Brace member

Abstract

A brace 702 for a vehicle (1044, Fig. 10) comprising expandable part 704 which is expandable and / or contractable with a fluid to change a stiffness of brace 702 along its longitudinal axis 708. Part 7

Description

TECHNICAL FIELD The present disclosure relates to a brace member. Aspects of the invention relate to a brace member, to a vehicle sub-assembly, to a vehicle, to a control system for controlling adjustment of a brace member, and to a computer implemented method for controlling adjustment of a brace member. BACKGROUND During design and manufacture of a vehicle, modifications are made to achieve a desirable vehicle stiffness. Typically, such modifications involve an iterative process of removing and replacing certain components of the vehicle and testing the vehicle to check whether a desirable vehicle stiffness has been achieved. In addition to being a burdensome task, the introduction of modified or new components to a vehicle may also have undesirable effects on the noise, vibration, harshness (NVH) characteristics of the vehicle. It is an aim of the present invention to address one or more of the disadvantages associated with the prior art. SUMMARY OF THE INVENTION Aspects and embodiments of the invention provide a brace member, a vehicle sub-assembly, a vehicle, a control system for controlling adjustment of a brace member, and a computer implemented method for controlling adjustment of a brace member as claimed in the appended claims. According to an aspect of the present invention there is provided a brace member mountable across a vehicle, the brace member extending along a longitudinal axis and comprising an adjustable part, the adjustable part being adjustable so that a stiffness of the adjustable part may be changed, and a change in the stiffness of the adjustable part results in a change of a stiffness of the brace member along the longitudinal axis. In certain embodiments, the adjustable part comprises an expandable part that is expandable and / or contractable with a fluid to change a stiffness of the brace member along the longitudinal axis. According to an aspect of the present invention there is provided a brace member mountable across a vehicle, the brace member extending along a longitudinal axis and comprising an expandable part that is expandable and / or contractable with a fluid to change a stiffness of the brace member along the longitudinal axis. When mounted to the vehicle, adjustment of the stiffness of the brace member causes a change in a stiffness of the vehicle. Thus, the brace member permits the stiffness of the vehicle to be adjusted without the need for removing and replacing brace members. In certain embodiments, the brace member comprises a brace element wherein the expandable part is connected to the brace element by connectors. The brace element may be a standard known brace member (or part thereof) and its connection to the expandable part may afford the advantage of adjustability, e.g. an expandable part connected to and running parallel to a standard brace member. In certain embodiments, the brace element may not be directly adjustable. In certain embodiments, the brace element may have a greater stiffness than the expandable part. In certain embodiments, adjustment of the tension of the expandable part may cause a change in stiffness of the brace element along the longitudinal axis. In other embodiments, expansion / contraction of the expandable part may not cause a change in stiffness of the brace element along the longitudinal axis. In certain embodiments, the expandable part may comprise a cavity for receiving the fluid and a plurality of fibres surrounding the cavity, wherein the cavity is expandable by the fluid and wherein the plurality of fibres are tensioned upon expansion of the cavity. The plurality of fibres may be tensioned upon introduction of fluid in the cavity thereby changing the stiffness of the expandable part. In certain embodiments, the expandable part may comprise a liner that is impermeable to the fluid and that seals and / or defines the cavity. The use of a line may be particularly effective and / or convenient for receiving and retaining the fluid. In certain embodiments, the plurality of fibres may define the cavity. In such embodiments, a separate liner may not be required thereby reducing the number of required components. In certain embodiments, the plurality of fibres may comprise a plurality of metallic and / or composite fibres (e.g. carbon fibre). Such materials are particularly suitable for providing the required strength and ability to be tensioned by a desired amount. In certain embodiments, the plurality offibres are not encapsulated (e.g. in a resin) so that the plurality of fibres may be adjustably tensioned without damage (e.g. cracking) such encapsulating material. By “adjustably tensionable” is meant that the tension of the fibres are selectively adjustable. In certain embodiments, the plurality offibres may comprise a lubricant and / or a coating for reducing a friction between adjacent ones of the plurality offibres. Such an arrangement mitigates against problems associated with friction between fibres when moving relative to one another. In certain embodiments, the brace member may comprise a fluid reservoir for containing the fluid, the fluid reservoir being in fluid communication with the expandable part. Fluid may be provided from the fluid reservoir to the expandable part to expand the expandable part and / or so that fluid may be received from the expandable part to the fluid reservoir to contract the expandable part. The fluid may therefore be provided to and / or received from a component (i.e. the fluid reservoir) of the brace member itself. In certain embodiments, the fluid comprises a gas. A gas is a particularly effective and / or convenient fluid for expanding the expandable part. In accordance with another embodiment of the present invention, there is provided a vehicle sub-assembly comprising at least one brace member as described above. In certain embodiments, the vehicle sub-assembly comprises at least one actuator for expanding and / or contracting the expandable part with the fluid to change the stiffness of the brace member along the longitudinal axis. The vehicle sub-assembly may comprise a vehicle sub-frame, wherein the respective brace member is mounted to the vehicle subframe. Such an arrangement provides the advantage of convenience since the actuator may be actuated to cause adjustment in contrast to manual adjustments being made. In accordance with another embodiment of the present invention, there is provided a vehicle comprising at least one brace member as described above, or comprising a vehicle sub-assembly as described above. In certain embodiments, the at least one brace member crosses a centre plane of the vehicle, the centre plane extending vertically from the front of the vehicle to the rear of the vehicle. Such an arrangement permits the stiffness of the vehicle to be adjusted along a particularly advantageous axis. In accordance with another embodiment of the present invention, there is provided a control system for controlling adjustment of a brace member as described above, the control system comprising one or more processors collectively configured to: receive input data from a user interface or a sensor; determine an adjustment instruction in dependence on the input data; and output a control signal to expand and / or contract the expandable part with the fluid according to the adjustment instruction. The control system provides a convenient means for controlling adjustability of the brace member. In certain embodiments, determination of the adjustment instruction may comprise comparison of the input data with a desired or actual stiffness of the brace member. The control system comprises one or more controllers collectively comprising at least one electronic processor having an electrical input for receiving an input signal; and at least one memory device electrically coupled to the at least one electronic processor and having instructions stored therein; and wherein the at least one electronic processor is configured to access the at least one memory device and execute the instructions thereon so as to output the control signal to expand and / or contract the expandable part according to the adjustment instruction. In accordance with another aspect of the present invention, there is provided a computer implemented method for controlling adjustment of a brace member as described above, the method comprising: receiving input data from a user interface or a sensor; determining an adjustment instruction in dependence on the input data; and outputting a control signal to expand and / or contract the expandable part with the fluid according to the adjustment instruction. In certain embodiments, determining the adjustment instruction may comprise comparing the input data with a desired or actual stiffness of the brace member. In accordance with another aspect of the present invention, there is provided a computer implemented method for controlling adjustment of a brace member as described above, the method comprising: determining an adjustment instruction; and outputting a control signal to expand and / or contract the expandable part with the fluid according to the adjustment instruction. In certain embodiments, determining the adjustment instruction may comprise comparing the input data with a desired or actual stiffness of the brace member. Such methods provide convenient means for controlling adjustability of the brace member. Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and / or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and / or features of any embodiment can be combined in anyway and / or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and / or incorporate any feature of any other claim although not originally claimed in that manner. BRIEF DESCRIPTION OF THE DRAWINGS One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: FIG. 1 schematically shows a brace member in accordance with an embodiment of the present invention; FIG. 2 schematically shows a brace member in accordance with another embodiment of the present invention; FIG. 3 shows a partial perspective view of an adjustable part of a brace member in accordance with an embodiment of the present invention; FIG. 4 shows a perspective view of an adjustable part of a brace member in accordance with another embodiment of the present invention; FIG. 5 shows a partial perspective view of an adjustable part of a brace member in accordance with another embodiment of the present invention; FIG. 6 shows a partial cross-sectional view of the adjustable part of FIG. 5; FIG. 7 schematically shows a brace member in accordance with another embodiment of the present invention, wherein the brace member is in a first configuration; FIG. 8 schematically shows the brace member of FIG. 7 in a second configuration; FIG. 9 schematically shows a brace member in accordance with another embodiment of the present invention; FIG. 10 schematically shows a vehicle (shown as transparent) that comprises a vehicle sub-assembly in accordance with an embodiment of the present invention; FIG. 11 schematically shows a control system in accordance with an embodiment of the present invention; and FIG. 12 shows a method in accordance with an embodiment of the present invention. DETAILED DESCRIPTION A brace member 102 in accordance with an embodiment of the present invention is shown in FIG. 1. The brace member 102 extends along a longitudinal axis 108 and comprises an adjustable part 104 (which also extends along the longitudinal axis 108). The adjustable part 104 is adjustable so that a stiffness of the adjustable part 104 may be changed, and a change in the stiffness of the adjustable part 104 results in a change of a stiffness of the brace member 102 along the longitudinal axis 108. In the non-limiting embodiment shown in FIG. 1, the brace member 102 additionally comprises a mounting part 106 at each end of the brace member 102. The mounting parts 106 are each connected to the adjustable part 104 and are each arranged to mount the brace member 102 to a vehicle. When the brace member 102 is mounted to a vehicle, adjustment of the stiffness of the brace member 102 causes a change in a stiffness of the vehicle. Thus, the brace member 102 permits the stiffness of the vehicle to be adjusted without the need for removing or replacing brace members or parts thereof. FIG. 2 schematically shows a brace member 202 in accordance with another embodiment of the present invention. The brace member 202 also extends along a longitudinal axis 208 and comprises an adjustable part 204 (which also extends along the longitudinal axis 208). The adjustable part 204 of the brace member 202 is connected to a brace element 210 by connectors 212. The brace element 210 is a substantially rigid (i.e. stiff) component and is stiffer (i.e. has a greater stiffness) than the adjustable part 204. The stiffness of the brace element 210 is not directly adjustable. Rather, the adjustable part 204 may be adjustable so that a stiffness of the adjustable part 204 may be changed, and by virtue of the connection of the adjustable part 204 to the brace element 210 via the connectors 212, a change in the stiffness of the adjustable part 204 may result in a change of a stiffness of the brace element 210 along the longitudinal axis 208. Furthermore, this change in the stiffness of the brace element 210 along the longitudinal axis 208 results in a change of a stiffness of the brace member 202 along the longitudinal axis 208. In other embodiments, adjustment of the adjustable part 204 may not necessarily result in a change in the stiffness of the brace element 210, but nevertheless result in a change in stiffness of the brace member 202 as a whole. In the non-limiting embodiment shown in FIG. 2, the brace member 202 additionally comprises a mounting part 206 at each end of the brace member 202. The mounting parts 206 are each connected to the adjustable 5 part 204 and are each arranged to mount the brace member 202 to a vehicle. When the brace member 202 is mounted to a vehicle, adjustment of the stiffness of the brace member 202 causes a change in a stiffness of the vehicle. Thus, the brace member 202 permits the stiffness of the vehicle to be adjusted without the need for removing or replacing brace members or parts thereof. FIG. 3 shows a partial perspective view of an adjustable part 304 that may form part of the brace member 102 or brace member 202 described above (in place of adjustable part 104 or adjustable part 204) in accordance with an embodiment of the present invention. The adjustable part 304 comprises a plurality of fibres 316 that are adjustably tensionable to change the stiffness of the brace member 102 or brace member 202. In the nonlimiting embodiment shown in FIG. 3, the plurality of fibres 316 are interlaced with one another. In particular, the plurality of fibres 316 comprise a braid. In certain embodiments, such as the non-limiting embodiment shown in FIG. 3, the braid may be a cylindrical wound braid (i.e. a wound braid forming a cylindrical shape). In certain embodiments, the braid may be helically wound to form the cylindrical shape. In the non-limiting embodiment shown in FIG. 3, the adjustable part 304 additionally comprises an inner tube 314 around which the plurality of fibres 316 are arranged. The inner tube 314 may provide support to the plurality of fibres 316 (e.g. when they are in a relaxed condition). When the plurality of fibres 316 are tensioned, the plurality of fibres 316 may exert a radially inward force on the inner tube 314 such that the collective stiffness of the plurality of fibres 316 and inner tube 314 increases along their length (i.e. perpendicularly to the direction of the radial force). FIG. 4 shows a perspective view of an adjustable part 404 that may form part of the brace member 102 or brace member 202 described above (in place of adjustable part 104 or adjustable part 204) in accordance with another embodiment of the present invention. Like the adjustable part 304, the adjustable part 404 comprises a plurality of fibres 416 that are adjustably tensionable to change the stiffness of the brace member 102 or brace member 202. In the non-limiting embodiment shown in FIG. 4, the plurality of fibres 416 are interlaced with one another. In particular, the plurality of fibres 416 comprise a braid. In certain embodiments, the braid may be a cylindrical wound braid, including but not limited to a cylindrical helically wound braid. Ends of the adjustable part 404 each comprise a termination 418 that may be engaged such that tension may be applied to the plurality of fibres 416. For example, the terminations 418 may be engaged and pulled so that the plurality of fibres 416 are put into tension. Such tension changes the stiffness of the adjustable part 404 and when the adjustable part 404 forms part of a brace member and is put into tension, the adjustable part 404 in turn causes a stiffness of the brace member to change. In the non-limiting embodiment shown in FIG. 4, the terminations 418 comprise loops. In alternative embodiments, the terminations 418 may take on any other form that enables engagement in a manner that may put the plurality of fibres 416 into tension. FIG. 5 shows a partial perspective view of an adjustable part 504 that may form part of the brace member 102 or brace member 202 described above (in place of adjustable part 104 or adjustable part 204) in accordance with another embodiment of the present invention. Like the adjustable part 304 and the 404, the part 504 comprises a plurality of fibres 516 that are adjustably tensionable to change the stiffness of the brace member 102 or brace member 202. In the non-limiting embodiment shown in FIG. 5, the plurality of fibres 516 are not interlaced with one another, and instead run parallel to one another. In other embodiments, the plurality of fibres 516 may be otherwise arranged. Ends of each of the plurality of fibres 516 comprise a termination 518 that may be engaged such that tension may be applied to the plurality of fibres 516. In the non-limiting embodiment shown in FIG. 5 , a tensioner 520 is provided for applying tension to the plurality of fibres 516. The tensioner 520 comprises a body 522, one or more fixed mounting points 524 that are each fixed relative to the body, and one or more moveable mounting points 526 that are each moveable relative to the body 522. Each of the fixed mounting points 524 and the plurality of moveable mounting points 526 are configured to engage one of the terminations 518. The moveable mounting points 526 may be moved relative to the body 522 in order to put the respective fibres 516 into tension relative to the fibres 516 that are connected to the fixed mounting points 524. In certain embodiments, more than one moveable mounting point 526 may be provided and different moveable mounting points 526 may be independently moveable so as to provide a variety of different tensions in the respective fibres 516. In certain embodiments, an actuator may be provided for causing tensioning of the fibres 516. For example, the actuator may cause movement of the moveable mounting points 526. FIG. 6 shows a partial cross-sectional view of the adjustable part 504 of FIG. 5 in which it can be seen that the moveable mounting points 526 are fixed or otherwise connected to pulling elements 528 that extend through the body 522 and are coaxially arranged relative to one another and the body 522. In alternative embodiments, the fibres 516 may be tensioned by winding a part of a respective fibre 516 on a windable tensioning peg (e.g. analagous to a guitar tuning peg). In any of the embodiments described above that include fibres (i.e. the adjustable part 304, the adjustable part 404 or the adjustable part 504), the fibres may comprise metallic and / or composite fibres (e.g. carbon fibre). In certain embodiments, the fibres may comprise a lubricant and / or a coating for reducing any friction between adjacent ones of the plurality of fibres. FIG. 7 schematically shows a brace member 702 in accordance with another embodiment of the present invention. The brace member 702 extends along a longitudinal axis 708 and comprises an adjustable part 704 (which also extends along the longitudinal axis 708). The adjustable part 704 of the brace member 702 is connected to a brace element 710 by connectors 712. The brace element 710 is a substantially rigid (i.e. stiff) component and is stiffer (i.e. has a greater stiffness) than the adjustable part 704. The stiffness of the brace element 710 is not directly adjustable. Rather, the adjustable part 704 is adjustable so that a stiffness of the adjustable part 704 may be changed, and by virtue of the connection of the adjustable part 704 to the brace element 710 via the connectors 712, a change in the stiffness of the adjustable part 704 results in a change of a stiffness of the brace element 710 along the longitudinal axis 708. Furthermore, this change in the stiffness of the brace element 710 along the longitudinal axis 708 results in a change of a stiffness of the brace member 702 along the longitudinal axis 708. In other embodiments, adjustment of the adjustable part 704 may not necessarily result in a change in the stiffness of the brace element 710, but nevertheless result in a change in stiffness of the brace member 702 as a whole. In the embodiment shown in FIG. 7, the adjustable part 704 comprises an expandable part 728 that is expandable with a fluid to change a stiffness of the brace member 702 along the longitudinal axis 708. In particular, the expandable part 728 may be expanded by the introduction of a liquid or a gas to cause the expansion of the expandable part 728 and a change in stiffness therein and of the brace member 702. Similarly, a volume of fluid (i.e. liquid or gas) may be evacuated from the expandable part 728 in order to change the stiffness of the expandable part 728 and the brace member 702. In certain embodiments, the expandable part 728 comprises a cavity for receiving the fluid and a plurality of fibres surrounding the cavity. The cavity may be expanded by introduction of fluid therein and the plurality of fibres surrounding the cavity may be tensioned upon expansion of the cavity. In certain embodiments, a liner that is impermeable to the fluid may seal or define the cavity. In other embodiments, the cavity may be defined by the plurality of fibres. In such embodiments, the plurality of fibres are configured to form a layer (e.g. formed as a cylinder) that is impermeable to the fluid. In certain embodiments, the fibres may comprise metallic and / or composite fibres. In certain embodiments, the fibres may not be encapsulated in a resin (as otherwise, such resin may crack or otherwise rupture upon introduction of fluid in the cavity). In the non-limiting embodiment shown in FIG. 7, the brace member 702 comprises a fluid reservoir 732 for containing fluid. The fluid reservoir 732 is in fluid communication with the expandable part 728 in order to provide fluid to and receive fluid from the expandable part 728. FIG. 7 shows the brace member 702 in a first configuration in which the expandable part 728 is in a nonexpanded state. FIG. 8 schematically shows the brace member 702 of FIG. 7 in a second configuration in which the expandable part 728 is in an expanded state following receipt of fluid in the expandable part 728 from the fluid reservoir 732. In the second configuration, the brace member 702 has a greater stiffness along the longitudinal axis 708 compared to the first configuration. FIG. 9 schematically shows a brace member 902 in accordance with another embodiment of the present invention. The brace member 902 extends generally along a longitudinal axis 908 and comprises a plurality of adjustable parts 904 in the form of dampers 934, each extending along a damper axis 942. Each damper 934 comprises a magnetorheological and / or electrorheological damper. Such dampers 934 contain a magnetorheological and / or electrorheological fluid and are energisable (by application of a magnetic and / or electric field) to cause a change in viscosity in the fluid. Each damper 934 has a housing 936 and a piston 938 that is moveable relative to the housing 936 along the respective damper axis 942. A change in viscosity of the fluid causes a change in the resistance to movement of the piston 938 in the housing 936, thereby changing the stiffness of the respective damper 934 along its damper axis 942. Each damper 934 has a rod end connector 940 for connecting the damper 934 to a vehicle or a part of a larger sub-assembly for assembly in a vehicle. In the non-limiting embodiment shown in FIG. 9, the housings 936 of each damper 934 are connected to one another by a bracket 944 so that the dampers 934 collectively form the adjustable part 904 of the brace member 902. In alternative embodiments, the housings 936 may be connectable to a vehicle or a part of a larger sub-assembly for assembly in a vehicle, and the rod end connectors 940 may be connectable to one another. In the non-limiting embodiment of FIG. 9, four dampers 934 are provided. Each of the four dampers 934 is arranged along a damper axis 942 that is inclined relative to the longitudinal axis 908 of the brace member 902. The dampers 934 are arranged in two pairs, where in each pair, the dampers 934 are arranged end to end with one another (i.e. damper axes 942 are coaxial with one another). Energising the dampers 934 to cause a change of stiffness along each respective damper axis 942 results in a change of stiffness of the brace member 902 along the longitudinal axis 908 (and an axis that is perpendicular to the longitudinal axis 908 and in a plane that contains the longitudinal axis 908 and the damper axes 942). The arrangement of the four dampers 934 in a cross-shape (as shown in FIG. 9) is advantageous in that it provides strength and resists twisting in the plane containing the dampers 934. In alternative embodiments, any number of dampers 934 (i.e. one or more) may be provided. For example, if one damper 934 is provided, the damper 934 may be connectable to a vehicle or a part of a larger subassembly for assembly in a vehicle by the housing 936 at one end and the rod end connector 940 at the other. The single damper 934 may extend along the longitudinal axis 908 so that the damper axis 942 and the longitudinal axis 908 are coaxial with one another. In other embodiments, multiple (i.e. two or more) dampers 934 may be provided. For example, the multiple dampers 934 may be arranged end to end along the longitudinal axis 908 so that the multiple damper axes 942 may be coaxial with the longitudinal axis 908. In other embodiments, three or more dampers 934 may be provided and the damper axes 942 may be oriented so that each extends radially from a common point (as is the case in the embodiment of FIG. 9). In certain embodiments, an odd number of dampers 934 may be provided, whilst in other embodiments, an even number of dampers 934 may be provided. In certain specific embodiments, one, two, three, four, five, or six (or multiples thereof) dampers 934 may be provided. In certain embodiments, more than six dampers 934 may be provided. In certain embodiments one or more of the dampers 934 described above may be used in place of the adjustable part 104 of the brace member 102 or the adjustable part 204 or the brace member 202 described above. FIG. 10 schematically shows a transparent view of a vehicle 1044 in accordance with an embodiment of the present invention. The vehicle 1044 includes a brace member 1002. The brace member 1002 may be any brace member described above. In the non-limiting embodiment shown in FIG. 10, an actuator 1050 is provided for causing the change in stiffness of the adjustable part of the brace member 1002. The action required by the actuator 1050 will depend on the nature of the adjustable part. For example, if the adjustable part comprises a plurality of fibres, the actuator 1050 may provide a pulling force or other action that causes some or all of the plurality of fibres to be tensioned. If the adjustable part comprises a magnetorheological and / or electrorheological damper, then the actuator 1050 may energise the damper so as to provide a magnetic and / or electric field and cause the stiffness of the damper to change. The actuator 1050 and the brace member 1002 form a vehicle sub-assembly 1048. In the non-limiting embodiment shown in FIG. 10, the vehicle sub-assembly 1048 is connected to a vehicle sub-frame 1046 of the vehicle 1044. In its assembled position, the brace member 1002 crosses a centre plane of the vehicle 1044, where the centre plane extends both vertically and horizontally from a front end 1044a of the vehicle 1044 to a rear end 1044b of the vehicle 1044. In the non-limiting embodiment shown in FIG. 10, the brace member 1002 extends between the rear wheels 1052 of the vehicle 1044. A stiffness of (at least part of) the vehicle 1044 is determined by the stiffness of the brace member 1002. Therefore, adjustment of the stiffness of the brace member 1002 causes a change in the stiffness of (at least part of) the vehicle 1044. Whilst only one brace member 1002 is shown in FIG. 10, in other embodiments, the vehicle 1044 may be provided with more than one brace member 1002 (e.g. disposed between the front two wheels). The vehicle 1044 comprises a control system 1154, as illustrated in FIG. 11, for controlling one or more functions of the vehicle 1044. The control system 1154 comprises one or more processors 1156 which are collectively configured to perform a method 1202 according to an embodiment of the invention, as described further below with reference to FIG. 12. The vehicle 1044 is a wheeled i.e. land-going vehicle, although it will be appreciated that embodiments of the invention may be used in other types of vehicles such as watercraft and aircraft. The illustrated control system 1154 comprises processing means 1156 and memory means 1158. The processing means 1156 may be one or more electronic processing devices 1156 which operably executes computer-readable instructions, herein after called a processor 1156. The memory means 1158 may be one or more memory devices 1158, herein after called a memory 1158. The memory 1158 is electrically coupled to the processor 1156. The memory 1158 is configured to store instructions, and the processor 1156 is configured to access the memory 1158 and execute the instructions stored thereon. The memory 1158 may also store data for use in the method 1202 as will be explained. The control system 1154 comprises an input means 1160 and an output means 1162. The input means 1160 may comprise an electrical input 1160 of the control system 1154. The output means 1162 may comprise an electrical output 1162 of the control system 1154. The input 1160 is arranged to receive an electrical signal 1164 which may originate from one or more sensors or other control systems of the vehicle 1044. The electrical signal 1164 may be indicative of one or more of an operability of a wireless interface of the vehicle 1044, a state of the vehicle 1044 or one or more subsystems thereof, and an environment of the vehicle 1044, as will be explained. The output 1162 is arranged to output a control signal 1166 for adjusting at least part of a brace member. Such adjustment may be via an actuator as described above (e.g. the control signal 1166 may control the actuator which adjusts at least part of the brace member). In some embodiments the input 1160 and output 1162 may be integrated into an I / O unit or interface of the control system 1154. The I / O interface may be a network interface of the control system 1154 for connecting the control system 1154 to a network system or bus of the vehicle 1044 such as a communications bus for receiving data from and communicating data to sensors, control systems or control units of the vehicle 1044 as would be understood by the skilled person. FIG. 12 illustrates a method 1202 according to an embodiment of the invention. The method 1202 may be a computer implemented method. The method 1202 is a method of controlling adjustment of at least part of a brace member. Such adjustment may be via an actuator as described above (e.g. the method 1202 may control the actuator which adjusts at least part of the brace member). The method 1202 may be performed by the control system 1154 illustrated in FIG. 11. The memory 1158 may comprise computer-readable instructions which, when executed by the processor 1156, cause the processor 1156 to perform the method 1202 according to an embodiment of the invention. The method 1202 starts at block 1204 and comprises a block 1206 comprising receiving input data from a user interface or a sensor. The input data may, for example, relate to a condition of the vehicle 1044 or a condition of the surface being driven on which may result in a desire to adjust a stiffness of the vehicle 1044. The input data may comprise the electrical signal 1164 and be received in the control system 1154 by the input means 1160. The method 1202 comprises a block 1208 comprising determining an adjustment instruction in dependence on the input data received in block 1206. The adjustment instruction may include parameters relating to an adjustment to be made to the brace member in dependence on the input data received in block 1206. For example, the parameters may include an adjustment distance and an adjustment direction of the brace member or part thereof (e.g. movement of part of the brace member (e.g. ends of fibres) 2 mm along the y-axis). The step of determining the adjustment instruction may be performed in the processor 1156, optionally making use of the memory 1158. In certain embodiments, the step of determining the adjustment instruction may comprise comparison of the input data with a desired stiffness of the brace member. In particular, the input data may be indicative of the current stiffness (or other condition) of the brace member, and the adjustment instruction may be indicative of the adjustment required to change the stiffness (or other condition) of the brace member so that the desired stiffness is achieved. In certain embodiments, the step of determining the adjustment instruction may comprise comparison of the input data with an actual stiffness of the brace member. In particular, the input data may be a desired stiffness (e.g. input by the user) of the brace member, and the adjustment instruction may be indicative of adjustment required to change the stiffness of the brace member from the actual stiffness to the desired stiffness. The method 1202 comprises a block 1210 comprising outputting a control signal to adjust at least part of the 5 brace member according to the adjustment instruction. The output signal may comprise the control signal 1166 that is outputted by the output means 1162. The control signal may cause adjustment of at least part of a brace member in accordance with the adjustment instruction. Such adjustment may be via an actuator as described above (e.g. the control signal may be received by the actuator and cause it to adjust at least part of the brace member in accordance with the adjustment instruction). 10 The method 1202 terminates at block 1212. It will be appreciated that various changes and modifications can be made to the present invention without departing from the scope of the present application, 15

Claims

1. A brace member mountable across a vehicle, the brace member extending along a longitudinal axis and comprising an expandable part that is expandable and / or contractable with a fluid to change a stiffness of the brace member along the longitudinal axis.

2. A brace member according to claim 1, comprising a brace element wherein the expandable part is connected to the brace element by connectors.

3. A brace member according to claim 1 or 2, wherein the expandable part comprises a cavity for receiving the fluid and a plurality of fibres surrounding the cavity, wherein the cavity is expandable by the fluid and wherein the plurality of fibres are tensioned upon expansion of the cavity.

4. A brace member according to claim 3, wherein the expandable part comprises a liner that is impermeable to the fluid and that seals and / or defines the cavity.

5. A brace member according to claim 3, wherein the plurality of fibres define the cavity.

6. A brace member according to any of claims 3, 4 or 5, wherein the plurality of fibres comprise aplurality of metallic and / or composite fibres.

7. A brace member according to any of claims 3 to 6, wherein the plurality of fibres are not encapsulated in a resin.

8. A brace member according to any preceding claim, comprising a fluid reservoir for containing the fluid, the fluid reservoir being in fluid communication with the expandable part.

9. A brace member according to any preceding claim, wherein the fluid comprises a gas.

10. A vehicle sub-assembly comprising at least one brace member according to any preceding claim and at least one actuator for expanding and / or contracting the expandable part with the fluid to change the stiffness of the brace member along the longitudinal axis.

11. A vehicle sub-assembly comprising at least one brace member according to any of claims 1 to 9 and a vehicle sub-frame, wherein the respective brace member is mounted to the vehicle sub-frame.

12. A vehicle comprising at least one brace member according to any of claims 1 to 9, or comprising a vehicle sub-assembly according to claim 10 or 11.13 A vehicle according to claim 12, wherein the at least one brace member crosses a centre plane of the vehicle, the centre plane extending vertically, and horizontally from the front of the vehicle to the rear of the vehicle.5 14. A control system for controlling adjustment of a brace member according to any of claims 1 to 9, thecontrol system comprising one or more processors collectively configured to:receive input data from a user interface or a sensor;determine an adjustment instruction in dependence on the input data; andoutput a control signal to expand and / or contract the expandable part with the fluid according to the 10 adjustment instruction.

15. A computer implemented method for controlling adjustment of a brace member according to any of claims 1 to 9, the method comprising:receiving input data from a user interface or a sensor;15 determining an adjustment instruction in dependence on the input data; andoutputting a control signal to expand and / or contract the expandable part with the fluid according to the adjustment instruction.

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