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: The present invention includes an electropneumatic positioner having an external binary input block which provides access to the electrical output of an integral electronic position controller to control operation of a valve relay. The invention enables manual control of the positioner for safety, maintenance etc.

Abstract: A full fluid-linked steering system, especially for use in on-highway steering, in which the system includes a fluid controller (21) including a fluid meter (65) operable to provide follow-up movement to controller valving (87,89), in response to the flow of fluid through the meter. The controller (21) includes a centering or biasing spring assembly (75) which provides sufficient torque that, upon rotation of the steering wheel (W), fluid is communicated to the steering actuator (19) without relative displacement of the valving, thus providing driver with the desired road feel. The system includes an EHC valve assembly (23) which controls flow to or from the actuator (19) in response to appropriate input signals (113,115) to maintain steered wheel to steering wheel registry.

Abstract: A hydrostatic power steering system comprising a fluid motor (19) which receives pressurized fluid from a controller (17) in response to the rotation of a vehicle steering wheel (W). As the motor (19) or the steered wheels reach the stops, control logic (31) receives signals (37,77) representing steered wheel and steering wheel position, respectively, and generates appropriate command signals (33,27) to a pressure reducing/relieving valve (15) and to a proportional electromagnetic valve (23), respectively, closing the valve (15) somewhat, and opening the valve (23). A pressure differential is built between an additional fluid path (21) and the high pressure conduit (15c) between the controller (17) and the fluid motor (19). Pressure is communicated through the valve (23) into the conduit (51c), and back into the fluid meter (43) of the controller, preventing any further rotation thereof in response to an attempt to turn the steering wheel, thus eliminating travel limit slip.

Abstract: An indication means in a brake cylinder for a vehicle brake with a spring activated parking brake in which the brake cylinder comprises a cylinder housing (3) with a casing wall (22) and at least one gable (23). A pressure spring (5) is positioned between the piston (4) and the gable (23) of the cylinder housing for activating the parking brake by mechanically influencing the piston (4) of the brake cylinder. A bar (11) is axially displaceable relative to the release screw (1) in the throughbore (34) in the release screw (1). The bar (11) at a first end, within the cylinder housing (3), has a position sensing body (8, 16) which is axially fixed to the bar (11) and provided with a contact surface (40) for contact against the nut (7). At a second end the bar (11) has an indication body (12) which visibly protrudes out of the screw head (36) of the release screw (1) in case of axial displacement of the bar (11).

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: A control system controls actuation of a hydraulic cylinder on a skid steer loader. The control system includes a movable element, movable by an operator. A position sensor is coupled to the movable element and provides a position signal indicative of a position of the movable element. A controller is coupled to the position sensor to receive the position signal and provide a control signal based on the position signal. A valve spool controls flow of hydraulic fluid to the hydraulic cylinder. An actuator is coupled to the controller and the valve spool and moves the valve spool in response to the control signal from the controller.

Abstract: A locus control system of hydraulic excavators whereby a target locus for a front device is set beforehand. A control unit calculates a position and posture of the front device based on signals from angle sensors, and calculates a target speed vector of the front device based on signals from control lever devices. Through this calculation process, the control unit maintains the target speed vector as it is when the front device is not near the target locus, and modifies the target speed vector to a vector pointing to a second point on the target locus advanced in the excavating direction by a second distance from a first point located on the target locus at a minimum distance from a tip of the front device, when the front device is near the target locus.

Abstract: A valve control system for positioning a valve in response to a command signal. The valve control system comprises a sensor for detecting the position of the valve and for generating an outer feedback signal, a valve location command circuit for comparing the command signal to the outer feedback signal to generate a correction signal, an actuator for positioning the valve in response to pneumatic pressure, a spool slidably disposed within a block to direct pneumatic pressure to the actuator, a spool positioning device for moving the spool to a desired position, a spool sensor for detecting the current position of the spool and generating an inner feedback signal, and a spool location command for comparing the correction signal to the inner feedback signal to generate a spool positioning signal to direct the spool positioning device to move the spool to the desired position.

Abstract: In a hydraulic power steering for motor vehicles having a steering control element, a position setting unit connected to the steering control element, a control motor connected to the position setting unit by way of a control circuit and a servo valve having control parts which are supported so as to be rotatable relative to each other but operatively interconnected by spring means retaining them in a central open position relative to each other, one of the control parts is operatively connected to the control motor and the other is connected to a steering gear mechanism associated with the steered wheels of the motor vehicle, and a hydraulic servomotor is associated with the vehicle wheel steering mechanism and hydraulically connected to the servo valve to receive hydraulic fluid therefrom depending on the relative rotary positions of the servo valve control parts.

Abstract: A control for a hydraulic drive or actuator is provided, wherein the actuator has pressurized operating fluid applied thereto, and wherein the operating fluid is directed through an electrically controlled valve for establishing the amount of operating fluid to be fed to the actuator. An electrical signal for controlling the valve is provided by a computing device. In the computing device, a predetermined desired value for the position (or travel), force, or pressure of the actuator or drive is continuously calculated based, at any given time, at least on one measured or simulated state variable indicative of a condition of the drive or actuator at the time of calculation. The calculated desired value determines the amplitude of the electrical signal directed to an electrical actuating device of the valve. The computing speed of the computing device for determining the respective desired value is faster than the actuating velocity or speed of the valve.

Abstract: A large manipulator, especially for self-propelled concrete pumps includes a rotary head that rotates about a vertical axis on a mast stand, and a jointed or articulated mast composed of at least three mast arms. The mast arms of the jointed mast can be swivelled to a limited extent about horizontal, mutually parallel axes relative to the adjoining rotary head or mast arm using a corresponding drive unit in each case. The jointed mast is operated by a remote control device which has a signal transmitter situated at the mast top and a control unit. The signal transmitter drives a computerized coordinate field device actuating the drive units according to a displacement path relative to the momentary position of the mast top as directly indicated by means of the control unit.

Abstract: In a hydraulic device at least one control valve with at least three control positions is connected with a variable capacity pump, whereby the controlling device of the variable capacity pump is connected with the supply line downstream the control valve via a feedback line with the purpose of adjusting the pump output so as to maintain a constant operational pressure gradient. The back flow pipe is conducted over the control valve, which is connected with the consumers by connecting valves associated to mentioned consumers, whereby a transducer is associated to the back flow pipe, which together with the transducer of the supply line constitutes a regulating variable for a control unit. This way a precise and energy saving regulation or control of the consumers in both flow directions by a control valve at a reasonable price is achieved.

Abstract: A system and method for controllably positioning a hydraulic actuator which is operably connected to a control surface includes at least one main control valve for controlling the hydraulic pressure supplied to the actuator in response to a control signal indicative of a predetermined actuator position and at least one parallel control valve for supplying additional hydraulic pressure to the actuator in response to an error signal indicative of the difference between the position of the actuator and the predetermined actuator position to thereby correct for any differences indicated by the error signal. By correcting for any differences indicated by the error signal, the errors in positioning the control surface can be decreased and the stiffness of the control surface can be increased.

Abstract: A closed loop hydraulic system especially adapted as a shot control system for a die casting machine. The control system includes a voice coil driven pilot servo valve mounted to a high flow proportional valve. The control system provides a highly controllable restriction of the outflow of hydraulic fluid from a hydraulic shot cylinder which drives a shot plunger of a die casting machine. Position transducers are provided for the pilot servo valve, proportional spool valve, and shot cylinder and a control system monitors these inputs to provide closed loop control over the shot process. A hydraulic accumulator is located in each of the pressure source and return lines of the pilot servo valve and a hydraulic accumulator tank is mounted directly to the proportional valve.

Abstract: An automotive hydraulic control system varies hydraulic fluid pressure applied to an actuator to position the actuator in accord with an automotive control application, the fluid pressure being generated in accord with a pressure command output from a hydraulic control function responsive to desired fluid pressure and to deviation in measured or estimated actuator transient response away from preferred actuator response to compensate for variations in hydraulic control system operating conditions.

Abstract: A hydraulic drive in accordance with the invention includes an axial piston hydraulic motor provided for forming a power drive with a follow-up control valve provided for controlling the pressure medium supply with the follow-up control valve being electronically controlled by a desired position value presetting and mechanical actual position value acknowledgement. An electric motor is provided for the desired position value presetting which can be activated by output signals of a central CN or CNC control unit. The rotor of the axial-piston hydraulic motor is rotatably supported with a circular-cylindrical tubular section of an output shaft thereon on an outer casing surface of an axial extension which is a hollow tubular shape and forms a pivot pin for the rotor of a housing section accommodating the electric motor provided for the desired value positioning control.

Abstract: An electro-hydraulic servo mechanism comprising: a hydraulic actuator formed with a pair of hydraulic chambers and having an output member which is displaced by a differential pressure between the hydraulic chambers, the output member being connected with an object to be controlled; an electro-hydraulic converter for varying the differential pressure between the hydraulic chambers in response to an electric signal; a first differential transformer for outputting a first induced electromotive force proportional to the displacement of the output member; a control circuit for generating the electric signal in response to the output of the first differential transformer and to an external command signal and for outputting the electric signal to the electro-hydraulic converter; a pressure receiving member that is displaced in response to the differential pressure between the hydraulic chambers; and a second differential transformer for outputting a second induced electromotive force proportional to the displacemen

Abstract: A system includes two lower articulated longitudinal arms (6, 7) provided on their front ends with two bottom hitching points (8, 9), and an upper arm (10) in the middle, for hitching an implement at a third point; valves for controlling the rise and descent of the two lower arms and of the upper arm are provided, and the implement (3) is equipped with hitching members (11) corresponding to the three point hitch of a tractor; a rigid intermediate support frame (12) is provided for connection between the implement and the arms (6, 7, 10); the frame includes two bottom lateral points (13, 14) and one top middle point (15) for hitching the implement, and two lateral top points (16, 17) intened to be connected to the third top hitching point (10) of the tractor by connection jacks of variable length; the two lower arms (6, 7) are independent and can assume different inclinations, and the two lower lateral portions (22, 23) of the frame (12) are hitched to the two bottom points (8, 9), the assembly being such that

Abstract: An electro-fluid converter for controlling a fluid actuating an adjusting element, such as a main control slider of a servo valve, comprises at least one displaceable throttle arranged in a fluid-rich circuit. The throttle has at least one throttle element with a central inlet passage and a plurality of flow-mechanical identical base elements arranged around the central inlet passage in a star-like manner. Each of the base elements includes a bipolar wall stream element connected with the inlet passage and a whirling chamber element connected with the wall stream element, each of the wall stream elements being thermoelectrically controllable.

Abstract: The position (x) of a hydraulic press or punch press is controlled highly dynamically, by a controller which uses the velocity (v) and the acceleration (a.sub.B) of a piston. While the position (x) and the velocity (v) are sensed by customary measuring devices, the acceleration (a.sub.B) is determined by means of a sensor (B) from the pressure (p) of the hydraulic fluid and the piston velocity (v). Thereby, an expensive acceleration measurement can be dispensed with by utilizing the already existing pressure measuring arrangement. The sensor (B) can further determine an interference quantity signal (f.sub.zB) which can be fed to the control element (SG) for the purpose of generating a compensating interference signal.

Abstract: An apparatus for positioning a work implement in predetermined operative attitudes, including a valve body mounting a piston which is operable for movement through a range of selective operative positions, and which is further connected to the work implement; a pair of pulse valves mounted on the valve body and connected in fluid communication with the piston and operable selectively to supply a source of hydraulic pressure to the valve body; and an actuator is connected in signal transmitting relation to the pair of pulse valves and is adapted selectively to actuate same thereby causing the selective release of hydraulic pressure to position the piston, and thus the work implement in a selected operable attitude.

Abstract: An article handling apparatus is disclosed which comprises two independently controllable fluid actuated drives. The first fluid actuated drive comprises a cylinder and a differential piston which defines a large chamber and a smaller chamber. Also, a control system is provided which maintains a differential pressure between the large and small chambers in each of several operating positions. The second fluid actuated drive is mounted to the movable member of the first drive, and the second drive is controlled by fluid lines leading respectively to the large and small chambers of the first drive.

Abstract: A novel digital servo valve system for use in displacing an actuator is capable of operating either in closed or open loop mode. The system includes a controller that compares computed values of actuator parameters with preselected parameter values and iteratively determines therefrom command signals for the servo valve. The servo valve is characterized by a ball screw mechanism that eliminates mechanical backlash and a torsion bar which increases radial and angular compliance. A servo valve provided according to the present invention also displays reduced flow forces using a simple, inexpensive valve body in combination with a uniquely configured displaceable spool.

Abstract: An electro-hydraulic servo actuator with function for adjusting rigidity. The electro-hydraulic servo actuator comprises an electro-hydraulic transducer which transduces an electric signal into a hydraulic signal, an actuator of a cylinder type which is operated by the electro-hydraulic transducer, and a position detector which detects a position of an output member of the actuator to emit a positional electric signal. The hydraulic-element transducer is a bias piston which is disposed within a actuator rod of the cylinder type actuator and which floats in response to a differential pressure within the cylinder, and the piston is connected to the position detector.

Abstract: For path control of a plurality of drives, i.e. for driving a plurality of drives in different axes in geometrical path dependence, to obtain high accuracy it is necessary for the lag error of the drives to remain constant. According to the invention for this purpose a circuit arrangement is proposed in a cascade structure in which from the speed of each individual path drive and the control deviation determined from the actual value and desired value of the position a difference signal is formed which is integrated and added to the output signal of a P controller.

Abstract: A hydraulic driving device includes a working cylinder for moving a machine component, and an electro-hydraulic servo system. The servo system includes a servo-valve, a position-error control, a circuit for emulating speed and acceleration of the working cylinder, and a regulator for weighting the ascertained position error according to the emulated speed and acceleration, and generating a setting signal for the servo valve.

Abstract: Means for servo-controlling the position of a pneumatic actuator (14) comprise a circuit (20) for controlling a valve (10) for feeding the actuator, and a position sensor (30) and an acceleration sensor (34) which are associated with the moving member (16) of the actuator and which provide position and acceleration signals to the control circuit (20). The invention improves the stability and the accuracy with which the position of a pneumatic actuator is servo-controlled.

Abstract: For setting and guiding a band running round two rolls the bearings of the roll on either side are each adjustable by a hydraulic or lifting cylinder. Each hydraulic cylinder comprises a position control circuit. The position desired value applied jointly to the position control circuits is varied by a tension-dependent control in such a manner that in the position adjustment a maximum admissible tension force is not exceeded. Furthermore, the position desired value has superimposed thereon a correction control by which the center setting of the band is monitored. The arrangement is preferably provided for positioning and tension-dependent adjustment of the encircling metal band of a sheet casting apparatus.

Abstract: An electronic bucket positioning and control system for a vehicle of the type including a hydraulically controlled boom assembly and bucket. The bucket positioning and control system can operate in a bucket positioning mode, bucket return to position mode, bucket anti-rollback mode, and tilt cushion mode.

Abstract: A metering valve comprised of two rotary registers are each provided with cutouts which are symmetrical in relation to the axis of the central opening defined by the movement of the registers. In accordance with the present invention, a mechanism for operating the registers synchronously and in opposite directions is composed of levers and connecting rods acting on the axis of suspension and rotation of the registers through the action of, for example, hydraulic jacks. In order to avoid the offsetting of the flow because of the difference between the radii of curvature of the registers, the entire mechanism is adapted to pivot as a whole about the pivot axis of the registers.

Abstract: A control force input system for a balance beam or pivot arm pneumatic positioner which does not allow the controlled apparatus to make a full travel motion when the overall control signal is removed. The control force is transmitted to the balance beam by the coupling of the magnetic fields produced by a fixed magnet located on the balance beam and a variable magnet located away from the balance beam. When the motive control signal is removed from the variable magnet, the balance beam returns to an equilibrium or zero position due to the action of a pair of zero springs, stopping the controlled apparatus at its position when the control signal is removed.

Abstract: A metering valve comprised of two rotary registers are each provided with cutouts which are symmetrical in relation to the axis of the central opening defined by the movement of the registers. In accordance with the present invention, a mechanism for operating the registers synchronously and in opposite directions is composed of levers and connecting rods acting on the axis of suspension and rotation of the registers through the action of, for example, hydraulic jacks. In order to avoid the offsetting of the flow because of the difference between the radii of curvature of the registers, one of the connecting rods acting on the axis of the registers is adjustable in length.

Abstract: A servomechnism made up of a relatively small number of components has a pintle that is moved back and forth by a hydraulic actuator, an input member disposed opposite to the pintle and capable of reciprocating parallel with the pintle, a spool capable of reciprocating parallel to both the input member and the pintle, a pair of idle gears pivoted to the spool, and a hydraulic circuit. The input member has a rack opposite to a rack formed on the pintle. The spool is mounted between these racks. The idle gears are in mesh with the racks. When the input member is moved to shift the spool out of its neutral position, the actuator is unlocked to return the spool to its neutral position.

Abstract: An electrohydraulic system includes a plurality of electrohydraulic devices individually controlled by on-board microprocessor-based control electronics. Each individual device controller is connected to and addressable by a master controller for coordinating operation of the various devices. An electrohydraulic servo valve assembly includes a hydraulic manifold having a valve spool variably positionable therein under control of a torque motor. A microprocessor-based controller is connected to the torque motor and is mounted on the manifold by a cover which encloses and protects both the controller and the torque motor. A watchdog timer in the microprocessor-based controller monitors pulsewidth modulated signals to the torque motor for terminating operation in the event of signal loss. In a preferred embodiment of the invention, the servo valve assembly is coupled to a linear actuator which has its position monitored by an electroacoustic transducer.

Abstract: The invention is a control system for generating time modulated pulse signals to effect movement of a doser type actuator. The control system is characterized in that it includes an augmenter circuit which generates a first correction signal additive to scheduled control signals when the actuator fails to respond or has a response below a predetermined limit to an actuating pulse, a second correction circuit which generates a correction signal proportional to the magnitude of the first movement of the actuator response to a pulse signal for reducing the magnitude of the pulse signal in proportion to the magnitude of the movement, and a gating signal or circuit which blocks said first and second correction signal generating circuits generating the augmentation signal when the movement of the actuator in response to a pulse signal is negative or above a predetermined limit, when the positional error changes direction, or when the actuator position is within the desired deadband limits.

Abstract: An apparatus for controlling a hydraulic single acting cylinder has first and second solenoid operated valves disposed in a supply line through which a working fluid is supplied to a working chamber defined in the cylinder which a piston is disposed, a third solenoid operated valve disposed in a return line through which the working fluid returns from the working chamber to a hydraulic tank, and a control unit for controlling the first to third solenoid operated valves. The second and third solenoid operated valves are solenoid operated proportional pressure control valves so that the piston speed can be regulated.

Abstract: A remote control proportional flow adhesive dispensing gun is pneumatically actuated and electrically controlled. An electric current applied to a magnetic torquemotor rotates a torquemotor arm which displaces the spool of a three-way air valve, admitting air to a control valve stem actuating piston. A constant rate feedback spring directly disposed between the actuating piston and the torque arm of the torquemotor acts to restore the air valve spool to an equilibrium non-flow position as the control valve stem approaches a position proportional to torquemotor control current. The air valve exhausts air from the piston and return springs close the control valve when control signal is removed. A shaped control plug attached to the flow control valve stem varies a control opening linearly as stem position changes.

Abstract: Pressure fluid operated servo system method and apparatus including a servo valve operable by an input signal to effect a system output movement; and which servo valve is responsive to the time rate of input signal receipt to vary a gain ratio of system output magnitude compared to input signal value; and method of making such a servo valve.

Abstract: The known power steering system of the type that movement of a steering wheel is transmitted via a torsion bar to an oil path switching valve to actuate a power cylinder in a desired steering direction by switching a high pressure oil path extending from an oil pump to the oil path switching valve and a low pressure oil path extending from the oil path switching valve to an oil tank and a part of working oil flowing through the high pressure oil path is led to a reaction piston to restrain torsion of the torsion bar, is improved in that the power steering system comprises a control oil path branched from the high pressure oil path and communicating with the reaction piston, a pressure control valve interposed in the control oil path for controlling an oil pressure to be equal to or lower than a predetermined highest pressure, a flow rate control valve provided on the downstream side of the pressure control valve for controlling a flow rate depending upon a car speed, a first orifice for communicating the down

Abstract: Two magnetic valves, one of which reduces the pressure and the other one of which increases the pressure by which the displacement of a positioning member is controlled, only one of them operated at a time in accordance to the sign of the error signal, are operated in a pulsed mode with variable pulse width when the error signal is within a range of low absolute value and in a continuous mode of operation when the error signal has a higher absolute value. Variation of the magnitude of the error signal within the intermittent valve operation range controls pulse width variation. Hysteresis is provided in a transition between operating modes of a valve by a time delay of the mode change after the error signal has risen or fallen past a threshold value of signal. High displacement resolution is obtained as well as independence from effect of temperature drifts and magnetic valve characteristics.

Abstract: A fast opening valve apparatus includes an electronic sensing circuit to determine when a positional error signal exceeds a predetermined reference value corresponding to an opening rate reference value. The sensing circuit provides a fast open command signal which is applied to a solenoid valve which is hydraulically coupled in parallel with a control servo valve. The control servo valve hydraulically couples a primary source of hydraulic fluid under pressure to a valve actuator which is mechanically coupled to a valve stem of an associated steam valve desired to be controlled. The activated solenoid valve opens a supplemental hydraulic fluid path between the valve actuator and the primary source of hydraulic fluid. To ensure an adequate hydraulic fluid pressure at the input of the servo valve and solenoid valve, an auxiliary source of hydraulic fluid under pressure may be coupled upstream of the servo valve and solenoid valve.

Abstract: An electrohydraulic control system which includes first and second electrically controlled fully variable hydraulic pumps adapted to be driven by the vehicle engine. In the specific embodiment of the invention herein disclosed, the first pump is coupled to the steering and braking control valves, and the second pump is coupled to the bucket and hoist control valves. An electrically controlled poppet valve selectively interconnects the respective pump outputs. Operator-responsive controllers, namely a bucket/hoist joy-stick controller, a vehicle propulsion controller and a steering controller, provide associated electrical signals as respective functions of operator demand. Electrically operated valves control application of hydraulic fluid to the bucket and hoist drive mechanisms, and pressure and position sensors are connected to such valves and actuating mechanisms.

Abstract: A multiple-mode, multiplex pumping apparatus includes circuit control elements for initializing the apparatus by placing each of the pistons and plungers in each pumping section of the multiplex pumping apparatus at a respective initial starting point. The pumping apparatus also includes electronic circuit elements for controlling the inlet valves, exhaust valves and precompression valves of the hydraulic circuit of the pumping apparatus. The apparatus includes phase control circuit elements for controlling the separation of the leading edges of the plungers of two of the pumping sections of the apparatus when the apparatus is operating as a quadruplex pump. The pumping apparatus also includes elecrtronic circuit elements for insuring that each plunger of each pumping section stops at a fixed stopping point. The apparatus also includes electronic circuit elements for controlling the volume of fluid in the rod end portions of each of the pumping sections.

Abstract: A servovalve device assembly is provided with an electronic matching circuit positioned upstream of the servovalve. The matching circuit supplies electric control signals whose purpose is to modify the hydraulic flowrate response curve of the servovalve as a function of the electrical control signal, so as to make it substantially identical to an ideal desired response curve.

Abstract: An electronically controlled apparatus for controllably positioning pneumatic actuators includes, in a first embodiment, first means for selectively flowing compressed fluid to the actuator and valve means for selectively exhausting compressed fluid from the actuator. An electronic control panel is adapted to receive digital command signals from a computerized controller and is coupled to the first means and to the valve means for actuation thereof in response to the command signals. Means are included for isolating electrical switching transients from the controller.In a second preferred embodiment, the positioner also includes transducer means for generating a feedback signal representative of the position of the actuator piston assembly. A third preferred embodiment is similar to that of the second embodiment and incorporates a control adapted to receive analog rather than digital command signals. An optional high limit pressure switch may be used with any embodiment.

Abstract: An electro-hydraulic proportional actuator in which the actuator piston position is hydraulically controlled by fluid flow through solenoid valves operable by an electronic control system. An operator control provides an input voltage representing a desired piston position and a transducer generates a voltage representing the actual piston position. The difference between the input and output voltages generates a difference or error signal that is fed into a feedback system including a sample-and-hold circuit. A clock logic system is provided for transmitting the signal from the feedback system to the solenoid valves at predetermined intervals to activate either valve to move the actuator piston in either direction or to activate both valves to hold the piston at a desired position.

Abstract: In a hydraulic piston actuator the supply of working fluid is governed by at least one servo valve of the three-gate type, the spring-loaded valve body of which is activated by a thermowire adapted normally to hold the valve body in a position to close-off the supply of fluid. One end of the thermowire is connected to a compensating device, goverened by the movement of the actuator piston in such a manner that thermal movements are partly counteracted. The servo valve may actuate a maximum switch, and a time relay will, after a predetermined period of time put the fluid pump out of action, and connect both sides of a double acting actuator with a return flow tank.

Abstract: A control system for controlling a double-acting cylinder includes four pilot-operated, proportional-type poppet valves for controlling fluid flow between the cylinder, a pump and a reservoir. Four solenoid-controlled pilot valves operate the poppet valves in response to error signals generated by a control circuit. The control circuit receives a cylinder position feedback signal and an operator-generated command signal. The control circuit provides for float, shutdown, variable deadband and pressure adjustment operation.