based on the predetermined third state of charge and the estimated total energy consumption and / or recovery derived from step (d), calculating a fourth state of charge of the trailing unit at which the reduction of the trailing unit’s auxiliary braking power contribution to the vehicle combination occurred,

[0070] (f) based on the calculated fourth state of charge of the trailing unit as derived from step (e), determining a second state of charge threshold for the trailing unit at which the trailing unit’s deliverable auxiliary braking power is limited.

[0071] Regardless of the embodiment of the herein described method, the step of determining the (first and / or second) state of charge threshold at which the trailing unit’s deliverable power is limited may be performed when it is assessed that the calculated second (or fourth) state of charge was a reason for the reduction of the trailing unit’s power contribution to the vehicle combination. Similarly, the method may comprise analyzing the trailing unit’s power contribution to the vehicle combination to thereby determine characteristics of the limitation of the trailing unit’s deliverable power both when the first SOC threshold is passed as well as when the second SOC threshold is passed.

[0072] The method may further comprise a step of communicating the determined state of charge threshold for the trailing unit at which the trailing unit’s deliverable power is limited to e.g. a server system (such as a cloud based server system and / or a fleet management system) for storage in a database. This may allow other towing units, to which the electrically poweredtrailing unit may be connected later on, to gain knowledge of the determined state of charge threshold for the electrically powered trailing unit.

[0073] The performance of the herein described method for determining at least one operational characteristic of an electrically powered trailing unit of a vehicle combination may be governed by programmed instructions. These programmed instructions may take the form of a computer program which, when executed by a computer, cause the computer to effect desired forms of control action. Such a computer may for example be comprised in the control arrangement as described herein. A computer is in the present disclosure considered to mean any hardware or hardware / firmware device implemented using processing circuity such as, but not limited to, a processor, Central Processing Unit (CPU), a controller, an arithmetic logic unit (ALU), a digital signal processor, a microcomputer, a field programmable gate array (FPGA), a System-on-Chip (SoC), a programmable logic unit, a microprocessor, an application-specific integrated circuit, or any other device capable of electronically performing operations in a defined manner.

[0074] The above described programmed instructions, which may take the form of a computer program, may be stored on a computer-readable medium. Hence, the present disclosure also relates to a computer-readable medium storing instructions, which when executed by a computer, cause the computer to carry out the herein described method for determining at least one operational characteristic of an electrically powered trailing unit of a vehicle combination. The computer-readable medium may be a non-transitory computer-readable medium, such as a tangible electronic, magnetic, optical, infrared, electromagnetic, and / or semiconductor system, apparatus, and / or device.

[0075] The present disclosure further relates to a control arrangement configured to determine at least one operational characteristic of an electrically powered trailing unit of a vehicle combination when the control arrangement is comprised in a towing unit of said vehicle combination. The control arrangement may be configured to perform any one of the steps of the method for determining at least one operational characteristic of an electrically powered trailing unit of a vehicle combination as described above.

[0076] More specifically, the present disclosure relates to a control arrangement configured to, when comprised in a towing unit of a vehicle combination, determine at least one operational characteristic of an electrically powered trailing unit of the vehicle combination. The control arrangement is configured to, when a reduction of the trailing unit’s power contribution to thevehicle combination is detected, estimate a total energy consumption and / or recovery of the trailing unit since a point in time at which the trailing unit had a predetermined first state of charge. The control arrangement is further configured to, based on the predetermined first state of charge and the estimated total energy consumption and / or recovery of the trailing unit, calculate a second state of charge of the trailing unit at which the reduction of the trailing unit’s power contribution to the vehicle combination occurred. Moreover, the control arrangement is configured to, based on the calculated second state of charge of the trailing unit, determine a state of charge threshold for the trailing unit at which the trailing unit’s deliverable power is limited.

[0077] The control arrangement may comprise one or more control units. In case of the control arrangement comprising a plurality of control units, each control unit may be configured to perform a certain action / step or a certain action / step may be divided between more than one control units. The control arrangement may be a control arrangement of a vehicle unit configured to act as a towing unit when said vehicle unit is comprised in a vehicle combination comprising a plurality of vehicle units. The control arrangement may for example be a control arrangement of a tractor truck, but is not limited thereto.

[0078] The control arrangement may be configured to communicate with one or more other control arrangements or control systems, for the purpose of performing parts of the herein described method. For example, the control arrangement may be configured to communicate with said one or more other control arrangements / control systems for the purpose of retrieving information utilized when performing the herein described method. More specifically, the herein described control arrangement may be configured to communicate with at least one of a user interface (for example a route planning interface or the like, or any other user interface allowing a driver to input certain forms of information to be retrievable by a control arrangement of a towing unit), a charger interface, a fleet management system, and a cloud service system for the purpose of determining the first state of charge of the trailing unit. Moreover, the control arrangement may be configured to communicate with e.g. a cloud service system for the purpose of determining, or utilizing, a predetermined model for the trailing unit which may be used when estimating total energy consumption and / or recovery during driving since a certain point in time (here the point in time at which the electrically powered trailing unit had the predetermined first state of charge).The control arrangement may further be configured to monitor the trailing unit’s power contribution to the vehicle combination, e.g. through monitoring of a difference between expected and actual power utilization of the towing unit. Thus, the control arrangement may also be configured to determine an expected power utilization of the towing unit as well as an actual power utilization of the towing unit.

[0079] Figure 1 schematically illustrates an example of a vehicle combination 1 comprising a towing unit 2 and an electrically powered trailing unit 3. In the illustrated example, the electrically powered trailing unit 3 is directly connected to the towing unit 2, i.e. without any intermediate vehicle unit present between the towing unit 2 and the electrically powered trailing unit 3. It should however be noted that the vehicle combination 1 may alternatively comprise one or more intermediate vehicle units arranged between the towing unit and the electrically powered trailing unit 3 without departing from the scope of the present disclosure. Additionally, or alternatively, the vehicle combination 1 may comprise one or more additional trailing units arranged after the electrically powered trailing unit 3 as seen in a primary direction of travel of said vehicle combination. Said primary direction of travel is in the figure illustrated by the arrow F.

[0080] The towing unit 2 of the vehicle combination 1 comprises a first powertrain 20. The first powertrain 20 comprises a first power unit 22, and optionally a second power unit 23. The first power unit 22 may for example be a combustion engine or an electric motor. The optional second power unit 23 may for example be an electric motor. The towing unit 2 may further comprise an energy storage device 21 configured to power the power unit(s) in case of said power unit(s) constituting electrical motor(s). The first power unit 22 and the optional second power unit 23 are configured to provide motive torque, via a first driveline 24, to drive wheels 4 of the towing unit 2, and thereby provide motive power to the towing unit 2 (and hence also to the vehicle combination 1 as such). The first power unit 22 and / or the optional second power unit 23 may further be configured to provide braking torque to the drive wheels 4 for the purpose of auxiliary braking of the towing unit 2. The first driveline 24 comprises a first transmission arrangement 26 connected to, optionally via a first differential 27, a first drive shaft 28. The first drive shaft 28 is in turn connected to the drive wheels 4 of the towing unit 2. The first power unit 22, the optional second power unit 23, the driveline 24 and the drive wheels 4 are all constituent parts of the first powertrain 20.The towing unit 2 further comprises a control arrangement 100. The control arrangement 100 may be configured to perform the herein described method for determining at least one operational characteristic of an electrically powered trailing unit of a vehicle combination comprisingthe towing unit. In otherwords, the control arrangement 100 may be configured to perform a method for determining at least one operational characteristic of the electrically powered trailing unit 3 of the vehicle combination 1. The control arrangement 100 may further be configured to control the towing unit 2. For example, the control arrangement 100 may be configured to control the first powertrain 20.

[0081] The trailing unit of the exemplified vehicle combination 1 is an electrically powered trailing unit 3 and comprises a second powertrain 30. The second powertrain 30 comprises a third power unit 32 configured to provide torque to a plurality of drive wheels 6 of the trailing unit 3 via a second driveline 34. Thereby, the second powertrain 30 may provide motive power to the trailing unit 3 and thus also to the vehicle combination 1 as such. The third power unit 32 is embodied as an electric motor, which in turn is powered by a second energy storage device 31. The second driveline 34 may, as shown in the figure, comprise a second transmission arrangement 36 connected to, optionally via a second differential 37, a second drive shaft 38. The second drive shaft 38 is in turn connected to the drive wheels 6 of the electrically powered trailing unit 3. The second transmission arrangement 36 may be a single speed transmission arrangement or a multi-speed transmission arrangement. The second powertrain 30 may for example be a drive unit in the form of an electric axle, also known as an e-axle, but is not limited thereto. The electrically powered trailing unit 3 may further comprise a controller 300 configured to control the second powertrain 30. The controller 300 may be configured to control the second powertrain 30 in accordance with its own control strategies, and may be non-integrated with the control arrangement 100 of the towing unit.

[0082] Figure 2 represents a flowchart schematically illustrating an exemplifying embodiment of the herein described method, performed by a control arrangement of a towing unit (such as the control arrangement 100 shown in Figure 1), for determining at least one operational characteristic of an electrically powered trailing unit of a vehicle combination comprising the towing unit. In the flowchart, optional steps of the exemplifying embodiment are shown with dashed lines.

[0083] The method according to the exemplifying embodiment comprises a step S101 of monitoring the trailing unit’s power contribution to the vehicle combination. The monitoring of the trailing unit’spower contribution to the vehicle combination may for example be made through monitoring of a difference between an expected power utilization of the towing unit and an actual power utilization of the towing unit. It should here be noted that step S101 may be continued to be performed in parallel with the subsequent steps of the method. In other words, step S101 need not be ended or completed as the method proceeds to subsequent steps.

[0084] The method further comprises a step S102 of, based on the monitoring in step S101 , determining whether an unforeseen reduction of the trailing unit’s power contribution to the vehicle combination may be detected. If no such reduction of the trailing unit’s power contribution is detected, the method may revert to start.

[0085] The method comprises a step S103 of, when an unforeseen reduction of the trailing unit’s power contribution to the vehicle combination is detected (as determined in step S102), estimating a total energy consumption and / or recovery of the trailing unit since a point in time at which the trailing unit had a predetermined first state of charge.

[0086] The method further comprises a step S104 of calculating a second state of charge of the trailing unit at which the reduction of the trailing unit’s power contribution to the vehicle combination occurred. Said calculation of the second state of charge is made based on the predetermined first state of charge and the estimated total energy consumption and / or recovery of the trailing unit as obtained in step S103.

[0087] The method may optionally comprise a step S105 of iterating the steps S101 to S104, thereby obtaining a plurality of calculated values of the second state of charge. The steps S101 to S104 could for example be reiterated a preselected number of times, to thereby obtain a preselected number of values of the second state of charge. Alternatively, the steps S101 to S104 may be reiterated until a preselected number of values, which are deemed to be consistent with each other, of the calculated second state of charge are obtained.

[0088] The method may further comprise a step S106 of assessing whether the calculated second state of charge was a reason for the detected reduction of the trailing unit’s power contribution to the vehicle combination. Said assessment may for example be made based on whether the calculated second state of charge falls within a predefined state of charge range. Alternatively, or additionally, the assessment may be made based on whetherthe calculated second state of charge is deemed to be consistent with previously determined values of the second state ofcharge for the trailing unit, said previously determined values of the second state of charge being derived through the reiteration according to the optional step S105.

[0089] In case the method comprises the optional step S106, the method is reverted to start in case it is assessed that the calculated second state of charge (obtained in step S104) was not a reason for the detected reduction (determined in step S102) of the trailing unit’s power contribution to the vehicle combination. Otherwise, the method proceeds to the subsequent step S107.

[0090] Step S107 comprises, based on the calculated second state of charge of the trailing unit (as obtained in step S104), determining a state of charge threshold for the trailing unit at which the trailing unit’s deliverable power is limited. According to one option, step S107 may comprise determining the state of charge at which the trailing unit’s deliverable power is limited to correspond to the calculated second state of charge. In case the method comprises the step S105 of reiterating steps S101 to S104, step S107 may for example comprise determining the state of charge threshold at which the trailing unit’s deliverable power is limited based on the plurality of values of the calculated second state of charge obtained through the reiteration.

[0091] The method may optionally further comprise a step S108 of analyzing the trailing unit’s power contribution to the vehicle combination to thereby determine characteristics of the limitation of the trailing unit’s deliverable power when the determined state of charge threshold (determined in step S107) is passed. For this purpose, the result of the monitoring according to step S101 may be utilized.

[0092] The method may thereafter be ended, as shown in the figure. Alternatively, the method may be reverted to start.

[0093] Figure 3 schematically illustrates an exemplifying embodiment of a device 500. The control arrangement 100 described above may for example comprise the device 500, consist of the device 500, or be comprised in the device 500.

[0094] The device 500 comprises a non-volatile memory 520, a data processing unit 510 and a read / write memory 550. The non-volatile memory 520 has a first memory element 530 in which a computer program, e.g. an operating system, is stored for controlling the function of the device 500. The device 500 further comprises a bus controller, a serial communication port, I / O means, an A / D converter, a time and date input and transfer unit, an event counter and aninterruption controller (not depicted). The non-volatile memory 520 has also a second memory element 540.

[0095] There is provided a computer program P that comprises instructions for a control arrangement of a towing unit to determine at least one operational characteristic of an electrically powered trailing unit of a vehicle combination comprising said towing unit. The computer program comprises instructions for, when a reduction of the trailing unit’s power contribution to the vehicle combination is detected, estimating a total energy consumption and / or recovery of the trailing unit since a point in time at which the trailing unit had a predetermined first state of charge. The computer program further comprises instructions for, based on the predetermined first state of charge and the estimated total energy consumption and / or recovery of the trailing unit, calculating a second state of charge of the trailing unit at which the reduction of the trailing unit’s power contribution to the vehicle combination occurred. The computer program also comprises instructions for, based on the calculated second state of charge of the trailing unit, determining a state of charge threshold for the trailing unit at which the trailing unit’s deliverable power is limited.

[0096] The computer program P may be stored in an executable form or in a compressed form in a memory 560 and / or in a read / write memory 550.

[0097] The data processing unit 510 may perform one or more functions, i.e. the data processing unit 510 may effect a certain part of the program P stored in the memory 560 or a certain part of the program P stored in the read / write memory 550.

[0098] The data processing device 510 can communicate with a data port 599 via a data bus 515. The non-volatile memory 520 is intended for communication with the data processing unit 510 via a data bus 512. The separate memory 560 is intended to communicate with the data processing unit 510 via a data bus 511. The read / write memory 550 is adapted to communicate with the data processing unit 510 via a data bus 514. The communication between the constituent components may be implemented by a communication link. A communication link may be a physical connection such as an optoelectronic communication line, or a non-physical connection such as a wireless connection, e.g. a radio link or microwave link.When data are received on the data port 599, they may be stored temporarily in the second memory element 540. When input data received have been temporarily stored, the data processing unit 510 is prepared to effect code execution as described above.

[0099] Parts of the methods herein described may be effected by the device 500 by means of the data processing unit 510 which runs the program stored in the memory 560 or the read / write memory 550. When the device 500 runs the program, methods herein described are executed.

[0100] Figure 4 illustrates a side view of an example of a vehicle in the form of a heavy-duty vehicle combination, which for example may correspond to the vehicle combination 1 shown in Figure 1. The vehicle combination 1 is here illustrated as a semi-trailer truck, and thus constitutes an example of a vehicle comprising two vehicle units. The primary direction of travel for the vehicle combination 1 is in the figure illustrated by the arrow F. More specifically, the exemplified vehicle combination 1 comprises a towing unit 2 in the form of a tractor truck, and an electrically powered trailing unit 3 in the form of an electrically powered semi-trailer. The towing unit 2 comprises drive wheels 4 configured to be driven by a powertrain of the towing unit 2 (compare with first powertrain 20 of Figure 1). The drive wheels 4 are equally distributed on both sides of the towing unit, and thus only one of the drive wheels 4 is visible in the figure. The towing unit 2 further comprises front wheels 5, which may typically be non-driven wheels, but could alternatively be drive wheels. The electrically powered trailing unit 3 comprises its own powertrain (compare with second powertrain 30 of Figure 1) configured to provide motive power to at least one set of drive wheels 6. The drive wheels 6 are equally disposed on both sides of the electrically powered trailing unit 3, and thus only one of the drive wheels 6 is visible in the figure.

Claims

1. CLAIMS1. A method, performed by a control arrangement (100) of a towing unit (2), for determining at least one operational characteristic of an electrically powered trailing unit (3) of a vehicle combination (1) comprising the towing unit (2),the method comprising the following steps:when a reduction of the trailing unit’s power contribution to the vehicle combination (1) is detected, estimating (S103) a total energy consumption and / or recovery of the trailing unit (3) since a point in time at which the trailing unit (3) had a predetermined first state of charge,based on the predetermined first state of charge and the estimated total energy consumption and / or recovery of the trailing unit (3), calculating (S104) a second state of charge of the trailing unit (3) at which the reduction of the trailing unit’s power contribution to the vehicle combination (1) occurred, andbased on the calculated second state of charge of the trailing unit (3), determining (S107) a state of charge threshold for the trailing unit (3) at which the trailing unit’s deliverable power is limited.

2. The method according to claim 1 , further comprising a step of:monitoring (S101) of the trailing unit’s power contribution to the vehicle combination (1) through monitoring of a difference between expected and actual power utilization of the towing unit (2).

3. The method according to anyone of claims 1 or 2, wherein the step of determining the state of charge threshold at which the trailing unit’s deliverable power is limited is performed when it is assessed that the calculated second state of charge was a reason for the reduction of the trailing unit’s power contribution to the vehicle combination (1).

4. The method according to claim 3, further comprising a step of:assessing (S106) whether the calculated second state of charge was the reason for the detected limitation of the trailing unit’s power contribution to the vehicle combination (1) based on whetherthe calculated second state of charge falls within a predefined state of charge range and / or whether the calculated second state of charge is deemed to be consistent with previously determined values of the second state of charge for the trailing unit (3).

5. The method according to any one of the preceding claims, wherein the step of estimating (S103) total energy consumption and / or recovery of the trailing unit (3) since the point in time at which the trailing unit (3) had the predetermined first state of charge is performed based on a predetermined model for the trailing unit (3).

6. The method according to any one of the preceding claims, further comprising a step of:analyzing (S108) the trailing unit’s power contribution to the vehicle combination (1) to thereby determine characteristics of the limitation of the trailing unit’s deliverable power when the determined state of charge threshold is passed.

7. A control arrangement (100) configured to, when comprised in a towing unit (2) of a vehicle combination (1), determine at least one operational characteristic of an electrically powered trailing unit (3) of the vehicle combination (1),the control arrangement (100) being configured to:when a reduction of the trailing unit’s power contribution to the vehicle combination (1) is detected, estimate a total energy consumption and / or recovery of the trailing unit (3) since a point in time at which the trailing unit (3) had a predetermined first state of charge,based on the predetermined first state of charge and the estimated total energy consumption and / or recovery of the trailing unit (3), calculate a second state of charge of the trailing unit (3) at which the reduction of the trailing unit’s power contribution to the vehicle combination (1) occurred, andbased on the calculated second state of charge of the trailing unit (3), determine a state of charge threshold for the trailing unit (3) at which the trailing unit’s deliverable power is limited.

8. The control arrangement (100) according to claim 7, wherein the control arrangement (100) further is configured to monitor the trailing unit’s power contribution to the vehicle combination (1 ) through monitoring of a difference between expected and actual power utilization of the towing unit (2).

9. The control arrangement (100) according to any one of claims 7 or 8, wherein the control arrangement (100) is configured to determine the state of charge threshold for the trailing unit (3) at which the trailing unit’s deliverable power is limited when it is assessedthat the calculated second state of charge was a reason for the reduction of the trailing unit’s power contribution to the vehicle combination (1 ).

10. The control arrangement (100) according to claim 9, wherein the control arrangement (100) further is configured to assess that the calculated second state of charge was the reason for the detected limitation of the trailing unit’s power contribution to the vehicle combination (1 ) when the calculated second state of charge falls within a predefined state of charge range and / or when the calculated second state of charge is deemed to be consistent with previously determined values of the second state of charge for the trailing unit (3).

11. The control arrangement (100) according to any one of claims 7 to 10, wherein the control arrangement (100) is configured to estimate total energy consumption and / or recovery of the trailing unit (3) since the point in time at which the trailing unit (3) had the predetermined first state of charge based on a predetermined model for the trailing unit (3).

12. The control arrangement (100) according to any one of claims 7 to 11 , wherein the control arrangement (100) further is configured to analyze the trailing unit’s power contribution to the vehicle combination (1) to thereby determine characteristics of the limitation of the trailing unit’s deliverable power when the determined state of charge threshold is passed.

13. The control arrangement (100) according to any one of claims 7 to 12, further configured to communicate with at least one of a user interface, a charger interface, a fleet management system, and a cloud service system for the purpose of determining the first state of charge of the trailing unit (3).

14. A computer program comprising instructions which, when executed by a control arrangement (100) according to any one of claims 7 to 13, cause the control arrangement (100) to perform the method according to any one of claims 1 to 6.

15. A computer-readable medium having stored thereon the computer program according to claim 14.

16. A vehicle unit configured to, when comprised in a vehicle combination (1), act as a towing unit (2), the vehicle unit comprising a control arrangement (100) according to any one of claims 7 to 13.

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