Ride height control system

Abstract

A ride height control system is described The ride height control system is for use in a vehicle comprising an active downforce system configured to generate a downforce acting on the vehicle. The ride height control system comprises a suspension system for supporting a sprung mass of the vehicle, wherein the suspension system comprises an actuator operable to control a ride height of the vehicle. A sensor is configured to detect a parameter indicative of a downforce generated by the active downforce system. The ride height control system further comprises a controller configured to operate the actuator as a function of an output signal from the sensor.

Description

[0001] RIDE HEIGHT CONTROL SYSTEM

[0002] Field of the Invention

[0003] The present invention relates to a ride height control system for controlling the ride height of a vehicle having an active downforce system.

[0004] Background

[0005] One technique for improving a vehicle’s grip (or traction) on a ground surface on which it is driving, such as a road, is to generate a downforce which acts on the vehicle and causes the vehicle to be pressed towards the ground surface. Such a downforce may increase tyre adhesion with the ground surface, enabling the vehicle to travel around bends at greater speeds without losing traction. This can also enable the tyres to transmit greater longitudinal forces to the ground, which may improve acceleration and deceleration of the vehicle.

[0006] Typically, a downforce may be generated using aerodynamic characteristics of the vehicle. The vehicle may include one or more surfaces which are configured to generate a downforce when air flows over those surfaces as the vehicle moves. As an example, the vehicle may include an aerofoil (or wing) which is configured to generate a downforce that presses the vehicle towards the ground surface as the vehicle drives over the ground surface. The aerofoil may function based on the same principles as an aircraft wing, except that the aerofoil is arranged to generate a negative lift, i.e. a force directed towards the ground surface.

[0007] Another method for generating a downforce that acts on a vehicle is to use a so-called active downforce system which is configured to create a low-pressure region underneath the vehicle. Such an active downforce system can for example include an airflow generator such as a fan which is arranged cause an air flow in a region underneath the vehicle, to thereby create a low-pressure region underneath the vehicle. For example, the air flow generator may act to remove air from the region underneath the vehicle, which may be defined at least in part by a skirt which is located underneath the vehicle. As a result of the low pressure region underneath the vehicle, a downforce is generated which acts on the vehicle and provides an increased grip of the vehicle on the ground surface.

[0008] Summary of the Invention

[0009] At its most general, the present invention provides a ride height control system for a vehicle having an active downforce system, where the ride height control system is configured to control a ride height of the vehicle in response to a downforce generated by the downforce system. In this manner, the ride height of the vehicle can be actively controlled, e.g. to compensate for changes in loading of vehicle suspension caused by the generated downforce. An active downforce system can typically generate downforces of the order of the weight of the vehicle, in some cases up to two or more times the weight of the vehicle. Such downforces dramatically affect a load experienced by a suspension system of the vehicle, in turn affecting the ride height of the vehicle. By providing the vehicle with a system that controls ride height in response to the generated downforce, it is possible to maintain a suitable ride height of the vehicle, both when the downforce system is activated and deactivated. For example, the ride height control system can act to compensate for the increase in load experience by the suspension system when the downforce system is activated, so as to maintain a desired ride height. This may improve vehicle handling as well as driver comfort when the downforce system is activated.

[0010] Additionally, the ride height of the vehicle will typically affect a magnitude of the downforce generated by the active downforce system. Thus, adjusting the ride height of the vehicle provides a mechanism for rapidly and reliably controlling the generated downforce. In this manner, taking the generated downforce as an input (e.g. in a feedback loop), the ride height control system can adjust the ride height of the vehicle to achieve a target downforce and / or adjust the downforce in a desired manner.

[0011] According to a first aspect of the invention, there is provided a ride height control system for a vehicle comprising an active downforce system configured to generate a downforce acting on the vehicle, the ride height control system comprising: a suspension system for supporting a sprung mass of the vehicle, wherein the suspension system comprises an actuator operable to control a ride height of the vehicle; a sensor configured to detect a parameter indicative of a downforce generated by the active downforce system; and a controller configured to operate the actuator as a function of an output signal from the sensor.

[0012] The suspension system may be any suitable suspension system for a vehicle.

[0013] The suspension system may be configured to couple the sprung mass of the vehicle to wheels of the vehicle, to thereby support the sprung mass.

[0014] In some cases, the suspension system may comprise a pushrod or a pull-rod suspension system. The suspension may be a multi-link suspension system. Such a multi-link suspension system may comprise multiple (e.g. three or more) linkages (or control arms) connected to each upright assembly of the vehicle.

[0015] Other examples of suspension systems that can be used include MacPherson strut systems, double wishbone suspension systems, torsion beam or trailing arm suspension systems, semi-active suspension systems, fully active suspension systems, hydraulic suspension systems, magnetorheological dampers, and / or other adaptive suspension technologies.

[0016] The suspension system may comprise a front suspension system arranged to connect the sprung mass of the vehicle to front wheels of the vehicle, and / or a rear suspension system arranged to connect the sprung mass to rear wheels of the vehicle.

[0017] Here, the sprung mass of the vehicle refers a portion of a total mass of the vehicle which is supported by (e.g. suspended on) the suspension system. The sprung mass may typically include a body of the vehicle, chassis, motor, transmission, and internal components, as well as any passengers and cargo of the vehicle. The sprung mass may also comprise the active downforce system. Unsprung mass of the vehicle, i.e. a portion of the total mass of the vehicle which is not supported by (e.g. suspended on) the suspension system, may typically include the wheels, tires, brake assemblies. The suspension system may be configured to provide a reaction force opposing a load exerted on the suspension system. The load exerted on the suspension system may comprise a first component resulting from a weight of the sprung mass of the vehicle, and a second component resulting from a downforce generated by the active downforce system. The ride height of the vehicle may correspond to a height at which the reaction force from the suspension system balances the total load exerted on the suspension system.

[0018] The suspension system may comprise one or more springs arranged to provide the reaction force. For example, the load exerted on the suspension system may cause the one or more springs to be compressed, resulting in the reaction force from the one or more springs. The suspension system may further comprise a linkage assembly in which the one or more springs are mounted, and arranged to couple the sprung mass of the vehicle to the wheels.

[0019] The suspension system comprises an actuator for controlling the ride height of the vehicle. In other words, the actuator is configured to adjust the suspension system, to control the ride height of the vehicle. The actuator may, for example, be operable to adjust one or more parameters of the suspension system, to thereby control the ride height. For example, various parameters of the suspension system may affect ride height of the vehicle, such as a stiffness of the suspension system, properties of the one or more springs (such as preload, compression and / or spring constant of the one or more springs), and / or spacings between linkages in the suspension system. In some cases, the actuator may be arranged to vary a volume of a fluid chamber (e.g. hydraulic chamber) in the suspension system, to control the ride height. Accordingly, the actuator can be adapted to adjust one or more suitable parameters of the suspension system for controlling the ride height of the vehicle.

[0020] The actuator may be coupled to one or more elements of the suspension system to adjust the one or more parameters of the suspension system and control the ride height. As noted above, various different types of suspension system may be used. Accordingly, the manner in which the actuator is coupled to the suspension system may be adapted to the specific type of suspension system and parameter(s) to be varied. For instance, the actuator may be coupled to one or more elements of the suspension system such as a spring perch, damper, rocker arm, and / or fluid (hydraulic) chamber, e.g. depending on a type and geometry of the suspension system.

[0021] In some cases, the actuator may in fact comprise multiple actuators, each for adjusting a respective parameter (or setting) of the suspension system. For instance, different actuators may be used to adjust a ride height and a spring constant or stiffness of the suspension system.

[0022] Any suitable type of actuator may be used, various examples of which are provided below.

[0023] The actuator may be configured to operate in response to a control signal received from the controller.

[0024] Herein, ride height of the vehicle may refer to a height of an underside of the vehicle above a ground surface on which the vehicle is located.

[0025] The sensor is configured to detect a parameter indicative of the downforce generated by the active downforce system. In other words, the sensor is arranged to detect a parameter that changes in response to the generated downforce, to provide an indication of the generated downforce (e.g. of a magnitude of the generated downforce). The sensor may be arranged to directly or indirectly detect (e.g. measure) the downforce generated by the active downforce system.

[0026] In some cases, multiple parameters indicative of the generated downforce may be detected, e.g. using multiple respective sensors. The multiple parameters can then be used by the controller to determine (estimate) a magnitude of the downforce, and to control operation of the actuator as a function of the determined downforce. As discussed below, various parameters of the vehicle, active downforce system, and the suspension system can be used to provide an indication of the generated downforce.

[0027] Accordingly, any combination of one or more of the disclosed parameters can be used in implementations of the invention.

[0028] The detected parameter may be indicative of the load exerted on the suspension system resulting from the active downforce system. Thus, for example, the sensor can be used to detect when the active downforce system is activated, and / or when there is a change in the downforce generated by the active downforce system, as this will result in a change in the load exerted on the suspension system.

[0029] Various parameters of the vehicle, suspension system, and / or active downforce system can provide an indication of downforce and / or the load exerted on the suspension system, several examples of which are provided below.

[0030] In some cases, the parameter detected by the sensor may be indicative of a total (or combined) load on the suspension system, the total load comprising a first component resulting from a weight of the sprung mass of the vehicle, and a second component resulting from a downforce generated by the active downforce system. For example, the sensor may be configured to detect the total load exerted on the suspension system, either directly (e.g. using one or more weight sensors in the suspension system) and / or indirectly (e.g. using one or more strain sensors in the suspension system, or measuring spring compression or relative displacement between parts of the suspension system). Alternatively, the parameter detected by the sensor may be indicative of the second component resulting from the downforce system. For example, the sensor may be configured to detect an operating parameter of the downforce system, which may provide an indication of the generated downforce.

[0031] In some cases, the sensor may be configured to detect a displacement of suspension system, e.g. as a result of the load exerted on the suspension system. The sensor may, for example, be arranged to detect a relative displacement between a chassis and a wheel hub of the vehicle, to determine displacement of the suspension system.

[0032] The parameter detected by the sensor may be the ride height of the vehicle, as vehicle ride height may be indicative of the downforce (and / or load exerted on the suspension system). This may facilitate control of the ride height of the vehicle. For example, the sensor may comprise a distance (or displacement) sensor, such as a laser-based distance sensor, configured to detect a distance between the underside of the vehicle and the ground surface. The distance sensor may, for instance, be mounted on an underside of the vehicle. Examples of sensor types that can be used to detect the ride height include laser-based sensors, optical displacement sensors, ultrasonic sensors, and radar. The parameter detected by the sensor may comprise a pressure within a pneumatic or hydraulic chamber of the suspension system, e.g. the sensor may comprise a pressure sensor.

[0033] The parameter detected by the sensor may be indicative of a motion of the vehicle, from which the downforce can be inferred. For example, the sensor may comprise an accelerometer and / or an inertial measurement unit (IMU).

[0034] Furthermore, as discussed further below, the sensor may be configured to detect an operating parameter of active downforce system, which may be indicative of the load exerted on the suspension system.

[0035] The sensor is configured to provide an output signal to the controller. The output signal may be indicative of the detected parameter. For example, the output signal may be indicative of a value of the detected parameter.

[0036] The controller may be communicatively coupled to the sensor, via a suitable wired or wireless connection, to receive the output signal from the sensor. The controller is then configured to operate the actuator to adjust the suspension system as a function of (i.e. based on) the output signal from the sensor, to thereby control the ride height. In this manner, the controller can automatically adjust the suspension system in real-time in response to changes in the load on the suspension system. For example, when the downforce system is activated, this may result in a sudden increase in the load experienced by the suspension system. The controller can then operate the actuator to adjust the suspension system in response to the increased load, e.g. to compensate for the increased load and maintain a desired ride height of the vehicle. Likewise, when there are changes in the generated downforce, resulting changes in the load on the suspension system will be detected by the sensor, enabling the controller to react in realtime.

[0037] The controller may be configured to implement a control algorithm (or control function) for controlling the actuator, which takes as an input the output signal from the sensor, and which provides in response control instructions for the actuator. The control instructions may comprise, for example, a control signal for controlling the actuator.

[0038] In some cases, the ride height control system may comprise multiple sensors, each of which is configured to detect a respective parameter indicative of the downforce and / or load exerted on the suspension system. For instance, the multiple sensors may be arranged to detect multiple ones of the various parameters mentioned above. The controller may then be configured to operate the actuator as a function of output signals received from each of the multiple sensors. In other words, the algorithm mentioned above may take as inputs the output signals from the multiple sensors. Using multiple sensors in this manner may improve an accuracy with which the controller can determine the load exerted on the suspension system, improving a responsiveness of control of the actuator. This also enables measurements from the different sensors to be used to cross-check one another.

[0039] In some cases, there may be multiple (e.g. two or more) sensors configured to detect a same parameter. For example, there may be two or more sensors configured to detect a ride height of the vehicle. Use of multiple sensors for detecting the same parameter may improve a safety and accuracy of the ride height control system, by providing redundancy and enabling the different sensors to be cross-checked against one another.

[0040] The ride height control system may further comprise an obstacle sensor configured to detect obstacles on the ground surface in front of the vehicle. The controller may then further be configured to operate the actuator as a function of an output signal from the obstacle sensor. In this manner, the ride height of the vehicle can automatically be adjusted in response to detection of an obstacle in front of the vehicle. This may serve to avoid damage to the underside of the vehicle and the active downforce system. As an example, the obstacle sensor may comprise a forward-facing sensor at a front of the vehicle, such as a proximity sensor, laser scanner, or Light Detection and Ranging (LiDAR) scanner. The obstacle sensor may be used in combination with the sensor(s) for detecting a parameter indicative of the load exerted on the suspension system, to provide rapid and reactive control of the suspension system.

[0041] The controller may comprise any suitable control device capable of implementing the control steps described herein. For example, the controller may be implemented using a suitable microcontroller or computing device. The controller may be configured to transmit a control signal to the actuator, for operating the actuator.

[0042] The ride height control system can be implemented in a vehicle comprising an active downforce system. The active downforce system may be a powered system, e.g. having a powered airflow source (such as a fan, turbine, vacuum generator, engine exhaust or the like) which is configured to generate a downforce acting on the vehicle. In particular, the air flow generator may be configured to produce an airflow for generating a downforce acting on the vehicle. The airflow generator may also be referred to as an airflow source or as a pressure source.

[0043] Various types of active downforce system may be used with the ride height control system of the invention.

[0044] In some cases, the airflow generator may be configured to generate a pressure differential between a region under the vehicle and a surrounding atmosphere, to thereby generate the downforce. For example, the airflow generator may be configured to evacuate air from the region under the vehicle, to generate the pressure differential. As another example, the airflow generator may be arranged to cause an airflow in a diffuser on an underside of the vehicle, to generate a low pressure region under the vehicle.

[0045] The airflow generator may be a dedicated airflow generator (or pressure source). In other words, the airflow generator may be configured to be driven (or controlled) independently from a main engine of the vehicle. Alternatively, the airflow generator may be driven by (or form part of) the main engine of the vehicle. For example, the active downforce system may comprise a blown diffusion system, where exhaust gas from the engine is blown into a diffuser on an underside of the vehicle.

[0046] The controller may be configured to operate the actuator to maintain a predetermined ride height of the vehicle. In this manner, the actuator can be automatically controlled to adjust the suspension system, e.g. to compensate for changes in the load exerted on the suspension system resulting from the active downforce system, in order to maintain the predetermined ride height. This may avoid sudden or unwanted changes in vehicle ride height as a result of activation of the downforce system and / or changes in the generated downforce. This may in turn result in improved vehicle handling and driver comfort across a variety of operating conditions of the active downforce system.

[0047] The predetermined ride height may correspond to a setpoint of the ride height control system. In some cases, the ride height of the vehicle may be maintained in a predetermined range around the setpoint. By way of example, the controller may be configured to perform a Proportional-lntegral-Derivative (PID) control loop for maintaining the predetermined ride height. This may serve to minimise overshooting of the predetermined ride height, and reduce settling time of the system.

[0048] In some cases, the predetermined ride height may be set automatically by the controller. Additionally or alternatively, the predetermined ride height may be set (selected) by a user.

[0049] The controller may be configured to operate the actuator to at least partially compensate for the load exerted on the suspension system resulting from the downforce system. This may serve to reduce or avoid changes in height of the vehicle as a result of the downforce generated by the active downforce system. In particular, such active compensation as a function of the output of the sensor can facilitate maintained the predetermined ride height of the vehicle.

[0050] The controller may be configured to operate the actuator in accordance with a predetermined ride height profile, the ride height profile providing an indication of target ride height as a function of output signal from the sensor.

[0051] The actuator may be operable to adjust a stiffness of the suspension system. In this manner, the controller can control the stiffness of the suspension system as a function of the output signal from the sensor. This enables the stiffness of the suspension system to be dynamically adapted to the amount of downforce generated by the active downforce system. For example, the stiffness of the suspension system can be adjusted to compensate for the load exerted on the suspension system resulting from the downforce system, which may reduce or avoid changes in ride height of the vehicle in response to operation of the active downforce system.

[0052] For instance, the controller may be configured to operate the actuator to increase the stiffness of the suspension system in response to an increase in the load exerted on the suspension system (as detected by the sensor) resulting from the active downforce system, e.g. as a result of activation of the downforce system and / or an increase in the generated downforce. The controller may be configured to increase the stiffness of the suspension system in response to activation of the active downforce system. The increased stiffness of the suspension system may provide enhanced handling of the vehicle under the increased load caused by the active downforce system. For example, the increased stiffness of the suspension system may serve to ensure that suspension system is capable of supporting the increased load, and that a suitable ride height is maintained. In a similar manner, the controller may be configured to operate the actuator to decrease the stiffness of the suspension system in response to a decrease in the load exerted on the suspension system as a result of the active downforce system. For example, when the active downforce system is switched off or the generated downforce is decreased, the stiffness of the suspension system may be reduced. This may provide a suitable level of compliance of the suspension system for the reduced load, and reduce or avoid increases in ride height when the active downforce system is switched off.

[0053] The controller may be configured to operate the actuator in accordance with a predetermined stiffness profile, the stiffness profile providing an indication of target stiffness of the suspension system as a function of output signal from the sensor.

[0054] The stiffness of the suspension system determines a change in ride height as a function of a change in the load exerted on the suspension system. The stiffness of the suspension system may also be referred to as a spring constant of the suspension system.

[0055] Accordingly, the controller can operate the actuator to control the stiffness of the suspension system, to thereby control ride height of the vehicle.

[0056] Various means may be provided for adjusting the stiffness of the suspension system. As one example, the actuator may comprise a spring having an adjustable stiffness (spring constant). As another example, the suspension system may comprise two springs, and the actuator may be operable between a first state where only one of the springs contributes to the reaction force, and a second state where the two springs are coupled in parallel to increase the stiffness of the suspension system.

[0057] The controller may be configured to operate the actuator to control the downforce generated by the active downforce system. In this manner, the ride height of the vehicle can be controlled to adjust the magnitude of the downforce. The sensor can be used as feedback by the controller when operating the actuator, e.g. in order to achieve a target downforce and / or a desired change in the downforce of the active downforce system. For example, the controller may be configured to operate the actuator to maintain a predetermined downforce, and / or the controller may be configured to operate the actuator to vary (adjust) the downforce.

[0058] The magnitude of the downforce generated by active downforce system is dependent on the ride height of the vehicle. In particular, the ride height of the vehicle determines a speed of airflow under the vehicle relative to an airflow over the vehicle, such that reducing the ride height accelerates the airflow under the vehicle relative to the airflow over the vehicle and increases downforce. Where the airflow generator is arranged to remove air from a region under the vehicle, the airflow generator contributes to acceleration of the airflow under the vehicle, thus increasing the downforce. Accordingly, the magnitude of the downforce generated with the active downforce system can be adjusted by adjusting the ride height of the vehicle.

[0059] Where the airflow source is arranged to cause an airflow in a diffuser on the underside of the vehicle, the ride height of the vehicle may change a size of a constriction between the underside of the vehicle and the ground surface. Thus, reducing ride height of the vehicle may reduce the size of the constriction, contributing to acceleration of the airflow under the vehicle and hence a reduction in pressure under the vehicle, such that the generated downforce is increased. On the other hand, increasing ride height of the vehicle may increase the size of the constriction, reducing airflow speed under the vehicle which in turn results in a reduced magnitude of the downforce. The suspension system may comprise a first linkage and a second linkage, the ride height of the vehicle being dependent on a spacing between the first linkage and the second linkage; and the actuator may be operable to adjust the spacing between the first linkage and the second linkage. In this manner, the actuator can be operated to directly control the ride height of the vehicle, by adjusting the spacing between the first and second linkages. For example, the actuator may be operated to maintain a predetermined spacing between the first and second linkage, e.g. to maintain the predetermined ride height of the vehicle. The actuator may be connected between the first linkage and the second linkage.

[0060] The first linkage and the second linkage may be arranged such that they move relative to one another when the ride height of the vehicle changes. The specific arrangement of the first linkage and the second linkage may vary, depending on a type and configuration of the suspension system. The first and second linkages may be arranged such that an increase in the spacing between the first and second linkages results in an increase in the ride height. In other words, increasing the spacing between the first and second linkages acts to push the sprung mass upwards away from the wheels.

[0061] The actuator may be operable to push the first linkage and the second linkage apart, i.e. to increase the spacing between the first and second linkages.

[0062] One or more springs of the suspension system may be connected between the first linkage and the second linkage such that the one or more springs change length in response to a change in spacing between the first and second linkage, the one or more springs being arranged to provide a reaction force opposing the load exerted on the suspension system. For example, the one or more springs may be arranged to be compressed in response to a load exerted on the suspension system. Accordingly, by adjusting the spacing between the first and second linkages, the actuator may adjust a compression of the one or more springs.

[0063] In some cases, the first linkage and the second linkage may be arranged such that the spacing between therebetween is adjustable in a direction substantially parallel to a ground surface on which the vehicle is located. This may contribute to reducing a height of the suspension system, and facilitate integrating the suspension system with vehicles having a small form factor.

[0064] By way of example, suspension system may comprise a pushrod suspension system. The first linkage may then comprise a first rocker (e.g. bell crank) which is pivotably connected to a first pushrod of the suspension system, the first rocker being configured to be pivotably coupled to a first pivot joint on the sprung mass of the vehicle on a first (e.g. left-hand) side of the vehicle. The second linkage may comprise a second rocker (e.g. bell crank) which is pivotably connected to a second pushrod of the suspension system, the second rocker being configured to be pivotably coupled to a second pivot joint on sprung mass of the vehicle on a second (e.g. right-hand) side of the vehicle. The actuator may be coupled to an end of the first rocker and an end of the second rocker, to control a spacing between the ends of the first and second rockers. Adjusting the spacing between the ends of the first and second rockers with the actuator causes the first and second rockers to pivot about the first and second pivot joint, respectively, resulting in a change of height of the sprung mass of the vehicle. The one or more springs may be connected between the ends of the first and second rockers. The first pushrod may be coupled to a first upright (or upright assembly) of the vehicle, and the second pushrod may be coupled to a second upright (or upright assembly) of the vehicle.

[0065] The ride height control system may comprise a first spring arranged to contribute to a reaction force of the suspension system opposing the load exerted on the suspension system, wherein the actuator is operable to adjust a length of the first spring. For example, the actuator may be operable to compress the first spring. Adjusting the length of the first spring results in a change in the contribution to the reaction force from the first spring, which in turn affects the ride height of the vehicle. For example, increasing compression of the first spring may result in an increased contribution to the reaction force from the first spring, resulting in an increased vehicle ride height. On the other hand, reducing or removing compression of the first spring may result in a reduced contribution to the reaction force from the first spring, resulting in a decreased vehicle height. Thus, the actuator can be operated to adjust compression of the first spring, to thereby control the ride height of the vehicle.

[0066] The controller may be configured to operate the actuator to compress (or increase a compression of) the first spring in response to an increase in the load exerted on the suspension system. Thus, the first spring may be compressed in response to activation of the downforce system and / or an increase in the generated downforce, e.g. to compensate for the downforce.

[0067] The first spring may be coupled between the first linkage and the second linkage of the suspension system. For example, the first spring may be coupled between the end of the first rocker and the end of the second rocker.

[0068] The first spring may comprise any suitable type of spring. For instance, the first spring may comprise one or more of a coil spring, a disc spring, a pneumatic spring, and a hydraulic spring. The first spring may have a fixed spring constant (spring rate) or a variable spring constant.

[0069] The actuator may comprise a linear actuator connected between the first linkage and the second linkage. This may facilitate adjusting the spacing between the first linkage and the second linkage with the actuator. Where a pushrod suspension system is used, the linear actuator may be connected between the end of the first rocker and the end of the second rocker.

[0070] The linear actuator and the first spring may be connected in series between the first linkage and the second linkage. In this manner, the linear actuator can act to adjust a length of the spring (e.g. compress the spring), and / or adjust the spacing between the first linkage and the second linkage. This may contribute to providing a compact arrangement of the suspension system.

[0071] An assembly comprising the linear actuator and the first spring may be arranged to extend across a centreline of the vehicle. This may contribute to reducing a height of the suspension system and of the vehicle. For example, a direction of extension of the linear actuator may be arranged to be substantially parallel to the ground surface on which the vehicle is disposed.

[0072] The linear actuator may comprise a shaft and an engagement element (e.g. flange) mounted on the shaft. The first spring may then be arranged (mounted) on the shaft. The actuator may be operable to move the engagement element along the shaft to compress the first spring. The first spring may have a fixed end, and a free end which is engageable by the engagement element of the actuator. Thus, the actuator can be operated to compress the spring between the engagement element and the fixed end of the spring.

[0073] The actuator may be movable between an engaged state where the actuator is engaged with an end (e.g. free end) of the first spring, and a disengaged state where the actuator is disengaged from the end of the first spring; and when the actuator is in the disengaged state, the first spring does not contribute to the reaction force. In this manner, the actuator can be operated to control whether or not the first spring contributes to the reaction force of the suspension system. When the actuator is in the engaged state, the first spring can become compressed due to its engagement with the actuator, such that it contributes to the reaction force of the suspension system. In particular, in the engaged state, the first spring may become compressed in response to the load or an increase in the load exerted on the suspension system. In some cases, the actuator may be arranged to compress the first spring in the engaged state.

[0074] On the other hand, when the actuator is in the disengaged state, the first spring may be in an uncompressed state, and so does not provide any reaction force. The actuator may be arranged such that there is a gap between the actuator and the end of the first spring in the disengaged state. This may avoid the first spring becoming compressed, e.g. as the suspension system moves (bounces) up and down.

[0075] Accordingly, switching between the disengaged and engaged states enables the stiffness of the suspension system to be varied. In particular, the suspension system will have a higher stiffness in the engaged state, as the first spring is arranged to contribute to the reaction force, whereas in the disengaged state the suspension system will have a lower stiffness, as the first spring does not contribute to the reaction force.

[0076] The controller may be configured to put the actuator in the disengaged state when the active downforce system is in an off state. In this manner, the suspension system may have a lower stiffness when the downforce system is not generating a downforce. The controller may be configured to put the actuator in the engaged state when the active downforce system activated. In this manner, the suspension system may have a higher stiffness when the downforce system is generating a downforce. Thus, the system can rapidly switch between states of low and high stiffness, in response to operation of the downforce system.

[0077] The first spring may comprise a progressive spring constant, such that the spring constant of the first spring increases with compression of the first spring. In this manner, the spring constant can increase in response to increased load exerted on the suspension system, resulting in higher stiffness of the suspension system at higher loads. Thus, for example, when the downforce system is activated and / or the downforce is increased, compression of the first spring may increase resulting in increased stiffness of the suspension system.

[0078] The first spring may comprise a first section and a second section arranged in series, the first section comprising a plurality of disc springs arranged in series, and the second section comprising a plurality of disc springs arranged in parallel. Such an arrangement of disc springs may provide the effect of a progressive spring constant that increases with compression of the spring. In particular, the first section may have a relatively low spring constant, whereas the second section may have a relatively high spring constant. Thus, as the suspension system is progressively loaded, the lower spring constant first section is preferentially compressed until its travel range is exhausted, following which the higher spring constant section is compressed.

[0079] The suspension system may further comprise a second spring arranged in parallel with the actuator. The second spring may be arranged to continuously contribute to the reaction force of the suspension system. Thus, when the actuator is in the engaged state, both the first and second springs may contribute in parallel to the reaction force. When the actuator is in the disengaged state, only the second spring may contribute to the reaction force.

[0080] Where the actuator comprises a linear actuator in series with the first spring, the second spring may be arranged in parallel with the linear actuator.

[0081] The second spring may be coupled between the first linkage and the second linkage of the suspension system.

[0082] The second spring may comprise any suitable type of spring, such as a coil spring, a disc spring, a pneumatic spring, and a hydraulic spring. In some cases, the second spring may comprise a damper, or a damper spring.

[0083] The actuator may comprise a fluid-based (or fluid-filled) actuator. A fluid-based actuator may facilitate continuous and accurate adjustment of the suspension system, thereby enabling accurate control of the ride height. Moreover, a fluid-based actuator may facilitate application of a force, e.g. to compress the first spring and / or push the first and second linkages apart. Herein, a fluid-based actuator may refer to an actuator where one or more fluids (e.g. liquid or gas) are used to operate the actuator. Examples of a fluid-based actuator include a hydraulic actuator and a pneumatic actuator. A fluid-based actuator may comprise a fluid chamber (cylinder) in which a piston is located, such that a fluid can be introduced into the chamber to generate a pressure differential across the piston and cause the piston to move. Any suitable type of fluid- based actuator may be used.

[0084] Advantageously, the fluid-based actuator may act as a spring, such that the fluid-based actuator may contribute to the reaction force (and stiffness) of the suspension system. Thus, the fluid-based actuator may also be referred to as a fluid-based spring, e.g. a hydraulic spring or a pneumatic spring. A pressure in the fluid chamber may be adjustable to adjust a spring constant of the fluid-based actuator. Thus, where a fluid-based actuator is used, the first spring discussed above may be dispensed of, as the fluidbased actuator may fulfil the function of both actuator and spring, thus simplifying construction of the system.

[0085] The ride height control system may further comprise an accumulator in fluid communication with a fluid chamber in the fluid-based actuator. Such an arrangement may facilitate accurate control of the fluidbased actuator, whilst enabling the fluid-filled actuator to effectively act as a spring in the suspension system. A fluid pressure in the accumulator can be controlled (adjusted) to control a spring constant of the fluid-based actuator. Advantageously, the accumulator may be mounted separately from the actuator, which may facilitate integration into the vehicle as well as improve ease of access. The sensor may be configured to detect an operating parameter of the active downforce system. In this manner, control of the actuator in the suspension system can be performed as a function of the operating parameter of the active downforce system. Various operating parameters of the active downforce system may be used to provide an indication of the load exerted on the suspension system by the downforce system. As such, any suitable operating parameter of the active downforce system may be detected, with the sensor being adapted accordingly. In some cases, multiple operating parameters of the active downforce system may be monitored, e.g. using multiple respective sensors. The multiple operating parameters can then be used by the controller to estimate the load exerted on the suspension system, and to control operation of the actuator.

[0086] For example, the operating parameter of the active downforce system may comprise an operating parameter of an airflow generator of the active downforce system. Typically, the downforce generated by the active downforce system is directly related to operation of the airflow generator, such that detecting an operating parameter of the airflow generator can provide a reliable indication of the resulting load exerted on the suspension system. For instance, the operating parameter of the airflow generator may comprise a fan speed and / or a fan torque (e.g. where the airflow generator comprises a fan). The sensor may then comprise a fan speed sensor, and / or a torque sensor. Additionally or alternatively, the operating parameter of the airflow generator may comprise an airflow speed and / or an airflow rate of an airflow generated by the airflow generator. The sensor may then comprise a suitable airflow sensor. Where the active downforce system comprises a blown diffusion system, the sensor may be configured to detect (measure) a flow speed and / or rate of an exhaust gas blown into the diffuser.

[0087] As another example, the operating parameter of the active downforce system may comprise an air pressure in a region under the vehicle acted on by the active downforce system. In particular, the airflow generator may be configured to generate a pressure differential between a region under the vehicle and a surrounding atmosphere. In line with the above discussion, this may be achieved by evacuating air from the region under the vehicle and / or accelerating an airflow on the underside of the vehicle. The downforce generated is related (e.g. proportional) to the pressure differential, such that the pressure in the region under the vehicle can provide a reliable indication of the generated downforce and resulting load on the suspension system. The sensor may therefore comprise a pressure sensor arranged to detect pressure in the region under the vehicle. In some cases, an ambient pressure sensor may further be used to detect the pressure in the surrounding atmosphere, to allow determination of the pressure differential. Otherwise, a predetermined atmospheric pressure may be used to determine the pressure differential.

[0088] The suspension system may comprise a front suspension system arranged to connect the sprung mass of the vehicle to front wheels of the vehicle, and a rear suspension system arranged to connect the sprung mass to rear wheels of the vehicle; and the may actuator comprise a first actuator in the front suspension system operable to adjust a ride height of a front of the vehicle, and a second actuator in the rear suspension system operable to adjust a ride height of a rear of the vehicle. Thus, ride height may be controlled for both the front and rear of the vehicle. Each of the front suspension system and the rear suspension system may have any of the features described above in relation to the suspension system of the first aspect. For each example, each of the front suspension system may have one or more of a respective first spring, second spring, first linkage, and second linkage as described above.

[0089] A same controller may be used for controlling both the first actuator and the second actuator. Alternatively, separate controllers may be provided for the front and rear suspension systems.

[0090] Where a same controller (or control system) is used for the front and rear suspension systems, the controller may be configured to independently operate the first actuator and the second actuator. In this manner, the ride height (and / or stiffness) of the front and rear of the vehicle can be adjusted independently, to provide desired vehicle handling characteristics. For example, this enables a pitch of the vehicle to be adjusted and controlled as a function of the generated downforce. Alternatively, the controller may be configured to operate the first actuator and the second actuator together, e.g. in a uniform manner.

[0091] The controller may comprise (e.g. the controller may be connected to) a user interface for receiving a user input, wherein the controller is further configured to operate the actuator as a function of the user input. In this manner, the user can set (select) one or more parameters of the ride height control system.

[0092] The user interface may be configured to receive a selection of a ride height from the user, and to set the predetermined ride height based on the received selection. In some cases, the user interface may be configured to receive a selection of a ride height profile, with the controller being configured to control the actuator based on the selected ride height profile. The ride height profile may, for example, indicate a target ride height of the vehicle as a function output signal from the sensor, or as a function of an operating parameter of the active downforce system.

[0093] The controller may include one or more selectable use profiles (or modes), which may be selectable via the user interface. Each use profile may comprise an indication of a target ride height and / or a target stiffness of the suspension system. When a use profile is selected, the controller is configured to operate the actuator to maintain the corresponding target ride height and / or target stiffness. Different use profiles may be tailored to different driving conditions. By way of example, a first use profile may be provided for road and / or urban driving. The first use profile may, for instance have a higher ride height (e.g. to facilitate clearing obstacles and speed bumps) and / or a lower target stiffness (e.g. for improved passenger comfort). A second use profile may be provided for competitive driving (racing). The second use profile may thus have a lower ride height, and / or a higher target stiffness.

[0094] As another example, the user interface may be configured to receive a selection of suspension system stiffness from the user, and to control the actuator to maintain the selected stiffness. In some cases, the user interface may be configured to receive a selection of a stiffness profile, with the controller being configured to control the actuator based on the selected stiffness profile. The stiffness may, for example, indicate a stiffness of the suspension system as a function output signal from the sensor, or as a function of an operating parameter of the active downforce system.

[0095] More generally, the user interface may allow a user to manually select a target ride height, stiffness of the suspension system, and / or a level of the downforce generated by the downforce system. Thus, in some cases, the controller may be configured to control the actuator and / or the active downforce system based on a user input received via the user interface. In this manner, the user interface may be used to control one or both the downforce system and the suspension system. Control of both the active downforce system and the suspension system via a same user interface may simplify user control of the two systems.

[0096] Accordingly, the controller may include one or more selectable use profiles (or modes), where each use profile is associated with one or more predetermined operating parameters for the downforce system, and one or more predetermined settings for the suspension system. In response to selection of a use profile via the user interface, the controller may be configured to control the downforce system based on the one or more predetermined operating parameters, and to control the actuator based on the one or more predetermined settings. In this manner, the downforce system and the suspension system may be controlled substantially simultaneously in response to the user’s selection of a user profile. This may ensure that the suspension system is suitably controlled to compensate for any change in downforce. For example, this may enable a user to select different use profiles corresponding to different levels of generated downforce, without having to separately adjust the suspension system to compensate for the different levels of downforce.

[0097] The one or more predetermined operating parameters of the downforce system may, for example, comprise a fan speed, fan torque, airflow speed, and / or airflow rate of the downforce system. Where the downforce system comprises a barrier (or skirt) extending downwards from an underside of the vehicle, the operating parameter may comprise a height of the barrier above the ground surface. The one or more predetermined operating parameters may also comprise a target downforce. Accordingly, when a use profile is selected, the controller may set operating parameters of the downforce system to the corresponding predetermined operating parameters. Where the predetermined operating parameters comprise a target downforce, the controller may control the downforce system to achieve the target downforce, e.g. based on a known relationship between the operating parameters and generated downforce and / or using the sensor output as feedback.

[0098] The one or more predetermined settings for the suspension system may, for example, comprise a position of the actuator, a stiffness of the suspension system, and / or a target ride height. Accordingly, when a use profile is selected, the controller may control the actuator to achieve the predetermined settings.

[0099] As an example, the one or more selectable use profiles may correspond to different levels of downforce. In line with the above, the use profiles may be tailored to different driving scenarios (e.g. urban, track, speed bumps, etc.). There may be a first use profile corresponding to a first, higher level of downforce, and a second use profile corresponding to a second, lower level of downforce. The predetermined setting for the suspension system may comprise a first, higher stiffness for the first use profile, and a second lower stiffness for the second use profile. Thus, when the first use profile is selected, the stiffness of the suspension system may automatically be increased, whilst when the second use profile is selected, the stiffness of the suspension system may automatically be decreased.

[0100] The one or more selectable use profiles may be stored in a memory of the controller. Here, control of the active downforce system by the controller may refer to setting (or adjusting) an operating parameter of the active downforce system by the controller.

[0101] The user interface may comprise any suitable interface for receiving a user selection, such as a touchscreen, keyboard, selection wheel, and / or one or more buttons. For instance, the user interface may comprise one or more physical input devices such as buttons, switches, knobs, dials, and / or rotary selectors. Additionally or alternatively, the user interface may comprise a screen (e.g. touchscreen) configured to display a graphical user interface. In some cases, the user interface may be provided on a remote device which is communicatively coupled to the controller via a wired or wireless connection. For example, the user interface may be provided by an application executed on a smartphone (or other computing device) that is connected to the controller. Further, in some cases the user interface may comprise voice-activated controls.

[0102] The ride height control system may be operatively integrated with other vehicle systems. In particular, the controller may be configured to control one or more vehicle systems in addition to the ride height control system. This may allow improved performance and adaptability of the vehicle to different driving conditions. For example, the controller may additionally be configured to perform one or more of traction control, electronic stability control (ESC), torque vectoring control, and / or control of a regenerative braking system. Combined control of the ride height system (and optionally the downforce system) with one or more other vehicle systems may enable aspects such as chassis pitch and load transfer to be optimised for different driving conditions.

[0103] The controller may further be configured to operate the actuator based on a location (geographic location) of the vehicle. In this manner, the ride height may automatically be controlled based on the location of the vehicle, e.g. to suit driving conditions at a current location. For example, the controller may comprise a memory in which different locations are associated with different respective ride heights. Additionally or alternatively, the controller may be configured to receive data indicative of a target ride height corresponding to a current location of the vehicle, and to control the actuator based on the received target ride height. For instance, the controller may be in communication with a remote server (e.g. via a wireless network) to receive the data indicative of a target ride height for the current vehicle location. In some cases, the ride height control system may comprise a GPS module for determining a location of the vehicle.

[0104] The controller may be configured for wireless communication with a remote (e.g. cloud) server and / or other wireless communication devices. Wireless, or over-the-air, communications may thus be used, for example, to conduct system updates and diagnostics, and store new use profiles in the controller.

[0105] The ride height control system may further comprise an environmental sensor, the controller being further configured to use an output from the environmental sensor as an input when operating the actuator. In this manner, control of the suspension system may be adapted to current environmental conditions. For example, the environmental sensor may comprise a temperature sensor and / or a pressure sensor. This enables the controller to compensate for factors such as temperature-dependent changes in fluid viscosity, air spring pressure, and / or component performance, to provide more accurate control of the ride height.

[0106] According to a second aspect of the invention, there is provided a vehicle comprising: an active downforce system comprising an airflow generator configured to produce an airflow for generating a downforce acting on the vehicle; and a ride height control system according to the first aspect of the invention. Any of the features described above in relation to the first aspect of the invention may be shared with the second aspect of the invention, and vice versa.

[0107] The airflow generator may be configured to generate the downforce by generating a pressure differential between a region under the vehicle and a surrounding atmosphere. For example, the airflow generator may comprise a suitable airflow source such as a fan, turbine, vacuum generator, or the like. The airflow source may be arranged to evacuate air from the region under the vehicle, to create a low-pressure region under the vehicle, thereby resulting in a downforce acting on the vehicle.

[0108] The airflow generator may be powered by a power source in the vehicle. For example, the airflow generator may be powered by a battery, fuel-cell, or other suitable power source in the vehicle. In some cases, the power source may be shared between the airflow generator and a traction system (e.g. main engine) of the vehicle).

[0109] The airflow generator may be a dedicated airflow generator (or pressure source). In other words, the airflow generator may be configured to be driven (or controlled) independently from a main engine of the vehicle. For example, the airflow generator may be driven by a motor that is independent from a motor of a traction system of the vehicle. In this manner, performance of the airflow generator may be independent from a speed at which the vehicle is driving. Providing a dedicated airflow generator for the downforce system may enable the airflow generator to be controlled independently from other vehicle systems. This may facilitate control of the pressure differential generated by the pressure source, and hence the downforce generated by the downforce system.

[0110] In some cases, the active downforce system may comprise at least two airflow generators, each airflow generator being configured to produce an airflow for generating a downforce acting on the vehicle. Using at least two airflow generators may provide redundancy, which may improve safety of the downforce system. For example, in the case of a failure of one of the airflow generators, the other airflow generators) may continue to operate normally. This may avoid a sudden loss of the downforce generated by the downforce system. The at least two airflow generators may be connected in parallel with one another, e.g. they may be connected in parallel to an airflow path in the active downforce system, such that each of the at least two airflow generators can act in parallel on the airflow path. Thus, the at least two airflow generators can individually and collectively contribute to an airflow along the airflow path for generating the downforce.

[0111] The vehicle may comprise a primary energy store (e.g. battery) for powering the active downforce system, e.g. for powering the airflow generator. The primary energy store may also be arranged to power the ride height control system. The vehicle may further comprise an auxiliary energy store which is configured to supply power to the active downforce system, and optionally the ride height control system, in the event of a failure of the downforce system and / or the vehicle. The auxiliary energy store may comprise a battery. In one example, the auxiliary energy store may comprise a flywheel which is configured to be connected to the downforce system by a linkage system in the event of a failure of the downforce system and / or the vehicle.

[0112] The active downforce system may further comprise a barrier arranged to extend downwards from an underside of the vehicle to restrict airflow into a region under the vehicle, wherein the airflow generator is configured to remove air from the region under the vehicle to generate a pressure differential across the barrier. Providing the barrier around the region may facilitate maintaining the pressure differential between the region under the vehicle and the surrounding atmosphere using the airflow generator. This may enable larger magnitude downforces to be achieved. The barrier may, for example, be in the form of a skirt extending downwards from the underside of the vehicle. The barrier may at least partially surround the region under the vehicle.

[0113] The active downforce system may comprise a diffuser on an underside of the vehicle, and the airflow generator may be arranged to cause an airflow in the diffuser. In other words, the active downforce system may comprise an active diffusion system. The airflow in the diffuser may cause a reduction in pressure in a region under the vehicle, resulting in an increase in downforce on the vehicle. The airflow generator may be arranged to generate an airflow which contributes to and / or accelerates airflow in the diffuser.

[0114] Various types of active diffusion system may be used. For instance, in some cases, the airflow generator may be arranged to suck (aspirate) air from under the vehicle via the diffuser. Thus, the airflow generator may serve to accelerate the airflow in the diffuser. Such an arrangement may be referred to as a sucked (or aspirated) diffuser or diffusion system. With a sucked diffusion system, the generated downforce can be controlled (e.g. adjusted), for example, by controlling the airflow generator (e.g. by controlling a speed and / or flow rate of the airflow generator).

[0115] In some cases, the airflow generator may be arranged to blow air or gas into the diffuser, to accelerate the airflow in the diffuser. For example, the vehicle may be configured to blow exhaust gas from an engine of the vehicle into the diffuser. In such a case, an exhaust of the vehicle engine may act as the airflow generator. Such an arrangement may be referred to as a blown diffuser or diffusion system. With a blown diffusion system, the generated downforce can be controlled, for example, by controlling a speed and / or flow rate of the exhaust gas blown into the diffuser. For instance, a valve and / or throttle may be connected between the engine exhaust and the diffuser, to control a speed and / or flow rate of the exhaust gas blown into the diffuser.

[0116] Additionally or alternatively, a blown diffusion system may be arranged to blow exhaust gas over (i.e. above) the diffuser, e.g. so that the exhaust gas flows over (along) an upper surface of the diffuser. This may act to entrain an airflow in (through) the diffuser, further contributing to acceleration of the airflow under the vehicle. More generally, the blown diffusion system may blow exhaust gas below and / or above the diffuser. The blown diffusion system may comprise a flow control unit for controlling the flow of gas blown into and / or over the diffuser, e.g. for controlling the flow speed and / or flow rate. Such a flow control unit may, for instance, comprise a flow generator or impeller (e.g. a fan or a turbo) for accelerating the flow of gas. The flow control unit may additionally or alternatively comprise a valve and / or a throttle for controlling the flow of gas. The flow control unit may be controllable to control the flow of gas blown into and / or over the diffuser, and hence the generated downforce.

[0117] The diffuser may be arranged (e.g. shaped) to accelerate an airflow under the vehicle, e.g. in order to enhance a ground effect of the vehicle and increase the generated downforce. The diffuser may located on the underside of the vehicle at the rear of the vehicle. The diffuser is arranged to provide a transition between the low-pressure region under the vehicle and the higher atmospheric pressure at the rear of the vehicle. In particular, the diffuser may be arranged to decelerate the air flow exiting the rear of the vehicle, an effect of this being to accelerate an upstream airflow under the vehicle which contributes to increasing the downforce.

[0118] The diffuser may define one or more channels on the underside of the vehicle (e.g. on a rear portion of the underside of the vehicle), which extend in a longitudinal direction of the vehicle and have an increasing cross-sectional size towards the rear of the vehicle. In this manner, the increasing cross- sectional size decelerates the airflow towards the rear of the vehicle, which may provide a smoother transition between the low-pressure region under the vehicle and the surrounding atmosphere, which contributes to maintaining the low pressure under the vehicle and sustaining the downforce.

[0119] The underside of the vehicle may be shaped to accelerate an airflow under the vehicle, to contribute to the vehicle’s ground effect. For example, the underside of the vehicle may be shaped to define a constriction for the airflow under the vehicle, to accelerate the airflow. The constriction may be located upstream (i.e. in front) of the diffuser. For instance, the underside of the vehicle may be shaped such that an airflow channel defined between the underside of the vehicle and the ground surface decreases in size (e.g. height and / or width) from a maximum at a front of the vehicle to a minimum part way along a length of the vehicle. Then channel may then increase in size from the minimum towards the diffuser.

[0120] The vehicle of the invention may combine one or more of the types of downforce systems and diffusions systems described herein.

[0121] The controller may further be configured to control operation of the active downforce system. Thus, the controller (or control system, more generally) may control operation of both the ride height control system and the active downforce system. In this manner, both ride height and downforce can be controlled together, so as to optimise performance of the vehicle for different driving conditions. For instance the downforce system can be controlled to achieve a desired downforce, whilst controlling the ride height to provide a desired aerodynamic performance of the vehicle. Stiffness of the suspension system can also be adjusted in tandem with the active downforce system.

[0122] The controller may be configured to control one or more operating parameters of the active downforce system. For example, the controller may be configured to control an operating parameter of the airflow generator (e.g. any of the operating parameters mentioned above such as fan speed, fan torque, airflow speed, airflow rate). Where the downforce system comprises a barrier (or skirt) extending downwards from an underside of the vehicle, the controller may be configured to control a height of the barrier above the ground surface. This may serve to control an amount of airflow between the surrounding atmosphere and the region under the vehicle, to control the pressure differential and hence the downforce.

[0123] The controller may be configured to operate the actuator and / or to control an operating parameter of the active downforce system to maintain (or achieve) a predetermined ride height, or to adjust the ride height.

[0124] The controller may be configured to operate the actuator and / or to control an operating parameter of the active downforce system to maintain (or achieve) a predetermined downforce.

[0125] The controller may be configured to operate the actuator and / or to control an operating parameter of the active downforce system based on one or more predetermined profiles. The predetermined profiles may be automatically selected by the vehicle (e.g. based on a current driving condition), and / selectable by a user (e.g. via a user interface as discussed above). Each predetermined profile may comprise an indication of a target ride height and / or stiffness of the suspension system, and an indication of a target downforce. The controller can then control the actuator and one or more operating parameters of the downforce system accordingly, taking the output from the sensor(s) as an input for the control.

[0126] By way of example, with a first predetermined profile (e.g. in a first mode of operation), the controller may be configured to increase the downforce generated by the active downforce system, and to maintain or adjust (e.g. reduce) a target ride height of the vehicle. For example, the controller may be configured to activate the downforce system, or increase the downforce compared to a second predetermined profile (described below). In some cases, the controller may be configured to increase the stiffness of the suspension system in response to the increased downforce. The first predetermined profile may be used, for example, during cornering with the vehicle, to increase a grip of the vehicle when going around a bend.

[0127] As another example, with a second predetermined profile (e.g. in a second mode of operation), the controller may be configured to decrease the downforce generated by the active downforce system, and to maintain or adjust (e.g. increase) a target ride height of the vehicle. For example, the controller may be configured to deactivate the downforce system, or reduce the downforce compared to the first predetermined profile. The ride height of the vehicle in the second predetermined profile may be greater than in the first predetermined profile. In some cases, the controller may be configured to reduce the stiffness of the suspension system in response to the reduced downforce. The second predetermined profile may be used on straights, for example, to increase reduce drag and improve fuel efficiency.

[0128] The vehicle may comprise a safety system configured to: detect a safety risk associated with operation of the active downforce system and / or the ride height control system; and in response to detection of a safety risk, generate an alert and / or cause the vehicle to be operated in a safety mode. In this manner, safety of the vehicle may be improved, by automatically alerting the driver and / or activating a safety mode in case a safety risk associated with the downforce system is detected. This may reduce a risk of sudden loss of the downforce generated by the downforce system, which could be highly dangerous for the vehicle and its occupants. The safety system may be implemented with the controller described above. A safety risk associated with operation of the active downforce system and / or ride height control system may be indicative of a fault with the vehicle, active downforce system, and / or ride height control system affecting safe operation of the vehicle. A safety risk may be detected, for example, in response to detection of one or more of the following conditions: damage to a component of the downforce system, the ride height control system, or the vehicle, a fault in the airflow generator or other part of the downforce system, a fault (or damage to) an energy store of the vehicle used power the downforce system, a low remaining energy level of the energy store, overheating of a component, a generated downforce outside of a target range, a ride height outside of a target range. The safety system may thus comprise one or more sensors configured to detect any of the conditions mentioned above. The safety system (e.g. the controller) may receive output signals from the one or more sensors, and detect a safety risk based on the one or more output signals.

[0129] Where an alert is generated, this may serve to notify the driver of the safety risk, so that they can take appropriate action to avoid danger. The alert may take any suitable form, such as an audible alert (e.g. via a speaker of the vehicle) and / or a visible alert (e.g. via a display unit in the vehicle).

[0130] Where the vehicle is operated in the safety mode, this may serve reduce a risk of accident in case of failure of the downforce system. In particular, one or more operating parameters of the vehicle and / or downforce system may be automatically controlled in the safety mode, to reduce the risk of accident.

[0131] The safety system may be configured to detect a safety risk if a remaining energy level in an energy store of the vehicle is below a predetermined level. In this manner, if the energy level falls below the predetermined level, the safety system may automatically generate an alert and / or operate the vehicle in the safety mode. When the energy store falls below the predetermined level, this may indicate that the downforce system may not be able to be powered for much longer. Accordingly, by generating an alert and / or operating the vehicle in the safety mode, operation of the vehicle can be adapted so as to avoid dangerous driving conditions in case of loss of downforce when the energy store is depleted.

[0132] The safety system may be configured to provide (output) a report indicative of the detected safety risk. This may facilitate diagnosis and repair of the vehicle. The report may include an indication of which system(s) and / or which component(s) gave rise to the detected safety risk.

[0133] The energy store may be configured to power the active downforce system, e.g. to power the airflow generator, and / or the ride height control system. For example, the energy store may comprise a battery. Thus, when a charge level of the battery is below the predetermined level, an alert may be generated and / or the vehicle may be operated in the safety mode.

[0134] Operating the vehicle in the safety mode may comprise reducing an upper limit associated with an operating parameter of the vehicle. In this manner the operating parameter of the vehicle may be automatically reduced in response to detection of a safety risk. Here, operating parameters of the vehicle include operating parameters of the downforce system. By way of example, the upper limit associated with an operating parameter of the vehicle may comprise one or more of: a maximum speed of the vehicle, a maximum power output of the vehicle engine, a maximum downforce generated by the downforce system, a maximum associated with the airflow generator (e.g. fan speed, fan torque, airflow speed, airflow rate). Thus, for example, in response to detecting a safety risk, the safety system may automatically reduce the maximum speed of the vehicle and / or the maximum downforce generated by the downforce system. This may reduce a risk of a dangerous driving situation arising. The upper limit associated with the operating parameter may act as a threshold, such that the operating parameter cannot be set above the upper limit when in the safety mode.

[0135] Operating the vehicle in the safety mode may comprise progressively decreasing (e.g. ramping down) the upper limit associated with the operating parameter of the vehicle. The speed with which the upper limit is decreased may depend on a severity of the detected risk. Ramping down the upper limit may avoid a sudden change in vehicle performance.

[0136] The vehicle may be any type of vehicle such as a road car or race car. The vehicle may be an electric vehicle, a hybrid vehicle, a vehicle with an internal combustion engine, a fuel-cell-powered vehicle, or any other type of powered vehicle.

[0137] According to a third aspect of the invention, there is provided a method of controlling a ride height of a vehicle, the vehicle comprising an active downforce system configured to generate a downforce acting on the vehicle, the method comprising: detecting, with a sensor, a parameter indicative of a downforce generated by the active downforce system, wherein the suspension system is arranged to support a sprung mass of the vehicle; controlling, as a function of an output signal from the sensor, operation of an actuator of the suspension system, wherein the actuator is operable to adjust a ride height of the vehicle.

[0138] The method of the third aspect of the invention may be implemented using the ride height control of the first aspect and / or the vehicle of the second aspect. Accordingly, any features disclosed above in relation to preceding aspects of the invention can be shared with the third aspect of the invention, and vice versa.

[0139] The method of the third aspect of the invention may be performed by the controller of the ride height control system. Thus, the method may be a computer-implemented method.

[0140] The step of detecting with the sensor may comprise receiving the output signal from the sensor.

[0141] The step of controlling operation of the actuator may comprise generating a control signal for controlling operation of the actuator.

[0142] Any of the operations performed by the controller in the first and second aspects of the invention can be applied as steps of the method of the third aspect of the invention.

[0143] The method may further comprise controlling the actuator to maintain a predetermined ride height of the vehicle.

[0144] The method may comprise controlling the actuator to adjust the downforce generated by the active downforce system.

[0145] The method may comprise receiving, via a user interface, a user selection of a ride height, and controlling the actuator to maintain the selected ride height. Where the actuator is operable to adjust a stiffness of the suspension system, the method may comprise controlling operation of the actuator to adjust a stiffness of the suspension system as a function of the output signal from the sensor.

[0146] The method may comprise receiving via a user interface, a user selection of a stiffness of the suspension system, and controlling the actuator to maintain the selected stiffness.

[0147] The method may comprise detecting a safety risk associated with operation of the active downforce system; and in response to detection of a safety risk, generating an alert and / or cause the vehicle to be operated in a safety mode.

[0148] In a fourth aspect of the invention, there is provided a vehicle comprising: an active downforce system comprising an airflow generator configured to produce an airflow for generating a downforce acting on the vehicle; and a safety system configured to: detect a safety risk associated with operation of the active downforce system; and in response to detection of a safety risk, generate an alert and / or cause the vehicle to be operated in a safety mode.

[0149] Any of the features described in relation to preceding aspects of the invention may be applied to the vehicle of the fourth aspect of the invention. In particular, the active downforce may include features described in relation to the active downforce system in the first and second aspects of the invention. Moreover, the safety system may be as described in relation to the safety system in the vehicle of the second aspect of the invention.

[0150] In a fifth aspect of the invention, there is provided a vehicle comprising: an active downforce system comprising an airflow generator configured to produce an airflow for generating a downforce acting on the vehicle; and a suspension system for supporting a sprung mass of the vehicle, wherein the suspension system comprises an actuator operable to control a ride height of the vehicle; a controller configured to operate the active downforce system and the actuator.

[0151] The controller may comprise (e.g. store) one or more selectable use profiles (or modes), where each use profile is associated with one or more predetermined operating parameters for the downforce system, and one or more predetermined settings for the suspension system. In response to selection of a use profile via a user interface, the controller may be configured to control the downforce system based on the one or more predetermined operating parameters, and to control the actuator based on the one or more predetermined settings. As an example, each use profile may be associated with a respective target downforce and a respective target ride height.

[0152] Any of the features described in relation to preceding aspects of the invention may be applied to the vehicle of the fourth aspect of the invention. In particular, the active downforce system, the suspension system, and controller may include any of the features described in preceding aspects of the invention. Likewise, features relating to the use profiles described above are applicable to the fifth aspect of the invention. The suspension system may form part of a ride height control system as described in relation to the first aspect of the invention.

[0153] The vehicle may further comprise one or more sensors for detect a parameter indicative of a downforce generated by the active downforce system, e.g. as described in relation to the first aspect of the invention.

[0154] In a sixth aspect of the invention, there is provided a method of controlling a vehicle comprising an active downforce system and a suspension system, the method comprising: receiving (e.g. via a user interface) a selection of a use profile from a plurality of selectable use profiles, wherein each use profile is associated with one or more predetermined operating parameters for the active downforce system and one or more predetermined settings for the suspension system; operating (e.g. by a controller) the active downforce system based on the one or more predetermined operating parameters associated with the selected use profile; and operating (e.g. by the controller) an actuator of the suspension system based on the one or more predetermined settings associated with the selected use profile, wherein the actuator is operable to control a ride height of the vehicle.

[0155] The method of the sixth aspect of the invention may be applied with the vehicle of the fifth aspect of the invention. Accordingly, any features described in relation to preceding embodiments are applicable to the method of the sixth aspect (and vice versa).

[0156] The method of the sixth aspect may be combined with one or more steps from the method of the third aspect. Thus, the actuator of the suspension system may be controlled based on the predetermined setting(s) associated with the selected use profile, and using the output signal from the sensor as an input. For example, the predetermined setting may comprise a target ride height, and the output signal from the sensor may be indicative of a ride height of the vehicle. The actuator can then be controlled to achieve the target ride height, using the output signal from the sensor as feedback.

[0157] The invention includes the combination of the aspects and preferred features described except where such a combination is clearly impermissible or expressly avoided.

[0158] Summary of the Figures

[0159] Embodiments and experiments illustrating the principles of the invention will now be discussed with reference to the accompanying figures in which:

[0160] Fig. 1 a is a schematic side view of a vehicle according to an embodiment of the invention;

[0161] Fig. 1 b is a schematic side view of a vehicle according to an embodiment of the invention;

[0162] Fig. 1c is a schematic side view of a vehicle according to an embodiment of the invention;

[0163] Fig. 2 is a perspective view of a suspension system in a ride height control system according to an embodiment of the invention;

[0164] Fig. 3 is a schematic front view of the suspension system of Fig. 2; Fig. 4 is a schematic top view of the suspension system of Fig. 2;

[0165] Figs. 5a and 5b show schematic top and side views of part of the suspension system of Fig. 2, where an actuator of the suspension system is in a disengaged state;

[0166] Figs. 6a and 6b show schematic top and side views of part of the suspension system of Fig. 2, where an actuator of the suspension system is in an engaged state;

[0167] Fig. 7 shows a schematic top view of the actuator of the suspension system of Fig. 2;

[0168] Fig. 8 shows a schematic cross-sectional view of a spring that can be used in a ride height control system according to an embodiment of the invention;

[0169] Fig. 9 shows a perspective view of the suspension system of Fig. 2, depicting further components of the system; and

[0170] Fig. 10 shows a flow diagram of a method according to an embodiment of the invention.

[0171] Detailed Description of the Invention

[0172] Aspects and embodiments of the present invention will now be discussed with reference to the accompanying figures. Further aspects and embodiments will be apparent to those skilled in the art. All documents mentioned in this text are incorporated herein by reference.

[0173] Fig. 1 a shows a schematic side view of a vehicle 100 according to an embodiment of the invention. In the example shown, the vehicle 100 is a car, however other types of vehicle may also be used. The vehicle 100 comprises an active downforce system, which includes a barrier (or skirt) 102 mounted on an underside 106 of the vehicle 100. An upper surface 110 of the barrier 102 is connected to the underside 106 of the vehicle 100, with the barrier extending downwards towards a ground surface (e.g. a road) 114 on which the vehicle 100 is disposed. The barrier 102 is arranged to at least partially define a region under the vehicle. For example, the barrier 102 may form a closed shape, such that it extends around a perimeter of a region over the ground surface 114 under the vehicle 100. Alternatively, the barrier 102 may be arranged so that it only extends around a portion of the region under the vehicle 100. acts to restrict airflow into a region under the vehicle 100. The barrier 102 acts to restrict airflow into the region under the vehicle 100.

[0174] The active downforce system of the vehicle 100 further includes an airflow generator (or pressure source) 126 which is configured to generate a pressure differential across the barrier 102. The airflow generator 126 is disposed on an airflow path 128 between an outlet 130 of the barrier 102 and an outlet 132 of the downforce system. The outlet 130 of the barrier 102 is formed as an aperture in the upper surface 110 of the barrier 102, whilst the outlet 132 of the downforce system is formed as an aperture in a body of the vehicle 100 located towards the rear end of the vehicle 100. The airflow generator 126 is configured to cause air to flow out of the region under the vehicle defined by the barrier 102, and along the airflow path 128, as illustrated by arrows 134 in Fig. 1 . As an example, the airflow generator 126 may comprise a fan which is arranged to generate an airflow along the airflow path 128. When the airflow generator 126 is activated, air may flow out of the region under the vehicle defined by the barrier via the outlet 130, along the airflow path 128, and out of the outlet 132 of the downforce system. Therefore, when the airflow generator 126 is activated, air may be evacuated from the region under the vehicle 100, which results in a drop in pressure in the region compared to atmospheric pressure. Due to the drop in pressure in region under the vehicle, a pressure differential is generated across the barrier 102, due to a difference between the atmospheric pressure surrounding the barrier 102 and the lower pressure in the region inside the barrier 102. Such a pressure differential results in a downforce acting on the vehicle 100, which may provide an improved grip of the vehicle 100 on the ground surface 114.

[0175] A rim 118 may be disposed at a lower end of the barrier 112, i.e. at an end of the barrier 102 closest to the ground surface 114. The rim 118 can extend along the lower end of the barrier 102, e.g. to extend along the perimeter of the region defined by the barrier 102. The rim 118 may include a sealing element in the form of a sealing strip 120, which is provided on a ground facing-surface of the rim 118 such that the sealing strip 120 is arranged to contact the ground surface 114 and slide along the ground surface 114 when the vehicle 100 moves over the ground surface 114. In this manner, the sealing strip 120 may be brought into contact with the ground surface 114 to form an at least partial seal with the ground surface 114, in order to restrict airflow between the rim 118 and the ground surface 114. Contact of the sealing strip 120 with the ground surface 114 may serve to significantly restrict air leakage into the region defined by the barrier 102, which may facilitate maintaining a low pressure inside the barrier 102, and thus increasing a downforce that can be achieved with the downforce system. The downforce system may further include one or more filters that are arranged along the airflow path 128, in order to capture any dust or debris travelling along the airflow path 128. This may avoid dust or debris from being ejected from the downforce system via the outlet 132.

[0176] The downwardly-extending portion of the barrier 102 may be formed of a flexible piece of material, such as a textile material or similar. Examples of suitable materials include Nylon, rubber, or thin composite materials. Using a flexible material enables the rim 118 to move relative to the upper surface 110 (and therefore relative to the underside 106 of the vehicle 100), e.g. in response to changes in ride height of the vehicle 100.

[0177] The barrier 102 may be retractable, so that it can be stowed when the downforce system is not in use. For example, downforce system may comprise an actuator for controlling a height of the rim 118 above the ground surface 114. The actuator can then be used to raise the rim 118 away from the ground surface 114, when the downforce system is not in use.

[0178] It should be noted that specific details of the downforce system described in reference to Fig. 1a are shown for example only. Other examples of active downforce systems that may be used in the vehicle 100 are disclosed in the applicant’s earlier patent application, published as GB2588394A and which is incorporated herein in its entirety.

[0179] The vehicle 100 further comprises a ride height control system which includes a front suspension system 140 and a rear suspension system 142. The front suspension system 140 is arranged to couple a sprung mass of the vehicle 100 to front wheels 144 of the vehicle 100, and the rear suspension system 142 is arranged to couple the sprung mass to rear wheels 146 of the vehicle 100. The sprung mass of the vehicle 100 may comprise a body, chassis, motor, transmission, and internal components, as well as any passengers and cargo of the vehicle 100. The sprung mass also comprises components of the active downforce system, including the barrier 102, rim 118 and sealing strip 120, as well as the airflow generator 126 and other components forming the airflow path 128. The front suspension system 140 and the rear suspension system 142 may comprise any suitable vehicle suspension system.

[0180] The ride height control system further includes a controller 148 which is configured to control a respective actuator in the front and / or rear suspension systems 140, 142, as described in more detail below. The controller 148 may, for example, be implemented with an onboard computer of the vehicle 100. The ride height system also includes a sensor 150 configured to detect a parameter indicative of a load exerted on the front and / or suspension systems 140, 142 resulting from the active downforce system. The controller 148 is communicatively coupled to the sensor 150 to receive an output signal from the sensor 150. The controller 148 is configured to operate the actuator in the front and / or rear suspension systems 140, 142 as a function of the output signal from the sensor 150.

[0181] The controller 148 may further be configured to control the active downforce system. For example, the controller 148 may be configured to control the airflow generator 126 (e.g. a speed and / or flow rate of the airflow generator 126). The controller 148 may also be configured to control raising and lowering of the rim 118 via a suitable actuator.

[0182] Note that for illustration purposes, in Fig. 1a the pressure source 126, airflow path 128, front and rear suspension systems 140, 142, controller 148, and the sensor 150 are shown with dashed lines to indicate that they are disposed within the vehicle 100, i.e. they would not normally be visible from outside the vehicle 100. It is also to be understood that locations of the components shown are for illustration purposes only, and are not necessarily indicative of actual locations of the components.

[0183] Fig. 1 b shows a schematic side view of a vehicle 170 according to an embodiment of the invention. Where the vehicle 170 has features corresponding to those of the vehicle 100 described above, those are indicated in Fig. 1 b with the same reference numerals as in Fig. 1a, and are not described again.

[0184] The vehicle 170 comprises an active downforce system in the form of a blown diffusion system. The blown diffusion system comprises a diffuser 172 on the underside 106 of the vehicle 170 at a rear of the vehicle 170. The diffuser is shaped to decelerate an airflow 174 (illustrated by the dashed arrows 174) under the vehicle 170 as it exits at the rear of the vehicle. In particular, in an area of the diffuser 172, a gap between the underside 106 of the vehicle 170 and the ground surface 114 increases towards the rear of the vehicle, so as to decelerate the airflow 174 as it passes through the diffuser 172. An effect of the diffuser 172 is to accelerate the airflow 174 in a region under the vehicle upstream of the diffuser 172 (i.e. closer to the front of the vehicle relative to the diffuser 172). Acceleration of the airflow 174 under the vehicle 170 results in a low pressure region under the vehicle 170, causing a downforce to act on the vehicle 170. The blown diffusion system is configured to blow exhaust gas from an engine of the vehicle into the diffuser 172, to accelerate the airflow 174 under the vehicle 170 and increase the generated downforce. As illustrated in Fig. 1 b, an air inlet 176 is located at a front of the vehicle 170 for drawing air into the engine (not shown) of the vehicle 170. Air drawn in via the inlet 176 is mixed with a high-speed flow of hot exhaust gas expelled from the engine. The mixture of air and exhaust gas in conveyed along a duct 178 within the vehicle 170. An outlet 180 of the duct 178 is located at an upstream portion of the diffuser 172, such that the mixture of air and exhaust gas is blown out of the outlet 180 and into the diffuser 172. The gas mixture blown into the diffuser 172 from the outlet 180 adds to the airflow 174 and further serves to accelerate the airflow 174 under the vehicle 170, thus reducing pressure under the vehicle 170 and increasing the generated downforce. Additionally or alternatively, the blown diffusion system may be arranged to blow the gas mixture over (e.g. above) the diffuser 172. The flow of gas above the diffuser 172 may then act to entrain an airflow through the diffuser 172, further contributing to acceleration of the airflow 174 under the vehicle 170. For example, the outlet 180 may be arranged such that the gas mixture exiting the outlet 180 flows over an upper surface of the diffuser 172. In some cases, the outlet 180 may be arrange such that portions of the gas mixture are blown above and below the diffuser 172.

[0185] The duct 178 may be connected to the outlet 180 via a flow control unit 182, for controlling a flow speed and / or flow rate of the gas blown into the diffuser 172. For example, the flow control unit 182 may comprise a valve and / or a throttle, for controlling to flow of gas exiting the outlet 180. The flow control unit 182 may be arranged to accelerate the flow of gas exiting the outlet 180. For example, the flow control unit 182 may comprise a flow generator such as a fan or a turbo, for propelling the gas out of the outlet 180. The flow control unit 182 may be controllable by the controller 148, in order to control the flow of gas out of the outlet 180 and hence the generated downforce.

[0186] The underside 106 of the vehicle 170 may further be shaped to accelerate air flowing under the vehicle 170, e.g. in addition to providing the diffuser 172. In particular, the underside 106 may define a constriction (or Venturi passage) for accelerating air passing under the vehicle 170 as the vehicle 170 drives over the ground surface 114. Fig. 1 b illustrates an example profile of the underside 106 for accelerating the airflow 174. The underside 106 of the vehicle 170 defines a channel with the ground surface 114 for airflow 174 under the vehicle 170. The underside 106 is shaped such that a height of the channel between the underside 106 and the ground surface 114 decreases from a front of the vehicle 170 towards a region part way along the length of the vehicle, where the height of the channel is at a minimum. Thus, the channel has a wide opening at the front of the vehicle, which gradually becomes narrower towards a mid-section of the vehicle. The height of the channel increases again from the region of minimum height towards the diffuser 172. Thus, the region of minimum height of the channel under the vehicle acts as a constriction (e.g. a Venturi passage) which accelerates the airflow 174 under the vehicle, contributing to reducing the pressure under the vehicle and increasing the downforce. In this manner, when the vehicle 170 drives over the ground surface 114, air passing under the vehicle 170 is accelerated due to the shape of the underside 106 and the diffuser 172, with further acceleration of the airflow 174 being provided by the gas mixture blown into the diffuser 172 via the outlet 180. It should be noted that Fig. 1 b depicts the profile of the underside 106, the inlet 176, the duct 178, the outlet 180, and the diffuser 172, for illustration purposes. In practice these features may not be visible from the side of the vehicle 170.

[0187] Fig. 1c shows a schematic side view of a vehicle 190 according to an embodiment of the invention. Where the vehicle 190 has features corresponding to those of the vehicle 100 described above, those are indicated in Fig. 1c with the same reference numerals as in Fig. 1 a, and are not described again.

[0188] The vehicle 190 comprises an active downforce system in the form of a sucked (aspirated) diffusion system. The aspirated diffusion system comprises a diffuser 172 on the underside 106 of the vehicle 170 at a rear of the vehicle 170. The diffuser 172 is arranged as described above in relation to the vehicle 170. Moreover, the underside 106 of the vehicle may be shaped as described above in relation to the vehicle 170 above. The sucked diffusion system comprises an airflow generator 192 which is configured to suck air from under the vehicle 190 in a region of the diffuser 172. In more detail, an air inlet 194 is provided in a portion of the underside 106 of the vehicle 190 forming the diffuser 172, the airflow generator 192 being connected to the air inlet 194 via a duct to aspirate air from the under the vehicle 190 via the air inlet 194. The airflow generator 192 is further connected via a duct to an air outlet 196 of the sucked diffusion system, such that the air sucked from under the vehicle 190 is blown out via the air outlet 196. The airflow generator 192 may, for example, a fan or the like. Sucking air from under the vehicle 190 in the vicinity of the diffuser 172 acts to accelerate the airflow 174 under the vehicle, contributing to reduced pressure under the vehicle 190 and an increased downforce acting on the vehicle 190. The airflow generator 192 may be controlled by the controller 148, to control the downforce generated by the sucked diffusion system.

[0189] It should be noted that Fig. 1c depicts the profile of the underside 106, the inlet 194, air ducts, the outlet 196, the airflow generator 192, and the diffuser 172 for illustration purposes. In practice these features may not be visible from the side of the vehicle 190.

[0190] Figs. 2 to 4 illustrate a suspension system 200 that may form part of a ride height control system according to an embodiment of the invention. For example, the suspension system 200 may be used as the front suspension system 140 and / or the rear suspension system 142 in the any of the vehicles 100, 170, 190. The suspension system 200 is a multi-link pushrod-type suspension system. The suspension system 200 comprises a first linkage in the form of a first rocker (e.g. bell crank) 202 which has a first pivot joint 204 for being pivotably connected to the sprung mass of the vehicle on a first (e.g. left-hand) side of the vehicle. A first pushrod 206 is connected between the first rocker 202 and a first upright assembly 208 of the vehicle. In more detail, a first end of the first pushrod 206 is pivotably connected at one end to the first rocker 202, a pivot axis between the first pushrod 206 and the first rocker 202 being substantially parallel to a pivot axis of the first pivot joint 204. A second end of the first pushrod 206 is pivotably connected to the first upright assembly 208, e.g. via a pivot joint or a ball joint. The first upright assembly 208 is arranged to connect the suspension system 200 to a first (e.g. left) wheel of the vehicle, e.g. the first upright assembly 208 may hold a hub of the first wheel. The suspension system 200 further includes a second linkage in the form of a second rocker (e.g. bell crank) 210 which has a second pivot joint 212 for being pivotably connected to the sprung mass of the vehicle on a second (e.g. right-hand) side of the vehicle. A second pushrod 214 is connected between the second rocker 210 and a second upright assembly 216 of the vehicle. In more detail, a first end of the second pushrod 214 is pivotably connected at one end to the second rocker 210, a pivot axis between the second pushrod 214 and the second rocker 210 being substantially parallel to a pivot axis of the second pivot joint 212. A second end of the second pushrod 214 is pivotably connected to the second upright assembly 216, e.g. via a pivot joint or a ball joint. The second upright assembly 216 is arranged to connect the suspension system 200 to a second (e.g. right) wheel of the vehicle, e.g. the second upright assembly 216 may hold a hub of the second wheel.

[0191] A first assembly comprising the first rocker 202, first pushrod 206 and first upright assembly 208, and a second assembly comprising the second rocker 210, second pushrod 214 and second upright assembly 216 are arranged to substantially mirror one another about a centreline of the vehicle.

[0192] The suspension system 200 further includes an actuator 218 connected between the first rocker 202 and the second rocker 210, the actuator 218 being operable to control a ride height of the vehicle. A top view of the actuator 218 on its own is shown in Fig. 7. The actuator 218 is a fluid-based actuator, such as a pneumatic or a hydraulic actuator. Other types of actuator, such as an electric or mechanical actuator may also be used. The actuator 218 is a linear actuator, comprising a shaft 220 that extends in a direction linking the first rocker 202 and the second rocker 210, and an engagement element (e.g. flange) 222 which is mounted on the shaft 220. The actuator 218 further includes a fluid chamber 224 from which the shaft 220 extends. The engagement element 222 is connected to a piston in the fluid chamber 224 to move the engagement element 222 along the shaft 220 and relative to the fluid chamber 224. In particular, a pressure (and / or volume) of fluid in the fluid chamber 224 can be controlled, to advance or retract the engagement element 222 along the shaft 220. As shown, the actuator 218 includes a fluid connector 226 for connection to a pressure source (not shown), for controlling a pressure of the fluid in the fluid chamber 224. The actuator 218 further includes a connector 227 for connection to a controller (e.g. the controller 148), in order to receive a control signal from the controller for operating the actuator 218. In particular, the actuator 218 includes a set of internal valves between the fluid connector 226 and the fluid chamber 224, to allow control of the pressure in the fluid chamber 224. The control signal from the controller controls opening and closing of the internal valves, to control pressure in the fluid chamber 224 and thereby control movement of the engagement element 222 along the shaft 220.

[0193] A first spring 228 is mounted on the shaft 220, such that it is connected in series with the actuator 218. A first connector 230 is rigidly connected to a distal end of the shaft 220, the first connector 230 being pivotably connected to the first rocker 202 via a pivot joint 234. A pivot axis between the connector 230 and the first rocker 202 is substantially parallel to the pivot axis of the first pivot joint 204. The engagement element 222 is movable relative to the first spring 228 such that the first spring 228 can be compressed between the engagement element 222 and a flange of the first connector 230. A second connector 232 is provided on a housing of the fluid chamber 224, the second connector 232 being pivotably connected to the second rocker 210 via a pivot joint 236. A pivot axis between the connector 232 and the second rocker 210 is substantially parallel to the pivot axis of the second pivot joint 212. The actuator 238 is thus arranged to control (adjust) a spacing between the pivot joint 234 on the first rocker 202 and the pivot joint 236 on the second rocker 236. In more detail, the actuator 218 can be operated to push the engagement element 222 along the shaft 220 (away from the fluid chamber 224), which causes the engagement element 222 to press against the first spring 228 and pushes the pivot joints 234, 236 away from one another. This in turn results in the first rocker 204 and the second rocker 210 pivoting away from one another about the first and second pivot joints 204, 212, respectively. This also acts to compress the first spring 228 between the engagement element 222 and the flange of the first connector 230.

[0194] The shaft 220 is arranged such that it is extendable from the fluid chamber 224, in response to changes in spacing between the pivot joints 234, 236. In other words, a length of the shaft 220 that protrudes from the housing of the fluid chamber 224 changes as the pivot joints 234, 236 move towards or away from one another. For example, the shaft 220 may be sleeved within the housing of the fluid chamber 224, to allow the shaft 220 to extend from, and partially retract into, the housing of the fluid chamber 224. The shaft 220 may be a concentric sliding shaft which is slidable along an internal shaft mounted within and extending from the fluid chamber 224. A length of the internal shaft is set such that the shaft 220 remains on the internal shaft when the pivot joints 234,236 are maximally spaced.

[0195] It is to be noted that the first rocker 202 and the second rocker 210 are arranged to convert vertical (up and down) motion of the sprung mass of the vehicle into a change in spacing between the pivot joints 234, 236, via pivoting motion of the first and second rockers 202, 210 about the first and second pivot joints 204, 212, respectively. In this manner, a greater the spacing between the pivot joints 234, 236, a greater the ride height of the vehicle. Here, ride height of the vehicle is determined by a height of the first and second pivot joints 204, 212 above the ground surface.

[0196] The suspension system 200 further comprises a spring assembly 238 connected in parallel with the actuator 218. The spring assembly 238 is pivotably connected to the first rocker 202 via a pivot joint 240, and to the second rocker via a pivot joint 242. A pivot axis of the pivot joint 240 may be substantially parallel to the pivot axis of the first pivot joint 204. Likewise, a pivot axis of the pivot joint 242 may be substantially parallel to the pivot axis of the second pivot joint 212. In the example shown, the spring assembly 238 comprises a second spring 244 and a third spring 246 connected in series with one another between the pivot joint 240 and the pivot joint 242. The spring assembly 238 is arranged such that the second and third springs oppose changes in spacing between the pivot joint 234 of the first rocker 202 and the pivot joint 236 of the second rocker 210. For example, the second and third springs 244, 246 may be arranged to be compressed in response to the pivot joints 234, 236 moving towards one another, and to become extended in response to the pivot joints 234, 236 moving apart from one another. Accordingly, the second and third springs 244, 246 are arranged to contribute to a reaction force of the suspension system 200 that opposes a load (loading force) exerted on the suspension system 200. In the example shown, each of the second spring 244 and the third spring 246 comprises a respective coil spring and a damper for damping motion of the coil spring. Other spring types and spring arrangements may also be used. The second and third springs 244, 246 may act as shock absorbers for the suspension system 200.

[0197] A pivotable connection (coupling) 245 may be provided between neighbouring ends of the second and third springs 244, 246, to allow the ends of the second and third springs 244, 246 to pivot relative to one another, e.g. in response to changes in ride height of the vehicle. In particular, an end of the second spring 244 distal to the first rocker 202 is connected to the pivotable connection 245, and an end of the third spring 246 distal to the second rocker 210 is connected to the pivotable connection 245. The pivotable connection 245 may be further connected to the sprung mass of the vehicle, to allow pivoting between the ends of the second and third springs 244, 246 and the sprung mass of the vehicle. For example, a suitable linkage (e.g. bar linkage) may connect the pivotable connection 245 to the sprung mass. In this manner, at least part of the sprung mass of the vehicle may be supported via the pivotable connection 245.

[0198] The actuator 218 is arranged such that it extends across a centreline of the vehicle. For example, the direction of extension of the actuator 218 (i.e. the direction linking the first and second rockers 202, 210) may be substantially parallel to the ground surface on which the vehicle is located. Likewise the spring assembly 238 is arranged to extend across the centreline of the vehicle. Such an arrangement of the actuator 218 and the spring assembly 238 may contribute to reducing a height of the suspension system 200 and of the vehicle. This may also facilitate integrating the suspension system 200 into a small form factor vehicle.

[0199] An operation of the actuator 218 for controlling ride height of the vehicle is illustrated in Figs. 5a to 6b. Figs. 5a and 5b show top and front views, respectively, of part of the suspension system 200 when the actuator 218 is in a first, disengaged state. Figs. 6a and 6b show top and front views, respectively, of part of the suspension system 200 when the actuator 218 is in a second, engaged state. In the disengaged state (Figs. 5a, 5b), the engagement element 222 is spaced apart from the end of the first spring 228, such that there is a gap between the engagement element 222 and the first spring 228. Thus, in the disengaged state, the first spring 228 is not compressed by the engagement element 222, and so does not contribute to the reaction force of the suspension system 200. However, the spring assembly 238 (including the second and third springs 244, 246) remains coupled between the first rocker 202 and the second rocker 210, and so provides the reaction force of the suspension system 200 in the disengaged state. In more detail, a load from the vehicle may be exerted on the suspension system 200 as a downward force on the first pivot joint 204 and the second pivot joint 212. This causes the first and second rockers 202, 210 to pivot towards one another, resulting in the second and third springs 244, 246 being compressed and providing the reaction force of the suspension system 200.

[0200] In the engaged state (Figs. 6a, 6b), the engagement element 222 is advanced along the shaft 220 such that it abuts the end of the first spring 228. In this configuration, the first spring 228 is arranged to contribute to the reaction force in parallel with the spring assembly 238. Thus, the first spring 228 contributes to the stiffness of the suspension system 200, to increase the overall stiffness of the suspension system 200 compared to the disengaged state. In more detail, loading forces exerted downwards on the first and second pivot joints 204, 212 cause the first and second rockers 202, 210 to pivot towards one another, resulting in the first spring 228 becoming compressed between the engagement element 222 and the flange on the first connector 230. Likewise, the springs in the spring assembly 238 become compressed, such that both the spring assembly 238 and the first spring 228 contribute in parallel to the reaction force of the suspension system 200. Accordingly, the actuator 218 can be operated to vary the stiffness of the suspension system 200 (e.g. moving to the engaged state to increase stiffness). Increased stiffness of the suspension system 200 will provide an increased ride height for a given load exerted on the suspension system, such that switching between the engaged and disengaged states can be used to control ride height of the vehicle.

[0201] In the engaged state, the engagement element 222 can be further advanced to increase the compression of the first spring 228. This increases a contribution to the reaction force provided by the first spring 228, which can increase a ride height of the vehicle. Increasing the compression of the spring 228 can further act to cause the first and second rockers 202, 210 to pivot away from one another, in turn increasing the ride height of the vehicle. Accordingly, the actuator 218 can be operated to control ride height (e.g. advancing the engagement element 222 along the shaft 220 to increase ride height).

[0202] Various types of spring may be used to implement the first spring 228, such as a coil spring, a disc spring, a pneumatic spring, or a hydraulic spring. In some cases, the first spring 228 may be arranged such that it has a progressive spring constant which increases with compression. In this manner, when the actuator 218 is in the engaged state, stiffness of the suspension system 200 can increase with compression of the first spring 228. An example of a spring 800 having a progressive spring constant and which may be used as the first spring in an embodiment of the invention is shown in Fig. 8. The spring 800 is composed of a plurality of disc springs 802, with multiple sections including different arrangements of disc springs to provide a progressive spring constant. A first section 804 of the spring 800 includes a first set of disc springs arranged in series with one another, providing a relatively low spring constant. A second section 806 of the spring 800 includes a second set of disc springs in a parallel-series arrangement, where pairs of parallel disc springs are arranged in series with one another. This provides the second section 806 with a higher spring constant compared to the first section 804. A third section 808 of the spring 800 includes a third set of disc springs, where a group of four parallel disc springs is arranged in series with another group of four disc springs, providing the third section 808 with a higher spring constant than the second section 806. As increasing compression forces are applied to the spring 800, the first section 804 will initially be preferentially compressed due to its lower spring constant. Once the travel range of the first section 804 is exhausted, the second section 806 will be preferentially compressed. The third section 808 having a much higher spring constant, may have a relatively low flexibility and travel range, effectively acting as an end stop for compression of the spring 800.

[0203] In some examples, an accumulator may be in fluid communication with the fluid chamber 224 in the fluidbased actuator 218. The accumulator may be a pressurised fluid reservoir, which is arranged to absorb changes in pressure in the fluid chamber 224. This may enable the actuator 218 itself to act as a spring, such that the first spring 228 may no longer be needed. A fluid pressure in the accumulator can then be adjusted to control a spring constant (stiffness) of the fluid-based actuator. It should be noted that the suspension system 200 may in practice have additional linkages which are not shown in the drawings. For example, additional linkages may be provided to couple the first and second upright assemblies 208, 216 together. More generally, the invention can be applied with suspension systems having different forms and different arrangements of linkages.

[0204] Fig. 9 shows a perspective view of the suspension system 200, depicting further linkages of the suspension system and / or vehicle, to further illustrate how the suspension system 200 may be connected in the vehicle. As shown, an anti-roll bar (or torsion bar) 902 is coupled between the first rocker 202 and the second rocker 210. In more detail, a first drop link 904 is pivotably connected to and extends downwards from the first rocker 202, and a second drop link 906 is pivotably connected to and extends downwards from the second rocker 210. A pivot axis between the first drop link 904 and the first rocker 202 is substantially parallel to the pivot axis of the first pivot join 204. Likewise, a pivot axis between the second drop link 906 and the second rocker 210 is substantially parallel to the pivot axis of the second pivot joint 212. The anti-roll bar 902 is connected between ends of the first drop link 904 and the second drop link 906. Each of the first drop link 904 and the second drop link 906 may include a respective pivotable arm at its end, to which the anti-roll bar 902 is connected, so that the anti-roll bar 902 can swing on the ends of the first and second drop links 904, 906.

[0205] A steering rack 908 of the vehicle is connected between the first upright assembly 208 and the second upright assembly 216, via a set of set of linkages. A set of control arms are connected to the first upright assembly 208 and the second upright assembly 216. In more detail, a respective lower front control arm 910 and a respective lower rear control arm 912 are connected at a lower end of each of the first upright assembly 208 and the second upright assembly 216. Further, a respective upper front control arm 914 and a respective upper rear control arm 916 are connected at an upper end of each of the first upright assembly 208 and the second upright assembly 216. The lower front control arms 910, lower rear control arms 912, upper front control arms 914, and upper rear control arms 916 may serve to connect each of the first upright assembly 208 and the second upright assembly 216 to the sprung mass of the vehicle (e.g. to a monocoque of the vehicle).

[0206] It should be noted that, although a multi-link pushrod-type suspension system is described above, other types of suspension system may also be used with the invention.

[0207] Fig. 10 shows a flow diagram of a method 1000 according to an embodiment of the invention. For illustration purposes, the method 1000 is described in the context of the vehicles 100, 170, and 190 and suspension system 200 described above. The steps of the method 1000 may, for example, be implemented by the controller 148, and used to control the actuator (e.g. actuator 218) in the front and / or rear suspension system 140, 142.

[0208] In a step 1002, the method 1000 comprises detecting, with the sensor 150, a parameter indicative of a downforce generated by the active downforce system. This may, for instance, comprise detecting a load exerted on a suspension system of the vehicle 100 resulting from the active downforce system. For example, the sensor 150 may be arranged to detect a parameter indicative of the load exerted on the front and / or rear suspension system 140, 142 as a result of the active downforce system. The sensor 150 may take various forms, depending on the specific parameter to be detected.

[0209] By way of example, the sensor 150 may be arranged to detect an operating parameter of the active downforce system, which may provide an indication of a magnitude of the downforce generated by the downforce system. For instance, the sensor 150 may comprise a sensor for detecting an operating parameter of the airflow generator 126, 192, such as a speed or torque of the airflow generator 126, 192, e.g. where the airflow generator 126, 192 comprises a fan. The sensor 150 may also comprise an airflow sensor for detecting an airflow speed and / or airflow rate generated by the airflow generator 126, 192. In the case of the vehicle 170, the sensor 150 may, for example, detect a flow rate or speed of the gas mixture flowing along the duct 178, and / or a speed of the engine of the vehicle 170.

[0210] As a further example, the sensor 150 may be arranged to detect a pressure in a region under the vehicle. For instance, the sensor 150 may detect a pressure in the region defined under the vehicle 100 by the barrier 102. Thus, the sensor 150 may comprise a pressure sensor located in the region under the vehicle 100, 170, 190. In some cases, a differential pressure sensor may be used, for detecting the pressure differential generated by the airflow generator 126 across the barrier 102.

[0211] As yet another example, the sensor 150 may be arranged to detect a load exerted on the front suspension system 140 and / or the rear suspension system 142. For example, the weight sensor (or pressure sensor) for detecting the load transferred to the suspension system via the first and second pivot joints 204, 212. In order to detect the load exerted on the suspension system, one or more strain gauges may be affixed to linkages in the suspension system. Each strain gauge may be oriented to measure longitudinal strain of a respective linkage, i.e. strain along a longitudinal axis of the linkage. Then, taking into account a geometry of the linkage and a Young’s modulus of the linkage, a load (force) exerted on the linkage can be determined from the strain gauge, which may be indicative of the load exerted on the suspension system. For example, strain gauges may be mounted on one or more of the first and second drop links 904, 906, the first and second pushrods 206, 214, and any of the control arms 910, 912, 914, 916. Output signals from the one or more strain gauges may then be used by the controller 148 to determine loading of the suspension system and to control the actuator accordingly.

[0212] In some cases, the sensor 150 may comprise a ride height detector, e.g. for detecting a height of the underside 106 of the vehicle 100 above the ground surface 114, to provide an indication of the load exerted on the suspension system. Use of a ride height detector may facilitate achieving a desired ride height, by enabling the controller 148 to directly monitor the ride height and control the actuator accordingly. The ride height detector may be implemented using a distance sensor configured to detect a distance between the underside 106 of the vehicle and the ground surface 114. For example, the distance sensor may be a laser-based distance (or displacement) sensor, or similar.

[0213] The sensor 150 generates an output signal which provides an indication of a value of the detected parameter, the output signal being conveyed to the controller 148. In some cases, multiple sensors can be used for detecting different parameters in the vehicle 100 that provide an indication of the load exerted on the suspension system. In such a case, the controller 148 can be arranged to receive the output signals from each sensor.

[0214] In step 1004, the method 1000 comprises controlling an actuator in the suspension system, e.g. the actuator 218 in the suspension system 200, as a function of the detected parameter (or as a function of the output signal), to control the ride height of the vehicle. The controller 148 may, for example, implement an algorithm which takes as an input the output signal from the sensor 150 (or from multiple sensors if applicable), and in response generates a control signal for controlling the actuator 118. For example, the controller 148 may be configured to determine a target position of the engagement element 222 along the shaft 220 of the actuator 218 based on the output signal from the sensor 150, and to generate a control signal to cause the actuator 218 to move the engagement element 222 to the determined position.

[0215] Various types of control may be performed by the controller 148. In some cases, the controller 148 may be configured to control the actuator 218 to maintain a predetermined ride height of the vehicle 100. The predetermined ride height may be pre-programmed in the controller. Additionally or alternatively, the predetermined ride height may be set or selected by a user. The controller 148 may comprise or be connected to a suitable user interface, to allow the user to select a desired ride height of the vehicle 100. The controller 148 can then operate the actuator 218 to compensate for changes in load on the suspension system 200 caused by the active downforce system, in order to maintain the predetermined ride height. For example, if the output signal received from the sensor 150 indicates an increase in the load exerted on suspension system 200 (e.g. due to activation of the downforce system or an increase in the generated downforce), the controller 148 can control the actuator 218 to set the spacing between the pivot joints 234, 236 on the first and second rockers 202, 210 to achieve the predetermined ride height.

[0216] In more detail, the controller 148 may be configured to determine a target position of the engagement element 222, e.g. a target distance along the shaft, as a function of the output signal from the sensor 150, and as a function of the predetermined distance. To achieve this, the algorithm implemented by the controller 148 may make use of a predetermined function (relationship) that provides target positions of the engagement element 222 as a function of values of the output signal of the sensor 150, for that predetermined height. Where there are multiple selectable ride heights, there may be such a predetermined function for each selectable height, to so that the controller 148 can adapt the position of the engagement element 122 to achieve the desired ride height. The predetermined function may be determined, for example, based on experimental or calibration measurements with the downforce system and sensor 150, and / or based on a theoretical model of downforce system and suspension system 200.

[0217] The controller 148 can perform PID control in order to achieve and maintain the predetermined ride height. In particular, the controller 148 can control the actuator 218 (i.e. the position of the engagement element 222) using a PID control loop, which may take as inputs the predetermined ride height and the output signal from the sensor 150. Use of a PID control loop in this manner may minimise overshooting of the predetermined ride height, as well as reduce settling time at the predetermined ride height (e.g. an amount of time the suspension system oscillates around the predetermined ride height). PID control also enables further fine-tuning of the suspension system 200. For example, parameters of the PID control (e.g. gains, coefficients, system variables) may be adjustable to tailor response of the suspension system

[0218] 200 to different driving conditions or scenarios, e.g. to prioritise vehicle performance or driver comfort.

[0219] As another example, the controller 148 may be configured to control the stiffness of the suspension system 200 as a function of the output signal from the sensor 150. For instance, the controller 148 may be configured to increase the stiffness of the suspension system 200, if the output signal from the sensor 150 indicates that the downforce system has been activated, and / or if the output signal from the sensor 150 indicates that the generated downforce has increased. Thus, in line with the above discussion, the controller 148 may control the actuator 218 to put the actuator in the engaged state in response to a determination that the downforce system is activated, and / or that the generated downforce has increased. Similarly to the above, the controller 148 may perform PID control for controlling the stiffness of the suspension system 200 as a function of the output signal from the sensor 150.

[0220] Where both the front suspension 140 and the rear suspension 142 have an actuator operable to control the ride height (e.g. actuator 218), the controller 148 may be configured to control the actuators in both the front and rear suspension systems 140, 142 together. Alternatively, the controller may be configured to control the actuators in the front and rear suspension systems 140, 142 separately. For example, different predetermined ride heights may be set for the front and rear suspension systems 140, 142, to achieve a desired pitch of the vehicle 100. In some cases, separate sensors may be provided for the front and rear suspension systems 140, 142, e.g. to detect parameters indicative of the load exerted on the front and rear suspension systems 140, 142 respectively. The controller may then control the actuator in each suspension system independently, using the output from the sensor for that suspension system.

[0221] In some cases, the step 1004 may involve controlling the actuator to control the downforce generated by the active downforce system. In particular, the actuator can be operated to adjust the ride height of the vehicle, to achieve a target downforce acting on the vehicle. The detected parameter, which provides an indication of the generated downforce, may be used as feedback in a control loop for adjusting the position of the actuator to achieve or maintain the target downforce.

[0222] In some cases, both the actuator in the suspension system and an operating parameter of the active downforce system can be controlled simultaneously be the controller 148, e.g. to achieve a desired downforce and aerodynamic performance of the vehicle. For example, the actuator may be controlled to maintain a desired ride height of the vehicle, whilst an operating parameter of the downforce system is controlled to achieve a desired downforce.

[0223] The controller 148 of any of the vehicles 100, 170, 190 described above may implement a safety system configured to detect a safety risk associated with operation of the active downforce system. The controller 148 may be coupled to one or more sensors (not shown) in the vehicle for detecting the occurrence of one or more conditions such as: damage to a component of the downforce system or the vehicle, a fault in the airflow generator or other part of the downforce system, a fault (or damage to) an energy store of the vehicle used power the downforce system, a low remaining energy level of the energy store, overheating of a component. If the controller 148 detects from one of the sensors occurrence of any such condition, the controller 148 may generate an alert and / or operate the vehicle in a safety mode. Operating the vehicle in the safety mode may comprise limiting one or more operating parameters of the vehicle, e.g. to limit or reduce various outputs of the vehicle. This may involve, for example, reducing a maximum speed of the vehicle, a maximum power output of the vehicle engine, a maximum downforce generated by the downforce system, a maximum associated with the airflow generator (e.g. fan speed, fan torque, airflow speed, airflow rate).

[0224] In some implementations, the controller 148 may comprise a memory storing a plurality use profiles (or operating modes). The user interface may enable a user to select one of the plurality of use profiles, following which the controller 148 controls the actuator of the suspension systems 140, 142 and / or the downforce system. For example, each use profile may be associated with one or more predetermined settings for the front suspension system 140 and / or the rear suspension system 142. The one or more predetermined settings may, for example, include a target ride height, a suspension stiffness, and / or a position of each actuator. The controller 148 may then control the actuator(s) in accordance with the one or more predetermined settings, e.g. to set a target ride height for the front and rear of the vehicle. Additionally, each of the use profiles may be associated with one or more predetermined operating parameters for the downforce system. The one or more predetermined operating parameters for the downforce system may include a target downforce magnitude, a fan speed, air flow rate, pressure, height of the rim 118, etc. The controller 148 can then operate the downforce system in accordance with the one or more predetermined operating parameters associated with the selected use profile. In this manner, when a user selects on of the plurality of use profiles, both the suspension system and the downforce system may be synchronously controlled based on the stored settings and operating parameters for the selected use profile.

[0225] The features disclosed in the foregoing description, or in the following claims, or in the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for obtaining the disclosed results, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

[0226] While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the invention.

[0227] For the avoidance of any doubt, any theoretical explanations provided herein are provided for the purposes of improving the understanding of a reader. The inventors do not wish to be bound by any of these theoretical explanations.

[0228] Any section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described.

[0229] Throughout this specification, including the claims which follow, unless the context requires otherwise, the word “comprise” and “include”, and variations such as “comprises”, “comprising”, and “including” will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

[0230] It must be noted that, as used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from “about” one particular value, and / or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and / or to the other particular value. Similarly, when values are expressed as approximations, by the use of the antecedent “about,” it will be understood that the particular value forms another embodiment. The term “about” in relation to a numerical value is optional and means for example + / - 10%.

Claims

Claims:1 . A ride height control system for a vehicle comprising an active downforce system configured to generate a downforce acting on the vehicle, the ride height control system comprising: a suspension system for supporting a sprung mass of the vehicle, wherein the suspension system comprises an actuator operable to control a ride height of the vehicle; a sensor configured to detect a parameter indicative of a downforce generated by the active downforce system; and a controller configured to operate the actuator as a function of an output signal from the sensor.

2. A ride height control system according to claim 1 , wherein the controller is configured to operate the actuator to maintain a predetermined ride height of the vehicle.

3. A ride height control system according to claim 1 or 2, wherein the controller is configured to operate the actuator to at least partially compensate for a load exerted on the suspension system resulting from the downforce system.

4. A ride height control system according to any preceding claim, wherein the actuator is operable to adjust a stiffness of the suspension system.

5. A ride height control system according to any preceding claim, wherein the controller is configured to operate the actuator to control the downforce generated by the active downforce system.

6. A ride height control system according to any preceding claim, wherein: the suspension system comprises a first linkage and a second linkage, the ride height of the vehicle being dependent on a spacing between the first linkage and the second linkage; and the actuator is operable to adjust the spacing between the first linkage and the second linkage.

7. A ride height control system according to any preceding claim, further comprising a first spring arranged to contribute to a reaction force of the suspension system opposing a load exerted on the suspension system, wherein the actuator is operable to adjust a length of the first spring.

8. A ride height control system according to claims 6 and 7, wherein the actuator comprises a linear actuator, and the linear actuator and the first spring are connected in series between the first linkage and the second linkage.

9. A ride height control system according to claim 7 or 8, wherein: the actuator is movable between an engaged state where the actuator is engaged with an end of the first spring, and a disengaged state where the actuator is disengaged from the end of the first spring; andwhen the actuator is in the disengaged state, the first spring does not contribute to the reaction force.

10. A ride height control system according to claim 9, wherein: the controller is configured to put the actuator in the disengaged state when the active downforce system is in an off state; and / or the controller is configured to put the actuator in the engaged state when the active downforce system activated.

11. A ride height control system according to any of claims 7 to 10, wherein the first spring comprises a progressive spring constant, such that the spring constant of the first spring increases with compression of the first spring.

12. A vehicle according to claim 11 , wherein the first spring comprises a first section and a second section arranged in series, the first section comprising a plurality of disc springs arranged in series, and the second section comprising a plurality of disc springs arranged in parallel.

13. A ride height control system according to any preceding claim, wherein the suspension system further comprises a second spring arranged in parallel with the actuator.

14. A ride height control system according to any preceding claim, wherein the actuator comprises a fluid-based actuator; and optionally further comprising an accumulator in fluid communication with a fluid chamber in the fluid-based actuator.

15. A ride height control system according to any preceding claim, wherein the sensor is configured to detect an operating parameter of the active downforce system.

16. A ride height control system according to claim 15, wherein the operating parameter of the active downforce system comprises one or more of: an operating parameter of an airflow generator of the active downforce system; and an air pressure in a region under the vehicle acted on by the active downforce system.

17. A ride height control system according to any preceding claim, wherein: the suspension system comprises a front suspension system arranged to connect the sprung mass of the vehicle to front wheels of the vehicle, and a rear suspension system arranged to connect the sprung mass to rear wheels of the vehicle; and the actuator comprises a first actuator in the front suspension system operable to adjust a ride height of a front of the vehicle, and a second actuator in the rear suspension system operable to adjust a ride height of a rear of the vehicle.

18. A ride height control system according to claim 17, wherein the controller is configured to independently operate the first actuator and the second actuator.

19. A ride height control system according to any preceding claim, wherein the controller comprises a user interface for receiving a user input, wherein the controller is further configured to operate the actuator as a function of the user input.

20. A vehicle comprising: an active downforce system comprising an airflow generator configured to produce an airflow for generating a downforce acting on the vehicle; and a ride height control system according to any preceding claim.21 . A vehicle according to claim 20, wherein the active downforce system comprises a barrier arranged to extend downwards from an underside of the vehicle to restrict airflow into a region under the vehicle, and wherein the airflow generator is configured to remove air from the region under the vehicle to generate a pressure differential across the barrier.

22. A vehicle according to claim 20 or 21 , wherein the active downforce system comprises a diffuser on an underside of the vehicle, and the airflow generator is arranged to cause an airflow in the diffuser.

23. A vehicle according to one of claims 20 to 22, further comprising a safety system configured to: detect a safety risk associated with operation of the active downforce system; and in response to detection of a safety risk, generate an alert and / or cause the vehicle to be operated in a safety mode.

24. A vehicle according to claim 23, wherein the safety system is configured to detect a safety risk if a remaining energy level in an energy store of the vehicle is below a predetermined level.

25. A vehicle according to claim 23 or 24, wherein operating the vehicle in the safety mode comprises reducing an upper limit associated with an operating parameter of the vehicle.

26. A vehicle according to one of claims 20 to 25, wherein the downforce system comprises at least two airflow generators, each airflow generator being configured to produce an airflow for generating a downforce acting on the vehicle.

27. A method of controlling a ride height of a vehicle, the vehicle comprising an active downforce system configured to generate a downforce acting on the vehicle, the method comprising: detecting, with a sensor, a parameter indicative of a downforce generated by the active downforce system, wherein the suspension system is arranged to support a sprung mass of the vehicle; controlling, as a function of an output signal from the sensor, operation of an actuator of the suspension system, wherein the actuator is operable to adjust a ride height of the vehicle.

28. A method according to claim 27, comprising controlling the actuator to maintain a predetermined ride height of the vehicle.

29. A method according to claim 27 or 28, comprising controlling the actuator to adjust the downforce generated by the active downforce system.

30. A method according to one of claims 27 to 29, wherein the actuator is operable to adjust a stiffness of the suspension system, the method comprising controlling operation of the actuator to adjust a stiffness of the suspension system as a function of the output signal from the sensor.

Images