Abstract: A pressure cylinder is connected to an air pressure source through a servo valve, the servo valve is controlled as an on/off switching valve by a control section in an advancing working step of a piston rod, and at the time of backward stroke of the piston rod, an operation position of the piston rod is detected by a position detector to feedback a detection signal to the control section, the servo valve is controlled by the control section such that a deviation between the operation position and a preset stopping position is eliminated, the piston rod is stopped at an intermediate stopping position, and a state in which substantially the same pressures are supplied to pressure chambers formed on opposite sides of the piston is maintained.

Abstract: The invention includes a moving step of moving a piston to a target position by supplying and discharging compressed air to and from pressure chambers on opposite sides of the piston of a pressure cylinder by driving servo valves by a controller, a clamping step of allowing a pressure member at a tip end of a piston rod to touch a workpiece softly in this target position, and a pressing force applying step of pressing the workpiece with the pressure member in a required force.

Abstract: A fluid power operate linear drive possessing a slab housing (2) with an elongated cross sectional outline, in which a plurality of receiving spaces (8) are arranged extending in a common housing plane adjacent to each other in the direction of the longitudinal axis (3) of the cross section. At one first narrow side (21) of the housing there is a piston receiving space (12) extending in the longitudinal direction containing a piston (13) connected with an outwardly running force output part (16). At the opposite second narrow housing side (22) there is an electronic circuitry receiving space (23) containing electronic valve control circuitry (24). Between the piston receiving space (12) and the electronic circuitry receiving space (23) there is at least one valve receiving space (26), which contains a control valve means (25), which is able to be electronically operated and serves for the control of fluid actuation of the piston (13).

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.

Abstract: A method is provided for controlling hydraulic flow to a hydraulic actuator. The method includes generating a command signal based on an operator input, sensing a linkage position associated with the hydraulic actuator, and selecting a moving rate of a valve associated with the hydraulic actuator based on the sensed linkage position and the command signal. The valve is modulated to control the hydraulic flow to the hydraulic actuator based on the selected moving rate.

Abstract: Disclosed is a piston positioning system for positioning a piston within a cylinder of a pneumatic circuit. The system comprises a piston position indicator for sensing an actual piston position, a controller for generating an output signal in response to the piston position signal, a pneumatic valving device for regulating the flow of pneumatic fluid and a solenoid valve configured to energize the pneumatic valving device. The pneumatic valving device comprises a four-way valve, a servo valve coupled to a stepper motor, and a two-way valve. The reversible stepper motor is incrementally rotatable over a desired angle of rotation in proportion to the magnitude of the output signal for linearly translating the servo valve such that the flow of pneumatic fluid maybe manipulated into and out of first and second ends of the cylinder to control the piston position therewithin.

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.

Abstract: A method is provided for recovering energy in a hydraulic circuit. The hydraulic circuit includes a pump having a swashplate and being in fluid communication with a hydraulic actuator via a valve. The method includes sensing an overrunning load condition in the hydraulic circuit, actuating the valve to provide fluid from the hydraulic actuator to the pump under the overrunning load condition, and producing a torque output from the fluid provided to the pump. Also, a method is provided for recovering energy in a hydraulic circuit including a pump and a motor in fluid communication with a hydraulic actuator via a valve. The method includes sensing an overrunning load condition in the hydraulic circuit, actuating the valve to provide fluid from the hydraulic actuator to the motor under the overrunning load condition, and producing a torque output from the fluid provided to the motor.

Abstract: A method (90) for simulating a system having a mechanical subsystem and a hydraulic subsystem is presented. The method comprises the steps of: describing (92) the mechanical subsystem and the effect of the hydraulic subsystem thereupon by integrating a first differential equation system of an n-dimensional first variable using a first numerical method, resulting in a sequence of values for the first variable; and describing (94) the hydraulic subsystem and the effect of the mechanical subsystem thereupon by integrating a second differential equation system of an m-dimensional second variable using a second numerical method, resulting in a sequence of values for the second variable. A corresponding arrangement having a first integrator (1) and a second integrator (4) is also presented.

Abstract: A method for controlling a fluid system is provided. The system may include a hydraulic circuit having a pump driven by an engine, wherein the pump delivers fluid to an actuator through a valve assembly. The method may include receiving an operator input and determining a condition of the hydraulic circuit. The condition of the hydraulic circuit may include at least one of a flow rate of fluid to the actuator, an engine speed, and a pump displacement. The method may include determining a valve transform function as a function of a position of a linkage associated with the actuator and the condition of the hydraulic circuit. The method may further include determining a valve command in response to the valve transform function and the operator input, wherein the valve command results in a consistent deadband. The valve command is delivered to the valve assembly.

Abstract: A method and apparatus for operating a load lifting device to move a load and hold the load steady is disclosed. In the conventional arts, a lifted or lowered suspended load had a tendency to move from its desired position, as hydraulic fluid in the lifting system cooled, e.g. a stick slip condition. The present invention monitors a fluid pressure in the lifting system and compensates the fluid pressure to accommodate any pressure drop due to fluid cooling. Thereby, the load can be effectively held steady at a desired position, and the stick slip condition can be avoided.

Abstract: A control device for the position (x) of a valve slide (3), with a d.c. voltage (UB) operated set point transmitter (11), which produces a set point value (Uw) proportional to the position (w) of a control lever (10) and the operating d.c. voltage (UB), with an actual value transmitter (15) operated with the same d.c. voltage (UB) as the set point transmitter (11), which produces an actual value signal (Ux) proportional to the position (x) of the valve slide (3) and the operating d.c. voltage (UB), the proportionality factors (k1, k2) being equal to the dependence of the set point and actual value signals (Uw, Ux) on the position (x) of the valve slide (3) or the position (w) of the control lever (10), respectively, and on the operating d.c.

Abstract: A booster of the present invention is structured to include one permanent magnet (first permanent magnet) 40 provided in an input rod 20, and the other permanent magnet (second permanent magnet) 51 forming a repulsive magnetic field between the second permanent magnet 51 and the first permanent magnet 40, and to apply a force amplified by a force received by the second permanent magnet 51 to an output rod 60 through a channel different from an output applying channel by an output applying member 30 to booster the inputted force. The booster can boost a force by applying a force to operate an inputting member without requiring such a negative pressure source or a hydraulic pressure source operated by a separate driving force different from a driving force to drive the inputting member as the conventional booster requires.

Abstract: In the construction machinery equipped with an engine, a hydraulic control unit and a machine controller, there is provided an antitheft device for the construction machinery, which can prevent the engine from starting and the hydraulic control unit from working with reliability no matter how the starter circuit of the engine is modified. The initial state of the machine controller is so set that the fuel injection by a fuel injection unit of the engine is halted and that the operations of control units in the hydraulic control unit are halted, and an antitheft control unit is provided to release the initial state of the machine controller upon receiving a release signal from the antitheft control unit.

Abstract: A system and method for controlling at least one hydraulic actuator of a hydraulic system includes a flow rate measurement of a hydraulic fluid flow traveling into and out of a cavity of the hydraulic actuator. The flow rate is used to calculate piston information corresponding to a position, velocity, acceleration, and/or direction of movement of a piston of the hydraulic actuator. The piston information can then be provided to an output device to aid in the control of the hydraulic actuator. Alternatively, the piston information can be compared to a reference signal relating to a desired position, velocity, acceleration, and/or direction of movement of the piston to produce a control signal, which can be used to adjust the hydraulic fluid flow and provide the desired actuation of the piston.

Abstract: A pressure cylinder is connected to an air pressure source through a servo valve, the servo valve is controlled as an on/off switching valve by a control section in an advancing working step of a piston rod, and at the time of backward stroke of the piston rod, an operation position of the piston rod is detected by a position detector to feedback a detection signal to the control section, the servo valve is controlled by the control section such that a deviation between the operation position and a preset stopping position is eliminated, the piston rod is stopped at an intermediate stopping position, and a state in which substantially the same pressures are supplied to pressure chambers formed on opposite sides of the piston is maintained.

Abstract: A device for controlling a working arm of a working machine, which is capable of releasing the pressure of the actuation fluid confined in the actuation cylinder of the working arm device at a predetermined pressure lower than the set pressure and of controlling the opening/closing of the cylinder relief valve. The device comprises releasing means for a releasing a pressurized fluid feed/drain circuit of an actuation cylinder of a working arm device at a predetermined pressure lower than a set pressure of a cylinder relief valve provided for said feed/drain circuit and a control means for controlling the opening/closing of the releasing means.

Abstract: A device for hydraulic adjustment of rollers of strand guiding segments of a strand casting device has hydraulic cylinders which are separated by a piston with piston rod into a cylinder chamber and an annular cylinder chamber, respectively. The cylinder chambers can be connected by control members alternatingly and in opposite directions as well as simultaneously with a pressure source and a pressure sink, wherein on-off valves are provided as control members.

Abstract: A precision servo control system for a pneumatic actuator has a piston positionable over a stroke of the pneumatic actuator using a supply of pressurized gas. A brake and a sensor system are connected to the actuator and to the servo control system. The servo control system operates to initiate the forward thrust from the pressurized gas to move the piston along the stroke. When a braking point along the stroke is determined, the servo control system initiates a reverse thrust from the pressurized gas while maintaining the forward thrust and simultaneously begins to selectively apply the brake to stop the piston within a predetermined tolerance of a desired stopping position. The precision servo control system is easily programmable in a manner similar to that of a control system for electrical actuators. The precision servo control system can maintain the predetermined tolerance even under changing loads, long stroke lengths or vertically oriented stroke directions.

Abstract: In a free piston machine, initial collisions of the piston with structures at the end of the cylinder are detected and generate a change in the magnitude of a perturbation signal, which is applied to the summing junction of a closed loop feedback control system controlling a piston force. The change is applied in a direction to reduce piston amplitude. In embodiments in which maximization of piston amplitude is desirable, the magnitude of the perturbation signal is also varied in the opposite direction in the absence of collisions to increase piston amplitude of oscillation so that operation then hunts between initial nondestructive collisions and a non-colliding maximum amplitude of piston oscillation.

Abstract: A fluid power operated fluid power cylinder having a cylinder housing (2) on whose rear side a control system housing (33) is mounted. The control system housing (33) contains a valve means and furthermore a electronic valve circuitry and/or electronic control circuitry as control components for the operation of the fluid power cylinder. Externally on the control system housing (33) electrical connection means (63) are provided for the supply of electrical control signals and fluid connection means (48 for the supply of the operating fluid.

Abstract: The invention relates to a method for operating a positioner with a first input for an input variable W for prescribing a desired value, a second input for a controlled variable X, an output for a manipulated variable Y, and an actuator, which, dependent on the input variable W and the controlled variable X, generates an output signal for forming the manipulated variable Y, whereby the control method comprises detecting, during continuous monitoring, of an abnormal status of the signal representing the controlled variable X generating of an error signal that acts on a changeover unit. When an error signal of the error detection device is present, the method deactivates the actuator with respect to the signal of the positioner that represents the manipulated variable Y, and activates a controller by the changeover unit.

Abstract: In a free piston machine, initial collisions of the piston with structures at the end of the cylinder are detected and generate a change in the magnitude of a perturbation signal, which is applied to the summing junction of a closed loop feedback control system controlling a piston force. The change is applied in a direction to reduce piston amplitude. In embodiments in which maximization of piston amplitude is desirable, the magnitude of the perturbation signal is also varied in the opposite direction in the absence of collisions to increase piston amplitude of oscillation so that operation then hunts between initial nondestructive collisions and a non-colliding maximum amplitude of piston oscillation.

Abstract: A method and system for controlling fluid pressure in a hydraulically actuated device is provided, in which the device receives an input indicating the amount of work that the device is to perform, and the threshold pressure of a relief valve is adjusted so that the pressure of the fluid is appropriate for the amount of work indicated by the input. In one implementation, the device receives a user input representing the amount of work to be performed by the device. Based on the user input, a setting for a relief valve that is sufficient to maintain the fluid pressure at a level appropriate for the amount of work required is determined. An electrical signal is then sent to the relief valve to adjust it to the determined setting. Determining the proper setting for the relief valve may involve referencing a look-up table that maps user input values to electrical signal values.

Abstract: The control method according to the invention serves the purpose of generating a manipulated variable (y) for controlling a hydraulic drive (HA). In this case, account is taken of at least a desired value (vs) for the speed (vi) of the hydraulic drive (HA), a first parameter (K1), which simulates the response characteristic (KV, AO) of the hydraulic drive (HA), and a second parameter (K1), which simulates the internal resistance (KD, AK, AO) which the technical process (TP), opposes to the hydraulic drive (HA). It is advantageous that nonlinear dependencies of the hydraulic drive (HA) can be taken into account for generating the manipulated variable (y) driving the hydraulic drive (HA). It is advantageously possible in this case to dispense with a technically complicated sensor system.

Abstract: A protection device for controlling the motion of a pneumatic actuator, having at least one elongated cylinder provided with a piston, dividing the cylinder into a first chamber and a second chamber, an actuating pressure supply line connectable to at least one of the first and second chambers, a control unit for controlling the motion of the piston relatively to the cylinder, and a motion sensor adapted to sense a piston feature related to the piston motion and co-operating with the control unit. According to the invention, the control unit limits the motion of the piston as soon as signal from the sensor indicates that an excessive value of the piston motion has been established.

Abstract: An electro-hydraulic transducing valve (3a) and other elements associated with cylinder-controlling components, such as a control valve (3), are connected to the output end of a controller (23) adapted to perform control computation based on electric manipulation signals send from and electric joy stick (12a) or the like. Control valve return pressure (PT) and load-sensing pressure (PL) are detected by the first and second detectors (18), (19) so that start-up of a hydraulic cylinder (7) or the like is detected based on rise of the differential pressure (&Dgr;P) between the two types of pressures. The controller (23) is provided with a function generating unit (14a) and a calibration computing unit (20). The function generating unit (14a) has a reference function (F) that determines the relationship between electric manipulation signals and command values for commanding the electro-hydraulic transducing valve (3a) and other similar elements.

Abstract: A random work arranging device that arranges randomly conveyed works by using a robot and carries out the arranged works, wherein the robot comprises a plurality of arms and a single robot controller for controlling respective arms independently one another to arrange and transfer the works from a conveying position to a carry-out position.

Abstract: Provided is a force-controlled hydro-elastic actuator, including a hydraulic actuator, having a connection to hydraulic fluid and including a mechanical displacement member positioned to be mechanically displaced by fluid flow at the actuator. A valve is connected at the hydraulic actuator connection and has a port for input and output of fluid to and from the valve. At least one elastic element is provided in series with the mechanical displacement member of the hydraulic actuator and is positioned to deliver, to a load, force generated by the hydraulic actuator. A transducer is positioned to measure a physical parameter indicative of the force delivered by the elastic element and to generate a corresponding transducer signal. A force controller is connected between the transducer and the valve to control the valve, based on the transducer signal, for correspondingly actuating the hydraulic actuator and deflecting the elastic element.

Abstract: An apparatus controllably moves a moveable element within a hydraulic motor. A lever device establishes an operator command signal indicative of a desired velocity and direction of movement of the moveable element. A position sensor senses the position of the moveable element and produce a position signal. An electronic controller receives the operator command signal and position signal, determines the actual velocity of the moveable element, and determines a limit value in response to the actual velocity of the moveable element. Additionally, the controller compares the operator signal magnitude to the limit value and produces a flow control signal in response to the comparison. An electrohydraulic controller receives the flow control signal and responsively controls the movement of the moveable element.

Abstract: A controllable pneumatic actuator and motion control apparatus including a field responsive medium and control method therefor. The apparatus has a pneumatic actuator coupled to a rotary-acting brake such that a motion (e.g., a displacement, velocity or acceleration) of an output member may be precisely controlled. The pneumatic actuator has a housing with a piston moveable responsive to a pressure differentials and an output member coupled to the piston. The rotary-acting controllable brake includes a field responsive medium and a brake shaft coupled to the output member. Preferably, the apparatus includes a control system having a sensor for deriving motion signal and a motion control for processing the motion signal and providing a control signal to the brake.

Abstract: A speed control apparatus for a cylinder comprises the cylinder, speed controllers for controlling flow rates of a pressure fluid introduced into and discharged from cylinder chambers, a controller for outputting control signals to the speed controllers, and a sensor for detecting the displacement amount of a piston of the cylinder to transmit a detection signal to the controller. Each of the speed controllers includes a throttle section for controlling the flow rate of the pressure fluid flowing through the fluid passage, and a throttle amount control section for changing the throttle amount at the throttle section on the basis of the control signal transmitted from the controller.

Abstract: An automatic depth control system is disclosed. The system includes a Console and remote Controller mounted in the tractor cab, power beyond Valving, and Depth Sensors, either ground contact or non-ground contact, mounted on the frame of the implement. The depth sensing system is provided to sense the actual penetration of an implement tool by determining the height of the implement frame above the ground. A circuit system is provided to receive the depth signal and to signal power beyond valving that will effect hydraulic corrections in order to maintain the select depth penetration. The Console includes an instrument panel having a toggle switch with AUTO, LOCK and MANUAL positions, an LED showing depth of tool penetration and a bargraph depicting variations from a desired depth and flashing lights on the bargraph to show depth corrections in process. The Console also includes a depth window in which no hydraulic correction would be made, a sensitivity switch, depth sensor switches and an UP/REPHASE switch.

Abstract: In a free piston machine, a coil is mounted to its housing and magnetically linked to a permanent magnet or electromagnet on its piston member to form a linear motor. The coil and magnet are either added to embody the invention or are part of an AC linear alternator or AC linear motor which are a part of the free piston machine. A source of DC electrical current and a switch for connecting the DC source to the coil supply DC current to the coil when the switch is closed so that the coil and magnet temporarily operate as a DC linear motor until the piston is adequately centered for start-up without collision. The DC source voltage is temporarily applied to the coil to move the piston away from an end wall of the cylinder. This is accomplished by applying the DC current to the coil for a predetermined time interval, or by sensing when the piston has reached an adequately centered position.

Abstract: An apparatus for controllably moving a work implement of an earth moving machine is disclosed. The work implement includes a boom and a bucket being attached thereto where the boom is actuated by a hydraulic lift cylinder and the bucket is actuated by a hydraulic tilt cylinder. An operator controlled joystick produces an operator command signal for controlling the movement of the work implement. Implement position sensors sense the elevational position of the boom and the pivotal position of the bucket, and responsively produce respective implement position signals. A controller receives the implement position and operator command signals, determines the instant position of the work implement, reduces the operator command signal as the boom is being raised and the bucket is being pivoted, and produces an electrical valve signal based on the reduced operator command signal.

Abstract: A system for determining the extended length or orientation of a hydraulic actuator, or of an implement or joint, is disclosed herein. Electromagnetic (EM) bursts such as ultra-wideband or frequency pulses are generated and applied to a transmitter unit attached to a stationary or moveable portion of the actuator. The EM bursts are launched by the transmitter toward a receiver located on the other of the stationary or moveable portion of the actuator. The time for the EM bursts to travel between the associated antennas of the transmitter and the receiver is determined and converted into a position signal representing the distance therebetween.

Abstract: This disclosure is directed to novel systems and methods for producing motion in response to a drive signal where the motion has a smooth translational reversal. The system accepts a command position signal and compares the command position signal to the actual position of a linear actuator to develop a position error that is then conditioned to produce a pair of valve drive signals that command series connected proportional valves that supply the linear actuator from a common connection of the valves with fluid flow and pressure to adjust the position of the linear actuator so as to reduce the position error by imparting motion to the linear actuator, thus imparting motion to a load. The conditioning of the valve drive signals includes the processing of the position error and the application of a quiescent drive signal to develop or nearly develop a quiescent fluid flow through the series connected valves. The quiescent drive signal can be automatically or manually developed.

Abstract: A material eject system includes an ejector mounted to a bed of a vehicle which is movable between a rear end and a forward end of the bed for ejecting material from the bed. The ejector is powered by a cylinder having different fluid volumes depending on the direction of motion of the cylinder. A control circuit operates with the ejector motor to automatically move the ejector through eject and return cycles. The ejector includes a speed control for operating the motor and the ejector at different speeds.

Abstract: An apparatus for the damped positioning of a piston running in a cylinder at one fixed abutment at least and more particularly for setting in a terminal position. The apparatus includes sensor means connected with an electronic regulating means for detecting the piston position as an actual value signal. A valve means adapted to be regulated by the regulating means serves for regulated braking of the piston prior to reaching the respective desired position by influencing opposing pressure in the cylinder outlet side. For forming the setting quantity for the proportional valve a position regulating means is provided which is modified by a value dependent on the respective speed and/or acceleration of the piston. This apparatus ensures an extremely accurate regulation of position simply by detecting of the position of the piston as an actual value signal. It is more particularly possible to brake the piston in the terminal positions with a damping action that an additional damping system is no longer necessary.

Abstract: A potentiometer-based gauge wheel position sensor system for use as part of an automatic depth control system. The potentiometer-based gauge wheel position sensor system works with a Console and remote Controller mounted in the tractor cab, power beyond Valving, and Depth Sensors, either ground contact or non-ground contact, mounted on the frame of the implement. The depth sensing system is provided to sense the actual penetration of an implement tool by determining the height of the implement frame above the ground. The gauge wheel system comprises an inverted pyramid structure having a horizontal support member coupled to the implement frame. At one end of the horizontal support member, a compressible vertical support member is coupled between a wheel and the horizontal support member. At the other end of the horizontal support member, a wheel leg extension is coupled between the wheel and the horizontal support member.

Abstract: To extend the control range of the pressure control in a brake system which is equipped with a brake power booster that is operable irrespective of the driver's wish, preferably electromagnetically, according to the present invention, the hydraulic pressure introduced into a master brake cylinder connected downstream of the brake power booster is determined and, following a comparison with a preset pressure value signal, is sent to a pressure controller having an output quantity which corresponds to a control current for the solenoid and is supplied to a limiter that determines the limit values of the desired control range, and the output quantity of the limiter is compared with the value of the current supplied to the solenoid. Subsequently, the comparison result is sent to a current controller which generates the voltage to be applied to the solenoid.

Abstract: Aircraft flight path changes commanded by a pilot via the wheel, column and pedal (12) are converted to position sensor signals (14) and passed as the input to primary flight computer (26). The primary flight computer (26) converts these pilot inputs and the inputs from autopilot (25) into desired surface actuator commands and then transmits them to actuator control electronics (18). The actuator control electronics (18) also receives a position feedback signal, representative of the position of the aircraft control surface (42). The actuator control electronics (18) produces a control signal which is fed to the input of an actuator (32) which includes a hydraulic system (34). The actuator responds to control input signals to drive linkage (40) which then positions the control surface (42).

Abstract: The invention discloses a power unit (1) which comprises: an accumulator battery (2); an electric converter (3) supplied by said accumulator battery (2); an electric motor (30) supplied by said converter (3); a hydraulic pump (4) mechanically connected to said electric motor (30), suited to put under pressure a liquid (50) which supplies one or more actuators (9) in order to lift a load (11) connected to them. Said pump (4) is of the reversible type and operates as a hydraulic motor suited to drive into rotation said electric motor (30) which operates as a generator supplying said battery (2) by means of said converter (3) whenever the descent by gravity of the load (11) supported by said one or more actuators (9) puts under pressure the oil held therein which passes through said pump (4) entering from the delivery opening (42) and coming out of the inlet opening (41).

Abstract: A fail-safe second stage valve for controlling actuator movement upon power loss in a multiplexed fluid power control system. The second stage valve is interposed between a corresponding actuator and a fluid multiplexer to operate generally as integrating or amplifying device which regulates flow to the actuator. The second stage valve is provided with a dampening mechanism in the form of a bleed port to reduce fluid flow to the actuator. The bleed port bleeds off accumulated fluid received by the second stage valve over a predetermined range of valve positions. This changes the position of the valve and thereby reduces flow rate to the actuator. The multiplexed fluid power control system using the fail-safe second stage valve controls the flow to the corresponding actuator upon electrical power loss. The actuator may be used to open and close variable stator vanes in an aircraft gas turbine engine.

Abstract: A system for determining the position of a piston moveable within a cylinder, or of an implement or joint, is disclosed herein. Electromagnetic (EM) bursts such as ultra-wideband or frequency pulses are generated and applied to a transmitter/receiver unit. The EM bursts are launched by the transmitter along a transmission guide from an end of the cylinder housing towards the piston. The transmission guide can be a dipstick mounted within the cylinder housing or the cylinder housing itself. The dipstick or cylinder housing is in electrical communication with the piston such that a surface of the piston represents an electrical impedance discontinuity which causes the EM bursts to be reflected back to the receiver. The time for the EM bursts to travel from the transmitter to the piston and for the reflections to travel back to the receiver is determined and converted into a position signal representing the piston's position.

Abstract: In order to accomplish many tasks of a machine efficiently, a motion planning system predetermines the response of the machine to a given set of motion commands. With two or more actuators being driven by a single hydraulic pump, there may not be adequate hydraulic pressure to drive both of the actuators at the speed requested. In order to determine the non-linear response of the actuators and the optimal combination of motions of the moving parts driven by the actuators, a controller for the machine is modeled as a linear dynamic system. The non-linear response of the actuators is modeled using a look-up table that is a function of internal variables of the machine's actuators and hydraulic system. The number of input, or independent, variables that are supplied to the table look-up functions is proportional to the number of actuators being driven by a single pump. Sensors provide data regarding the internal state of each actuator including variables such as spool valve position and cylinder force.

Abstract: A double-acting electropneumatic positioner for controlling an actuator, the actuator having a first and second chamber, comprises a single-acting electropneumatic positioner which provides an output pneumatic pressure to the first chamber of the actuator. A pressure inverter, coupled to the single-acting electropneumatic positioner, inverts the output pneumatic pressure. The inverted output pneumatic pressure is then coupled to the second chamber of the actuator.

Abstract: An electropneumatic positioner includes a data processing control section and an electropneumatic converter. The control section includes first and second position determining sections and a signal setting section. The first position determining section obtains the valve opening degree positions of a regulating valve as the minimum and maximum valve opening degree positions which are set when a driving signal for conversion from an electrical signal into an air pressure is set to the minimum signal and the maximum signal. The second position determining section obtains the valve opening degree position of the valve which is set when the driving signal is the minimum signal on the basis of the relative positional relationship between the obtained minimum and maximum valve opening degree positions and the valve plug form of the valve.

Abstract: An electro-hydraulic operating system for an extensible boom includes one or more hydraulic cylinders for imparting relative motion between the boom sections to retract the boom according to an electronically stored program of sequences of movement and speeds. A source of pressurized hydraulic fluid is fed through appropriate control valves which include solenoid valves in fluid communication with a source of pressurized hydraulic fluid. The solenoid control valves are supplied with control currents proportional to the desired flow rates of fluid to the hydraulic cylinders in order to achieve speed and position control according to the stored program. A metering valve structure is provided for operation in conjunction with the solenoid control valves.

Abstract: An apparatus for controllably moving a work implement. The implement is connected to a work machine and is moveable in response to the operation of a hydraulic cylinder. The apparatus includes an operator controlled joystick that generates an operator command signal, which is indicative of a desired velocity of the work implement movement. Cylinder position sensors produce cylinder position signals in response to the position of lift and tilt cylinders. A valve assembly receives an electrical valve signal, and controllably provides hydraulic fluid flow to the respective hydraulic cylinders to move the cylinders in accordance with the operator command signal. A controller receives the operator command and cylinder position signals, and responsively produces a pump command signal to change the displacement of a variable displacement pump to regulate the movement of the hydraulic cylinders.