Abstract: A valve actuator control system, although suitable for many control functions, is especially adapted for remote control of plug-type valves utilizes a unique configuration providing a unitary explosion-proof container to house all electrical components and also providing a manifold assembly that is adapted for either a hydraulic or pneumatic actuator motor with relatively minor modification. The manifold assembly is designed to accept all utilized control valves, relief valves, check valves, flow control devices, and manually operable override controls thereby simplifying installation and maintenance and reducing attendant costs. Three independent solenoid valves, responsive to mechanical feedback provided through the plug-valve's operating stem and integrated into the manifold within the explosion-proof container, provide for actuator motor control including a novel dual speed capability for enhancing plug-valve performance while precluding costly premature wear.

Abstract: An external combustion engine comprises an actuating cylinder in which a piston with rod is mounted for reciprocation, said piston serving as the actuating member, a valve distributor serving as the switching member, as well as a crank gear serving as the converter of the piston reciprocation to the drive shaft revolution. The piston divides the cylinder cavity into two, namely, a rod cavity and a rodless cavity. Each one of the cavities communicates with a source of working fluid via valve distributor. The piston rod is operatively connected with the drive shaft via crank gear. The engine further comprises an electric oscillator whose frequency is variable in accordance with the preset r.p.m. of the drive shaft, connected electrically with the converter in the form of a linear dynamic link, and a transducer indicating the current value of the piston position relative to its neutral position. The linear dynamic link is coupled mechanically with the distributor slide valve.

Abstract: A dual automatic leveling system for a blast hole drill during raising and lowering which includes "fine" level sensors to detect an attitude within a fine level range and "coarse" level sensors to detect an attitude outside a coarse level range which is greater than that of the first. A controller is connected to the sensors as well as to appropriate valving with a pressurized fluid source so as to operate hydraulic jacks. The jacks are activated in a first mode in conjunction with the "fine" sensors and in a second mode in conjunction with the "coarse" sensors. In a preferred manner, the "fine" and "coarse" level sensors are positioned as front, rear, and end level sensors mounted on the main frame of the blast hole drill. The "fine" level sensors in conjunction with a programmable logic control will initially level the drilling platform within a .+-.0.5.degree. (both transverse and longitudinally). If during the raising or lowering process the platform becomes out of level by 2.degree.

Abstract: An electrohydraulic actuator system has a first pair of actuators and a control circuit and a control valve for each actuator. The control circuits generate actuator position error signals and are also responsive to divergence of the operating position of the respective valves from a mean valve operating position thereby tending to maintain the valve operating positions, and hence the forces on the actuators, identical. The magnitudes of the position error signals are limited to limit overdrive of the valves in the event of minor malfunctions thereof and to permit a malfunction indication to be provided. The system also includes a further pair of actuators having an associated control circuit which is responsive to a selected differential position of the further actuators, for causing one of these actuators to be driven away from a limiting position of the other actuator until the required position differential is obtained.

Abstract: A system for positioning a movable body for a processing machine. A lead screw is rotatably and axially shiftably supported and engaged with the movable body. The lead screw is rotated by a motor to move the movable body. A hydrostatic thrust bearing is provided for preventing axial movement of the lead screw. The lead screw is finely moved in the axial direction by controlling the pressure difference of oil supplied to the thrust bearing to position the movable body.

Abstract: A pumping system for producing uniform discharge and suction rates includes a pump connected to a supply of hydraulic fluid to deliver hydraulic control fluid at a selectable flow rate to a proportioning valve. The proportioning valve divides the flow of hydraulic fluid into two resulting flows, each of which is utilized via a four-way valve to drive a piston within a hydraulic cylinder. The positions of the pistons within the cylinders are detected and used to control the proportioning valve such that each piston is imparted with a velocity that varies in a sinusoidal manner in response to the hydraulic fluid delivered to it by the porportioning valve. Sensing of the piston positions and control of the proportioning valve may be accomplished mechanically by a system of cams driven by the pistons, or electronically by a microprocessor receiving signals from transducers coupled to the pistons.

Abstract: At an installation comprising a roll stand having at least one roll of the variable camber type, comprising a fixed support and a casing carried by at least three jacks and rotationally movable about the support, the pressure of the fluid in each of the jacks (14), the position of the pistons of these jacks, the speed of rotation of the roll, and the flatness and thickness of the flat product are measured. The position of one of the jacks (14b) is controlled by the thickness measurement. The pressure in the other jacks (14a, 14c, 14d, 14e) is controlled by the pressure in the one jack (14b). The positions of the end jacks (14a and 14e) are compared and the pressure in the jacks (14) is modified in order to bring the tilt of the roll to a suitable value. The deformation of the fixed support is calculated and the shape of the generatrix of contact of the roll is determined. The pressure in the jacks (14) is modified in order to bring the generatrix to a reference shape.

Abstract: A control system (10) for supplying an operational chamber (38) in an air motor with pressurized fluid causing rotors (18 and 20) therein to move and develop an output torque in response to an input signal. Electrically operated valves (52 and 54) selectively controlling the flow of fluid from first and second bellows means (48 and 50) which are normally seated to seal distribution conduit (34 and 36) connecting the operational chamber (38) to the atmosphere. A select high disc valve (104) in the fluid pressure supply passage provides operating fluid to the distribution conduit (34 or 36) opposite the one which is vented to the atmosphere. In a two position air motor powered actuator, the electrical signals for the valves (52 and 54) may be derived as a simple function of actual rotor rotation and rotor rotational speed.

Abstract: An automatic depth control system is disclosed. The system includes a floating piston hydraulic cylinder in which the floating piston is adjusted as a stop for limiting the travel of the main piston in the cylinder. A depth sensing system is provided to sense the actual depth of a implement tool on which the cylinder is mounted to provide a depth signal indicative of the depth penetration of the tool. A circuit system is provided to receive the depth signal and to control a hydraulic valve system to move the stop piston within the cylinder to adjust the working position of the implement tool. The control system includes an instrument panel having a first display indicating the actual depth of the implement tool and a second display indicating the depth limit settings predetermined by the operator. Further means are provided to monitor the actual depth and compare it to the selected depth setting and thereby correct the position of the floating piston.

Abstract: An electrohydraulic servo control system which includes a position feedback loop responsive to actual position at the hydraulic actuator and load, and a position command reference generator responsive to an operator joystick input command and to an operator mode select switch for generating a position command reference signal to the position loop as differing functions of the joystick input in each of the switch-selectable modes. The selectable modes of operation include an absolute position control mode wherein the joystick input is treated as indicating absolute desired position at the actuator and load, an incremental position control mode wherein the joystick input is treated as indicating desired change in position with reference to a base position, and a velocity control mode wherein the joystick input is treated as indicating velocity at the actuator and load desired by the operator.

Abstract: A safety and centering device for rotors suspended in contactless magnetic bearings, which provides almost instantaneous centering support for the rotor if the bearing magnets loose power. In a preferred embodiment, the rotor shaft has a collar with a conical friction surface, and a sleeve controlled by an electro magnet with counter-acting springs and also having a conical friction surface. In case of power failure the springs force the two surfaces together and provide centering support for the rotor. In another embodiment having a vertical rotor, the bearing magnets lift the rotor with the friction collar out of engagement with the matching stationary friction surface when the rotor is operating; but if the rotor bearings become de-energized the rotor drops with the collar falling into engagement with the matching friction surface.

Abstract: A linear servoactuator including an integrated split-secondary differential transformer position sensor and a fluid driven linear actuator controlled by solenoid poppet valves. Signals from the position sensor transformer are digitized and linearized by a control microcomputer by using digitized transformer signals as addresses for a programmable read only memory. The linearized output is compared to a command position to determine an error value. When the error reaches a predetermined magnitude, indicating that the actuator is approaching the command position, solenoid poppet valves are actuated by a pulse-width modulated signal from the microcomputer to progressively decrease the fluid flow to the actuator for deceleration.

Abstract: A system and method for pulse-width modulation of multiple solenoid-operated valves in an electrohydraulic servo system employing a microprocessor-based digital controller. Solenoid-energization pulse widths are identified by comparison of operator command input signals to feedback signals responsive to actual motion at the actuators and loads. During each modulation period, all solenoids are initially selectively simultaneously energized as a function of binary information stored in an energization control register, and the shortest energization pulse duration is identified. After a delay corresponding to such shortest duration, during which the microprocessor may perform other control functions, the solenoids associated with such shortest duration are selectively de-energized as a function of binary information stored in a de-energization control register.

Abstract: A temperature control device used in an automobile air conditioner system includes a potentiometer for detecting the opening amount of an air-mix door. The potentiometer is tapped and includes at least one auxiliary resistance connected in parallel with a resistance element of the potentiometer.

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: A digital proportional valve with valve spool driven in discrete steps by a digital spool actuator in response to a remote manual control signal, while the proportional valve may be provided with positive and negative load compensation.

Abstract: The slide (61) of an electrohydraulic valve (31) delimits two end chambers (57, 58) respectively fed by a control pressure that is a slave to the open or closed state of one of the two solenoid valves (51, 52) controlled by signals processed by an electronic control (50) and the establishment of a state acts on the slide (61) in direction of a throttling of the delivery which causes a feed channel of the valve (31) and a working line (27, 28) from a pump (1) to communicate with the line (70) for connection with the fluid tank (2).

Abstract: A method of controlling the duty ratio of operation of a solenoid control valve in a fluid passage to control the flow rate of fluid in the fluid passage to a desired value. A flow rate value range is divided into a plurality of flow rate value regions between first and second extreme flow rate values which the fluid can assume when the duty ratio assumes corresponding minimum and maximum values. A first predetermined duty ratio value is preset corresponding to each of the divided regions and dependent upon the magnitude of manufacturing variations of the duty ratio-to-flow characteristic of the valve. A second larger predetermined duty ratio value is preset corresponding to each of the divided regions.

Abstract: A remote handling manipulator having a slave arm and a manually operated controller with a grip mechanism, is provided with a force feedback system to impose a force resisting operation of the grip mechanism related to a load experienced by the slave arm. A jaw mechanism of the slave arm is operated by a pressurized fluid, and in the system the pressure of the fluid and the effort exerted by the grip mechanism are compared to produce an error signal used for regulating the force applied to the grip mechanism.

Abstract: A pressure operated control installation, especially for automotive vehicles, which includes a pressure source and a servo member controlled through a control block. The control block includes a logistor, a control element coupled with a control unit, and a bypass line with a throttling arrangement. The pressure conducting inlet of the logistor is connected through the bypass line to a control inlet of the logistor and the control unit controls a connection between the control inlet of the logistor and a return line. At least two control blocks are provided with a control outlet of the logistor of the first control block and a pressure conducting inlet of the logistor of the second control block being connected to the servo member.

Abstract: An active pneumatic mechanism and a passive hydraulic mechanism of the apparatus are so connected with each other and with a driven member that movement imparted by the pneumatic mechanism to the driven member produces, and is controllable by restriction of, hydraulic fluid flow within the hydraulic mechanism. Restriction of the fluid flow to any desired extent is accomplished by command signals directed by a control computer to a valve that preferably is of the type actuable by a torque motor. The command signals produced by the computer are based upon a correlation of data supplied by a computer program with data supplied by a monitor of the positions of the driven member along its path of travel. Precise control of the speeds, accelerations and positions of the driven member are realized.

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: A method of controlling the revolution of the drive shaft of an external combustion engine comprises shaping a control signal for a switching member and converting said signal to mechanical movement of an actuating member. The control signal is shaped in the form of symmetric, periodic sustained vibrations of variable sign, the time intervals of positive and negative values of said vibrations being of equal duration, and the frequency of said vibrations is set equal to a preset number of drive shaft revolutions. The variation of said movement corresponds in time to variation of the control signal, an instantaneous value of the control signal is varied in proportion to the variation of load on the drive shaft, and the actuating member movement is converted to revolution of the engine drive shaft.

Abstract: A control system for a superhigh pressure generation circuit includes a hydraulic pump having a usual range of delivery pressure. An electrohydraulic servo valve controls the flow rate of pressurized fluid from the pump and supplies it to a primary side of a boost cylinder. A stepped piston slidably received in the boost cylinder strokes in response to the input fluid to generate a fluid pressure elevated in accordance with an effective sectional area ratio of the stepped piston in a secondary side of the boost cylinder. The fluid pressure in the secondary side is caused to coincide accurately with a reference pressure level on the basis of a feedback control.

Abstract: A pneumatic control system for machines that provides precise incremental or continuous direction, position, velocity and acceleration control of a variety of machine functions, such as rotary or linear motions, tool positioning and the like. A compressed air supply is maintained accurately at a preselected minimum pressure necessary for a particular operation, by a digitally pulsed air flow control system. Air flow and pressure to the associated actuating mechanisms is also controlled by a digital dithering technique using individual sharp pulses of air, each of which instantly breaks the static friction of the mechanism and causes a discrete precise increment of movement, with rapid consecutive pulses providing continuous motion. The direction, amount, acceleration and speed of travel are controlled by varying the pulse width and rate of air flow and pressure as necessary and for efficiency in air consumption.

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: A shot cylinder controller for injection molding machines comprises a valve connected with one side of the shot cylinder and including a valve head which is movable with respect to a seat. The valve head is connected with at least two, lineally extensible actuators, interconnected in an end-to-end relationship. The actuators are independently extended and retracted, whereby selective manipulation of the actuators varies the position of the valve head, and thereby controls the extension of the shot cylinder and regulates the speed of die injection.

Abstract: A redundant swashplate control system includes five or more actuators coupled to the swashplate. A feedback network independently controls each actuator to track a commanded position and a reference ram differential pressure that it related to the ram differential pressures sensed from all of the actuators.

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.

Abstract: An application of the basic system of patent application Ser. No. 149,065 for operating a remote hydraulic valve. An electro-hydraulic actuator is mechanically linked to the control member of the remote valve. An input control signal is generated by multiplying a signal from a control handle position transducer by a scale factor constant produced by a full control setting with a gain control circuit. The gain control circuit also operates to set the constant to unity in case the signal from the handle position transducer exceeds a predetermined level corresponding to a maximum control handle setting.The control handle itself has four positions: Float, Lower, Neutral and Raise. The handle is biased so that if the handle is released from any position other than Neutral, the handle will go to the Neutral position provided a detent is off. The detent is put in the "off" position by an electrical solenoid which is actuated whenever the supply pressure to the remote valve exceeds a set value.

Abstract: In a pulse modulated servosystem having solenoid activated on-off valves governing the amount of fluid in two variable volume chambers of a double-acting piston-cylinder unit any limitation of the accuracy due to inertia of the valves is eliminated by influencing both chambers in opposite directions.

Abstract: A control system 54 for a doser type hydraulic actuator 56 is disclosed. The doser actuator includes a pair of unequal area pistons 18, 20 on a common shaft 16 which are moved incrementally by injecting into or removing from a control pressure chamber metered quantities or doses of fluid. The doses are metered by timed openings of solenoid valves 32, 34 connecting the control pressure chambered to a supply 44 or return 48 pressure sources. The control system includes a base pulse width signal generator 106 which pulse modulates the solenoids as a function of the error between a requested position and an actual position. The base pulse width is modified by a correction means 108, 110, 112 when the error is within a predetermined band width. The correcting means compensates for the reaction of the actuator when its response is uncertain with respect to the base pulse width.

Abstract: To reduce the piston velocity in a cylinder as the piston approaches the end positions, a signal transmitter is provided for sensing the position of a part driven by means of the piston and cylinder assembly, and thus of the piston in the cylinder. The signal of the signal transmitter is applied to a control unit in which it is compared with a signal from an actuator means. The signal from the actuator means controls the extension and shortening of the piston and cylinder assembly and the velocity at which this occurs, and may be positive or negative. The comparison of signals is so exploited that if it is established by this comparison that the piston is not in the areas of the end positions or, alternatively is in these areas but is activated by the actuator means to move away therefrom, the signal from the actuator means is not acted upon, whereas if the piston is in these areas and approaches the end positions, the hydraulic fluid supply to the piston and cylinder assembly is continuously reduced.

Abstract: A control system for an automobile air conditioner including an air blend door for adjusting the output of the air conditioner, a vacuum actuator including a hermetic chamber and a control member, the control member being connected to control the air blend door proportionally to the pressure within the chamber, a vacuum modulator including a first valve for exhausting air from the chamber to a vacuum reservoir, a second valve for emitting air from atmosphere to the chamber and a restriction member arranged at the entrance side of the chamber, a control circuit for providing a first electrical driving signal for operating the first valve so as to open and a second electrical driving signal for operating the second valve so as to open proportionally to the difference between a selected temperature within the automobile and the actual temperature within the automobile, an integrating circuit for providing integrated outputs of the first electrical driving signal and the second electrical driving signal with a ti

Abstract: A linearization circuit for use with servovalves for controlling reciprocating actuators. The circuit will maintain a substantially linear flow as a function of spool position from the servovalve regardless of the differential pressure across the servovalve orifices, for example the differential pressures which result from changing direction of movement of the controlled actuator under a high load. A differential pressure signal from the actuator, which correlates to differential pressure on the servovalve orifices is processed to provide a compensation signal combined with the normal control signal to achieve the desired output.

Abstract: A device for controlling the speed of movement of a mobile member relative to a fixed support member, said mobile member receiving its motion from first drive means is described. The main feature of said drive is that it comprises a speed transducer operated directly by said mobile member and arranged to supply an electrical signal proportional to said speed of movement of said mobile member to second comparison and processing means, to said second means there being also fed at least one electrical reference signal proportional to a predetermined value of said speed; the output signal of said second means, proportional to the difference between said signal of said transducer and said electrical reference signal, being fed to said first drive means.

Abstract: Servoactuator includes a pair of double-acting linear actuators providing for 360.degree. controlled rotation of an output shaft. The rotary motion of the ouput shaft is employed to sequence high pressure fluid flow and return for the same to the respective ends of the respective actuators so that both actuators continuously develop output force except for end stroke points. Shimmy damping may also be obtained by a bypass-damping valve which comprises a shuttle movable to a first position by high pressure fluid for controlled operation of the servoactuator and to a second position by removal of the high pressure fluid to direct fluid flow between the respective actuators through a damping orifice.

Abstract: A device for hydraulically lifting agricultural implements by a lifting jack, utilizing a pump with constant stroke volume and a stepless distributor. A flow pressure regulator of the pump is piloted by the pressure of the lifting jack, a downstroke valve is provided for lowering the implements, and a relay valve connects to the reservoir the piloting pressure of the regulator in the downward movement of the implements. A reducing valve fed by the flow circuit of the pump feeds at least one pilot electrovalve of the stepless distributor.

Abstract: In a system which provides feel-force to the control stick of an aircraft by means of hydraulic pressure, a fault indicating system which responds to excessive differences between desired and actual force in the actuator, only of a polarity in the same direction as concurrent stick motion, to separate pilot induced pressure excesses from force-system faults, is provided with directional sensitivity in the fault-indicating output logic. Excessive pressure errors in either direction of stick travel institute the monitoring of changes in stick position. Changes in stick position of an excessive magnitude are recognized as fault only if they occur in the same direction as the direction of excessive pressure error. A simple analog embodiment utilizes threshold detectors and a track store device; a dedicated-digital embodiment utilizes comparators, registers and a subtractor; and a computer embodiment utilizes a software routine.

Abstract: An electronic compensation circuit for a pneumatic load bearing bellows system closed on position, in which a servo valve provides pressure to the bellows to actuate the top of the bellows to move to a predetermined position in response to a control signal. The compensation circuit (42) cancels at least one load-variable system characteristic which, if not cancelled would cause system instability at system gain levels which are necessary for desired system response. The compensation circuit electronically provides a replacement system characteristic which permits the system to be operated at a gain level substantially higher than the gain level at which the uncompensated system goes unstable.

Abstract: The amount of axial movement of a plunger is controlled by a hydraulic servomechanism. The pressure in the hydraulic chamber of the servomechanism is controlled by opening and closing an inlet valve and outlet valve provided respectively at the inlet and outlet sides of the hydraulic chamber. When the difference value between the actual position and desired position of the plunger is greater than a first predetermined value, only one or the other of the inlet and outlet valves is energized. When the difference is intermediate the first predetermined value and a second predetermined value which is smaller than the former, the inlet and outlet valves are energized at different duty cycles. When the difference is smaller than the second predetermined value, the valves are both deenergized.

Abstract: A delaying device for a fluid system for operating a hydraulic motor (10) wherein electrically operated pilot valves (39,40) are actuated by limit switches (13,13') in the motor to control flow through pilot lines (37,38) into a control block (20) and then to and from the motor, said delaying device comprising a dashpot cylinder (46) connected to said pilot lines for momentarily continuing to supply fluid to said control block (20) after pilot valve (39 or 40) is shut off.

Abstract: A device for controlling both the displacement of, and the transmittal of force by, a longitudinally movable driving apparatus comprising a piston rod which is hydraulically movable inside a cylinder, an emitter and receiver for ultrasonic waves, which are transmitted between a movable and a fixed part of the driving apparatus, a logic circuit and a controllable source of force, said receiver being electronically connected to said controllable source of force via said logic circuit.

Abstract: An electrohydraulic servo system to actuate the power shaft of a fuel control system from the cockpit throttle including electrical devices responsive to the position of the throttle that actuates a hydraulic piston for moving the power shaft together with a backup system that assures a shaft position proportional to the throttle position. This permits the use of electrical lines from the cockpit to the engine rather than mechanical cables and linkages.

Abstract: A digitally controllable pneumatic linear actuator in which a moving piston driven by compressed air is initially decelerated by the pressure of compressed air applied to the both sides thereof in the course of its advancing movement toward a predetermined stop position and is then braked by a mechanical brake, thereby obviating failure of precise positioning of the piston due to the compressibility of air. The piston displacement is digitally detected, and the result of detection is fed back to a digital controller.

Abstract: This disclosure relates to a system for protecting pneumatic cylinders and diaphragm valves against failure of both electrical and pneumatic supplies. In the event of a failure of the air supply, the loss of air pressure is detected and all drives are locked in position. The position pneumatic feedback signal from the pneumatic cylinder diaphragm valve is then connected directly to a pneumatic memory. Thus when the air supply recovers, the pneumatic memory will be equal to the instantaneous position of the pneumatic cylinder or diaphragm valve.In the event of an electrical failure, a solenoid valve interrupts the flow of the pneumatic signal from an electropneumatic transducer to the pneumatic memory, so that the air cylinder or valve is directly connected to the pneumatic memory. By selectively energizing a pair of solenoid valves connected to the memory, the operator using an emergency d.c.

Abstract: In a hydraulic actuator such as those used in multiple degree freedom motion bases for aircraft simulators, a secondary force sensitive hydraulic servo loop is added in parallel to the primary position feedback servo loop with the secondary loop having a servo valve possessing substantially greater band pass and less capacity than the main valve used in the first servo loop. Force feedback from the control actuator is applied degeneratively to the smaller servo valve, thereby reducing noise and jitter caused by responses of the system outside the response of the primary servo loop. The response of the main servo loop which control the position of the actuator is low pass and restricts response to the full desired band pass of operational frequencies. The secondary loop is high pass and is shaped to prevent degeneration of operational frequencies while providing optimum gain and phase for the degeneration of the unwanted high frequency portion of the band wherein noise and jitter reside.

Abstract: A time modulated position controller is provided comprising a hydraulic actuator having a cylinder and a piston slidably disposed in the cylinder thus defining a chamber within the cylinder. An electric solenoid valve functions upon actuation to permit fluid communication from a source of fluid pressure to the cylinder chamber while, conversely, upon deactuation of the solenoid valve, the valve functions to exhaust fluid from the cylinder chamber. A position transducer, which generates a signal in response to the axial position of the piston within the cylinder, is coupled to one input of a differential amplifier while a control line, having an analog signal is coupled to the second input of the differential amplifier. The error output from the differential amplifier is time modulated to produce a square wave with a variable duty cycle which in turn is used to activate the solenoid valve.