Abstract: A method is for controlling an actuation force exerted by an actuating device having a first working chamber and a second working chamber supplied with pressurized air from a source of pressurized air by a first pressure regulator and a second pressure regulator. The method includes calculating, by an optimization algorithm based on a dynamic model of the actuating device and of the first and second pressure regulators, desired values for control signals for the first and second pressure regulators to generate an actuation force equal to a desired value for the actuation force. An estimated value for the actuation force, estimated values for pressures inside the first and second working chambers and for first derivatives of the pressures, are determined by a state observer based on a measured value for the actuation force and on measured values for the pressures in the first and second working chambers.

Abstract: A shovel includes a lower traveling structure, an upper swing structure swingably mounted on the lower traveling structure, a work attachment attached to the upper swing structure and including a boom, an arm attached to the boom, and an end attachment attached to the arm, a first obtaining device configured to obtain data on the pose state of the work attachment, and a second obtaining device configured to obtain data on the pose state of the lower traveling structure or the upper swing structure. Predetermined control related to the movement of the work attachment is executed based on the data obtained by the first and second obtaining devices. Information on the type of the end attachment is obtained, and a response characteristic of the work attachment or the details of an operation for the work attachment during the predetermined control are corrected based on the obtained information.

Abstract: A shovel includes a lower traveling structure, an upper swing structure mounted on the lower traveling structure, an engine mounted on the upper swing structure, a hydraulic pump configured to be driven by the engine, a hydraulic actuator, an operating device configured to operate the hydraulic actuator, and a hardware processor configured to control the discharge quantity of the hydraulic pump through negative control and change a control characteristic of the negative control according to the details of an operation on the operating device.

Abstract: An electric driven hydraulic fracking system is disclosed. A pump configuration includes the single VFD, the single shaft electric motor, and the single hydraulic pump mounted on the single pump trailer. A controller associated with the single VFD and is mounted on the single pump trailer. The controller monitors operation parameters associated with an operation of the electric driven hydraulic fracking system as each component of the electric driven hydraulic fracking system operates to determine whether the operation parameters deviate beyond a corresponding operation parameter threshold. Each of the operation parameters provides an indicator as to an operation status of a corresponding component of the electric driven hydraulic fracking system. The controller initiates corrected actions when each operation parameter deviates beyond the corresponding operation threshold.

Abstract: A variable displacement pump device includes a pump, a mover, a biasing member, first and second control chambers, and a controller. The first and second control chambers are provided between an inner periphery of a containing chamber of a housing and an outer periphery of the mover. Hydraulic oil is introduced from a discharge port into the first control chamber. The pump is configured to permit oil to be introduced from the discharge port into the second control chamber via a supply/discharge passage or to be discharged from inside the second control chamber. The second control chamber is located adjacent to any of the pump chambers in a discharge region or the discharge port via the mover. The controller is configured to switch states in which the second control chamber is opened and closed to the supply/discharge passage.

Abstract: A control device of a loading machine includes an adjustment determination unit and an operation signal output unit. The loading machine includes a swing motor and a swing body. The adjustment determination unit determines whether or not an angle formed by an azimuth direction of a swing body when the swing body stops and a target stop azimuth direction is less than an allowable angle based on an azimuth direction, a swing speed, and the target stop azimuth direction of the swing body during braking of the swing motor. The operation signal output unit outputs a swing control signal for driving the swing motor in a case in which it is determined that the angle formed by the azimuth direction of the swing body when the swing body stops and the target stop azimuth direction is equal to or greater than the allowable angle.

Abstract: To provide a construction machine that can highly precisely control branch flows from a hydraulic pump to a plurality of hydraulic actuators without being affected by load conditions. A controller (100) has a meter-out valve control section (140) configured to calculate a target opening area of a second meter-out valve (65a) (65b) according to a pressure difference between a supply pressure and a second meter-in pressure, or calculate a target opening area of a first meter-out valve (55a) (55b) according to a pressure difference between the supply pressure and the first meter-in pressure.

Abstract: System and methods for a DC powered hydraulic system capable of providing control over pressurized hydraulic fluid delivered to directional valves without the need for a PTO and/or a proportional valve. The hydraulic system controls the output from a battery to a direct current hydraulic pump.

Abstract: To achieve the improvement of recovery efficiency from a rod end oil chamber to a head end oil chamber during extending operation of a stick cylinder, and at the same time, to prevent an operation speed of the stick cylinder from being impaired when recovery is impossible, as well as to achieve the reduction of the number of parts, in a construction machine equipped with a stick. It is configured such that a first region Y1 at which a discharge valve passage 14g is opened while being throttled and a second region Y2 at which the discharge valve passage 14g is wider opened than at the first region Y1 are provided, in an operating position of a stick control valve 14 during extending operation of the stick cylinder, and if recovery from the rod end oil chamber 9b to the head end oil chamber 9a during extending operation of the stick cylinder 9 is possible, the stick control valve 14 is caused to be positioned at the first region Y1, and if the recovery is impossible, positioned at the region Y2.

Abstract: A construction machine is provided. If the rotational speed of a prime mover is set lower than a rated rotational speed and the delivery rate of a hydraulic pump is lowered, the construction machine can prevent deterioration of the operability in slow speed operation works by keeping wide a lever operation range in which the rate of flow supplied to a hydraulic actuator is variable.

Abstract: A laying die, for picking up and laying of substrates, comprising an elastically deformable substrate receiving structure providing an engagement surface for releasable receiving of substrates, an attaching element comprising a gas channel for providing positively or negatively pressurized gas for picking up and blowing off the substrates, and a carrier body made from elastically deformable material and sandwiched between the substrate receiving structure and the attaching element which is arranged to distribute the positively or negatively pressurized gas over the carrier body. The carrier body comprises breakthroughs to transfer the pressurized gas from the attaching element to the substrate receiving structure that comprises an elastically deformable distribution plate to distribute the positively or negatively pressurized gas over the engagement surface.

Abstract: A hydraulic work machine is provided which can improve the finishing accuracy in a horizontally leveling work, a slope face shaping work and so forth by preventing sudden acceleration of an arm when the excavation load decreases suddenly. The hydraulic work machine includes an arm velocity-control valve device 22 capable of adjusting a meter-out opening of the arm cylinder independently of a first arm directional control valve 23. A controller 100 is configured to control, when correcting and increasing an operation amount instructed by the first arm directional control valve, the arm velocity-control valve device to decrease the meter-out opening of the arm cylinder in response to the increase of load pressure of the arm cylinder.

Abstract: Apparatuses, systems and methods are provided for controlling at least one fluid actuated device; e.g., an actuator such as a hydraulic cylinder. A method is provided, for example, involving an actuatable component and an actuation system, which includes an actuation system component and an actuator. During a mode of operation, the actuation system component is fluidly coupled with a first chamber and a second chamber of the actuator using the actuation system. The actuator is operable to move the actuatable component.

Abstract: The present invention discloses a control system and method for injection molding machine. The control method comprises the following steps: establishing a work command according to a plurality of production process parameters; receiving a position information directly from an injection molding machine; and controlling a servo pump to drive the injection molding machine according to the position information and the work command.

Abstract: A servo pump control system (100) and a corresponding servo pump control method are disclosed. The servo pump control system (100) comprises a pressure controller (101) configured to receive a first control signal, and directly or indirectly provide a second control signal to the electric motor; and the pressure controller (101) configured to automatically commission at least one parameter without any manual adjustment.

Abstract: Controlling a functional system of a materials handling vehicle includes monitoring a current delivered by an energy storage system for powering the functional system, wherein the energy storage system may include at least one of a battery and a fuel cell. When the current delivered by the energy storage system exceeds a first predetermined amount, performance of the functional system is reduced from a first operating level to a second operating level for at least one task of the functional system to attempt to reduce the current delivered by the energy storage system.

Abstract: A hydraulic system that includes a rotating group with a plurality of fluid chambers and a plurality of valve sets that valve a corresponding one of the fluid chambers is disclosed. The hydraulic system may function as a hydraulic transformer. The hydraulic system may transfer energy between a high pressure fluid supply (e.g., from a pump), an accumulator, a hydraulic component (e.g., a hydraulic cylinder, a hydraulic motor, and/or a hydraulic pump-motor), and/or an input/output shaft. The hydraulic system may include a single rotating group with a common axis. Each of the valve sets may include a first valve that fluidly connects to the pump, a second valve that fluidly connects to a tank, a third valve that fluidly connects to the accumulator, and a fourth valve that fluidly connects to the hydraulic component. The valves may have a valving period set to less than half or one-third of a rotational period of the rotating group.

Abstract: A hydraulic jack includes an oil cylinder, an oil tank, and an oil storage barrel. The oil storage barrel includes a front portion and a back portion which are opposite to each other; an oil outlet of the oil cylinder is connected with an oil inlet at the front portion of the oil storage barrel by means of an oil inlet pipe; and an oil inlet of the oil tank is connected with an oil outlet at the front portion of the oil storage barrel by means of an oil outlet pipe, the oil inlet pipe and the oil outlet pipe are provided with switching valves for alternatively turning on the oil inlet pipe and the oil outlet pipe. A partition plate that is capable of moving along a barrel wall and an elastic telescoping member are provided inside the oil storage barrel.

Abstract: Provided is a hydraulic drive apparatus for working machine capable of preventing an excessive pressure drop on a meter-in side and moving a load in a lowering direction at a stable speed requiring no counter balance valve, including a hydraulic pump, a first hydraulic actuator lowering a first load, an operating device, a first hydraulic circuit including meter-in and meter-out flow passages, a control valve, a meter-in-flow-rate controller, a meter-out-flow-rate controller making a meter-out flow rate not lower than a meter-in flow rate, a second hydraulic actuator, a second hydraulic circuit between the first hydraulic circuit and a tank and for the second hydraulic actuator, a back pressure valve between the second hydraulic circuit and the tank, a regeneration line leading a part of hydraulic fluid from between the second hydraulic circuit and the back pressure valve to the meter-in flow passage, and a check valve in the regeneration line.

Abstract: Hydraulic actuation systems having variable displacements and energy recovery capabilities include cylinders with pistons disposed inside of barrels. When operating in energy consuming modes, high speed valves pressurize extension chambers or retraction chambers to provide enough force to meet or counteract an opposite load force. When operating in energy recovery modes, high speed valves return a working fluid from extension chambers or retraction chambers, which are pressurized by a load, to an accumulator for later use.

Abstract: A device is disclosed that may include a spool valve having a first connector and a second connector and a spool movable for controlling flow between the first connector and the second connector, regardless of direction of flow through the spool valve. A pilot valve having an inlet and an outlet develops a command pressure. A feedback circuit having an inlet and an outlet develops a feedback pressure. The spool valve may be responsive to the command pressure and the feedback pressure. A fluid rectifier circuit is provided to connect the higher pressure of the first connector and second connector to the pilot valve inlet and feedback circuit inlet, and connect the other of the first connector and second connector to the pilot valve outlet and feedback circuit outlet.

Abstract: The present invention relates to a stand-alone therapeutical training device which is peculiar in that the stand-alone therapeutical training device comprising a shallow housing having at least a top surface and a bottom surface, said housing comprising at least one force sensor, said force sensor measuring the force applied to said top surface of said housing and generating a response signal, at least one user feedback unit, a controller placed inside said housing configured for controlling said user feedback unit and that the controller controls the user feedback unit proportionally to said response signal from said force sensor. Hereby can be archived a simple stand-alone therapeutically training device enabling the patient and/or the physiotherapist to evaluate the force or weight applied by the user on the upper surface of the device.

Abstract: A system and method to recapture energy of a hydraulic motor is disclosed. The system includes a plurality of pistons disposed about a periphery of a flywheel, wherein each piston is compressed by a roller during each revolution of the flywheel. As each piston is engaged and pushes against the roller, the piston is biased inward and forces hydraulic fluid out of the cylinder recapturing energy as pressure to the system when the flywheel is rotating under its own rotational inertia. In addition, the piston pushing against the roller causes the flywheel to continue to rotate. As the force acting on the piston causes the flywheel to rotate, the next piston starts to approach the position of the prior piston. This action continues as long as the fluid is under pressure when it enters each cylinder.

Abstract: The present disclosure provides embodiments directed towards a system for the control of hydraulic output by a hydraulic power source. In one embodiment, a system is provided. The system includes a hydraulic supply system having a drive, a hydraulic pump coupled to the drive, a first hydraulic output configured to supply a first flow of a hydraulic fluid from the hydraulic pump to a hydraulic lift, a second hydraulic output configured to supply a second flow of the hydraulic fluid from the hydraulic pump to a first hydraulic tool, and a controller configured to adjust a speed of the drive in response to a feedback indicative of a first load by the hydraulic lift, a second load by the first hydraulic tool, or a combination thereof.

Abstract: A method for predefining a rotational speed of a drive machine of a drive system is disclosed. The method involves at least the drive machine and a hydrostatic drive unit, wherein the rotational speed which is to be predefined for the drive machine is determined as a function of an instantaneous system state and a predicted system state of the drive system.

Abstract: A system is provided in which a control module may include a user interface configurable to receive input and display hydraulic control settings, wherein the hydraulic control settings include at least a hydraulic pressure setting and a hydraulic flow setting. The control module may also include a processor executable to convert the hydraulic control settings to corresponding electrical currents, wherein the electrical currents correspond to at least the hydraulic pressure setting and the hydraulic flow setting. The control module may also include one or more communication interfaces coupled to the processor configurable to output the electrical currents to the hydraulic circuit to control hydraulics that operate one or more attachments of a machine.

Abstract: The present disclosure is directed toward a hydraulic control system. The system may have a pump and a tool actuator configured to move a tool with a flow of pressurized fluid provided by the pump. The system may further have a tool control valve configured to control the flow of pressurized fluid to the tool actuator. The system may also have a controller operably connected with the tool control valve and the pump. The controller may be configured to receive a tool movement request. The controller may further be configured to estimate a change in a flow demand across the tool control valve associated with the tool movement request. The controller may also be configured to command adjustment of a discharge flow rate of the pump based on the estimated change in flow demand to satisfy the tool movement request.

Abstract: There are provided: control valves 22-24 that control flow of pressure oil from the hydraulic source 21 to the hydraulic actuators 15-17; electric lever devices 51-53 that output electrical operation signals, which are drive instructions for the hydraulic actuators 15-17, in correspondence to lever operation; and a control unit 25-30 and 50 that controls the control valves 22-24 in correspondence to the operation signals. When the determination unit determines that an operation signal is not within the normal range, the hydraulic actuators 15-17 are allowed to be driven with flow of pressure oil to the hydraulic actuators 15-17 limited more significantly than in a case where it is decided that an operation signal is within the normal range.

Abstract: A large hydraulic excavator permits an easy change from a machine mode corresponding to a backhoe excavator to a machine mode corresponding to a loader excavator, and vice versa. A hydraulic circuit is provided with hydraulic pumps and directional control valves, solenoid valves for controlling the hydraulic pumps and the directional control valves, and a controller for controlling the solenoid valves in accordance with operation of control lever devices and control pedal devices. The controller performs its control in a backhoe mode or loader mode selectively instructed by a mode instruction unit. Control of the solenoid valves in the backhoe mode makes the hydraulic circuit function as a backhoe hydraulic drive circuit, while control in the loader mode makes the hydraulic circuit function as a loader hydraulic drive circuit.

Abstract: In a method for controlling a valve system controlling an actuator, the first direction of motion of the actuator is controlled solely by the first and the second valve series; or, its second direction of motion is controlled solely by the third and the fourth valve series; and an error caused by a fault situation in the control of the actuator is compensated for by using, for the control of the first direction of motion, also the third valve series, the fourth valve series, or both of them; or, an error in the control of the actuator caused by a fault situation is compensated for by using, for the control of the second direction of motion, also the first valve series, the second valve series, or both of them.

Abstract: A system for lubricating transmission components with hydraulic fluid includes a pump and a motor coupled to the pump. The pump has an inlet port that receives hydraulic fluid and an outlet port from which hydraulic fluid is pumped to the transmission components. A pump pressure is regulated by adjusting a motor torque of the motor, and the motor torque is set by commands based on a look-up table or a formula.

Abstract: A hydraulic system includes a hydrostatic piston machine having a plurality of valves that can be actuated using an actuator depending on the motion of the pistons and a control unit for activating the actuators. The switching points at which the valves are actuated are dependent on operating conditions, so that the expected functionality and the essential properties of the hydrostatic piston machine are ensured under different operating conditions.

Abstract: The operating system for a construction machine gives advice on efficient operation to an operator. A specified state value relating to the operational condition of the construction machine, for example, the hydraulic oil pressure or engine speed, is detected (S101), and the frequency distribution of the state value in prescribed time intervals is calculated (S102). The variable range of the state value is classified into plural regions beforehand, and different target values are pre-set for each these regions. For each region, the frequency distribution is compared with the target value (S104, 106, 108, 110, 112), and as a result of the comparison, a applicable message is selected from the prescribed messages and output (S105, 107, 109, 111, 113). The output message may also be selected according to the combination of the comparison results for the plural state values such as the hydraulic oil pressure and engine speed.

Abstract: A programmable cylinder, a system and a method change a velocity of a machine element within a compartment. A light detector within the compartment determines that the machine element is located at a first position or at a second position and/or is moving at a first velocity or at a second velocity. Switches determine that the machine element may be located at the first position or at the second position and/or is moving at the first velocity or at the second velocity. A microprocessor transmits a control signal to a transducer to alter an electrical current of the transducer to move valves of the compartment between an open position and a closed position. A compressed fluid within the interior of the compartment is changed via the valves. The machine element is accelerated and/or is decelerated to the first velocity or to the second velocity via the compressed fluid.

Abstract: A hydraulic system is disclosed having at least two hydraulic circuits. The disclosed system compares pressures between the hydraulic circuits and alters valve commands of the circuit associated with higher pressures in order to reduce overall system pressure.

Abstract: A machine, such as a backhoe, has a series of components connected in series and moved by separate hydraulic actuators. A position estimator determines the present position of each component from the load acting on the associated hydraulic actuator and a velocity command for the component. For each component, a function parameter estimator uses the present positions of the components to derive a set of parameters that include a static structure load that the components exert on the associated hydraulic actuator, acceleration and deceleration limits for both directions of component motion, and a control bandwidth for the associated hydraulic actuator. The set of parameters for a given component is used to control the associated hydraulic actuator.

Abstract: In a hydraulic driving device for an operating machine, when an output value of an operating device is in a first predetermined range, a pump is stopped and each of an open and closed valve and a hydraulic control valve is closed. When the output value goes beyond the first predetermined range, the pump is started and the open and closed valve is opened. When the output value goes beyond a second range greater than the first predetermined range, the hydraulic control valve is opened to supply a hydraulic fluid to an actuator.

Abstract: A control device for a construction machine according to the present invention is configured so that in the construction machine provided with an automatic stop function which automatically stops an engine by an engine controller upon a predetermined automatic stop condition being met, and a hydraulic lock function which sets a hydraulic actuator locked in an inactive state by a hydraulic lock controller, there is provided a restart switch, where after an automatic stop of the engine, when the restart switch is operated, a restart command is transmitted to the engine controller via a route independently of that of an engine switch and independently of a hydraulic unlock condition, and the engine is restarted.

Abstract: A system and process for controlling propulsion and steering of a track trencher excavation machine powered by an engine includes a multiple mode propulsion and steering control system that performs a plurality of functions depending on a selection of one of a plurality of operational modes. A controller generates a vehicle propulsion hydrostatic drive signal optionally using a track drive hydraulic pressure or a track drive speed as a variable for modifying the propulsion drive signal. The controller optionally uses a hydraulic attachment drive pressure as a variable for further modifying the propulsion drive signal.

Abstract: A control system for a work machine having a plurality of removably attachable work tools is disclosed. The control system has a tool recognition device configured to generate a recognition signal corresponding to each of the removably attachable work tools, and at least one fluid actuator configured to move at least one of the plurality of removably attachable work tools. The control system also has at least one fluid sensor configured to generate a load signal and at least one operator interface device configured to generate a desired velocity signal. The control system further has a controller in communication with the tool recognition device, the at least one fluid actuator, the at least one fluid sensor, and the at least one input device. The controller is configured to command a velocity for the fluid actuator in response to the recognition signal, the load signal, and the desired velocity signal.

Abstract: A control apparatus is provided for a hydrostatic transmission to simulate a gear drive on a tractor. The hydrostatic transmission has a swashplate that is angularly movable to a plurality of positions, and a proportional valve that provides a control pressure to a servo piston to control the hydrostatic transmission swashplate position. A transmission control lever may be moved to a plurality of positions, each position providing a different voltage signal to a microcontroller. The microcontroller receives and converts a voltage signal to a coil current to actuate the proportional valve.

Abstract: A priority flow rate control valve (30) distributes pressurized working oil discharged from a hydraulic pump (10) driven by an electric motor (11) to a power steering device (20) first, and distributes the residual pressurized working oil to a cargo handling device (19). The rotation speed of the electric motor (11) and the distribution ratio of the pressurized working oil of the priority flow rate control valve (30) vary depending on the operation states of these devices (19, 20). By decreasing the rotation speed of the electric motor (11) at a rate smaller than a normal decrease rate when the cargo handling device (2) stops operation in a state where the power steering device (20) and the cargo handling device (19) are in operation, a kickback in a steering wheel (7) due to a response delay of the priority flow rate control valve (30) can be prevented.

Abstract: An apparatus and method for controlling a work tool on a work machine are provided. The work machine may have first and second actuators, each actuator being operable in a vibratory mode and a non-vibratory mode, and each actuator being coupled to the work tool for changing the position of the work tool. The method may include simultaneously (i) operating the first actuator in a vibratory mode, (ii) operating the second actuator in a vibratory mode, and (iii) receiving a command to change the position of the work tool. The method may further include operating the first actuator in a non-vibratory mode to change the position of the work tool while operating the second actuator in a vibratory mode to vibrate the work tool, in response to receiving the command.

Abstract: A distributed hydraulic system having a plurality of hydraulic functions each including a hydraulic actuator, a valve assembly that controls flow of fluid to the hydraulic actuator, and a function controller which operates the valve assembly. The function controllers exchange messages over a communication network which has a finite bandwidth. Access to the network is controlled by determining which function controllers govern high priority operations and allowing those function controllers to send messages as often as once every first interval of time. The other function controllers are limited to sending messages no more often than once every second interval of time, which is longer than the first interval of time.

Abstract: A method for controlling an air cylinder such that air is supplied to and exhausted from pressure chambers of the air cylinder by air servo valves. Pressures in the pressure chambers are detected by pressure sensors, signals of the detected pressures are feedback to a controller, and the degrees of opening of the air servo valves are adjusted by corresponding PID adjusters of the controller on the basis of the respective differences between instruction values and detection values. The displacement of the rod of the air cylinder is detected by a displacement sensor, and a detection signal of the displacement is fed back to the controller so that a gain of the PID adjuster is always changed in accordance with the detection signal of the displacement.

Abstract: A distributed hydraulic system having a plurality of hydraulic functions each including a hydraulic actuator, a valve assembly that controls flow of fluid to the hydraulic actuator, and a function controller which operates the valve assembly. The function controllers exchange messages over a communication network which has a finite bandwidth. Access to the network is controlled by determining which function controllers govern high priority operations and allowing those function controllers to send messages as often as once every first interval of time. The other function controllers are limited to sending messages no more often than once every second interval of time, which is longer than the first interval of time.

Abstract: A steering speed-computing section (81) to differentiate a steering angle of a steering wheel from a steering angle sensor (18) to compute the steering speed signal, a low-pass filter (82) to cut high frequency components in the steering speed signal to output a correction steering speed signal, a switching section (87) to switch the cut-off frequency in the low-pass filter to be higher at the time of determining a high-speed steering condition, and a flow quantity-computing section (85) to compute a target flow quantity supplied to a power steering output section (8) based on the steering angle signal and the correction steering speed signal are provided to control a flow quantity of an operating oil supplied to the power steering output section (8) for the target flow quantity.

Abstract: An electro-hydraulic assembly for use in underground mining is disclosed. The assembly includes a hydraulic component, such as a valve block for an underground self-advancing roof support, as well as actuators and/or sensors which have a housing and can be connected or are connected via a data-transmission system to a control unit. A function (e.g. withdrawing the support, setting, advancing, or the like) can be activated at the hydraulic component by each actuator, and/or a hydraulic state associated with a measuring point of the hydraulic component or another measured variable associated with the self-advancing roof support can be measured by each sensor. A reader unit is associated with each actuator and/or sensor in its respective housing, and an information element or transponder is associated with the hydraulic component for each function, each control valve, or each measuring point.

Abstract: The invention relates to a method for controlling a pressure supply device in a hydraulic circuit, especially in a hydraulic circuit in an automatic gearbox which comprises an hydraulic pump, a pressure control valve and a consumer. The hydraulic pump is controlled if the system pressure falls below a specific lower threshold value and is switched off if a specific higher threshold value of the system pressure is reached or exceeded. In the data on the system pressure is not available, the current system pressure is calculated.

Abstract: A hydraulic circuit branch includes a hydraulic actuator, such as a cylinder, and an assembly of one or more electrohydraulic proportional valves connected in series between a pressurized fluid supply line and a tank return line. The force acting on the hydraulic actuator is determined by sensing fluid pressures produced by the hydraulic actuator. Pressures in the supply and tank return lines also are sensed. The sensed pressures and a desired velocity for the hydraulic actuator are employed to determine an equivalent flow coefficient, which characterizes fluid flow through the hydraulic circuit branch, either a conduction or restriction coefficient may be derived. The equivalent flow coefficient is used to determine how to activate each electrohydraulic proportional valve to achieve the desired velocity of the hydraulic actuator. The equivalent flow coefficient also is employed to control the pressure levels in the supply and tank return lines.