Apparatus and method for controlling hydraulic actuators

Abstract

To provide an improved method of controlling actuators connected using at least two manifolds driven by pumps.SOLUTION: A hydraulic apparatus comprises first and second manifolds 110A, 110B each of which is connected to multiple actuators via corresponding actuator valves connected in parallel and operated responsively to input to regulate the flow of fluid to the actuators. Multiple working chambers are connectable to either the first or second manifold 110A, 110B and have a net flow which is controlled responsively to a negative feedback signal. The negative feedback signal is determined responsively to a calculated pressure or flow rate in virtual fluid flow paths extending from the first and second manifolds 110A, 110B.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to the field of supplying (and in some cases, receiving) a hydraulically pumped flow of hydraulic fluid to a hydraulic actuator in a hydraulic machine such as a vehicle (e.g., an excavator) or an industrial machine (e.g., an injection molding machine, a water jet cutting machine).

Background Art

[0002] Currently, the hydraulic actuators of excavators, particularly tracked excavators, are generally controlled by a hydraulic system with a manifold that extends through an open center actuator valve that can be moved by an operator using a manual control interface (e.g., a joystick). The hydraulic fluid supplied by the pump is diverted to the manifold and then flows from the manifold to the hydraulic actuators connected to various valves. Many manifolds have their own pumps and valves. The manifold also includes a throttle aperture (control orifice) with an associated pressure sensor. During use, hydraulic fluid continuously flows out of the control orifice, returns to the low pressure side, the pressure of the orifice is monitored, and the displacement of the pump is adjusted to maintain the measured pressure at a predetermined value by a negative control process. This control process is known as negacon in the art. An example can be found in US20160290370 (Doosan).

[0003] The continuous loss of hydraulic fluid through a control orifice is a waste of energy, and this requirement can be eliminated by using a highly controllable variable displacement pump. However, the existing negative control processing is preferred by excavator operators. This provides the operator with a characteristic response of the actuator to commands and useful feedback regarding the actuator's function, which can be felt, for example, when the actuator is not moving because it has hit an obstacle. This is partly due to fluctuations in the flow rate to the actuator accompanied by manifold pressure. Negative control also provides some useful damping of the actuator's movement.

[0004] It is known to provide a hydraulic control arrangement that does not include such an outlet, but allows the pump capacity to be varied to simulate the presence of leakage through the outlet. This provides the operator with the control and feedback they are familiar with and prefer.

[0005] Such a virtual control arrangement can be applied to a typical hydraulic arrangement with two or more pumps, each supplying a separate manifold to which various actuators are connected. However, it has been found that such arrangements typically cannot optimally drive high-capacity actuators that are connected to both pumps in a standard hydraulic arrangement and receive fluid from both pumps.

[0006] The present invention provides an improved method for controlling actuators connected using at least two pump-driven manifolds, while maintaining energy efficiency and providing a desirable response to actuator control commands, and in some embodiments, also providing appropriate feedback to a user who may be a typical human user of manually operable control, but could also be a machine (e.g., a robotically controlled device). [Overview of the project] [Means for solving the problem]

[0007] According to the present invention, a hydraulic system, Controller and The prime mover and A hydraulic machine comprising a rotatable shaft that engages with a prime mover, and a plurality of work chambers having a volume that periodically fluctuates with the rotation of the rotatable shaft, wherein the net displacement of one or more groups of the work chambers is independently variable under the control of a controller. Multiple hydraulic actuators, It comprises a hydraulic circuit extending between multiple work chambers and multiple hydraulic actuators, The hydraulic circuit comprises a first manifold extending between a first group of one or more work chambers and a first group of one or more actuators, a plurality of first actuator valves controllable to regulate the flow rate of hydraulic fluid from the first group of one or more work chambers to the first group of one or more actuators, a second manifold extending between a different second group of one or more work chambers and a second group of one or more actuators, and a plurality of second actuator valves controllable to regulate the flow rate of hydraulic fluid from the second group of one or more work chambers to the second group of one or more actuators. One or more work chambers are switchable by one or more gang valves between becoming part of a first group and being connected to a first manifold, and becoming part of a second group and being connected to a second manifold. The flow rates of hydraulic fluid flowing into or out of the first and second manifolds from the first and second groups of work chambers are independently variable under the control of the controller by independent control of the first and second groups of one or more work chambers (i.e., each manifold can be controlled independently), thereby allowing the pressures in the first and second manifolds to be varied independently. The first and second plurality of actuator valves have controllable positions in response to commands, thereby regulating the flow rate of fluid from the first and second manifolds to the actuators. A hydraulic system is provided in which the controller independently controls the net displacement of first and second groups of one or more work chambers, and independently varies the flow rates to or from the first and second manifolds in response to a command, thereby adjusting the actuator's response to the command.

[0008] The present invention also extends to a method for controlling a hydraulic system, which includes controlling the net displacement of first and second groups of work chambers to independently vary the flow to or from first and second manifolds (from or two first and second groups of one or more work chambers) in response to commands through an interface.

[0009] The positions of the controlled first and second actuator valves are typically the open cross-sectional areas (of the fluid conduit). As the valves open, their respective open cross-sectional areas increase, and as they close, their respective open cross-sectional areas decrease.

[0010] Therefore, the actuator's response to a command is determined by the positions of the first and second actuator valves, the flow rates of hydraulic fluid flowing into or out of the first and second manifolds, respectively, and the input pressures to the first and second manifolds, respectively. The flow rates are then determined by the net displacement of the first or second group of work chambers, which can be expressed in volume or as a fraction of the maximum displacement per revolution of the rotatable shaft, for example, which requires multiplying the maximum volumetric displacement per revolution of the rotatable shaft by the rotational speed of the rotatable shaft to give the flow rate in volume. The input pressure can be increased or decreased by displacing more or less fluid than the fluid supplied to (or received by) the actuator.

[0011] In addition to controlling the net displacement of first and second groups of one or more work chambers, the controller can, for example, control the positions of a plurality of first and second actuator valves in response to a command. The plurality of first and second actuator valves may be controlled by means other than the controller, for example, by commands from an input such as a user-operable control (e.g., pilot pressure).

[0012] Typically, the controller is configured to switch one or more work chambers from being connected to one manifold to being connected to other manifolds (first and second manifolds) by operating one or more gang valves. The switching of one or more gang valves responds to the demand for fluid flow to a first group of one or more actuators and a second group of one or more actuators, respectively. Thus, the controller may switch one or more work chambers from being connected to a first manifold to being connected to a second manifold in response to, for example, an increase in the demand for a second group of one or more actuators, a decrease in the demand for a first group of one or more actuators, or an increase in the ratio of the demand for a second group of one or more actuators to the demand for a first group of actuators. The switching may allow for a more precise meeting of the demands.

[0013] Commands are typically received via an interface. The interface can be an electronic interface. The interface can be a mechanical or hydraulic interface. The interface can communicate commands from user input devices, such as one or more joysticks, levers, pedals, or other manual user interface devices.

[0014] Therefore, the actuator's response to a command depends not only on the position of the actuator valve determined in response to the command (e.g., whether they are open or closed, or more typically, to what extent they are open), but also on the flow to each manifold, which is determined in response to the command passing through the interface, as well as by other variables such as pressure.

[0015] Pressure dependence allows for better control over the actuator's response to commands, particularly by providing characteristic actuator behavior, response, and / or feel in other, less energy-efficient hydraulic circuit configurations that are experienced by the operator and should be emulated.

[0016] Since the inflow or outflow rates to the first or second manifold are independently variable, the pressures in the first and second manifolds are independent. This is advantageous because otherwise, both groups of actuators would need to be driven using the same pressure, even though they require very different flow rates, which would otherwise be energy inefficient.

[0017] Typically, the flow rates to or from the first and second manifolds are controlled to respond to commands received by the actuators, for example, to satisfy those commands. These commands may indicate, for example, a demand for fluid flow, pressure, or actuator position. The demand may be fully satisfied. In some situations, the demand may only be partially satisfied. For example, if there is not enough fluid flow to satisfy a command, the fluid flow to individual actuators may be scaled back, for example, proportionally, or by prioritizing the flow to one or more actuators over the flow to one or more further actuators.

[0018] The device may typically include one or more first pressure sensors for measuring the pressure in the first manifold, and one or more second pressure sensors for measuring the pressure in the second manifold, in the region between each working chamber and the actuator valve, for example, when fluid enters or exits the manifold from or to a group of each working chamber.

[0019] Typically, the first manifold (and typically the second manifold) does not have a throttle aperture through which the working fluid can flow out from the first (or second) manifold to a low-pressure region during normal operation.

[0020] This is in contrast to a common excavation control arrangement in which the manifold is also connected to a controlled outlet of the pressurized working fluid (e.g., to a tank or a low-pressure manifold) via a throttle aperture (typically one or more orifices of a given cross-section), and during use, there can be a flow of hydraulic fluid through the throttle aperture from each manifold (not via one or more actuators actuated thereby).

[0021] In such an arrangement, the pressure of the working fluid in the manifold immediately before the throttle aperture is typically measured and used to control the displacement of a hydraulic machine (typically a pump) using negative feedback. These common excavation control arrangements provide a desirable link between the desired response of the actuator to a command and / or the feel of manual control (movement or force exerted thereby) to the movement of the actuator, but waste energy due to leakage of hydraulic fluid from the manifold through the throttle aperture during use.

[0022] The first and second groups of one or more actuators may not include a common actuator. However, in some embodiments, one or more actuators may be part of the first and second groups of one or more actuators. Typically, the actuators of the first and second groups of one or more actuators are each connected to only a single manifold (the first or second manifold). Each actuator of the device may be connected to only a single manifold that extends to a group of one or more working chambers.

[0023] Typically, the controller responds to a feedback signal calculated based on (virtual) characteristics within a (virtual) hydraulic circuit that includes one or more (virtual) valves that extend from the first (or second) manifold and whose position varies in response to the position of an actuator valve whose position is commanded, to control the flow to or from the first manifold (and typically also the second manifold), thereby controlling the flow of hydraulic fluid to or from the actuator through the actuator valve (including the method of controlling). The virtual characteristics can be obtained by simulating the characteristics of the virtual hydraulic circuit, taking into account measured parameters such as the position of the valve or actuator, the pressure or flow rate within the hydraulic circuit, or the torque within the rotating shaft.

[0024] The (virtual) position of the varying (virtual) valve can be a (virtual) opening cross-sectional area that varies (e.g., linearly) with the opening cross-sectional area of the actuator valve. When the opening cross-sectional area of the actuator valve is increased, the (virtual) opening cross-sectional area of the (virtual) valve can be increased or decreased.

[0025] The feedback signal can be calculated based on, for example, the pressure or flow rate of the (virtual) fluid within the (virtual) hydraulic circuit, or the position of the (virtual) actuator, or the torque within the (virtual) rotating shaft.

[0026] Typically, the controller is configured to control (and the method includes controlling) the flow to or from the first manifold (and typically the second manifold as well) in response to a calculated pressure or flow rate at a control point in a virtual fluid flow path extending from the first (or second) manifold through one or more virtual valves that modulate the virtual fluid flow depending on the position of the actuator valves.

[0027] Typically, the virtual fluid flow path extends into the low-pressure region through one or more virtual valves and virtual throttle apertures.

[0028] Typically, the controller is configured to control (and the method includes controlling) the flow to or from the first manifold in response to a calculated pressure or flow rate at each control point of a plurality of virtual fluid flow paths extending from the first (or second) manifold through one or more different virtual valves, which divert the virtual fluid flow to a lower pressure region by diverting it to a respective throttle aperture depending on the position of each actuator valve.

[0029] Flow into or from the first manifold (and typically the second manifold as well) can be controlled at a control point in the virtual fluid flow path, or at each control point in a plurality of virtual fluid flow paths, so that the inlet pressure of the first manifold (and typically the second manifold as well) fluctuates in response to a calculated pressure or flow rate.

[0030] The inlet pressure of the first (or second) manifold refers to the pressure of the fluid flowing into (or out of) the first (or second) manifold from a first (or second) group of one or more working chambers.

[0031] A first group of actuator valves may be connected in parallel to a first manifold. A first group of one or more actuators may be connected in parallel to a first manifold through their respective actuator valves. A second group of actuator valves may be connected in parallel to a first manifold. A second group of one or more actuators may be connected in parallel to a second manifold through their respective actuator valves.

[0032] Two or more virtual valves are treated as if they were connected in series in the virtual fluid flow path, while the corresponding actuator valves are connected in parallel to the first (or second) manifold.

[0033] Corresponding virtual valves and actuator valves refer to virtual valves and actuator valves that are both controlled by the same control input, typically an operator joystick command. The position of the actuator valve determines the cross-sectional area, also called the orifice area, through which actual fluid can flow, while the virtual position of the virtual valve determines the virtual cross-sectional area through which virtual flow occurs, depending on the pressure conditions upstream and downstream of the virtual valve.

[0034] There are multiple (virtual) flow paths extending parallel to the first (and typically the second as well) manifold, each containing one or more different (virtual) control valves, and the calculated pressure or flow rate in each of these flow paths may be taken into consideration when determining the flow rate from the first group (or each of the second groups) of the work chamber to the first manifold (or each of the second manifolds).

[0035] In one of the multiple flow paths extending in parallel from a first (and typically a second manifold as well), there may be multiple control valves connected in series, and in another of the multiple flow paths extending in parallel from a first (and typically a second manifold as well), there may be a single control valve. For at least one actuator, both of the multiple flow paths may have a control valve whose orifice area is determined based on the same actuator control signal.

[0036] The interface may provide an output that varies in response to the input pressure of the first and / or second manifold.

[0037] The output may be a variation in the response of a manually operated control, such as a lever, button, or wheel. A variation in response to pressure may be one or more of the following: (i) movement of the manually operated control, (ii) resistance to the movement of the manually operated control, (iii) force exerted by the manually operated control, or (iv) variation in resistance to the movement or force exerted by the manually operated control accompanying the movement. These responses to pressure in the first and / or second manifolds are useful features of known excavator control arrangements because they provide tactile feedback to the human operator. For example, they allow the operator to detect that an actuator (e.g., an excavation bucket) is in contact with an obstacle because the pressure in the manifold connected to the actuator is rising.

[0038] The output may be an electronic signal. One or more user-operable manual controls may be coupled, for example, to one or more actuator valves via hydraulic or electronic couplings. One or more actuator valves may be controlled by a controller in response to commands received via an interface (typically electronic).

[0039] One or more actuator valves, in first and second groups, are closed-center type, having a normally closed path with no normally open path to the actuator, and each of them can be opened in response to a command through an interface, allowing hydraulic fluid to flow to at least one actuator.

[0040] This is in contrast to the common valve configuration in excavators that use negative pressure feedback from the throttle aperture, which is typically based on open-center (open by default) valves connected in series.

[0041] The controller may be configured to control (and the method includes controlling) the flow to or from a first manifold (and typically also a second manifold) so that the manifold has an open outlet through which the working fluid flows through a throttle aperture into a low-pressure region during use, causing the actuator to respond to commands via an interface.

[0042] Typically, a throttle aperture that is not part of the present invention is a permanently open aperture. In the present invention, neither a throttle aperture nor an outlet pressure sensor configured to measure the pressure in a manifold adjacent to the throttle aperture exists. In the present invention, the flow rates to the first and second manifolds are not controlled in response to negative feedback of a pressure signal from an outlet pressure sensor adjacent to the throttle aperture (because the pressure sensor and throttle aperture may not exist, or because the path may be sealed through a valve (between the throttle aperture and the low-pressure region)).

[0043] The device may be configured to selectively direct (and the method may include selectively directing) (or receiving) the majority (more than 50%) (typically at least 75% or at least 90%, or 100%) of the fluid flow from multiple groups of work chambers (or groups) to a single actuator (or from) connected only to a first manifold (and not to a second manifold) through at least one actuator valve, in response to a command. This is done selectively (and temporarily) in response to a received command. This is in contrast to known devices in which the fluid is supplied from both manifolds in order to direct the majority of the fluid flow to a single actuator or to receive it from a single actuator. The device may be configured to switch, if necessary, from being connected to a second manifold to being connected to a first manifold in response to a command that enables this. The method may include switching one or more groups of work chambers from being connected to a second manifold to being connected to a first manifold in response to a command that selectively directs the majority of the fluid flow (e.g., more than 50%, or at least 75%, or at least 90%, or 100% of the fluid flow) from / to / a single actuator connected to a first manifold (but not to a second manifold) through at least one actuator valve to / from / a group of work chambers. Each actuator may be connected to either a first manifold only or a second manifold only via an actuator valve. The first group of actuators (and typically a second group as well) may comprise actuators having multiple different capacities. The first group of actuator valves may comprise actuator valves having different maximum opening cross-sectional areas.

[0044] The apparatus may be configured to selectively connect a majority (more than 50%), more than 75%, more than 90%, or all of the working chambers in a group of working chambers to one of the first or second manifolds. This occurs selectively (and temporarily) in response to a command, for example, in response to a large demand for fluid flow to or from one or more actuators.

[0045] The device may be configured such that pressure changes in the first manifold fluctuate less with respect to a given change in flow rate to the second actuator than with respect to the first actuator.

[0046] Some (or all) of the first actuator valves may be connected in parallel to provide an independently controllable parallel path for fluid flow from the first group of work chambers to the actuators.

[0047] A second actuator valve may also be connected in parallel. A first group of working chambers is controlled to regulate the flow to or from a first manifold, causing a fluid flow to a first actuator (of one or more first actuators) and / or causing a flow to or from the first manifold, and the first group may respond as if the first manifold had a throttle aperture for hydraulic fluid, which does not actually exist.

[0048] Therefore, the response of one or more actuators to a command, and potentially the feedback provided to the user, also varies as if the first manifold had such a throttle aperture. This allows the actuator movement, and potentially the device feedback, to emulate a hydraulic control circuit with such a throttle aperture, without actually needing one, thereby saving energy.

[0049] The controller can emulate some or all of a first set of open centers connected in series with each other and connected to a low-pressure region via throttle apertures for hydraulic fluid, and can calculate the pressure that would have been in the throttle apertures to determine the required displacement of the pump.

[0050] The controller may be configured, by default, to connect some of the work chambers to the first manifold, some of the work chambers to the second manifold, and additional work chambers to the first manifold (and the method includes connecting them by default) when the demand for fluid flow from the first group of actuators exceeds the maximum fluid flow rate that can be provided by the group of work chambers at that time.

[0051] Therefore, the controller may be configured to direct the working fluid to the first and second manifolds in order to operate actuators connected to the first and second manifolds, so that the first and second manifolds each simultaneously receive a portion of the net flow of the working fluid from the working chamber. The controller may also be configured to direct the working fluid to only one or more actuators connected to the first manifold, and not to any actuators connected to the second manifold, and to switch the connection of one or more working chambers from the second manifold to the first manifold.

[0052] Therefore, there may be a net flow of working fluid from the working chamber to the first manifold (e.g., more than 50% of the maximum flow rate of working fluid in the hydraulic system), but no net flow of working fluid from the working chamber to the second manifold.

[0053] Typically, the apparatus comprises a plurality of pressure sensors, including at least one pressure sensor configured to measure pressure in a first manifold and at least one pressure sensor configured to measure pressure in a second manifold. There may also be at least one pressure sensor configured to measure pressure at the input to the first manifold from a first group of work chambers and at least one pressure sensor configured to measure pressure at the input to the second manifold from a second group of work chambers. The controller typically also processes the measured pressures from the pressure sensors and control signals received via the interface to determine the displacement of at least the first and second groups of work chambers.

[0054] The controller may, in response to a command, independently control (and the method may include independently controlling) the displacements of the first and second groups of the work chamber in order to implement damping of the actuator's movement.

[0055] The controller may, in response to commands through the interface, control (and the method may include) the net displacement of the first and second groups of work chambers to independently vary the flow in the first and second manifolds.

[0056] Typically, the method further includes switching one or more work chambers from being connected to a first manifold to being connected to a second manifold. In this case, they are also swapped between groups of work chambers controlled together.

[0057] The flow to or from the first (and typically the second as well) manifold can be regulated to actively dampen the vibrations of one or more of the first group of actuators (and typically the second group of actuators as well).

[0058] Linear actuators, such as excavator booms, are prone to spontaneous vibrations that reduce controllability and can therefore affect efficiency and productivity. A closed-loop system can be fabricated to measure these vibrations (using pressure sensors, position sensors, or others) and adjust the machine flow rate to suppress them, by timing the flow rate adjustment so that the phase effect of the flow rate on the pressure is opposite to the phase of the vibration.

[0059] Typically, the commands received via the interface are the pressure of the fluid used to actuate the actuator valve (e.g., pilot pressure), or they can be, for example, electronic signals. Typically, the actuator valve is a normally closed valve.

[0060] The hydraulic circuit may comprise one or more further manifolds, each extending between each of the further groups of one or more work chambers and each of the further groups of one or more actuators, and each of the further manifolds has each of the further actuator valves, each controllable to regulate the flow of hydraulic fluid from each of the further groups of one or more work chambers to each of the further groups of one or more actuators. One or more or all of the work chambers may be switchable between being connected to a first manifold, being connected to a second manifold, and being connected to one of the further manifolds.

[0061] However, these work chambers can be connected to either the first or second manifold, and do not need to be connected to any further manifolds.

[0062] The hydraulic circuit may comprise one or more fixedly connected working chambers, which have a volume that periodically fluctuates with the rotation of a rotatable shaft and typically have a net displacement that is independently variable under the control of a controller, and which are fixedly connected to one or more further actuators through one or more further manifolds, and typically the fixedly connected working chambers cannot be switched between being connected to one manifold and being connected to another manifold.

[0063] Here, one or more embodiments of the present invention are illustrated with reference to the following drawings. [Brief explanation of the drawing]

[0064] [Figure 1] This is a schematic diagram of a known excavator actuator control system. [Figure 2] Figure 1 is a schematic diagram of a negative feedback control table from a known device. [Figure 3] This is a schematic diagram of the control arrangement of an excavator actuator according to the present invention. [Figure 4] This is a schematic diagram of a pump module for use with the present invention. [Figure 5] This is a schematic diagram of the controller. [Figure 6] This is a schematic diagram of a negative feedback control table for use in the apparatus of the present invention. [Figure 7] This is a graph of flow rate (y-axis) versus command signal (x-axis) at different functional pressures according to the present invention. [Figure 8] This corresponds to Figure 7, except for the device without feedback calculated according to the present invention. [Modes for carrying out the invention]

[0065] Referring to Figure 1, a typical hydraulic control system for hydraulic drilling machine actuators employs first and second manifolds 10A, 10B, configured to receive hydraulic fluid from variable displacement pumps 15A, 15B, respectively. Each manifold extends through a plurality of closed central actuator control valves 20A, 20B, 20C, 20D, 20E, 20F, 20G, 20H to actuators 30A (boom), 30B (bucket), 30C (dipper function), 30D (right movement), 30E (left movement), and 30F (swing function). In this example, most actuators receive fluid from a single manifold via a single, individually controllable actuator valve, while two higher-capacity actuators (boom 30A and dipper 30C) receive fluid from both manifolds via their respective flow paths, each having its own actuator valve.

[0066] The command interface includes manually operated control levers 40A, 40B, 40C, 40D, 40F, and 40H, used by the operator to control actuators 30A, 30B, 30C, 30D, 30E, and 30F. The control levers can be moved to open and close the respective actuator valves via pilot hydraulic control lines 50A, 50B, 50C, 50D, 50F, and 50H. As the valves are opened from the closed position, their open cross-sectional areas increase from zero, allowing fluid to flow from the respective manifold to the actuator. The fluid flow rate can be continuously controlled by varying the level position. In some implementations, the closed central valve can be opened in one of two opposite directions, for example, to operate the actuator in the opposite direction.

[0067] The control lines also extend to open center control valves 60A, 60B, 60C, 60D, 60E, 60F, 60G, and 60H. Open center control valves 60A, 60B, 60C, and 60D are connected in series from the first manifold 10A to the tank (low pressure) 75 via a throttle in the form of an orifice 70A with a defined cross-sectional area. Open center control valves 60E, 60F, 60G, and 60H are connected in series from the second manifold 10B to the tank (low pressure) 75 via a further throttle in the form of an orifice 70B with a defined cross-sectional area. Pressure sensors 80A and 80B measure the control pressure on the control valve side of the orifice.

[0068] An open-center control valve opens (at the point of maximum open cross-sectional area) when the corresponding actuator valve is closed (at the point of minimum open cross-sectional area), and closes when the actuator valve is opened. In some actuators, the control lever operates a single actuator valve and a corresponding single control valve. For control levers (40A, 40C) that operate actuator valves connected to each manifold, the control lines (50A, 50C) extend to the actuator valves and control valves connected to each manifold, regulating both simultaneously.

[0069] When the actuator valves are opened, fluid flows to each actuator, and the flow rate is determined by how much the actuator valve is open (its open cross-sectional area) and the input pressure at the inlet to each manifold. In a steady state, the flow rate from the pump supplies fluid at the same rate as it is consumed by the actuators.

[0070] When the actuators connected to individual manifolds are not activated, bypass fluid flow can flow from each manifold to the tank with minimal flow resistance, except through their respective orifices. Therefore, the control pressure measured at each orifice is virtually the same as the inlet pressure for the same manifold. When an actuator valve is opened, the corresponding control valve closes, increasing the flow resistance through the control valve and decreasing the control pressure relative to the input pressure.

[0071] During operation, the control pressure is continuously measured, and the displacement of each pump is varied to give a flow rate (F, y-axis) determined according to the measured control pressure (P, x-axis) (the control pressure measured by sensor 80A for the first manifold 10A, and the control pressure measured by sensor 80B for the second manifold 10B). Figure 2 shows the relationship between the measured pressure P and the flow rate F. This negative feedback configuration is known in the art as a negative control and generates a characteristic response of the actuator to a command.

[0072] It should be noted that the input pressures to the first and second manifolds are neither measured nor directly controlled, but are indirectly controlled as a result of negative feedback control of the pump flow in response to the control pressure measured in front of orifices 80A and 80B. If the fluid in the actuator is at high pressure, or if the actuator cannot move due to encountering resistance, the negative feedback control increases the flow until the input pressure stabilizes at a relatively high value, thus increasing the input pressure to each manifold. This is an important part of the feel of known negative control devices, and we recognize that it is advantageous to reproduce this feel.

[0073] Figure 3 is a schematic diagram of arrangement 100 according to the present invention. The components within the dashed box 300 are not actual components but virtual components whose functions are emulated by the controller 102, as described below. Similar to the arrangement in Figure 1, there is a first manifold 110A and a second manifold 110B, each of which extends to hydraulic actuators 130A, 130B, and 130C in the case of the first manifold, and to hydraulic actuators 130D, 130E, and 130F in the case of the second manifold. The flow from each manifold to each actuator is controlled by actuator valves 120A, 120B, 120C, and 120A' in the case of the first manifold, and by actuator valves 120D, 120E, 120F, and 120E' in the case of the second manifold. The actuator valves are controlled by the pilot pressure of hydraulic control lines 150A, 150B, 150C, 150D, 150E, and 150F, and by the control levels 140A, 140B, 140C, 140D, 140E, and 140F associated with each actuator.

[0074] Multiple pump modules 160A-H are driven by a prime mover 165 via a common rotating shaft 170 and have output manifolds 175A-H that can be switched and connected to either the first manifold 110A or the second manifold 110B via a valve network 180. The valve network is controlled by a controller 102 via a control line 195. The controller also controls the displacement of the individual pump modules. Thus, the flow rate to each manifold can be adjusted by the controller by controlling the displacement of the individual pump modules and by controlling which pump modules are grouped together and connected to each manifold. Pressure sensors 185A and 185B measure the input pressure in the first and second manifolds 110A and 110B and transmit the measured values ​​to the controller.

[0075] In this example, each actuator is connected to only one manifold containing several actuators capable of consuming the entire maximum displacement of the pump module (thus requiring connections to both manifolds of the known system in Figure 1). For these high-capacity actuators, two actuator valves connected in parallel provide fluid to a single actuator from the same manifold controlled by the same control lever; for example, actuator valves 120A and 120A' provide flow in parallel to actuator 130A from a first manifold regulated by control lever 140A, and actuator valves 120E and 120E' provide flow in parallel to actuator 130E from a second manifold regulated by control lever 140E. Nevertheless, instead of using two actuator valves in parallel, a single valve with a larger cross-sectional area for the fluid flow can be used.

[0076] The functions of the controller and pump modules will now be described with reference to Figures 4 and 5. Figure 4 is a schematic diagram of an individual pump module 160 useful for the present invention. The pump module is part of an electronically rectified hydraulic machine (ECM) 200 that houses the pump module. The ECM comprises a plurality of working chambers, each having a cylinder 202 with a working volume 204 defined by the inner surface of the cylinder, and a piston 206 driven from a rotatable shaft 170 by an eccentric cam 208, which reciprocates within the cylinder to periodically vary the working volume of the cylinder. The rotatable shaft is fixedly connected to a drive shaft and rotates together with it. A shaft position and / or speed sensor 210 determines the instantaneous angular position and / or rotational speed of the shaft and transmits it to the controller 102 via a signal line 212, thereby enabling the machine controller to determine the instantaneous phase of the cycle of each cylinder.

[0077] Each working chamber has an associated working chamber and is associated with a low-pressure valve (LPV) in the form of an electronically actuated face-seal poppet valve 214 that can operate to selectively close a channel extending from the working chamber to the low-pressure hydraulic fluid manifold 216, which can connect one or more working chambers, or in fact, all working chambers in the pump module as shown herein, to the low-pressure hydraulic fluid manifold and tank 75 of the apparatus. The LPV is a normally open solenoid operated valve that is passively open when the pressure in the working chamber is less than or equal to the pressure in the low-pressure hydraulic fluid manifold, i.e., during the intake stroke, to fluidly connect the working chamber to the low-pressure hydraulic fluid manifold, but can be selectively closed under the active control of the controller via the LPV control line 218 to prevent fluid connection between the working chamber and the low-pressure hydraulic fluid manifold. The valve may alternatively be a normally closed valve.

[0078] Each work chamber is further associated with a high-pressure valve (HPV) 220, each of which is in the form of a pressure-operated delivery valve. Each HPV is open outward from its respective work chamber, and each is operable to seal its respective channel extending from the work chamber to the high-pressure hydraulic fluid manifold 222, which can connect to one or more work chambers, or in fact all of them, as shown in Figure 2, to the high-pressure hydraulic fluid manifold 175 of the pump module. The HPV functions as a normally closed pressure-open check valve, passively opening due to the pressure difference across the valve and taking into account the force of the biasing member within the HPV. The HPV also functions as a normally closed solenoid-operated check valve, which the controller can selectively retain open via the HPV control line 224 when the HPV is opened by the pressure in the work chamber to which it is associated. Typically, the HPV is not openable by the controller for pressure in the high-pressure hydraulic fluid manifold. The HPV may be additionally openable or partially openable under the control of the controller when there is pressure in the high-pressure hydraulic fluid manifold but not in the work chamber.

[0079] In pumping mode, the controller selects the net displacement rate of hydraulic fluid from the working chamber to the high-pressure hydraulic fluid manifold by the hydraulic pump by actively closing typically one or more LPVs near the point of maximum volume in the associated working chamber cycle, thereby closing the path to the low-pressure hydraulic fluid manifold and thereby directing the hydraulic fluid through the associated HPV in the subsequent contraction stroke (but without actively opening and holding the HPV). The controller selects the number and order of LPV closures and HPV openings to generate flow or create shaft torque or power to satisfy the selected net displacement rate. The above "selection" by the controller is refreshed periodically or continuously. The selection is refreshed or updated when the pump module is moved from connection to the first manifold to the second manifold, or vice versa.

[0080] Some embodiments may include a pump module that can monitor the hydraulic fluid received back from the hydraulic actuator and regenerate energy from it, converting it into mechanical energy, for example, when the actuator is lowered or when the wheel motor acts as a pump to apply braking torque. In these cases, the working chamber of the pump module is also fitted to the motor, in which case the controller can actively control the LPV and HPV and perform a monitoring operation mode in which the controller actively closes one or more of the LPVs immediately before the point of minimum volume in the cycle of the associated working chamber by selecting the net displacement rate of the hydraulic fluid displaced by the hydraulic machine via the high-pressure hydraulic fluid manifold, thereby closing the path to the low-pressure hydraulic fluid manifold that compresses the hydraulic fluid in the working chamber by the remaining contraction stroke. The associated HPV is opened when its pressure equalizes, and a small amount of hydraulic fluid is directed through the associated HPV which is opened and held by the hydraulic machine controller. The controller then actively keeps the associated HPV open, typically until it approaches the maximum cycle volume of the associated work chamber, and introduces hydraulic fluid from the high-pressure hydraulic fluid manifold into the work chamber to apply torque to the rotatable shaft.

[0081] In addition to determining whether to close or leave the LPV open each cycle, the controller can be operated to vary the precise phase of HPV closure relative to the fluctuating working chamber volume, thereby selecting the net displacement rate of the hydraulic fluid from high pressure to low pressure in the hydraulic fluid manifold, or vice versa.

[0082] The arrows on manifolds 216 and 175 indicate the hydraulic fluid flow in pump mode, while the flow is reversed in motoring mode.

[0083] In practice, there are several pump modules, as shown in Figure 4, that are connected by a common shaft and a single controller, and typically use a single shaft position sensor capable of sending control signals to valves associated with each work chamber of each pump module. The work chambers within the pump module do not need to be evenly spaced around the shaft, but are typically arranged alternately along the shaft to distribute the load.

[0084] Therefore, although the working chambers constituting each pump module are fixed, the pump modules that provide flow to the first and second manifolds can be varied as needed.

[0085] In some embodiments, in addition to the illustrated work chamber, manifold, and actuator, there are one or more additional pump modules (equipped with one or more work chambers) coupled to a common shaft that supply (or receive) fluid to one or more further actuators via a fixed connection. This type of fixed service is useful for certain types of actuators, such as steering actuators.

[0086] Figure 5 is a schematic diagram of the controller 102. The controller includes a processor circuit 250 that electronically communicates with a memory 252 that stores a database 254 of pump modules, a database 256 of which work chambers are permanently associated with which pump modules and which pump modules are currently connected to which manifolds, and data 258 regarding the parameters of the simulated hydraulic fluid circuit 200. The controller also receives pressure and any other relevant measurement signals 260 for each of the first and second hydraulic circuit manifolds, as well as shaft position and / or velocity signals, through a signal line 262. The feedback signals 260 may be simple pressure signals, but may also receive actuator position signals, flow measurements, temperature measurements, commands, e.g., operator commands, displacement demand signals, etc. Outputs from the controller include work chamber valve control lines 218, 224 (for controlling the LPV, and HPV as needed), and a valve switching control line 264 for controlling valves in the switching block.

[0087] In some embodiments, actuator valve commands are not communicated independently of the controller; rather, the controller receives commands from, for example, an electronic interface or user input peripheral and controls the actuator valve.

[0088] During operation, the controller maintains a database of which pump modules are connected to which manifolds from the default configuration. The controller also maintains accumulators (internal variables stored in the controller) 266A, 266B of the difference between the volume of hydraulic fluid delivered to each manifold and the volume of hydraulic fluid demanded by the pump modules connected to each manifold. As the rotatable shaft rotates, a determination point is reached at different times (shaft positions) for various work chambers. At a given work chamber determination point, the controller determines which hydraulic circuit module the work chamber is connected to (this requires querying database 254 of the pump modules and which work chambers are fixedly associated with which pump modules, and database 256 of which pump modules are currently connected to which manifolds), and the controller then updates the accumulator of the manifold to which the work chamber is connected, according to the demand received for that manifold. The controller then compares the accumulator value to a threshold, and if the accumulated demand exceeds the threshold, it schedules and then sends a valve control signal to the work chamber to perform an active cycle in which the work chamber generates a net displacement of the working fluid and subtracts the net displacement of the working fluid from the value stored by the accumulator. Otherwise, the work chamber is made to perform an inactive cycle in which the work chamber does not generate a net displacement of the working fluid (for example, the controller sends a signal to the work chamber's LPV to keep the LPV open throughout the cycle of the work chamber's volume), and the accumulator remains unchanged. In this way, the controller determines for each work chamber whether to perform an active cycle in response to the demand from the manifold to which the work chamber is connected. The accumulator and demand signals can use any convenient unit. In one known example, the demand is F d It is expressed as the "displacement fraction," which is the fractional part of the maximum possible displacement per revolution of the rotating shaft. The target flow rate is expressed in terms of volume as F d It is the product of [the product of the

[0089] The controller sometimes determines that a pump module needs to be reassigned from one hydraulic circuit module to another to meet a changing demand for hydraulic fluid. In this case, the controller sends a control signal to the relevant valve in the valve network 180 to switch the high-pressure manifold of the pump module from one manifold to the other, and updates the database 256 of which pump modules are currently connected to which hydraulic circuit modules. Thus, in the future, when a decision point is reached for each working chamber of a pump module that has been switched from being assigned to one manifold to another, the controller reads the displacement accumulator value of the new manifold, and therefore the demand for hydraulic fluid through the new manifold.

[0090] Referring again to Figure 3, during operation, the actuator valves open and close in response to user commands, as before, to adjust the connections of the first and second manifolds to various actuators. However, the displacement of each pump module is determined using feedback signals associated with the manifold to which each pump module is connected, and is calculated based on the virtual fluid pressure in the calculated response of the virtual hydraulic circuit 300.

[0091] The virtual hydraulic circuit includes a first virtual circuit branch 310A that extends in series from a first manifold 100A through a throttle orifice 330A to a low-pressure sink 325 via virtual control valves 320A, 320B, and 320C. A second virtual circuit branch 310B extends from a first manifold 110A, parallel to the first virtual branch 310A, through a throttle orifice 330B to a low-pressure sink 325 via virtual control valve 320G. Correspondingly, a third virtual circuit branch 310C extends from the second manifold 110B through a throttle orifice 330C to the low-pressure sink 325 via a virtual control valve 320H, and parallel thereto, a fourth virtual circuit branch 310D extends from the second manifold 110B through a throttle orifice 330D to the low-pressure sink 325 via virtual control valves 320E, 320G, and 320H. High-capacity actuators 130A and 130E, each having dual actuator valves 120A, 120A' and 120E, 120E' (or a single high-capacity actuator valve), each having virtual control valves (320A, 320G, and 320E, 320H, respectively) corresponding to each of the two parallel virtual circuit branches extending from the manifold to which they are connected.

[0092] The parameters of the virtual hydraulic circuit 300 are stored in memory 252 and updated 258 to simulate the function of the hydraulic virtual circuit. The simulation utilizes live measurements of the input pressure in the first and second hydraulic manifolds, measured by pressure sensors 185A and 185B. The virtual control valves are treated as having an opening cross-sectional area that decreases as the opening cross-sectional area of ​​the corresponding actuator valve increases (320A and 320G are treated as more open as 120A and 120A' are more closed, 320B is treated as more open as 120B is more closed, 320C is treated as more open as 120C is more closed, 320D is treated as more open as 120D is more closed, 320E and H are treated as more open as 120E and 120E' are more closed, and 320F is treated as more open as 120F is more closed). In practice, the open cross-sectional area of ​​each virtual control valve can be determined as a parameter of the measurement of the control signal from each control lever. In some embodiments, signals from user control or from an electronic interface are used both to control the actuator valve and to determine the virtual position of the virtual control valve.

[0093] Considering the input pressures in the first and second hydraulic manifolds and the simulated open cross-sectional areas of each virtual control valve and virtual throttle orifice 330A, 330B, 330C, and 330D, the pressure drop across each virtual valve, and therefore the fluid pressure and flow rate in the hydraulic virtual circuit, are calculated. Of particular interest is the calculated pressure present in the hydraulic virtual circuit before the throttle orifice at each virtual circuit branch at positions 340A, 340B, 340C, and 340D, if they actually exist.

[0094] To perform this calculation, control signals 150A, 150B, 150C, 150D, 150E, and 150F for each actuator are monitored. For each virtual control valve 320A, 320B, 320C, 320D, 320E, 320F, 320G, and 320H, the virtual open cross-sectional area is calculated or determined from a lookup table based on the corresponding control signal. As the open cross-sectional area of ​​the corresponding actuator valve increases, as indicated by each control signal, the virtual open cross-sectional area decreases.

[0095] For each virtual hydraulic circuit branch equipped with multiple virtual control valves in series, the total equivalent open cross-sectional area A equiv This is calculated from the virtual open cross-sectional area of ​​each individual control valve A as follows:

[0096]

number

[0097] For each virtual hydraulic circuit branch, the simulated leakage flow q from each manifold passing through the circuit branch is calculated using, for example, the following formula, where A is the virtual opening cross-sectional area of ​​a single valve or, if there are multiple virtual valves, A equiv Here, ΔP is the pressure obtained by subtracting the pressure directly downstream of the valve from the pressure directly upstream of the valve, c is a coefficient that can be found experimentally (known in the art as the flow coefficient) (typically about 0.7), and ρ is the fluid density.

[0098]

number

[0099] Next, the pressures calculated in front of the virtual throttle orifices 340A, 340B, 340C, and 340D can be calculated from this flow rate, for example, using a lookup table, and the resulting pressures are used as a negative feedback signal to select the net flow rate for the group of working chambers delivering fluid to each manifold.

[0100] Referring to Figure 6, the flow rate F A F B For each of the circuit branches connected to the manifold (310A and 310B for the first manifold 110A, and 310C and 310D for the second manifold 110B), the calculated pressure P A , P B This is determined based on (340A and 340B for the first manifold 110A, and 340C and 340D for the second manifold 110B). These are then added together to determine the flow rate F of the pump module connected to each manifold.

[0101] Next, the displacement of the pump modules connected to each manifold is calculated to determine the required flow rate, and a decision is made accordingly whether to perform an active or inactive cycle for each cycle of the working chamber volume. This may involve calculating the displacement fraction (Fd) corresponding to the required flow rate, taking into account the number and capacity of the pump modules connected to each manifold, as well as the current rotational speed of the rotatable shaft.

[0102] If the displacement demand for one manifold exceeds the maximum possible demand for the working chambers of the pump modules currently connected to that manifold, one or more pump modules are moved from the other manifold by the operation of valves in the valve network 180, and the pump module allocation 256 is updated. If the total demand for both manifolds cannot be delivered at once, the pump modules may be divided between the first and second manifolds according to a predetermined prioritization scheme.

[0103] As a result, the flow delivered to each manifold is similar to that of known negative control configurations, and the feel of the system to the operator is similar to that of known negative control devices. However, several key differences and advantages exist.

[0104] Firstly, because the manifold branching is virtual, there is no actual loss of working fluid through the actual throttle orifice, thus improving energy efficiency.

[0105] Furthermore, this is achieved using relatively few additional sensors. For example, in some embodiments, only the manifold input pressure and user commands may be measured to determine the flow rate. Nevertheless, additional sensors such as additional pressure sensors (e.g., AT actuators), actuator position sensors, and flow sensors may be incorporated.

[0106] Pump modules and their working chambers can be reassigned from one manifold to another to accommodate fluctuating demands for fluid flow to different actuators. Therefore, since the majority of pump modules can be temporarily connected to a single manifold when needed, high-capacity actuators that potentially require more than half of the pump modules' maximum total output can be supplied from a single manifold.

[0107] In existing excavators, actuators are assigned to one or another manifold, partly based on how often they are used simultaneously, with a view to reducing the frequency with which two or more actuators on the same manifold are used at once. One reason for this is the energy loss associated with supplying fluid to two actuators at different pressure levels from a single pressure source. However, actuators with high flow demands require being connected to both manifolds, thereby allowing all of the combined pump flow to be delivered to them. This allows both manifolds to be combined into one manifold. In this invention, actuators that can operate simultaneously at very different pressures or flow rates can be assigned to different manifolds. Since the pump capacity connected to each manifold can be dynamically changed, the required flow can be provided to any high-flow actuator without reducing the system to a single pressure source. This improves energy efficiency.

[0108] In the example in Figure 3, parallel virtual circuit branches 310A and 310B are used to control the flow when the high-capacity actuator 130A is operated, and parallel virtual circuit branches 310C and 310D are used to control the flow when the high-capacity actuator 130E is operated. The provision of additional virtual circuit branches 310B and 310C, as well as the calculation of pressure at position 340C, 340C between the respective virtual control valves 320G, 320H and the throttle orifices 330B, 330C, and the additional actuator control valve (or a single higher cross-section actuator control valve) allows the use of more than half of the output of the pump module's flow when each high-capacity actuator is operated, without requiring those actuators to be connected to both the first and second manifolds (as per Figure 1). This is advantageous because the first and second manifolds remain at different pressures and flow rates when high-capacity actuators are used, saving energy and simplifying control. It is also made possible by the mechanical ability to move the pump module from one manifold to the other, supporting the delivery of fluid to the high-capacity actuator when operated.

[0109] Advantageously, in this example, the system flow rate and response always fluctuate with the manifold input pressure. The manifold input pressure is a critical parameter for determining the fluid flow rate to the actuator. The fluid flow to the actuator is, at any given time, a function of the manifold inlet pressure, the pressure within the actuator, and the open cross-sectional area of ​​the associated actuator valve. As described above, a typical negative control system provides this characteristic pressure dependence and therefore gives the operator a unique feel for the control system that is useful to them. This also smooths the response to some extent. Furthermore, in some configurations, the operator can actually feel the pressure within the manifold, for example, in relation to the resistance to the movement of the control joystick. The arrangement according to the present invention can advantageously replicate this feel.

[0110] This pressure dependence is shown in Figure 7, which displays the flow rate in liters per minute (y-axis) against different actuator control signal values ​​(x-axis), such as pilot pressure in the hydraulic control line from the joystick, for each of several different functional pressures, which are the pressures inside the actuators to which the fluid is supplied. This is in contrast to the corresponding response of a system that, while corresponding in the physical components, varies the flow rate of the pump module and reassigns the pump module between manifolds using only the feedforward of the control signal shown in Figure 8, without the negative feedback described above.

[0111] Furthermore, the high-capacity actuators 130A and 130E have different pressure responses compared to the other actuators due to the additional virtual manifold branches, virtual control valves, virtual control pressures, and virtual throttle orifices assigned to each actuator.

[0112] In this example, the pressure in the virtual hydraulic circuit is calculated and used to determine the flow rates of the first and second groups of pump modules by negative feedback, although the negative feedback signal may be calculated based on other calculated characteristics, such as the calculated virtual flow rate or the position or velocity of the virtual actuator's movement.

[0113] Furthermore, in a given example, the fluid flow rate of each manifold is determined by an effective simulation of the characteristics of the virtual hydraulic circuit section, although the controller may calculate the fluid flow rate using an alternative algorithm, and in any case, the calculated feedback signal may be further modified as needed, for example, by filtering to introduce smoothing. The characteristics of the simulated components may vary permanently or in different operating modes (for example, to provide user options), for example, the virtual control valve opening section may be increased to increase sensitivity to load pressure and reduce pressure drop in the system, which has the effect of each control joystick having a larger deadband.

[0114] In these examples, the pump module functions as a pump, delivering fluid to the actuator. However, the present invention is also operable when the working chamber is controlled as a motor receiving fluid from the actuator. Thus, the pump module can be an operable pump and motor in alternative operating modes. This facilitates energy recovery from the hydraulic fluid returned by the actuator.

Claims

1. A hydraulic device comprising: a controller; a prime mover; a hydraulic machine having a rotatable shaft drivingly engaged with the prime mover and including a plurality of working chambers having a volume that varies periodically with the rotation of the rotatable shaft, wherein the net displacement of one or more plural groups of the working chambers is independently variable under the control of the controller; a plurality of hydraulic actuators; and a hydraulic circuit extending between the plurality of working chambers and the plurality of hydraulic actuators, wherein the hydraulic circuit includes a first manifold extending between a first group of one or more working chambers and a first group of one or more actuators, a first plurality of actuator valves controllable to regulate the flow rate of hydraulic fluid from the first group of one or more working chambers to the first group of one or more actuators, a second manifold extending between a different second group of one or more working chambers and a second group of one or more actuators, and a second plurality of actuator valves controllable to regulate the flow rate of hydraulic fluid from the second group of one or more working chambers to the second group of one or more actuators; one or more of the working chambers are switchable between being part of the first group and connected to the first manifold and being part of the second group and connected to the second manifold by one or more gang valves; the flow rate of hydraulic fluid flowing into or out of the first and second manifolds from the first and second groups of working chambers is independently variable by independent control of the first and second groups of one or more working chambers under the control of the controller, whereby the pressures in the first and second manifolds can be independently varied; the first and second pluralities of actuator valves have positions controllable in response to a command to thereby regulate the flow rate of fluid from the first and second manifolds to the actuators. The controller independently controls the net displacement of the first and second groups of the one or more working chambers, and in response to the command, independently varies the flow rate to or from the first and second manifolds, thereby adjusting the response of the actuator to the command. The controller is configured to control the flow to or from the first manifold in response to the calculated pressure or flow rate at a control point within a virtual fluid flow path extending from the first manifold through one or more virtual valves that adjust a virtual fluid flow according to the position of the actuator valve. The hydraulic device is configured to control the flow to or from the first manifold in response to the calculated pressure or flow rate at each control point of a plurality of virtual fluid flow paths extending from the first manifold through one or more different virtual valves that divert the virtual fluid flow corresponding to the position of each actuator valve to a lower pressure region through each throttle aperture. **Claim 2** The hydraulic device according to claim 1, wherein the controller controls the flow to or from the first manifold in response to a feedback signal calculated based on virtual characteristics within a virtual hydraulic circuit including one or more virtual valves extending from the first manifold and whose position varies according to the position of the actuator valve that responds to the command, thereby controlling the flow of hydraulic fluid to or from the actuator through the actuator valve. **Claim 3** The hydraulic device according to claim 1, wherein two or more virtual valves are treated as if they were connected in series in a virtual fluid flow path, while the corresponding actuator valves are connected in parallel to the first manifold. **Claim 4** The hydraulic device according to claim 1, wherein there are a plurality of virtual fluid flow paths extending in parallel from the first manifold and having one or more different virtual control valves therein, and the calculated pressure or flow rate in each of the plurality of flow paths is considered when determining the flow rate from the first group of working chambers to the first manifold. **Claim 5** The hydraulic device according to claim 1, wherein the interface provides an output that varies in response to the input pressure of the first manifold and / or the second manifold.

6. The hydraulic device according to claim 5, wherein the controller causes the actuator to respond to a command via the interface so that the manifold controls the flow to or from the first manifold as if the manifold had an open outlet through which the working fluid flows into a low-pressure region during use.

7. The hydraulic device according to claim 1, configured to selectively direct or receive a majority of the fluid flow to or from a single actuator connected only to the first manifold, or from a single actuator, through at least one actuator valve, from or to the plurality of groups of working chambers.

8. The hydraulic device according to claim 7, configured such that a change in pressure within the first manifold varies less for a given change in flow rate to the second actuator than to the first actuator.

9. The hydraulic device according to claim 1, wherein a plurality of first actuator valves are connected in parallel to provide independently controllable parallel paths for fluid flow from the first group of working chambers to the actuator.

10. The hydraulic device according to claim 1, wherein the first group of working chambers is controlled to regulate the flow to or from the first manifold to cause a fluid flow rate to the first actuator and / or to cause a flow to or from the first manifold, and the first group responds as if the first manifold had a throttle aperture for hydraulic fluid, where the throttle aperture does not actually exist.

11. When the demand of the controller for the fluid flow of the first group of actuators exceeds the maximum fluid flow rate that can be provided at that time by the group of the working chambers, by default, some of the working chambers are connected to the first manifold, some of the working chambers are connected to the second manifold, and additional working chambers are configured to be connected to the first manifold. The hydraulic device according to claim 1.

12. The hydraulic device according to claim 1, wherein the controller further independently controls the displacements of the first and second groups of the working chambers in response to the command to implement damping of the movement of the actuator.

13. A method of controlling a hydraulic device according to any one of claims 1 to 12, the method comprising controlling the net displacements of the first and second groups of the working chambers to independently vary the flow to or from the first and second manifolds in response to a command through an interface.

14. The method according to claim 13, wherein the flow to or from the first manifold is adjusted to actively damp one or more vibrations of the first group of actuators.

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