Hydraulic control apparatus for a piston actuator of an active suspension system of a vehicle

Abstract

Aspects of the present invention relate to a hydraulic control apparatus for a piston actuator of an active suspension system of a vehicle, the hydraulic control apparatus comprising: a first hydraulic gallery hydraulically couplable to a first fluid chamber of the piston actuator; a second hydraulic gallery hydraulically couplable to a second fluid chamber of the piston actuator; a third hydraulic gallery connected to the first and second hydraulic galleries; a fourth hydraulic gallery connected to the first, second and third hydraulic galleries; a first valve connecting the fourth hydraulic gallery to the first hydraulic gallery; a second valve connecting the second hydraulic gallery to the third hydraulic gallery; and a filter positioned such that hydraulic fluid flow from the third hydraulic gallery to the fourth hydraulic gallery passes through the filter.

Description

[0001] HYDRAULIC CONTROL APPARATUS FOR A PISTON ACTUATOR OF AN ACTIVE SUSPENSION SYSTEM OF A VEHICLE

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to a hydraulic control apparatus for a piston actuator of an active suspension system of a vehicle. Aspects of the invention relate to a hydraulic control apparatus, an active suspension system, and a vehicle.

[0004] BACKGROUND

[0005] An active suspension system of a vehicle can be hydraulically-actuated. Hydraulic actuation is controlled by a hydraulic control apparatus comprising hydraulic circuits. To maintain cleanliness of the hydraulic fluid throughout the lifetime of the suspension system it would be helpful to be able to filter the hydraulic fluid. However, active suspension systems typically require bi-directional flow.

[0006] It is an aim of the present invention to address one or more of the disadvantages associated with the prior art.

[0007] SUMMARY OF THE INVENTION

[0008] Aspects and embodiments of the invention provide a hydraulic control apparatus, an active suspension system, and a vehicle as claimed in the appended claims.

[0009] According to an aspect of the invention there is provided a hydraulic control apparatus for a piston actuator of an active suspension system of a vehicle, the hydraulic control apparatus comprising: a plurality of connected hydraulic galleries; and a filter positioned such that fluid flow through or between hydraulic galleries of the plurality of connected hydraulic galleries passes through the filter.

[0010] According to an aspect of the invention there is provided a hydraulic control apparatus for a piston actuator of an active suspension system of a vehicle, the hydraulic control apparatus comprising: a first hydraulic gallery hydraulically couplable to a first fluid chamber of the piston actuator; a second hydraulic gallery hydraulically couplable to a second fluid chamber of the piston actuator; a third hydraulic gallery connected to the first and second hydraulic galleries; a fourth hydraulic gallery connected to the first, second and third hydraulic galleries; a first valve connecting the fourth hydraulic gallery to the first hydraulic gallery, wherein the first valve is biased towards a closed position and arranged to permit flow of hydraulic fluid from the fourth hydraulic gallery to the first hydraulic gallery when open; a second valve connecting the second hydraulic gallery to the third hydraulic gallery, wherein the second valve is arranged to permit one-way hydraulic fluid flow from the second hydraulic gallery to the third hydraulic gallery, and wherein the second valve is controllable to control a pressure across the second valve; and a filter positioned such that hydraulic fluid flow from the third hydraulic gallery to the fourth hydraulic gallery passes through the filter.

[0011] Advantageously, the hydraulic fluid is filtered as it passes through the filter. The arrangement of valves is such that the flow through the filter is uni-directional. In this manner, filtered contamination is not flushed back out of the filter. More specifically, for a flow path from the second hydraulic gallery to the first hydraulic gallery the flow passes: through the second valve from the second hydraulic gallery to the third hydraulic gallery; from the third hydraulic gallery to the fourth hydraulic gallery, passing through the filter; through the first valve from the fourth hydraulic gallery to first hydraulic gallery. By configuring the hydraulic control apparatus such that there is uni-directional flow through the filter, effective filtering is achieved without the use of additional check valves, which lead to additional system pressure drop, cost and weight.

[0012] In certain embodiments the hydraulic control apparatus comprises: a third valve connecting the fourth hydraulic gallery to the second hydraulic gallery, wherein the third valve is biased towards a closed position and arranged to permit flow of hydraulic fluid from the fourth hydraulic gallery to the second hydraulic gallery when open; and a fourth valve connecting the first hydraulic gallery to the third hydraulic gallery, wherein the fourth valve is arranged to permit one-way hydraulic fluid flow from the first hydraulic gallery to the third hydraulic gallery, and wherein the fourth valve is controllable to control a pressure across the fourth valve.

[0013] Advantageously uni-directional flow through the filter is irrespective of the fluid flow through the system. Specifically, flow goes uni-directionally through the filter irrespective of whether the flow is going: from the second hydraulic gallery to the first hydraulic gallery (through the second valve, through the filter, through the first valve); or from the first hydraulic gallery to the second hydraulic gallery (through the fourth valve, through the filter, through the third valve).

[0014] In certain embodiments, the third hydraulic gallery or fourth hydraulic gallery comprises a hydraulic accumulator. Advantageously, accumulators enable control of fluid volume during suspension disturbance events.

[0015] In certain embodiments, the hydraulic control apparatus comprises one or more seal elements configured to prevent hydraulic fluid flow from an outlet of the second valve and / or the third hydraulic gallery to an inlet of the third valve and / or the fourth hydraulic gallery. Advantageously, the presence of the one or more seal elements helps ensure hydraulic fluid flow is directed uni-directionally through the filter. That is, the one or more seal elements help ensure the filter is not bypassed as hydraulic fluid flows from an outlet of the second valve or the third hydraulic gallery to an inlet of the third valve.

[0016] In certain embodiments, the hydraulic control apparatus comprises one or more seal elements configured to prevent hydraulic fluid flow from an outlet of the fourth valve or the third hydraulic gallery to an inlet of the first valve and / or the fourth hydraulic gallery. Advantageously, the presence of one or more seal elements helps ensure hydraulic fluid flow is directed uni-directionally through the filter. That is, the one or more seal elements help ensure the filter is not bypassed as hydraulic fluid flows from an outlet of the fourth valve or the third hydraulic gallery to an inlet of the first valve.

[0017] In certain embodiments, the filter comprises one or more seal elements configured to prevent hydraulic fluid flow around the filter from the third hydraulic gallery to the fourth hydraulic gallery. Advantageously, the presence of the one or more seal elements around the filter helps ensure hydraulic fluid flow does not bypass the filter.

[0018] In certain embodiments, the second valve and the third valve are integral within a sleeve member. Advantageously integrating the second valve and third valve within a sleeve member helps reduce package space, cost and weight.

[0019] In certain embodiments, the first valve and the fourth valve are integral within a sleeve member. Advantageously integrating the first valve and fourth valve within a sleeve member helps reduce package space, cost and weight.

[0020] In certain embodiments, the hydraulic control apparatus comprises a pump operable to control flow rate and / or pressure in the first hydraulic gallery and second hydraulic gallery. In certain embodiments, the pump is operable to pump hydraulic fluid between the first hydraulic gallery and the second hydraulic gallery.

[0021] In certain embodiments, each of the third hydraulic gallery and the fourth hydraulic gallery is a channel element. Advantageously, providing each of the third hydraulic gallery and the fourth hydraulic gallery as a channel element, rather than an open volume, helps restrict the hydraulic fluid flow to a particular flow path. In turn, this helps ensure the hydraulic flow can be directed uni-directionally through the filter.

[0022] In certain embodiments, all hydraulic fluid flow from the third hydraulic gallery to the fourth hydraulic gallery passes through the filter. Advantageously, this helps ensure that all hydraulic fluid is filtered by a single filter as it is circulated through the system. As such, filtration of the hydraulic fluid is achieved without the necessity for additional check valves that are required only for the filtration process.

[0023] According to another aspect of the invention there is provided an active suspension system comprising: the hydraulic control apparatus of any aspect or embodiment of the invention; and the piston actuator.

[0024] According to yet another aspect of the invention there is provided a vehicle comprising an active suspension system of according to any aspect or embodiment of the invention.

[0025] In certain embodiments the vehicle comprises one of said active suspension system for each of a plurality of wheels of the vehicle. Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and / or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and / or features of any embodiment can be combined in any way and / or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and / or incorporate any feature of any other claim although not originally claimed in that manner.

[0026] BRIEF DESCRIPTION OF THE DRAWINGS

[0027] One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0028] FIG. 1 illustrates an example of a vehicle;

[0029] FIG. 2 illustrates an example of an active suspension system of a vehicle;

[0030] FIG. 3 illustrates an example of an actuator system of an active suspension system;

[0031] FIGS. 4 and 5 illustrate another example of an actuator system of an active suspension system;

[0032] FIGS. 6 and 7 illustrate another example of an actuator system of an active suspension system;

[0033] FIGS. 8 and 9 illustrate another example of an actuator system of an active suspension system;

[0034] FIG. 10 illustrates an example valve configuration;

[0035] FIG. 11 illustrates an example control system; and

[0036] FIG. 12 illustrates an example non-transitory storage medium.

[0037] DETAILED DESCRIPTION

[0038] A vehicle 1 in accordance with an embodiment of the present invention is described herein with reference to the accompanying FIG. 1. In some, but not necessarily all examples, the vehicle 1 is a passenger vehicle, also referred to as a passenger car or as an automobile. In other examples, embodiments of the invention can be implemented for other applications, such as commercial vehicles.

[0039] FIG. 1 is a front perspective view and illustrates a longitudinal x-axis between the front and rear of the vehicle 1 representing a centreline, an orthogonal lateral y-axis between left and right lateral sides of the vehicle 1 , and a vertical z-axis. A forward / fore direction typically faced by a driver’s seat is in the negative x-direction; rearward / aft is +x. A rightward direction as seen from the driver’s seat is in the positive y-direction; leftward is -y. These are a first lateral direction and a second lateral direction.

[0040] In summary, FIGS. 2 and 3 illustrate an example of a hydraulic control apparatus 17 for a piston actuator 502 (e.g., FIG. 3) of an active suspension system 104 of a vehicle 1 , the hydraulic control apparatus 17 comprising: a first hydraulic gallery G1 hydraulically couplable to a first fluid chamber C1 of the piston actuator 502; a second hydraulic gallery G2 hydraulically couplable to a second fluid chamber C2 of the piston actuator 502; a third hydraulic gallery G3 connected to the first and second hydraulic galleries G1 , G2; a fourth hydraulic gallery G4 connected to the first, second and third hydraulic galleries G1 , G2, G3; a first valve X1 connecting the fourth hydraulic gallery G4 to the first hydraulic gallery G1 , wherein the first valve X1 is biased towards a closed position and arranged to permit flow of hydraulic fluid from the fourth hydraulic gallery G4 to the first hydraulic gallery G1 when open; a second valve V4 connecting the second hydraulic gallery G2 to the third hydraulic gallery G3, wherein the second valve V4 is arranged to permit one-way hydraulic fluid flow from the second hydraulic gallery G2 to the third hydraulic gallery G3, and wherein the second valve V4 is controllable to control a pressure across the second valve V4; and a filter F positioned such that hydraulic fluid flow from the third hydraulic gallery G3 to the fourth hydraulic gallery G4 passes through the filter F.

[0041] The term ‘connected’ herein means fluidly connected / hydraulically coupled.

[0042] In the particular example shown in FIGS. 2 and 3, the hydraulic control apparatus 17 further comprises: a third valve X2 connecting the fourth hydraulic gallery G4 to the second hydraulic gallery G2, wherein the third valve X2 is biased towards a closed position and arranged to permit flow of hydraulic fluid from the fourth hydraulic gallery G4 to the second hydraulic gallery G2 when open; and a fourth valve V2 connecting the first hydraulic gallery G1 to the third hydraulic gallery G3, wherein the fourth valve V2 is arranged to permit one-way hydraulic fluid flow from the first hydraulic gallery G1 to the third hydraulic gallery G3, and wherein the fourth valve V2 is controllable to control a pressure across the fourth valve V2.

[0043] First, an active suspension system 104 is described with reference to FIG. 2. FIG. 2 illustrates an example active suspension system 104 of the vehicle 1 , connecting a vehicle body 102 to vehicle wheels 12.

[0044] The active suspension system 104 comprises front left active suspension 106 for a front left wheel FL, front right active suspension 116 for a front right wheel FR, rear left active suspension 108 for a rear left wheel RL, and rear right active suspension 1 18 for a rear right wheel RR. The active suspension for each wheel (e.g. quarter / corner) of the vehicle 1 may be individually controllable by a control system 200.

[0045] FIG. 2 also shows a torque source 103 such as an internal combustion engine or electric machine, for driving at least some of the vehicle wheels 12.

[0046] The active suspension 106, 116, 108, 118 for each corner of the vehicle 1 comprises an actuator 502.

[0047] As will be described, the actuator 502 is a hydraulic actuator such as a hydraulic fluid-filled chamber containing a piston 24 (as shown in FIG. 3). The actuator 502 is therefore a piston actuator of a hydraulic system. The fluid may comprise hydraulic oil. One end of the actuator 502 is coupled to a vehicle wheel 12 and the other end is coupled to the vehicle body 102. A spring 504 (e.g. coil or pneumatic) may be in equilibrium and acting in parallel with the actuator 502. When the active suspension system 104 is undisturbed, the piston 24 of the hydraulic actuator 502 sits at a neutral position in the chamber.

[0048] The piston 24 can move in either direction inside the chamber, e.g. due to a road disturbance or body accelerations compressing or extending the actuator 502. As will be described, the piston 24 can displace fluid out of the chamber into hydraulic circuits (shown later). The fluid imparts a restoring force against movement of the piston 24. Energy can be added to and / or extracted from the actuator 502 by pumping fluid and / or controlling valves to regulate fluid pressure to either side of the piston 24.

[0049] The damping of the actuator 502 can be modified by controlling a damper valve at a constriction, which regulates the force realized by the fluid transferred in and out of the actuator 502 by movement of the piston 24. Bump and rebound damping rates could be controlled independently in some examples.

[0050] Further, energy can be added to or removed from the actuator 502 in order to control various suspension characteristics including, but not limited to the damping curve (force-velocity relationship) of the actuator 502.

[0051] In FIG. 2 but not necessarily all examples, the spring 504 comprises an active spring such as a pneumatic spring, enabling control of ride height. The control system 200 may be configured to pump gas (e.g. air) in or out of the pneumatic spring 504 to control ride height.

[0052] Energy can be added to or removed from the pneumatic spring 504 in order to increase or decrease the volume of the pneumatic spring 504. Increasing the volume can lift the vehicle body 102 in the z-axis. In the example of FIG. 2 this enables the wheel-to-body distance to be changed independently at different ends and / or at different corners of the vehicle 1 .

[0053] Additionally or alternatively, the spring 504 comprises a passive spring (e.g. coil) or is omitted entirely.

[0054] Control of the active suspension system 104 relies on one or more sensors. Wheel travel may be sensed by a wheel-to-body displacement sensor 514 (suspension displacement-based sensor), for example. The wheel- to-body displacement sensor 514 is placed somewhere on the active suspension 106, 116, 108, 118 and can sense the position of the wheel 12 along an arc defined by suspension geometry. An example of a wheel-to- body displacement sensor 514 is a rotary potentiometer attached to a lever, wherein one end of the lever is coupled to the vehicle body 102, and the other end is coupled to a suspension link.

[0055] In some examples, the control system 200 more accurately determines the wheel travel and / or its associated derivatives by fusing information from the wheel-to-body displacement sensor 514 with information from hub accelerometers 516.

[0056] In at least some examples the control system 200 is configured to control the active suspension system 104 by transmitting a force request to the active suspension 106, 1 16, 108, 118 or to a low-level controller thereof. The force request may be an arbitrated force request based on requests from various requestors and information from various sensors.

[0057] FIG. 2 illustrates additional optional features that may interact with the control system 200 to influence force request calculation. These include any one or more of:

[0058] - a hub-mounted accelerometer 516 for each wheel 12, coupled to the unsprung mass of the vehicle 1 .

[0059] - at least one vehicle body accelerometer 522 coupled to the vehicle body 102 (sprung mass). A particular example includes a 3DOF or 6DOF inertial measurement unit (IMU). A unit may comprise an accelerometer or a multi-axis set of accelerometers.

[0060] FIG. 3 illustrates an example actuator system 16 comprising an actuator 502 and a hydraulic control apparatus 17 for the actuator 502. A topology of the hydraulic control apparatus 17 is shown. The hydraulic control apparatus 17 comprises hydraulic circuits 28, 29. The hydraulic control apparatus 17 is hydraulically coupled or couplable to the actuator 502 by galleries 30, 32.

[0061] Where multiple active suspensions 106, 108, 116, 118 are provided, the actuator system 16 can comprise the actuators 502 of each of the active suspensions 106, 108, 1 16, 118, and the hydraulic control apparatus 17 for each actuator 502.

[0062] In an implementation, the active suspension system 104 comprises an independent hydraulic control apparatus 17 for each corner of the vehicle 1 (each actuator 502), wherein the control system 200 is configured to determine independent control signals for each of the independent hydraulic circuits to provide a Fully Active Suspension (FAS) function.

[0063] However, the hydraulic control apparatus 17 is not limited to that shown in FIG. 3, which is for illustrative purposes only. Aspects of the invention are applicable to other suspension hydraulic circuit arrangements having multiple hydraulic circuits and valves. For example, aspects of the invention may be applicable to a semi-active system such as a system in which a hydraulic circuit is shared between a pair of laterally separated wheels 12 of the vehicle 1 , such that the active suspension system 104 is configured to provide an Active Roll Control (ARC) function.

[0064] In FIG. 3, the actuator 502 includes a cylinder 22 containing the piston 24. The cylinder 22 is secured to the wheel 12 and the piston 24 is secured to the vehicle body 102 via a rod 26. The piston 24 defines a first fluid chamber C1 and a second fluid chamber C2. The piston 24 fluidly isolates the first fluid chamber C1 from the second fluid chamber C2. In the illustrated example, the first fluid chamber C1 is an annulus chamber and the second fluid chamber C2 is a piston chamber. In another example, the direction of the actuator 502 is reversed so that the cylinder 22 is secured to the vehicle body 102 via rod 26, and the piston 24 is secured to the wheel 12.

[0065] The hydraulic control apparatus 17 includes a hydraulic pump P having a first port PP1 and a second port PP2. In the illustrated example, the pump P is bi-directional so as to selectively generate flow out of the first port PP1 or second port PP2. In other examples, separate single-direction pumps are provided, or a single-direction pump is connected to a direction-controlling valve.

[0066] The hydraulic control apparatus 17 of FIG. 3 includes valves V1 and V3. The valves V1 and V3 may be electromagnetically controlled. In this example, valve V1 includes a damper valve V1A and a check valve V1 B. Similarly, in this example, valve V3 includes a damper valve V3A and a check valve V3B.

[0067] The hydraulic control apparatus 17 of FIG. 3 includes valves V2 and V4. The valves V2 and V4 may be electromagnetically controlled. In this example, valves V2 and V4 are both variable pressure control valves (PCVs). Valves V2 and V4 may have a pilot stage and a main stage. Valves V2 and V4 have controllable orifice sizes to control pressure. The pilot stage may have a small, magnetically actuated poppet valve, to generate a pressure in a chamber that then acts on the larger main stage. The main stage may be closed by a spring and forced open by fluid flow from the actuator 502, opposed by the spring and pressure force generated by the pilot stage (or a magnetic force if there is no pilot stage). The valves V2 and V4 may be normally closed and may allow one-way flow. In other examples, the valves V2 and V4 comprise a different type of hydraulic valve.

[0068] The illustrated hydraulic control apparatus 17 includes hydraulic galleries G1 , G2, G3 and G4. In this example, the illustrated hydraulic control apparatus 17 also includes hydraulic accumulators A1 , A2, A3.

[0069] The hydraulic control apparatus 17 includes check valves X1 and X2. As schematically illustrated in FIG. 10, a check valve X may include a closing member 602 such as a ball or spool in a sleeve, and a self-returner 604A such as a bias (e.g. spring such as a coil spring), and a seat 606. The illustrated self-returner 604A may bias the closing member 602 of the check valve X towards an open position (away from seat 606), such that the check valve X is normally open. In other examples, the seat 606 may be located at the opposite side of the closing member 602 or the bias direction may be reversed, so that the closing member 602 is biased towards a closed position (towards seat 606) such that the check valve X is normally closed. In some examples the closing member 602 may include an aperture or bore extending therethrough. Hydraulic fluid may pass through the aperture or bore even when the closing member 602 is in the closed position (see the examples of Figures 7 to 9, for example).

[0070] The term ‘normally closed’ refers to the direction of feree of the valve’s provided self-returner 604A (e.g., bias). The term ‘cracking pressure setting’ refers to the minimum pressure differential needed between the inlet X11 or X2I and outlet X1 O or X2O of the check valve X1 or X2 at which steady flow first occurs. The cracking pressure setting is determined by factors such as the bias force of the valve’s provided self-returner 604A (e.g., stiffness of provided bias), and / or any weight forces holding of the valve against its seat. The cracking pressure setting of the check valve X1 , X2 is arranged to bias the check valve X1 , X2 towards the valve’s closed position to prevent hydraulic fluid flow from the respective gallery G1 or G2 into gallery G4 and to permit flow of hydraulic fluid from gallery G4 to the respective gallery G1 or G2 when the check valve X1 , X2 is open. The cracking pressure setting of the check valves X1 , X2 may be a value set by the manufacturer. The value is a balance of overcoming the friction force of the valve spool in the sleeve to close, and having a low pressure drop across the valve to open and after opening, so as to minimise an effect of the valve on wheel damping. An example of the value is 25 kilopascals (0.25bar / 0.25 atmosphere). Although there is no specific limit, the value is unlikely to be less than 10 kilopascals. During a vacuum operation, the check valves X1 , X2 can reseal with tens of kilopascals of air pressure still remaining in gallery G4.

[0071] In this example, gallery G1 connects port PP1 of pump P, outlet X10 of check valve X1 , inlet V2I of valve V2, hydraulic accumulator A1 , and port V1 C of valve V1. In this example, the valves V2 and X1 are shown in parallel fluid passages P2 and P1 , respectively. The respective valves of V2 and X1 are configured to control fluid flow through their respective fluid passages P2, P1 .

[0072] In this example, gallery G2 connects port PP2 of pump P with outlet X2O of check valve X2, inlet V4I of valve V4, hydraulic accumulator A3, and port V3C of valve V3. In this example, the valves V4 and X2 are shown in parallel fluid passages P3, P4, respectively. The respective valves V4, X2 are configured to control fluid flow through their respective fluid passages P3, P4.

[0073] In some examples, the particular position of the pump P may deviate from that shown in FIG. 3.

[0074] The fluid passages P1 , P2, P3, P4 may be channel elements (as depicted) or ports which interface the valves V2, X1 , V4, X2 with the corresponding gallery G1 , G2.

[0075] In this example, gallery 30 connects the first fluid chamber C1 of the actuator 502 with port V1 D of valve V1 . Similarly, gallery 32 connects the second fluid chamber C2 of the actuator 502 with port V3D of valve V3.

[0076] In this example, gallery G3 connects the outlet V2O of valve V2 and the outlet V4O of valve V4 to the inlet Fl of the filter F. That is, the gallery G3 is an outlet gallery for valves V2 and V4. Gallery G3 is a channel element, allowing passage of hydraulic fluid therethrough.

[0077] In this example, gallery G4 connects the outlet FO of the filter F to the inlet X1 1 of the valve X1 and the inlet X2I of the valve X2. That is, the gallery is an inlet gallery for valves X1 and X2. Gallery G4 is a channel element, allowing passage of hydraulic fluid therethrough.

[0078] The filter F filters debris and / or contaminants from the hydraulic fluid that passes through the filter F from inlet Fl to outlet FO. Any suitable filter may be used. For example the filter F may include pleated material and / or a mesh material to prevent passage of debris and / or contaminants. For example, the filter F may include pleated filter media sandwiched between a stainless steel mesh with a perforated aluminum inner tube and two end caps bonded with epoxy. In FIG. 3 the filter F is positioned on a fluid passage that connects the gallery G3 and the gallery G4. However, in other examples the inlet Fl of the filter F may be positioned on the gallery G3 and / or the outlet FO of the filter F may be positioned on the gallery G4.

[0079] In the schematic illustrated in FIG. 3 gallery G4 connects hydraulic accumulator A2 with inlet X1 1 of check valve X1 , inlet X2I of check valve X2 and the outlet FO of filter F. However, in other examples (for example FIG. 8) the hydraulic accumulator A2 may instead be connected to the outlet V2O of valve V2, the outlet V4O of valve V4 and the inlet Fl of filter F by gallery G3.

[0080] As can be seen from FIG. 3, the first hydraulic circuit 28 defined at least by gallery G1 and gallery 30 connect the first port PP1 of the hydraulic pump P to the first chamber C1 of the actuator 502. Where the first chamber C1 is an annulus chamber, the first hydraulic circuit 28 can be described as an annulus circuit.

[0081] Similarly, the second hydraulic circuit 29 defined at least by gallery G2 and gallery 32 connect the second port PP2 of the hydraulic pump P with the second chamber C2 of the actuator 502. Where the second chamber C2 is a piston chamber, the second hydraulic circuit 29 can be described as a piston circuit. The hydraulic circuits 28, 29 collectively define a compression circuit and a rebound circuit.

[0082] In operation, the control system 200 is configured to determine an appropriate setpoint indicative of required hydraulic pressure in one or both of the chambers C1 , C2 of the actuator 502. The setpoint obtained (received or calculated) by the control system 200 may be a pressure setpoint or an actuator force setpoint, for example.

[0083] In an example, the control system 200 may increase the setpoint for the second fluid chamber C2 of the actuator 502 when it is desired to cause an extension force to be generated by the actuator 502, for example to counter vehicle body roll in a particular direction. When it is determined that the actual pressure in second fluid chamber C2 of the actuator 502 is below the setpoint, then the pump P is operated so as to pump fluid from the first gallery G1 through the pump P into the second gallery G2. As the pressure in gallery G2 rises, hydraulic fluid may flow past check valve V3B causing the hydraulic pressure in gallery 32 and hence in the second fluid chamber C2 of the actuator 502 to also rise. Hydraulic pressure in hydraulic accumulator A3 will similarly rise. The pressure in gallery G2 relative to the setpoint is controlled by the valve V4 by restricting the flow back to the third gallery G3.

[0084] As the pressure in gallery G2 increases, so the pressure in gallery G1 may fall. Valves X2 and V4 will prevent or restrict fluid flow from gallery G2 to gallery G4 when the pressure in gallery G2 is greater than the pressure in gallery G4. As the pressure in gallery G1 drops, in particular to a pressure below the pressure in gallery G4 then check valve X1 will open, thereby equalising the pressure in galleries G1 , G3 and G4.

[0085] As the pressure in the second fluid chamber C2 of the actuator 502 increases, the piston 24 may rise (when viewing FIG. 3) causing hydraulic fluid to be expelled from the first fluid chamber C1 of the actuator 502. The expelled fluid will flow into gallery G1 dependent upon the flow characteristics of valve V1A, thus replacing some of the fluid lost from gallery G1 to gallery G2 via pump P. Fluid from hydraulic accumulator A1 may pass into gallery G1 .

[0086] After a period of time a steady equilibrium will be reached wherein the pressure in gallery G2, accumulator A3, gallery 32 and in the second fluid chamber C2 of the actuator 502 are all equal. The magnitude of this steady state pressure, equal to the setpoint, will determine the appropriate pump speed and setting of valve V4.

[0087] Consider the scenario where there is a disturbance input in the form of the wheel 12 hitting a bump. Whilst the target pressure in the second fluid chamber C2 of the actuator 502 is tending to extend the actuator 502, the bump in the road will cause the actuator 502 to contract thereby causing hydraulic fluid to flow out of the contracting second fluid chamber C2 of the actuator 502 and consequently into the expanding first fluid chamber C1 of the actuator 502. Fluid flow into the expanding first fluid chamber C1 is provided primarily by hydraulic fluid from accumulator A1 flowing through check valve V1 B. However, hydraulic fluid flowing out of the contracting second fluid chamber C2 of the actuator 502 is damped by valve V3A. Thus valve V3A acts as a damper valve underthese circumstances. Hydraulic fluid passing through valve V3A will primarily cause fluid to flow into accumulator A3. Once the bump has been negotiated the piston 24 will return to its steady state position. The bump will create a high frequency road induced input which is accommodated primarily by accumulator A3 which is close to the second fluid chamber C2 of the actuator 502 when compared with accumulator A2.

[0088] However, as a rate / magnitude of bump travel increases, movement of the piston 24 within the cylinder 22 may cause the pressure in chamber C2 of the actuator 502 and gallery G2 to increase above the valve pressure setting of valve V4 in which case the opening of the valve V4 will be momentarily increased so as to limit the pressure in gallery G2. Simultaneously, the large bump will cause the volume of chamber C1 of the actuator 502 to increase in size. Therefore, hydraulic fluid flows out of accumulator A1 into gallery G1 and on to gallery 30 via check valve V1 B. Hydraulic fluid also flows out of accumulator A2, through gallery G4, into gallery G1 via check valve X1 and on to gallery 30 via check valve V1 B.

[0089] If the disturbance input is in the opposite direction, such as a rebound, the fluid flow will be in the opposite direction. The rebound will cause the actuator 502 to extend thereby causing hydraulic fluid to flow out of the contracting first fluid chamber C1 of the actuator 502 and at the same time hydraulic fluid to flow into the expanding second fluid chamber C2 of the actuator 502. Fluid flow into the expanding second fluid chamber C2 is provided primarily by hydraulic fluid from accumulator A3 flowing through check valve V3B. However, hydraulic fluid flowing out of the contracting first fluid chamber C1 of the actuator 502 is damped by valve V1 A. Thus valve V1A acts as a damper valve underthese circumstances. Hydraulic fluid passing through valve V1A will primarily cause fluid to flow into accumulator A1 . Once the rebound has been negotiated the piston 24 will return to its steady state position. The rebound will create a high frequency road induced input which is accommodated primarily by accumulator A1 which is close to the first fluid chamber C1 of the actuator 502 when compared with accumulator A2. However, as a rate / magnitude of rebound travel increases, movement of the piston 24 within the cylinder 22 may cause the pressure in chamber C1 of the actuator 502 and gallery G1 to increase above the valve pressure setting of valve V2 in which case the opening of the valve V2 will be momentarily increased so as to limit the pressure in gallery G1 . Simultaneously, the large rebound will cause the volume of chamber C2 of the actuator 502 to increase in size. Therefore, hydraulic fluid flows out of accumulator A3 into gallery G2 and on to gallery 32 via check valve V3B. Hydraulic fluid also flows out of accumulator A2, through gallery G4, into gallery G2 via check valve X2 and on to gallery 32 via check valve V3B.

[0090] The volume of the second accumulator A2 may be greater than the volumes of accumulators A1 and A3. The volume of the second accumulator A2 may be greater than the full stroke differential volume of the actuator 502. The accumulator A2 may be a low pressure accumulator to compensate for system volume change when the actuator 502 strokes. The accumulators A1 and A3 may be high pressure accumulators (relatively).

[0091] Therefore, the first fluid chamber C1 of the actuator 502 can vent fluid to both hydraulic accumulators A1 and A2. The second fluid chamber C2 of the actuator 502 can vent fluid to both hydraulic accumulators A3 and A2. The hydraulic accumulators A1 and A3 are relatively close both physically and hydraulically to the fluid chambers C1 and C2 of the actuator 502, so these accumulators A1 , A3 can accommodate high frequency road induced inputs which tend to require relatively low amounts of hydraulic fluid to accommodate. If the control system’s setpoint is moving, the accumulators A1 and A3 may need to be filled more. Conversely the hydraulic accumulator A2, being larger, is better able to accommodate larger volumes of hydraulic fluid associated with larger relative movements of the piston 24 within the cylinder 22 often associated with low frequency driver induced inputs.

[0092] In this example, the valve V2 is a variable PCV and the valve pressure setting of valve V2 can be electronically varied to suit the particular circumstances. The valve V2 may comprise a variable restriction (variable orifice). Specifically, the valve pressure setting of valve V2 may be dependent upon the setpoint for the first chamber C1 of the actuator 502. The valve pressure setting of valve V2 may further be dependent upon the operating point of the pump P. The more electrical current is applied to the PCV V2, the more counteracting force restricts the flow. The PCV V2 needs continuous electrical current to counteract that pressure.

[0093] In this example, the valve V4 is a variable PCV and the valve pressure setting of valve V4 can be electronically varied to suit the particular circumstances. The valve V4 may comprise a variable restriction (variable orifice). Specifically, the valve pressure setting of valve V4 may be dependent upon the setpoint in the second chamber C2 of the actuator 502. The valve pressure setting of valve V4 may further be dependent upon the operating point of the pump P. The more electrical current is applied to the PCV V4, the more counteracting force restricts the flow. The PCV V4 needs continuous electrical current to counteract that pressure.

[0094] In steady state conditions, hydraulic fluid pumped in a first direction from the first port PP1 of pump P flows through the PCV V2, past the check valve X2, and back to the second port PP2 of the pump P. Hydraulic fluid pumped in the opposite direction from the second port PP2 of the pump P flows through the PCV V4, past the check valve X1 , and back to the first port PP1 of the pump P. The hydraulic pressure in each circuit 28, 29 is determined predominantly or entirely by the controllable pressure through the PCVs V2, V4.

[0095] Prior to operation, the hydraulic control apparatus 17 needs to be filled with hydraulic fluid. FIG. 3 illustrates fill ports FP1 and FP2, to enable filling with hydraulic fluid. Fill port FP1 is connected to the gallery G1 . Fill port FP1 is branched off the first hydraulic circuit 28. Fill port FP2 is connected to the gallery G2. Fill port FP2 is branched off the second hydraulic circuit 29. Two fill ports are shown because the hydraulic circuits 28, 29 are sealed from each other. The galleries G3 and G4 do not require a dedicated separate fill ports, because hydraulic fluid can flow into galleries G3 and G4 through the valves V2 and V4.

[0096] Before the filling, atmospheric air may be evacuated from the galleries G1 , G2, G3 and G4. It is desirable to minimise cycle time, defined as the time taken to evacuate the air and complete filling with hydraulic fluid. During a hydraulic fluid filling method, an interface 11 of a vacuum-and-fill machine M may be connected to a port such as fill port FP1 , and the machine M is controlled to generate a substantial vacuum in gallery G1 . The interface 11 may comprise a connector at the end of a hose connected to the machine M, for example. The machine M may be configured to both create a vacuum and to supply hydraulic fluid, through the interface 11 . Alternatively, separate vacuum machines and fill machines may be connected to separate ports. A similar interface I2 may be connected to another port such as fill port FP2, to generate a substantial vacuum in gallery G2. The interface I2 may comprise a connector at the end of a hose connected to a vacuum-and-fill machine, which may be the same machine M or a different one. Where the same machine M is used, a Y-split hose or separate hoses can connect the single machine M to both interfaces 11 , I2. Vacuum and fill operations are performed at both fill ports FP1 , FP2 simultaneously, to prevent small vacuum / fluid leakages from one gallery to the other through pump and valve clearances. Cycle time is also minimised.

[0097] By configuring the hydraulic control apparatus 17 with a separate outlet gallery for valves V2 and V4 and a separate inlet gallery for valves X1 and X2, when there is flow from gallery G1 to gallery G2 or from gallery G2 to gallery G1 the flow is uni-directional from gallery G3 to G4. That is, the only direct route between the outlets of V2 and V4 and the inlets ofX1 and X2 goes through both gallery G3 and gallery G4. The filter F is positioned such that hydraulic fluid flow from the gallery G3 to the gallery G4 passes through the filter F. As such, flow through the filter F is uni-directional. The uni-directional flow through the filter ensures filtered debris and / or contamination is not flushed back out of the filter as a F as a result of bi-directional flow.

[0098] The uni-directional flow through the filter F is irrespective of the hydraulic fluid flow through the system. Specifically, hydraulic fluid flow goes uni-directionally through the filter F irrespective of whether the flow is going from the gallery G2 to the gallery G1 (through the valve V4, through the filter F, through the valve X1) or from the gallery G1 to the gallery G2 (through the valve V2, through the filter F, through the valve X2).

[0099] By configuring the hydraulic control apparatus 17 such that there is uni-directional flow through the filter F, effective filtering is achieved without the use of additional check valves, which lead to additional system pressure drop, cost and weight. In some examples one or more seal elements may be provided to block any potential flow paths from the outlets of V2 and V4 and / orthe gallery G3 to the inlets of X1 and X2 and / orthe gallery G4, for example around V2 and V4. In some examples one or more seal elements may be provided to block any potential flow paths around the filter F from the gallery G3 to the gallery G4.

[0100] FIGS. 4 to 9 illustrate example embodiments, implementing the schematic of FIG. 3.

[0101] FIG. 4 illustrates an example actuator system 161 and hydraulic control apparatus 171. The hydraulic control apparatus 171 may be used as the hydraulic control apparatus 17 for the actuator system 16 of FIG. 3. In the apparatus 171 , the valves V2, V4, X1 and X2 are each separate components mounted within a housing 191. The filter F is positioned on gallery G3 between valves V2, V4. The hydraulic fluid flow from either V2 or V4 enters the filter F directly from gallery G3.

[0102] In this example V2 and V4 each include a seal element 301 , 302 to help prevent hydraulic fluid flow from galleries G1 and G2, respectively, leaking into gallery G3. In this example the filter F includes a seal element 309 to prevent leakage from gallery G3 to G4 around the filter F. Any suitable seal element, for example an O- ring, may be used for each of seal elements 301 , 302, 309.

[0103] As an example, FIG. 5 illustrates the hydraulic control apparatus 171 in use with the pump pumping fluid from gallery G2 to gallery G1 . It would be understood that the specific relative pressures and valve settings that drive the hydraulic flow in the manner shown may be the same as those described above for FIG. 3. The arrows on each gallery or fluid passage indicate the direction of flow. In this example, hydraulic fluid passes from gallery G1 through V2, which is at least partially open. The hydraulic fluid enters gallery G3 from V2 and then flows to gallery G4 through filter F. V4 remains closed. Hydraulic fluid is otherwise prevented from flowing from gallery G3 to gallery G4 by seal element 309. From filter F, the hydraulic fluid passes through valve X2 into gallery G2.

[0104] FIG. 6 illustrates another example actuator system 162 and hydraulic control apparatus 172. The hydraulic control apparatus 172 may be used as the hydraulic control apparatus 17 for the actuator system 16 of FIG. 3. In the apparatus 172, the valves V2, V4, X1 and X2 are each provided in a housing 192. The valves V2 and X1 are integral within sleeve member 195. The valves V4 and X2 are integral within sleeve member 196. The filter F is positioned between gallery G3 and gallery G4.

[0105] In this example, access to valve V2 from gallery G1 is provided through a central bore 305 of valve X1 . The central bore 305 passes through closing member 306 even when the closing member 306 is in the closed position. For the avoidance of doubt, X1 is shown in the closed position and X2 is shown in the open position in FIG. 6. In the same manner, access to valve V4 from gallery G2 is provided through a central bore of valve X2 (for image clarity the central bore and closing member of X2 are not labelled). In this example sleeve member 195 includes a seal element 303 positioned between V2 and X1. Sleeve member 196 includes a seal element 304 positioned between V4 and X2. Seal elements 303, 304 prevent hydraulic fluid flow from gallery G3 to gallery G4 around V2 or V4.

[0106] As an example, FIG. 7 illustrates the hydraulic control apparatus 172 in use with the pump pumping fluid from gallery G2 to gallery G1. It would be understood that the relative pressures and valve settings that drive the hydraulic flow in the manner shown may be the same as those described above for FIG. 3. The arrows on each gallery or fluid passage indicate the direction of flow.

[0107] In this example, hydraulic fluid passes from gallery G1 through V2, which is at least partially open. Access to V2 from G1 is provided via the central bore in X1 . The hydraulic fluid enters gallery G3 from V2. Hydraulic flow along G3 passes across V4 (which remains closed) and then flows to gallery G4 through filter F. The hydraulic fluid passes through valve X2 into gallery G2.

[0108] FIG. 8 shows another example actuator system 173. This example largely corresponds to the example actuator system 172. However, in this example the filter F is positioned between the sleeve assemblies 195, 196. As an example, FIG. 9 illustrates the hydraulic control apparatus 173 in use with the pump pumping fluid from gallery G1 to gallery G2. In this example, hydraulic fluid passes from gallery G2 through V4, which is at least partially open. Access to V4 from G2 is provided via the central bore in X2. The hydraulic fluid enters gallery G3 from V4. Hydraulic fluid flow passes from G3 to G4 through filter, with V2 remaining closed. The hydraulic fluid passes through valve X1 into gallery G1 .

[0109] With reference to FIG. 11 , there is illustrated an example implementation of a control system 200 for a vehicle 1 . The control system 200 comprises one or more controllers 201 .

[0110] The control system 200 is configured to receive sensor data from any appropriate sensors such as one or more of the sensors 514, 516, 522 (FIG. 2), and determine the setpoint indicative of required hydraulic pressure, in dependence on the sensor data. The control system 200 may then output a control signal to control the active suspension system 104. For example, control signals may be output to one or more of: the pump P; the valve V2; or the valve V4, of at least one hydraulic control apparatus 17.

[0111] The control system 200 as illustrated in FIG. 11 comprises one controller 201 , although it will be appreciated that this is merely illustrative. The controller 201 comprises processing means 204 and memory means 206. The processing means 204 may be one or more electronic processing devices 204 which operably execute computer-readable instructions. The memory means 206 may be one or more memory devices 206. The memory means 206 is electrically coupled to the processing means 204. The memory means 206 is configured to store instructions, and the processing means 204 is configured to access the memory means 206 and execute the instructions stored thereon.

[0112] The controller 201 comprises an input means 210 and an output means 212. The input means 210 may comprise an electrical input 210 of the controller 201 . The output means 212 may comprise an electrical output 212 of the controller 201 . The controller 201 may have an interface 202 comprising an electrical input / output I / O 210, 212, or an electrical input 210, or an electrical output 212, for receiving information and interacting with external components. The input 210 is arranged to receive the sensor data. The sensor data is an electrical signal which is indicative of a measurand sensed by the relevant sensor. The output 212 is arranged to output suspension control signals, indicative of a setpoint for controlling the hydraulic control apparatus 17.

[0113] FIG. 12 illustrates a non-transitory computer-readable storage medium 300 comprising the instructions (computer software).

[0114] It is to be understood that the or each controller 201 can comprise a control unit or computational device having one or more electronic processors (e.g., a microprocessor, a microcontroller, an application specific integrated circuit (ASIC), etc.), and may comprise a single control unit or computational device, or alternatively different functions of the or each controller 201 may be embodied in, or hosted in, different control units or computational devices. As used herein, the term “controller,” “control unit,” or “computational device” will be understood to include a single controller, control unit, or computational device, and a plurality of controllers, control units, or computational devices collectively operating to provide the required control functionality. A set of instructions could be provided which, when executed, cause the controller 201 to implement the control techniques described herein (including some or all of the functionality required for the method(s) described herein). The set of instructions 208 could be embedded in said one or more electronic processors 204 of the controller 201 ; or alternatively, the set of instructions 208 could be provided as software to be executed in the controller 201 . A first controller or control unit may be implemented in software run on one or more processors. One or more other controllers or control units may be implemented in software run on one or more processors, optionally the same one or more processors as the first controller or control unit. Other arrangements are also useful.

[0115] The, or each, electronic processor 204 may comprise any suitable electronic processor (e.g., a microprocessor, a microcontroller, an ASIC, etc.) that is configured to execute electronic instructions 208. The, or each, electronic memory device 206 may comprise any suitable memory device and may store a variety of data, information, threshold value(s), lookup tables or other data structures, and / or instructions therein or thereon. In an embodiment, the memory device 206 has information and instructions for software, firmware, programs, algorithms, scripts, applications, etc. stored therein or thereon that may govern all or part of the methodology described herein. The processor, or each, electronic processor 204 may access the memory device 206 and execute and / or use that or those instructions and information to carry out or perform some or all of the functionality and methodology described herein.

[0116] The at least one memory device 206 may comprise a computer-readable storage medium (e.g. a non-transitory or non-transient storage medium) that may comprise any mechanism for storing information in a form readable by a machine or electronic processors / computational devices. Examples of the form include, without limitation: a magnetic storage medium (e.g. floppy diskette); optical storage medium (e.g. CD-ROM); magneto optical storage medium; read only memory (ROM); random access memory (RAM); erasable programmable memory (e.g. EPROM ad EEPROM); flash memory; or electrical or other types of medium for storing such information / instructions. It will be appreciated that embodiments of the present invention can be realised in any suitable form of hardware, software or a combination of hardware and software. For example, it is contemplated that the present invention is not limited to being implemented by way of programmable processing devices, and that at least some of, and in some embodiments all of, the functionality and or method steps of the present invention may equally be implemented by way of non-programmable hardware, such as by way of non-programmable ASIC, Boolean logic circuitry, etc.

[0117] It will be appreciated that various changes and modifications can be made to the present invention without departing from the scope of the present application.

Claims

CLAIMS1 . A hydraulic control apparatus for a piston actuator of an active suspension system of a vehicle, the hydraulic control apparatus comprising: a first hydraulic gallery hydraulically couplable to a first fluid chamber of the piston actuator; a second hydraulic gallery hydraulically couplable to a second fluid chamber of the piston actuator; a third hydraulic gallery connected to the first and second hydraulic galleries; a fourth hydraulic gallery connected to the first, second and third hydraulic galleries; a first valve connecting the fourth hydraulic gallery to the first hydraulic gallery, wherein the first valve is biased towards a closed position and arranged to permit flow of hydraulic fluid from the fourth hydraulic gallery to the first hydraulic gallery when open; a second valve connecting the second hydraulic gallery to the third hydraulic gallery, wherein the second valve is arranged to permit one-way hydraulic fluid flow from the second hydraulic gallery to the third hydraulic gallery, and wherein the second valve is controllable to control a pressure across the second valve; and a filter positioned such that hydraulic fluid flow from the third hydraulic gallery to the fourth hydraulic gallery passes through the filter.

2. The hydraulic control apparatus of any preceding claim, comprising: a third valve connecting the fourth hydraulic gallery to the second hydraulic gallery, wherein the third valve is biased towards a closed position and arranged to permit flow of hydraulic fluid from the fourth hydraulic gallery to the second hydraulic gallery when open; and a fourth valve connecting the first hydraulic gallery to the third hydraulic gallery, wherein the fourth valve is arranged to permit one-way hydraulic fluid flow from the first hydraulic gallery to the third hydraulic gallery, and wherein the fourth valve is controllable to control a pressure across the fourth valve.

3. The hydraulic control apparatus of claim 2, wherein the hydraulic control apparatus comprises one or more seal elements configured to prevent hydraulic fluid flow from an outlet of the second valve and / or the third hydraulic gallery to an inlet of the third valve and / or the fourth hydraulic gallery.

4. The hydraulic control apparatus of claim 2 or 3, wherein the hydraulic control apparatus comprises one or more seal elements configured to prevent hydraulic fluid flow from an outlet of the fourth valve and / or the third hydraulic gallery to an inlet of the first valve and / or the fourth hydraulic gallery.

5. The hydraulic control apparatus of any of claims 2 to 4, wherein the second valve and the third valve are integral within a sleeve member.

6. The hydraulic control apparatus of any of claims 2 to 5, wherein the first valve and the fourth valve are integral within a sleeve member.

7. The hydraulic control apparatus of any preceding claim, wherein the filter comprises one or more seal elements configured to prevent hydraulic fluid flow around the filter from the third hydraulic gallery to the fourth hydraulic gallery.

8. The hydraulic control apparatus of any preceding claim, wherein the third hydraulic gallery or fourth hydraulic gallery comprises a hydraulic accumulator.

9. The hydraulic control apparatus of any preceding claim, comprising a pump operable to control flow rate and / or pressure in the first hydraulic gallery and second hydraulic gallery.

10. The hydraulic control apparatus of any preceding claim, wherein each of the third hydraulic gallery and the fourth hydraulic gallery is a channel element.

11. An active suspension system comprising: the hydraulic control apparatus of any one of the preceding claims; and the piston actuator.

12. A vehicle comprising the active suspension system of claim 11.

13. The vehicle of claim 12, comprising one of said active suspension system for each of a plurality of wheels of the vehicle.

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