US3834279A - Method and device for electrohydraulic control of a hydraulic actuator - Google Patents

Method and device for electrohydraulic control of a hydraulic actuator Download PDF

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Publication number
US3834279A
US3834279A US00173525A US17352571A US3834279A US 3834279 A US3834279 A US 3834279A US 00173525 A US00173525 A US 00173525A US 17352571 A US17352571 A US 17352571A US 3834279 A US3834279 A US 3834279A
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Prior art keywords
pressure
spool
servovalves
control
pressure medium
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US00173525A
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English (en)
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H Boss
H Butschek
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Airbus Defence and Space GmbH
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Messerschmitt Bolkow Blohm AG
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B21/00—Common features of fluid actuator systems; Fluid-pressure actuator systems or details thereof, not covered by any other group of this subclass
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B64—AIRCRAFT; AVIATION; COSMONAUTICS
    • B64C—AEROPLANES; HELICOPTERS
    • B64C13/00—Control systems or transmitting systems for actuating flying-control surfaces, lift-increasing flaps, air brakes, or spoilers
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B18/00—Parallel arrangements of independent servomotor systems

Definitions

  • the apparatus has a plurality of electrohydraulic servovalves each controlled by separate electrical input channels and connected to a central pressure medium source.
  • the control further has a control spool triggered by the servovalve to control the actuator and a hydraulic logic system for monitoring errors in the servo output signal.
  • the positioning land of the control spool is acted upon on the one side by one group of signals consisting of the combined output signals of the same sign from one selected group of servovalves and is acted upon on the other side by the central pressure medium supply while the remaining servovalve signals are applied separately to a hydraulic logic system including a comparator and switching logic means.
  • the invention relates to a method and a device for the electrohydraulic control of a hydraulic actuator in the form of a redundant servovalve circuit with switching and monitoring logic, having a multiplicity of electrohydraulic servovalves, each controlled by separate electrical input channels and connected to a central pressure medium source, and having further a control spool triggered by the servovalves to control the actuator and a hydraulic logic system for error monitoring of the servovalve output signals.
  • hydromechanical circuits For monitoring redundant electrohydraulic actuators, two types of hydromechanical circuits are used at the pressure ports of the servovalves (electrohydraulic servovalves and electrohydraulic amplifiers):
  • servovalve circuits Redundant servovalve circuits.
  • the servovalve pressure ports are arranged in such a way as to permit control of the actuator and the detection of errors by comparison of the pressures through use of a comparator. If the pressure difference between two servovalves exceeds a prescribed value, the comparator initiates a reaction in the switching and monitoring logic.
  • the invention attains this objective by employing a method in which the positioning land of the control spool is acted upon, on the one side, by the one signal group consisting of the combined servovalve output signals of the same sign and, on the opposite side, by the central pressure media supply, while the remaining free servovalves signals are applied individually to the hydrologic system.
  • a device having a multiplicity of electrohydraulic servovalves, a control spool triggered by the servovalves to control a hydraulic actuator and a hydrologic system wherein the one group of all servovalve outputs of the same sign is conducted to one side of the positioning land of the control spool, and the other group of outputs is connected separately to the hydrologic system and, further, wherein, the other side of the control spool positioning land is connected with the central pressure medium source.
  • One illustrative embodiment of the invention provides, as servovalves, two single stage jet-pipe valves attached to a central pressure medium source, further, a control spool having one positioning land, two control lands and an attached comparator responding from two sides, said comparator having a switching device to shut off the central pressure medium supply, each of the two jet-pipe valve outputs of the same sign jointly acting upon one side of the positioning land, the central pressure medium supply acting upon the other side of the positioning land, and the two other outputs of the jet-pipe valves acting upon both sides of the comparator, the displacement of which triggers the switching device.
  • the positioning land mentioned in the present description can readily be divided into two individual lands, in which case, only one side of each land is acted upon for the purpose of displacing the control spool.
  • Another illustrative embodiment of the invention provides that two such devices be connected in parallel to a common pressure medium supply, in which case, both control spools are rigidly, mechanically connected to each other and the output signals trigger the switching devices indirectly via an AND-gate and a further switch for cutting in a safety device or to cut out the central pressure medium supply.
  • a circuit of this kind still permits control of the control valve even after the shutoff of two servovalves by one of the switching devices.
  • three electrohydraulic servovalves are provided whose two free outputs not used to trigger the common control spool, trigger a system of three hydraulic comparators whose outputs are connected via a triple AND-gate to a switch for cutting off the central pressure medium supply or to any other safety circuit.
  • a circuit of this kind can survive the failure of one servovalve. Not until a failure of a further servovalve do all three comparators deflect and activate, via the AND- gate, the switch for any safety circuit.
  • FIG. 1 An electrohydraulic actuator with two servovalves acting upon one control spool;
  • FIG. 2 two systems according to FIG. 1 connected in parallel;
  • FIG. 3 An electrohydraulic actuator with three servovalves acting upon one control spool
  • FIGS. 4-16 special switching logic designs as are usable in the devices shown in FIGS. 1 and 2;
  • FIG. 17 a redundant version of an AND gate.
  • the two servovalve pressure ports 3 of the same signal are joined to a common line 4 which is connected to chamber 5 in control spool housing 6.
  • Chamber 7 in control spool 6 connects, through line 9, with the central pressure medium supply 8, which also supplies both servovalves through lines 10 and 11.
  • Both servovalve pressure ports 12 are compared with each other by a comparator 13.
  • the comparator 13 deflects and connects lines 20 and 23 through orifice 25.
  • Lines 20 and 23 represent the pressure potential between the pressure medium inflow and drain.
  • the pressure in line 24 changes, thus causing a response in switching logic 26.
  • This serves to trigger a safety circuit 43A, to energize a warning device or to shut off the central pressure supply 8. In this way, an error at the pressure port of both servovalves can be detected and eliminated.
  • FIG. 2 two control channels, each in accordance with the device shown in FIG. 1, are connected in parallel.
  • the two control spools 31 are coupled together by a connecting rod 30. Both channels are connected to the same pressure medium supply 32 for the servovalves 33, and to the same working medium supply 34.
  • both control spools 31 are balanced, i.e., the forces acting upon the positioning land surfaces 35 and 36 cancel each other out, the same as do the forces acting on the positioning land areas 37 and 38.
  • the actuator ports of control spool 31 work upon a hydraulic actuator, likewise redundant, but not shown in the drawing.
  • Each of the two comparators 40 associated with the signal channels triggers, for its part, a switching logic 41 to shut off the central pressure medium supply 32.
  • switch 433 When both switching logic units 41 deactivate the associated signal channels, switch 433 is tripped by AND-gate 42 for some kind of safety switching operation (for example, shutting off the actuator controlled by control spool 31).
  • the circuit shown in FIG. 2, with redundant pressure medium input, can survive the failure of one servovalve or one pressure medium input.
  • FIG. 3 displays the use of the principle of the circuit of FIG. 1 as applied to three servovalves 51.
  • the outlet ports 53 of the same sign work through common line 52 upon one positioning land 54 of control spool 62, while the other positioning land is acted upon by the pressure medium supply 56.
  • the drain, or return line, is indicated by 57.
  • the circuit represented in FIG. 3 can be doubled in accordance with F IG. 2, thus forming a circuit with six servovalves.
  • the switching logics outlined hereinafter are embodiments, the general function of which is the same as that in 26, shown in FIG. 1, and 41, shown in FIG. 2.
  • the circuits vary from each other in the arrangement and number of solenoid valves and in having parallel or series connection of switching logic 41 with AND-gate 42 in the case of the duo-duplex circuit.
  • Switching logic 41 and AND- gate 42 lie in parallel when the AND element is connected to line 24 and simultaneously respond to the switching logic controlled by line 24. Switching logic 41 and AND element 42 lie in series when the AND element is not connected to line 24 and is first triggered by the switching logic.
  • the switching logics are connected to the pressure medium inlet 65 and drain 66. Three connections are provided for the switching function; line 67 leads to comparator 13 (FIG. 1) or 40 (FIG. 2), line 68 a switch 43A (FIG. 1) or to AND element 42 (FIG. 2) and the servovalves are supplied with pressure medium from line 69.
  • FIGS. 4 and 5 show a switching logic with an active solenoid valve 70 in the inlet and connected in series to the AND element 42 or switch 43A.
  • the active solenoid valve 70 has two switching states; in the excited state, it opens the connection to the pressure medium drain 66.
  • solenoid valve 70 is excited and spool 71 (which acts as a further comparator) is in the extreme right-hand position, thus connecting outlets 67, 68 and 69 with pressure medium inlet 65.
  • spool 71 which acts as a further comparator
  • solenoid valve 70 When solenoid valve 70 is subsequently subjected to continuous energization, lines 67, 68 and 69 are again connected with pressure medium inlet 65 and servovalve functioning is restored. Further excitation of solenoid valve 70 in FIG. 4 results in pressure in line 67 and, due to the elasticity and/or the compressibility of the pressure medium, volume is consumed, which flows through orifice 74. i
  • AND-gate 78 is in the left-hand end position and the bypass is open, so that the pressure medium volume can flow into line 61 by bypassing orifice 74 and no pressure differential can occur between lines 79 and 67 that could slide spool 75 into the left-hand end position.
  • AND-gate 78 is in the right-hand end position and the bypass is again blocked.
  • Spool 71 and 75 can be brought into the right-hand end position by brief interruption in the excitation of solenoid valve 70, only when the varying pressures at the servovalve outlets, which caused deflection of the comparator, have again become uniform. Otherwise, line 67, downstream from restrictor orifice 74, does not fill.
  • FIG. 6 shows a switching logic with an active solenoid valve in the inlet and parallel connection to the AND- gate.
  • Active solenoid valve 80 has two switching states; in the energized state, it opens the connection to the pressure medium inlet 65 and in the de-energized state, it opens the connection to the pressure medium drain 66; When the servovalves are operating, solenoid valve 80 is excited and spool 81 is in the right-hand end position and connects outlets 67, 68 and 69 with pressure medium inlet 65.
  • switching off by the comparator through line 67 and switching on and off by the active solenoid valve 80 will now be considered.
  • Switching on by the active solenoid valve Cancellation of servovalve functioning can be initiated by the comparator or by active solenoid valve 80. If the switching off is effected by active solenoid valve 80, the functioning of the servovalves is restored by excitation of solenoid valve 80. If switching off is accomplished by the comparator, the functioning of the servovalves is restored by a brief interruption of energization of solenoid valve 80. During the brief interruption of excitation, line 86 is connected with pressure medium drain 66 and spring 87 moves spool 81 into the righthand end position.
  • Spool 81 can be brought into the right-hand end position by brief interruption in the energization ofsolenoid valve 80, only when the varying pressures at the servovalve outlets, which caused the deflection of the comparator, have again become uniform. Otherwise, lines 67 and 68, downstream from restrictor orifice 82, will not fill.
  • FIG. 7 shows a switching logic with an active solenoid valve in the drain and connected in parallel to the AND element.
  • the active solenoid valve 90 has three switching states. In the unexcited state, it opens all connections to pressure medium drain 66. When positively excited, solenoid valve 90 blocks the connection between line 91 and pressure medium drain 66 through delay spool 98. In the case of negative excitation, solenoid valve 90 blocks all connections to pressure medium drain 66. When the servovalves are operating, solenoid valve 90 is positively excited, spool 98 is in the righthand end position and connects outlets 67, 68 and 69 with pressure medium inlet 65.
  • initiation by means of the comparator as well as switching on and switching off by active solenoid valve 90 will now be considered.
  • spool 93 When in the left-hand end position, spool 93 connects outlets 67, 68 and 69 with pressure medium drain 66, and functioning of the servovalves is irreversibly stopped due to connection with pressure medium drain 66. In this position, orifice 94 prevents a short circuit between pressure medium inlet and drain.
  • Switching on by the active solenoid valve Switching off of the servovalves can be initiated by the comparator or by active solenoid valve 90. If deactivation is accomplished by the comparator, spool 93 remains in the left-hand end position until either the pressure medium flow at 65 is shut off from the outside, or, through brief negative excitation of solenoid valve 90, all connections to the pressure medium inlet 65 are temporarily blocked. When the pressure medium flow at 65 is shut off from the outside, spring 95 slides spool 93 into the right-hand end position again. When solenoid valve 90 is negatively excited, and all connections to pressure medium drain 66 are blocked, line 67 fills again through restrictor orifice 94, and the spool is slid into the right-hand end position. While solenoid valve 90 is closing all the connections to pressure medium drain 66 and line 67 is being filled, check valve 96 opens, and delay spool 92 is slid into the upper end position, thus blocking the connection between line 67 and solenoid valve 90.
  • solenoid valve 90 is again positively excited, the connection from line 67 through delay spool 92 remains blocked during the switching operation, until connection 97 is blocked, since the delay spool is still in the upper end position. Not until spring 98 has displaced the stroke volume of delay spool 92, via restrictor orifice 100, is the connection from line 67 to line 97 open again.
  • the displacement volume of delay spool 92 and the flow through restrictor orifice 100 are coordinated with the switching time of the solenoid valve from negative to positive excitation.
  • Spool 93 can be brought into the right-hand end position by brief negative excitation of solenoid valve 90, only when the varying pressures at the servovalve oulets, which caused the deflection of the comparator, have again become uniform. Otherwise, line 67 does not fill through restrictor orifice 94.
  • FIG. 8 shows a switching logic with an active solenoid valve in the drain and connected in parallel to the AND element.
  • the circuit functions as in FIG. 7. However, outlet 68 to the AND-gate with the comparator is connected to the same space as line 67.
  • FIG. 9 shows a switching logic with an active solenoid valve in the inlet, a passive solenoid in the drain and parallel connection to the AND element.
  • Active solenoid valve 101 has two switching states. In the energized state, it blocks the connection to pressure medium drain 66 and in the de-energized state, it blocks the connection to pressure medium inlet 65.
  • Passive solenoid valve 102 also has two switching states. In the unexcited state, it opens the connection to pressure medium drain 66 and in the excited state, it blocks this connection. When the servovalves are operating, active solenoid valve 101 is excited and passive solenoid valve 102 is unexcited. Spool 103 is in the right-hand end position and connects outlets 67, 68 and 69 with pressure medium inlet 65. In order to describe the functioning of the switching logic in FIG. 9, switching off by the comparator and by the active solenoid valve 101 as well as switching on by means of passive solenoid valve 102 will now be considered.
  • Deactivation of servovalve functioning can be initiated by deflection of the comparator, by discontinuing excitation of the active solenoid valve 101, or stopping of the pressure medium flow at 65 from the outside. In all cases of deactivation, spool 103 is in the left-hand end position.
  • the active solenoid valve In order to switch on, the active solenoid valve must first be excited and the connection to the pressure medium inlet 65 must open. Solenoid valve 102 is then briefly energized and line 107 to pressure medium drain 66 is blocked. During energization of solenoid valve 102, line 67 is filled through restrictor orifice I and spool 103 is pushed against spring 104 into the right-hand end position.
  • Spool 103 can be brought into the right-hand end position by brief excitation of solenoid valve 102, only when the varying pressures at the servovalve outlets, which caused the deflection of the comparator, have again become uniform. Otherwise, line 67 will not fill through restrictor orifice 105.
  • FIG. 10 shows a switching logic with an active solenoid valve in the inlet a passive solenoid valve in the drain and connected in parallel to the AND element.
  • FIG. 11 shows a switching logic with an active and a passive solenoid valve in the drain and connected in series to the AND element.
  • Active solenoid valve 108 has two switching states. In the energized state, it blocks the connection to pressure medium drain 66 and in the de-energized state, it opens the connection to pressure medium drain 66. Passive solenoid valve 109 also has two switching states. In the de-energized state, it opens the connection to pressure medium drain 66 and in the energized state, it blocks this connection. When the servovalves are operating, active solenoid valve 108 is energized and passive solenoid valve 109 is de-energized.
  • Spool 121 is held in the left-hand end position by the pressure in line 67 and connects outlets 67, 68 and 69 with pressure medium inlet 65.
  • switching off by the comparator and by the active solenoid valve 108 as well as switching on by the passive solenoid valve 109 will now be considered.
  • Deactivation of the servovalves can be initiated by deflection of the comparator, by discontinuing energization of the active solenoid valve 108 or by shutting off the pressure medium flow at 65 from the outside. In all cases, spool 121 is held in the left-hand end position by spring 110. In order to switch on after all types of deactivation, active solenoid valve 108 must first be energized and the connection to the pressure medium drain blocked. The passive solenoid valve is then briefly energized and blocks the connection to pressure medium drain 66.
  • line 67 fills through restrictor orifice 111 and spool 121 is slid into the right-hand end position.
  • Spool 121 can be brought into the right-hand end position by brief energization of solenoid valve 109, only when the varying pressures at the servovalve outlets, which caused the deflection of the comparator, have again become uniform. Otherwise, line 67 will not fill through orifice 111.
  • the circuit in FIG. 12 functions the same as the one in FIG. 11. However, outlet 68 to the AND-gate with the comparator is connected to the same space as line 67.
  • FIG. 13 shows a switching logic with an active solenoid valve in the drain and a passive solenoid valve in the inlet and connected to the AND-gate in series.
  • Active solenoid valve 1 12 has two switching states. In the energized state, it blocks the connection to pressure medium drain 66 and in the de-energized state, it opens the connection. Passive solenoid valve 1 13 also has two switching states. In the de-energized state it blocks the connection to the pressure medium inlet 65 and in the energized state, it reopens this connection.
  • active solenoid valve 112 is de-energized. Spool 114 is held in the right-hand end position by the pressure in line 67 and connects outlets 67, 68 and 69 with pressure medium inlet 65.
  • Deactivation of the servovalves can be initiated by deflection of the comparator, by discontinuing energization of active solenoid valve 112, or by stopping the flow of pressure medium at 65 from the outside. In all cases, the spool is held in the left-hand end position by spring 115.
  • active solenoid 112 In order to switch on, following all types of deactivation, active solenoid 112 must first be energized and the connection to the pressure medium drain 66 blocked. The passive solenoid valve 113 is then energized briefly and opens to the pressure medium inlet 65, which causes the spool to slide into the righthand end position against spring 115.
  • Spool 114 can be brought into the right-hand end position by brief energization of the passive solenoid valve, only when the varying pressures at the servovalve outlets, which caused the deflection of the comparator, have again become uniform.
  • FIG. 14 shows a switching logic with an active solenoid valve in the drain and a passive solenoid valve in the inlet and connected in parallel to the AND-gate.
  • FIG. 15 shows a switching logic with a passive solenoid valve in the drain and connected in series to the AND element.
  • Passive solenoid valve 117 has two switching states. In the de-energized state, it opens the connection to pressure medium drain 66 and in the energized state, it blocks this connection. When the servovalves are operational, passive solenoid valve 117 is de-energized and spool 118 is in the right-hand end position and connects outlets 67, 68 and 69 with pressure medium inlet 65. In order to describe the functioning of the switching logic in FIG. 15, switching off by the comparator and switching on by the passive solenoid valve will now be considered. Switching off with the solenoid valve is not possible. If, in spite of error-free servo-valves with uniform outlet pressures, switching off is to be effected, then the servovalves must receive artificial error signals that cause a pressure difference at the pressure outlets and thus, a deflection of the comparator.
  • Deactivation of the servovalves can be initiated by deflection of the comparator or shutoff of the pressure medium flow at 65 from the outside. In both cases of deactivation, spool 118 is in the left-hand end position.
  • passive solenoid valve 117 is briefly energized, thus blocking the connection to pressure medium drain 66.
  • line 67 fills through restrictor orifice 120 and spool 118 is slid into the left-hand end position against spring 119.
  • Spool 1 18 can be brought into the right-hand end position by brief energization of passive solenoid valve 117, only when the varying pressures at the servovalve outlets, which caused the deflection of the comparator, have again become uniform. Otherwise, line 67 will not fill through restrictor orifice 120.
  • FIG. 16 shows a switching logic with a passive solenoid valve in the drain and connected in parallel to the AND-gate.
  • the circuit in FIG. 16 functions the same as the one in FIG. 15. However, the outlet 68 to the AND-gate with the comparator is connected to the same space as line 67.
  • FIG. 17 shows the redundant version of an AND-gate shown schematically as 42 in FIG. 2, wherein each of the lines 68 has a switching logic as in FIGS. 4 through 16.
  • each of the lines 68 has a switching logic as in FIGS. 4 through 16.
  • the pressure coming from line 68 and existing in front of spools 124 and 125 is reduced by check valve 130, and spools 124 and 125 are moved into the right-hand end position, as is also true of spools 122 and 123, in order to trigger a safety switch 128.
  • the switching logics in FIGS. 4 through 16 are designed so that, in case of a connection between pressure medium inlet and drain through line 131, a short circuit will not occur. It is the purpose of check valves 129 and 130 and lines 132 and 133 to prevent the connection of two switching logics through line 131 until one of the two AND-gates moves into the righthand end position through connection of both lines 68 with the pressure medium drain. If, for example, only line 68 from spool 122 is connected with-the pressure medium drain, then the connection to the pressure medium inlet if spool 124 and line 132 via check valve 129 remains blocked.
  • a device for effecting an electrohydraulic control of said hydraulic actuator comprising:
  • servovalve circuit means including at least a pair of identical electrohydraulic servovalves each having an energized and an unenergized condition and each servovalve including at least a pair of output terminals thereon, each servovalve producing a first pressure signal at one of said pair of output terminals and a second pressure signal at the other one of said pair of output terminals dependent upon the condition thereof;
  • said fourth pressure signal responsive means in said hydraulic logic system includes pressure responsive valve means having a second outlet port and third and fourth inlet ports, one of said third and fourth inlet ports being connected with said first outlet port and said fourth pressure signal and acting on one side of said pressure responsive valve means, the other of said third and fourth inlet ports being connected to said pressure source means and to an opposed side of said pressure responsive valve means, and active solenoid valve means for controlling the transmission of a pressure pulse from said pressure source means to said other of said third and fourth inlet ports, said pressure responsive valve means being responsive to a change in pressure applied thereto by either one or both of said fourth pressure signal and the pressure signal from said other of said third and fourth inlet ports.
  • said first pressure comparator means includes means defining an elongated housing having a spool slideably supported therein, said first and second inlet ports being provided at spaced locations on said housing on opposite sides of said spool.
  • a device including centering means for mechanically centering said spool in said housing means of said first pressure comparator means.
  • said pressure responsive valve means includes means defining an elongated housing having a spool slideably supported therein, said third and fourth inlet ports being provided at spaced locations on said housing on opposite sides of said spool, the position of said spool in said housing controlling the transmission of pressure from the other of said third and fourth inlet ports to said second outlet port.
  • said active solenoid valve means includes means defining a chamber having spaced openings, a drain connection defined by one of said openings and a valve member movable in said chamber between said spaced openings to selectively block one of said spaced openings and thereby control whether said chamber is pressurized or depressurized.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Automation & Control Theory (AREA)
  • Aviation & Aerospace Engineering (AREA)
  • Fluid-Pressure Circuits (AREA)
  • Magnetically Actuated Valves (AREA)
  • Servomotors (AREA)
US00173525A 1970-08-21 1971-08-20 Method and device for electrohydraulic control of a hydraulic actuator Expired - Lifetime US3834279A (en)

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Application Number Priority Date Filing Date Title
US05/490,132 US3987702A (en) 1970-08-21 1974-07-19 Method and device for electrohydraulic control of a hydraulic actuator

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE2041681A DE2041681C2 (de) 1970-08-21 1970-08-21 Verfahren und Einrichtung zur elektrohydraulischen Ansteuerung eines hydraulischen Stellantriebes

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US05/490,132 Division US3987702A (en) 1970-08-21 1974-07-19 Method and device for electrohydraulic control of a hydraulic actuator

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US00173525A Expired - Lifetime US3834279A (en) 1970-08-21 1971-08-20 Method and device for electrohydraulic control of a hydraulic actuator

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US (1) US3834279A (enExample)
DE (1) DE2041681C2 (enExample)
FR (1) FR2103437B1 (enExample)
GB (1) GB1344373A (enExample)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4538504A (en) * 1983-11-18 1985-09-03 General Electric Company Fail-safe servovalve system

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2615345C3 (de) * 1976-04-08 1984-05-10 Liebherr-Aero-Technik Gmbh, 8998 Lindenberg Selbstüberwachter Stellantrieb, insbesondere für Steuerruder von Flugzeugen
US4143583A (en) * 1977-09-23 1979-03-13 Pneumo Corporation Redundant EHV fault detector

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3084676A (en) * 1958-07-15 1963-04-09 Erich Herion Safety control apparatus for operating pressure-actuated devices
US3391611A (en) * 1965-08-23 1968-07-09 Bell Aerospace Corp Hydraeric control system
US3496836A (en) * 1968-01-02 1970-02-24 Bell Aerospace Corp Redundant control system having fail-operate fail-neutral and channel emergency select
US3667344A (en) * 1969-11-25 1972-06-06 Hobson Ltd H M Position control servo systems

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3084676A (en) * 1958-07-15 1963-04-09 Erich Herion Safety control apparatus for operating pressure-actuated devices
US3391611A (en) * 1965-08-23 1968-07-09 Bell Aerospace Corp Hydraeric control system
US3496836A (en) * 1968-01-02 1970-02-24 Bell Aerospace Corp Redundant control system having fail-operate fail-neutral and channel emergency select
US3667344A (en) * 1969-11-25 1972-06-06 Hobson Ltd H M Position control servo systems

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4538504A (en) * 1983-11-18 1985-09-03 General Electric Company Fail-safe servovalve system

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GB1344373A (en) 1974-01-23
DE2041681B2 (de) 1972-03-16
DE2041681A1 (enExample) 1972-03-16
DE2041681C2 (de) 1978-06-22
FR2103437A1 (enExample) 1972-04-14
FR2103437B1 (enExample) 1975-07-11

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