Adaptive steering

Abstract

A towed vehicle, comprising a number of interspaced steerable wheel groups that each have one or more steerable wheels, the wheels of each steerable wheel group being pivotable about a wheel steering axis of that steerable wheel group so as to include a steering angle relative to a longitudinal axis of the vehicle in response to a steering moment exerted on the wheels of the wheel group by a central steering actuator of the towed vehicle that acts on the wheels of at least one of the steerable wheel groups, said interspaced steerable wheel groups being coupled via a physical steering link included between said interspaced steerable wheel groups, which steering link transfers the steering moment of the steering actuator and couples pivoting movement of the wheels of said interspaced steerable wheel groups about their respective wheel steering axes in accordance with a transfer function, characterized in that the physical steering link between said interspaced steerable wheel groups includes a powered set-up actuator that is arranged to adjust the physical steering link so as to change the set-up of the transfer function of the coupling of the wheels of the interspaced steerable wheel groups.

Description

[0001] Title: Adaptive steering

[0002] The invention generally relates to towed vehicles, and in particular to towed vehicles comprising a number of interspaced steerable wheel groups that each have one or more steerable wheels. Such towed vehicle may e.g. be a trailer, a flatbed, a semi low loader, a low loader, a dolly or combinations thereof.

[0003] In practice, the wheels of each steerable wheel group of a towed vehicle are typically pivotable about a wheel steering axis of that steerable wheel group so as to include a steering angle relative to a longitudinal axis of the vehicle in response to a steering moment exerted on the wheels of the wheel group. Such steering moment may be safely, reliably, and cost effectively be applied by one or more central steering actuators of the towed vehicle that acts on the wheels of at least one of the steerable wheel groups. The interspaced steerable wheel groups may then be coupled via a physical steering link included between the interspaced steerable wheel groups, e.g. a steering rod. The steering link then transfers the steering moment of the steering actuator and couples pivoting movement of the wheels of said interspaced steerable wheel groups.

[0004] For towed vehicles it is not easy to have all wheels of interspaced steerable wheel groups perform a purely circular movement around the same centre during travel through a bend. The bend radius and the position of the centre of the bend, i.e. the momentary centre, differ at a given angular displacement of the longitudinal axis of the pulling vehicle relative to the longitudinal axis of the towed vehicle. When a towed vehicle negotiates a bend and a steered wheel is not provided with a steering angle that corresponds with the momentary centre, that wheels shall not only roll in the travel direction over the road surface, but shall also skid sideways over the road surface. This causes additional wear of the tire, and additional loads on the wheel and its suspension. To allow the wheels of interspaced steerable wheel groups to perform a circular movement around the same centre during travel through a bend, the physical link may be arranged to transfer the steering moment of the steering actuator and to couple pivoting movement of the wheels of the interspaced steerable wheel groups about their respective wheel steering axes in accordance with a transfer function. This way, the steering deflections of the wheels of the various wheel groups can be adapted to match their position relative to the centre.

[0005] However, the ratio of the steering angles of the steerable wheels of the pulled vehicle, i.e. the steering deflections of the wheels, and the angular displacement of the pulling vehicle relative to the pulled vehicle will be optimal only at a specific distance between the coupling, the steerable wheels and any non-steerable wheels. At other distances, i.e. when the pulled vehicle is changed in length or width relative to this specific distance, this ratio will represent a compromise, and significant sideways skidding shall still occur.

[0006] The problem of sideways skidding of steerable wheels over the road surface occurs particularly in reconfigurable towed vehicles in which the steerable wheels can be placed at different longitudinal and / or transverse positions relative to the longitudinal axis, such as trailers, flatbeds, semi low loaders, low loaders, dollies or combinations thereof that are configurable in their length- and / or width depending on use requirements, e.g. using telescoping or modular portions. To address this problem, it has been proposed to provide additional mounting holes and manually reposition the ends of the steering rods to correspond to various configurations of length and width of the towed vehicle. This proposal has not met much success, as the steering rods are difficult to access and repositioning is labor intensive, hard to carry out safely and correctly, while the end result remains a compromise and is available for a limited number of configurations of the towed vehicle. Further, due to the requirement of manual access to the steering rods, this proposal is available for a limited set of suspension and steering types. Also, it has been proposed to use a lockable lever to switch between transfer modes for the steering rod depending on configuration of the towed vehicle, which is available for a limited number of interspaced centrally steered wheel groups only, e.g. 3. In addition, it leads to a compromise and is available for a limited number of configurations of the towed vehicle.

[0007] Further, it has been proposed to dispense with a central steering actuator for a number of interspaced steerable wheel groups, and to make the steerable wheel groups independently steerable using local steering. However, this is less cost effective than using central steering actuators, and is also more difficult to implement safely and reliably. As an alternative, in W02023003472A1 a hybrid system has been proposed in which interspaced steerable wheel groups are steered using both central steering and local steering. In this system, length adjustable steering rods adjust the amount of deflection per wheel group provided by the central steering actuator during the steering operation, the amount of adjustment per wheel group depending on the configuration of the towed vehicle. However, this requires complex control and relatively sturdy actuators. In addition, in case of malfunction the system returns to a safe mode which is independent of the actual configuration of the towed vehicle, and which may thus may not be suitable for operation in that configuration.

[0008] The invention aims to alleviate the disadvantages of the prior art. Specifically, the invention aims to provide a for a towed vehicle comprising interspaced steerable wheel groups that includes central steering and a physical steering link included between said interspaced steerable wheel groups, in particular a reconfigurable towed vehicle in which the steerable wheels can be placed at different longitudinal and / or transverse positions relative to the longitudinal axis, with which the steering deflections of the various wheels can be adapted to match their position relative to the momentary centre more cost effectively, safely, reliably, and / or correctly, in particular for a large number of steerable wheel groups, a large number of configurations of the towed vehicle, and a large number of types of steering and suspension.

[0009] Thereto, the invention provides for a towed vehicle, comprising a number of interspaced steerable wheel groups that each have one or more steerable wheels, the wheels of each steerable wheel group being pivotable about a wheel steering axis of that steerable wheel group so as to include a steering angle relative to a longitudinal axis of the vehicle in response to a steering moment exerted on the wheels of the wheel group by a central steering actuator of the towed vehicle that acts on the wheels of at least one of the steerable wheel groups, said interspaced steerable wheel groups being coupled via a physical steering link included between said interspaced steerable wheel groups, which steering link transfers the steering moment of the steering actuator and couples pivoting movement of the wheels of said interspaced steerable wheel groups about their respective wheel steering axes in accordance with a transfer function, wherein the physical steering link between said interspaced steerable wheel groups includes a powered set-up actuator that is arranged to adjust the physical steering link so as to change the set-up of the transfer function of the coupling of the wheels of the interspaced steerable wheel groups.

[0010] By including a powered set-up actuator that is arranged to adjust the physical steering link so as to change the set-up of the transfer function of the coupling of the wheels of the interspaced steerable wheel groups, the transfer function can for each configuration of the vehicle be set-up to match their position relative to the momentary centre without need for manual reconfiguration in a safe, reliable and accurate way, without need for continuous adjustment during steering operations. The actuator facilitates adjustment of the physical link to a plurality of configurations, in particular by providing a continuous or multi-stepped adjustment of the physical link. It is observed that with this context, a steerable wheel group is meant to include one or more steerable wheels. A steerable wheel group may e.g. include one wheel on one longitudinal side of a vehicle, a wheel set on one longitudinal side of vehicle, or wheelsets on opposite sides of a vehicle axle line. Such steerable wheel may e.g. be carried on a pendle axle, a trough axle, or on independent suspension, may e.g. be coil sprung or air sprung. The steering may be e.g. be rod steering or turntable steering.

[0011] Further, it is observed that, within the context of this patent application, interspaced wheel groups are to be considered interspaced with respect to their steering axes, which may be an interspace in a direction along a longitudinal axis of the towed vehicle, e.g. a placement of one behind the other in direction in of straight forward travel in side view of the towed vehicle, and / or an interspace in a direction transverse to a longitudinal axis of the towed vehicle, e.g. a placement on opposite sides of the towed vehicle in rear view of the towed vehicle seen in direction of straight forward travel.

[0012] Also it is observed that in this context, a powered actuator is meant to comprise an actuator that is arranged to act under power from a power source, e.g. a hydraulic, electric and / or pneumatic power source, i.e. without need for supply of human power.

[0013] Additionally it is observed that in the context of this invention, that a transfer function may be construed as the relation between an input, in particular a steering angle of a first wheel group of two interspaced wheel groups that are connected via a physical steering link included between said interspaced steerable wheel groups, and an output, in particular in particular a steering angle of a second wheel group of the two interspaced wheel groups that are connected via the physical steering link included between said interspaced steerable wheel groups. The transfer function may typically be a continuous function. The input may be an actual steering angle of the first wheel group, and may e.g. vary from a neutral steering angle to a maximum input steering angle. The output may be an actual steering angle of the second wheel group, and may e.g. vary from a neutral steering angle to a maximum steering angle of the second wheel group. The function may include progressive, digressive, and / or linear sections. The progression of the function may depend on the set-up of the physical hnk between the interspaced wheel groups.

[0014] When the transfer function departs from a neutral steering position of the wheels of the steerable wheel groups that allows straight travel of the vehicle along its longitudinal axis, and when the powered setup actuator is arranged to adjust the physical steering link so as to change the set-up of the transfer function with maintenance of its neutral steering position, the set-up may be applied to any configuration of the towed vehicle without influencing its capacity for straight travel.

[0015] When the powered set-up actuator is arranged with at least two actuated degrees of freedom to adjust the physical steering link, changing the set-up without influencing the towed vehicle’s capacity for straight travel may be facilitated, and accurate adjustment of the steering deflections of the wheels of the various wheel groups to match their position relative to the centre can be facilitated for a large number of configurations of the towed vehicle. The at least two actuated degrees of freedom of the setup actuator may be realized with a single actuator unit, e.g. using a displacement track or linkage for at least one end of the physical steering link. The at least two actuated degrees of freedom of the set-up actuator may also be realized with distinct actuator units, which may be separate or integrated, and which may be separately and / or independently controlled. The actuated degrees of freedom may e.g. include 1 actuated degree of translation and 1 actuated degree of rotation, 2 actuated degrees of translation, 2 actuated degrees of rotation, 1 actuated degree of translation and 1 actuated degree of rotation, 2 actuated degrees of translation and 1 actuated degree of rotation or 1 actuated degree of translation and 2 actuated degrees of rotation, etc. When the powered set-up actuator is arranged to adjust the physical steering link in at least a plane that extends transversely to the steering axis, the set-up actuator may be implemented relatively easily in a large number of different steering and / or suspension types. The plane may be an x, y plane perpendicular to a z axis that extends parallel to the steering axes, but may also be a plane extending obliquely to the z axis. The x axis may be a longitudinal axis of the towed vehicle, the y axis may be a transverse axis of the towed vehicle, and the z axis may be an upright axis of the towed vehicle.

[0016] The powered set-up actuator may be arranged to adjust the physical steering link in at least two perpendicular directions in said plane, e.g. in an x and y direction, in particular each direction corresponding to an actuated degree of freedom, e.g. a first actuator unit for adjustment in x direction and a second actuator unit for adjustment in y direction.

[0017] The powered set-up actuator may alternatively or in addition be arranged to adjust the physical steering link in at least a direction transverse to said plane, i.e. along the steering axis, e.g. in a z direction. This may further facilitate implementation in a large number of different steering and / or suspension types.

[0018] The powered set-up actuator may efficiently be arranged to adjust the physical steering link along at least two of a longitudinal axis of towed vehicle (x), a transverse axis of the towed vehicle (y) and an upright axis towed vehicle (z), e.g. each with an actuated degree of freedom, e.g. each realized with a dedicated actuator unit.

[0019] The powered set-up actuator may be arranged to operate in response to a set-up signal. Such set-up signal may conveniently only made available during set-up of the towed vehicle, e.g. when the towed vehicle is stationary. During set-up, the towed vehicle may either be loaded or unloaded. The set-up signal may e.g. not be made available when the steering actuator is acting in response to a steering signal, e.g. to prevent changing the set-up during steering. This way, the actuator may be prevented from being subjected to large loads, and disturbance of the towed vehicle’s steering behavior while driving may be avoided.

[0020] The powered set-up actuator may be arranged to act on the link during set-up only. The powered set-up actuator may then e.g. be prevented from actuating when the towed vehicle performs a steering movement, i.e. when the steering actuator is acting on a steering signal. The powered setup actuator may then e.g. be prevented from actuating when the towed vehicle is moving and its wheels are rolling.

[0021] The steerable wheel groups may be interspaced along a longitudinal axis of the towed vehicle, and / or transversely to a longitudinal axis of the towed vehicle.

[0022] The powered set-up actuator may be arranged to be accessory to the physical link between the steerable wheel groups. This way, when the set-up actuator is inactive, the physical link between the steerable wheel groups remains intact. After set-up, the physical link can thus remain as is, i.e. intact without adjustment. The set-up actuator may e.g. be considered inactive when it is switched off, powerless or when it fails.

[0023] When the powered set-up actuator is locked against adjustment under external force, adjustment of the set-up actuator under external force may be counteracted. The lock may e.g. include an externally applied lock, but may e.g. as an alternative or in addition include a self-locking, selfbraking or self-hemming drive.

[0024] The powered set-up actuator may e.g. be electrically, hydraulically and / or pneumatically powered. The powered set-up actuator may include an accumulator for accumulating power for the powered actuator. This way, the set-up actuator may be used to set the steering up to match a configuration of the towed vehicle without need for the set-up actuator external to be connected to a power source, which is e.g. useful when the towed vehicle is not provided with external power. The powered set-up actuator may include a motor or pump to drive the actuator. The powered set-up actuator may include one or more of a spindle, a telescoping cylinder, and an excentre to provide motion.

[0025] The physical steering link may include a mechanical steering element, and the powered set-up actuator may be arranged to adjust an axial length and / or to displace a mounting point of the mechanical steering element.

[0026] The invention further relates to a steering system for a towed vehicle, in particular a towed vehicle provided with one or more of the features discussed above, the steering system having a physical steering link including a powered set-up actuator that is arranged to adjust the physical steering link so as to change the set-up of the transfer function of the coupling of the wheels of the interspaced steerable wheel groups.

[0027] The invention also relates to a method of setting up steering of a towed vehicle, preferably a towed vehicle provided with one or more of the features discussed above, the towed vehicle comprising a number of interspaced steerable wheel groups that each have one or more steerable wheels, the wheels of each steerable wheel group being pivotable about a wheel steering axis of that steerable wheel group so as to include a steering angle relative to a longitudinal axis of the vehicle in response to a steering moment exerted on the wheels of the wheel group by a central steering actuator of the towed vehicle that acts on the wheels of at least one of the steerable wheel groups, said interspaced steerable wheel groups being coupled via a physical steering link included between said interspaced steerable wheel groups, which steering link transfers the steering moment of the steering actuator and couples pivoting movement of the wheels of said interspaced steerable wheel groups about their respective wheel steering axes in accordance with a transfer function, in which method the transfer function of the coupling of the wheels of the physical steering link is adjusted by actuation of a powered set-up actuator included in the physical steering link between said interspaced steerable wheel groups that is arranged to adjust the physical steering link so as to change the set-up of the transfer function of the coupling of the wheels of the interspaced steerable wheel groups.

[0028] The transfer function of the towed vehicle departs from a neutral steering position of the wheels of the steerable wheel groups that allows straight travel of the vehicle along its longitudinal axis, and wherein the powered set-up actuator is used to adjust the physical steering link so as to change the set-up of the transfer function while maintaining its neutral steering position. The set-up may e.g. be changed only when the vehicle is stationary, and the set-up may be maintained unchanged when the vehicle is moving.

[0029] Still further, the invention relates to a method of retrofitting a towed vehicle, the towed vehicle comprising a number of interspaced steerable wheel groups that each have one or more steerable wheels, the wheels of each steerable wheel group being pivotable about a wheel steering axis of that steerable wheel group so as to include a steering angle relative to a longitudinal axis of the vehicle in response to a steering moment exerted on the wheels of the wheel group by a central steering actuator of the towed vehicle that acts on the wheels of at least one of the steerable wheel groups, said interspaced steerable wheel groups being coupled via a physical steering link included between said interspaced steerable wheel groups, which steering link transfers the steering moment of the steering actuator and couples pivoting movement of the wheels of said interspaced steerable wheel groups about their respective wheel steering axes in accordance with a transfer function, in which method a physical steering link between interspaced steerable wheels groups is provided with a powered set-up actuator that is arranged to adjust the physical steering link so as to change the set-up of the transfer function of the coupling of the wheels of the interspaced steerable wheel groups. The above aspects of the invention individually alleviate disadvantages, and in combination can alleviate disadvantages further. The above aspects of the invention together form an invention, but may each individually also be seen as inventions on their own.

[0030] The invention will further be elucidated on the basis of exemplary embodiments which are represented in the drawings. The exemplary embodiments are given by way of non-limitative illustration of the invention.

[0031] In the drawings:

[0032] Figs. 1A and IB show a schematic top view of the wheel positions of a towing vehicle and a towed vehicle according to the state of the art for an elongated and a regular sized towed vehicle respectively;

[0033] Figs. 2A and 2B show a schematic top view of the wheel positions of a towing vehicle and a towed vehicle according to an example of the invention for an elongated and a regular sized towed vehicle respectively;

[0034] Fig. 3 shows a side-by-side comparison of the wheel positions of a towing vehicle and a towed vehicle according to an example of the invention;

[0035] Fig. 4 shows a side-by-side comparison of a schematic top view of the wheel positions of the example of Fig. 3 in a different configuration;

[0036] Figs. 5A-5D show a schematic top views of various examples of steering systems according to the invention.

[0037] The figures are schematic representations only, and are given by way of non-limited examples. In the figures, the same or corresponding parts are designated with the same reference numerals.

[0038] Referring to Figs 1A and IB, schematic top views of the wheel positions for a truck 200, or towing vehicle, and a towed vehicle 100 according to the state of the art have been depicted. In both figures, the towed vehicle 100 has an equal number of steerable wheel groups 10, each steerable wheel group 10 comprises two wheels 11. In Fig. 1A, an elongated towed vehicle 100 has been depicted, which is a longer towed vehicle 100 than the towed vehicle of Fig. IB. In the shown example, the steerable wheel groups 10 in Figs 1A and IB have been provided at substantially the same distance from the rear of the towed vehicle 100, i.e. on the opposite side of the towed vehicle 100 from where the truck 200 is located. As a result, the elongated towed vehicle 100 of Fig. 1A comprises a longer bridging section 101, i.e. the section between the wheel groups 10 nearest to the truck 200 and the wheel group 201 of the truck nearest to the towed vehicle 100. In both figures an example is given for when the truck 200 towing a towed vehicle 100 is making a left turn in a direction of travel. In an idealized situation, it can be seen that when the front most wheels 202 turn about their respective steering axis, imaginary lines drawn perpendicular to the direction of motion D of each of wheel steering axis converge to a first momentary centre Cl. Since the imaginary lines of the front most wheels 202 and the sets of rear wheels 202 of truck 200 converge in a momentary centre Cl, the wheels of the truck 200 can perform a purely circular movement such that the wheels 200 can roll in the direction of travel over a road surface without a movement component perpendicular to the circular movement. Turning to the towed vehicle 100 known from the state of the art, it can be seen that the imaginary lines of each of the wheel steering axis 12 converge at a separate momentary centre C2. Since Cl and C2 do not overlap, the truck 200 and towed vehicle 100 combination does not have a combined momentary centre, and as a result some of the wheels will skid sideways over the road surface when the truck 200 is making the exemplary left turn. Turning to Fig. IB, a different conventional towed vehicle 100 is shown. As previously stated, this towed vehicle 100 is of a reduced length compared to the towed vehicle 100 of Fig. 1A. While some of the imaginary lines intercept one another, they do converge in two tow separate momentary centres Cl’ and C2’. Therefore, the issue of sideward skidding wheels 10 is also present in the example with a shorter towed vehicle 100. It should be noted that, with respect to the momentary centres Cl, Cl’, C2 and C2’, a simplified and schematic representation is shown. In practice, not all imaginary lines may converge to a single momentary centres. For example, it may happen that a few lines of a larger set of imaginary lines do not converge. However, in order to clearly illustrate the disadvantages of the prior art converging momentary centres have been depicted.

[0039] Turning to Figs 2A and 2B, a schematic top view of the wheel positions for a truck 200, or towing vehicle, and a towed vehicle 100 according to an example of the invention have been depicted. The towed vehicle 100 comprises a number of interspaced steerable wheel groups 10 that each have one or more steerable wheels 11. The wheels 11 of each steerable wheel group 10 are being pivotable about a wheel steering axis 12 of that steerable wheel group 10 so as to include a steering angle a relative to a longitudinal axis of the vehicle in response to a steering moment exerted on the wheels 11 of the wheel group 10 by a central steering actuator 13 of the towed vehicle 100, that acts on the wheels 11 one of the steerable wheel groups 10. The interspaced steerable wheel groups 10 are being coupled via a physical steering link 14 included between said interspaced steerable wheel groups 10. Said steering link 14 transfers the steering moment of the steering actuator 13 and couples pivoting movement of the wheels 11 of said interspaced steerable wheel groups 10 about their respective wheel steering axes 12 in accordance with a transfer function. The physical steering link 14 between the interspaced steerable wheel groups 10 includes a powered set-up actuator 15 that is arranged to adjust the physical steering link 14 so as to change the set-up of the transfer function of the coupling of the wheels 11 of the interspaced steerable wheel groups 10. In the shown example, the steerable wheel groups 10 are interspaced along a longitudinal axis of the vehicle and are interspaced transversely to a longitudinal axis of the vehicle. In both depicted examples, it can be seen that by adjusting the physical steering links 14, the transfer function between the input of the steering actuator 13 and the steering angle a of wheel groups 10 can be actuated such that there exists a single momentary centre C in which the imaginary lines converge. In other words, the there is no sideward skidding of wheels 10 in the shown example.

[0040] In Fig 3 a side-by-side comparison between a towed vehicle 100, being towed by a towing vehicle 200, which has the same transfer function provided by the powered set-up actuator 15 but having different steering angles are shown. The transfer function departs from a neutral steering position of the wheels 11 of the steerable wheel groups 10 that allows straight travel of the vehicle 100 along its longitudinal axis. The powered set-up actuator 15 is arranged to adjust the physical steering link 14 so as to change the set-up of the transfer function with maintenance of its neutral steering position.

[0041] The powered set-up actuator 15 is arranged to adjust the physical steering link 14 along at least two of a longitudinal axis of towed vehicle, a transverse axis of the towed vehicle and an upright axis of the towed vehicle in order to facilitate a large range of possible transfer functions. These directions correspond to the x, y and z direction respectively. Facilitating that the physical steering link 14 can be adjusted in a 3D-space spanned by the x, y and z directions results in that there may be multiple configurations of the steering link 14 possible that result in an identical transfer function. As a result, it may be possible to pick the most efficient to obtain transfer function such that the steering link 14 is minimally adjusted.

[0042] Turning to Fig. 4, a side-by-side comparison between a towed vehicle 100 and a towing vehicle 200 is shown, in which the powered set-up actuator 15 has rearranged the steering links 14 to allow for ‘crab -steering’. Driving in a straight line, as depicted on the left hand, it can be seen that the wheels 10 are pointing to the same direction such that there is no skidding. Once the towing vehicle 200 makes a turn, e.g. the right turn shown in the right figure, the wheels 10 of the individual steering groups 11 again face in the same direction, under the same steering angle a relative to the longitudinal axis of the towed vehicle 100. This set-up allows for ‘crabsteering’, in which the towed vehicle 100 has a movement component in a direction that is perpendicular to its longitudinal direction. When crabsteering, imaginary lines drawn perpendicular to the direction of travel starting from the wheel steering axis 12 of the towed vehicle 100 do not converge in a momentary centre. However, since they are parallel to each other and perpendicular to the direction of travel D, the wheels 11 of the towed vehicle do not skid.

[0043] In Figs. 5A-5D, various examples of a steering systems 19 for a towed vehicle 100 have been depicted. In all four depicted examples, a steering system 17 has been depicted with a physical steering link 14 that includes a powered set-up actuator 15 that is arranged to adjust the physical steering link 14, thereby changing the set-up of the transfer function of the coupling of the wheels 11 of the interspaced steerable wheel groups 10. For illustration purposes, only two wheel sets 10 have been depicted. However it will be clear to the person skilled in the art that any number of wheel sets 10 can be provided that can be connected via steering systems 17.

[0044] In a first example of a steering system 17 a powered set-up actuator 15 is depicted in Fig. 5A. In the example, the powered set-up actuator 15 comprises an excentre 20 at both ends of the steering link 14. The excentre 20 is arranged to physically connect an end of the steering link 14 to a corresponding wheel group 10, preferably near the wheel steering axis 12. Due to the physical connection between the wheel groups 10, the transfer function prescribing the steering angle of a wheel set 10 as a result of the steering angle of a connected wheel set 10, can be adjusted by rotating one or more excentres 20. Using excenters 20, the physical steering link 14 can be adjusted in a plane that is spanned by a direction in a longitudinal direction of the towed vehicle and a direction transverse to the longitudinal direction of the towed vehicle.

[0045] Fig. 5B depicts a second example of a powered set-up actuator 15, comprising a gear set 30. The gear sets 30 physically connect the steering link 14 at its ends with a corresponding wheel group 10, preferably near the wheel steering axis 12. The gear sets 30 comprise a primary gear 31, connected to a corresponding wheel set 10, and a secondary gear 32 connected to the physical steering link 14. The gears of the gear set 30 are arranged to mesh, and are provided such that they are able to freely rotation rotate around their individual axis. For example, primary gear 31 is arranged to rotate around its axis, without translating said rotational movement to the wheel group 10. In the shown example, the secondary gear 32 is arranged to rotate in around the primary gear 31 by rotating at least one of the primary gear 31 and secondary gear 32. By rotating at least one of the gears 31, 32 the physical steering link 14, connecting the two adjacent wheel groups 10, the transfer function can be adjusted according to preference.

[0046] Fig. 5C shows yet a further example of a powered set-up actuator 15. The powered set-up actuator comprises a telescopic cylinder 41 and an auxiliary link 40 at each end of the physical steering link 14. The auxiliary link 40 connects the steering link 14 to the wheel steering axis 12. At least one of the ends of the auxiliary link 40 is hingingly connected to the steering link 14 and the wheel steering axis 12 respectively. The telescopic cylinder 41, arranged to extend and contract in its longitudinal direction, is attached at one end to the wheel steering axis 12 and at the other end to the physical steering link 40. Such a configuration, with an auxiliary link 40 and telescopic cylinder 41 is provided at both wheel groups 10. By adjusting the length of the telescopic cylinder of the powered set-up actuator 41, the transfer function of between the connected wheel groups 10 can be adjusted. In Fig. 5D a fourth example of a powered set-up actuator 15 is depicted. In the example, the steering axis 12 of connected wheel groups 10 is by a physical steering link 14 and telescopic cylinders 41. Comparable to Fig. 5C, extending and retracting the telescopic cylinders affects the transfer function between the connected wheel groups 10. In the shown example, the auxiliary links 41 from the third example have been omitted, which may result in a simpler and therefore more cost efficient configuration.

[0047] In general, the powered set-up actuator 15 is arranged to be accessory to the physical link 14 between said wheels 11. Such a set-up actuator 15 may be electrically, hydraulically or pneumatically powered. For example, the powered set-up actuators of the examples depicted in Figs. 5A and 5B may be electrically driven, for example via a motor. When such a motor is actuated, the excentre 20 and respectively the gear set 30 may be rotated. In the examples of Figs. 5C and 5D, the telescopic cylinders 41 may be hydraulically or pneumatically powered, for example using a pump.

[0048] Additionally, the powered set-up actuators 15 are arranged to operate only during set-up in response to a set-up signal. Furthermore, the powered set-up actuator 15 is locked against adjustment under external force.

[0049] Referring back to Fig. 2A and 2B an example is given in order to further elucidate the use of the powered setup-up actuator 15. As an example, a truck 200 is first used to tow the reconfigurable towed vehicle 100 having a relative small length, e.g. as depicted in Fig. 2B. The transfer function of the coupling of the wheels 11 via the physical steering link 14 has been adjusted, when the truck 200 and the towed vehicle 100 combination is standing still, by actuation of a powered set-up actuator 15 such that there is a momentary center C in which all imaginary lines drawn perpendicular to the direction of travel of the individual wheel groups 10 converge when the truck 200 tows the towed vehicle 100 around a corner. When the vehicle 100 is moving, the set-up is maintained unchanged and cannot be adjusted. As a further example, once the towed vehicle 100 has reached its destination and has been unloaded, the vehicle 100 is reconfigured for a longer load. As a result, the towed vehicle 100 is extended, e.g. as depicted in Fig. 2A, and there exists no momentary center. In order to create a, new, momentary center C in which all imaginary lines drawn perpendicular to the direction of travel of the wheel groups converge when the truck 100 and vehicle 100 moves around a corner, the towed vehicle 100 is retrofitted using the powered set-up actuator 15. The powered set-up actuator 15 is arranged to adjust the physical steering link 14 so as to change the set-up of the transfer function of the coupling of the wheels 11 of the interspaced steerable wheel groups 10. In other words, the towed vehicle 100 is retrofitted by adjusting the way the physical steering link 14 is coupling the interspaced steerable wheel groups 11, for example by adjusting the location of coupling using the example comprising the excentre 20 mechanism shown in Fig. 5A. This is done when the vehicle 100 is stationary, e.g. after the first load has been removed and before the second load is placed.

[0050] Many variations will be apparent to the skilled person in the art. For example, the skilled person in the art may use any combination or configuration of powered set-up actuators such that a desired transfer function may be obtained. Such variations are understood to be comprised within the scope of the invention as defined in the appended claims.

[0051] LIST OF REFERENCE SIGNS

[0052] 10. Steerable wheel group

[0053] 11. Wheel

[0054] 12. Wheel steering axis

[0055] 13. Central steering actuator

[0056] 14. Steering link

[0057] 15. Power set-up actuator

[0058] 17. Steering system

[0059] 20. Excentre

[0060] 30. Gear set

[0061] 31. Primary gear

[0062] 32. Secondary gear

[0063] 40. Auxiliary link

[0064] 41. Telescopic cylinder of powered set-up actuator

[0065] 100. Towed vehicle

[0066] 101. Bridging section

[0067] 200. Towin g vehicle

[0068] 201. Wheel group of towing vehicle

[0069] 202. Wheel of towing vehicle a Steering angle

[0070] D. Direction of travel

Claims

Claims1. A towed vehicle, comprising a number of interspaced steerable wheel groups that each have one or more steerable wheels, the wheels of each steerable wheel group being pivotable about a wheel steering axis of that steerable wheel group so as to include a steering angle relative to a longitudinal axis of the vehicle in response to a steering moment exerted on the wheels of the wheel group by a central steering actuator of the towed vehicle that acts on the wheels of at least one of the steerable wheel groups, said interspaced steerable wheel groups being coupled via a physical steering link included between said interspaced steerable wheel groups, which steering link transfers the steering moment of the steering actuator and couples pivoting movement of the wheels of said interspaced steerable wheel groups about their respective wheel steering axes in accordance with a transfer function, characterized in that the physical steering link between said interspaced steerable wheel groups includes a powered set-up actuator that is arranged to adjust the physical steering link so as to change the setup of the transfer function of the coupling of the wheels of the interspaced steerable wheel groups.

2. The towed vehicle of claim 1, wherein the transfer function departs from a neutral steering position of the wheels of the steerable wheel groups that allows straight travel of the vehicle along its longitudinal axis, and wherein the powered set-up actuator is arranged to adjust the physical steering link so as to change the set-up of the transfer function with maintenance of its neutral steering position.

3. The towed vehicle of claim 1 or 2, wherein the powered set-up actuator is arranged with at least two actuated degrees of freedom to adjust the physical steering link.

4. The towed vehicle of any of claims 1-3, wherein the powered setup actuator is arranged to adjust the physical steering link in at least a plane that extends transversely to the steering axis.

5. The towed vehicle of claim 4, wherein the powered set-up actuator is arranged to adjust the physical steering link in at least two perpendicular directions in said plane.

6. The towed vehicle of claims 4 or 5, wherein the powered set-up actuator is arranged to adjust the physical steering link in at least a direction transverse to the plane.

7. The towed vehicle of any of claims 1-6, wherein the powered setup actuator is arranged to adjust the physical steering link along at least two of a longitudinal axis of towed vehicle (x), a transverse axis of the towed vehicle (y) and an upright axis towed vehicle (z).

8. The towed vehicle of any of claims 1-7, wherein the powered setup actuator is arranged to operate in response to a set-up signal.

9. The towed vehicle of any of claims 1-8, wherein the powered setup actuator is arranged to act on the link during set-up only.

10. The towed vehicle according to any of claims 1-9, wherein steerable wheel groups are interspaced along a longitudinal axis of the vehicle.

11. The towed vehicle according to any of claims 1-10, wherein steerable wheel groups are interspaced transversely to a longitudinal axis of the vehicle.

12. The towed vehicle of any of claims 1-11, wherein the powered setup actuator is arranged to be accessory to the physical link between said wheels.

13. The towed vehicle of any of claims 1-12, wherein the powered setup actuator is locked against adjustment under external force.

14. The towed vehicle of any of claims 1-13, wherein the powered setup actuator is electrically, hydraulically or pneumatically powered.

15. The towed vehicle of any of claims 1-14, wherein the powered setup actuator includes an accumulator for accumulating power for the powered set-up actuator.

16. The towed vehicle of any of claims 1-15, wherein the powered setup actuator includes a motor or pump.

17. The towed vehicle of any of claims 1-16, wherein the powered setup actuator includes one or more of a spindle, a telescoping cyhnder, and an excenter.

18. The towed vehicle of any of claims 1-17, wherein the physical steering link includes a mechanical steering element, and wherein the powered set-up actuator is arranged to adjust an axial length and / or to displace a mounting point of the mechanical steering element.

19. A steering system for a towed vehicle according to any of the preceding claims, the steering system having a physical steering hnk including a powered set-up actuator that is arranged to adjust the physical steering link so as to change the set-up of the transfer function of the coupling of the wheels of the interspaced steerable wheel groups.

20. A method of setting up steering of a towed vehicle, preferably a towed vehicle according to any one of the preceding claims, the towed vehicle comprising a number of interspaced steerable wheel groups that each have one or more steerable wheels, the wheels of each steerable wheel group being pivotable about a wheel steering axis of that steerable wheel group so as to include a steering angle relative to a longitudinal axis of the vehicle in response to a steering moment exerted on the wheels of the wheel group by a central steering actuator of the towed vehicle that acts on the wheels of at least one of the steerable wheel groups, said interspaced steerable wheel groups being coupled via a physical steering link included between said interspaced steerable wheel groups, which steering link transfers the steering moment of the steering actuator and couples pivoting movement of the wheels of said interspaced steerablewheel groups about their respective wheel steering axes in accordance with a transfer function, in which method the transfer function of the coupling of the wheels of the physical steering link is adjusted by actuation of a powered set-up actuator included in the physical steering link between said interspaced steerable wheel groups that is arranged to adjust the physical steering link so as to change the set-up of the transfer function of the coupling of the wheels of the interspaced steerable wheel groups.

21. The method of claim 20, wherein the transfer function of the vehicle departs from a neutral steering position of the wheels of the steerable wheel groups that allows straight travel of the vehicle along its longitudinal axis, and wherein the powered set-up actuator is used to adjust the physical steering link so as to change the set-up of the transfer function with maintenance of its neutral steering position.

22. The method of claim 20 or 21, wherein the set-up is changed only when the vehicle is stationary.

23. The method of any of claims 20 -22, wherein the set-up is maintained unchanged when the vehicle is moving.

24. A method of retrofitting a towed vehicle, the towed vehicle comprising a number of interspaced steerable wheel groups that each have one or more steerable wheels, the wheels of each steerable wheel group being pivotable about a wheel steering axis of that steerable wheel group so as to include a steering angle relative to a longitudinal axis of the vehicle in response to a steering moment exerted on the wheels of the wheel group by a central steering actuator of the towed vehicle that acts on the wheels of at least one of the steerable wheel groups, said interspaced steerable wheel groups being coupled via a physical steering link included between said interspaced steerable wheel groups, which steering link transfers the steering moment of the steering actuator and couples pivoting movement of the wheels of said interspaced steerablewheel groups about their respective wheel steering axes in accordance with a transfer function, in which method a physical steering link between interspaced steerable wheels groups is provided with a powered set-up actuator that is arranged to adjust the physical steering link so as to change the set-up of the transfer function of the coupling of the wheels of the interspaced steerable wheel groups.

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