Control device and method for controlling a trailing axle steering system

Abstract

Method performed by a control device (100) to control a trailing axle steering system (14), the trailing axle steering system (14) is designed to actively steer the trailing axle wheels (13) of a trailing axle (12) of a vehicle (1, 1'), the procedure includes one step of: in response to an indication that the vehicle (1, 1') in which the trailing axle (12) is arranged is being or is about to be driven in reverse while the trailing axle steering system (14) is operating in a trailing steering mode: locking (S103, S206) the position of the trailing axle wheels (13) in a current steering angle of the trailing axle wheels (13).

Description

TECHNICAL AREA

[0001] The present disclosure relates generally to a method for controlling a trailing axle steering system. The present disclosure further relates generally to a control device configured for controlling a trailing axle steering system. The present disclosure further relates generally to a computer program and a computer-readable medium. In addition, the present disclosure generally relates to a vehicle.

[0002] DE 103 29 234 A1 discloses a commercial vehicle with a leading and trailing axle with wheels steered by means of adhesion force and a space-saving positioning device with which the wheels can be returned from a steering position to a straight-ahead position and locked in place.

[0003] DE 40 12 699 A1 discloses a steering system for a multi-section road vehicle. Both directions of travel can be operated with steering stability without special guidance devices by controlling the steering angle of a trailing axle via an articulation angle. A steering ratio is adjusted depending on the direction of travel.

[0004] DE 34 43 102 A1 discloses a forced steering system for a leading or trailing axle of a truck. This system becomes effective when the truck is reversing below a certain speed and is characterized by direct and analogous control without steering inputs during the forced steering. BACKGROUND

[0005] Vehicles designed to transport heavy loads, such as trucks, semi-trailer trucks, buses, dump trucks, tractors, and trailers, often exert significant pressure on the ground due to their weight, especially when carrying a load. To manage this pressure, such vehicles often incorporate one or more trailing axles, each comprising a pair of trailing axle wheels. This reduces the pressure that each wheel of the vehicle must transmit to the ground. A trailing axle is a non-driven axle, meaning it does not provide power, and can be located in various positions on the vehicle. A trailing axle positioned in front of a drive axle in the vehicle's main direction of travel is often referred to as a pusher axle or pusher tag axle. A trailing axle positioned behind the drive axle is often referred to as a trailing axle or trailing tag axle.The trailing axle is often liftable so that the trailing axle wheels can be lifted off the ground when they are not needed, for example when the vehicle is not carrying a load.

[0006] To improve the vehicle's maneuverability, the trailing axle can be steerable. This means that the trailing axle wheels can be steered. This makes it possible, for example, to achieve a more suitable turning radius. Furthermore, the ability to steer the trailing axle wheels can also reduce tire wear on these wheels. The steering of the trailing axle wheels can be controlled by a trailing axle steering system. This steering can be synchronized with the steering of the vehicle's front wheels. However, the ability to steer the trailing axle wheels is subject to certain limitations and, of course, depends on the proper functioning of the trailing axle steering system. A malfunction in the trailing axle steering system will result in a loss of maneuverability, which can have detrimental consequences.To mitigate this risk, specific fault modes were developed for the operation of the trailing axle steering system. Generally, locking the trailing axle wheels in a neutral position, where they are aligned with the longitudinal direction or extent of the vehicle, is considered the safest mode. In this position, the vehicle continues to behave as the driver expects.

[0007] In certain cases, however, it can be difficult to return the trailing axle wheels to the neutral position. Another example of a fault mode therefore involves releasing the trailing axle wheel steering. In other words, the trailing axle steering system is put into a trailing axle steering mode. In such a mode, the trailing axle wheels are released and simply follow the vehicle, and are thus essentially steered by the lateral forces acting upon them. If the trailing axle wheel caster angle (i.e., the angular offset of the steering axis relative to the vertical axis of the wheel) is positive, the trailing axle wheels will self-center, eventually aligning with the longitudinal direction or extent of the vehicle, i.e., reaching the neutral position.When the trailing axle wheels are aligned in the direction of travel of the vehicle, they can be locked in this position (the neutral position). In other words, even after the trailing axle steering is released, the fault mode can still include locking the trailing axle wheels in the neutral position if they have reached it. Alternatively, if desired, the trailing axle wheels can remain in trailing mode even after reaching the neutral position.

[0008] WO 2014 / 163560 A1 discloses a system for steering at least one non-driven trailing axle of a vehicle. The system comprises an auxiliary unit designed to switch the system into a first fail-safe state with trailing axle steering when the vehicle speed is below a threshold speed at the time of a system malfunction, but to keep the trailing axle locked in a fixed neutral position oriented to the longitudinal direction of the vehicle in a second fail-safe state when the vehicle speed exceeds the threshold speed.

[0009] SE 1650840 A1 discloses an articulated vehicle comprising an articulating joint and an articulating joint sensor element configured to measure at least one joint parameter representing the joint state of the articulating joint. The vehicle further comprises a steerable trailing axle controlled by a trailing axle control unit. The trailing axle control unit is configured to receive a joint signal generated by the articulating joint sensor element, analyze the joint parameter value(s) with respect to a set of vehicle control rules, and determine a trailing axle steering command based on the result of the analysis. SHORT DESCRIPTION

[0010] The object of the present invention is to further improve the safety and maneuverability of a vehicle with a steerable trailing axle.

[0011] The problem is solved by the subject matter of the attached independent claims.

[0012] According to the present disclosure, a method for controlling a trailing axle steering system, performed by a control device, is provided. The trailing axle steering system is configured to actively steer the trailing axle wheels of a trailing axle of a vehicle. The method comprises a step of: in response to an indication that the vehicle in which the trailing axle is located is being, or is about to be, driven in reverse, while the trailing axle steering system is operating in a trailing axle steering mode, locking the position of the trailing axle wheels at a current steering angle of the trailing axle wheels.

[0013] Locking the position of the trailing axle wheels at the current steering angle temporarily or permanently disables the trailing axle steering mode. Because the position of the trailing axle wheels is locked, they can no longer rotate left or right due to lateral forces they may be subjected to. Locking the trailing axle wheels ensures that the vehicle behaves predictably when steered (for example, by a driver), regardless of the trailing axle wheel caster angle. This predictable vehicle behavior also enables safe reversing.

[0014] In other words, the present method allows the vehicle to be driven in reverse directly from a situation in which the trailing axle steering system is operating in a trailing steering mode.

[0015] In contrast, it was previously considered unsafe to reverse the vehicle when the trailing-steer system was operating in trailing-steer mode, as the vehicle might not behave as predicted by a driver or remote control center. Therefore, the possibility of reversing in such cases was previously prevented / prohibited or significantly restricted. This can cause considerable problems, for example, when parking the vehicle or driving in confined spaces where maneuvering back and forth may be necessary. However, with the present method, it is no longer necessary to prevent reversing, thus improving the vehicle's maneuverability.

[0016] The step of locking the position of the trailing axle wheels at the current steering angle can be performed when the trailing axle steering system is operating in a fault mode. When the trailing axle steering system is operating in a fault mode, the trailing axle wheels cannot be actively steered by the system. In particular, the trailing axle wheels cannot be actively steered to a neutral position. Therefore, when the trailing axle steering system is operating in a fault mode, the vehicle's maneuverability is fundamentally limited because it is not possible to steer the trailing axle wheels. The aforementioned trailing axle steering mode can be part of this fault mode. Specifically, the trailing axle steering mode can serve to mitigate the effects of the reduced maneuverability of the vehicle in the event of a trailing axle steering system malfunction.

[0017] The indication that the vehicle in which the trailing axle is located is being driven or is intended to be driven in reverse can be obtained from at least one of the vehicle's wheel sensors, a transmission management system, an engine management system, a sensor designed to detect the vehicle's direction of travel, and / or a positioning system to determine the vehicle's geographical position. In this way, a reliable indication of the vehicle's current direction of travel and / or its intended direction of travel (forward or reverse) can be derived.

[0018] The procedure may further include a step in which, if the trailing axle wheels are locked at the current steering angle of the trailing axle wheels, and in response to a determination that the vehicle in which the trailing axle is located is moving or is about to move forward, the trailing axle wheels are released so that the trailing axle steering system operates in trailing steering mode. In other words, the trailing steering can, in such a case, be returned to the trailing mode as it was used before reversing. This can further improve the vehicle's maneuverability, since the trailing steering mode allows the trailing axle wheels to self-center when the vehicle is moving forward, i.e., in the vehicle's main direction of travel.

[0019] The present method is particularly useful when the trailing axle wheels of the trailing axle have a positive caster angle during operation of the trailing axle steering system in trailing axle steering mode. In other words, the method is especially useful when the trailing axle wheels have a positive caster angle in the vehicle's main direction of travel (i.e., when driving forward). In such cases, the caster angle would be negative if the vehicle were traveling in reverse. If the trailing axle steering system is operating in trailing axle mode and the caster angle is negative (because the vehicle is traveling in reverse), the lateral forces to which the trailing axle wheels may be subjected by the vehicle's movement would steer the trailing axle wheels in an uncontrolled manner, potentially causing the trailing axle wheels to be turned maximally to the right or left. This, in turn, could lead to a catastrophic outcome.Therefore, reversing with trailing-edge steering was generally considered impossible and thus prevented or prohibited according to the prior art, as mentioned above. The present method overcomes this obstacle by locking the position of the trailing axle wheels at the current steering angle of the trailing axle wheels, as mentioned above. Because of this locking, the vehicle can be reversed safely, as the vehicle's behavior is essentially as predicted, for example, by a driver.

[0020] The trailing axle steering system can be an electro-hydraulic trailing axle steering system or an electric trailing axle steering system.

[0021] The present disclosure also provides a computer program comprising commands which, when executed by a control device, cause the control device to perform the procedure as described above.

[0022] The present disclosure also provides a computer-readable medium comprising instructions which, when executed by a control device, cause the control device to perform the procedure as described above.

[0023] Furthermore, the present disclosure provides a control device configured to control a trailing axle steering system, wherein said trailing axle steering system is configured to actively steer the trailing axle wheels of a trailing axle of a vehicle. The control device is configured to lock the position of the trailing axle wheels at a current steering angle of the trailing axle wheels in response to an indication that the vehicle in which the trailing axle is located is reversing or is about to be reversed, while the trailing axle steering system is operating in a trailing axle steering mode.

[0024] The control device offers the same advantages as described above in relation to the method disclosed herein for controlling a trailing axle steering system.

[0025] The control device can further be configured to control the trailing axle steering system in response to a fault signal indicating a malfunction of the trailing axle steering system, so that it operates in a fault mode. If this is the case, the trailing axle steering system can be operated in the trailing axle steering mode in said fault mode if one or more predetermined condition(s) are met.

[0026] The control device may further be configured to control the trailing axle so that, when the trailing axle wheels are locked in the current steering angle of the trailing axle wheel, and in response to a finding that the vehicle in which the trailing axle is arranged is moving forward or is about to move forward, it controls the trailing axle so that it operates in trailing steering mode by releasing the position of the trailing axle wheels.

[0027] The present disclosure further provides a vehicle comprising a trailing axle steering system configured to actively steer the trailing axle wheels of a trailing axle arranged in the vehicle. The vehicle further comprises the control device described above. The vehicle may be, but is not limited to, a heavy vehicle such as a bus or a truck. Furthermore, the vehicle may be an articulated vehicle, if desired. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 schematically shows a side view of a first example of a vehicle, Fig. Figure 2 schematically shows a top view of a second example of a vehicle, Fig. Figure 3a schematically shows a top view of the wheel axles of an example vehicle, showing the trailing axle wheels in a neutral position. Fig. Figure 3b schematically shows a top view of the wheel axles of an example vehicle, in which the trailing axle wheels are shown in a position deviating from the neutral position. Fig. Figure 4a schematically shows a steerable wheel of a vehicle, where the wheel is provided at a negative caster angle. Fig. Figure 4b schematically shows a steerable wheel of a vehicle, where the wheel is provided at a positive caster angle. Fig. Figure 5 presents a flowchart that schematically illustrates a first exemplary embodiment of the method for controlling a trailing axle steering system according to the present disclosure, Fig. Figure 6 presents a flowchart that schematically illustrates a second exemplary embodiment of the method for controlling a trailing axle steering system according to the present disclosure, Fig. Figure 7 schematically shows a device that may form, comprise, or be part of a control device for controlling a trailing axle steering system. DETAILED DESCRIPTION

[0028] The invention is described in more detail below with reference to exemplary embodiments and the accompanying drawings. However, the invention is not limited to the exemplary embodiments discussed and / or shown in the drawings, but can be varied within the scope of the accompanying claims. Furthermore, the drawings are not to be considered as being drawn to scale, since some features may be exaggerated to better illustrate the invention or its features.

[0029] In the present disclosure, a steered or steerable trailing axle is to be understood as comprising, at least when the vehicle in which the trailing axle is installed is in operation, its trailing axle wheels and the trailing axle steering system which is configured to steer the trailing axle wheels of the trailing axle.

[0030] When it is further described here that the trailing axle wheels are locked in a position (defined by the steering angle of the trailing axle wheels), this means that the trailing axle wheels cannot be turned left or right by either lateral forces or the trailing axle steering system. In contrast, in trailing axle steering mode, the trailing axle wheels are not in a locked position and can therefore be turned left or right by the lateral forces they may experience as a result of vehicle movement. However, it should be noted that in trailing axle steering mode, the trailing axle wheels are not actively steered by the trailing axle steering system.

[0031] The trailing axle steering system described in this disclosure is a trailing axle steering system configured to actively steer the trailing axle wheels. In this disclosure, the term "actively steer" is used to distinguish it from steering systems of so-called self-steering trailing axles, in which the trailing axle wheels are only passively steered. Generally, self-steering trailing axles are based on self-steering axle suspension systems in which only the pitch or caster angle of the wheels is adjusted such that the resistance of the wheels when the vehicle moves forward causes automatic steering of the wheels. There is no control unit configured to actively control the steering of these trailing axle wheels. In contrast, the trailing axle steering system described here is configured to actively control the steering of the trailing axle wheels.

[0032] Furthermore, when the direction of travel of a vehicle is described here as forward or backward, this should be understood in relation to the vehicle's primary direction of travel. Forward, therefore, means in the vehicle's primary direction of travel. However, the term "traveling forward" should not be understood to mean that the vehicle is traveling straight ahead, unless explicitly stated otherwise. It should be noted that although the vehicle is traveling forward or backward, it can also turn around at the same time.

[0033] Furthermore, a caster angle is the angular offset of the steering axis to the vertical axis of a steered wheel in the side view of a vehicle. With a positive caster angle, the steering axis is angled such that its central axis intersects the road surface, in the direction of travel of the vehicle encompassing the wheel, in front of the center of the wheel's contact patch on the road surface. It is important to note that the center of the wheel's contact patch on the road surface is considered here only in the direction of travel of the vehicle and not in a direction perpendicular to the direction of travel (i.e., not in a direction parallel to the wheel's axis of rotation). Conversely, with a negative caster angle, the steering axis is inclined such that its central axis intersects the road surface, viewed in the direction of travel, behind the center of the wheel's contact patch on the road surface. A configuration where the caster angle is 0° (i.e.,When the angle of incidence (neither positive nor negative) is significant, it is often referred to as vertical caster. In such a case, the center axis of the steering axle intersects the road surface essentially at the center of the wheel contact patch on the road surface in the direction of travel of the vehicle.

[0034] The trailing axle steering system described in the present disclosure can be a trailing axle steering system configured to steer the trailing axle wheels of a trailing axle installed in any land vehicle, in particular a heavy vehicle, such as a truck, bus, or trailer. The vehicle may or may not be an articulated vehicle. An articulated vehicle is a vehicle that has a pivot joint (joint connection) which allows for greater rotation of the vehicle. Furthermore, such a trailing axle can be located at any point on the vehicle and thus be a leading axle or a trailing axle. It should also be noted that a vehicle can be equipped with more than one steerable trailing axle if desired.

[0035] The present disclosure provides a method for controlling a trailing axle steering system, wherein the trailing axle steering system is configured to actively steer the trailing axle wheels of a trailing axle of a vehicle. The trailing axle steering system can, for example, be configured to steer trailing axle wheels of a trailing axle depending on information received from a front axle steering system of the vehicle, wherein the front axle steering system is configured to steer the front wheels of the vehicle and / or an articulation control system of the vehicle, wherein said articulation control system is configured to monitor and / or control at least one articulation parameter that represents an articulation state of the vehicle.In other words, the trailing axle steering system can be configured to steer the trailing axle wheels of a trailing axle based on information from the vehicle's front axle steering system, which is configured to steer the vehicle's front wheels. Alternatively or additionally, and if the trailing axle is located in an articulated vehicle, the trailing axle steering system can be configured to steer the trailing axle wheels based on information received from the vehicle's articulation control system, which is configured to monitor and / or control at least one articulation parameter that represents an articulation state of the vehicle.

[0036] The present method for controlling a trailing axle steering system comprises a step in which, in response to an indication that the vehicle (in which the trailing axle is located) is being or is about to be reversed, while the trailing axle steering system is operating in a trailing axle steering mode, the position of the trailing axle wheels is locked at the current steering angle of the trailing axle wheels. In other words, the method comprises, at a time when the trailing axle steering system is operating in a trailing axle steering mode, locking the position of the trailing axle wheels at the current steering angle of the trailing axle wheels in response to an indication that the vehicle (in which the trailing axle is located) is being or is about to be reversed.The aforementioned step of locking the trailing axle wheels at the current steering angle can be performed regardless of the actual value of the current steering angle. The current steering angle of the trailing axle wheels does not need to be known. Locking the trailing axle wheels at the current steering angle also means that the trailing axle steering mode is interrupted or terminated. This step therefore prevents the trailing axle wheels from rotating due to any lateral forces acting upon them.

[0037] The present procedure was primarily developed for the case where the trailing axle steering system operates in trailing axle steering mode as a result of operation in fault mode. The trailing axle steering system can operate in such a fault mode in response to an indication of a malfunction. It should be noted that the fault mode can include additional constituent modes besides the trailing axle steering mode. Another example of a constituent mode is the locking of the trailing axle wheels in the neutral position. The activation of the various constituent modes of the fault mode can depend on the respective conditions and thus on various parameters, such as the steering angle of the trailing axle wheels and / or the vehicle speed in which the trailing axle is located.However, it should be noted that the present procedure can also be applied in other situations where the trailing axle steering system is operated in a trailing steering mode (i.e., where the trailing axle wheels are enabled for trailing steering), and thus not only as a result of the trailing axle steering system operating in a fault mode.

[0038] In other words, the step of locking the position of the trailing axle wheels at the current steering angle of the trailing axle wheels can be performed when the trailing axle steering system is operating in a fault mode. The trailing axle steering system might be operating in a fault mode, for example, because a fault signal has been generated indicating a malfunction, thus putting the trailing axle steering system into a fault mode. The trailing axle steering system can operate in trailing steering mode while operating in fault mode. In other words, trailing steering mode can be a part of the fault mode.

[0039] The aforementioned indication that the vehicle (in which the trailing axle is located) is being, or is about to be, reversed can be obtained from any previously known device or system of the vehicle capable of determining the vehicle's direction of travel. This indication can be obtained from at least one wheel sensor, a transmission management system, and / or an engine management system. Alternatively, the indication can be derived using a positioning system configured to determine the vehicle's geographic position at a given time. Such a positioning system could, for example, include a global positioning system (GPS) or similar.Alternatively or additionally, such a positioning system may include one or more detection devices configured to detect the vehicle's position, with such detection devices being located in the infrastructure where the vehicle is to be located, at least temporarily. The indication that the vehicle is being, or is to be, reversed may alternatively or additionally be derived from other types of sensors that can be used to determine the vehicle's direction of travel, for example, a gyroscope.

[0040] An indication that the vehicle is being, or is about to be, reversed can be derived, for example, from a transmission management system through information about whether reverse gear is currently engaged or the detection of an indication to engage reverse gear. As another example, the indication that the vehicle is reversing can be obtained from one or more of the vehicle's wheel sensors by determining the direction of rotation of one or more wheels to which the sensor(s) are attached (and comparing this to a direction of rotation corresponding to the vehicle's forward movement). The wheel sensors can be assigned to any wheel of the vehicle, such as a front wheel, a drive wheel, or even a trailing axle wheel.Similarly, the indication that the vehicle is being, or is to be, reversed can be received, for example, from an engine management system configured to control an electric machine designed to propel the vehicle, the direction of rotation of which corresponds to a specific direction of travel for the vehicle (optionally in combination with information from a transmission management system about the currently engaged gear, if the vehicle has a transmission). A request for rotation of the electric machine in a specific direction, or an actual rotation of the electric machine in a specific direction, can thus indicate the intended (or current) direction of travel for the vehicle.Furthermore, a positioning system designed to determine a vehicle's geographic position can, for example, be used to determine a vehicle's direction of travel by comparing two successive geographic positions of the vehicle (those determined at two consecutive times). Alternatively, a positioning system can be used to determine a vehicle's direction of travel by combining map data with knowledge of the vehicle's orientation (longitudinal direction) relative to the aforementioned map data and an intended destination.

[0041] The method may further include a step in which the trailing axle wheels are released to enable the use of the trailing axle steering if the vehicle is or is intended to be driven forward again. In other words, the method may include a step in which, if the trailing axle wheels are locked at the current steering angle of the trailing axle wheels, and in response to a detection that the vehicle (in which the trailing axle is located) is or is intended to be driven forward, the trailing axle wheels are released so that the trailing axle steering system operates in trailing axle steering mode. This allows the trailing axle wheels to right themselves and self-align as the vehicle moves, further improving maneuverability.If there is a new indication that the vehicle is being or is about to be reversed, the procedure may again include a step to lock the trailing axle wheels at the current steering angle. This can be useful, for example, in situations where the vehicle is being operated in confined spaces, during parking maneuvers, or similar situations requiring multiple changes of direction.

[0042] The method described here for controlling a trailing axle steering system can be used with any type of previously known trailing axle steering system configured to actively steer the trailing axle wheels. However, in practice, it would probably be most useful if the trailing axle steering system is an electro-hydraulic or electric system. The trailing axle steering system can be a steer-by-wire system. An example of an electro-hydraulic trailing axle steering system to which the present method can be applied is described in the aforementioned WO 2014 / 163560 A1.

[0043] Furthermore, the execution of the procedure described here for controlling a trailing axle steering system can be controlled by programmed commands. These programmed commands typically take the form of a computer program which, when executed in or by a control device, causes the control device to perform the desired types of control actions. Such instructions can usually be stored on a computer-readable medium.

[0044] Furthermore, the present disclosure provides a control device configured to perform the above-described method for controlling a trailing axle steering system. The control device may be configured to perform one of the steps of the method for controlling a trailing axle steering system described herein.

[0045] More precisely, the present disclosure provides a control device configured to control a trailing axle steering system, wherein the trailing axle steering system is configured to actively steer the trailing axle wheels of a trailing axle of a vehicle. The trailing axle steering system can, for example, be configured to steer the trailing axle wheels of a trailing axle based on information received from a front axle steering system of a vehicle, wherein the front axle steering system is configured to steer the front wheels of the vehicle.If the trailing axle is arranged in an articulated vehicle, the trailing axle steering system may additionally or alternatively be configured to steer the trailing axles of the trailing axle wheels depending on information received from an articulation control system of the vehicle, wherein the articulation control system is configured to monitor and / or control at least one articulation parameter that represents an articulation state of the vehicle.

[0046] The control device is configured to lock the position of the trailing axle wheels at the current steering angle of the trailing axle wheels when the trailing axle steering system is operated in trailing axle steering mode, in response to an indication that the vehicle (in which the trailing axle is located) is being or is about to be driven backward (i.e., in reverse).

[0047] The control device may further be configured to control the trailing axle steering system in response to a fault signal indicating a malfunction of the trailing axle steering system, causing it to operate in a fault mode. This fault mode may comprise a number of different operating modes, selected according to the circumstances. In particular, the fault mode may include operating the trailing axle steering system in the aforementioned trailing axle steering mode. The control device may be configured to control the trailing axle steering mode in accordance with the fault mode, for example, depending on the vehicle speed and / or the steering angle of the trailing axle wheels when the fault mode is initiated.In other words, the control device can be configured to control the trailing axle steering system so that it operates in trailing axle steering mode (as a consequence of the fault mode) when one or more predefined conditions are met, where these predefined conditions may relate to the vehicle speed and / or the current steering angle of the trailing axle wheels. For example, trailing axle steering mode can be selected when the vehicle speed is below a predefined vehicle speed threshold and / or when the current steering angle of the trailing axle wheels is outside a predefined range of steering angles around the steering angle corresponding to the neutral position of the trailing axle wheels.

[0048] The control device for the trailing axle steering system can comprise one or more control units. If the control device comprises multiple control units, each control unit can be configured to control a specific function, or a specific function can be distributed among different control units. The control device can be located within the vehicle and thus constitute part of the vehicle. The control device can be part of the trailing axle steering system itself. Alternatively, the control device can be separate from the trailing axle steering system but configured to communicate with it to perform various control actions.

[0049] The present disclosure further provides a vehicle with a steerable trailing axle and the control device described above. The vehicle may be, for example, a heavy land vehicle such as a truck, a bus, a trailer, or the like.

[0050] Fig. Figure 1 schematically shows a side view of a first example of a vehicle 1. The vehicle 1 comprises a powertrain 2 with a drive unit, for example, an internal combustion engine 3. The powertrain 2 may further comprise a transmission 4 configured to transmit the drive torque from the drive unit to the drive wheels 6 (only one shown in the figure) of the vehicle 1 in various gear ratios. The vehicle 1 may also comprise a transmission management system 24 configured to control the transmission 4. The vehicle 1 may also comprise an engine management system 23 configured to control the drive unit. The transmission management system 24 and the engine management system 23 can typically be configured to communicate with each other for the purpose of controlling the vehicle powertrain 2.

[0051] The gearbox 4 can be connected to the drive wheels 6 via a drive shaft 5 and a drive wheel shaft 7. The drive shaft 5, the drive wheel shaft 7, and the drive wheels 6 are components of the drive train 2. The primary direction of travel of the vehicle 1, i.e., the direction of travel when the vehicle is moving forward, is indicated in the figure by arrow M.

[0052] The vehicle 1 also includes a front axle 9 and front wheels 8. The front wheels 8 are steered. The vehicle includes a front axle steering system 10, which is configured to control the steering of the front wheels 8. The vehicle 1 may also include a steering wheel 11. The steering wheel 11 can be operated by a driver of the vehicle 1 to steer the vehicle.

[0053] One or more of the wheels of the vehicle 1 can be equipped with one or more wheel sensors 18. Such wheel sensors are frequently used in the technical field and can, for example, be configured to determine the direction of rotation of the wheel (on which the wheel sensor is located) and / or its rotational speed. Fig. Figure 1 shows only one wheel sensor 18, which is assigned to a front wheel 8 of the vehicle 1. However, a wheel sensor can be arranged on any of the wheels of the vehicle 1. For example, all wheels of the vehicle 1 can be equipped with one or more wheel sensors 18.

[0054] The vehicle may further comprise at least part of a positioning system 25 configured to determine the vehicle's geographic position. Alternatively, the vehicle may comprise a communication device (not shown) configured to communicate with such a positioning system 25. The positioning system 25 may, for example, comprise or consist of a global positioning system (GPS) as known in the prior art. Alternatively or additionally, the positioning system may use sensing devices arranged in the infrastructure to determine the vehicle's geographic position at different times.

[0055] The vehicle 1 may further comprise a trailing axle 12 with associated trailing axle wheels 13. The trailing axle 12 with the trailing axle wheels 13 is not part of the drivetrain, and the trailing axle wheels 13 are therefore non-driven wheels. The trailing axle wheels 13 may be steerable via a trailing axle steering system 14. The trailing axle steering system 14 may be configured to steer the trailing axle wheels 13, for example, depending on information received from the front axle steering system 10. The vehicle 1 may further comprise a control device 100 configured to control the trailing axle steering system 14.

[0056] Vehicle 1 can be a heavy vehicle, such as a truck or a bus. Furthermore, the vehicle can be a hybrid vehicle, comprising an electric machine (not shown) in addition to the internal combustion engine 2. Alternatively, the vehicle can be a fully electric vehicle, comprising only an electric machine and not the internal combustion engine 3 shown. In this disclosure, the term "engine" refers to a drive unit of the vehicle and thus includes either an internal combustion engine or an electric machine. Furthermore, Vehicle 1 can be a manually controlled vehicle, a semi-autonomous vehicle, or a fully autonomous vehicle.

[0057] Fig. Figure 2 schematically shows a top view of a second example of a vehicle, here in the form of an articulated vehicle 1'. As in Fig. The vehicle 1 shown in Figure 1 comprises a front axle 9 with associated front wheels 8, a front axle steering system 10 for controlling the steering of the front wheels 8, a drive shaft 7 with associated drive wheels 6, and a trailing axle 12 with associated trailing axle wheels 13. Although not shown in the figure, the vehicle 1' further comprises a drive unit and may also include a transmission, similar to that in Figure 1. Fig. The vehicle 1 shown in Figure 1 comprises a joint 15 and a joint control system 16. The joint control system 16 is configured to control the joint, for example, based on information received from the front axle steering system 10 and / or various sensors or control units of the vehicle indicating the joint state of the vehicle. The joint control system 16 can, for example, be configured to control a joint angle of the joint 15.

[0058] The vehicle 1' further comprises a trailing axle steering system 14 and a control device 100 configured to control the trailing axle steering system. The trailing axle steering system 14 can be configured to steer the trailing axle wheels based on information received from the joint control system 16. The trailing axle steering system 14 can also be configured, if desired, to steer the trailing axle wheels based on information received from the front axle steering system 10.

[0059] It should be noted that the in Fig. 1. Vehicle shown, 1 and the one in Fig. The vehicle shown in Figure 2 is for illustrative purposes only, and the present invention is not limited to the vehicles shown or to the position of the trailing axle 12 in the vehicles mentioned. However, a trailing axle is arranged behind the front axle when viewed in the main direction of travel of the vehicle.

[0060] Fig. Figure 3a schematically shows a top view of the wheel axles 9, 7, 12 of a vehicle (for example, the one in Fig. Figure 1 shows the vehicle 1), in which the trailing axle wheels 13 are depicted in a neutral position. As can be seen from the figure, the wheels 13 of the driving axle are arranged in the neutral position such that their axis of rotation (which also coincides with the longitudinal axis of the trailing axle 12) is substantially perpendicular to a central axis A of the vehicle. In other words, the trailing axle wheels are substantially aligned with the longitudinal axis A of the vehicle in the neutral position. In the figure, the front wheels 8 are also shown to be substantially aligned with the longitudinal axis A. The in Fig. The position of the trailing axle wheels 13 and the front wheels 8 shown in 3a can typically occur when the vehicle is not turning but driving straight ahead. A malfunction of the trailing axle steering occurs when the trailing axle wheels are in the position shown in Fig. When the neutral position shown in 3a is reached, the trailing axle wheels 13 can be locked in this position, as it is considered the safest position until the trailing steering can be checked in a workshop or the like.

[0061] Fig. Figure 3b schematically shows a top view of the wheel axles 9, 7, 12, which shows the trailing axle wheels 13 in a position deviating from the neutral position. In other words, the steering angle of the trailing axle wheels 13 here deviates from the steering angle of the neutral position of the trailing axle wheels. More precisely, the trailing axle wheels are actively steered by the trailing axle steering system, for example, depending on information received from a front axle steering system. As in Fig. As shown in Figure 3b, the front wheels 8 are also rotated (by the vehicle's front axle steering system) from a position in which they are aligned with the vehicle's longitudinal axis A. The situation shown can typically occur when the vehicle is steered lightly. If a fault signal occurs indicating a malfunction of the trailing axle steering system when the trailing axle wheels are rotated as shown in Figure 3b, the vehicle's front axle steering system will be turned from a position where they are aligned with the vehicle's longitudinal axis A. Fig. As shown in Figure 3b, the trailing axle wheels 13 can, for example, be placed in a trailing steering mode. In this case, the trailing axle wheels 13 are not locked in any position and can therefore rotate due to the lateral forces to which they are subjected by the movement of the vehicle. If the vehicle continues to move forward and is no longer steered, the trailing axle wheels automatically align themselves to reach the neutral position (see Figure 3b). Fig. 3a) In other words, the steering angle of the trailing axle wheels approaches the steering angle of the neutral position. This is illustrated by arrow T, which indicates the direction of rotation of the trailing axle wheels due to the lateral forces when the vehicle is traveling straight ahead.

[0062] As mentioned above, the method for controlling a trailing axle steering system according to the present disclosure is particularly useful when the trailing axle wheels have a positive caster angle, as seen in the main direction of travel of the vehicle. In other words, the method is particularly useful when the trailing axle wheels have a positive caster angle when driving forward. In such a case, when the trailing axle steering system is operated in trailing axle steering mode, the trailing axle wheels can straighten out to align themselves with the main direction of travel as a result of possible lateral forces to which they are subjected due to the movement of the vehicle itself. Fig. 4a and Fig. Figure 4b schematically shows two different alternatives of caster angles.

[0063] In detail, it shows Fig. Figure 4a schematically shows a steerable wheel 30. The steerable wheel 30 could, for example, be a trailing axle wheel 13 as shown in the preceding figures. However, it should be noted that, if desired, other wheels of the vehicle can also be provided with different caster angles. The in Fig. The steerable wheel 30 shown in Figure 4a has a caster angle α that is negative when viewed in a primary direction of travel (indicated by arrow M) of the vehicle. Such a primary direction of travel M of the vehicle corresponds to the vehicle's direction of travel when moving forward. When the wheel 30 has a negative caster angle α, the steering axis (not shown) is inclined such that a central axis 32 of the steering axis intersects the roadway 33 behind the center of the contact point 34 of the wheel 30, as viewed in the direction of travel (here shown as the primary direction of travel M) of the vehicle. The center of the contact point 34 of the wheel 30 on the roadway 33 corresponds to a position where a vertical axis 31 of the wheel 30, perpendicular to a rotation axis of the wheel 30, intersects the roadway 33.

[0064] As opposed to Fig. 4a shows Fig. Figure 4b schematically shows the steered wheel 30 with a positive caster angle α, viewed in a main direction of travel (indicated by arrow M) of a vehicle. As shown in the figure, with a positive caster angle of the wheel 30, the central axis 32 of the steering axle intersects the road surface 33 in front of the center of the contact point 34 of the wheel 30 with the road surface when viewed in the direction of travel.

[0065] In a situation where the vehicle's direction of travel is reversed, so that the direction of travel is opposite to that indicated by the arrows M in the Fig. 4a and Fig. In the direction shown in 4b, wheel 30 would naturally point in the opposite direction M with a caster angle, since the angular displacement of the steering axis is not changed.

[0066] Fig. Figure 5 presents a flowchart that schematically illustrates a first exemplary embodiment of the method for controlling a trailing axle steering system according to the present disclosure. Optional steps of the exemplary embodiment are represented by dashed lines / boxes.

[0067] The procedure may include a first step S101, in which it is determined whether the trailing axle steering system is operating in a trailing axle steering mode. If the trailing axle steering system is not operating in a trailing axle steering mode, the procedure returns to the start. However, if the trailing axle steering system is operating in a trailing axle steering mode, the procedure may proceed to the subsequent step S102. Step S102 involves determining whether there is any indication that the vehicle in which the trailing axle steering is arranged is being, or is intended to be, driven in reverse. If there is no indication that the vehicle is being, or is intended to be, driven in reverse, the procedure may be reset to the start. However, if there is an indication that the vehicle is being, or is intended to be, driven in reverse, the procedure proceeds to step S103.Step S103 involves locking the position of the trailing axle wheels at the current steering angle of the trailing axle wheels. After step S103, the procedure can be terminated.

[0068] Alternatively, the procedure after step S103 may further include step S104, in which it is determined whether there is an indication that the vehicle is or is intended to be driven forward. If there is an indication that the vehicle is or is intended to be driven forward, the procedure continues with step S105, in which the trailing axle wheels are released so that the trailing axle steering system operates in trailing axle steering mode. In other words, the trailing axle steering system is controlled to operate in trailing axle steering mode by releasing the position of the trailing axle wheels. After step S105, the procedure may be reversed back to step S102.

[0069] Fig. Figure 6 presents a flowchart illustrating a second exemplary embodiment of the method for controlling a trailing axle steering system according to the present disclosure. Optional steps of the exemplary embodiment are represented by dashed lines / boxes.

[0070] According to the second exemplary embodiment, the method may include a first step S201 in which it is determined whether an error signal has been generated indicating a malfunction of the trailing axle steering system. If no such error signal has been generated, the method returns to the start after step S201. However, if it is determined in step S201 that an error signal has been generated indicating a malfunction of the trailing axle steering system, the method may continue with step S202.

[0071] Step S202 involves determining whether the (current) steering angle of the trailing axle wheels is offset from the steering angle of a neutral position for the trailing axle wheels. If the current steering angle of the trailing axle wheels does not differ from the steering angle of a neutral position for the trailing axle wheels, the procedure can continue with step S203, in which the trailing axle wheels are locked in the neutral position. After step S203, the procedure can be terminated. However, if the steering angle of the trailing axle wheels differs from the steering angle of the neutral position for the trailing axle wheels, the procedure can continue with step S204. Step S204 involves initiating and operating the trailing axle steering system in trailing axle steering mode. This releases the trailing axle wheels so that their steering angle can be changed as a result of the lateral forces to which the trailing axle wheels may be subjected.This allows the trailing axle wheels to be straightened when the vehicle is driving straight ahead, in order to approach and possibly reach the neutral position.

[0072] It should be noted that step S203, in which the trailing axle wheels are locked in the neutral position, and step S204, which involves operating the trailing axle steering system in trailing axle steering mode, can be parts of the trailing axle steering system's operation in a fault mode. In other words, if a fault signal is generated indicating a malfunction of the trailing axle steering system, the system can, depending on the circumstances, be put into either a trailing axle steering mode or a mode in which the trailing axle wheels are locked in the neutral position, corresponding to the operation of the trailing axle steering system in a fault mode. It should also be noted that, if desired, the fault mode can include further alternative modes depending on various circumstances.The trailing axle steering system may remain in fault mode until it has been repaired or replaced in a workshop or similar facility.

[0073] After step S204, the method may include step S205, in which it is determined whether there is any indication that the vehicle in which the trailing axle steering is arranged is being, or is about to be, driven in reverse. If there is any indication that the vehicle is being, or is about to be, driven in reverse, the method proceeds to step S206. Step S206 includes locking the position of the trailing axle wheels at the current steering angle of the trailing axle wheels. After step S206, the method may be terminated as shown in the figure. Alternatively, the method may include steps S104 and S105 as described above with respect to the first embodiment. If the method according to the second exemplary embodiment also includes steps S104 and S105, the method may return to step S205 after step S105.

[0074] Fig.Figure 7 schematically shows an exemplary embodiment of a device 500. The control device 100 described above can, for example, comprise the device 500, consist of the device 500, or be contained within the device 500.

[0075] 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, for example, 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, input / output capabilities, an analog-to-digital converter, a time and date input and transmission unit, an event counter, and an interrupt controller (not shown). The non-volatile memory 520 also has a second memory element 540.

[0076] A computer program P is provided which includes commands for controlling a trailing axle steering system, wherein the trailing axle steering system is configured to actively steer the trailing axle wheels of a trailing axle of a vehicle. The computer program includes commands to lock the position of the trailing axle wheels at the current steering angle of the trailing axle wheels in response to an indication that the vehicle in which the trailing axle is located is being, or is about to be, driven in reverse, when the trailing axle steering system is operating in a trailing axle steering mode.

[0077] The program P can be stored in executable form or in compressed form in a memory 560 and / or in a read / write memory 550.

[0078] The data processing unit 510 can perform one or more functions, i.e., the data processing unit 510 can execute a specific part of the program P stored in memory 560 or a specific part of the program P stored in read / write memory 550.

[0079] The data processing unit 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 for communication with the data processing unit 510 via a data bus 511. The read / write memory 550 can communicate with the data processing unit 510 via a data bus 514. Communication between the individual components can take place via a communication link. A communication link can be a physical connection, such as an optoelectronic communication line, or a non-physical connection, such as a wireless connection, for example, a radio or microwave link.

[0080] When data is received via data port 599, it can be temporarily stored in the second memory element 540. Once the received input data has been temporarily stored, the data processing unit 510 is ready to execute the code as described above.

[0081] Parts of the procedures described here can be executed by the device 500 using the data processing unit 510, which executes the program stored in the memory 560 or in the read / write memory 550. When the device 500 executes the program, the procedures described here are carried out.

Claims

[1] Method carried out by a control device (100) to control a trailing axle steering system (14), the trailing axle steering system (14) is designed to actively steer the trailing axle wheels (13) of a trailing axle (12) of a vehicle (1, 1'), the procedure includes one step of: in response to an indication that the vehicle (1, 1') in which the trailing axle (12) is arranged is being or is about to be driven in reverse while the trailing axle steering system (14) is operating in a trailing steering mode: locking (S103, S206) the position of the trailing axle wheels (13) in a current steering angle of the trailing axle wheels (13). [2] Method according to claim 1, wherein the step of locking (S103, S206) the position of the trailing axle wheels (13) in the current steering angle of the trailing axle wheels (13) is performed when the trailing axle steering system (14) is operated in a fault mode. [3] Method according to one of the preceding claims, wherein the indication that the vehicle (1, 1') in which the trailing axle (12) is arranged is being driven or is to be driven in reverse is obtained from at least one wheel sensor (18) of the vehicle (1, 1'), a transmission management system (24) of the vehicle (1, 1'), an engine management system (23) of the vehicle (1, 1'), a sensor configured to determine a direction of travel of the vehicle, and / or a position determination system (25) configured to determine the geographical position of the vehicle (1, 1'). [4] A method according to any of the preceding claims, further comprising a step such that: when the trailing axle wheels (13) are locked in the current steering angle of the trailing axle wheels (13) and in response to a determination that the vehicle (1, 1') in which the trailing axle (12) is arranged is moving forward or is about to move forward, the trailing axle wheels are released (S105) so that the trailing axle steering system (14) is operated in trailing steering mode. [5] Method according to one of the preceding claims, wherein when the trailing axle steering system (14) is operated in trailing steering mode, the trailing axle wheels (13) of the trailing axle (12) have a positive caster angle (α). [6] Method according to any of the preceding claims, wherein the trailing axle steering system (14) is an electro-hydraulic trailing axle steering system or an electric trailing axle steering system. [7] Computer program (P) with instructions which, when executed by a control device (100), cause the control device (100) to execute the method according to any of the preceding claims. [8] Computer-readable medium containing instructions which, when executed by a control device (100), cause the control device (100) to execute the method according to any one of claims 1 to 6. [9] Control device (100) configured to control a trailing axle steering system (14), the trailing axle steering system (14) is designed to actively steer the trailing axle wheels (13) of a trailing axle (12) of a vehicle (1, 1'), wherein the control device (100) is configured to: In response to an indication that the vehicle (1, 1') in which the trailing axle (12) is arranged is being or is about to be driven in reverse while the trailing axle steering system (14) is operating in a trailing steering mode, the position of the trailing axle wheels (13) is locked in a current steering angle of the trailing axle wheels (13). [10] Control device (100) according to claim 9, which is further configured to: in response to an error signal indicating a malfunction of the trailing axle steering system (14), the trailing axle steering system is controlled to operate in an error mode, wherein in fault mode, if one or more predetermined condition(s) is / are met, the trailing axle steering system (14) is operated in trailing steering mode. [11] Control device (100) according to one of claims 9 or 10, which is further configured to: when the trailing axle wheels (13) are locked in the current steering angle of the trailing axle wheels (13) and in response to a determination that the vehicle (1, 1') in which the trailing axle (12) is arranged is moving forward or is about to move forward, the trailing axle steering system controls to operate in trailing steering mode by releasing the position of the trailing axle wheels (13). [12] Vehicle comprising (1, 1'): a trailing axle steering system (14) configured to actively steer trailing axle wheels (13) of a trailing axle (12) arranged in the vehicle (1, 1'), and the control device (100) according to one of claims 9 to 11.

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