Method and control device for controlling regenerative braking in a vehicle

Abstract

A control device (100) and a method (200, 220) for controlling a vehicle (1) are provided. The vehicle comprises an energy storage device (3), an electric motor (2) and at least one service brake (10) configured to brake a vehicle wheel (7, 8). The method (200, 220) comprises the step of applying a braking force by activating the service brake (10) if it is predicted that the energy storage device (3) will not have sufficient capacity for a required regenerative braking power during an upcoming braking event. The service brake (10) is activated while the electric motor (2) applies a propulsion force or in a plurality of consecutive braking phases (20) in which the propulsion force of the electric motor (2) is temporarily interrupted, the braking phases (20) being separated by vehicle 10 acceleration phases (22) during which a propulsion force is applied by the electric motor (2).

Description

TECHNICAL FIELD

[0001] The present disclosure generally relates to a method for controlling a vehicle. The present disclosure generally also relates to a control device configured to control a vehicle. The present disclosure generally also relates to a computer program and a computer readable medium. The present disclosure generally also relates to a vehicle. BACKGROUND

[0002] Regenerative braking of a vehicle is an effective tool for controlling the speed of a vehicle, such as a heavy land vehicle. It is also beneficial in that it allows for the recovery of energy, which can subsequently be used for propulsion of the vehicle. More specifically, during regenerative braking, the electric motor of the vehicle operates as a generator, whereby the kinetic energy of the vehicle is converted into electrical energy for charging the energy storage device of the vehicle. The recovered energy can subsequently be used for propulsion of the vehicle by the electric motor powered by the energy storage device.

[0003] However, the ability to use regenerative braking is limited by the storage capacity of the energy storage device. The storage capacity is typically given by a predetermined maximum threshold. During a braking event, the energy storage device can be charged to the predetermined maximum threshold and no additional energy can be accepted without the risk of overcharging and damaging the energy storage device. Therefore, when the capacity of the energy storage device is at or above the predetermined maximum threshold, regenerative braking cannot be used to control the speed of the vehicle during a braking event.

[0004] In case the capacity of the energy storage device at the start of a regenerative braking event is insufficient to provide the required regenerative braking power for the braking event, it can be necessary to use other braking systems of the vehicle during the braking event. Examples of such other braking systems can include service brakes configured to brake the wheels of the vehicle, or auxiliary braking systems, such as retarders or engine brakes (in case of a hybrid vehicle). Using service brakes during a braking event, especially during prolonged braking events, can for example lead to an increased wear and / or overheating of the service brakes. This in turn can pose a safety risk. SUMMARY

[0005] It is an object of the present invention to enable a more efficient use of regenerative braking.

[0006] This object is achieved by the subject matter of the appended independent claims.

[0007] According to the present disclosure, a method for controlling a vehicle is provided. The method is performed by a control device. The vehicle comprises an energy storage device chargeable by regenerative braking of the vehicle, a propulsion unit in the form of an electric motor powered by the energy storage device, and at least one service brake configured to brake a wheel of the vehicle. The method comprises the steps of: if it is predicted that the energy storage device will not have sufficient capacity for a required regenerative braking power during an identified upcoming braking event, applying a braking force by activating the service brake, wherein the service brake is activated while the electric motor applies a propulsion force, or in a plurality of consecutive braking phases in which the propulsion force of the electric motor is temporarily interrupted, said braking phases being separated by vehicle acceleration phases during which a propulsion force is applied by the electric motor.

[0008] By the present method, a more efficient use of regenerative braking during a braking event can be achieved. This is due to that the energy storage device is effectively discharged prior to the braking event if it is predicted that the state of charge of the energy storage device will be too high at the start of the braking event to allow for the required regenerative braking power. By the present method, the discharge of the energy storage is achieved by applying a braking force that is at least partly compensated for by the electric motor. This in turn results in that the electric motor needs more energy compared to if the vehicle simply continues to be driven in a normal electric (or, as applicable, hybrid) driving mode. This results in an increased discharge of the energy storage device, which means that the state of charge of the energy storage device will be lower when the vehicle reaches the start of the braking event compared to if the vehicle continues to be driven in an electric (or, if applicable, hybrid) driving mode. Thus, the ability to utilize regenerative braking during the braking event is improved.

[0009] The method can comprise the step of predicting whether the energy storage device will have sufficient capacity for a required regenerative braking power during the identified upcoming braking event based on an estimated state of charge of the energy storage device at the start of the upcoming braking event and an estimated charge generated by regenerative braking during the identified upcoming braking event. Thus, the accuracy of predicting whether the energy storage device will have sufficient capacity to allow for a required regenerative braking power during an upcoming braking event can be improved. This in turn further improves the control of the vehicle and thereby further improves the likelihood of efficiently using regenerative braking during an upcoming braking event.

[0010] The step of applying a braking force by activating the service brake can be performed so as to keep the vehicle speed within a preselected speed interval. Thereby, the energy storage device can be effectively discharged without any risk of causing any confusion and / or discomfort to a driver of the vehicle. Furthermore, this can further facilitate the discharge of the energy storage device since the speed reduction caused by applying the braking force by activating the service brake is compensated for by means of the propulsion force applied by the electric motor.

[0011] The method can further comprise the step of predicting a required discharge amount of the energy storage device to be achieved before the time point of the start of the identified upcoming braking event, to allow for a required regenerative braking power during the braking event. This has in particular the advantage that it enables a more accurate determination of the amount of braking force to be applied by the service brakes, and when the braking force should be applied, which in turn improves the control of the vehicle. Thereby, the risk of an excessively high usage of the service brakes can be reduced, which in turn reduces the wear of the service brakes and further reduces the risk of overheating of the service brakes.

[0012] The method can further comprise predicting a first time point at which a braking force should be applied by means of the service brakes; and activating the service brakes at the first time point. This in turn further improves the control of the vehicle, as it enables the application of the braking force to be performed at an appropriate time point to allow for the required amount of discharge of the energy storage device, while not adversely affecting the operation of the vehicle.

[0013] The method can further comprise predicting a second time point at which the application of the braking force by means of the activation of the service brakes should be terminated, to allow for the service brakes to have a required temperature at the start of the braking event; and terminating the step of applying the braking force by means of the activation of the service brakes at the second time point, if the service brakes have not already been deactivated. This has the advantage that it enables sufficient time for the temperature of the service brakes to be reduced (which can increase during the application of the braking force), so that it can be ensured that the service brakes have a suitable temperature at the start of the braking event.

[0014] Although it can not be intended to use the service brakes during the braking event, these should still be prepared for use in case the vehicle unexpectedly needs to brake with a higher braking power during the braking event. Furthermore, in certain situations, the service brakes can need to be used during the braking event if the available regenerative braking power is not sufficient for the entire braking event.

[0015] The method can further comprise controlling the braking force applied by means of the service brakes to meet the predicted required discharge amount of the energy storage device to be achieved before the time point of the start of the identified upcoming braking event. Thereby, the risk of unnecessarily using the service brakes can be minimised. Furthermore, the risk of the energy storage device discharging more than intended or necessary can be minimised. Furthermore, this has the advantage of achieving a sufficient discharge of the energy storage device before the time point of the start of the braking event, and thus increases the likelihood of efficiently using regenerative braking during the braking event.

[0016] The method can further comprise deactivating the service brake in response to determining that the energy storage device has reached a required state of charge and / or that the temperature of the service brake has reached a predetermined threshold temperature. Thus, it can be ensured that the application of braking force by use of the service brake is interrupted before the energy storage device reaches too low a state of charge or the temperature of the service brake becomes too high. In other words, this increases the safety of the vehicle control and reduces the risk of permanent damage to its constituent parts.

[0017] The method can further comprise controlling the temperature of the energy storage device to increase the regenerative braking power available during the braking event. Thus, the possibility of utilizing regenerative braking during the braking event can be further improved.

[0018] Furthermore, the present disclosure provides a computer program comprising instructions which, when executed by a control device, cause the control device to perform the method as described above.

[0019] The present disclosure also provides a computer readable medium comprising instructions which, when executed by a control device, cause the control device to perform the method as described above.

[0020] Furthermore, according to the present disclosure, a control device configured to control a vehicle is provided. The vehicle comprises an energy storage device chargeable by regenerative braking of the vehicle, a propulsion unit in the form of an electric motor powered by the energy storage device, and at least one service brake configured to brake a wheel of the vehicle. The control device is configured to, if it is predicted that the energy storage device will not have sufficient capacity for a required regenerative braking power during an identified upcoming braking event, (i) apply a braking force by activating the service brake while the electric motor applies a propulsion force, or (ii) apply a braking force by activating the service brake in a plurality of consecutive braking phases in which the propulsion force of the electric motor is temporarily interrupted, the braking phases being separated by vehicle acceleration phases during which the propulsion force is applied by the electric motor.

[0021] The control device has the same advantages as described above in relation to the corresponding method for controlling a vehicle.

[0022] The control device can be further configured to predict a required discharge amount of the energy storage device to be achieved before a time point at which the identified upcoming braking event starts, to allow for the required regenerative braking power during the braking event.

[0023] Further, the control device can be configured to: predict a first point in time at which a braking force should be applied by means of the service brakes; and to activate the service brakes at said first point in time. Alternatively or additionally, the control device can be configured to: predict a second point in time at which the application of the braking force by means of the activation of the service brakes should be terminated to allow the service brakes to have a required temperature at the start of the braking event; and to terminate the application of the braking force by means of the activation of the service brakes at said second point in time if the service brakes have not already been deactivated.

[0024] The control device can further be configured to deactivate said at least one service brake in response to determining that the energy storage device has reached a required state of charge and / or that the temperature of the service brakes has reached a predetermined threshold temperature.

[0025] The present disclosure also provides a vehicle comprising a control device as described above. The vehicle can be a heavy duty vehicle, such as a bus or a truck. Further, the vehicle can be a hybrid vehicle or a fully electric vehicle. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 a side view of a vehicle is schematically illustrated,

[0027] Figure 2 a situation in which the vehicle is approaching a downhill section of a road is schematically illustrated, and a braking event associated with the downhill section is identified,

[0028] Figure 3 a flow chart schematically illustrating a first exemplary embodiment of a method for controlling a vehicle according to the present disclosure,

[0029] Figure 4 a flow chart schematically illustrating a second exemplary embodiment of a method for controlling a vehicle according to the present disclosure,

[0030] Figures 5a-5c different alternatives of applying a braking force by means of activating one or more service brakes according to the present disclosure,

[0031] Figure 6 a device according to the present disclosure which can constitute, comprise or be part of a control device configured to control a vehicle is schematically illustrated. DETAILED DESCRIPTION

[0032] The present application will be described below in greater detail, with reference to exemplary embodiments and accompanying drawings. The present application is not limited to the exemplary embodiments discussed and / or illustrated in the accompanying drawings, but can vary within the scope of the appended claims. Moreover, the accompanying drawings should not be considered to be drawn to scale as some features can be exaggerated in order to more clearly illustrate the present application or features thereof.

[0033] According to the present disclosure, a method for controlling a vehicle is provided. More specifically, the present disclosure provides a method for controlling a vehicle approaching an upcoming braking event during which it can be desirable to brake the vehicle (at least during a part of the braking event and / or at least partially) by regenerative braking. The vehicle comprises an energy storage device chargeable by regenerative braking of the vehicle. The vehicle further comprises a first propulsion unit in the form of an electric motor powered by the energy storage device. If desired, the vehicle can comprise a further propulsion unit, e.g. a second electric motor and / or a combustion engine. Regenerative braking of the vehicle can be performed by operating the first propulsion unit or possibly the second electric motor of the vehicle as a generator, thereby charging the energy storage device. The vehicle also comprises at least one service brake configured to brake a driven wheel or a non-driven wheel of the vehicle. Preferably, the vehicle comprises a plurality of service brakes. Any (driven or non-driven) wheel of the vehicle can be provided with a respective service brake.

[0034] The method for controlling a vehicle according to the present disclosure comprises the step of applying a braking force by enabling the service brake if it is predicted that the energy storage device will not have sufficient capacity for the required regenerative braking power during the identified upcoming braking event. According to a first alternative, the service brake is enabled while the electric motor applies a vehicle propulsion force. In other words, the braking force (achieved by enabling the service brake) is applied while the vehicle propulsion force of the electric motor is applied to the vehicle. According to this first alternative, the service brake can be enabled, for example, during a single braking phase or in a plurality of consecutive braking phases, wherein the vehicle propulsion force is applied simultaneously over the total duration of at least two consecutive braking phases (suitably substantially the entire duration of the plurality of braking phases). According to a second alternative, the service brake is enabled in a plurality of consecutive braking phases in which the vehicle propulsion force of the electric motor is temporarily interrupted, and wherein two consecutive braking phases are separated by a vehicle acceleration phase during which the vehicle propulsion force is applied by the electric motor. In other words, a plurality of vehicle braking phases are applied alternately with a plurality of vehicle acceleration phases.

[0035] The method results in discharging the energy storage device due to the electric motor at least partially compensating for the applied braking force, regardless of which of the two alternatives how the braking force is applied. The first alternative how the braking force is applied has the advantage that the energy storage device can be discharged more quickly compared to the second alternative. However, for certain vehicle configurations and / or vehicle masses, the first alternative can not be suitable, in which case the second alternative is more suitable.

[0036] As mentioned above, the method comprises the step of applying a braking force by enabling the service brakes if the energy storage device is predicted not to have sufficient capacity for the required regenerative braking power during the identified upcoming braking event. If the vehicle comprises a plurality of service brakes (as is generally the case), the step of applying a braking force can comprise enabling one or more service brakes. The application of the braking force can be achieved by enabling at least two service brakes for reasons of vehicle stability and / or the required braking power to be achieved. The step can comprise applying a braking force by enabling any combination of the service brakes, including all service brakes.

[0037] The step of applying a braking force by enabling the service brakes can be performed in response to the aforementioned prediction that the energy storage device will not have sufficient capacity for the required regenerative braking power during the identified upcoming braking event. In other words, the step can be initiated automatically if the energy storage device is predicted not to have sufficient capacity for the required regenerative braking power during the identified upcoming braking event. In this case, the method can be described as comprising the step of applying a braking force by enabling the service brakes in response to a prediction that the energy storage device will not have sufficient capacity for the required regenerative braking power during the identified upcoming braking event, wherein the service brakes are enabled while the electric motor applies a propulsion force, or are enabled in a plurality of consecutive braking phases in which the propulsion force of the electric motor is temporarily interrupted, the braking phases being separated by vehicle acceleration phases during which a propulsion force is applied by the electric motor.

[0038] Alternatively, if desired, the step of applying a braking force by activating the service brakes can be performed in response to a request by the driver to discharge the energy storage device prior to the upcoming braking event. In this case, the method can comprise the step of suggesting to the driver to initiate the request to discharge the energy storage device prior to the upcoming braking event in response to a prediction that the energy storage device will not have sufficient capacity for the required regenerative braking power during the identified upcoming braking event. The suggestion to the driver can be made in any manner previously known for suggesting actions to the driver of a vehicle, such as by displaying a message on a display of the vehicle and / or by sound. The suggestion to the driver can be performed, for example, by alerting the driver.

[0039] The method can further comprise the step of predicting whether the energy storage device will have sufficient capacity for the required regenerative braking power during the identified upcoming braking event based on an estimated state of charge of the energy storage device at the start of the upcoming braking event and an estimated charge generated by regenerative braking during the identified upcoming braking event. Thereby, a reliable prediction can be provided whether the energy storage device will not have sufficient capacity for the required regenerative braking power during the upcoming braking event and the energy storage device should therefore be discharged prior to the braking event. Thereby, the application of a braking force by activating the service brakes can be avoided unnecessarily.

[0040] The step of applying a braking force by activating one or more of the service brakes of the vehicle can be performed in order to keep the vehicle speed within a preselected speed interval. The preselected speed interval can for example comprise a preselected target vehicle speed with an associated acceptable margin, but is not limited thereto. Thereby, the application of the braking force can not pose a risk of causing confusion for the driver of the vehicle, desiring the vehicle to travel, for example, at a preselected cruising speed. Furthermore, by keeping the vehicle speed within the preselected speed interval, it can be ensured that the braking force applied by means of the one or more service brakes is effectively compensated by the propulsion force applied by the electric motor, such that the energy storage device is effectively discharged.

[0041] If desired, the method can further comprise the step of inhibiting activation (illumination) of a brake light of the vehicle when the one or more service brakes are activated. This can in particular be performed in case the step of applying a braking force is performed in order to keep the vehicle speed within a preselected speed interval. Typically, a brake light of a vehicle is automatically activated when the service brakes are activated. If the brake light of the vehicle is activated during the performance of the method described herein, other road users (in the vicinity of the vehicle) can become confused. For said reason, the method can comprise the step of inhibiting activation of the brake light when the service brakes are activated for the purpose of discharging the energy storage device.

[0042] The method can further comprise the step of predicting a required discharge amount of the energy storage device to be achieved before a time point of the start of the upcoming braking event, to allow for a required regenerative braking power during the braking event. Based on this prediction, it can be determined when to apply a braking force by activating one or more service brakes, to allow sufficient time for discharging the energy storage device. Thus, based on this, the method can comprise predicting a first time point at which a braking force should be applied by means of one or more service brakes; and activating the one or more service brakes at the first time point.

[0043] The method can further comprise the step of predicting a second time point at which the application of a braking force by means of the one or more service brakes should be terminated, to allow for the one or more service brakes to have a required temperature at the start of the braking event. Although it can not be intended to use the service brakes during the braking event, but to rely on regenerative braking, the service brakes should still be able to provide sufficient braking force at any time during the braking event, in case of an unexpected situation. For this reason, it can be important to ensure that the service brakes can have a suitable temperature at the start of the braking event, or at least shortly after the braking event. Furthermore, in some situations, depending on the gradient of the road and / or the duration of the braking event, it can also be possible to use the service brakes during the braking event to control the vehicle speed. Again for this reason, the service brakes should have a suitable temperature at the start of the braking event. The method can further comprise the step of terminating the step of applying a braking force at the second time point (whether this braking force is applied in a single braking phase or in a plurality of consecutive braking phases).

[0044] The method can further comprise the step of controlling the braking force applied by the one or more service brakes (before a braking event in which regenerative braking is intended) to meet the predicted required discharge amount of the energy storage device to be achieved before a time point of the start of the upcoming braking event. Such control can take into account the first time point at which a braking force should be applied and the second time point at which the application of a braking force should be terminated, as discussed above.

[0045] The method can comprise the step of deactivating the one or more service brakes in response to determining that the energy storage device has reached the required state of charge and / or that the temperature of the one or more service brakes has reached a predetermined threshold temperature, primarily for safety reasons. Thereby, the application of braking force is terminated. By terminating the application of braking force when the energy storage device has reached the required state of charge, it can be avoided that the energy storage device is discharged below a permissible minimum state of charge threshold, and it is ensured that the energy storage device can obtain a suitable state of charge for propelling the vehicle after the end of the braking event during regenerative braking. The predetermined threshold temperature may, for example, correspond to a maximum permissible temperature of the one or more service brakes.

[0046] The method can further comprise the step of actively controlling the temperature of the energy storage device to increase the regenerative braking power available during the braking event. Depending on the situation, such control can comprise increasing, maintaining or decreasing the temperature of the energy storage device. The control of the temperature of the energy storage device can be performed before and / or during the application of braking force by activating the one or more service brakes. By actively controlling the temperature of the energy storage device, for example, the discharge of the energy storage device can be increased prior to the braking event, thereby increasing the ability to use regenerative braking during the braking event.

[0047] The execution of the method for controlling a vehicle as described herein can be managed by programming instructions. These programming instructions typically take the form of a computer program which, when executed in or by a control device, causes the control device to implement the desired form of control action. Such instructions can typically be stored on a computer readable medium.

[0048] The present disclosure also relates to a control device configured to control a vehicle according to the method described above. The control device can be configured to perform any one of the steps of the method for controlling a vehicle as described herein.

[0049] More specifically, a control device configured to control a vehicle is provided. The vehicle comprises an energy storage device chargeable by regenerative braking of the vehicle, a propulsion unit in the form of an electric motor powered by the energy storage device, and at least one service brake configured to brake a wheel of the vehicle. The control device is configured to apply a braking force by activating the service brake if it is predicted that the energy storage device will not have sufficient capacity for a required regenerative braking power during an identified upcoming braking event. Said applying of the braking force by activating can be performed by the control device while the electric motor applies a propulsion force. Alternatively, said applying of the braking force by activating can be performed by activating the service brake in a plurality of consecutive braking phases in which the propulsion force by the electric motor is temporarily interrupted, wherein two consecutive braking phases are separated by a vehicle acceleration phase during which a propulsion force is applied by the electric motor.

[0050] The control device can further be configured to predict whether the energy storage device will have sufficient capacity for a required regenerative braking power during an identified upcoming braking event. Alternatively, the control device can be configured to communicate with a control system (of the vehicle, partially comprised in the vehicle, or arranged remote from the vehicle) configured to make the prediction of whether the energy storage device will have sufficient capacity for a required regenerative braking power during an identified upcoming braking event.

[0051] The control device can comprise one or more control units. In case the control device comprises a plurality of control units, each control unit can be configured to control a certain function, or a certain function can be divided between more than one control unit. The control device can be part of the vehicle itself. Alternatively, parts of the control device can be arranged remote from the vehicle, such as a remote control centre or similar.

[0052] Figure 1 A side view of an example of a vehicle 1 is schematically illustrated. The vehicle can be a fully electric vehicle or a hybrid vehicle. Further, the vehicle can be a heavy duty vehicle, such as a bus or a truck, but is not limited thereto. The vehicle 1 comprises a first propulsion unit in the form of an electric motor 2. The electric motor 2 is powered by an energy storage device 3 of the vehicle. If desired, the vehicle 1 can comprise a second propulsion unit, such as a combustion engine 5 and / or a second electric motor (not shown). The vehicle further comprises one or more service brakes 10 arranged at respective wheels of the vehicle, such as drive wheels 7 or non-drive wheels 8.

[0053] Preferably, each wheel of the vehicle 1 can be braked by a respective service brake 10.

[0054] The vehicle 1 can further comprise a gearbox 4 configured to selectively transmit propulsion torque from the propulsion unit to the drive wheels 7 of the vehicle. The gearbox 4 can be connected to the drive wheels 7 of the vehicle via a conventional propeller shaft 6. In this case, the vehicle powertrain can have a central drive configuration. However, it should be noted that the vehicle powertrain can alternatively have an electric axle configuration if desired.

[0055] In addition to being configured to supply power to the electric motor 2, the energy storage device 3 is configured to be charged by regenerative braking of the vehicle 1. This can be achieved, for example, by operating the electric motor 2 as a generator. Alternatively, the energy storage device 3 can be charged by operating a second electric motor (if present) as a generator during regenerative braking of the vehicle.

[0056] The vehicle 1 can further comprise a control device 100 configured to control the vehicle. In particular, the control device 100 can be configured to control the electric motor, the energy storage device and the service brakes. The control device 100 can also be configured to communicate with a remote control centre, control devices of other vehicles and / or control units of infrastructure for exchanging various forms of data via any previously known communication system, such as a V2X communication system. Examples of such data can include data for the positioning of the vehicle and / or map data (including terrain data), but are not limited thereto.

[0057] To illustrate one possible scenario and certain features of the method according to the present disclosure, Figure 2 a vehicle is schematically illustrated when approaching a downhill section of a road, for example Figure 1 the vehicle 1 shown in Fig. 1. At a time point t0, an upcoming braking event can be identified and it can be determined that the braking event is expected to start at a time t start_BE The braking event can for example occur during the downhill section, but can also start before the vehicle has actually reached the downhill section or after the vehicle has passed the start of the downhill section. The upcoming braking event can also be expected to end at a time point t end_BE When the upcoming braking event has been identified, it can be predicted that at t start_BEwhether the energy storage device will have sufficient capacity for the required regenerative braking power during the identified upcoming braking event. The required regenerative braking power can for example be a regenerative braking power for maintaining the vehicle speed within a predetermined speed interval during the braking event. Such a vehicle speed can be substantially the same as, higher than, or lower than the vehicle speed before the braking event. Alternatively or additionally, the required regenerative braking power can be a sufficient regenerative braking power such that use of further braking systems of the vehicle, such as an auxiliary braking system and / or service brakes, can be avoided during the braking event or during at least a part of the braking event.

[0058] If it is predicted that the energy storage device will not have sufficient capacity for the required regenerative braking power, i.e. if the state of charge of the energy storage device will be too high at t start_BE to allow for the required regenerative braking power, the method comprises applying a braking force by activating the service brakes at a first point in time tl. The application of the braking force by activating the service brakes can be terminated at a second point in time t2. The application of the braking force is initiated and terminated before the vehicle reaches the braking event. In other words, both tl and t2 are before the braking event starts, i.e. before t start_BE Furthermore, the application of the braking force by activating the service brakes is performed while the electric motor applies a vehicle propulsion force, or in a plurality of consecutive braking phases in which the propulsion force of the electric motor is temporarily interrupted, the braking phases being separated by vehicle acceleration phases during which a propulsion force is applied by the electric motor. Thereby, the energy storage device is effectively discharged before the vehicle reaches the braking event, since the braking force applied (by means of the service brakes) is compensated by the propulsion force applied by the electric motor which is powered by the energy storage device.

[0059] Figure 3 A flowchart representing a first exemplary embodiment 200 of a method for controlling a vehicle according to the present disclosure is shown schematically. In the flowchart, optional steps are shown by dashed lines and / or dashed boxes. The method can comprise any one of the optional steps independently of the other optional steps, as well as any combination of a plurality of optional steps. As previously mentioned, the vehicle comprises an energy storage device which is chargeable by regenerative braking of the vehicle, a propulsion unit in the form of an electric motor powered by the energy storage device, and at least one service brake configured to brake a wheel of the vehicle. If the vehicle comprises a plurality of service brakes, each service brake can be associated with a respective (driven or non-driven) wheel of the vehicle.

[0060] The method 200 can comprise a step S101 of identifying an upcoming braking event. Such identification can thus be made by any previously known method, for example by using knowledge of the geographical position of the vehicle in combination with map data and / or by using a look-ahead system.

[0061] The method can further comprise a step S102 of estimating the state of charge of the energy storage device at the start of the identified upcoming braking event. In other words, the method can comprise a step S102 of estimating the (future) state of charge of the energy storage device at a point in time at which regenerative braking for the braking event is estimated to start. Such estimation can be made by determining the current state of charge of the energy storage device and estimating the change in state of charge of the energy storage device from the current state of charge up to the point in time at which the braking event starts. The change in state of charge depends on the operation of the vehicle up to the point in time at which the braking event starts.

[0062] Hence, in estimating the change in state of charge of the energy storage device, the operating conditions of the vehicle can be taken into account. Furthermore, in estimating the change in state of charge, other factors can be taken into account, such as the vehicle mass, etc.

[0063] The method can further comprise a step S103 of estimating the charge generated by regenerative braking during the upcoming braking event. The estimation of the charge generated by regenerative braking during the braking event can take into account factors such as the vehicle speed (which can be substantially the same or vary during the braking event), the terrain, the duration of the braking event, the braking power (which can be substantially constant or vary during the braking event), the vehicle mass, etc. Furthermore, the estimation can also take into account the possible use of an auxiliary brake (if available) and the braking power achieved thereby.

[0064] The method 200 can generally comprise a step S104 of predicting whether the energy storage device will have sufficient capacity for the required regenerative braking power during the identified upcoming braking event. The required regenerative braking power can for example correspond to the regenerative braking power required to keep the vehicle speed within a preselected speed interval. This can for example be defined by a cruise control system, a downhill speed control system or similar. The prediction in step S104 can be based on the estimated state of charge at the start of the braking event as obtained in step S102 and the estimated charge generated by regenerative braking during the identified upcoming braking event as obtained in S103. If it is predicted that the energy storage device will have sufficient capacity for the required regenerative braking power during the identified upcoming braking event, the method can return to the start. However, if it is predicted that the energy storage device will not have sufficient capacity for the required regenerative braking power during the identified upcoming braking event, the method proceeds to a subsequent step.

[0065] The method 200 comprises a step S108 of applying a braking force by activating one or more service brakes of the vehicle, if it is predicted that the energy storage device will not have sufficient capacity for the required regenerative braking power during the identified upcoming braking event. The step S108 can be performed automatically in response to the prediction that the energy storage device will not have sufficient capacity for the required regenerative braking power during the identified upcoming braking event. According to one alternative, the braking force applied in step S108 is performed in a single braking phase, during which vehicle propulsion force is also applied by means of the electric motor (as compared to Figure 5a According to another alternative, the braking force applied in step S108 is performed by activating the service brakes in a plurality of consecutive braking phases, wherein propulsion force is applied simultaneously for the total duration of at least two consecutive braking phases (as compared to Figure 5b According to yet another alternative, the braking force applied in step S108 is performed by activating the service brakes in a plurality of consecutive braking phases in which the propulsion force of the electric motor is temporarily interrupted, said consecutive braking phases being separated by vehicle acceleration phases during which propulsion force is applied by the electric motor (as compared to Figure 5c

[0066] Prior to step S108, the method 200 can further comprise a step S105 of predicting a required discharge amount to be achieved prior to the time point of the start of the identified upcoming braking event, to allow for the required regenerative braking power during the braking event. This can be performed simultaneously with step S104.

[0067] The method 200 can further comprise a step S106 of predicting a first time point at which braking force should be applied by means of the one or more service brakes. In other words, in step S106 it can be predicted when to initiate step S108.

[0068] The method 200 can further comprise a step S107 of predicting a second time point at which the application of braking force by activating the service brakes should be terminated, to allow for the service brakes to have a required temperature at the start of the braking event. The reason for this is thus to allow the service brakes to have sufficient time to cool down to a suitable temperature to allow for the service brakes to be used if necessary during the upcoming braking event. In other words, in step S107 it can be predicted when to terminate step S108.

[0069] When step S108 has been initiated, the method 200 can further comprise a step S109 of controlling the braking force applied by means of the service brakes to meet the predicted required discharge amount of the energy storage device to be achieved prior to the time point of the start of the identified upcoming braking event (as obtained in step S105).

[0070] ​After the initiating step S108, the method 200 can further comprise a step S110 of deactivating the one or more service brakes in response to determining that the energy storage device has reached the required state of charge and / or that the temperature of the service brakes has reached the predetermined threshold temperature. In other words, the method can comprise the step of terminating the application of braking force by means of the service brakes if the energy storage device is no longer required to be discharged (it reaches a minimum threshold state of charge or has sufficient capacity for a regenerative braking event) and / or the service brakes have reached an undesirably high temperature. Thus, the step S108 can be seen as a safety step.

[0071] After any one of the steps S108 and / or the optional steps S109 and S110, the method can be terminated. Alternatively, the method can return to the start.

[0072] Figure 4 A flow chart representing a second exemplary embodiment 220 of a method for controlling a vehicle according to the present disclosure is schematically illustrated. The method 220 can comprise a step S104 of predicting whether the energy storage device will have sufficient capacity for the required regenerative braking power during the identified upcoming braking event. If it is predicted that the energy storage device will have sufficient capacity for the required regenerative braking power during the identified upcoming braking event, the method can return to the start. However, if (in step S104) it is predicted that the energy storage device will not have sufficient capacity for the required regenerative braking power during the identified upcoming braking event, the method proceeds to a step S120. The step S120 comprises presenting a suggestion to the driver of the vehicle of initiating a request to discharge the energy storage device prior to the identified upcoming braking event. The presentation of the suggestion can be performed by using any previously known way of presenting a suggestion action to the driver of the vehicle, e.g. visually (via e.g. a display) and / or acoustically.

[0073] After the step S120, the method comprises a step S121 of determining whether the driver has requested discharging of the energy storage device. If it is determined that the driver has not requested discharging of the energy storage device, the method 220 can return to the start. However, if it is determined that the driver has requested discharging of the energy storage device, the method can proceed to a step S108 in which a braking force is applied by enabling the service brakes. As described above in relation to the exemplary embodiment shown in Figure 3 According to one alternative, the application of braking force in the step S108 can be performed in a single braking phase during which vehicle propulsion force is also applied by means of the electric motor (as opposed to the two-phase braking described above in relation to the exemplary embodiment shown in Figure 5aby enabling service brakes in a plurality of consecutive braking phases, wherein the propulsion force is applied simultaneously for the total duration of at least two consecutive braking phases (as compared to Figure 5b by enabling service brakes in a plurality of consecutive braking phases, wherein the propulsion force is applied simultaneously for the total duration of at least two consecutive braking phases (as compared to Figure 5c by enabling service brakes in a plurality of consecutive braking phases, wherein the propulsion force is applied simultaneously for the total duration of at least two consecutive braking phases (as compared to

[0074] Although Figure 4 not shown in Fig. 1 1, the method can further comprise any one of steps S101 -S103, S105-S107 and S109 as described above with reference to Fig. 1 1. Figure 3

[0075] As previously discussed, the method of the present disclosure comprises applying a braking force by enabling one or more of the service brakes of the vehicle if it is predicted that there is not enough capacity for the required regenerative braking power during the identified upcoming braking event. The purpose of applying such a braking force is to increase the load on the electric motor so that it will result in an increased discharge of the energy storage device. In other words, the increased load on the electric motor is a result of the braking force applied by enabling one or more of the service brakes of the vehicle, which braking force is intended to be compensated for by the electric motor. This application of a braking force and the application of a propulsion force associated therewith is performed before the upcoming braking event starts. Figures 5a-5c Different alternatives of how the method according to the present disclosure can apply such a braking force by enabling one or more service brakes are schematically illustrated.

[0076] Figure 5a The braking force applied by one or more service brakes (upper part) and the vehicle propulsion force applied by the electric motor (lower part) over time are schematically illustrated. According to this alternative, the braking force is applied at the same time as the electric motor applies a propulsion force. The application of the braking force by means of one or more service brakes can be performed during a single braking phase starting at a first point in time tl. At a second point in time t2, the application of the braking force is terminated. The second point in time t2 is at a point in time t start BE before the estimated start of the braking event (also in contrast to Figure 2 ​(Comparison). The fact that braking force is terminated by means of one or more service brakes before the start of an upcoming braking event allows the temperature of the service brakes to decrease before the start of the upcoming braking event. Therefore, the increase in service brake temperature caused by the braking phase does not pose a risk of causing safety problems due to excessively high temperatures of the service brakes during a braking event. Furthermore... Figure 5a As shown, during the entire braking phase, the vehicle propulsion force is applied by an electric motor. If necessary, the application of vehicle propulsion force can be terminated after t2. Therefore, until t... start_be During this period, the electric motor can continue to apply propulsion to the vehicle, causing the energy storage device to discharge (albeit at a lower rate than during the braking phase described above). However, t2 and t start_be The vehicle propulsion force applied during the braking phase can preferably be lower than that during the braking phase to avoid an increase in vehicle speed just before the braking event begins. Alternatively, the propulsion force applied by the electric motor can terminate substantially simultaneously with the termination of the braking phase, or terminate before the termination of the braking phase.

[0077] Figure 5b This schematically illustrates an alternative approach to applying braking force by activating one or more of the vehicle's service brakes while the electric motor applies propulsive force to the vehicle. Figure 5b The alternatives shown are Figure 5a The alternative shown is similar, but differs in that one or more service brakes are activated in multiple consecutive braking phases 20 (three are shown in the figure). These multiple braking phases begin at t1 and (may occur at t2) start_BE The process terminates at t2 (previous point).

[0078] Figure 5c This schematically illustrates an alternative method for applying braking force by activating one or more of the vehicle's service brakes. Similar to... Figure 5b In the alternative shown, one or more service brakes are activated in several consecutive braking phases 20, and the total duration of the braking phases is within the range of t1 to t2. However, compared with... Figure 5b Compared to the alternative shown, during the corresponding braking phase, the electric motor does not apply vehicle propulsion. Instead, braking phase 20 is separated from vehicle acceleration phase 22. During this vehicle acceleration phase, propulsion is applied by the electric motor. During the vehicle acceleration phase, the reduction in vehicle speed caused by the application of the previous braking phase can be compensated for during the vehicle acceleration phase. Figure 5c As shown, it can be after t2 but but at t start_BE The final vehicle acceleration phase 24 is performed previously. However, if necessary, the final vehicle acceleration phase 24 can be omitted, or performed with a lower thrust compared to the previous vehicle acceleration phase 22.Figure 5c As illustrated in the middle, the combination of multiple braking phases separated by vehicle acceleration phases results in a higher discharge of the energy storage device compared to the case where the vehicle's travel route is assumed, for the same average vehicle speed, only a propulsion force (i.e. no braking force) would be applied.

[0079] Figure 6 An exemplary embodiment of the device 500 is schematically illustrated. The above-mentioned control device 100 can for example comprise the device 500, consist of the device 500, or be comprised in the device 500.

[0080] 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, such as an operating system, is stored to control the functions of the device 500. The device 500 further comprises a bus controller, a serial communication port, I / O devices, an A / D converter, a time and date input and transmission unit, an event counter and an interrupt controller (not depicted). The non-volatile memory 520 further has a second memory element 540.

[0081] A computer program P is provided, comprising instructions for controlling a vehicle comprising an energy storage device, an electric motor powered by the energy storage device and at least one service brake configured to brake a wheel of the vehicle. The computer program comprises instructions to apply a braking force by enabling the service brake if the energy storage device is predicted to not have sufficient capacity for a required regenerative braking power during an identified upcoming braking event. The computer program can comprise instructions to perform said application of the braking force while the electric motor applies a propulsion force of the vehicle. Alternatively, the computer program can comprise instructions to apply said braking force by enabling the service brake in a plurality of consecutive braking phases in which the propulsion force of the electric motor is temporarily interrupted, said braking phases being separated by vehicle acceleration phases during which a propulsion force is applied by the electric motor.

[0082] The program P can be stored in the memory 560 and / or the read / write memory 550 in an executable form or in a compressed form.

[0083] The data processing unit 510 can execute one or more functions, i.e. the data processing unit 510 can implement 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.

[0084] The data processing device 510 can communicate with the data port 599 via a data bus 515. The non-volatile memory 520 is intended to communicate 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 can be achieved by a communication link. The communication link can be a physical connection, such as an optoelectronic communication line, or a non-physical connection, such as a wireless connection, for example a radio link or a microwave link.

[0085] When receiving data on the data port 599, they can be temporarily stored in the second memory element 540. When the received input data has been temporarily stored, the data processing unit 510 is ready to implement the code execution as described above.

[0086] The parts of the method described herein can be implemented by the device 500 by means of the data processing unit 510 running a program stored in the memory 560 or the read / write memory 550. When the device 500 runs the program, the method described herein is executed.

Claims

1. A method (200, 220) for controlling a vehicle (1), performed by a control device (100), the vehicle (1) comprising: an energy storage device (3) chargeable by regenerative braking of the vehicle (1), a propulsion unit in the form of an electric motor (2) powered by the energy storage device (3), and at least one service brake (10) configured to brake a wheel (7, 8) of the vehicle (1); the method (200, 220) comprising the steps of: applying (S018) a braking force by activating the service brake (10) if it is predicted that the energy storage device will not have sufficient capacity for a required regenerative braking power during an identified upcoming braking event, wherein the service brake (10) is activated while the electric motor (2) applies a propulsion force, or in a plurality of consecutive braking phases (20) in which the propulsion force of the electric motor (2) is temporarily interrupted, the braking phases (20) being separated by vehicle acceleration phases (22) during which a propulsion force is applied by the electric motor (2); the method further comprising: a second time point (t2) at which the application of the braking force by activation of the service brake (10) should be terminated to allow the service brake (10) to have a required temperature at the start (t start_BE ) of the braking event, and terminating the step of applying (S108) a braking force by activating the service brake at the second point in time (t2) if the service brake (10) has not been deactivated.

2. The method (200, 220) according to claim 1, further comprising: based on an estimated state of charge of the energy storage device (3) at the start (t start_BE ) of the upcoming braking event and an estimated charge generated by regenerative braking during the identified upcoming braking event, it is predicted (S104) whether the energy storage device (3) will have sufficient capacity for the required regenerative braking power during the identified upcoming braking event.

3. The method (200, 220) according to claim 1 or 2, wherein the step of applying (S018) a braking force by activating the service brake is performed in order to keep a vehicle speed within a preselected speed interval.

4. The method (200, 220) according to claim 1 or 2, further comprising: predict (S105) a required discharge amount of the energy storage device to be implemented before a time point (t start_BE ) of a start of the identified upcoming braking event, to allow a required regenerative braking power during the braking event.

5. The method (200, 220) according to claim 4, further comprising: predicting a first point in time (tl) at which a braking force should be applied by means of the service brake (10), and activating the service brake at the first point in time (tl).

6. The method (200, 220) of claim 4, further comprising: controlling (S109) the braking force applied by means of the service brake (10) to meet a required discharge amount of the energy storage device to be achieved before a predicted time point (t start_BE ) of the start of the identified upcoming braking event.

7. The method (200, 220) of claim 1 or 2, further comprising: deactivating (S110) the service brake in response to determining that the energy storage device (3) has reached a required state of charge and / or a temperature of the service brake (10) has reached a predetermined threshold temperature.

8. The method (200, 220) of claim 1 or 2, further comprising: controlling a temperature of the energy storage device (3) to increase a regenerative braking power available during the braking event.

9. A computer program product comprising instructions which, when executed by a control device (100), cause the control device (100) to perform the method according to any one of claims 1 to 8.

10. A computer readable medium comprising instructions which, when executed by a control device (100), cause the control device (100) to perform the method according to any one of claims 1 to 8.

11. A control device (100) configured to control a vehicle (1), the vehicle (1) comprising: an energy storage device (3) chargeable by regenerative braking of the vehicle (1), a propulsion unit in the form of an electric motor (2) powered by the energy storage device (3), and at least one service brake (10) configured to brake a wheel (7, 8) of the vehicle (1); wherein the control device (100) is configured to: if it is predicted that the energy storage device (3) will not have sufficient capacity for the required regenerative braking power during the identified upcoming braking event, then (i) apply a braking force by activating the service brake (10) while the electric motor applies a propulsion force, or (ii) apply a braking force by activating the service brake (10) in a plurality of consecutive braking phases (20) in which the propulsion force of the electric motor (2) is temporarily interrupted, the braking phases (20) being separated by vehicle acceleration phases (22) during which a propulsion force is applied by the electric motor (2); wherein the control device (100) is further configured to: to predict a second point in time (t2) at which the application of the braking force by activation of the service brake (10) should be terminated to allow the service brake (10) to have a desired temperature at the beginning (t start_BE ) of the braking event, and terminate the step of applying (S108) a braking force by activating the service brake (10) at the second point in time (t2) if the service brake (10) has not been deactivated.

12. The control device (100) according to claim 11, further configured to predict a required discharge amount of the energy storage device to be achieved before a time point (t start_BE ) of the identified upcoming braking event start to allow a required regenerative braking power during the braking event.

13. The control device (100) according to claim 12, further configured to: predict a first point in time (ti) at which a braking force should be applied by means of the service brake (10); and activate the service brake (10) at the first point in time (ti); and terminate the step of applying a braking force by activating the service brake (10) at the second point in time (t2) if the service brake (10) has not been deactivated.

14. The control device (100) according to any one of claims 11 to 13, further configured to deactivate the service brake (10) in response to determining that the energy storage device (3) has reached a required state of charge and / or a temperature of the service brake (10) has reached a predetermined threshold temperature.

15. A vehicle (1) comprising a control device (100) according to any one of claims 11 to 14.

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