EP4271582A1

EP4271582A1 - Controller for hydraulic apparatus for a vehicle

Info

Publication number: EP4271582A1
Application number: EP21836615.1A
Authority: EP
Inventors: Niall Caldwell; Alexis DOLE; Paul Marshall
Original assignee: Artemis Intelligent Power Ltd
Current assignee: Artemis Intelligent Power Ltd
Priority date: 2020-12-30
Filing date: 2021-12-30
Publication date: 2023-11-08
Also published as: WO2022144553A1

Abstract

The present invention refers to a controller for hydraulic apparatus (100) for controlling a vehicle. The controller is configured to determine (310) that an hydraulic actuator is moving in such a way that an energy return criteria is being met and, in response thereto, control (320) the hydraulic apparatus in a way to transfer energy from the hydraulic actuator to an energy storage component, via a hydraulic machine. The controller is further configured to receive (330) a propulsion demand signal indicative of a propulsion demand to propel the vehicle, and to control (340) the hydraulic apparatus in a way to transfer energy from the energy storage component to a hydraulic propulsion motor of the hydraulic apparatus to propel the vehicle in accordance with the propulsion demand.

Description

CONTROLLER FOR HYDRAULIC APPARATUS FOR A VEHICLE

Field of the invention

The present invention relates to a controller for hydraulic apparatus for a vehicle, such as a motorised vehicle, and to a method of controlling such hydraulic apparatus.

Background to the invention

It is known to store and transfer energy using hydraulic systems. It is also known to use energy stored in hydraulic systems to do work, such as to operate tools of a vehicle.

In one example, energy transferred from a hydraulic system is used to drive the propulsion system of a vehicle using a hydraulic transmission. An energy storage component in the form of a hydraulic accumulator can be provided in and selectively connected to the hydraulic system to allow energy from the hydraulic transmission to be recovered (sometimes referred to as energy regeneration) and stored in the accumulator for example during braking. The stored energy can be supplied back to the hydraulic transmission by connecting the accumulator directly to the hydraulic transmission.

Energy can be exchanged between a rotatable shaft and a hydraulic circuit via a hydraulic machine. Commonly, the hydraulic machine is torque connected to a prime mover to allow energy to be provided to the hydraulic circuit from the prime mover via the hydraulic machine. The hydraulic machine defines a plurality of working chambers in the hydraulic circuit, each working chamber partially defined by a movable working surface mechanically connected to the rotatable shaft.

Electronically commutated hydraulic machines are known in which the displacement of working fluid by each working chamber is controlled for each individual cycle of working chamber volume by the active control, in phased relation with cycles of working chamber volume, of at least low-pressure valves which connect each working chamber to a low-pressure manifold and in some embodiments (for example if the machines are to function as motors) high-pressure valves which connect each working chamber to a high-pressure manifold. Such machines can respond rapidly to changes in demand and can very closely match output to a fluctuating demand signal.

It is in this context that the present invention has been devised.

Summary of the invention

In accordance with an aspect of the present invention, there is provided a controller for hydraulic apparatus for a vehicle. The hydraulic apparatus comprises: a prime mover; a hydraulic circuit through which hydraulic fluid can flow; and a hydraulic machine having a rotatable shaft in driven engagement with the prime mover and defining a plurality of working chambers in the hydraulic circuit. Each working chamber is defined partially by a movable working surface mechanically coupled to the rotatable shaft. The hydraulic machine is configured to exchange energy with the hydraulic circuit and the prime mover by movement of the working surfaces and the rotatable shaft. The hydraulic apparatus further comprises a hydraulic actuator in a first portion of the hydraulic circuit, in fluid communication with at least one of the plurality of working chambers and comprising a movable component. The hydraulic actuator is configured to transfer energy to the hydraulic circuit when driven by movement of the movable component. The hydraulic apparatus further comprises at least one hydraulic propulsion motor in a second portion of the hydraulic circuit, separate from the first portion, having a rotatable propulsion shaft in driven engagement with a propulsion component for propelling the vehicle. The or each of the at least one hydraulic propulsion motor is configured to exchange energy with the hydraulic circuit by movement of the rotatable propulsion shaft. The hydraulic apparatus further comprises: an energy storage component in the hydraulic circuit; and a plurality of routing valves in the hydraulic circuit for selectively routing the hydraulic fluid between one or more of: the plurality of working chambers; the hydraulic actuator; the at least one hydraulic propulsion motor; and the energy storage component. The controller is configured to: determine that an energy return criteria has been met by the hydraulic actuator and, in response thereto, control at least one of the hydraulic machine and the plurality of routing valves to cause energy to be transferred from the hydraulic actuator to the energy storage component via the hydraulic machine, during movement of the movable component such that the energy return criteria is met; receive a propulsion demand signal indicative of a propulsion demand to propel the vehicle; and control at least one of the hydraulic machine and the plurality of routing valves to cause energy to be transferred from the energy storage component to the hydraulic propulsion motor to propel the vehicle using the propulsion component in accordance with the propulsion demand.

Thus, the apparatus can be controlled to recover energy from the hydraulic actuator, for example during lowering of a lifting actuator, such as by way of a return of hydraulic fluid from the actuator. Energy is typically transferred from the hydraulic actuator to the hydraulic circuit by flow of hydraulic fluid from the hydraulic actuator to the hydraulic circuit. The recovered energy is stored in the energy storage component, and is reused to power the at least one propulsion motor. Energy is typically exchanged with the energy storage component by exchange of hydraulic fluid between the energy storage component and the hydraulic circuit.

The controller may comprise one or more processors and a memory configured to store instructions which when executed by the one or more processors cause the hydraulic apparatus to carry out the functions of the controller described herein. The memory may be non-transitory, computer readable memory. The memory may have the instructions stored thereon. The present invention extends to a non-transitory computer-readable medium (e.g. memory) having the instructions stored thereon to control the apparatus as described herein. The memory may be solid-state memory.

Viewed from another aspect, there is provided a method of controlling a hydraulic apparatus for a vehicle. The hydraulic apparatus comprises: a prime mover; a hydraulic circuit through which hydraulic fluid can flow; and a hydraulic machine having a rotatable shaft in driven engagement with the prime mover and defining a plurality of working chambers in the hydraulic circuit. Each working chamber is defined partially by a movable working surface mechanically coupled to the rotatable shaft. The hydraulic machine is (e.g. configured) to exchange energy with the hydraulic circuit and the prime mover by movement of the working surfaces and the rotatable shaft. The hydraulic apparatus further comprises a hydraulic actuator in a first portion of the hydraulic circuit, in fluid communication with at least one of the plurality of working chambers and comprising a movable component. The hydraulic actuator is configured to transfer energy to the hydraulic circuit when driven by movement of the movable component. The hydraulic apparatus further comprises at least one hydraulic propulsion motor in a second portion of the hydraulic circuit, separate from the first portion, having a rotatable propulsion shaft in driven engagement with a propulsion component for propelling the vehicle. The or each of the at least one hydraulic propulsion motor is configured to exchange energy with the hydraulic circuit by movement of the rotatable propulsion shaft. The hydraulic apparatus further comprises: an energy storage component in the hydraulic circuit; and a plurality of routing valves in the hydraulic circuit for selectively routing the hydraulic fluid between one or more of: the plurality of working chambers; the hydraulic actuator; the at least one hydraulic propulsion motor; and the energy storage component. The method comprises: determining that an energy return criteria has been met by the hydraulic actuator and, in response thereto, controlling at least one of the hydraulic machine and the plurality of routing valves to cause energy to be transferred from the hydraulic actuator to the energy storage component via the hydraulic machine, during movement of the movable component such that the energy return criteria is met; receiving a propulsion demand signal indicative of a propulsion demand to propel the vehicle; and controlling at least one of the hydraulic machine and the plurality of routing valves to cause energy to be transferred from the energy storage component to the hydraulic propulsion motor to propel the vehicle using the propulsion component in accordance with the propulsion demand.

Thus, there is provided a method for controlling the hydraulic apparatus to recover energy from the actuator, such as when lowering the actuator, and to store the recovered energy in the energy storage component. Subsequently, the stored energy can be reused in a separate part of the hydraulic apparatus, such as to provide at least some of the energy required to power the hydraulic propulsion motor. Advantageously, the present inventors have realised that not only is it possible to recover energy from the hydraulic actuator of a hydraulic apparatus having both the hydraulic actuator and the hydraulic propulsion motor, to be stored in the energy storage component, but that the recovered energy from the hydraulic actuator can be subsequently transferred to the hydraulic propulsion motor. In other words, the recovered energy from the hydraulic actuator can be used to drive the hydraulic propulsion motor.

It will be understood that the energy return criteria is substantially any criteria of the hydraulic apparatus indicative of energy being returned to the hydraulic circuit from the hydraulic actuator. If the energy return criteria is being met, then energy is being transferred from the hydraulic actuator to the hydraulic circuit.

Although the hydraulic actuator has been described as being configured to transfer energy to the hydraulic circuit by movement of the movable component, it will be understood that the hydraulic actuator is typically also configured to receive energy from the hydraulic circuit to cause movement of the movable component.

The movable component may be configured to be mechanically connected to a further movable component of the vehicle in which the hydraulic apparatus is provided. In some examples, the further movable component may be a lifting arm.

The volume of the working chamber may vary cyclically with rotation of the rotatable shaft.

The invention may relate particularly to electronically commutated hydraulic machines which intersperse active cycles of working chamber volume, where there is a net displacement of hydraulic working fluid, with inactive cycles of working chamber volume, where there is no net displacement of hydraulic working fluid between the working chamber and the hydraulic circuit. Typically, the majority or all of the active cycles are full stroke cycles, in which the working chambers displace a predetermined maximum displacement of working fluid by suitable control of the timing of valve actuation signals. It is also known to regulate low- and optionally high-pressure valves of one or more of the plurality of working chambers to regulate the fraction of maximum displacement made during an active cycle by operating so-called part stroke cycles. However, such machines typically intersperse active and inactive cycles, with the active cycles being full stroke cycles, with the fraction of cycles which are active cycles (the active cycle fraction) varied to achieve a demanded fractional displacement, instead of operating with only part stroke cycles.

The controller may be configured (e.g. programmed) to control the low- and optionally high-pressure valves of the working chambers to cause each working chamber to carry out either an active or an inactive cycle of working chamber volume during each cycle of working chamber volume.

By ‘active cycles’ we refer to cycles of working chamber volume which make a net displacement of working fluid. By ‘inactive cycles’ we refer to cycles of working chamber volume which make no net displacement of working fluid (typically where one or both of the low-pressure valve and high-pressure valve remain closed throughout the cycle). Typically, active and inactive cycles are interspersed to meet the demand indicated by the demand signal. This contrasts with machines which carry out only active cycles, the displacement of which may be varied.

The demand signal for one or more working chambers of the hydraulic machine is typically processed as a ‘displacement fraction’, Fd, being a target fraction of maximum displacement of working hydraulic fluid per rotation of the rotatable shaft. A demand expressed in volumetric terms (volume of working hydraulic fluid per second) can be converted to displacement fraction taking into account the current speed of rotation of the rotatable shaft and the number of working chambers connected in a group to the same high pressure manifold and one or more hydraulic components (e.g. the hydraulic actuator or the hydraulic propulsion motor) of the hydraulic apparatus. The demand signal relates to a demand for the combined fluid displacement of the group of one or more working chambers fluidically connected to the said one or more hydraulic components of the hydraulic apparatus via the hydraulic circuit. There may be other groups of one or more working chambers fluidically connected to one or more other hydraulic components having respective demand signals.

It may be that at least the low-pressure valves (optionally the high-pressure valves, optionally both the low-pressure valves and the high-pressure valves) are electronically controlled valves, and the controller or a further controller is configured to control the (e.g. electronically controlled) valves in phased relationship with cycles of working chamber volume to thereby determine the net displacement of hydraulic fluid by each working chamber on each cycle of working chamber volume. The method may comprise controlling the (e.g. electronically controlled) valves in phased relationship with cycles of working chamber volume to thereby determine the net displacement of hydraulic fluid by each working chamber on each cycle of working chamber volume.

Groups of one or more working chambers may be dynamically allocated to respective groups of one or more hydraulic components in the hydraulic circuit (e.g. the hydraulic actuator and/or the hydraulic propulsion motor) to thereby change which one or more working chambers are connected to (e.g. a group of) hydraulic components, for example by opening or closing electronically controlled valves (e.g. high-pressure valves and low-pressure valves, described herein), e.g. under the control of a controller. Groups of (e.g. one or more) working chambers may be dynamically allocated to (respective) groups of (e.g. one or more) hydraulic components to thereby change which working chambers of the machine are coupled to which hydraulic components, for example by opening and/or closing (e.g. electronically controlled) valves, e.g. under the control of the or a further controller. The net displacement of hydraulic fluid through each working chamber (and/or each hydraulic component) can be regulated by regulating the net displacement of the working chamber or chambers which are connected to the hydraulic component or components. Groups of one or more working chambers are typically connected to a respective group of one or more said hydraulic components through a said manifold.

It may be that the rate of flow of hydraulic fluid accepted by, or output by, each working chamber is independently controllable. It may be that the flow of hydraulic fluid accepted by, or produced by each working chamber can be independently controlled by selecting the net displacement of hydraulic fluid by each working chamber on each cycle of working chamber volume. This selection is typically carried out by the controller.

Typically, the hydraulic machine is operable as a pump, in a pump operating mode or is operable as a motor in a motor operating mode. It may be that some of the working chambers of the hydraulic machine may pump (and so some working chambers may output hydraulic fluid) while other working chambers of the hydraulic machine may motor (and so some working chambers may input hydraulic fluid). It will be understood that the hydraulic propulsion motor may also be partially powered using energy transferred into the hydraulic circuit by rotation of the rotatable shaft by the prime mover. In other words, not all of the energy consumed by the at least one propulsion motor may be supplied from energy stored in the energy storage component.

The first portion and the second portion of the hydraulic circuit are typically different, and typically separate, portions of the hydraulic circuit. The hydraulic circuit may comprise further portions in addition to the first portion and the second portion. It may be that the first portion of the hydraulic circuit is separated from the second portion of the hydraulic circuit by the hydraulic machine. In other words, for a component of the hydraulic apparatus in the first portion of the hydraulic circuit to exchange energy with a component of the hydraulic apparatus in the second portion of the hydraulic circuit via the hydraulic circuit, it may be necessary to exchange energy between the component in the first portion of the hydraulic circuit and the hydraulic machine and also to exchange energy between the hydraulic machine and the component in the second portion of the hydraulic circuit. By providing the hydraulic actuator in the first portion of the hydraulic circuit and the hydraulic propulsion motor in the second portion of the hydraulic circuit, it is possible to drive both the hydraulic propulsion motor and the hydraulic actuator at the same time without significant energy loss. It will be understood that in some applications, the pressure required by the hydraulic actuator may be less, and sometimes much less, than the pressure required to drive the hydraulic propulsion motor. Therefore, without separation of the first portion and the second portion, it would sometimes otherwise be necessary to reduce the pressure of (sometimes referred to as “throttle”) the hydraulic fluid in the hydraulic circuit before bringing it into fluid communication with the hydraulic actuator. The present disclosure reduces or even completely eliminates this requirement.

The energy storage component will be understood to be substantially any component capable of extracting at least some of the energy in the hydraulic circuit and storing the extracted energy. The energy storage component may be a hydraulic accumulator. Thus, energy can be extracted from the hydraulic circuit in an efficient way. The hydraulic accumulator may be an energy storage component into/out of which pressurised hydraulic fluid can flow. The energy storage component may be an electrical battery, such as an electrochemical battery. The energy storage component may be an electric supercapacitor. The energy storage component may be a kinetic energy recovery system, KERS, component, such as a flywheel.

The energy storage component may be brought into fluid communication with the hydraulic machine via a first flow path in the hydraulic circuit, the first flow path separate from the hydraulic actuator and the hydraulic propulsion motor. In other words, the first flow path does not include the hydraulic actuator and the hydraulic propulsion motor. The energy storage component may be brought into fluid communication with the hydraulic propulsion motor via a second flow path in the hydraulic circuit, the second flow path separate from the hydraulic machine. In other words, the second flow path does not include the hydraulic machine. Thus, there are two separate ways in which energy can be transferred between the energy storage component and the hydraulic propulsion motor. In other words, there are two separate routes by way of which hydraulic fluid can flow into or out of the energy storage component to transfer energy between the energy storage component and the hydraulic propulsion motor. As described further hereinafter, energy may be exchanged directly between the energy storage component and the hydraulic propulsion motor by direct fluid communication therebetween, or energy may be exchanged indirectly between the energy storage component and the hydraulic propulsion motor by direct fluid communication between the energy storage component and the hydraulic machine, and direct fluid communication between the hydraulic propulsion motor and the hydraulic machine.

To propel the vehicle in accordance with the propulsion demand, the energy may be transferred from the energy storage component to the hydraulic propulsion motor via the hydraulic machine. In other words, the energy storage component may transfer energy to a portion of the hydraulic circuit in fluid communication with a first subset of the plurality of working chambers of the hydraulic machine to transfer the energy to the rotatable shaft. Subsequently, or concurrently, the energy may be transferred from the rotatable shaft of the hydraulic machine to a second subset of the plurality of working chambers, different from any of the first subset, to cause transfer of energy to a portion of the hydraulic circuit in fluid communication with the hydraulic propulsion motor. This is sometimes referred to as transforming. Thus, even where the energy storage component cannot provide the hydraulic fluid conditions required to provide energy directly to the hydraulic propulsion motor (e.g. sufficient pressure and/or flow rate), the energy storage component can transfer energy to the hydraulic machine, which can itself transfer energy to the hydraulic propulsion motor via the hydraulic circuit. For example, if the energy storage component is storing hydraulic fluid at a first pressure, but the hydraulic propulsion motor requires hydraulic fluid at a second pressure, greater than the first pressure, it would not be possible to use the pressurised hydraulic fluid stored in the energy storage component to directly provide the pressurised hydraulic fluid required to drive the hydraulic propulsion motor. For this reason, it is sometimes necessary to use the transforming principles described herein.

One or more groups of working chambers (e.g. which are grouped together by virtue of a common high-pressure manifold) may operate as a pump or as a motor in alternative operating modes.

In some examples, at least one of the plurality of working chambers of the hydraulic machine may be arranged to receive hydraulic fluid to transfer energy from a portion of the hydraulic circuit to the rotatable shaft, even when rotation of the rotatable shaft causes at least one other of the plurality of working chambers to transfer energy from the hydraulic machine to another portion of the hydraulic circuit. The rotatable shaft may be caused to rotate, at least partially, by the prime mover. The rotatable shaft may be cause to rotate, at least partially, by energy transferred from a portion of the hydraulic circuit using at least one of the plurality of working chambers of the hydraulic machine in fluid communication with the portion of the hydraulic circuit from which energy is transferred.

It should be noted that transforming allows pressures and/or flow rates to be ‘transformed’ to different pressures and/or flow rates. The advantage of the digital displacement hydraulic machine, with multiservice connections, is that the transforming can be carried out by that single hydraulic machine, for example within a single machine body, by simultaneous pumping and motoring on two independently controllable service connections.

The pump-motor may be a digital displacement pump-motor. Due to the high efficiency of digital displacement pump motors, the transfer of energy from the hydraulic actuator to the energy storage component via the hydraulic machine (or any energy transfer in the hydraulic circuit using transforming of energy using the hydraulic machine) is also particularly efficient, and more efficient than alternative technologies. It will further be understood that digital displacement pump motors are particularly suited to this application due to the accurate and independent control of pressure and flow that is possible.

The hydraulic propulsion motor may be a variable displacement hydraulic motor. In this way, it will be understood that where the energy storage component is a hydraulic accumulator, hydraulic fluid can be transferred directly in the hydraulic circuit between the hydraulic accumulator and the variable displacement hydraulic motor at a range of hydraulic fluid pressures, because the displacement of the hydraulic motor can be varied to satisfy the required torque to be received or delivered by the hydraulic motor, for a given hydraulic fluid pressure. In other words, the pressure of the hydraulic fluid in the second portion of the hydraulic circuit may change from a first time to a second time, during which the hydraulic motor is active, even for a constant torque to be output by (or input from) the hydraulic motor.

It will be understood that in one example, the energy may be transferred from the energy storage component to the portion of the hydraulic circuit which is in fluid communication with the hydraulic machine by causing hydraulic fluid to flow from the energy storage component into the portion of the hydraulic circuit in fluid communication with the hydraulic machine.

A portion of the energy to be used by the hydraulic propulsion motor to propel the vehicle in accordance with the propulsion demand, may be supplied by torque exerted on the rotatable shaft of the hydraulic machine by the prime mover. The portion of the energy may be transferred to the hydraulic propulsion motor from the hydraulic machine via the hydraulic circuit. Thus, the propulsion of the vehicle can be caused by energy provided by the prime mover exerting torque on the rotatable shaft of the hydraulic machine, and also by energy recovered from the actuator and stored in the energy storage component before subsequently being supplied to the hydraulic machine to also exert torque on the rotatable shaft.

The hydraulic apparatus may be configured such that at least one of the plurality of working chambers can be brought into fluid communication with a first hydraulic component of the hydraulic apparatus, via the hydraulic circuit, in a first configuration of the hydraulic apparatus. The hydraulic apparatus may be further configured such that the at least one of the plurality of working chambers can be fluidly isolated from the first hydraulic component and instead brought into fluid communication with a second hydraulic component of the hydraulic apparatus, via the hydraulic circuit, in a second configuration. Thus, one or more of the working chambers can be reconfigured to be fluidly connected to different hydraulic components at different times, allowing the hydraulic machine to be used flexibly. In other words, the first hydraulic component and the second hydraulic component can each be connected to the same working chamber(s), but at different times.

It may be that the first hydraulic component is in the first portion of the hydraulic circuit and the second hydraulic component is in the second portion of the hydraulic circuit. The first hydraulic component may be a first plurality of hydraulic components. The second hydraulic component may be a second plurality of hydraulic components. The first hydraulic component may be the hydraulic actuator. The second hydraulic component may be the at least one hydraulic propulsion motor. The at least one of the plurality of working chambers may be a subset plurality of working chambers, routed together to the first hydraulic component in the first configuration and to the second hydraulic component in the second configuration.

In some examples, it may be that the hydraulic machine comprises a plurality of machine bodies, such as two machine bodies, each having a subset of the plurality of working chambers. In other examples, the hydraulic machine may be provided in the form of a single machine body. Where the hydraulic machine comprises a plurality of machine bodies, it may be that the working chambers of a first machine body are configured to provide a pumping operation and the working chambers of a second machine body are configured to provide a motoring operation. It may be that the rotatable shaft extends between each of the plurality of machine bodies.

To propel the vehicle in accordance with the propulsion demand, the energy may be transferred from the energy storage component to the hydraulic propulsion motor via a portion of the hydraulic circuit not including any of the plurality of working chambers of the hydraulic machine. In other words, the energy may be transferred directly from the energy storage component to the hydraulic propulsion motor via a portion of the hydraulic circuit providing fluid communication between the energy storage component and the hydraulic propulsion motor. Thus, if the energy storage component is capable of providing the hydraulic fluid conditions necessary to transfer energy to the hydraulic propulsion motor, the energy storage component may be used to transfer energy to the hydraulic propulsion motor especially efficiently. It may be that the energy to be transferred from the energy storage component to the hydraulic propulsion motor can be transferred either via the hydraulic machine, or via a portion of the hydraulic circuit not including any of the plurality of working chambers of the hydraulic machine, based on at least one operational characteristic of the hydraulic apparatus and/or operational characteristics of the vehicle.

Under certain conditions, it may be more efficient for energy to be transferred directly from the energy storage component to the propulsion motor, compared to transfer via the plurality of working chambers.

The method may further comprise: receiving a demand signal indicative of a movement demand to move the movable component of the hydraulic actuator such that the energy return criteria is not met; and controlling at least one of the hydraulic machine and the plurality of routing valves to cause energy to be transferred from the hydraulic circuit to the hydraulic actuator to move the movable component in accordance with the movement demand. The controller may be configured to: receive the demand signal indicative of the movement demand to move the movable component of the hydraulic actuator such that the energy return criteria is not met; and control at least one of the hydraulic machine and the plurality of routing valves to cause energy to be transferred from the hydraulic circuit to the hydraulic actuator to move the movable component in accordance with the movement demand.

The energy to be transferred to the hydraulic actuator may be from the energy storage component.

Thus, energy stored in the energy storage component can also be used to supply at least some of the energy necessary to move the hydraulic actuator from which the energy was recovered. In some examples, the energy stored in the energy storage component can be used to supply at least some of the energy necessary to move a further hydraulic actuator, different to the hydraulic actuator from which the energy was recovered. In other words, energy recovered from the hydraulic actuator, and stored in the energy storage component, may be used to transfer energy to either or each of the hydraulic propulsion motor and the (or a further) hydraulic actuator.

It will be understood that if the hydraulic actuator is moving in such a way that the energy return criteria is not being met, then energy is not being transferred from the hydraulic actuator to the hydraulic circuit. Typically, in such situations, energy is being transferred from the hydraulic circuit to the hydraulic actuator to cause movement of the movable component.

The energy to be transferred to the hydraulic actuator may be from the hydraulic propulsion motor without passing through the energy storage component.

The hydraulic actuator may be further configured to receive energy from the hydraulic circuit to cause movement of the movable component.

To move the movable component in accordance with the movement demand, the energy may be transferred from the energy storage component to the hydraulic actuator via the hydraulic machine. In other words, the energy storage component may transfer energy to a portion of the hydraulic circuit in fluid communication with a first subset of the plurality of working chambers of the hydraulic machine to transfer the energy to the rotatable shaft. Subsequently, the energy may be transferred from the rotatable shaft of the hydraulic machine to a second subset of the plurality of working chambers, different from any of the first subset, to cause transfer of energy to a portion of the hydraulic circuit in fluid communication with the hydraulic actuator. As described hereinbefore, this is sometimes referred to as transforming. Thus, even where the energy storage component cannot provide the hydraulic fluid conditions required to provide energy directly to the hydraulic actuator to meet the further movement demand (e.g. sufficient pressure and/or flow rate), the energy storage component can transfer energy to the hydraulic machine, which can itself transfer energy to the hydraulic actuator via the hydraulic circuit. It will be understood that the energy required by the hydraulic actuator to meet the movement demand may come only partially from the energy storage component, and partially from another source, for example from energy transferred to the hydraulic machine by torque exerted on the rotatable shaft by the prime move, from a further energy storage component, or from recovery of energy from a further hydraulic component of the hydraulic apparatus (such as a further hydraulic actuator, or a further hydraulic propulsion motor).

The movement demand may be to be satisfied whilst the hydraulic apparatus is also meeting the propulsion demand. In other words, it may be that the hydraulic apparatus is configured to use energy to move the hydraulic actuator at the same time as also using energy to propel the vehicle. Thus, energy can be transferred from the energy storage component to the hydraulic machine and used to energy transfer from the hydraulic machine to both the hydraulic propulsion motor and the hydraulic actuator. In some examples, it may be that the energy is transferred directly from the energy storage component to the hydraulic propulsion motor.

The method may further comprise: receiving a braking signal indicative of a braking demand to brake the vehicle; and controlling at least one of the hydraulic machine and the plurality of routing valves to cause energy to be transferred from the hydraulic propulsion motor to the second portion of the hydraulic circuit, during the braking of the vehicle in accordance with the braking demand.

The controller may be configured to: receive the braking signal indicative of the braking demand to brake the vehicle; and control at least one of the hydraulic machine and the plurality of routing valves to cause energy to be transferred from the hydraulic propulsion motor to the energy storage component via the second portion of the hydraulic circuit, during the braking of the vehicle in accordance with the braking demand.

The energy may be transferred from the hydraulic propulsion motor to the energy storage component.

Thus, the energy storage component can recover energy from either (or both) of the hydraulic actuator and the hydraulic propulsion motor.

In other examples, the energy may be transferred from the hydraulic propulsion motor to another component of the hydraulic circuit, such as to the hydraulic actuator. Typically, the energy is transferred from the hydraulic propulsion motor to the hydraulic actuator via the hydraulic machine.

As used herein, it will be understood that braking the vehicle means substantially any action to restrict movement of the hydraulic propulsion motor such that the vehicle moves more slowly than otherwise would have been the case without the braking action. In other words, even if the vehicle speeds up (but more slowly than it otherwise would have done without the braking), this is still considered to be braking the vehicle. A first portion of the energy from the hydraulic propulsion motor may be transferred to the energy storage component whilst a second portion of the energy from the hydraulic propulsion motor may be simultaneously transferred to the hydraulic actuator via the hydraulic machine. The first portion of the energy from the hydraulic propulsion motor may be transferred to the energy storage component via the hydraulic machine.

To move the movable component in accordance with the movement demand, a portion of the energy to be used by the hydraulic actuator may be supplied by torque exerted on the rotatable shaft of the hydraulic machine by the prime mover. The portion of the energy may be transferred to the hydraulic actuator from the hydraulic machine via the hydraulic circuit.

In response to determining that the energy return criteria has been met at a further time, and in response to receiving a further propulsion demand signal indicative of a further propulsion demand to propel the vehicle during the further time, the method may further comprise controlling at least one of the hydraulic machine and the plurality of routing valves to cause energy to be transferred from the hydraulic actuator to the hydraulic propulsion motor, via the hydraulic machine, to propel the vehicle in accordance with the further propulsion demand, during movement of the movable component such that the energy return criteria is met.

In response to determining that the energy return criteria has been met at a further time, and in response to receiving a further propulsion demand signal indicative of a further propulsion demand to propel the vehicle during the further time, the controller may be configured to control at least one of the hydraulic machine and the plurality of routing valves to cause energy to be transferred from the hydraulic actuator to the hydraulic propulsion motor, via the hydraulic machine, to propel the vehicle in accordance with the further propulsion demand, during movement of the movable component such that the energy return criteria is met.

Thus, the energy from the hydraulic actuator need not be stored in the energy storage component before being used by the hydraulic propulsion motor.

At least one of the hydraulic machine and the plurality of routing valves may be controlled to cause energy to be transferred from the hydraulic propulsion motor, for example kinetic energy during the braking of the vehicle in accordance with the braking demand.

The movement of the movable component such that the energy return criteria is met may correspond to a lowering movement of the hydraulic actuator. Thus, the hydraulic actuator may be a lifting ram or similar, and may be configured to convert and recover energy during lowering or some other operation, to capture the otherwise lost potential energy (gravitational, sprung, etc) of the movable component of the hydraulic actuator.

The movement of the movable component such that the energy return criteria is met may correspond to a braking movement of the hydraulic actuator. In other words, the energy recovery from the hydraulic actuator may be as a result of reducing momentum (i.e. velocity) of moving components configured to be movable by the hydraulic actuator. In some examples, the component may have a relatively high inertia. The braking movement may be a spring recovery movement. In other words, the energy to be recovered from the actuator to the hydraulic circuit may be as a result of movement of the hydraulic actuator caused by oscillatory movement of a further component mounted to the moveable component thereof.

The energy storage component may be separated from the first portion of the hydraulic circuit by the hydraulic machine. In other words, in some examples, there may be no direct fluid communication pathway between the energy storage component and the hydraulic actuator in the first portion of the hydraulic circuit. Specifically, in the direction of flow from the energy storage component, the energy storage component may be separated from the first portion of the hydraulic circuit by the hydraulic machine. Thus, the hydraulic apparatus prevents direct fluid communication from the energy storage component to the hydraulic actuator. It will be understood that the hydraulic actuator will typically require precise control, which may be difficult to achieve from the energy storage component. Therefore, to improve safety and precise operation of the hydraulic apparatus, there may be no fluid communication path allowing fluid communication from the energy storage component to the hydraulic actuator.

The energy storage component may be provided in the second portion of the hydraulic circuit. Thus, the energy storage component can be brought into fluid communication with the hydraulic propulsion motor in the second portion of the hydraulic circuit for transferring energy from the hydraulic propulsion motor to the energy storage component via the second portion of the hydraulic circuit.

The hydraulic actuator may be a plurality of hydraulic actuators, each provided in the first portion of the hydraulic circuit. Any of the functionality described herein in relation to the hydraulic actuator may apply to any one or several of the plurality of hydraulic actuators. The plurality of hydraulic actuators may together be configured to move one or more tools of the vehicle. In one example, the hydraulic actuator or at least one of the plurality of hydraulic actuators may be arranged to facilitate movement (e.g. vertical movement) of an arm of the vehicle. The plurality of hydraulic actuators may comprise at least one hydraulic actuator from which recovery of energy is not possible.

It will be understood that a hydraulic actuator is substantially any component in the hydraulic circuit configured to convert between energy in the hydraulic circuit and kinetic energy of the movable component. The movement of the movable component may be linear movement. The movement of the movable component may be rotational movement.

Where the apparatus comprises a plurality of hydraulic actuators, a priority valve may be provided to restrict (or even substantially prevent) fluid communication between the hydraulic machine and at least one of the plurality of hydraulic actuators unless sufficient flow is already being provided to meet the demand of at least one priority actuator among the plurality of hydraulic actuators. Thus, hydraulic fluid is not diverted to lower-priority hydraulic actuators where it is needed to power any one or more of the priority actuators.

The hydraulic machine may be configured such that one rotation of the rotatable shaft causes exactly one cyclic variation of the volume of each of the plurality of working chambers. It may be that there is no geared relationship between rotation of the rotatable shaft and any of the working chambers.

The prime mover may comprise a prime mover shaft which is directly coupled to (optionally integrated with) the rotatable shaft such that they rotate together at the same angular speed (i.e. in a 1 : 1 gearing ratio). Typically, the prime mover shaft is coupled to (optionally integrated with) the rotatable shaft without intermediate gearing. The apparatus may further comprise a clutch between the prime mover and the hydraulic machine to selectively decouple rotation of the rotatable shaft from the prime mover. In some examples, the clutch may only partially decouple rotation of the rotatable shaft from the prime mover. In other words, some energy may be transferred between the rotatable shaft and the prime mover via the clutch, even when the clutch partially decouples rotation of the rotatable shaft from the prime mover. Thus, even where the rotatable shaft of the hydraulic machine is rotating at high speed, this need not result in high speed rotation of a shaft of the prime mover, which may negatively affect fuel efficiency of the prime mover. In this way, the efficiency of the hydraulic apparatus can be improved.

It will be understood that the plurality of routing valves are substantially any valves in the hydraulic circuit which can affect a fluid flow characteristic of the hydraulic circuit, such as a pressure, a flow rate, or a route of the hydraulic fluid through the hydraulic circuit. It will be understood that controlling at least one of the plurality of routing valves will still be understood to be controlling the plurality of routing valves. In some examples, it may be that each of the plurality of routing valves can be controlled to implement the selected at least one energy control strategy.

The plurality of routing valves may comprise a regeneration valve provided to controllably restrict fluid communication between the energy storage component and the hydraulic propulsion motor. The regeneration valve may be a proportional flow valve. It will be understood that a proportional flow valve is controllable in a first configuration to partially restrict fluid flow therethrough, in a second configuration to partially restrict fluid flow therethrough to an amount different than in the first configuration, and in a third configuration to substantially prevent fluid flow therethrough.

The plurality of routing valves may comprise a plurality of valves to bring the plurality of working chambers into fluid communication with one or more of the hydraulic actuator, the energy storage component and the hydraulic propulsion motor. In some examples, the plurality of working chambers may be grouped into a plurality of subgroups, each comprising a plurality of working chambers and to be controllably routed independently of at least one other of the plurality of sub-groups. In this way, it is possible to fluidly connect a first one of the plurality of sub-groups of working chambers to the energy storage component, whilst a second of the plurality of sub-groups is fluidly connected to the hydraulic propulsion motor and a third of the plurality of sub-groups is fluidly connected to the hydraulic actuator. The sub-groups are sometimes referred to as pump modules. It may be that each of the plurality of sub-groups can be re-routed, for example such that the first sub-group is fluidly connected to the hydraulic propulsion motor or to the hydraulic actuator, and/or such that the second sub-group is fluidly connected to the energy storage component or to the hydraulic actuator.

It may be that the hydraulic propulsion motor can be brought into fluid communication with the energy storage component to transfer energy thereto via a first flow valve, and can be brought into fluid communication with a low pressure reservoir to transfer energy thereto via the first flow valve and a second flow valve, such that energy from the hydraulic propulsion motor is transferred to the low pressure reservoir when the energy storage component is unable to store any further energy. The first flow valve and the second flow valve may be controlled together, for example by a pilot valve. The first flow valve and the second flow valve may each be a pressure relief valve. The first flow valve and the second flow valve may each be a proportional flow valve. The first flow valve and the second flow valve may each be a solenoid valve. The first flow valve and the second flow valve may be synchronised.

Thus, the arrangement of the first flow valve and the second flow valve ensures that energy can be transferred to the energy storage component in a particularly efficient way. In some examples, the arrangement of the first flow valve and the second flow valve may be a passive arrangement, in that no feedback is required from the energy storage component or from the hydraulic propulsion motor to control the first flow valve and the second flow valve.

The plurality of routing valves may comprise one or more actuator valves for controlling fluid communication with the hydraulic actuator. The one or more actuator valves may be arranged in a valve group. The valve group may further comprise at least one further valve of the plurality of routing valves, the at least one further valve for controlling fluid communication with at least one of the energy storage component and the hydraulic propulsion motor. Each valve in the valve group may be connected to one or more of the working chambers of the hydraulic machine. Thus, the use of the valve stack provides a particularly simple implementation of the plurality of routing valves. It will be understood that a valve group is a collection of valves, arranged together, for example mounted together. It will be understood that the hydraulic apparatus may include a pre-charging component to ensure that the hydraulic fluid pressure in the hydraulic circuit can be maintained above a minimum hydraulic fluid pressure to ensure operation of the hydraulic apparatus can be initialised and maintained. The pre-charging component may be driven by torque supplied from the prime mover, for example via the rotatable shaft.

The method may comprise calculating an amount of pumping of hydraulic fluid from the hydraulic machine to the propulsion motor in dependence on a pressure at the energy storage component.

The at least one propulsion motor may be a plurality of propulsion motors. At least one of the plurality of propulsion motors may be controlled independently of another of the plurality of propulsion motors.

The or each hydraulic propulsion motor may be provided in a H-bridge arrangement in the second portion of the hydraulic circuit.

The prime mover may be a combustion engine, more precisely an internal combustion engine. The prime mover may be an electric motor.

The hydraulic actuator may be a linear actuator. In other words, it may be that the actuator is capable of causing movement of the movable component along only a single axis, such as up and down along a vertical axis.

Viewed from another aspect, the present invention extends to a vehicle comprising the hydraulic apparatus described hereinbefore, including the controller. The vehicle is typically a motorised vehicle. The vehicle may be a telehandler. The vehicle may be a wheel loader. The vehicle may be a forest harvester. The vehicle may be a forklift truck.

It will be understood that where the disclosure refers to transfer of energy between a component in the hydraulic circuit and the hydraulic circuit, this is typically provided by corresponding flow of hydraulic fluid. Specifically, for energy to be transferred from the component in the hydraulic circuit to the hydraulic circuit, hydraulic fluid typically flows from the component into the hydraulic circuit (vice versa transfer direction, for the reverse energy flow). Where the disclosure refers to transfer of energy between different components in the hydraulic circuit, via the hydraulic circuit, such as between a first component and a second component, this is typically provided by corresponding flow of hydraulic fluid.

The controller is typically a hydraulic apparatus controller. The controller may be a vehicle hydraulic apparatus controller.

Description of the Drawings

An example embodiment of the present invention will now be illustrated with reference to the following Figures in which:

Figure 1a is a schematic illustration of hydraulic apparatus according to an example of the present disclosure;

Figure 1b is a schematic illustration of an example of a portion of hydraulic apparatus, as an alternative to part of the hydraulic apparatus shown in Figure 1a;

Figure 2 is a schematic illustration of systems of a vehicle according to an example of the present disclosure;

Figure 3 shows a method according to an example of the present disclosure;

Figures 4 and 5 show additional steps for the method of Figure 3, according to an example of the present disclosure; and

Figure 6 is a schematic diagram of an electronically commutated hydraulic machine.

Detailed Description of an Example Embodiment

Figure 1a is a schematic illustration of hydraulic apparatus according to an example of the present disclosure. The hydraulic apparatus 100 is for use in a vehicle and can be used to provide energy to a propulsion unit of the vehicle and to one or more tools or other work functions of the vehicle, each to be powered hydraulically. The hydraulic apparatus 100 comprises or is mechanically connected to a prime mover 105 arranged to exert torque. The prime mover 105 is typically a motor, such as a combustion engine, arranged to convert energy from a fuel source to rotational torque. The hydraulic apparatus 100 further comprises a hydraulic circuit 110 through which hydraulic fluid can flow. The hydraulic circuit 110 is typically formed from a plurality of fluid flow conduits, such as pipework, providing a plurality of possible routes through which hydraulic fluid can flow. In particular, the hydraulic circuit comprises a first portion 112 and a second portion 114. The first portion 112 is separate from the second portion 114.

The hydraulic apparatus 100 further comprises a precharge portion 120 for ensuring the pressure in the hydraulic circuit 110 remains above a minimum operating pressure of the hydraulic circuit 110.

The hydraulic apparatus 100 further comprises a hydraulic machine 130, in the form of a digital displacement pump-motor 130. The hydraulic machine 130 comprises a rotatable shaft 132 arranged to be driven by the prime mover 105. In other words, the rotatable shaft 132 of the hydraulic machine has torque applied thereto by operation of the prime mover 105. The hydraulic machine 130 comprises a plurality of pump modules 133a, 133b, 133c, 133d, in this example four pump modules 133a, 133b, 133c, 133d, each arranged to be independently controlled to, in a first operating mode, transfer energy from the rotatable shaft 132 of the hydraulic machine 130 into the hydraulic circuit 110 by pumping hydraulic fluid into the hydraulic circuit 110, or in a second operating mode, transfer energy from the hydraulic circuit 110 to the rotatable shaft 132 of the hydraulic machine 130 by causing hydraulic fluid from the hydraulic circuit 110 to apply torque to the rotatable shaft via the respective pump module 133a, 133b, 133c, 133d. Each pump module 133a, 133b, 133c, 133d defines at least one, and typically a plurality of working chambers in the hydraulic circuit which are connected to the same high-pressure manifold and which are controlled together. Each working chamber is defined partially by a movable working surface mechanically coupled to the rotatable shaft, such that movement of the working surface and the rotatable shaft causes exchange of energy between the rotatable shaft and the hydraulic circuit.

The hydraulic machine 130 in this example further comprises a plurality of further pump units 134, 136 in driven engagement with the rotatable shaft 132, such that rotation of the rotatable shaft 132 can cause pumping by the further pump units 134, 136 as will be described further hereinafter.

The hydraulic apparatus 100 further comprises a hydraulic actuator 140a, in the form of a vertical movement actuator 140a, such as a lifting ram 140a. The hydraulic actuator 140a is in the first portion 112 of the hydraulic circuit 110. The hydraulic actuator 140a defines a working chamber. The working chamber is partially defined by a movable component 142a of the hydraulic actuator 140a, which is movable to expand or contract the working chamber to increase or reduce the volume thereof. The movable component 142a of the hydraulic actuator 140a is mechanically connected to a further movable component of the vehicle, such as a lifting arm (not shown in Figure 1a). The hydraulic actuator 140a will exchange energy with the first portion 112 of the hydraulic circuit 110 by movement of the movable component 142a. A force on the hydraulic actuator 140a caused by the weight of the components of the hydraulic actuator 140a acting on the movable component 142a as well as any external load to be carried by the lift arm, may act to cause downward movement of the movable component 142a. In this way, potential energy from the external load and the weight of the components is transferred into the first portion 112 of the hydraulic circuit 110 due to pressurisation of the hydraulic fluid. The pressurisation of the hydraulic fluid can be used to do further work by another component in the hydraulic circuit 110, for example, driving rotation of the hydraulic machine 130, as will be described further hereinafter. Conversely, if the pressurisation of the hydraulic fluid is sufficient to overcome the force on the movable component 142a of the hydraulic actuator 140a, the external load carried by the lifting arm can be raised, and the hydraulic actuator 140a can be considered to be consuming energy from the hydraulic circuit 110.

Typically, it will be understood that the exchange of energy between the hydraulic circuit 110 and the further hydraulic components, such as the hydraulic actuator 140a, is by flow of pressurised hydraulic fluid in the hydraulic circuit 110.

The hydraulic apparatus 100 further comprises a propulsion motor 150, sometimes a plurality of propulsion motors. The propulsion motor 150 is provided in the second portion 114 of the hydraulic circuit 110. The propulsion motor 150 comprises a rotatable propulsion shaft 152 in driven engagement with a propulsion component 160, in the form of a wheel 160. The wheel 160 is arranged to cause propulsion of the vehicle when driven. The propulsion motor 150 is configured to exchange energy with the second portion 114 of the hydraulic circuit 110 by rotation of the rotatable propulsion shaft 152. The propulsion motor 150 is in the form of a variable displacement pumpmotor 150. In other words, the propulsion motor 150 can be configured to, in a first operating mode, operate as a pump to cause pressurisation of hydraulic fluid passing therethrough to transfer energy from rotation of the rotatable propulsion shaft 152, or in a second operating mode, operate as a motor to use pressurisation of the hydraulic fluid passing therethrough to transfer energy to the rotatable propulsion shaft 152 by causing rotation thereof. Furthermore, a volume of a one or more working chambers of the propulsion motor 150 can be varied to provide the required operating characteristics of the propulsion motor 150 (such as a required torque of the rotatable propulsion shaft 152 from a given pressure of the hydraulic fluid, based on increasing or decreasing a flow rate of hydraulic fluid through the propulsion motor 150).

The hydraulic apparatus 100 further comprises an energy storage component 170 in the form of a hydraulic accumulator 170 arranged to store hydraulic fluid therein at a pressure exceeding atmospheric pressure, for example 300 bar (3 x 10⁷ pascal). The energy storage component 170 can be brought into fluid communication with the hydraulic propulsion motor 150. The energy storage component 170 can separately be brought into fluid communication with the hydraulic machine 130. In this example, it is not possible to bring the energy storage component 170 into direct fluid communication with the first portion 112 of the hydraulic circuit 110. In this example, the hydraulic apparatus 100 also includes a further energy storage component 172 to maintain pressure in low pressure side of the motor, to avoid cavitation. When you’ve stored pressure in the accumulator, from propel regen, then you need to provide fluid into the closed circuit (closed circuit propulsion motor needs a minimum back pressure).

The hydraulic apparatus 100 further comprises a plurality of valves in the form of a plurality of routing valves 182, 184, 186a, 186b, 188a, 188b, 190, 192. The routing valves 182, 184, 186a, 186b, 188a, 188b, 190, 192 are together for selectively routing the hydraulic fluid between the pump modules 133a, 133b, 133c, 133d of the hydraulic machine 130, the hydraulic actuator 140a, the hydraulic propulsion motor 150 and the energy storage component 170. In particular, the plurality of routing valves includes a plurality of bus valves 182 to independently control hydraulic fluid routing between each of the plurality of pump modules 133a, 133b, 133c, 133d and any one of: the first portion 112 of the hydraulic circuit 110 towards the hydraulic actuator 140a; the second portion 114 of the hydraulic circuit 110 towards the propulsion motor 150; and the energy storage component 170. In this way, any one or more (or even all) of the plurality of pump modules 133a, 133b, 133c, 133d can be brought into fluid communication with any combination of one or more of the first portion 112 of the hydraulic circuit 110, the second portion 114 of the hydraulic circuit 110 and the energy storage component 170.

The plurality of routing valves includes a propulsion regeneration valve 184 in a fluid flow path between the energy storage component 170 and the second portion 114 of the hydraulic circuit 110. The propulsion regeneration valve 184 is typically a bidirectional proportional flow valve, which is controllable to selectively regulate fluid communication between the energy storage component 170 and the second portion 114 of the hydraulic circuit 110, specifically the propulsion motor 150.

The plurality of routing valves includes a first propulsion flow control valve 186a and a second propulsion flow control valve 186b for selectively allowing fluid communication between the propulsion motor 150 and the hydraulic machine 130 and/or the energy storage component 170. A different one of the first propulsion flow control valve 186a and the second propulsion flow control valve 186b can be open (with the other being closed) depending on the direction of rotation of the hydraulic propulsion motor 150. The plurality of routing valves also includes a first propulsion proportional flow valve 188a and a second propulsion proportional flow valve 188b for selectively allowing fluid communication between the second portion 114 of the hydraulic circuit 110 and a low pressure manifold, to allow dissipation of excess pressure hydraulic fluid from the hydraulic propulsion motor 150 if necessary, for example to provide a braking function to the hydraulic propulsion motor 150.

The plurality of routing valves also includes a priority flow control valve 190 to prioritise fluid communication between the hydraulic machine 130 and the hydraulic actuator 140a, which may be referred to as a primary hydraulic actuator 140a, and to only permit fluid communication between the hydraulic machine 130 and further actuators also connected to the priority flow control valve 190 when there is sufficient fluid flow and/or hydraulic pressure in the first portion 112 of the hydraulic circuit 110 to meet a movement demand from a user for the primary hydraulic actuator 140a.

The hydraulic apparatus 100 further comprises a steering safety valve 192, in fluid communication with a hydraulic steering system 194 and with one or more further hydraulic systems 196 having one or more further hydraulic actuators, and to prioritise fluid communication between a steering system pump 134 of the hydraulic machine 130 and the steering system 194. If sufficient hydraulic fluid is provided to the steering system 194 to meet any steering demand, excess hydraulic fluid can be supplied to the further hydraulic systems 196 to supplement hydraulic fluid supplied from the other pump modules 133a, 133b, 133c, 133d of the hydraulic machine 130 via the priority flow control valve 190.

Figure 1b is a schematic illustration of an example of a portion of hydraulic apparatus, as an alternative to part of the hydraulic apparatus shown in Figure 1a. Specifically, the portion of hydraulic apparatus shown in Figure 1 b is the portion of the hydraulic circuit including the hydraulic propulsion motor 150b connected to the propulsion component 160b, and further including the energy storage component 170b in the form of the hydraulic accumulator 170b. The hydraulic circuit path 111b of Figure 1b is for connecting the hydraulic machine (not shown in Figure 1 b) to the hydraulic propulsion motor 150b for allowing energy transfer between the hydraulic machine and the hydraulic propulsion motor 150b. As in Figure 1a, the first propulsion flow control valve 186ba and the second propulsion flow control valve 186bb are provided in different routes from the hydraulic machine to the hydraulic propulsion motor 150b to allow hydraulic fluid to be supplied to either side of the hydraulic propulsion motor 150b as described hereinbefore.

The first and second propulsion proportional flow valves 188a, 188b and the propulsion regeneration valve 184 of Figure 1a are replaced by an arrangement of six controllable valves 187ba, 187bb, 189ba, 189bb, 191 ba, 191 bb, in addition to two non-return flow valves 193ba, 193bb, the function of which will be described further hereinafter.

During energy recovery by the hydraulic propulsion motor 150b, hydraulic fluid is caused to flow through the hydraulic circuit towards either of the first upper flow control valve 187ba or the second upper flow control valve 187bb, depending on the direction of rotation of the hydraulic propulsion motor 150b. If the relevant upper flow control valve 187ba, 187bb is open, hydraulic fluid flows from the relevant upper flow control valve 187ba, 187bb towards one of the first lower flow control valve 189ba and the second lower flow control valve 189bb (depending on which of the upper flow control valves 187ba, 187bb was open), as well as towards the relevant non-return flow valve 193ba, 193bb. The energy storage component 170b is in fluid communication with the non-return flow valves 193ba, 193bb. The non-return flow valves 193ba, 193bb are arranged so as to restrict (e.g. prevent) flow of hydraulic fluid therethrough in a direction away from the energy storage component 170b, but to permit flow of hydraulic fluid therethrough in a direction towards the energy storage component 170b. The energy storage component 170b is also in fluid communication with the hydraulic machine (not shown in Figure 1 b) via the energy storage component flow path 198b to allow hydraulic fluid to flow in a direction from the energy storage component 170b (or from the hydraulic propulsion motor 150b) towards the hydraulic machine via the energy storage component flow path 198b. If the relevant lower flow control valve 189ba, 189bb is open, hydraulic fluid flows from the relevant lower flow control valve 189ba, 189bb towards a low-pressure reservoir (not shown in Figure 1 b) via a low-pressure reservoir flow path 197b. The first upper flow control valve 187ba and the first lower flow control valve 189ba are both controlled by a first pilot valve 191 ba. The second upper flow control valve 187bb and the second lower flow control valve 189bb are both controlled by a second pilot valve 191 bb. The pilot valves 191 ba, 191 bb are both preset to control the respective upper and lower flow control valves to open when a pressure at an upstream end thereof exceeds a predetermined operating pressure of the energy storage component 170b. In this way, it can be seen that the system can use passive control to ensure that the energy storage component 170b receives energy from the hydraulic propulsion motor 150b until the energy storage component 170b is at capacity, at which point the energy can be routed elsewhere, such as to the hydraulic machine via the energy storage component flow path 198b, or through the relevant lower flow control valve 189ba, 189bb to the low-pressure reservoir if no better energy recovery options are available.

Figure 2 is a schematic illustration of systems of a vehicle according to an example of the present disclosure. The vehicle 200 comprises the hydraulic apparatus 100 as described with reference to Figure 1a hereinbefore (or the alternative described with reference to Figure 1 b) and a controller 210. The controller 210 is configured to exchange signals 225 with the hydraulic apparatus 100 to control the hydraulic apparatus 100 in accordance with input signals received by the controller 210, for example from user inputs by an operator of the vehicle 200. The controller 210 in this example is realised by one or more processors 230 and a computer-readable memory 240. The memory 240 stores instructions which, when executed by the one or more processors 230, cause the hydraulic apparatus 100 to operate as described herein. Although the controller 210 is shows as being part of the vehicle 200, it will be understood that one or more components of the controller 210, or even the whole controller 210 can be provided separate from the vehicle 200, for example remotely from the vehicle 200, to exchange signals with the vehicle 200 by wireless communication.

Figure 3 shows a method according to an example of the present disclosure. The method 300 is a method of controlling the hydraulic apparatus 100 described hereinbefore with reference to Figures 1a and 1b. The method 300 can be implemented by the controller 210 described with reference to Figure 2 hereinbefore.

The method 300 comprises determining 310 that an energy return criteria has been met. Specifically, the method 300 comprises determining 310 that the energy return criteria has been met by the hydraulic actuator. In other words, the method comprises determining 310 that energy is being transferred from the hydraulic actuator to the hydraulic circuit by movement of the movable component of the hydraulic actuator.

In response to determining 310 that the energy return criteria has been met by the hydraulic actuator, the method 300 comprises controlling 320 the hydraulic apparatus during movement of the movable component such that the energy return criteria is met. Specifically, the method 300 comprises controlling 320 at least one of the hydraulic machine and the plurality of routing valves to cause energy to be transferred from the hydraulic actuator to the energy storage component via the first portion of the hydraulic circuit, during movement of the further movable component such that the energy return criteria is met. In an example, the energy is transferred from the hydraulic actuator to the energy storage component by transferring the energy from the hydraulic actuator to the hydraulic machine via the first portion of the hydraulic circuit and subsequently or concurrently transferring the energy from the hydraulic machine to the energy storage component by a route different to the first portion of the hydraulic circuit. In particular, one or more pump modules of the hydraulic machine pumps hydraulic fluid from the hydraulic machine towards (e.g. to) the energy storage component. In this way, it will be understood that the hydraulic actuator may exchange energy with the hydraulic machine through transfer of a first quantity of hydraulic fluid at a first pressure, but that the hydraulic machine may exchange energy with the energy storage component through transfer of a second quantity of hydraulic fluid at a second pressure, the second quantity being less than the first quantity, but the second pressure being greater than the first pressure.

Subsequently, the method 300 comprises receiving 330 a propulsion demand signal. The propulsion demand signal is indicative of a demand to propel the vehicle using the propulsion component driven by the hydraulic propulsion motor, referred to as a propulsion demand.

In response to receiving 330 the propulsion demand signal, the method 300 comprises controlling 340 the hydraulic apparatus in accordance with the propulsion demand. Specifically, the method 300 comprises controlling 340 at least one of the hydraulic machine and the plurality of routing valves to cause energy to be transferred from the energy storage component to the hydraulic propulsion motor to propel the vehicle in accordance with the propulsion demand using the propulsion component. In the hydraulic apparatus described with reference to Figure 1a, the energy can be transferred from the energy storage component to the hydraulic propulsion motor via a route separate to the hydraulic machine, via the propulsion regeneration valve 184 and whichever of the first propulsion flow control valve 188a and the second propulsion flow control valve 188b will deliver rotation of the hydraulic propulsion motor 150 in the required rotational direction to meet the propulsion demand. Alternatively in the hydraulic apparatus described with reference to Figures 1a and 1b, the energy can be transferred from the energy storage component to the hydraulic propulsion motor via energy transfer to and from the hydraulic machine. In the alternative method, energy is first transferred from the energy storage component to the hydraulic machine via at least one of the bus valves 182. Next, energy is transferred from the hydraulic machine to the hydraulic propulsion motor via the second portion 114 of the hydraulic circuit, specifically via the whichever of the first propulsion flow control valve 188a and the second propulsion flow control valve 188b will deliver rotation of the hydraulic propulsion motor 150 in the required rotational direction to meet the propulsion demand.

Figures 4 and 5 show additional steps for the method of Figure 3, according to an example of the present disclosure. The method 400 shown in Figure 4 is to be performed at any stage after step 320 of method 300 described in relation to Figure 3 hereinbefore, specifically once energy is stored in the energy storage component. The method 400 comprises receiving 410 a demand signal. The demand signal is indicative of a movement demand to move the movable component of the hydraulic actuator in a way that requires energy to be transferred to the hydraulic actuator to cause the movement. Alternatively the demand signal may be indicative of a movement demand to move a movable component of a further hydraulic actuator in a way that requires energy to be transferred to the hydraulic actuator to cause the movement.

In response to receiving 410 the demand signal, the method 400 comprises controlling 420 the hydraulic apparatus in accordance with the component movement demand (the demand to move the movable component or the demand to move a further hydraulic actuator). Specifically, the method 400 comprises controlling 420 at least one of the hydraulic machine and the plurality of routing valves to cause energy to be transferred from the energy storage component to the hydraulic actuator (or a further hydraulic actuator) to move the movable component (or the further hydraulic actuator) in accordance with the movement demand. In an example, the energy is transferred from the energy storage component to the hydraulic actuator (or a further hydraulic actuator) by first transferring the energy from the energy storage component to the hydraulic machine via at least one of the bus valves 182 and next transferring the energy from the hydraulic machine to the hydraulic actuator (or the further hydraulic actuator) via the priority flow control valve 190. In this way, it will be understood that the energy storage component may transfer energy to the hydraulic machine through transfer of a first quantity of hydraulic fluid at a first pressure, but that the hydraulic machine may exchange energy with the hydraulic actuator through transfer of a second quantity of hydraulic fluid at a second pressure, the second quantity being greater than the first quantity, but the second pressure being less than the first pressure. Typically, the hydraulic fluid pressure provided by the energy storage component is greater than the hydraulic fluid pressure required to drive the hydraulic actuator(s).

The method 500 shown in Figure 5 is to be performed at any point in relation to the methods 300, 400 described with reference to Figures 3 and 4. The method 500 comprises receiving 510 a braking signal. The braking signal is indicative of a demand to slow down propulsion of the vehicle (or to prevent an increase in the speed of propulsion of the vehicle which would otherwise occur without further energy input from the hydraulic propulsion motor to the propulsion component).

In response to receiving 510 the braking signal, the method 500 comprises controlling 520 the hydraulic apparatus in accordance with the braking demand (the demand to move the further movable component mechanically connected to the hydraulic actuator or the demand to move a further hydraulic actuator). Specifically, the method 500 comprises controlling 520 at least one of the hydraulic machine and the plurality of routing valves to cause energy to be transferred from the hydraulic propulsion motor to the energy storage component during braking of the vehicle in accordance with the braking demand. In an example, the energy is transferred from the hydraulic propulsion motor to the energy storage component directly via a route separate to the hydraulic machine, specifically via whichever of the first propulsion flow control valve 188a and the second propulsion flow control valve 188b will have pressurised hydraulic fluid delivered thereto from the hydraulic propulsion motor during braking in the required rotational direction to meet the braking demand, and subsequently via the propulsion regeneration valve 184. Alternatively in the hydraulic apparatus described with reference to Figures 1a and 1 b, the energy can be transferred from the hydraulic propulsion motor to the energy storage component via energy transfer to and from the hydraulic machine. In the alternative method, energy is first transferred from the hydraulic propulsion motor to the hydraulic machine via the second portion 114 of the hydraulic circuit, specifically via the whichever of the first propulsion flow control valve 188a and the second propulsion flow control valve 188b will have pressurised hydraulic fluid delivered thereto from the hydraulic propulsion motor during braking in the required rotational direction to meet the braking demand. Next, energy is transferred from the hydraulic machine to the energy storage component via at least one of the bus valves 182.

Figure 6 is a schematic diagram of part of the hydraulic apparatus shown in Figures 1a and 1 b, and shows a single group of working chambers currently connected to one or more hydraulic components (e.g. an actuator or the hydraulic propulsion motor) through a high pressure manifold 654. Figure 6 provides detail on the first group 600, said group comprises a plurality of working chambers (8 are shown) having cylinders 624 which have working volumes 626 defined by the interior surfaces of the cylinders and pistons 628 (providing working surfaces 628) which are driven from a rotatable shaft 630 by an eccentric cam 632 and which reciprocate within the cylinders to cyclically vary the working volume of the cylinders. The rotatable shaft is firmly connected to and rotates with a drive shaft. A shaft position and speed sensor 634 determines the instantaneous angular position and speed of rotation of the shaft, and through a signal line 636 informs a controller 650, which enables the controller 650 to determine the instantaneous phase of the cycles of each cylinder. The working chambers are each associated with Low Pressure Valves (LPVs) in the form of electronically actuated face-sealing poppet valves 652, which have an associated working chamber and are operable to selectively seal off a channel extending from the working chamber to a low-pressure hydraulic fluid manifold 654, which may connect one or several working chambers, or indeed all as is shown here, to the low-pressure hydraulic fluid manifold hydraulic circuit. The LPVs are normally open solenoid actuated valves which open passively when the pressure within the working chamber is less than or equal to the pressure within the low-pressure hydraulic fluid manifold, i.e. during an intake stroke, to bring the working chamber into fluid communication with the low-pressure hydraulic fluid manifold but are selectively closable under the active control of the controller via LPV control lines 656 to bring the working chamber out of fluid communication with the low-pressure hydraulic fluid manifold. The valves may alternatively be normally closed valves.

The working chambers are each further associated with a respective High-Pressure Valve (HPV) 664 each in the form of a pressure actuated delivery valve. The HPVs open outwards from their respective working chambers and are each operable to seal off a respective channel extending from the working chamber through a valve block to a high-pressure hydraulic fluid manifold 658, which may connect one or several working chambers, or indeed all as is shown in Figure 6. The HPVs function as normally-closed pressure-opening check valves which open passively when the pressure within the working chamber exceeds the pressure within the high-pressure hydraulic fluid manifold. The HPVs also function as normally-closed solenoid actuated check valves which the controller may selectively hold open via HPV control lines 662 once that HPV is opened by pressure within the associated working chamber. Typically, the HPV is not openable by the controller against pressure in the high- pressure hydraulic fluid manifold. The HPV may additionally be openable under the control of the controller when there is pressure in the high-pressure hydraulic fluid manifold but not in the working chamber, or may be partially openable.

In a pumping mode, the controller selects the net rate of displacement of hydraulic fluid from the working chamber to the high-pressure hydraulic fluid manifold by the hydraulic motor by actively closing one or more of the LPVs typically near the point of maximum volume in the associated working chamber’s cycle, closing the path to the low-pressure hydraulic fluid manifold and thereby directing hydraulic fluid out through the associated HPV on the subsequent contraction stroke (but does not actively hold open the HPV). The controller selects the number and sequence of LPV closures and HPV openings to produce a flow or create a shaft torque or power to satisfy a selected net rate of displacement.

In a motoring mode of operation, the controller selects the net rate of displacement of hydraulic fluid, displaced via the high-pressure hydraulic fluid manifold, actively closing one or more of the LPVs shortly before the point of minimum volume in the associated working chamber’s cycle, closing the path to the low-pressure hydraulic fluid manifold which causes the hydraulic fluid in the working chamber to be compressed by the remainder of the contraction stroke. The associated HPV opens when the pressure across it equalises and a small amount of hydraulic fluid is directed out through the associated HPV, which is held open by the controller. The controller then actively holds open the associated HPV, typically until near the maximum volume in the associated working chamber’s cycle, admitting hydraulic fluid from the high-pressure hydraulic fluid manifold to the working chamber and applying a torque to the rotatable shaft.

As well as determining whether or not to close or hold open the LPVs on a cycle by cycle basis, the controller is operable to vary the precise phasing of the closure of the HPVs with respect to the varying working chamber volume and thereby to select the net rate of displacement of hydraulic fluid from the high-pressure to the low-pressure hydraulic fluid manifold or vice versa.

Arrows on the low pressure fluid connection 606, and the high-pressure fluid connection 621 indicate hydraulic fluid flow in the motoring mode; in the pumping mode the flow is reversed. A pressure relief valve 666 may protect the first group from damage.

In normal operation, the active and inactive cycles of working chamber volume are interspersed to meet the demand indicated by the received demand signal.

In summary, there is provided a controller for apparatus (100) for controlling a vehicle. The controller is configured to determine (310) that an energy return criteria has been met and, in response thereto, control (320) the hydraulic apparatus in a way to transfer energy from the hydraulic actuator to an energy storage component, via a hydraulic machine, when moving such that the energy return criteria has been met. The controller is further configured to receive (330) a propulsion demand signal indicative of a propulsion demand to propel the vehicle, and to control (340) the hydraulic apparatus in a way to transfer energy from the energy storage component to a hydraulic propulsion motor of the hydraulic apparatus to propel the vehicle in accordance with the propulsion demand.

Throughout the description and claims of this specification, the words “comprise” and “contain” and variations of them mean “including but not limited to”, and they are not intended to and do not exclude other components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

Features, integers, characteristics or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

36 Claims

1. A controller for hydraulic apparatus for a vehicle, the hydraulic apparatus comprising: a prime mover; a hydraulic circuit through which hydraulic fluid can flow; a hydraulic machine having a rotatable shaft in driven engagement with the prime mover and the machine defining a plurality of working chambers in the hydraulic circuit, each working chamber being defined partially by a movable working surface mechanically coupled to the rotatable shaft, such that, in operation, the hydraulic machine exchanges energy with the hydraulic circuit and the prime mover by movement of the working surfaces and the rotatable shaft; a hydraulic actuator in a first portion of the hydraulic circuit, in fluid communication with at least one of the plurality of working chambers and comprising a movable component, such that movement of the movable component causes the hydraulic actuator to transfer energy to the hydraulic circuit; at least one hydraulic propulsion motor in a second portion of the hydraulic circuit, separate from the first portion, having a rotatable propulsion shaft in driven engagement with a propulsion component for propelling the vehicle, and such that, in operation, the hydraulic propulsion motor exchanges energy with the hydraulic circuit by movement of the rotatable propulsion shaft; an energy storage component in the hydraulic circuit; and a plurality of routing valves in the hydraulic circuit for selectively routing the hydraulic fluid between one or more of: the plurality of working chambers; the hydraulic actuator; the at least one hydraulic propulsion motor; and the energy storage component, the controller is configured to: determine that an energy return criteria has been met by the hydraulic actuator and, in response thereto, control at least one of the hydraulic machine and the plurality of routing valves to cause energy to be transferred from the hydraulic actuator to the energy storage component via the hydraulic machine, during movement of the movable component such that the energy return criteria is met; receive a propulsion demand signal indicative of a propulsion demand to propel the vehicle; and control at least one of the hydraulic machine and the plurality of routing valves to cause energy to be transferred from the energy storage 37 component to the hydraulic propulsion motor, to propel the vehicle using the propulsion component in accordance with the propulsion demand.

2. A method of controlling a hydraulic apparatus for a vehicle, the hydraulic apparatus comprising: a prime mover; a hydraulic circuit through which hydraulic fluid can flow; a hydraulic machine having a rotatable shaft in driven engagement with the prime mover and the hydraulic machine defining a plurality of working chambers in the hydraulic circuit, each working chamber being defined partially by a movable working surface mechanically coupled to the rotatable shaft, such that, in operation, the hydraulic machine exchanges energy with the hydraulic circuit and the prime mover by movement of the working surfaces and the rotatable shaft; a hydraulic actuator in a first portion of the hydraulic circuit, in fluid communication with at least one of the plurality of working chambers and comprising a movable component, such that movement of the movable component causes the hydraulic actuator to transfer energy to the hydraulic circuit; at least one hydraulic propulsion motor in a second portion of the hydraulic circuit, separate from the first portion, having a rotatable propulsion shaft in driven engagement with a propulsion component for propelling the vehicle, and such that, in operation, the hydraulic propulsion motor exchanges energy with the hydraulic circuit by movement of the rotatable propulsion shaft; an energy storage component in the hydraulic circuit; and a plurality of routing valves in the hydraulic circuit for selectively routing the hydraulic fluid between one or more of: the plurality of working chambers; the hydraulic actuator; the at least one hydraulic propulsion motor; and the energy storage component, the method comprising: determining that an energy return criteria has been met by the hydraulic actuator and, in response thereto, controlling at least one of the hydraulic machine and the plurality of routing valves to cause energy to be transferred from the hydraulic actuator to the energy storage component via the hydraulic machine, during movement of the movable component such that the energy return criteria is met; receiving a propulsion demand signal indicative of a propulsion demand to propel the vehicle; and controlling at least one of the hydraulic machine and the plurality of routing valves to cause energy to be transferred from the energy storage component to the hydraulic propulsion motor, to propel the vehicle using the propulsion component in accordance with the propulsion demand.

3. The controller as claimed in claim 1 or the method as claimed in claim 2, wherein a portion of the energy to be used by the hydraulic propulsion motor to propel the vehicle in accordance with the propulsion demand is supplied by torque exerted on the rotatable shaft of the hydraulic machine by the prime mover, and the portion of the energy is transferred to the hydraulic propulsion motor from the hydraulic machine via the hydraulic circuit.

4. The controller or method as claimed in any preceding claim, wherein the hydraulic apparatus is configured such that at least one of the plurality of working chambers can be brought into fluid communication with a first hydraulic component of the hydraulic apparatus, via the hydraulic circuit, in a first configuration of the hydraulic apparatus, and can be fluidly isolated from the first hydraulic component and instead brought into fluid communication with a second hydraulic component of the hydraulic apparatus, via the hydraulic circuit, in a second configuration.

5. The controller or method as claimed in claim 4, wherein the first hydraulic component is the hydraulic actuator, and the second hydraulic component is the at least one hydraulic propulsion motor.

6. The controller or method as claimed in any preceding claim, wherein the prime mover comprises a prime mover shaft which is directly coupled to the rotatable shaft such that they rotate together at the same angular speed.

7. The controller or method as claimed in any preceding claim, wherein, to propel the vehicle in accordance with the propulsion demand, the energy is transferred from the energy storage component to the hydraulic propulsion motor via the hydraulic machine.

8. The controller or method as claimed in any preceding claim, wherein either the method further comprises: receiving a demand signal indicative of a movement demand to move the movable component of the hydraulic actuator such that the energy return criteria is not met; and controlling at least one of the hydraulic machine and the plurality of routing valves to cause energy to be transferred from the hydraulic circuit to the hydraulic actuator to move the movable component in accordance with the movement demand, or the controller is configured to: receive the demand signal indicative of the movement demand to move the movable component of the hydraulic actuator such that the energy return criteria is not met; and control at least one of the hydraulic machine and the plurality of routing valves to cause energy to be transferred from the hydraulic circuit to the hydraulic actuator to move the movable component in accordance with the movement demand, optionally wherein to move the movable component in accordance with the movement demand, the energy is transferred from the energy storage component to the hydraulic actuator, for example via the hydraulic machine.

9. The controller or method as claimed in any preceding claim, wherein either the method further comprises: receiving a braking signal indicative of a braking demand to brake the vehicle; and controlling at least one of the hydraulic machine and the plurality of routing valves to cause energy to be transferred from the hydraulic propulsion motor to the second portion of the hydraulic circuit, during the braking of the vehicle in accordance with the braking demand, or the controller is configured to: receive the braking signal indicative of the braking demand to brake the vehicle; and control at least one of the hydraulic machine and the plurality of routing valves to cause energy to be transferred from the hydraulic propulsion motor to the second portion of the hydraulic circuit, during the braking of the vehicle in accordance with the braking demand.

10. The controller or the method of claim 9, when dependent on claim 8, wherein to move the movable component in accordance with the movement demand during braking of the vehicle in accordance with the braking demand, energy from the hydraulic propulsion motor is transferred to the hydraulic actuator, via the hydraulic machine, or the controller or the method of claim 9, wherein a first portion of the energy from the hydraulic propulsion motor is transferred to the energy storage component, for example via the hydraulic machine, whilst a second portion of the energy from the hydraulic propulsion motor is simultaneously transferred to the hydraulic actuator via the hydraulic machine.

11. The controller or the method of claim 8, or any claim dependent thereon, wherein to move the movable component in accordance with the movement demand, a portion of the energy to be used by the hydraulic actuator is supplied by torque exerted on the rotatable shaft of the hydraulic machine by the prime mover, and the said portion of the energy is transferred to the hydraulic actuator from the hydraulic machine via the hydraulic circuit.

12. The controller or the method of any preceding claim, wherein, in response to determining that the energy return criteria has been met at a further time, and to receiving a further propulsion demand signal indicative of a further propulsion demand to propel the vehicle during the further time, the method further comprises: controlling at least one of the hydraulic machine and the plurality of routing valves to cause energy to be transferred from the hydraulic actuator to the hydraulic propulsion motor, via the hydraulic machine, to propel the vehicle in accordance with the further propulsion demand, during movement of the movable component such that the energy return criteria is met, or the controller is configured to: control at least one of the hydraulic machine and the plurality of routing valves to cause energy to be transferred from the hydraulic actuator to the hydraulic propulsion motor, via the hydraulic machine, to propel the vehicle in accordance with the further propulsion demand, during movement of the movable component such that the energy return criteria is met.

13. The controller or method as claimed in any preceding claim, wherein the movement of the movable component such that the energy return criteria is met corresponds to a lowering movement of the hydraulic actuator, and/or wherein the movement of the movable component such that the energy return criteria is met corresponds to a braking movement of the hydraulic actuator, and/or 41 wherein the energy storage component is separated from the first portion of the hydraulic circuit by the hydraulic machine.

14. The controller or method as claimed in any preceding claim, wherein the energy storage component is provided in the second portion of the hydraulic circuit, optionally wherein the hydraulic propulsion motor can be brought into fluid communication with the energy storage component to transfer energy thereto via a first flow valve, and can be brought into fluid communication with a low pressure reservoir to transfer energy thereto via the first flow valve and a second flow valve, wherein the first flow valve and the second flow valve are synchronised, wherein a single pilot valve controls both functions, such that energy from the hydraulic propulsion motor is transferred to the low pressure reservoir when the energy storage component is unable to store any further energy.

15. The controller or method as claimed in any preceding claim, wherein the plurality of routing valves comprises one or more actuator valves for controlling fluid communication with the hydraulic actuator, the one or more actuator valves arranged in a valve group, and wherein the valve group further comprises at least one further valve of the plurality of routing valves, the at least one further valve for controlling fluid communication with at least one of the energy storage component and the hydraulic propulsion motor, each valve in the valve group connected to one or more of the working chambers of the hydraulic machine.

16. The controller or method as claimed in any preceding claim, wherein the apparatus further comprises a clutch between the prime mover and the hydraulic machine to selectively decouple rotation of the rotatable shaft from the prime mover.

17. The controller or method as claimed in any preceding claim, wherein the energy storage component is a hydraulic accumulator.

18. A vehicle comprising: a prime mover; a hydraulic circuit through which hydraulic fluid can flow; a hydraulic machine having a rotatable shaft in driven engagement with the prime mover and the hydraulic machine defining a plurality of working chambers in the hydraulic circuit, each working chamber being defined partially by a movable working 42 surface mechanically coupled to the rotatable shaft, such that, in operation, the hydraulic machine exchanges energy with the hydraulic circuit and the prime mover by movement of the working surfaces and the rotatable shaft; a hydraulic actuator in a first portion of the hydraulic circuit, in fluid communication with at least one of the plurality of working chambers and comprising a movable component, such that movement of the movable component causes the hydraulic actuator to transfer energy to the hydraulic circuit; at least one hydraulic propulsion motor in a second portion of the hydraulic circuit, separate from the first portion, having a rotatable propulsion shaft in driven engagement with a propulsion component for propelling the vehicle, and such that, in operation, the hydraulic propulsion motor exchanges energy with the hydraulic circuit by movement of the rotatable propulsion shaft; an energy storage component in the hydraulic circuit; a plurality of routing valves in the hydraulic circuit for selectively routing the hydraulic fluid between one or more of: the plurality of working chambers; the hydraulic actuator; the at least one hydraulic propulsion motor; and the energy storage component; and the controller of any of claims 1 to 17.