An electrohydraulic unit for a vehicle

Abstract

An electrohydraulic unit for a vehicle having housing 2 with two ports 8, 9, pump 3 (e.g. radial piston pump) providing to and extracting fluid from the two ports, and two valves 4, 5 controlling flui

Description

Field of the Disclosure The present disclosure concerns electrohydraulic units for vehicles. More particularly, but not exclusively, the present disclosure concerns an electrohydraulic unit for a vehicle, an electrohydraulic system comprising such a unit, vehicles comprising such systems or units, and methods of operating such units. Background of the Disclosure The control of automotive vehicle systems has evolved significantly over the years, broadly transitioning from purely mechanical systems to electromechanical systems. Electromechanical systems integrate electric actuators, motors, and electronic control units to manage various vehicle systems, such as steering, braking, and suspension. Despite their widespread adoption, electromechanical systems present several disadvantages. First, the complexity of their design often leads to increased production costs and challenges in maintenance. Additionally, the power demands of electromechanical actuators can strain vehicle electrical systems, particularly in battery-electric vehicles where energy efficiency is critical. Furthermore, electromechanical systems may face limitations in providing sufficient force or responsiveness for certain heavy-duty or high-performance applications. For example, in braking or steering systems subjected to high loads, purely electromechanical solutions may struggle to deliver the necessary performance without significant increases in component size and power consumption. Electrohydraulic systems, which combine hydraulic actuation with electronic control, may be used to manage individual vehicle systems requiring higher force output, such as power steering or active suspension. Furthermore, electrohydraulic systems may provide a smaller footprint with lower power consumption. While electrohydraulic systems can address some limitations of electromechanical systems by leveraging the high power density of hydraulics, they are typically confined to specific applications rather than serving as a comprehensive vehicle control solution. In prior art systems, each hydraulic valve is controlled by a different electric motor. The operation of different valves is then synchronized by a control system that controls the operation of the various motors. This may limit the speed at which the valve can switch between different configurations, and can result in a large, mechanically complex system. The present disclosure seeks to mitigate the above-mentioned problems. Alternatively or additionally, the present disclosure seeks to provide an electrohydraulic unit and methods of operation thereof. Summary of the Disclosure In a first aspect, the present disclosure may provide an electrohydraulic unit for a vehicle. The electrohydraulic unit may comprise a housing. The housing may comprise a first P-port and / or a second P-port. The electrohydraulic unit may comprise a pump configured to provide fluid to and extract fluid from a first P-port and a second P-port. The electrohydraulic unit may comprise a first valve located between the pump and the first P-port, and a second valve located between the pump and the second P-port, each valve configured to control fluid flow between the pump and each respective P-port. The electrohydraulic unit may comprise a first pressure sensor configured to provide indication of a first pressure at the first P-port, and a second pressure sensor configured to provide indication of a second pressure at the second P-port. The electrohydraulic unit may comprise a controller. The controller may be configured to receive status signals indicating the first and second pressures. The control may be configured to receive status signals indicating current operation parameters of the pump, the first valve and / or the second valve. The controller may be configured to receive a control signal indicating a target pressure at the first P-port and / or the second P-port. The controller may be configured to determine target operation parameters of the pump, the first valve and / or the second valve. The controller may be configured to determine said target operation parameters based on the status signals and the control signal. The controller may be configured to control one or more of pump, the first valve and the second valve based on the target operation parameters. One or more of the pump, the first and second valves, the first and second pressure sensors and the controller may be located within the housing. Such an electrohydraulic unit may provide an efficient means of controlling multiple systems of a vehicle. Use of a single pump to control fluid flow to and from multiple P-ports may provide a compact and efficient unit and / or improve the control of pressure in the unit. Persistent or periodic feedback between the multiple components of the electrohydraulic unit may facilitate a high level of control of fluid pressure at the P-ports, which may lead to a more responsive electrohydraulic unit. Hereafter, the terms ‘electrohydraulic unit’ and ‘unit’ may be used interchangeably for brevity. It may be that the unit is self-contained. The unit may be suitable for connection to external systems and / or components. The unit may form the basis for a modular electrohydraulic system, the electrohydraulic system being formed by at least one electrohydraulic unit connected to at least two actuators via the P-ports. The housing of the unit may be an enclosure configured to encase the various components of the unit. The housing may comprise an external surface including the first and second P-ports. The first and second P-ports, and any further P-ports, may be orifices in an external surface of the housing. It may be that the housing comprises an interior cavity for accommodating the pump, valves, pressure sensors, controller and any further components comprised by the housing. It may be that the housing is formed from a single component, or several separate components combined to form a unified external surface. It may be that fluid flows into and out of the electrohydraulic unit via only the P-ports. It may be that the housing comprises more than two P-ports, for example at least three, at least four, at least five or more than five P-ports. It may be that the pump comprises a rotor assembly and a pump motor. It may be that the pump is bidirectional as regards the flow of fluid through the pump. In this way, the pump may both provide fluid to, and extract fluid from, an external system connected to each P-port. It may be that the fluid is a liquid and / or a gas. It may be that each P-port permits flow in both directions (i.e. a P-port is a two-way or bidirectional port). Each P-port may be an orifice. For example, each P-port may be an orifice in a surface of the housing. Each P-port may comprise and / or be configured to receive a connector. The electrohydraulic unit may comprise connectors configured to connect the unit to an external system, each connector being received in each P-port and / or being integrally formed with a housing defining each P-port. Each connector may comprise a screw thread and / or a tapered region for interlocking with a corresponding connector on the external system. The connector may be a male or female connector. The connector may comprise a protuberance, for example extending around the longitudinal axis of the connector and being configured to form a seal with a corresponding connector. It may be that the first valve and / or the second valve comprises a spool mounted for movement with respect to a sleeve. It may be that the position of the spool relative to the sleeve determines the fluid flow to or from one or both P-ports. It may be that the first valve and / or the second valve is a servo valve. The or each servo valve may comprise a spool mounted for movement with respect to a sleeve. The or each servo valve may be configured such that movement of the spool relative to the sleeve controls the flow of fluid through the valve. For example, one or more inlet ports and one or more outlet ports may be formed in the sleeve and movement of the spool may determine the flow paths between said ports. It may be that the spool has one or more lands or grooves formed therein, and, in use, fluid flows between the inlet and outlet ports via said lands or grooves. The or each servo valve may be configured such that the position of the spool determines the fluid flow to or from one or both P-ports. The or each servo valve may be a multi-way (for example, a two-way) servo valve. A single servo valve may comprise both the first and second valves, and any further valves. For example, the servo valve may be a six-way servo valve. The or each servo valve may be configured to control the flow of fluid to or from the first P-port independently of the flow to from the second, or any other P-port. Use of a single servo valve may provide for a more compact and / or mechanically electrohydraulic unit. Additionally or alternatively, use of a servo valve may provide a more responsive suspension unit as a servo valve allows for rapid switching between configurations. Additionally or alternatively, use of such a valve may increase the power efficiency of the unit as only a small amount of power is required to move the valve between different states. The sleeve of the servo valve may be integrally formed with a manifold or housing of the electrohydraulic unit. The sleeve of the servo valve may be formed using an additive manufacturing technique. The or each servo valve may be a rotary servo valve in which the spool is mounted for rotation relative to the sleeve. The or each servo valve may be a linear servo valve in which the spool is mounted for axial displacement relative to the sleeve. The or each servo valve may be a direct drive valve. Thus, the or each servo valve may comprise a motor configured to move the spool relative to the sleeve. Use of a direct drive valve (i.e. a valve where the spool is directly driven by an actuator) may allow yet further miniaturisation of the unit, and may allow for precise switching between operational states, at high frequency and with quick response time. It may be that the first valve is the only component situated in a first flow path between the pump and the first P-port. It may be that the second valve is the only component situated in a second flow path between the pump and the second P-port. A valve may have an open configuration in which fluid is able to flow through the valve along a flow path, and another open configuration in which fluid is able to flow through the valve along the same flow path but in which the valve provides an increased resistance to flow in comparison with the other open configuration. A valve may have further open configurations in which fluid is able to flow through the valve along the same flow path but in which the valve provides an altered resistance to flow in comparison with the first open configuration. A valve may have a discrete number of different open configurations providing different flow resistance. Alternatively, a valve may have a continuum of open configurations with the flow resistance varying across said range. A valve may be a proportional valve. A valve may have an open configuration, in which fluid is able to flow through the valve along a flow path and another open configuration in which fluid is able to flow through the valve along a different flow path. A valve may have further open configurations, in which fluid is able to flow through the valve along further, different, flow paths. Thus, a valve may be a multiway valve, for example a three or four-way valve. A valve may have a closed configuration. A closed configuration may be defined as a configuration in which the flow of fluid through the valve is prevented. It will be appreciated that in some valves, the intended flow paths through the valve are closed off in a closed configuration, but there will nevertheless be some leakage. For example, when a spool valve is in a closed configuration the flow paths between the ports via the spool are closed off, but there will be some quiescent leakage around the spool. It may be that the closed configuration is a shut-off configuration, being a closed configuration in which there is no leakage through the valve in either direction of flow. Thus, a valve may be a shutoff valve. A shutoff valve may be a valve with an open configuration and a closed configuration, with no intermediate configuration therebetween. A shutoff valve may be configured to provide a binary control of fluid flow. A shutoff valve may be configured to prevent fluid flow from the pump to a P-port, and from a P-port to the pump. As used herein, the term “sensor” refers to both sensors and transducers. It may be that a pressure sensor comprises a pressure sensing element for detecting a change in pressure and a sensor mechanism for converting that pressure change to an electrical signal. It may be that each pressure sensor is connected, for example via a wired and / or wireless connection, to the controller. It may be that the controller is a device configured to execute tasks and manage operations based on instructions provided by software. It may be that the controller is connected, for example via wired and / or wireless connections, to the components of the electrohydraulic unit. It may be that the controller comprises a processor, memory, input / output interfaces and / or communication interfaces. In this way, the controller may communicate with components within the electrohydraulic unit and systems and / or a user external to the electrohydraulic unit. It may be that the control signal is received by the controller from an external system. For example, the control signal may be the result of a user input, a vehicle input and / or in response to a user action (e.g. braking, steering etc.). Preferably, the electrohydraulic unit has a response time of less than 50 ms, for example less than 10 ms, and even more preferably a response lime of less than 5 ms. A response time may be defined as the time needed between the controller initiating a change in the operation parameters of a component of the electrohydraulic unit and the change being achieved. It may be that the controller comprises a feedback-based control loop mechanism. It may be that the controller comprises a proportional-integral-derivative (PID) mechanism. A PID system may be based on three factors: proportional, integral, and derivative terms. The proportional term reacts to the current error, the difference between the desired and actual output. The integral term accumulates past errors to address long-term deviations, and the derivative term predicts future errors by assessing the rate of change. Together, these terms may enable precise and dynamic control of the fluid pressure. The controller may periodically or continually compare the target pressures with the current pressures, and apply corrective operation parameters (i.e. vary the operation parameters) to resolve them (i.e. reduce any difference between the target pressure and the current pressures). It may be that the second valve differs from the first valve. It may be that the second valve differs from the first valve in respect to the type and / or construction of the valve. It may be that the second valve is of a different construction to the first valve. It may be that the second valve is of a different type to the first valve. By way of example only, valves of the same type (e.g. servo valves, poppet valves) may have different construction (e.g. a different sleeve, valve member, ports and / or a different arrangement of any of the foregoing). It may be that the first and / or second valve differs (in construction and / or type) from any further hydraulic valve. It may be that the first, second and / or any further hydraulic valve is a spool valve or a poppet valve. It may be that only one or neither of the first and second valves is a shutoff valve. A shutoff valve is a valve that can provide a shutoff configuration. Thus, the electrohydraulic unit may provide a binary level of control to one P-port (for example: on or off) and a proportional level of control to another P-port (for example over a range of pressures). It may be that the operation parameters include at least one of: a speed of the pump; a direction of the pump; a position of the first valve; and a position of the second valve. Thus, the electrohydraulic unit may adapt to the requirements of external systems. In this way, the pressure at the P-ports may be controlled in an efficient manner. It may be that the controller determines a particular combination of operation parameters for a particular combination of target pressures at the first P-port and the second P-port. It may be that a target pressure is obtained via a combination of at least two operation parameters. It may be that a target pressure is obtained by a particular sequence of operation parameters. It may be that the controller is configured to receive a mode signal indicating a mode of operation of the unit. The controller may be configured to determine operation parameters in dependence on the mode of operation. The mode signal may indicate various different modes, for example a low power mode and a high-speed mode. The mode signal may be provided by an external system and / or a user input. It may be that in the low power mode the controller prioritises efficiency over speed. For example, in the low-power mode the controller may be configured to minimise a speed of the pump while delivering target pressure, which may result in a higher latency between current and target pressures. It may be that in the high-speed mode the controller prioritises speed over efficiency. For example, in the high-speed mode the controller may be configured to minimise the latency between current and target pressures. When the control signal indicates high target pressure at both ports, the controller may be configured to determine operation parameters comprising a high pump speed and open first and second valves. When the control signal indicates a moderate target pressure at the first P-port and a low target pressure at the second P-port, the controller may be configured to determine operation parameters comprising a moderate pump speed, an open first valve and a restricted second valve. The operation parameters may further include at least one of: a speed of the first valve; and a speed of the second valve. It may be that the electrohydraulic unit further comprises a temperature sensor. The temperature sensor may be configured to provide indication of a temperature of fluid within the unit. It may be that the status signals further indicate the temperature. It may be that the temperature sensor is connected, for example via a wired and / or wireless connection, to the controller. In this way, the controller may be configured to control various components of the electrohydraulic unit in accordance with the temperature of the fluid. It may be that the controller is configured to adapt the determination of target operation parameters based on the temperature. It may be that the determination of operation parameters is dependent on the temperature. For example, variations in fluid temperature may cause associated variations in pressure, which the controller may account for to maintain a high level of control of the pressure at the first and second P-ports. It may be that the electrohydraulic unit further comprises at least one accumulator. It may be that the or each accumulator is connected to the first and / or second valve. It may be that the or each accumulator is configured to supply pressurised fluid to the first and / or second P-port. It may be that the or each accumulator is configured to supply pressurised fluid via the first and / or second valve. It may be that the or each accumulator is associated with an accumulator valve. It may be that the or each accumulator valve is configured to control fluid flow between the or each accumulator and the first P-port and / or the second P-port. It may be that the or each accumulator is located within the housing. It may be that the or each accumulator is a gas accumulator. A gas accumulator may comprise a gas reservoir (for containing a compressible gas) and a fluid reservoir (for containing an incompressible fluid). The gas and fluid reservoirs may be separated by a barrier such that pressure can be transmitted between the gas and fluid reservoirs. In use, the gas reservoir may contain a compressible gas. In use, the fluid reservoir may contain incompressible fluid as used in the common flow path and rest of the hydraulic unit. The or each accumulator may comprise at least one air fill valve configured for connection to a supply of compressible gas. It may be that an accumulator allows for a smaller pump to be used in the electrohydraulic unit, as pressurised fluid may be built up in at least one accumulator over time, rather than being provided instantaneously. Additionally or alternatively, this may lead to a more efficient electrohydraulic unit by avoiding peaks and troughs in the power required from the pump. It may be that the electrohydraulic unit comprises a plurality of accumulators. Using accumulator(s) may allow this to be achieved in a space efficient and mechanically simply way. It may be that the operation parameters include a status and / or charge of the at least one accumulator. It may be that the status signals further indicate a status and / or charge of the at least one accumulator. It may be that a status and / or charge of the at least one accumulator comprises an internal pressure, for example an internal gas pressure, of the at least one accumulator. It may be that the pump is a radial piston pump. It may be that the pump comprises a pintle. It may be that the pump comprises a rotor mounted for rotation on the pintle, the rotor comprising a plurality of piston chambers, a piston being mounted in each chamber for reciprocal movement. It may be that the pump is configured such that rotation of the rotor in a first direction causes fluid to flow from the piston chambers toward a P-port, and rotation of the rotor in a second, opposite, direction causes fluid to flow from a P-port toward the piston chambers. Thus, a radial piston pump may be bidirectional as regards the flow of fluid through the piston chambers. In this way, the pump may both provide fluid to, and extract fluid from, an external system connected to each P-port. This may reduce the need for separate controllers and / or motors for controlling fluid flow in external systems. Alternatively or additionally, this may improve the control of pressure in the electrohydraulic unit. Additionally, or alternatively, flow in both directions between the piston chambers and the P-ports may be controlled using a single valve. It may be that flow in both directions between the piston chambers and the P-ports is controlled using a separate valve associated with each P-port. This may allow for a compact electrohydraulic unit. Alternatively or additionally, external components (for example actuators or vehicle systems) connected to the electrohydraulic unit may not require their own controller or valves. In this way, the electrohydraulic unit may provide a means of controlling multiple systems of a vehicle in a compact, efficient manner. The pump may comprise a pump motor configured to rotate the rotor relative to the pintle. The pump motor may comprise a plurality of magnets, a plurality of coils and a stator. It may be that the rotor comprising the plurality of piston chambers is mounted for rotation with respect to the stator. It may be that either the plurality of magnets or the plurality of coils is mounted on the stator and the other of the plurality of magnets and the plurality of coils is mounted on the rotor. Thus, electrohydraulic units in accordance with the present disclosure may comprise a common rotor as between the pump and the pump motor. It may be advantageous to mount the magnets on the rotor, as the coils can thereby be located in a dry area of the pump unit. Use of such a common rotor may allow for a more compact pump for a given flow rate and / or reduce the mechanical complexity of the pump with respect to similar prior art pumps. It will be appreciated that the plurality of magnets or the plurality of coils are mounted on the rotor for rotation therewith, such that when a current is provided to the coils in the presence of the magnetic field of the magnets and electromotive force is generated thereby rotating the rotor. Electric motors per se are well known and will not be described further here. Further detail is provided in WO 2022 / 234284 (Dornin Fluid Power Limited) the contents of which is incorporated herein by reference. It may be that the pump comprises a manifold. It may be that the manifold is of a single-piece construction, for example produced using additive manufacturing. It may be that the manifold comprises (e.g. an internal surface of the manifold defines) P flow-galleries leading to the P-ports. It may be that the manifold, e.g. a surface of the manifold, defines the pintle. The pump may comprise a servo valve comprising a spool mounted for movement relative to one or more ports, for example ports formed in an internal surface (for example an internal surface of the manifold) defining a cavity in which the spool is received. Thus, movement of the spool relative to the ports may be used to control the flow of fluid through the manifold and / or to or from an external hydraulic system. It may be that the spool has one or more lands or grooves formed therein, and, in use, fluid flows between the ports via said lands or grooves. It may be that the first valve and / or the second valve is a proportional valve. A proportional valve may be defined as a valve that can occupy more than one open position, such that the non-zero flow rate of fluid through the valve can be varied. It will be understood that the pressure drop or loss across such a valve corresponds to a dissipation of hydraulic power and accordingly such valves can dissipate the oscillations of an actuator connected thereto. The proportional valve may be a variable orifice valve. It may be that the electrohydraulic unit further comprises a reservoir connected to the pump such that, in use, fluid can flow between the reservoir and the pump. It may be that the reservoir is situated within the housing of the electrohydraulic unit, as an internal reservoir. Alternatively or additionally, the electrohydraulic unit may be connected to a reservoir external to the housing of the unit, for example a power steering reservoir of a vehicle. It may be that the electrohydraulic unit comprises one or more sensors. It may be that the or each sensor is configured to provide indication of a parameter of the operation of the unit. According to a second aspect of the disclosure, there is provided an electrohydraulic system comprising the electrohydraulic unit of the first aspect. It may be that the electrohydraulic system comprises first and second actuators connected to the first and second P-ports respectively. It may be that each actuator is arranged to move using energy provided in the form of hydraulic pressure at the P-ports. Thus, an electrohydraulic system may be defined herein as a system comprising an electrohydraulic unit and two or more actuators. An actuator may be able to apply a force in a first direction and / or a second, opposite, direction. An actuator may be able to increase and / or decrease in length. It may be that an actuator is a linear actuator, rotary actuator or a hydraulic motor. It may be that each actuator is arranged to move using energy provided in the form of hydraulic pressure from the pump and / or from one or more accumulators. It may be that the electrohydraulic system comprises one or more sensors. It may be that the or each sensor is configured to provide indication of a parameter of the operation of an actuator, e.g. a position, velocity, acceleration etc. of the actuator. It may be that the electrohydraulic system further comprises a position sensor. It may be that the position sensor is configured to provide indication of a position of the first actuator or the second actuator. It may be that the status signals further indicate the position of the first actuator or the second actuator. A linear actuator may have an extended configuration and a retracted configuration. It may be that a linear actuator has a range of positions between the extended and retracted configurations. It may be that the position of an actuator is a measure of its extension / retraction. A rotary actuator may have a radial position relative to a fixed axis. It may be that the position of an actuator is a measure of its radial position. It may be that the position sensor is connected, for example via a wired and / or wireless connection, to the controller. In this way, the controller may provide a more sophisticated level of control of an actuator. It may be that the controller is configured to determine the operation parameters in dependence on the position of the first actuator and / or the second actuator. It may be that the electrohydraulic unit and / or system further comprises an accelerometer. It may be that the accelerometer is configured to provide indication of an acceleration of the first actuator or the second actuator. It may be that the accelerometer is configured to provide indication of an acceleration of the electrohydraulic unit and / or system. It may be that the status signals further indicate the acceleration of the first actuator or the second actuator. It may be that the accelerometer is connected, for example via a wired and / or wireless connection, to the controller. It may be that the controller is configured to determine the operation parameters in dependence on the acceleration of the first actuator and / or the second actuator. It may be that at least one of the first and second actuators forms part of one of the following vehicle systems: suspension, brakes, steering, toe adjust, aerodynamics, and camber. For example, an actuator may be a suspension actuator arranged to control relative motion of a vehicle wheel and chassis in response to road conditions. An actuator may be a brake actuator configured to move a brake pad of a vehicle from a first position to a second position in order to effect braking of a wheel of the vehicle. An actuator may be a steering actuator configured to move one or more wheels of a vehicle. An actuator may be a toe adjust actuator configured to control the alignment of a vehicle’s wheels relative to a centreline of the vehicle. An actuator may be an aerodynamics actuator configured to move an aerodynamic component of a vehicle, such as a spoiler, wing, diffuser, or air intake. An actuator may be a camber actuator configured to control the tilt of one or more wheels of a vehicle. It may be that the electrohydraulic unit is coupled with one or more actuators of an automotive system, for example an actuator of a suspension system. Other contemplated systems include a brake system, a steering system, a toe adjust system, an aerodynamic system, and a camber system. In this way, the or each electrohydraulic system may be easily integrated within a vehicle, as it may occupy a comparable volume to the conventional mechanical system it replaces. Alternatively or additionally, this may avoid the requirement for a central controller / system for communicating with each electrohydraulic unit. This may allow for a compact and / or efficient means of vehicle control. It may be that the electrohydraulic system further comprises a third actuator connected to the first P-port. It may be that the third actuator is arranged to move using energy provided in the form of hydraulic pressure at the first P-port. In this way, the first valve may be able to control both the first and third actuators. This may provide for an efficient and / or compact means of control. Alternatively or additionally, the first and third actuators may be controlled simultaneously and / or dependently on one another. It may be that the first actuator is arranged to control a camber of one or more wheels of a vehicle, and the third actuator is arranged to control an aerodynamic profile of a vehicle. It may be that camber and aerodynamic profile are complementary vehicle systems. Thus, camber and aerodynamic profile may be particularly suited to being controlled by a single valve. Thus, such a system may provide a compact and / or efficient means of vehicle control. According to a third aspect of the disclosure, there is provided a vehicle comprising the electrohydraulic unit of the first aspect and / or the electrohydraulic system of the second aspect. The vehicle may have any of the features described above, or vice versa. It may be that the vehicle comprises a plurality of units according to the first aspect. It may be that the vehicle comprises a plurality of systems according to the second aspect. For example, the vehicle may comprise four electrohydraulic units and / or systems. It may be that each electrohydraulic unit / system is arranged on a corner of the vehicle. In this way, the vehicle may not require a vehicle-wide hydraulic system. Each electrohydraulic unit / system may be configured to control systems and / or actuators adjacent to each respective corner of the vehicle, thereby avoiding the need to pump hydraulic fluid around the majority of the vehicle. This may provide an efficient and / or low power consumption means of control for a vehicle. It may be that each electrohydraulic unit / system is configured to communicate with a central vehicle controller. Alternatively or additionally, it may be that each electrohydraulic unit / system is configured to communicate directly with each other electrohydraulic unit / system without need of a central vehicle controller. According to a fourth aspect of the disclosure, there is provided a method of operating an electrohydraulic unit, the electrohydraulic unit comprising a housing. The housing may comprise a first P-port and as second P-port. The unit may comprise a pump, for example located within the housing, configured to provide fluid to and extract fluid from a first P-port and a second P-port; a first valve (e.g. located within the housing) located between the pump and the first P-port, and a second valve (e.g. located within the housing) located between the pump and the second P-port, each valve configured to control fluid flow between the pump and each respective P-port; a first pressure sensor (e.g. located within the housing) configured to provide indication of a first pressure at the first P-port, and a second pressure sensor (e.g. located within the housing) configured to provide indication of a second pressure at the second P-port; and a controller (e.g. located within the housing). It may be that the method comprises the controller receiving status signals indicating the first and second pressures and current operation parameters of the pump, the first valve and / or the second valve. It may be that the method comprises the controller receiving a control signal indicating a target pressure at the first P-port and / or the second P-port. It may be that the method comprises the controller determining target operation parameters of the pump, the first valve and / or the second valve based on the status signals and the control signal. It may be that the method comprises controlling the pump, the first valve and / or the second valve based on the target operation parameters. According to a fifth aspect of the disclosure, there is provided an electrohydraulic suspension unit for a vehicle. It may be that the unit comprises a housing, the housing comprising at least one port, being a first P-port. The housing may comprise a second port, being a second P-port. The suspension unit may comprise an actuator, located at least partially within the housing. The actuator being, or being suitable for, connecting between the wheel and the body of a car. The suspension unit may be configured such that when the actuator is connected between the wheel and the body of the car the actuator controls the movement of the wheel relative to the car. The unit may further comprise within the housing a pump configured to provide fluid to and extract fluid from the first P-port and the second P-port (if present). The pump may also be configured to provide fluid to and extract fluid from the chambers of the actuator to cause movement of the actuator. The hydraulic actuator may comprise a piston comprising a rod and a piston head mounted on the rod, and a piston housing, wherein the piston is mounted for movement within a cavity of a housing and the piston head divides the cavity into a first chamber and a second chamber. The suspension unit may be configured such that displacement of the rod causes fluid to flow from the chamber being compressed, to the chamber being expanded. The unit may comprise within the housing, a first valve located between the pump and the first P-port. The unit may comprise within the housing a second valve located between the pump and the second P-port. It may be that each valve is configured to control fluid flow between the pump and each respective P-port. The unit may comprise within the housing a further valve(s) located between the pump and one or both chambers of the actuator of the suspension unit, for example such that the pump and further valve(s) can control the flow of fluid to one or both chambers of the actuator and thereby control the movement of the actuator. The unit may comprise, for example within the housing: a first pressure sensor configured to provide indication of a first pressure at the first P-port, and a second pressure sensor configured to provide indication of a second pressure at the second P-port (if present). The unit may comprise a further pressure sensor(s) configured to provide an indication of a pressure in one or both of the chambers of the actuator. The unit may comprise, for example within the housing, a controller configured to receive status signals indicating one or more of the first pressure, the second pressure (if present), the further pressure(s) and current operation parameters of one or more of the pump, the first valve, the second valve (if present) and any further valve(s). The controller may be configured to receive a control signal indicating a target pressure at the first P-port, in one or both of the chambers of the actuator and / or the second P-port (if present). The controller may be configured to determine target operation parameters of the pump, the first valve, the second valve and / or any further valve (s) based on the status signal(s) and the control signal. The controller may be configured to control the pump, the first valve, the second valve and / or any further valve(s) based on the target operation parameters. Thus, the electrohydraulic suspension unit may provide (active) suspension for the vehicle while also providing pressurized fluid to and / or controlling the operation of a first and / or second actuator via the P-ports. The suspension unit may have any of the features described above or below in connection with the unit, system and / or method of any other aspect. According to a sixth aspect of the disclosure, there is provided an electrohydraulic suspension system comprising the electrohydraulic suspension unit of the fifth aspect. It may be that the suspension actuator (i.e. the actuator of the suspension unit) is arranged between a wheel and a body of a vehicle. It may be that the first and / or second P-port is connected to another actuator of a vehicle as described above. In this way, the electrohydraulic suspension system may provide a means of control of the suspension system in addition to another vehicle system connected to the P-ports. Thus, additional control means for the external system may be avoided. Alternatively or additionally, the electrohydraulic suspension system may provide a compact means of control of external systems, as means of control of fluid flow to and from the P-ports is integrated with the suspension system. It may be that the electrohydraulic suspension unit further comprises, for example within the housing, an accumulator connected to the first valve, the second valve (if present) and / or any further valve(s), the accumulator configured to supply pressurised fluid to the chambers of the actuator and / or the P-ports. It may be that the electrohydraulic suspension system comprises a plurality of accumulators, each accumulator controlled by an associated valve to supply or extract fluid from a suspension actuator. It will of course be appreciated that features described in relation to one aspect of the present disclosure may be incorporated into other aspects of the present disclosure. For example, the method of the disclosure may incorporate any of the features described with reference to the apparatus of the disclosure and vice versa. Description of the Drawings Embodiments of the present disclosure will now be described by way of example only with reference to the accompanying schematic drawings of which: Fig. lisa schematic drawing of an electrohydraulic unit for a vehicle; Fig. 2 is a schematic drawing of a unit connected to multiple systems of a vehicle; Fig. 3 is a schematic drawing of an electrohydraulic suspension unit connected to multiple systems of a vehicle; Fig. 4 is a schematic drawing of an electrohydraulic unit connected to multiple systems of a vehicle; and Fig. 5 is a flow chart of an example method of operating an electrohydraulic unit. Detailed Description Fig. lisa schematic drawing of an electrohydraulic unit 1 for a vehicle. All of the components of the electrohydraulic unit 1 are contained within an external housing 2, shown schematically as a square box. First and second P-ports 8, 9 allow fluid to exit and enter the housing 2. The housing 2 may comprise connections to other external systems, for example connections for electrical power, but these are not shown for clarity. The electrohydraulic unit 1 comprises a pump 3, which comprises a rotor assembly 2 and a pump motor 24. The rotor assembly 2 is connected to a reservoir 14 via a T flow-path 18, to a first P-port 8 via a first P flow-path 6, and to a second P-port 9 via a second P flow-path 7. It will be appreciated that the reservoir 14 is an optional feature of the electrohydraulic unit 1, in that the electrohydraulic unit 1 may be a closed-loop system having no need of a reservoir. Alternatively, the reservoir 14 may be external to the electrohydraulic unit 1, for example outside the housing 2, when the electrohydraulic unit 1 is connected to a power steering reservoir. Fluid flows into and out of the electrohydraulic unit 1 via the P-ports 8, 9. A first valve 4 is located on the first P flow-path 6, and a second valve 5 is located on the second P flow-path 7. A first pressure relief valve 10 is connected to the first P flow-path 6, between the first valve 4 and the first P-port 8. A second pressure relief valve 11 is connected to the second P flow-path 7, between the second valve 5 and the second P-port 9. The pressure relief valves 10, 11 are connected to the reservoir 14 via a R flow-path 16. A first pressure sensor 20 is located on the first P flow-path 6, between the first valve 4 and the first P-port 8. A second pressure sensor 21 is located on the second P flow-path 7, between the second valve 5 and the second P-port 9. The pressure sensors 20, 21 are electrically connected to a controller 22. The controller 22 is electrically connected to the pump motor 24. The pump motor 24 is arranged to drive the rotor assembly 2. The control system 22 is also electrically connected to a first valve motor 26 and a second valve motor 27. The first valve motor 26 is arranged to move the position of the first valve 4 (for example, when the first valve 4 is a shutoff valve, between an on position and an off position). The second valve motor 27 is arranged to move the position of the second valve 5 (for example, when the second valve 5 is a proportional valve, over a range of positions). Thus, the controller 22 is able to receive status signals providing indication of the fluid pressure at the first and second P-ports 8, 9, and the current operation parameters of the pump 3 and valves 4, 5. Such operation parameters may include the position / status of the first and second valves 4, 5, and the speed and / or direction of the pump 3. The controller 22 is configured to receive a control signal (for example a control signal originating external to the electrohydraulic unit) representing a target pressure at the first P-port 8 and / or the second P-port 9. The control signal may be the result of a user input, a vehicle input and / or in response to a user action (e.g. braking, steering etc.). The controller is configured to determine target operation parameters of the pump 3, the first valve 4 and / or the second valve 5 based on the status signal and the control signal, and then control those components based on the target operation parameters. For example, the controller may send an electrical signal to the pump motor 24, the first valve motor 26 and / or the second valve motor 27 to reach the target pressure at the first P-port 8 and / or the second P-port 9. Fig. 2 is a schematic drawing of an electrohydraulic unit 200 connected to multiple systems of a vehicle. The unit 200 is similar to the electrohydraulic unit of Fig. 1, but comprises additional valves. The electrical connections between systems are not shown for clarity. A vehicle may comprise one or more of such units 200. For example, a vehicle may comprise a single unit 200 positioned centrally on the vehicle, a single unit 200 positioned on a corner of the vehicle, or multiple units 200 positioned on multiple corners of the vehicle. For example, a vehicle may comprise four such units 200; one on each of the four corners of the vehicle. In each of these arrangements, the or each unit 200 is capable of controlling the various systems connected thereto. The unit 200 comprises a first valve, which is a shutoff valve 202. The shutoff valve 202 is connected to a suspension system 204. The unit 200 comprises a second valve, which is a 3-way proportional valve 206.The 3-way proportional valve 206 is connected to a steering actuator 208. The unit 200 comprises a third valve, which is a shutoff valve 210. The shutoff valve 210 is connected to a brake system 212. The unit comprises a fourth valve, which is a 2-cam shutoff valve 214. The 2-cam shutoff valve 214 is connected to an active camber system 216 and an active aero system 218. In this way, the 2-cam shutoff valve 214 is able to control both the active camber system 216 and the active aero system 218 in unison, thus providing a compact and efficient means of control. The P-ports between each valve and the respective system are not shown for clarity. Fig. 3 is a schematic drawing of an electrohydraulic suspension unit 300 connected to multiple systems of a vehicle. In essence, the electrohydraulic suspension unit 300 is the unit 200 of Fig. 2, integrated with a suspension system. That is, the unit 200 comprises a suspension actuator 204 located at least partially within the housing of the unit 200. The electrohydraulic suspension unit 300 may be suitable for mounting between a wheel and a body of a vehicle. Features of the electrohydraulic suspension unit 300 that are similar to the unit of Fig. 2 are labelled with the same reference numerals. Thus, the electrohydraulic suspension unit 300 is able to control the steering actuator 208 via connection at a first P-port, the active camber system 216 and the active aero system 218 via connection at a second P-port, in addition to the suspension actuator 204. Fig. 4 is a schematic drawing of an electrohydraulic unit 400 connected to multiple systems of a vehicle. A broken line delineating a rectangle encompasses all of the components within the unit 400, with external systems and / or components peripheral to the broken line. A pump 402 is driven by a pump motor 404 to provide pressurised fluid to and extract pressurised fluid from a manifold 406 of the electrohydraulic unit 400. A solid line delineating a rectangle encompasses all of the components located within the manifold 406. Hydraulic connections are shown by solid straight lines, and it will be appreciated that fluid may flow in both directions along said hydraulic connections, which as a whole are referred to herein as a hydraulic circuit. Electrical connections between the sensors and a controller are not shown for clarity. The pump 402 is connected to a temperature sensor 408 and a steering pressure sensor 410, which are associated with a steering rack 412 to form an electrically powered hydraulic steering system. The output of the temperature sensor 408 may also be used to mediate control of other components within the electrohydraulic unit 400 based on the temperature of the fluid. After the temperature sensor 408 and the pressure sensor 410, the hydraulic circuit forks into two branches. The right-hand fork comprises a spur leading to a proportional valve 409, which controls the flow of fluid between the pump 402 and a first P-port 411, whereby fluid flows into and out of the unit 400 between the steering rack 412. Thus, a non-zero flow rate of fluid to and from the steering rack 412 can be varied by the proportional valve 409. The steering rack 412 amongst other components comprises a hydraulic steering actuator for assisting mechanical components of the steering rack 412 in steering the vehicle. Another spur of the right-hand branch leads to a first shutoff valve 414 driven by a first valve motor 416. The pressure of fluid after the first shutoff valve 414 is measured by a nose lift pressure sensor 418. The first shutoff valve 414 controls the fluid flow to and from a second P-port 419, where fluid exits and enters the unit 400 between a nose lift actuator 420. The nose lift actuator 420 is configured to raise and lower a front of the vehicle, for example to change the ground clearance of the vehicle. The left-hand fork of the hydraulic circuit leads to a second shutoff valve 422, driven by a second valve motor 424. The pressure of fluid after the second shutoff valve 422 is measured by a first roll pressure sensor 426. The second shutoff valve 422 controls the fluid flow to and from a third P-port 427, where fluid exits and enters the unit 400 between a first suspension roll circuit 428. After the second shutoff valve 422 is a third shutoff valve 430, driven by a third valve motor 432. The pressure of fluid after the third shutoff valve 430 is measured by a second roll pressure sensor 434. The third shutoff valve 430 controls the fluid flow to and from a fourth P-port 435, where fluid enters and exits the unit 400 between a second suspension roll circuit 436. Together, the first and second suspension roll circuits 428, 436 form a suspension roll control system. Control of the two separate circuits by the separate valves may provide improved reliability and performance of the vehicle’s roll dynamics. For example, front and rear axles of the vehicle may be independently controlled, and / or an additional circuit may provide redundancy in the vent of failure. A reservoir 438 is shown at the base of the drawing, which is configured to provide fluid to the pump 402. In this embodiment, the reservoir 438 is external to the electrohydraulic unit 400, although it will be appreciated that in other embodiments the reservoir 438 may be integrated within the electrohydraulic unit 400. Fig. 5 is a flow chart of an example method of operating an electrohydraulic unit. There is a step 500 of the controller receiving a status signal indicating the first and second pressures and current operation parameters of the pump, the first valve and / or the second valve. There is a step 502 of the controller receiving a control signal indicating a target pressure at the first P-port and / or the second P-port. There is a step 504 of the controller determining target operation parameters of the pump, the first valve and / or the second valve based on the status signal and the control signal. There is a step 506 of the controller controlling the pump, the first valve and / or the second valve based on the target operation parameters. Whilst the present disclosure has been described and illustrated with reference to particular embodiments, it will be appreciated by those of ordinary skill in the art that the disclosure lends itself to many different variations not specifically illustrated herein. Where in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present disclosure, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the disclosure that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims. Moreover, it is to be understood that such optional integers or features, whilst of possible benefit in some embodiments of the disclosure, may not be desirable, and may therefore be absent, in other embodiments.

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