US3702575A

US3702575A - Redundant hydraulic control system for actuators

Info

Publication number: US3702575A
Application number: US148756A
Authority: US
Inventors: Richard A Campbell
Original assignee: National Aeronautics and Space Administration NASA
Current assignee: National Aeronautics and Space Administration NASA
Priority date: 1971-06-01
Filing date: 1971-06-01
Publication date: 1972-11-14
Anticipated expiration: 1989-11-14

Abstract

A unique combination of three main valves to supply hydraulic pressure to a conduit pattern including four secondary valves for the assured operation of a hydraulic actuator. All the secondary valves are under the command of a comparator and logic controller which is capable of stopping the hydraulic flow from a valve that failed and allowing the hydraulic flow to continue with the other operative valves. The control system permits two single point failures and still allows operation with no degradation in performance.

Description

' United States Patent Campbell [54] REDUNDANT CONTROL SYSTEM FOR ACTUATORS [72] Inventor: Richard A. Campbell, Huntsville,

Ala.

[73] Assignee: The United States of America as represented by the Administrator of the National Aeronautics and Space Administration [22] Filed: June 1, 1971 [21] Appl.No.: 148,756

[52] US. Cl. ..91/363 A, 91/363 A, 91/448 [51] Int. Cl. ..Fl5b 9/03, Fl5b 9/04 [58] Field of Search ..9l/363 A, 363 R, 387, 448, 91/32 [56] References Cited UNITED STATES PATENTS 7 3,270,623 9/1966 Garnyost et al. .....9l l387 COMPARATOR AND LOGIC CONTROLLER [451 Nov. 14, 1972 Asche ..91/363 A I Wood ..91/363 A Primary Examiner-Paul E. Maslousky AttorneyL. D. Wofford, Jr., W. H. Riggins and John R. Manning ABSTRACT A'unique combination of three main valves to supply hydraulic pressure to a conduit pattern including four secondary valves for the assured operation of a hydraulic actuator. All the secondary valves are under the command of a comparator and logic controller which is capable of stopping the hydraulic flow from a valve that failed and allowing the hydraulic flow to continue with the other operative valves. The control system permits two single point failures and still allows operation with no degradation in performance.

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sneznura VALVE I SHUTTLE VALVE D INVENTOR RICHARD A. CAMPBELL A T TORNE Y PATENTEDnnv 14 I972 SHEET 2 BF 3 N mmjgm mm @0233 mm 2386 8 3062 5 wziutsm mzfimmmoo 8| momma 29:8. 134E328 INVENTOR RICHARD A. CAMPBELL ATTORNEY REDUNDANT HYDRAULIC CONTROL SYSTEM FOR ACTUATORS ORIGIN OF THE INVENTION The invention described herein was made by an em- 5 ployee of the United States Government and may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

BACKGROUND OF THE INVENTION popular method is to supply a plurality of servovalves all operating simultaneously and in parallel. Each servovalve having its own independent feedback loop so that if any one or two servovalves should fail the remaining valves simply overpower the failed unit and maintain control of the actuator load. The disadvantages of this method are that the failed components are not removed from the active systems and thus, caused degradation in system performance. Also, the multitude of valves increase cost and weight and it is difficult to establish the pre-operation status of the system.

It has been proposed that redundancy be achieved by providing a plurality of complete systems, each one including a main hydraulic actuator. However, having hydraulic fluid flowing through all the hydraulic actuators simultaneously results in a significant power loss, and the many control valves and main hydraulic actuators results in considerable additional weight and cost.

BRIEF DESCRIPTION OF THE INVENTION The invention provides for three main servovalves to supply and return hydraulic pressure from a main system to a conduit pattern including four secondary shuttle valves for the assured delivery of the hydraulic pressure to a principal hydraulic actuator. All the secondary valves are under the command of a comparator and logic computer controller which is capable of stopping the hydraulic pressure flow from a failed main servovalve or a secondary valve to reroute the flow through the conduit pattern and maintain hydraulic pressure on the actuator.

Accordingly, it is an object of the present invention to provide adequate hydraulic control reliability at the minimum weight and cost.

Other and further objects, uses, and advantages of the present invention will become apparent as the description proceeds.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 schematically illustrates the redundancy control system of the present invention.

FIG. 2 is a functional block presentation of the controller.

FIG. 3 is a diagram of the switching logic for the controller.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENT Referring now to FIG. 1 wherein is illustrated a single principal hydraulic actuator 20 suitable for providing alignment control of a rocket engine or control of aerodynamic surface on an airplane. The hydraulic actuator 20 is itself considered extremely reliable due to its large size and forces acting upon it. The present invention is directed therefore, toward assuring that the control system for the actuator 20 is at least as reliable by being able to withstand any two single point failures and still operate with no degradation of performance.

The redundant control means for the actuator 20 begins with three servovalves 22-1, 22-2, and 22-3 all of which operate from a command input signal, simultaneously, from a suitable manned or automatic master control (not shown). Each servovalve 22-1, 22-2, 22-3 is connected to the main hydraulic pressure system consisting of supply and

return ducts

28 and 30, respectively. Each servovalve is a standard type having a torque motor operated by the command input signal and a second stage hydraulic spool which regulates the fluid communication between the supply and

return ducts

28 and 30, and the servovalve exit ports to cause the proper fluid activation of the actuator 20.

The particular servovalve 22-1, 22-2, or 23-3 which controls the hydraulic actuator 20 is determined by the four secondary shuttle valves A, B, C, and D, which are connected together in a unique conduit pattern. The spool of each shuttle valve A, B, C and D is maintained in a normal upper position by the use of a preloaded spring but the spool may be shifted by hydraulic pressure from the main hydraulic pressure supply 28 applied to the upper land of each spool by a

controller

29A, 29B, 29C, and 29D. As shown secondary valve A has a eight ports and a spool with five lands, secondary valve B has four ports and a spool with three lands, secondary valve C has four ports and a spool with five lands, and secondary valve D has four ports and a spool with three lands.

Servovalve 22-1 supplies hydraulic pressure through supply conduits l and IR to the two upper entry ports of shuttle valve A. Servovalve 22-2 supplies hydraulic pressure through supply conduits 2 and 2R to the two lower entry ports of shuttle valve A. As shown the upper two lands of the spool of shuttle valve A are in a normal position which permits hydraulic pressure to pass to the two upper exit ports which are connected to third supply conduits 3 and SR.

Also, the lower two lands of the spool of the shuttle valve A are in a normal position which blocks the pressure from the lower exit ports which are connected to the fourth supply conduits 4 and 4R.

The third conduits 3 and SR are connected to fifth supply conduits 5 and SR, which divide into two branches, the upper branch connected to the two entry ports of shuttle valve B and the lower branch joined to the upper two entry ports of shuttle valve D.

The fourth conduits 4 and 4R, also are connected to the fifth supply conduits 5 and SR, respectively.

Sixth supply conduits 6, 6R are divided into two branches, the upper branch connects with the two exit ports of shuttle valve B and the lower branch connects with the upper two exit ports of shuttle valve D.

The normal position of the spool of shuttle valve B is such that its upper two lands blocks the passage of hydraulic pressure from the upper branch of conduits 5 and SR to the upper branch of conduits 6 and 6R. The normal position of the spool of shuttle valve D is such that its upper three lands are positioned to allow the passage of hydraulic pressure from the lower branch of conduits 5 and SR, to the lower branch of conduits 6 and 6R.

The sixth conduits 6 and GR connect with the seventh supply conduits 7 and 7R of the actuator 20.

The third servovalve 22-3 supplies hydraulic pressure through the eighth supply conduits 8 and SR to the two entry ports of shuttle valve C. Ninth supply and returned conduits 9 and 9R connect to the two exit ports of shuttle valve C to the two lower entry ports of shuttle valve D. Tenth supply conduits l0 and 10R connect the two lower exit ports of shuttle valve D to the sixth conduits 6 and 6R.

The normal position of the spool of shuttle valve C is such that hydraulic pressure is permitted to pass from

eighth conduits

8 and 8R to ninth conduits 9 and 9R. The normal position of the spool of shuttle valve D is such that its lower lands blocks the passageway from the ninth conduits 9 and 9R to the tenth conduits 10 and 10R.

Each of the three main servovalves 22-1, 22-2, 22-3, are operated simultaneously by a signal along line 44 from a command control (not shown). This signal is also inputed into a comparator and logic controller 50. The position of the hydraulic actuator is determined by a transducer 44 connected thereto which gives a signal to the controller 50, along line 45, indicative of the actual position of the actuator piston shaft 46. Also, the position of the spools of each of the shuttle valves A, B, C, D, are determined by

limit switches

48A, 48B, 48C, and 48D associated with a shaft secured to the bottom of the spool of each valve. A shift in the spool downward will cause the limit switch to trip and provide a signal to the controller 50 of the new position of the spool for that valve.

FIG. 2 illustrates the functions of the controller in comparing the desired math model 51 position of the hydraulic actuator 20 with the actual physical position 52 of the actuator, and computing the error difference and providing it to a comparator 53. When the error of the position exceeds some predetermined limit (2 set on the comparator 53, a failure is considered to have occurred, and the switching logic 54 is activated to remove the failed component from the system.

FIG. 3 illustrates the switching logic of the controller 50. For example, should servovalve 22-1 have failed, and

limit switches

48D and 48A are both in off, and thus have not been tripped by movement of the shuttle valves D and A, the controller will activate pressure controller 29A to shift the spool of shuttle valve A and remove servovalve 22-1 from the using system, and allow servovalve 22-2 to control the actuator 20.

Should servovalve 22-2 now fail, and limit switch 480 is in its normal off position, and switch 48A is in its shifted on position, then the controller will activate pressure controller 29D to shift the spool of shuttle valve D and thereby remove servovalve 22-2 from the using system and allow servovalve 22-3 to control the actuator 20.

Other failures of the components which could be solved by the novel arrangement of servovalves and shuttlevalves should now be apparent and the logic for these solutions are incorporated into the controller 50. For example, if shuttle valve A failed by shifting its spool, then no action is necessary by the controller 50 because main servovalve 22-2 would pick up the control of the actuator.

Thus, it is apparent that a novel arrangement of valves and conduits are used in a control of a hydraulic actuator to obtain significant cost and weight savings and sufficient fail-safe redundancy. Obviously, many modifications and variations of the disclosed system are possible. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced other than as specifically described.

I claim:

1. A redundant control system for a hydraulic actuator comprising:

a principal hydraulic actuator having a movable shaft for providing essential movement to a member,

a pair of control hydraulic supply conduits joined to said actuator for supplying fluid thereto,

main hydraulic supply and returned means providing a primary source of hydraulic fluid pressure,

a first main valve means connecting said main hydraulic supply and returned means to a first pair of supply conduits so either one of said first supply conduits may supply hydraulic fluid from said main supply means while the other returns fluid to said main returned means,

a first secondary valve means connected to said first supply conduits,

a second main valve means connecting said main hydraulic supply and return means to a second pair of supply conduits so either of said second conduits may supply hydraulic fluid from said main supply means while the other returns fluid to said main returned means,

a third pair of supply conduits connected to said first secondary valve means, and a fourth pair of supply conduits connected to said first secondary valve means,

said first secondary valve means normally openily communicating each of said first supply conduits to a corresponding conduit of said third pair of supply conduits, and normally blocking communication between each of said second pair of supply conduits and a corresponding conduit of said fourth pair of supply conduits,

a fifth pair of supply conduits having first and second branches, each of said fifth pair of supply conduits connected to a corresponding conduit of said third pair of supply conduits and to a corresponding conduit of said pair of fourth pair of supply conduits,

a second secondary valve means connected to said first branch of said fifth pair of supply conduits,

a third secondary valve means connected to said second branch of said fifth pair of supply conduits,

a sixth pair of supply conduits having first and second branches, said first branch of said sixth pair of supply conduits connected to said second secondary valve means; and said second branch of said sixth pair of supply conduits connected to said third secondary valve means,

said second secondary valve means normally blocking communication of each of said first branch of said fifth supply conduits to a corresponding conduit of said first branch of said sixth pair of supply conduits,

said third secondary valve means normally openly communicating of each of said second branch of said fifth pair of supply conduits to a corresponding conduit of said second branch of said sixth pair of supply conduits,

said sixth pair of supply conduits connected to said pair of control hydraulic supply conduits joined to said hydraulic actuator,

said first and second main valve means being responsive to an electrical command signal to supply and return hydraulic fluid to and from said first pair of supply conduits and to and from said second pair of supply conduits, respectively, in amounts to position said movable shaft of said hydraulic actuator at a desired location,

actuator sensing means for producing an electrical signal representative of the position of said movable shaft of said hydraulic actuator,

each of said secondary valve means having sensing means for producing an electrical signal indicative of valve operation which blocks communication between respective conduits connected thereto which are normally open and which opens communication between respective conduits connected thereto which are normally blocked,

controller means for receiving said electrical command signal and said actuator sensing means electrical signal and said secondary valve sensing means electrical signals,

said controller means determining a failure occurrence by comparing the error represented by the difference in the electrical command signal and said actuator sensing means electrical signal to some known limit and when said limit is exceeded energizing corrective switching logic determined by said secondary valve sensing means electrical signal, which switching logic provides for proper change in valve operation of said secondary valve means to block communication between respective conduits connected thereto which are normally opened and to open communication between respective conduits connected thereto which are normally blocked to maintain the proper hydraulic fluid pressure for control of said principal hydraulic actuator.

2. A redundant control systemaccording to claim 1 including:

a third main valve means connecting said main hydraulic supply and return means to eighth pair of supply conduits so either of said eighth conduits may supply hydraulic fluid from said main supply means while the other returns fluid to said main return means,

a fourth secondary valve means connected to said eighth pair of supply conduits,

a ninth pair of secondary conduits connected to said third secondary valve means,

a tenth pair of supply conduits connected to said third SBQOl'ldG-{K valve means each of said ten pair of supply conduits connected to a corresponding conduit of said sixth pair of supply conduits, and

said third secondary valve means normally blocking communication between each of said ninth pair of supply conduits and a corresponding conduit of said tenth pair of supply conduits.

3. A redundant control system according to claim 2 wherein each of said secondary valve means have an internal moveable spool with lands to provide valve action between supply conduits.

4. A redundant control system according to claim 3 wherein each of said secondary valve means has a controller to supply hydraulic fluid to the upper land of its movable spool to shift its position.

Claims

1. A redundant control system for a hydraulic actuator comprising: a principal hydraulic actuator having a movable shaft for providing essential movement to a member, a pair of control hydraulic supply conduits joined to said actuator for supplying fluid thereto, main hydraulic supply and returned means providing a primary source of hydraulic fLuid pressure, a first main valve means connecting said main hydraulic supply and returned means to a first pair of supply conduits so either one of said first supply conduits may supply hydraulic fluid from said main supply means while the other returns fluid to said main returned means, a first secondary valve means connected to said first supply conduits, a second main valve means connecting said main hydraulic supply and return means to a second pair of supply conduits so either of said second conduits may supply hydraulic fluid from said main supply means while the other returns fluid to said main returned means, a third pair of supply conduits connected to said first secondary valve means, and a fourth pair of supply conduits connected to said first secondary valve means, said first secondary valve means normally openily communicating each of said first supply conduits to a corresponding conduit of said third pair of supply conduits, and normally blocking communication between each of said second pair of supply conduits and a corresponding conduit of said fourth pair of supply conduits, a fifth pair of supply conduits having first and second branches, each of said fifth pair of supply conduits connected to a corresponding conduit of said third pair of supply conduits and to a corresponding conduit of said pair of fourth pair of supply conduits, a second secondary valve means connected to said first branch of said fifth pair of supply conduits, a third secondary valve means connected to said second branch of said fifth pair of supply conduits, a sixth pair of supply conduits having first and second branches, said first branch of said sixth pair of supply conduits connected to said second secondary valve means; and said second branch of said sixth pair of supply conduits connected to said third secondary valve means, said second secondary valve means normally blocking communication of each of said first branch of said fifth supply conduits to a corresponding conduit of said first branch of said sixth pair of supply conduits, said third secondary valve means normally openly communicating of each of said second branch of said fifth pair of supply conduits to a corresponding conduit of said second branch of said sixth pair of supply conduits, said sixth pair of supply conduits connected to said pair of control hydraulic supply conduits joined to said hydraulic actuator, said first and second main valve means being responsive to an electrical command signal to supply and return hydraulic fluid to and from said first pair of supply conduits and to and from said second pair of supply conduits, respectively, in amounts to position said movable shaft of said hydraulic actuator at a desired location, actuator sensing means for producing an electrical signal representative of the position of said movable shaft of said hydraulic actuator, each of said secondary valve means having sensing means for producing an electrical signal indicative of valve operation which blocks communication between respective conduits connected thereto which are normally open and which opens communication between respective conduits connected thereto which are normally blocked, controller means for receiving said electrical command signal and said actuator sensing means electrical signal and said secondary valve sensing means electrical signals, said controller means determining a failure occurrence by comparing the error represented by the difference in the electrical command signal and said actuator sensing means electrical signal to some known limit and when said limit is exceeded energizing corrective switching logic determined by said secondary valve sensing means electrical signal, which switching logic provides for proper change in valve operation of said secondary valve means to block communication between respective conduits connected thereto which are normally opened and to open communication between respective conduits Connected thereto which are normally blocked to maintain the proper hydraulic fluid pressure for control of said principal hydraulic actuator.

2. A redundant control system according to claim 1 including: a third main valve means connecting said main hydraulic supply and return means to eighth pair of supply conduits so either of said eighth conduits may supply hydraulic fluid from said main supply means while the other returns fluid to said main return means, a fourth secondary valve means connected to said eighth pair of supply conduits, a ninth pair of secondary conduits connected to said third secondary valve means, a tenth pair of supply conduits connected to said third secondary valve means, each of said tenth pair of supply conduits connected to a corresponding conduit of said sixth pair of supply conduits, and said third secondary valve means normally blocking communication between each of said ninth pair of supply conduits and a corresponding conduit of said tenth pair of supply conduits.