Controll arrangement and method for controlling a vehicle

Abstract

Control arrangement (100) and method for controlling a vehicle (1), said vehicle (1) comprising a powertrain (2) configured to transmit torque to one or more drive wheels (7) of the vehicle (1). The powertrain (2) comprises a transmission arrangement (4), and an auxiliary brake system (11, 12, 13) arranged upstream of the transmission arrangement (4). The method comprises, when slip control of the vehicle (1) is initiated and / or actively performed, determining (S102) a desired brake torque operational range for slip control of the vehicle (1). The method further comprises, when the vehicle (1) is braked using the auxiliary brake system (11, 12, 13), activating (S104) an adjusted gear selection strategy so that the transmission arrangement (4) is controlled in accordance therewith. Said adjusted gear selection strategy comprises selecting a gear that, for a predefined operational output torque window for the auxiliary brake system (11, 12, 13), results in an available brake torque operational range at the one or more drive wheels (7) that falls within, and / or provides a broadest overlap with, the determined desired brake torque operational range for slip control.

Description

[0001] CONTROLL ARRANGEMENT AND METHOD FOR CONTROLLING A VEHICLE

[0002] TECHNICAL FIELD

[0003] The present disclosure relates in general to a method for controlling a vehicle. The present disclosure also relates in general to a control arrangement configured to control a vehicle, as well as a vehicle comprising the control arrangement.

[0004] The present disclosure also relates in general to a computer program, and a computer-readable medium.

[0005] BACKGROUND

[0006] Vehicle powertrains, in particular powertrains for heavy vehicles, typically comprise a transmission arrangement arranged between one or more power sources (such as an internal combustion engine and / or one or more electric machines) and the drive wheels of the vehicle, wherein the transmission arrangement is controllable between different gears to provide different transmission ratios between the power source(s) and the drive wheels.

[0007] A controllable transmission arrangement allows for advantages in terms of performance, efficiency, and driving experience of the vehicle. For example, by enabling selection of different gears, the performance of the vehicle may be adapted to the driving conditions. At low speeds, using a lower gear increases the torque available at the wheels, which is particularly useful for starting from a standstill or climbing steep slopes. Moreover, at higher speeds, selecting a higher gear reduces the speed of the one or more power sources. This reduction is crucial for enhancing fuel efficiency in internal combustion engines and extending battery life in electric or hybrid vehicles by minimizing energy consumption. It also contributes to a quieter and more comfortable ride, as lower power source speeds reduce noise and vibration. Furthermore, the ability to switch gears allows the vehicle to operate within an optimal power band of the power source(s). This means the power source(s) can work within the most energy efficient range, which in turn reduces energy consumption of the vehicle.

[0008] Transmission arrangements are typically controlled in accordance with predetermined gear selection strategies. Gear selection strategies define appropriate gear ratio, and thus the gear to be selected, to match the vehicle’s operating conditions, such as load, terrain, and travelling speed requirements. Gear selection strategies typically also define one or more criteria for when to perform a gear shift, for example power source speeds at which an upshift / downshift should be performed. As may be realized from the above, gear selection strategies are important for improving vehicle performance, energy efficiency, drivability, and driver comfort.

[0009] Slip control is a vital technology in vehicles, aimed at maintaining traction and enhancing safety during operation. It manages the interaction between the tires and the road to prevent excessive slipping, which can compromise vehicle control, especially under challenging road conditions such as wet, icy or uneven roads. Slip control systems, including traction control systems (TCS) and anti-lock braking systems (ABS), are designed to counteract the negative effects of slipping by automatically adjusting braking power / torque or reducing output power of the power source(s). Most modern vehicles comprise both TCS and ABS. Furthermore, these slip control systems may often be integrated into broader stability systems, such as an electronic stability control system (ESC) or the like.

[0010] A traction control system normally operates by applying a brake torque to one or more drive wheels, and / or by reducing the power output of the power source(s) of the vehicle, if it is detected that the one or more drive wheels spins significantly faster than a threshold set from a speed estimate of the vehicle. The speed estimate of the vehicle may for example be obtained using input from a number of wheel sensors configured to sense the rotational speed of nondriven wheels. An anti-lock braking system operates by reducing the braking torque on a wheel if it is detected that the wheel is rotating significantly slower than a threshold set from a speed estimate of the vehicle. Like above, the speed estimate of the vehicle may for example be obtained using input from wheel sensors configured to sense the rotational speed of one or more non-driven wheels of the vehicle.

[0011] Preventing locking of wheels during slip control is crucial for several safety and performance reasons. For example, locked wheels can cause a vehicle to destabilize, especially in case of heavy vehicles where weight distribution plays an important role. Moreover, when wheels lock during braking, they lose traction and begin to skid across the road surface, leading to a loss of steering ability and increased tire wear. By preventing wheel lock, systems like ABS ensure that the maximum possible braking force may be applied to vehicle without losing traction, leading to shorter and more consistent stopping distances. Vehicles may be braked using different brake systems, including both service brake systems and auxiliary brake systems. Examples of auxiliary brake systems include various engine brake systems, regenerative brake systems, various types of retarders, and the like. Not only the service brake system, but also auxiliary brake systems can be used during slip control if the vehicle's slip control system(s) are designed to integrate and control them effectively. Modern heavy vehicles often include such an integration, ensuring that auxiliary braking contributes to overall stability and traction, even under slip conditions.

[0012] SUMMARY

[0013] The object of the present invention is to improve the ability to brake a vehicle under slip conditions, to thereby further improve e.g., safety in operation of the vehicle.

[0014] The object is achieved by the subject-matter of the appended independent claim(s).

[0015] The present disclosure relates to a method, performed by a control arrangement, for controlling a vehicle. The vehicle comprises a powertrain configured to transmit torque to one or more drive wheels of the vehicle. Said powertrain comprises a transmission arrangement, and an auxiliary brake system arranged upstream of the transmission arrangement. The method comprises a step of, when slip control of the vehicle is initiated and / or actively performed, determining a desired brake torque operational range for slip control of the vehicle. The method further comprises a step of, when the vehicle is braked, or about to be braked, using the auxiliary brake system, activating an adjusted gear selection strategy for the transmission arrangement so that the transmission arrangement is controlled in accordance with the adjusted gear selection strategy. Said adjusted gear selection strategy comprises selecting a gear, from a plurality of possible gears of the transmission arrangement, that, for a predefined operational output torque window for the auxiliary brake system, results in an available brake torque operational range at the one or more drive wheels that falls within, and / or provides a broadest overlap with, the determined desired brake torque operational range for slip control.

[0016] Among other things, the herein described method achieves a more controlled (as perceived by e.g., a driver of the vehicle) braking of the vehicle when wheels of the vehicle are slipping, and reduces the risk of having to interrupt braking of the one or more drive wheels due to risk for wheel locking, which contributes to improved safety in operation of the vehicle. This is achieved by the herein described method adopting an adjusted gear selection strategy when the vehicle is braked by an auxiliary brake system, arranged upstream of the transmission arrangement, during slip control. By means of said adjusted gear selection strategy, a good balance between the brake torque that may be transmitted to the one or more drive wheels, controllability of the auxiliary brake system, and output torque of the auxiliary brake is achieved. In essence, gear selection is, in accordance with the adjusted gear selection, made so that the resulting available braking torque range, that may be transmitted to the one or more drive wheels when the auxiliary brake system is operated within its predefined operational output torque window, best matches the desired brake torque operational range for slip control.

[0017] Normally, a gear that maximizes the possible braking torque that may be transmitted from the auxiliary brake system (arranged upstream of the transmission arrangement) to the drive wheels is typically selected in accordance with conventional gear selection strategies during braking of a vehicle. In other words, a lower gear (and thus higher transmission ratio) may typically be selected in accordance with a default gear selection strategy for the transmission arrangement. However, once tire slip has risen, precise control of braking torque at the one or more drive wheels and an ability to achieve lower braking torques at the one or more drive wheels, are needed for efficient slip control. Auxiliary brake systems may often have impaired controllability when operated outside of their predefined operational output torque window. During slip control, it is therefore especially important to be able to operate within said window so that also precise control of braking torque at the one or more drive wheels may be achieved. This is accomplished by the herein described method which adopts the adjusted gear selection strategy as described above. However, not only the controllability of the auxiliary brake system is important, but also the ability to reduce braking torque transmitted to the one or more drive wheels without having to switch gear during braking, which could lead to a temporary interruption in braking torque to the one or more drive wheels. Therefore, a higher gear (and thus lower transmission ratio) than would normally have been selected (when possible slip is so low that slip control is not needed) may often be suitable during slip control. This is also achieved by the adjusted gear selection strategy utilized in accordance with the herein described method.

[0018] The step of determining a desired brake torque operational range for slip control of the vehicle may comprise determining an upper limit for the desired brake torque operational range that allows maximum braking of the vehicle without causing locking of the one or more drive wheels. Thereby, the ability to safely brake the vehicle after gear selection according to the adjusted gear selection strategy is further improved. Moreover, this may lead to shorter stopping distances, when the vehicle may need to be braked to a stop.

[0019] The method may further comprise a step of initiating slip control in response to a determination that a wheel slip of at least one of the one or more drive wheels is above a threshold wheel slip and / or a derivative of wheel slip of at least one of the one or more drive wheels is above threshold derivative. It should however be noted that slip control may alternatively be initiated in response to detection of one or more other predetermined criteria therefore being fulfilled.

[0020] The method may further comprise a step of, when active slip control of the vehicle is terminated, deactivating the adjusted gear selection strategy so that the transmission arrangement is controlled in accordance with a default gear selection strategy. This ensures that the transmission arrangement will be controlled in accordance with an appropriate gear selection strategy therefore, applicable to the prevailing driving conditions when slip control no longer is needed or desired.

[0021] The method may further comprise a step of, in response to a determination that the vehicle no longer is braked by the auxiliary brake system, deactivating the adjusted gear selection strategy so that the transmission arrangement is controlled in accordance with a default gear selection strategy. When the vehicle is no longer braked by the auxiliary brake system, there is no need to adapt gear selection to the controllability thereof and the risk for wheel locking due to the vehicle being braked by the auxiliary brake system is removed. Thus, energy efficiency and performance of the vehicle may be improved by reverting back to the default gear selection strategy for the transmission arrangement, even in situations where slip control may be continued.

[0022] The present disclosure also related to a control arrangement configured to control a vehicle, said vehicle comprising a powertrain being configured to transmit torque to one or more drive wheels of the vehicle. Said powertrain comprises a transmission arrangement, and an auxiliary brake system arranged upstream of the transmission arrangement. The control arrangement is configured to, when slip control of the vehicle is initiated and / or actively performed, determine a desired brake torque operational range for slip control of the vehicle. The control arrangement is further configured to, when the vehicle is braked, or about to be braked, using the auxiliary brake system, activate an adjusted gear selection strategy for the transmission arrangement so that the transmission arrangement is controlled in accordance with the adjusted gear selection strategy. Said adjusted gear selection strategy comprises selecting a gear, from a plurality of possible gears of the transmission arrangement, that, for a predefined operational output torque window for the auxiliary brake system, results in an available brake torque operational range at the one or more drive wheels that falls within, and / or provides a broadest overlap with, the determined desired brake torque operational range for slip control.

[0023] The control arrangement provides the same advantages as described above with respect to the corresponding method for controlling a vehicle.

[0024] The control arrangement may be configured to determine an upper limit of the desired brake torque operational range for slip control of the vehicle sufficient for allowing maximum braking of the vehicle without causing locking of the one or more drive wheels.

[0025] The control arrangement may optionally further be configured to perform slip control of the vehicle. In other words, the herein described control arrangement may be comprised in a slip control system of the vehicle, if desired.

[0026] The control arrangement may further be configured to deactivate the adjusted gear selection strategy, so that the transmission arrangement is controlled in accordance with a default gear selection strategy, when it is determined that active slip control of the vehicle is terminated and / or when it is determined that the vehicle is no longer braked by the auxiliary brake system.

[0027] The present disclosure further relates to a computer program comprising instructions which, when executed by the above described control arrangement configured to control a vehicle, cause the control arrangement to carry out the above described method for controlling a vehicle.

[0028] Moreover, the present disclosure relates to a computer-readable medium having stored thereon the computer program described above.

[0029] The present disclosure also relates to a vehicle comprising the control arrangement configured to control a vehicle as described above. The vehicle also comprises a powertrain configured to transmit torque to one or more drive wheels of the vehicle. The powertrain comprises a transmission arrangement, and an auxiliary brake system arranged upstream of the transmission arrangement. The above described auxiliary brake system may for example be an engine brake system, a regenerative brake system, or a pre-transmission retarder.

[0030] In case the auxiliary brake system is an engine brake system, said engine brake system may comprise an exhaust brake system, a compression release brake system, variable valve brake system, and / or a variable vane brake system.

[0031] The vehicle may be heavy-duty vehicle, such as a bus or a truck, but is not limited thereto. Moreover, the vehicle may be a fully electric vehicle (in which case, the vehicle does not comprise an engine brake system), a hybrid vehicle, or a vehicle driven solely by a combustion engine (in which case, the vehicle does not comprise a regenerative brake system). The vehicle may alternatively be a fuel cell vehicle, in which case the vehicle comprises one or more electrical machines powered by a fuel cell stack. Each of these one or more electrical machines may be utilized as a regenerative brake system of the powertrain, and thus an auxiliary brake system arranged upstream of the transmission arrangement.

[0032] BRIEF DESCRIPTION OF DRAWINGS

[0033] Fig. 1 schematically illustrates an example of a vehicle,

[0034] Fig. 2 schematically illustrates an example of a powertrain of a vehicle,

[0035] Fig. 3 represents a flowchart schematically illustrating one exemplifying embodiment of the herein described method for controlling a vehicle,

[0036] Fig. 4 schematically illustrates gear selection in accordance with the adjusted gear selection strategy used in accordance with the herein described method, and

[0037] Fig. 5 schematically illustrates an exemplifying embodiment of a device that may comprise, consist of, or be comprised in the herein described control arrangement for controlling a vehicle. DETAILED DESCRIPTION

[0038] 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.

[0039] The present disclosure relates to a method for controlling a vehicle. More specifically, the present disclosure relates to a method for controlling a vehicle in conjunction with slip control of the vehicle. In other words, the herein described method may be performed upon activation of slip control and / or during slip control, and may be continued to be performed until after slip control has been terminated. Slip control of the vehicle may be performed using one or more slip control systems of the vehicle as known in the art.

[0040] The vehicle that is controlled in accordance with the herein described method comprises at least one powertrain configured to transmit torque to one or more drive wheels of the vehicle. The torque transmitted to said one or more drive wheels may be either a propulsion torque or a braking torque depending on the driving conditions. Typically, the said at least one powertrain is configured to transmit torque to a set of drive wheels of the vehicle (i.e. a plurality of drive wheels of the vehicle). In case of the vehicle comprising more than one powertrain, each of said powertrains may be configured to transmit torque to a respective set of drive wheels.

[0041] The at least one powertrain of the vehicle comprises a transmission arrangement. Said transmission arrangement is configured to, by shifting between different gears of the transmission arrangement, provide different transmission ratios between at least one power unit of the powertrain and the one or more drive wheels of the vehicle. In other words, the transmission arrangement comprises a plurality of possible gears. Such a transmission arrangement is sometimes referred to as a multispeed transmission arrangement, as opposed to a single speed transmission arrangement that is not shiftable. The transmission arrangement may for example comprise, or consist of, an automated manual transmission (AMT), but is not limited thereto. The transmission arrangement may for example alternatively be, or comprise, a dual clutch transmission (DCT), or have a configuration as described in US 2016 / 0053864 A1 . The powertrain further comprises an auxiliary brake system arranged upstream of the transmission arrangement. Such an auxiliary brake system may alternatively be described as a pre-transmission auxiliary brake system, or an auxiliary brake system acting on a power unit side of the transmission arrangement. In other words, said auxiliary brake system may be operably connected, or at least connectable, to an input shaft of the transmission arrangement. The auxiliary brake system that is arranged upstream of the transmission arrangement may for example comprise (or consist of) an engine brake system, a regenerative brake system, and / or a pre-transmission retarder. In case the auxiliary brake system is an engine brake system, it may comprise an exhaust brake system, a compression release brake system, a variable valve brake system, or a variable vane brake system. It is also plausible that the engine brake system comprises at least two of an exhaust brake system, a compression release brake system, a variable valve brake system, and a variable vane brake system.

[0042] It should here be noted that the powertrain may optionally further comprise an auxiliary brake system arranged downstream of the transmission arrangement, without departing from the present disclosure. One example of an auxiliary brake system arranged downstream of the transmission arrangement is a conventional retarder, often an oil retarder, connected to an output shaft of the transmission arrangement. However, when an auxiliary brake system is discussed in the present disclosure, an auxiliary brake system arranged upstream of the transmission arrangement is intended to be referred to, unless explicitly disclosed otherwise or immediately apparent from the context in which it is mentioned.

[0043] The herein described method for controlling a vehicle comprises a step of, when slip control of the vehicle is initiated and / or actively performed, determining a desired brake torque operational range for slip control of the vehicle. Such a desired brake torque operational range is defined by an upper limit and a lower limit of (desired) brake torque that may be transferred to the one or more drive wheels of the vehicle.

[0044] The method further comprises a step of, when the vehicle is braked, or about to be braked, using the auxiliary brake system (while slip control of the vehicle is performed), activating an adjusted gear selection strategy for the transmission arrangement so that the transmission arrangement is controlled in accordance with the adjusted gear selection strategy. The adjusted gear selection strategy comprises selecting a gear, from the plurality of possible gears of the transmission arrangement, that, for a predefined operational output torque window for the auxiliary brake system, results in an available brake torque operational range at the one or more drive wheels that falls within, and / or provides a broadest overlap with, the determined desired brake torque operational range for slip control. The above mentioned predefined operational output torque window for the auxiliary brake system (that is arranged upstream of the transmission arrangement) may suitably correspond to an operational output torque window within which the auxiliary brake system has appropriate controllability.

[0045] The above mentioned step of determining a desired brake torque operational range for slip control of the vehicle may comprise determining an upper limit for the desired brake torque operational range that allows maximum braking of the vehicle without causing locking of the one or more drive wheels. This may be performed in accordance with any previously known technique, used by slip control systems, for determining maximum braking torque that may be applied to the respective drive wheels before causing locking thereof. Such techniques are known in the art, and will therefore not be discussed in detail herein.

[0046] In most cases, the lower limit of the desired brake torque operational range for slip control of the vehicle may be selected to be zero, or at least close to zero. This is due to the fact that it is typically desirable to be able to reduce the braking torque transmitted to the drive wheels as far as possible during slip control. Therefore, it may not be needed to estimate or calculate a lower limit for the desired torque operational range for slip control, but simply select the lower limit to be zero. However, in some situations, it may be needed or at least appropriate to determine a lower limit of the desired brake torque operational range for slip control which is higher than zero torque. This could for example be due to one or more inherent limitations of the auxiliary brake system intended to be used during slip control, and / or one or more limitations dependent of, or inherent to, the vehicle configuration. Thus, the step of determining a desired brake torque operational range for slip control of the vehicle may comprise determining a lower limit for the desired brake torque operational range to be zero, or determining a lower limit for the desired brake torque operational range in consideration of limitations of the auxiliary brake system (arranged upstream of the transmission arrangement and intended or envisaged to be used during slip control) and / or vehicle configuration.

[0047] As previously described, the desired brake torque operational range for slip control is determined when slip control of the vehicle is initiated and / or actively performed. Slip control may for example be initiated in response to a determination that a wheel slip of at least one of the one or more drive wheels is above a threshold wheel slip and / or a derivative of wheel slip of at least one of the one or more drive wheels is above a threshold derivative. Slip control may however alternatively be initiated in response to other factors as known in the art, if desired.

[0048] The method may suitably further comprise a step of, when active slip control of the vehicle is terminated, deactivating the adjusted gear selection strategy so that the transmission arrangement is controlled in accordance with a default gear selection strategy. Active slip control of the vehicle may for example be terminated in response to a driver-initiated request therefore, or automatically terminated in response to a determination that slip control is no longer needed to maintain an acceptable traction of the vehicle. When slip control is no longer actively performed, there is no need for the transmission arrangement to be controlled in accordance with the adjusted gear selection strategy and it may be more appropriate, e.g., for energy efficiency and / or vehicle performance, to control the transmission arrangement in accordance with the default gear selection strategy.

[0049] The method may further comprise a step of, in response to a determination that the vehicle no longer is braked by the auxiliary brake system that is arranged upstream of the transmission arrangement, deactivating the adjusted gear selection strategy so that the transmission arrangement is controlled in accordance with the default gear selection strategy. Thus, irrespectively of whether slip control is performed, the transmission arrangement may be controlled usingthe default gear selection strategy when said auxiliary brake system is no longer used for braking the vehicle. This may for example contribute to improved energy efficiency and / or performance of the vehicle.

[0050] The performance of the herein described method for controlling a vehicle 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. 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, or a control arrangement comprising the computer, to carry out the herein described method for controlling a vehicle. 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.

[0051] The present disclosure further relates to a control arrangement configured to control a vehicle. The control arrangement may be configured to perform any one of the steps of the method for controlling a vehicle as described above.

[0052] More specifically, in accordance with the present disclosure, a control arrangement configured to control a vehicle, such as in conjunction with slip control of the vehicle, is provided. The vehicle, which may be controlled by said control arrangement, comprises a powertrain configured to transmit torque to one or more drive wheels of the vehicle. Said powertrain comprises a transmission arrangement, and an auxiliary brake system arranged upstream of the transmission arrangement. The control arrangement is configured to, when slip control of the vehicle is initiated and / or actively performed, determine a desired brake torque operational range for slip control of the vehicle. The control arrangement is further configured to, when the vehicle is braked, or about to be braked, using the auxiliary brake system (while slip control is performed), activate an adjusted gear selection strategy for the transmission arrangement so that the transmission arrangement is controlled in accordance with the adjusted gear selection strategy. The adjusted gear selection strategy comprises selecting a gear, from a plurality of possible gears of the transmission arrangement, that, for a predefined operational output torque window for the auxiliary brake system, results in an available brake torque operational range at the one or more drive wheels that falls within, and / or provides a broadest overlap with, the determined desired brake torque operational range for slip control.

[0053] 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 control a certain function / step or a certain function / step may be divided between more than one control units. The control arrangement may be a control arrangement of a transmission arrangement of the vehicle, or a control arrangement of a slip control system of the vehicle. In the latter case, the slip control system is configured to communicate with the transmission arrangement for the purpose of performing the herein described method. Alternatively, the control arrangement may be any other control arrangement of the vehicle but configured to communicate with the transmission arrangement of the vehicle for the purpose of performing the herein described method.

[0054] Figure 1 schematically illustrates an example of a vehicle 1 , here illustrated as a truck. The exemplified vehicle 1 comprises a powertrain 2 configured to transmit torque to drive wheels 7 of the vehicle for the purpose of providing motive force or braking force, depending on the driving situation, to the vehicle. The powertrain 2 comprises a combustion engine 3 configured to serve as a power source, and a transmission arrangement 4 that may be shifted between different gears. The combustion engine 3 may be connected to the transmission arrangement 4 via a clutch (cf. Figure 2). The transmission arrangement 4 may in turn be connected to the drive wheels 7 of the vehicle 1 via an output shaft 6 of the transmission arrangement 4. The vehicle 1 further comprises front wheels 8 and optionally also tag axle wheels 9. It should be noted that although Figure 1 illustrates a vehicle 1 comprising drive wheels 7 arranged in front of tag axle wheels 9, and thus a driven axle in front of the tag axle, a possible tag axle may alternatively or additionally be arranged in front of the drive axle in case the vehicle comprises such a tag axle. The vehicle 1 may alternatively, or additionally, comprise a plurality of driven axles with associated drive wheels 7. The plurality of driven axles may be comprised in the same powertrain 2. Alternatively, the vehicle 1 may comprise a plurality of mechanically separate powertrains that may be controlled independently of each other. In such a case, each of the mechanically separated powertrains may comprise its own driven axle with associated drive wheels 7.

[0055] The present disclosure is not limited to a vehicle driven by a combustion engine. The vehicle 1 may additionally, or alternatively, comprise one or more electrical machines 5 (only one shown in the figure) configured to serve as power source(s). Said one or more electrical machines 5 are part of the powertrain 2.

[0056] The vehicle 1 comprises a service brake system 10. The service brake system may comprise service brakes 10a arranged at the respective drive wheels 7, service brakes 10b arranged at the front wheels 8 and / or service brakes 10c arranged at any other wheel of the vehicle 1 as shown in the figure. The vehicle 1 further comprises one or more auxiliary brake systems. For example, the vehicle 1 may comprise an auxiliary brake system in the form of a retarder 14. Such a retarder 14 may for example be connected to an output shaft of the transmission arrangement 4 as illustrated in the figure, and is in such a case arranged downstream of the transmission arrangement 4. Alternatively, a retarder may be connected to a shaft of the combustion engine 3 (as shown in Figure 2), in which case it is arranged upstream of the transmission arrangement 4. Additionally, or alternatively, the vehicle 1 may comprise an auxiliary brake system in the form of an engine brake system 12. The engine brake system 12 may for example comprise a compression release brake system, an exhaust brake system, a variable valve brake system, and / or a variable vane brake system. Furthermore, when present, the electrical machine 5 may also serve as an auxiliary brake system in the form of a regenerative brake system 13. When serving as a regenerative brake system 13, the electrical machine 5 is operated as generator for the purpose of converting kinetic energy of the vehicle to electrical energy which for example may be used to charge an energy storage device (not shown) of the vehicle. The energy stored in the energy storage device may thereafter be used for the purpose of driving the electrical machine 5 when the electrical machine 5 is operated as a machine generating motive power.

[0057] The vehicle 1 further comprises a control arrangement 100 configured to control the vehicle. Said control arrangement 100 may be configured to perform the herein described method for controlling a vehicle. The vehicle 1 further comprises a slip control system 200. The control arrangement 100 may be a part of the slip control system 200. Alternatively, the control arrangement 100 may be separate from the slip control system 200, but configured to communicate therewith.

[0058] Figure 2 schematically illustrates an example of a powertrain 2 of a vehicle, such as the vehicle 1 shown in Figure 1 . The exemplified powertrain 2 comprises both a combustion engine 3 and an electrical machine 5, each configured to serve as a power source. Thus, the exemplified powertrain 2 is a hybrid powertrain. The powertrain 2 further comprises a transmission arrangement 4 having an output shaft 6 that is connected to a set of drive wheels 7 of the vehicle via a differential 16 and a drive shaft 17. The differential 16, drive shaft 17 and drive wheels 7 are comprised in the powertrain 2.

[0059] The combustion engine 3 is connected to an input shaft 4a of the transmission arrangement 4 via a clutch 18. Moreover, the electrical machine 5 is arranged to be connectable to the input shaft 4a of the transmission arrangement 4. The powertrain 2 comprises one or more auxiliary brake systems. For example, the powertrain 2 may comprise a retarder 11 connectable to a crankshaft (not shown) of the combustion engine 3. In such a case, the retarder is arranged upstream of the transmission arrangement 4. The powertrain 2 may further comprise an engine brake system 12 and / or a regenerative brake system 13, as shown in the figure. As described above, the engine brake system 12 may for example comprise a compression release brake system, an exhaust brake system, a variable valve brake system, and / or a variable vane brake system. Moreover, the regenerative brake system 13 may comprise operating the electrical machine 5 as a generator. Similarly to the retarder, each of the engine brake system 12 and the regenerative brake system 13 are arranged upstream of the transmission arrangement 4. The powertrain 2 may also comprise an auxiliary brake system arranged downstream of the transmission arrangement 4, such as a retarder 14 connected to the output shaft 6 of the transmission arrangement 4.

[0060] It should here be noted that the present disclosure is not limited to the powertrain 2 illustrated in Figure 2. The powertrain of the vehicle according to the present disclosure may for example alternatively be a fully electric powertrain, in which case the powertrain does not comprise any combustion engine 3. Alternatively, the powertrain 2 may be a powertrain which does not comprise any electrical machine 5, but merely comprises a single power source in the form of a combustion engine 3.

[0061] The powertrain 2, or at least parts thereof, may be controlled by the previously described control arrangement 100 configured to perform the herein described method for controlling a vehicle.

[0062] Figure 3 represents a flowchart schematically illustrating one exemplifying embodiment of the herein described method for controlling a vehicle. Optional steps of the exemplifying embodiment are illustrated using dashed lines.

[0063] The method may comprise an initial step S101 of initiating slip control of the vehicle in response to a determination that a wheel slip of at least one of the one or more drive wheels is above a threshold wheel slip and / or a derivative of wheel slip of at least one of the one or more drive wheels is above a threshold derivative. In case the method does not comprise the step S101 , slip control has already been initiated when the method starts. The method comprises a step S102 of, when slip control of the vehicle is initiated and / or actively performed, determining a desired brake torque operational range for slip control of the vehicle.

[0064] After step S102, the method proceeds to a step S103 of determining whether the vehicle is braked, or is about to be braked, by the auxiliary brake system that is arranged upstream of the transmission arrangement. In case the vehicle is not braked by said auxiliary brake system and it is not foreseen that the vehicle will be braked by the auxiliary brake system within short, the method may be reverted back to step S102. However, in case it is determined that the vehicle is braked, or is about to be braked, by said auxiliary brake system, the method proceeds to the subsequent step S104.

[0065] Step S104 comprises activating an adjusted gear selection strategy for the transmission arrangement so that the transmission arrangement is controlled in accordance with the adjusted gear selection strategy. Said adjusted gear selection strategy comprises selecting a gear, from the plurality of possible gears of the transmission arrangement, that, for a predefined operational output torque window for the auxiliary brake system, results in an available brake torque operational range at the one or more drive wheels that falls within, and / or provides a broadest overlap with, the determined desired brake torque operational range for slip control.

[0066] The method may further comprise a step S105 of determining whether one or more predefined criteria for deactivation of the adjusted gear selection strategy are met. For example, step S105 may comprise determining whether braking of the vehicle by means of the auxiliary brake system arranged upstream of the transmission arrangement has been terminated (i.e. the vehicle is no longer braked by the auxiliary brake system), and / or determining whether active slip control of the vehicle has been terminated (either automatically or in response to a driver- initiated request therefore). As shown in the figure, step S105 may be repeated until it is determined that at least one of said one or more predefined criteria for deactivation of the adjusted gear selection strategy is met. Thereafter, the method may proceed to a step S106 of deactivating the adjusted gear selection strategy so that the transmission arrangement is controlled in accordance with a default gear selection strategy. Thereafter, the method may be ended, as shown in the figure, or reverted to start.

[0067] Figure 4 schematically illustrates gear selection in accordance with the adjusted gear selection strategy for the transmission arrangement. In the figure, (brake) torque is abbreviated Tq. On the left hand side of Figure 4, a predefined operational output torque window Wfor the auxiliary brake system arranged upstream of the transmission arrangement is shown. Said auxiliary brake system may be anyone of the auxiliary brake systems 11 -13 shown in Figure 2. The predefined operational output torque window W represents the window within which the auxiliary brake system should be operated e.g., for ensuring sufficient precision during control thereof. On the right hand side, a determined desired brake torque operational range R_SC for slip control is shown. The determined desired brake torque operational range R_SC for slip control is defined by an upper limit UL and a lower limit LL. Moreover, on the right hand side, the available brake torque operational range at the one or more drive wheels which would result from different gear selections (in the figure denominated A-D) is shown in relation to the determined desired brake torque operational range R_SC. From the figure, it can be shown that gear selection B would result in an available brake torque operational range, at the one or more drive wheels, which falls within the determined desired brake torque operational range R_SC for slip control. Moreover, it can be seen that, although each of the gear selections C and D provides a partial overlap with the determined desired brake torque operational range R_SC, these gears would not enable a reduction of brake torque transmitted to the drive wheels as the gear selection B which provides a broader overlap with the determined desired brake torque operational range R_SC. It can also be seen that gear selection A would result in an unduly low maximum possible braking torque for not having a smaller overlap with the determined desired brake torque operational range R_SC compared to gear selection B. This would thus mean that gear selection A would not enable braking of the vehicle to the same extent as gear selection B. Thus, when the adjusted gear selection strategy is activated, gear selection B would be made.

[0068] Figure 5 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.

[0069] 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 an interruption controller (not depicted). The non-volatile memory 520 has also a second memory element 540. There is provided a computer program P that comprises instructions for controlling a vehicle. Said vehicle comprises a powertrain being configured to transmit torque to one or more drive wheels of the vehicle, said powertrain comprising a transmission arrangement and an auxiliary brake system arranged upstream of the transmission arrangement. The computer program comprises instructions for, when slip control of the vehicle is initiated and / or actively performed, determining a desired brake torque operational range for slip control of the vehicle. The computer program further comprises instructions for, when the vehicle is braked, or about to be braked, using the auxiliary brake system, activating an adjusted gear selection strategy for the transmission arrangement so that the transmission arrangement is controlled in accordance with the adjusted gear selection strategy. Said adjusted gear selection strategy comprises selecting a gear, from a plurality of possible gears of the transmission arrangement, that, for a predefined operational output torque window for the auxiliary brake system, results in an available brake torque operational range at the one or more drive wheels that falls within, and / or provides a broadest overlap with, the determined desired brake torque operational range for slip control.

[0070] The 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.

[0071] 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.

[0072] 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.

[0073] 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. 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

[0074] 550. When the device 500 runs the program, methods herein described are executed.

Claims

CLAIMS1 . A method, performed by a control arrangement (100), for controlling a vehicle (1 ), the vehicle (1) comprising a powertrain (2) being configured to transmit torque to one or more drive wheels (7) of the vehicle (1), said powertrain (2) comprising: a transmission arrangement (4), and an auxiliary brake system (11 , 12, 13) arranged upstream of the transmission arrangement (4), the method comprising the following steps: when slip control of the vehicle (1) is initiated and / or actively performed, determining (S102) a desired brake torque operational range for slip control of the vehicle (1 ), and when the vehicle (1 ) is braked, or is about to be braked, using the auxiliary brake system (11 , 12, 13), activating (S104) an adjusted gear selection strategy for the transmission arrangement (4) so that the transmission arrangement (4) is controlled in accordance with the adjusted gear selection strategy, wherein said adjusted gear selection strategy comprises selecting a gear, from a plurality of possible gears of the transmission arrangement (4), that, for a predefined operational output torque window (W) for the auxiliary brake system (11 , 12, 13), results in an available brake torque operational range at the one or more drive wheels (7) that falls within, and / or provides a broadest overlap with, the determined desired brake torque operational range (R_SC) for slip control.

2. The method according to claim 1 , wherein the step of determining a desired brake torque operational range for slip control of the vehicle (1) comprises determining an upper limit for the desired brake torque operational range that allows maximum braking of the vehicle (1 ) without causing locking of the one or more drive wheels (7).

3. The method according to any one of claims 1 or 2, further comprising a step of initiating (S101 ) slip control in response to a determination that a wheel slip of at least one of the one or more drive wheels (7) is above a threshold wheel slip and / or a derivative of wheel slip of at least one of the one or more drive wheels (7) is above a threshold derivative.

4. The method according to any one of the preceding claims, further comprising a step of:when active slip control of the vehicle (1 ) is terminated, deactivating (S106) the adjusted gear selection strategy so that the transmission arrangement (4) is controlled in accordance with a default gear selection strategy.

5. The method according to any one of the preceding claims, further comprising a step of: in response to a determination that the vehicle (1) no longer is braked by the auxiliary brake system (11 , 12, 13), deactivating (S106) the adjusted gear selection strategy so that the transmission arrangement (4) is controlled in accordance with a default gear selection strategy.

6. A control arrangement (100) configured to control a vehicle (1 ), the vehicle (1) comprising a powertrain (2) being configured to transmit torque to one or more drive wheels (7) of the vehicle (1), said powertrain (2) comprising: a transmission arrangement (4), and an auxiliary brake system (11 , 12, 13) arranged upstream of the transmission arrangement (4), the control arrangement (100) being configured to: when slip control of the vehicle (1) is initiated and / or actively performed, determine a desired brake torque operational range for slip control of the vehicle (1 ), and when the vehicle (1 ) is braked, or about to be braked, using the auxiliary brake system (11 , 12, 13), activate an adjusted gear selection strategy for the transmission arrangement (4) so that the transmission arrangement (4) is controlled in accordance with the adjusted gear selection strategy, wherein said adjusted gear selection strategy comprises selecting a gear, from a plurality of possible gears of the transmission arrangement (4), that, for a predefined operational output torque window for the auxiliary brake system (11 , 12, 13), results in an available brake torque operational range at the one or more drive wheels (7) that falls within, and / or provides a broadest overlap with, the determined desired brake torque operational range for slip control.

7. The control arrangement (100) according to claim 6, wherein in the control arrangement (100) is configured to determine an upper limit of the desired brake torque operational range for slip control of the vehicle (1) sufficient for allowing maximum braking of the vehicle (1 ) without causing locking of the one or more drive wheels (7).

8. The control arrangement (100) according to any one of claims 6 or 7, further configured to perform slip control of the vehicle (1 ).

9. The control arrangement (100) according to any one of claims 6 to 8, further configured to deactivate the adjusted gear selection strategy, so that the transmission arrangement (4) is controlled in accordance with a default gear selection strategy, when it is determined that active slip control of the vehicle (1) is terminated and / or when it is determined that the vehicle (1 ) is no longer braked by the auxiliary brake system (11 , 12, 13).

10. A computer program comprising instructions which, when executed by the control arrangement (100) according to any one of claims 6 to 9, causes the control arrangement (100) to carry out the method according to any one of claims 1 to 5.11 . A computer-readable medium having stored thereon the computer program according to claim 10.

12. Avehicle (1) comprising: a control arrangement (100) according to any one of claims 6 to 9, and a powertrain (2) configured to transmit torque to one or more drive wheels (7) of the vehicle (1), said powertrain (2) comprising a transmission arrangement (4) and an auxiliary brake system (11 , 12, 13) arranged upstream of the transmission arrangement (4).

13. The vehicle (1) according to claim 12, wherein the auxiliary brake system (11 , 12, 13) is an engine brake system, a regenerative brake system, or a pre-transmission retarder.

14. The vehicle (1) according to claim 13, wherein the engine brake system comprises an exhaust brake system, a compression release brake system, a variable valve brake system, and / or a variable vane brake system.

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