SE2251013A1

SE2251013A1 - Control device and method for reducing possible side pull of a vehicle

Info

Publication number: SE2251013A1
Application number: SE2251013A
Authority: SE
Inventors: Emil Lundgren; Frederik Laanen
Original assignee: Scania Cv Ab
Priority date: 2022-09-01
Filing date: 2022-09-01
Publication date: 2024-03-02
Also published as: DE102023118381A1

Abstract

A control device (100) and a method for reducing possible side pull of a vehicle (1), the vehicle (1) comprising a steerable tag axle (12). The method comprises, in response to either a driver-initiated request for compensation of side pull of the vehicle (1) or an indication of unintentional side pull of the vehicle (1), controlling (S104, S108, S110, S207) the steerable tag axle (12) to adjust a predefined steering angle (or) of at least one of the tag axle wheels (6) of the steerable tag axle (12) so as to at least partly compensate for side pull of the vehicle (1), wherein said predefined steering angle corresponds to a neutral position of said at least one of the tag axle wheels (6).

Description

CONTROL DEVICE AND METHOD FOR REDUCING POSSIBLE SIDE PULL OF A VEHICLE TECHNICAL FIELD The present disclosure relates in general to a method for reducing possible side pull of a vehicle. The present disclosure further relates in general to a control device configured to reduce possible side pull of a vehicle. Moreover, the present disclosure relates in general to a computer program as well as a computer readable medium. The present disclosure also relates in general to a vehicle.

BACKGROUND A vehicle may sometimes have a tendency to unintentionally deviate from travelling straight ahead (i.e. in the direction of the longitudinal axis of the vehicle) in the absence of for example any driver operation of the steering wheel or active compensation by steering system for the front wheels of III the vehicle. This tendency frequently being described by the term "side pul .Vehicles may suffer from side pull due to several reasons. Examples of such reasons include, but are not limited to, road banking (i.e. transverse inclination of the road), side wind, uneven and/or worn tires, uneven loading conditions of the vehicle or due to misalignment in the axles/wheels of the vehicle. Side pull of a vehicle may for example be uncomfortable or disturbing to a driver of the vehicle, who has to actively compensate for the side pull by exerting a force on the steering wheel to keep the vehicle travelling straight-ahead. Side pull of a vehicle can also result in uneven wear of the tires and/or increased energy consumption of the vehicle, as well as in worst case scenario present a safety risk.

Vehicles adapted to transport heavy loads (such as trucks, semis, buses, dumpers, haulers and trailers) often exert large pressure on the ground as a result of their weight, especially when transporting a load. To handle this pressure, such vehicles may often comprise one or more tag axles, each comprising a pair of tag axle wheels. This decreases the pressure each wheel of the vehicle has to transfer to the ground. A tag axle is an unpowered, i.e. non-driven, axle, and may be arranged at various positions in the vehicle. ln order to improve maneuverability of the vehicle, the tag axle may be a steerable tag axle. This means that the tag axle wheels may be steered. Thereby, it is for example possible to obtain a more appropriate turning radius of the vehicle. Furthermore, the ability to steer tag axle wheels may also reduce the tire wear of the tag axle wheels. Steering of the tag axle wheels may often be performed in dependence of the steering of the front wheels of the vehicle.

WO 2014/163560 A1 discloses one example of a system for steering at least one unpowered wheeled tag axle of a vehicle. SE 541031 C2 discloses an example of an articulated vehicle comprising a steerable tag axle, wherein controlling of steering of the tag axle may be dependent of the articulation state of the vehicle.

EP 3283351 A1 discloses a method for steering the wheels of a wheeled axle, for example a steered tag axle, of a vehicle. The method addresses the problem of difference in toe-values between the respective wheels resulting from bending of the axle beam of wheeled axle due to heavy load, a situation that may lead to side pull of a vehicle. According to the method, the value of a load applied on the axle beam is compared to stored data of a change in toe-values of the wheels as a function of load applied on the axle beam. The method thereafter comprises calculating a length to be assumed by a power means, configured to control the direction of the wheels, for obtaining the same toe- value for the wheels, and controlling the power means to assume said length.

SUMMARY The object of the present invention is to at least reduce possible side pull of a vehicle, noticed by a driver or a vehicle system while the vehicle is in motion, even if the reason for said possible side pull of the vehicle may be unknown or if the cause of the side pull cannot be easily fixed.

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

The present disclosure provides a method, performed by a control device, for reducing possible side pull of a vehicle. The vehicle comprises a steerable tag axle comprising tag axle wheels. The method comprises a step of, in response to either a driver-initiated request for compensation of side pull of the vehicle or an indication of unintentional side pull of the vehicle, said indication generated while the vehicle is in motion, controlling the steerable tag axle to adjust a predefined steering angle of at least one of the tag axle wheels so as to at least partly compensate for side pull of the vehicle. Said predefined steering angle corresponds to a neutral position of said at least one of the tag axle wheels.

By means of the herein described method, side pull can be counteracted on a vehicle comprising a steerable tag axle regardless of the actual reason for the vehicle unintentionally pulling to one side while in motion. lmportantly, the present method enables counteracting side pull of the vehicle regardless of the alignment of the other axles of the vehicle. Possible misalignment of the axles of a vehicle is not something which may be easily fixed without the vehicle being taken out of operation for an extended period of time, which may be costly for an owner of the vehicle (especially in the case of a commercial heavy vehicle). Thus, the present method has the advantage of enabling a reduction of side pull of the vehicle even if the reason therefore would be a possible misalignment of the other axles, such as the front axle and/or drive axle, of the vehicle without taking the vehicle out of its planned operation.

Reducing (including overcoming) side pull of the vehicle may improve the comfort of a possible driver of the vehicle, reduce undue wear of the tires/axles and related components of the vehicle, as well as improve safety in the operation of the vehicle. Moreover, in some situations, a reduction of side pull may reduce the energy consumption of the vehicle and thereby the operational economy thereof. Furthermore, in the case of an autonomous vehicle, the present method may facilitate and/or simplify the control strategy for keeping the vehicle travelling straight ahead.

The step of controlling the steerable tag axle to adjust the predefined steering angle of at least one of the tag axle wheels may be performed while the vehicle is stationary or while the vehicle is in motion with a vehicle speed lower than a predetermined vehicle speed threshold. This may improve the safety of the vehicle while performing the step of controlling the steerable tag axle, especially for certain vehicle configurations.

The method may further comprise a step of determining a first adjusted predefined steering angle of the at least one of the tag axle wheels needed to overcome side pull of the vehicle. When the method comprises said step of determining said first adjusted predefined steering angle, the step of controlling the steerable tag axle to adjust the predefined steering angle of the at least one of the tag axle wheels may comprise, when the determined first adjusted predefined steering angle of the at least one of the tag axle wheels is within a predetermined acceptable range, controlling the steerable tag axle to achieve said first adjusted predefined steering angle of the at least one of the tag axle wheels. This has the advantage of minimizing possible side pull of the vehicle as soon as possible without compromising the safety of the vehicle.

The method may further comprise a step of determining a second adjusted predefined steering angle of the at least one of the tag axle wheel capable of partly compensating for side pull of the vehicle. ln such a case, the step of controlling the steerable tag axle to adjust the predefined steering angle of the at least one of the tag axle wheels may comprise controlling the steerable tag axle to achieve said second adjusted predefined steering angle of the at least one of the tag axle wheels. Thereby, a reliable reduction of the side pull of the vehicle may be achieved without compromising the safety of the vehicle.

The method may further comprise, after the step of controlling the steerable tag axle to adjust the predefined steering angle of the at least one of the tag axle wheels and while the vehicle is in motion, determining whether the vehicle is unintentionally pulling to one side, and, in response to a determination that the vehicle is unintentionally pulling to one side, iterating the step of controlling the steerable tag axle to adjust a predefined steering angle of at least one of the tag axle wheels so as to at least partly compensate for side pull of the vehicle. Thereby, possible side pull of the vehicle may be reduced further. |teration of the step of controlling the steerable tag axle to adjust a predefined steering angle of at least one of the tag axle wheels so as to at least partly compensate for side pull of the vehicle may be performed until it is determined that a further iteration would result in a predefined steering angle outside of a predetermined acceptable range. Thereby, it is ensured that possible side pull is reduced as much as possible without compromising the safety of the vehicle.

The method may further comprise a step of determining said indication of unintentional side pull of the vehicle based on data relating to road inclination, lateral acceleration, yaw velocity, vehicle speed, one or more parameters from steering system of a front axle of the vehicle, and/or one or more current control parameters of the steerable tag axle. Thereby, a reliable determination of unintentional side pull may be achieved while the vehicle is in motion.

The data, used for determining the indication of unintentional side pull of the vehicle, may be obtained from onboard sensors of the vehicle. Thereby, a more reliable determination of unintentional side pull of the vehicle may be made.

The method may further comprise, in response to a driver-initiated command for adjustment of at least one control parameter of the steerable tag axle, determining an effect of the commanded adjustment of the at least one control parameter with regard to possible side pull of the vehicle. When the commanded adjustment of the at least one control parameter is determined to affect possible side pull of the vehicle, the method may comprise presenting, via an interface, the determined effect with regard to possible side pull of the vehicle to a driver of the vehicle and enabling the driver to confirm the command for adjustment of the at least one control parameter. ln such a case, the method also comprises, when the driver (via the interface) confirms the command for adjustment of the at least one control parameter, determining that the driver-initiated request for compensation of side pull of the vehicle has been generated. Thereby, it may for example be avoided that a driver unintentionally initiates a change of control parameters of the steerable tag axle which could risk causing side pull of the vehicle.

The present disclosure also provides a computer program comprising instructions which, when executed by a control device, cause the control device to carry out the method as described above.

The present disclosure also provides a computer-readable medium comprising instructions which, when executed by a control device, cause the control device to carry out the method as described above.

Furthermore, the present disclosure provides a control device configured to reduce possible side pull of a vehicle, said vehicle comprising a steerable tag axle comprising tag axle wheels. The control device is configured to, in response to either a driver-initiated request for compensation of side pull of the vehicle or an indication of unintentional side pull of the vehicle, said indication generated while the vehicle is in motion, control the steerable tag axle to adjust a predefined steering angle of at least one of the tag axle wheels so as to at least partly compensate for side pull of the vehicle. Said predefined steering angle corresponds to a neutral position of said at least one of the tag axle wheels.

The control device provides the same advantages as described above with regard to the corresponding method for reducing possible side pull of a vehicle.

The control device may further be configured to determine a first adjusted predefined steering angle of the at least one of the tag axle wheels needed to overcome side pull of the vehicle, and when the determined first adjusted predefined steering angle of the at least one of the tag axle wheels is within a predetermined acceptable range, control the steerable tag axle to achieve said first adjusted predefined steering angle of the at least one of the tag axle wheels.

Moreover, the control device may further be configured to determine said indication of unintentional side pull of the vehicle based on data relating to road inclination, lateral acceleration, yaw velocity, vehicle speed, one or more parameters from steering system of a front axle of the vehicle, and/or one or more current control parameters of the steerable tag axle.

The present disclosure also provides a vehicle comprising a steerable tag axle and the control device described above. The vehicle may be a heavy vehicle, such as a bus, or truck, but is not limited thereto. Furthermore, the vehicle may be a vehicle partly or fully operated by a driver or be a fully autonomous vehicle.

BRIEF DESCRIPTION OF DRAWINGS Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. 7 schematically illustrates a side view of a first example of a vehicle, represents a top view schematically illustrating the wheel axes of a vehicle, such as the vehicle shown in Figure 1, when the tag axle wheels are steered and are in a position other than the neutral position, schematically illustrates an example of a steerable tag axle, represents a flowchart schematically illustrating a first exemplifying embodiment of the method for reducing possible side pull of a vehicle according to the present disclosure, represents a flowchart schematically illustrating a second exemplifying embodiment of the method for reducing possible side pull of a vehicle according to the present disclosure, represents a flowchart schematically illustrating a third exemplifying embodiment of the method for reducing possible side pull of a vehicle according to the present disclosure, and schematically illustrates an exemplifying embodiment of a device comprising, consisting or comprised in a control device configured to reduce possible side pull of a vehicle according to the present disclosure.

DETAILED DESCRIPTION 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. ln the present disclosure, a steered or steerable tag axle should be considered to mean to comprise the tag axle as such, including its tag axle wheels (at least when fitted in the vehicle), as well as the tag axle steering system configured to steer the tag axle wheels of said tag axle. ln the present disclosure, the term "steering angle" is used to describe the angle between an axis parallel to the longitudinal axis of the vehicle and the line of intersection of the wheel plane and the road surface. The wheel plane is the central plane of the wheel that traverses (more specifically, is substantially perpendicular to) the wheel's axis of rotation. During active steering of a steerable tag axle, the steering angle of the tag axle wheels may typically be changed in dependence of the steering angle of the front wheels of the vehicle to achieve a desired turning radius of the vehicle.

However, the term "predefined steering angle" of a wheel (such as a tag axle wheel) is in the present disclosure used to describe a set control parameter (of steering angle) which is set independently of the changes in steering angle resulting from active steering of the vehicle. The predefined steering angle thus corresponds to the steering angle of a set neutral position of the tag axle wheel(s).

The term "neutral position" of the tag axle wheels is used to describe the position of the tag axle wheels, when the tag axle is fitted in a vehicle, wherein the tag axle wheels are, or at least are considered to be, essentially aligned with a longitudinal axis of the vehicle. Described differently, the neutral position is the desired position of the tag axle wheels when the vehicle should be travelling straight ahead in the direction of the longitudinal axis of the vehicle. Such a position may alternatively be described as a centered position.

The term "driver" is in the present disclosure used to describe a person driving a vehicle and shall be considered to encompass a driver present onboard the vehicle, as well as a person being remote from the vehicle (for example at a remote control center) and controlling the vehicle remotely.

A steerable tag axle can have various configurations, and may for example be hydraulically steered and/or electronically steered. The present disclosure is not limited to any particular configuration of the steerable tag axle, as long as the steering angle of at least one of the tag axle wheels can be actively steered by a steering system. According to one exemplifying embodiment, the steerable tag axle comprises an electrohydraulic tag axle steering system. According to another exemplifying embodiment, the steerable tag axle comprises an electronic tag axle steering system.

The herein described method for reducing possible side pull may be practiced in/on any vehicle comprising a steerable tag axle. The vehicle may be a land-based vehicle, in particular a heavy land- based vehicle. Examples of such a vehicle include, but are not limited to, a truck, a bus, or a trailer. Furthermore, the vehicle may or may not be an articulated vehicle. An articulated vehicle is a vehicle comprising a pivot joint (articulation joint) that allows the vehicle to turn more sharply.

The vehicle may be a vehicle driven by a driver (present onboard or remotely from the vehicle) or a fully autonomous vehicle.

Moreover, the steerable tag axle may be arranged anywhere in the vehicle and may thus be a pusher tag axle or a trailing tag axle. Furthermore, the steerable tag axle may be a raisable tag axle, if desired. lt should also be noted that a vehicle may be fitted with more than one steerable tag axle, if desired.

The present disclosure provides a method for overcoming or at least reducing possible side pull of a vehicle. The method is performed by a control device configured therefore. The vehicle comprises a steerable tag axle comprising tag axle wheels. The method comprises a step of controlling the steerable tag axle to adjust a predefined steering angle of at least one of the tag axle wheels so as to at least partly compensate for side pull of the vehicle. The predefined steering angle corresponds to a neutral position of said at least one of the tag axle wheels. The step of controlling the steerable tag axle to adjust the predefined steering angle is performed in response to an indication of unintentional side pull of the vehicle, said indication generated while the vehicle is in motion. Alternatively, the step of controlling the steerable tag axle to adjust the predefined steering angle is performed in response to a driver-initiated request for compensation of side pull of the vehicle. lt should be noted that it may be appropriate to adjust the predefined steering angle of more than one of the tag axle wheels in order to be able to reduce possible side pull of the vehicle. Thus, the method may alternatively be described to comprise a step of controlling the steerable tag axle to adjust a respective predefined steering angle of one or more of the tag axle wheels so as to at least partly compensate for side pull of the vehicle, said step being performed in response to either a driver-initiated request for compensation of side pull of the vehicle or an indication of unintentional side pull of the vehicle, said indication generated while the vehicle is in motion.

The step of controlling the steerable tag axle to adjust the predefined steering angle of the at least one of the tag axle wheels so as to at least partly compensate for side pull may suitably be made when the tag axle wheels are arranged in their respective neutral position since it facilitates said adjustment. The present method is however not limited thereto, and the adjustment of the predefined steering angle may also be made when the tag axle wheels are arranged in a position deviating somewhat from the neutral position.

The step of controlling the steerable tag axle to adjust the predefined steering angle of the at least one of the tag axle wheels so as to at least partly compensate for side pull may preferably be made while the vehicle is in motion, suitably while the vehicle is intended to travel straight ahead (i.e. when the tag axle wheels are in their respective neutral position). More specifically, said step of controlling the steerable tag axle may suitably be made as soon as an indication of unintentional side pull of the vehicle has been generated or a driver-initiated request for compensation of side pull has been detected. This reduces the time the vehicle is subjected to unintentional side pull. However, depending on e.g. the vehicle configuration (such as number of axles and the arrangement thereof in the vehicle, including where in the vehicle the tag axle is arranged) and the current vehicle load, such an adjustment of the predefined steering angle of a tag axle wheel may in certain cases not be at all vehicle speeds without jeopardizing the safety of the vehicle. Therefore, according to one embodiment of the herein described method, the step of controlling the steerable tag axle to adjust the predefined steering angle of at least one of the tag axle wheels is performed while the vehicle is in motion with a vehicle speed lower than a predetermined vehicle speed threshold. As evident from the above, said predetermined vehicle speed threshold may be dependent of the vehicle configuration and possibly also the current vehicle load. For a heavy vehicle, the predetermined vehicle speed threshold may for example be 50 km/h, 40 km/h, 30 km/h, the present disclosure is however not limited to these exemplified vehicle speed thresholds. ln certain cases, the above described adjustment of the predefined steering angle of a tag axle wheel may even need to be made while the vehicle is stationary for safety reasons. Therefore, the step of controlling the steerable tag axle to adjust the predefined steering angle of the at least one of the tag axle wheels may according to another embodiment be performed while the vehicle is stationary, for example in conjunction with at a temporary stop for loading/unloading cargo or passengers, in conjunction with a short stop at e.g. red light, or in conjunction with a longer stop during which the vehicle is parked.

According to a first embodiment of the herein described method for reducing possible side pull of a vehicle, the step of controlling the steerable tag axle to adjust the predefined steering angle of the at least one of the tag axle wheels may be performed so as to adjust the predefined steering angle in accordance with a preselected (small) adjustment of the predefined steering angle. The value of said preselected adjustment may be stored as such in the control device, or may for example be derived by the control device from data stored in a look-up table elsewhere, said data specifying various preselected adjustments of the predefined steering angle as a function of different circumstances (such as vehicle configuration, vehicle load, direction of side pull, current control parameters of steerable tag axle and/or driving mode of vehicle etc.). Naturally, such a look-up table may alternatively be stored in the control device, if desired. Thereafter, the method may comprise monitoring data of the vehicle from which possible side pull of the vehicle may be determined for the purpose of generating a (new) indication of unintentional side pull of the vehicle while the vehicle is in motion. ln other words, the method may comprise reiterating the step of controlling the steerable tag axle to adjust the predefined steering angle of the at least one of the tag axle wheels until there is no indication of unintentional side pull of the vehicle.

According to a second embodiment, the method may comprise a step of determining a first adjusted predefined steering angle of the at least one of the tag axle wheels needed to overcome side pull of the vehicle. ln case the determined first adjusted predefined steering angle is within a predetermined acceptable range, the step of controlling the steerable tag axle to adjust the predefined steering angle of the least one of the tag axle wheels so as to at least partly compensate for side pull of the vehicle may comprise controlling the steerable tag axle to achieve said first adjusted predefined steering angle of the at least one of the tag axle wheels. The predetermined acceptable range is herein intended to mean a predetermined range of adjustment of the predefined steering angle and/or a predefined range of the predefined steering angle within which an adjustment of the predefined steering angle may be made without compromising the safety of the vehicle and thereby acceptable.

By controlling the steerable tag axle so as to achieve the determined first adjusted predefined steering angle if it is within the predetermined acceptable range, it is possible to as soon as possible minimize possible side pull of the vehicle without compromising safety of the vehicle. However, 11 compared to the first embodiment wherein the adjustment of the predefined steering angle is made in accordance with a preselected adjustment, the method according to the second embodiment may require more computing efforts for the purpose of determining the first adjusted predefined steering angle since this is typically made by calculation based on current data relating to the vehicle and its operation.

The above mentioned predetermined acceptable range may typically be a range dependent of vehicle configuration (including where in the vehicle the tag axle is arranged) and/or vehicle load. The predetermined acceptable range may also in some cases be dependent of other factors, such as weather condition (e.g. rain, snow or icy road). As an illustrative non-limiting example, the predetermined acceptable range may for example be i 1° (corresponding to about 17.5 mm/m) of the current predefined steering angle or i 1° of a default predefined steering angle. ln case the determined first adjusted predefined steering angle of the at least one of the tag axle wheels is not within the predetermined acceptable range, the method may comprise a step of determining a second adjusted predefined steering angle of the at least one of the tag axle wheels capable of partly compensating for side pull of the vehicle. Such a determination of the second adjusted predefined steering angle may suitably be made by calculation based on current data relating to the vehicle and its operation. Thereafter, the step of controlling the steerable tag axle to adjust the predefined steering angle of the at least one of the tag axle wheels comprises controlling the steerable tag axle to achieve said second adjusted predefined steering angle of the at least one of the tag axle wheels. lt should here be noted that adjustment of the current predefined steering angle of the at least one of the tag axle wheels to the determined second adjusted predefined steering angle will entail a smaller adjustment compared to a case of adjusting to the first adjusted predefined steering angle.

According to one alternative to the above described first embodiment, wherein the adjustment of the predefined steering angle is made in accordance with a preselected adjustment, the herein described method may instead comprise determining a second adjusted predefined steering angle of the at least one of the tag axle wheels capable of partly compensating for side pull of the vehicle. This would correspond to the above described second embodiment except for omitting the determination of the first adjusted steering angle needed to overcome side pull of the vehicle and hence also the possibility for controlling the steerable tag axle to achieve such a first adjusted steering angle. 12 The herein described method may further comprise (irrespectively of embodiment), after the step of controlling the steerable tag axle to adjust the predefined steering angle of the at least one of the tag axle wheels and while the vehicle is in motion, a step of determining whether the vehicle is unintentionally pulling to one side. ln other words, the method may comprise determining whether the vehicle is still pulling to one side or even if the adjustment of the predefined steering angle has resulted in the vehicle now pulling to the other side. ln case it is determined that the vehicle is unintentionally pulling to one side (whichever side that may be), the method may comprise reiterating the step of controlling the steerable tag axle to adjust the predefined steering angle of at least one of the tag axle wheels so as to at least partly compensate for said side pull. Said step of controlling the steerable tag axle to adjust the predefined steering angle may be iterated until it is determined that the problem of side pull has been overcome or until it is determined that a further iteration would result in a predefined steering angle outside of the above described predetermined acceptable range.

The method according to the present disclosure may further comprise a step of, while the vehicle is in motion, monitoring data relating to the vehicle and its operation and/or data relating to the road on which the vehicle is travelling for the purpose of, when relevant, generating an indication of unintentional side pull of the vehicle determined based on said data. Alternatively, the control device may be configured to obtain information of such a generated indication of unintentional side pull of the vehicle from another control system.

An indication of unintentional side pull of the vehicle may be determined based on data relating to at least two parameters selected from the group comprising road inclination, lateral acceleration of the vehicle, yaw velocity, vehicle speed, one or more parameters obtained from a steering system of a front axle of the vehicle, one or more current control parameters of the steerable tag axle, and/or geographical positioning data of the vehicle in combination with map data. Examples of parameters obtained from a steering system of a front axle may for example include steering wheel angle, steering wheel torque, or torque measured on an input shaft of steering gear. Examples of current control parameters of the steerable tag axle may for example include data regarding steering mode of the steerable tag axle (for example if the tag axle wheels currently are actively steered, in caster steer mode or in a locked mode in a neutral position), current steering angle of the tag axle wheels, and/or condition/position of a power means configured to control the steering angle of the tag axle wheels. Merely as an illustrative example, an indication of unintentional side pull of the vehicle may be determined in a case where it is noted that the driver is constantly exerting a torque on the steering wheel (i.e. a parameter obtained from a steering system of a front axle) to one direction in 13 order to keep the vehicle in a straight line (i.e. no yaw velocity) on a level road. ln such a case, it may be determined that the vehicle is travelling on a level road by usage of onboard sensor(s) or by data relating to the vehicle's geographical position (obtained for example by GPS) in combination with map data (including topographical data).

Suitably, the above mentioned data used for determining an indication of unintentional side pull of the vehicle may be obtained from onboard sensors of the vehicle.

As discussed above, the step of controlling the steerable tag axle to adjust a predefined steering angle of at least one of the tag axle wheels so as to at least partly compensate for side pull of the vehicle may be performed in response to a driver-initiated request for compensation of side pull of the vehicle. ln such a case, the method may comprise a step of, in response to a driver-initiated command for adjustment of at least one control parameter of the steerable tag axle, determining an effect of the commanded adjustment of the at least one control parameter with regard to possible side pull of the vehicle. Thereafter, the method may comprise a step of, when the commanded adjustment is determined to affect possible side pull of the vehicle, presenting the determined effect with regard to possible side pull of the vehicle to a driver of the vehicle by means of an interface therefore and enabling the driver to confirm the command for adjustment of the at least one control parameter of the steerable tag axle (after having been presented with the determined effect). According to one alternative, the determined effect is only presented to the driver in case it would have a negative effect on side pull of the vehicle, i.e. it may increase side pull of the vehicle. Thereafter, the method comprises a step of, when the driver via said interface confirms the command for adjustment of the at least one control parameter, determining that the driver-initiated request for compensation of side pull of the vehicle has been generated. lf desired, the method may further comprise a step of, in case it is determined that the driver- initiated command for adjustment of at least one control parameter of the steerable tag axle would have a negative effect on side pull of the vehicle in case if it is executed, determining a modified command for adjustment of the at least one control parameter which would avoid side pull of the vehicle or at least result in less side pull of the vehicle. Thereafter, the method may comprise a step of proposing said determined modified command and optionally the difference in effect with regard to side pull of the vehicle, via the interface, to the driver of the vehicle and allowing the driver to select between the driver-initiated command and the determined modified command. The selection made by the driver may thereafter be determined to constitute the driver-initiated request for compensation of side pull of the vehicle. 14 The performance of the method for reducing possible side pull of a vehicle as disclosed herein may be governed by programmed instructions. These programmed instructions typically take the form of a computer program which, when executed in or by a control device, causes the control device to effect desired forms of control action. Such instructions may typically be stored on a computer- readable medium.

Furthermore, the present disclosure provides a control device configured to perform the above- described method for reducing possible side pull of a vehicle. The control device may be configured to perform any one of the steps of the method for reducing possible side pull of a vehicle as described herein.

More specifically, the present disclosure provides a control device configured to reduce possible side pull of a vehicle, said vehicle comprising a steerable tag axle comprising tag axle wheels. The control device is configured to, in response to either a driver-initiated request for compensation of side pull of the vehicle or an indication of unintentional side pull of the vehicle, said indication generated while the vehicle is in motion, control the steerable tag axle to adjust a predefined steering angle of at least one of the tag axle wheels so as to at least partly compensate for side pull of the vehicle. Said predefined steering angle corresponds to a neutral position of said at least one of the tag axle wheels.

The control device may comprise one or more control units. ln case the control device comprises a plurality of control units, each control unit may be configured to control a certain function or a certain function may be divided between different control units. The control device may be arranged in the vehicle, and thus be a part of the vehicle. The control device may be a part of the steerable tag axle as such, for example be partly or fully incorporated into the steering system of the steerable tag axle. Alternatively, the control device may be separate from the steerable tag axle but configured to communicate therewith for the purpose of performing the herein described method.

Figure 1 schematically illustrates a side view of an example of a vehicle 1, here illustrated as a truck. The vehicle 1 comprises drive wheels 2, i.e. powered wheels. The drive wheels 2 may typically be non-steered wheels, but may alternatively be steered wheels. Furthermore, the vehicle 1 comprises front wheels 4, which are steered wheels. The vehicle 1 further comprises a front axle steering system 10 configured to control the steering of the front wheels 4. The vehicle 1 may further comprise a steering wheel 8. The steering wheel 8 may be operated by a driver of the vehicle 1 for the purpose of steering the vehicle 1.

The illustrated vehicle 1 further comprises a tag axle with associated tag axle wheels 6. The tag axle is not a part of the powertrain, and the tag axle wheels 6 are thus non-driven wheels. The tag axle is here shown to be arranged behind the driven wheels 2 as seen in the primary direction of travel of the vehicle 1, which is illustrated by the arrow M in the figure. lt should however be noted that a tag axle may be arranged at other positions in the vehicle as long as it is behind the front axle with its associated front wheels 4. The tag axle wheels 6 may be steerable via a tag axle steering system 20. The tag axle steering system 20 may be configured to steer the tag axle wheels 6 in dependence of information obtained from the front axle steering system 10. The vehicle 1 may further comprise a control device 100 configured to reduce possible side pull of the vehicle 1.

Figure 2 represents a top view schematically illustrating the wheel axes of a vehicle, such as the vehicle 1 shown in Figure 1. Figure 2 shows a situation when the tag axle wheels are steered and are in a position other than the neutral position. ln other words, Figure 2 shows a situation when the vehicle 1 is turning and the tag axle is actively steered. The vehicle 1 comprises a driven axle 3, with associated driven wheels 2. The figure illustrates two parallel drive wheels 2 at each end of the driven axle 3, but the present disclosure is not limited thereto. The driven axle 3 is arranged behind a front axle 5 as seen in the primary direction of travel M of the vehicle (i.e. in the direction of the longitudinal axis A of the vehicle). The vehicle 1 further comprises a steerable tag axle, here illustrated by a tag axle beam 7 with associated tag axle wheels 6. Figure 2 further illustrates the steering angle ot of one of the tag axle wheels 6. The steering angle ot is the angle between an axis B, parallel to the longitudinal axis A of the vehicle, and line of intersection of the wheel plane WP and the road surface. ln contrast to the situation illustrated in Figure 2, if the tag axle wheels are in a neutral position, the tag axle wheels are arranged in a position which is suitable when the vehicle is intended to travel in a straight ahead direction, i.e. in the primary direction of travel M of the vehicle 1. ln the neutral position, the wheel planes WP of the tag axle wheels 6 are essentially aligned with the longitudinal axis A of the vehicle 1 but typically with a possible small offset from zero in steering angle. Such an offset may typically be a few mm/m, such as i 5 mm/m. The steering angle ot of the tag axle wheels 6 in the neutral position is in the present disclosure denominated predetermined steering angle since it constitutes a set control parameter of the steerable tag axle. 16 Steerable tag axles are typically controlled to lock the tag axle wheels in the neutral position, i.e. at the predetermined steering angle, when the vehicle speed is above for example 30 km/h or 40 km/h (depending on vehicle configuration) for reasons of safety in operation of the vehicle, vehicle stability and/or due to legislative requirements.

Figure 3 schematically illustrates an example of a previously known steerable tag axle 12. The steerable tag axle 12 comprises tag axle wheels 6 (at least when fitted into a vehicle) arranged at opposite ends of a tag axle beam 7. The steerable tag axle 12 further comprises a power cylinder 14 mechanically connected to the to the tag axle beam 7. Moreover, the steerable tag axle 12 comprises a track rod 18 arranged substantially parallel to the tag axle beam 7. The track rod 18 is at opposite ends thereof connected to a respective rod arm 19 via a first hinge device 19a, for example a ball joint. Each of the rod arms 19 is in turn connected to an axle shaft (not shown) of a respective tag axle wheel 6.

The power cylinder 14 comprises a piston 15a with an associated piston rod 15b. The piston rod 15b is, via a second hinge device 16a, such as a ball joint, connected to a link arm 16. The link arm 16 is, at the end opposing the second hinge device 16a, connected to the axle shaft (not shown) of one of the tag axle wheels 6. The power cylinder 14 is fluidly connected to a hydraulic control unit 13 configured to convey pressurized hydraulic fluid to the power cylinder 14 for the purpose of moving the piston 15a inside the power cylinder 14. The hydraulic control unit 13 may be a constituent component of the tag axle steering system 20 shown in Figure 1.

Movement of the piston 15a inside the power cylinder 14 will via the link arm alter the alignment of the tag axle wheel 6 to which it is connected relative to the longitudinal axis of the vehicle. Said alteration of the tag axle wheel will also cause an alteration of the alignment of the tag axle wheel arranged at the opposite end of the tag axle beam due as a result of movement of the respective rod arms 19 via the track rod 18. Thus, the power cylinder 14 acts indirectly between the tag axle beam 7 and the rod arm 19 connected to the track rod 18 since the link arm 16 and the rod arm 19 are connected to the axle shaft of the same tag axle wheel 6 and will follow this as it turns. Thus, movement of the piston 15a may alter the steering angle of the respective tag axle wheels 6. lt should here be noted that the present disclosure is not limited to a vehicle comprising the exemplified steerable tag axle shown in Figure 3, but may be practiced on a vehicle comprising a steerable tag axle having any type of configuration where the steering angle of at least one of the tag axle wheels can be actively steered by a steering system. By way of example only, the steerable tag 17 axle need not comprise the track rod 18 with the associated rod arms 19 shown in Figure 2, but instead comprise two power cylinders 14, each mechanically connected to the tag axle beam 7. ln such a case, each of the power cylinders may be configured to alter the alignment of a respective one of the tag axle wheels 6. As another example, the steerable tag axle need not comprise any hydraulic control unit but may be entirely electronically steered.

Figure 4 represents a flowchart schematically illustrating a first exemplifying embodiment of the herein described method for reducing possible side pull of a vehicle. Optional steps are illustrated by dashed lines in the figure.

The method may comprise a step S101 of, while the vehicle is in motion, monitoring data relating to the vehicle and its operation and optionally also data relating to the road on which the vehicle is travelling for the purpose of, when relevant, generating an indication of unintentional side pull of the vehicle determined based on said data.

The method further comprises a step S102 of determining whether an indication of unintentional side pull of the vehicle has been generated while the vehicle is in motion. lf no such indication has been generated, the method may be returned to start. ln case an indication of unintentional side pull of the vehicle has been generated while the vehicle is in motion, the method proceeds to a subsequent step.

The method may comprise a step S103 of determining whether the vehicle speed is below a predetermined vehicle speed threshold. ln case the vehicle speed is not below the predetermined vehicle speed threshold, the method may be reverted to prior to step S103. However, if the vehicle speed is below the predetermined vehicle speed threshold, the method proceeds to step S104.

The method comprises a step S104 of, when there is an indication of unintentional side pull of the vehicle as determined in step S102, of controlling the steerable tag axle to adjust a predefined steering angle of at least one of the tag axle wheels so as to at least partly compensate for side pull of the vehicle. The predefined steering angle is the steering angle corresponding to the selected neutral position of the at least one tag axle wheel. The predefined steering angle may for example be adjusted in accordance with a preselected small adjustment of the steering angle. The method is after step S104 reverted to start. 18 The method according to the first exemplifying embodiment is thus based on, when there is an indication of side pull of the vehicle while the vehicle is in motion, making a small adjustment of the predefined steering angle and allowing the method to revert back to start to determine if the vehicle still experiences unintentional side pull.

Albeit not illustrated in the figure, the method may be terminated for example when the ignition of the vehicle is turned off or when interrupted by a request therefore.

Figure 5 represents a flowchart schematically illustrating a second exemplifying embodiment of the herein described method for reducing possible side pull of a vehicle. Optional steps are illustrated by dashed lines in the figure.

The optional step S101 and step S102 of the second exemplifying embodiment of the method corresponds to the first two steps of the first exemplifying embodiment illustrated in Figure 4.

However, the method according to the second exemplifying embodiment comprises a step S105 of, when it has been determined in step S102 that an indication of unintentional side pull of the vehicle has been generated while the vehicle is in motion, determining a first adjusted predefined steering angle of at least one of the tag axle wheels needed to overcome the (unintentional) side pull of the vehicle.

Thereafter, the method may comprise a step S106 of determining whether the first adjusted predefined steering angle is within a predetermined acceptable range of the predefined steering angle. The predetermined acceptable range may typically be a range dependent of vehicle configuration (including where in the vehicle the tag axle is arranged) and/or vehicle load. The predetermined acceptable range may also in some cases be dependent of other factors, such as weather condition (e.g. rain, snow or icy road). ln case the first adjusted predefined steering angle is within the predefined acceptable range of the predefined steering angle, the method may proceed to a step S107 of determining whether the vehicle speed is below a predetermined vehicle speed threshold. ln case the vehicle speed is not below the predetermined vehicle speed threshold, the method may be reverted to e.g. after step S105. 19 Moreover, in case the first adjusted predefined steering is within the predefined acceptable range of the predefined steering angle (and the vehicle speed is below the predetermined vehicle speed threshold, where applicable), the method comprises a step S108 of controlling the steerable tag axle to achieve said first adjusted predefined steering angle of the at least one of the tag axle wheels. ln other words, the step of controlling the steerable tag axle to adjust the predefined steering angle of the at least one of the tag axle wheels comprises in this situation controlling the steerable tag axle to achieve said first adjusted predefined steering angle. After step S108, the method may be reverted to start as illustrated in the figure, or terminated.

However, in case it is found in step S106 that the first adjusted predefined steering angle is outside of the predefined acceptable range of the predefined steering angle, the method may proceed to a step S109 of determining a second adjusted predefined steering angle of the at least one of the tag axle wheels capable of partly compensating for side pull of the vehicle.

After step S109, the method proceeds to a step S110 of controlling the steerable tag axle to achieve said second adjusted predefined steering angle of the at least one of the tag axle wheels. Albeit not shown in the figure, the method may between steps S109 and S110 comprise a step of determining whether the vehicle speed is below a predetermined vehicle speed threshold, similar to step S107, and step S110 in such a case being performed only if the vehicle speed is below the predetermined vehicle speed threshold. After step S110, the method may be returned to start, as shown in the figure.

Just like the method according to the first exemplifying embodiment, the method according to the second exemplifying embodiment may be terminated for example when the ignition of the vehicle is turned off or when interrupted by a request therefore.

Figure 6 represents a flowchart schematically illustrating a third exemplifying embodiment of the herein described method for reducing possible side pull of a vehicle.

The method according to the third exemplifying embodiment comprises a step S201 of, in response to a driver-initiated command for adjustment of at least one control parameter of the steerable tag axle, determining an effect of the commanded adjustment of the at least one control parameter with regard to possible side pull of the vehicle.

Thereafter, the method comprises a step S202 of determining whether the commanded adjustment would affect side pull of the vehicle. lf the commanded adjustment of the at least one control parameter of the steerable tag axle is determined to not affect side pull of the vehicle, the method may be reverted to start. However, if the commanded adjustment of the at least one control parameter (initiated by the driver), the method proceeds to a step S203 of presenting, via an interface, the determined effect with regard to possible side pull of the vehicle to the driver of the vehicle and enabling the driver to confirm the command for adjustment of the at least one control parameter.

According to one alternative, the effect of the commanded adjustment is presented to the driver irrespectively of whether it is a negative or a positive effect with regard to possible side pull of the vehicle. However, according to another alternative, the effect of the commanded adjustment is only presented to the driver if the commanded adjustment could risk increasing the side pull of the vehicle, i.e. only if it would be negative.

The method thereafter comprises a step S204 of determining whether the driver has confirmed the commanded adjustment of the at least one control parameter of the steerable tag axle after having being presented with the determined effect of the commanded adjustment. lf it is determined that the driver has not confirmed the commanded adjustment, the method is reverted to start. However, if it is determined that the driver has confirmed the commanded adjustment of the at least one control parameter of the steerable tag axle, the method comprises a step S205 of determining that a driver-initiated request for compensation of side pull of the vehicle has been generated.

The method further comprises, after step S205, a step S206 of determining whether the driver- initiated command for adjustment of at least one control parameter of the steerable tag axle comprises a command for adjustment of a predefined steering angle of at least one of the tag axle wheels. lf not, the method may be reverted to start. However, if the driver-initiated command for adjustment comprises a command for adjustment of the predefined steering angle of the at least one of the tag axle wheels, the method proceeds to step S207.

Step S207 comprises, in response to the driver-initiated request for compensation of side pull of the vehicle, controlling the steerable tag axle to adjust the predefined steering angle of the at least one of the tag axle wheels so as to at least partly compensate for side pull of the vehicle, said predefined steering angle corresponding to a neutral position of said at least one of the tag axle wheels. More specifically, the steerable tag axle is controlled so as to adjust the predefined steering angle of the at 21 least one of the tag axle wheels in accordance with the driver-initiated command for adjustment thereof.

Figure 7 schematically illustrates an exemplifying embodiment of a device 500. The control device 100 described above may for example comprise the device 500, consist of the device 500, or be comprised in the device 500.

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 reducing possible side pull of a vehicle, said vehicle comprising a steerable tag axle comprising tag axle wheels. The computer program comprises instructions for, in response to either a driver-initiated request for compensation of side pull of the vehicle or an indication of unintentional side pull of the vehicle, controlling the steerable tag axle to adjust a predefined steering angle of at least one of the tag axle wheels so as to at least partly compensate for side pull of the vehicle. The above mentioned indication of unintentional side pull of the vehicle is an indication generated while the vehicle is in motion. Furthermore, the predefined steering angle corresponds to a neutral position of said at least one of the tag axle wheels.

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.

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.

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 22 510 via a data bus 514. The communication between the constituent components may be implemented by a communication link. A communication link may be a physical connection such as an optoelectronic communication line, or a non-physical connection such as a wireless connection, e.g. a radio link or microwave link.

When data are received on the data port 599, they may be stored temporarily in the second memory element 540. When input data received have been temporarily stored, the data processing unit 510 is prepared to effect code execution as described above.

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

Claims

1.Claims A method, performed by a control device (100), for reducing possible side pull of a vehicle (1), said vehicle (1) comprising a steerable tag axle (12) comprising tag axle wheels (6), the method comprising a step of: in response to either a driver-initiated request for compensation of side pull of the vehicle (1) or an indication of unintentional side pull of the vehicle (1), said indication generated while the vehicle (1) is in motion, controlling (S104, S108, S110, S207) the steerable tag axle (12) to adjust a predefined steering angle of at least one of the tag axle wheels (6) so as to at least partly compensate for side pull of the vehicle (1), said predefined steering angle corresponding to a neutral position of said at least one of the tag axle wheels (6). The method according to claim 1, wherein the step of controlling (S104, S108, S110, S207) the steerable tag axle (12) to adjust the predefined steering angle of at least one of the tag axle wheels (6) is performed while the vehicle (1) is stationary or while the vehicle (1) is in motion with a vehicle speed lower than a predetermined vehicle speed threshold. The method according to any one of claims 1 or 2, further comprising a step of: determining a first adjusted predefined steering angle of the at least one of the tag axle wheels (6) needed to overcome side pull of the vehicle (1), wherein the step of controlling (S104, S108, S110, S207) the steerable tag axle (12) to adjust the predefined steering angle of the at least one of the tag axle wheels (6) comprises, when the determined first adjusted predefined steering angle of the at least one of the tag axle wheels (6) is within a predetermined acceptable range, controlling (S108) the steerable tag axle (12) to achieve said first adjusted predefined steering angle of the at least one of the tag axle wheels (6). The method according to any one of the preceding claims, further comprising a step of: determining a second adjusted predefined steering angle of the at least one of the tag axle wheels (6) capable of partly compensating for side pull of the vehicle (1), wherein the step of controlling (S104, S108, S110, S207) the steerable tag axle (12) to adjust the predefined steering angle of the at least one of the tag axle wheels (6) comprisescontro||ing (S110) the steerable tag axle (12) to achieve said second adjusted predefined steering angle of the at least one of the tag axle wheels (6). The method according to any one of the preceding claims, further comprising: after the step of contro||ing (S104, S108, S110, S207) the steerable tag axle (12) to adjust the predefined steering angle of the at least one of the tag axle wheels (6) and while the vehicle (1) is in motion, determining whether the vehicle (1) is unintentionally pulling to one side, and in response to a determination that the vehicle (1) is unintentionally pulling to one side, iterating the step of contro||ing (S104, S108, S110, S207) the steerable tag axle (12) to adjust a predefined steering angle of at least one of the tag axle wheels (6) so as to at least partly compensate for side pull of the vehicle (1). The method according to claim 5, wherein iterating the step of contro||ing (S104, S108, S110, S207) the steerable tag axle (12) to adjust a predefined steering angle of at least one of the tag axle wheels (6) so as to at least partly compensate for side pull of the vehicle (1) is performed until it is determined that a further iteration would result in a predefined steering angle outside of a predetermined acceptable range. The method according to any one of the preceding claims, further comprising a step of: determining said indication of unintentional side pull of the vehicle (1) based on data relating to road inclination, lateral acceleration, yaw velocity, vehicle speed, one or more parameters from a steering system (10) of a front axle (5) of the vehicle (1), and/or one or more current control parameters of the steerable tag axle (12). The method according to claim 7, wherein said data, used for determining the indication of unintentional side pull of the vehicle (1), is obtained from onboard sensors of the vehicle (1). The method according to any one of the preceding claims, further comprising: in response to a driver-initiated command for adjustment of at least one control parameter of the steerable tag axle (12), determining (S201) an effect of the commanded adjustment of the at least one control parameter with regard to possible side pull of the vehicle (1), when the commanded adjustment of the at least one control parameter is determined to affect possible side pull of the vehicle (1), presenting (S203), via an interface, the determined effect with regard to possible side pull of the vehicle (1) to a driver of the vehicle (1) and enabling the driver to confirm the command for adjustment of the at least one control parameter, and when the driver, via the interface, confirms the command for adjustment of the at least one control parameter, determining (S205) that the driver-initiated request for compensation of side pull of the vehicle (1) has been generated. A computer program comprising instructions which, when executed by a control device (100), cause the control device (100) to carry out the method according to any one of the preceding claims. A computer-readable medium comprising instructions which, when executed by a control device (100), cause the control device (100) to carry out the method according to any one of claims 1 to A control device (100) configured to reduce possible side pull of a vehicle (1), said vehicle (1) comprising a steerable tag axle (12) comprising tag axle wheels (6), wherein said control device (100) is configured to: in response to either a driver-initiated request for compensation of side pull of the vehicle (1) or an indication of unintentional side pull of the vehicle (1), said indication generated while the vehicle (1) is in motion, control the steerable tag axle (12) to adjust a predefined steering angle of at least one of the tag axle wheels (6) so as to at least partly compensate for side pull of the vehicle (1), said predefined steering angle corresponding to a neutral position of said at least one of the tag axle wheels (6). The control device (100) according to claim 12, further configured to: determine a first adjusted predefined steering angle of the at least one of the tag axle wheels (6) needed to overcome side pull of the vehicle (1), and when the determined first adjusted predefined steering angle of the at least one of the tag axle wheels (6) is within a predetermined acceptable range, control the steerable tag axle (12) to achieve said first adjusted predefined steering angle of the at least one of the tag axle wheels (6). The control device (100) according to any one of claims 12 and 13, further configured to:determine said indication of unintentional side pull of the vehicle (1) based on data relating to road inclination, |atera| acceleration, yaw velocity, vehicle speed, one or more parameters from steering system (10) of a front axle (5) of the vehicle (1), and/or one or more current control parameters of the steerable tag axle (12). A vehicle (1) comprising a steerable tag axle (12) and the control device (100) according to any one of claims 12 to 14.