GB2346456A

GB2346456A - Hydraulic logic cross-coupling between separate redunant servoactuators

Info

Publication number: GB2346456A
Application number: GB0001091A
Authority: GB
Inventors: David J Flavell
Original assignee: Moog Inc
Current assignee: Moog Inc
Priority date: 1999-02-04
Filing date: 2000-01-19
Publication date: 2000-08-09
Anticipated expiration: 2020-01-19
Also published as: GB0001091D0; GB2346456B; DE10004605A1; JP2000234601A; DE10004605B4

Abstract

A redundant control actuation system (100) provides hydraulic logic cross-coupling between separate servoactuators (101A, 101B). Each servoactuator has a control valve (102A, 102B) arranged to provide a hydraulic output in response to a control signal. Each actuator also has a hydraulic actuator (106A, 106B) arranged to move a load in response to the hydraulic output from its associated control valve. Logic valve means (103A, 104A, 105A, 103B, 104B, 105B) are operatively associated with the control valves (102A, 102B) and actuators (106A, 106B). Each logic valve means is supplied with hydraulic and electrical input signals. Each logic valve means is operatively arranged between the associated control valve and actuator to either (a) permit control operation of the actuator in response to the control signal, (b) permit the actuator to move freely and independently of the control signal, or (c) restrain movement of the load independently of the control signal, as a function of the supplied input signals. Each logic valve means is operatively arranged to provide a hydraulic output signal. The hydraulic output signal of each servoactuator is provided as the hydraulic input signal to the other servoactuator via lines 116, 118.

Description

HYDRAULIC LOGIC CROSS-COUPLING BETWEEN SEPARATE REDUNDANT SERVOACTUATORS

The present invention relates generally to servoactuators for moving a load in response to a control signal, and, more particularly, to an improved redundant control actua tion system in which separate servoactuators, the outputs of which are connected to a com mon load, are cross-coupled to exchange hydraulic logic information therebetween.

Modern fly-by-wire ("FBW") aircraft use hydraulically-powered electrically controlled dual-redundaht servoactuators to operate flight control surfaces, and, more recent ly, engine thrust-vectoring controls. Many of these servoactuators, particularly those de signed for military aircraft, employ tandem-piston actuators that are integrated into a single mechanical package and have redundant sources supplying pressurized hydraulic fluid inde pendently to one or more integrated electrohydraulic servovalves. On the other hand, in commercial aircraft, it is generally desired that the redundant servoactuators be physically separated from one another, and be provided with separate connections to independent pres sure sources and fluid returns.

In either case, these redundant servoactuators have been typically arranged to operate cooperatively in either an active-active manner or an active- standby manner. More particularly, the servovalves have been typically connected with respect to their respective actuators with logic valves that permit three distinct operating modes for each servoactuator.

The first of these modes involves active control, in which the servovalve is used to actively control the flows of fluid with respect to the associated actuator. The second mode is known as afree-bypass mode, in which the actuator is effectively disconnected (i.e., "feath ered") from its associated servovalve (e.g., because its control elements or power supplies have failed, or because1t is in a standby mode) to permit continued control and operation of the load by the other actuator. The third is known as a fail-safe mode, in which the servovalve is disconnected from the associated actuator, and with the opposing chambers of the disconnected actuator communicating with one another through a restricted orifice to permit continued, albeit "damped", movement of the load.

Previous cross-coupling techniques for redundant servoactuators have employed the exchange of electrical and/or hydraulic signals. In general, these prior art devices have involved pilot-operated solenoid valves and fail-safe valves to accomplish mode switching

2 in response to certain conditions. Some devices have even employed a bypass valve in connection with a fail-safe valve. Upon information and belief, each of these prior systems has involved a compromise of performance in weight, size or expense.

Accordingly, it would generally be desirable to provide an improved redundant control actuation system, and servoactuator for use in same, that avoid these compromises in the prior art.

According to a first aspect of the invention, there is provided a servoactuator for use in a redundant control actuation system, said servoactuator comprising a control valve arranged to provide a hydraulic output in response to a control signal, a hydraulic actuator arranged to move a load in response to the hydraulic output from said control valve, and logic valve means operatively associated with said control valve and actuator, said logic valve means being supplied with hydraulic and electrical input signals, said logic valve means being operatively arranged between said control valve and said actuator to either (a) permit control operation of said actuator in response to said control signal, (b) permit said actuator to move freely and independently of said control signal, or (c) restrain movement of said load independently of said control signal, as a function of said supplied input signals, said logic valve means being arranged to provide a hydraulic output signal.

According to a second aspect of the invention, there is provided a redundant control actuation system, comprising first and second servoactuators, each servoactuator having a control valve arranged to provide a hydraulic output in response to a control signal, a hydraulic actuator arranged to move a load in response to the hydraulic output from the associated control valve, and logic valve means operatively associated with said control valve and actuator, each logic valve means being supplied with hydraulic and electrical input signals, each logic valve means being operatively arranged between the associated control valve and actuator to either (a) permit control operation of said actuator in response to said control signal, (b) permit said actuator to move freely and independently of said control signal, or (c) restrain movement of said load independently of said control signal, as a function of said supplied input signals, each logic valve means being arranged to provide a hydraulic output signal, and wherein the hydraulic output signal of each servoactuator is provided as the hydraulic input signal to the other servoactuator.

In the preferred forrns, each control valve may be an electro-hydraulic servovalve, and the two servovalves are identical.

3 Each servoactuator may further include a first flow passageway arranged to selectively communicate the opposing chambers of its associated actuator when its logic valve means permits the actuator to move freely and independently of the control signal.

Each servoactuator may farther include a second flow passageway having a restricted orifice, the second flow passageway being arranged to selectively communicate the opposing chambers of its associated actuator when its logic valve means causes the actuator to restrain movement of the load independently of the control signal.

The logic valve means may include a bypass valve and a fail-safe valve connected hydraulically in series between the associated control valve and actuator. The bypass valve is movable between a first position in which fluid is permitted to flow between the associated control valve and actuator, and a second position in which fluid is prevented from flowing therebetween and is freely bypassed (i.e., without purposeful flow restriction) between the opposing chambers of the associated actuator. The bypass valve may be biased toward the second position. The bypass valve may include a valve spool mounted for sealed sliding movement within a body,and may fiifther include a spring operatively arranged to cause the spool to move toward the second position. The spool may be caused to move toward the first position by a fluid pressure.

The servoactuator may ftirther include a source of pressurized fluid and a solenoid valve operatively arranged between the source and the bypass valve. The solenoid valve may communicate with the source and be arranged such that energization of the solenoid valve by the electrical input signal will cause pressurized fluid from the source to move the bypass valve spool to the first position and to provide the hydraulic output signal.

The fail-safe valve is movable between an open position in which fluid is permitted to flow between the associated bypass valve and the actuator, and a closed position in which fluid is prevented from flowing between the associated bypass valve and actuator.

The fail-safe valve may be biased toward its closed position. The failsafe valve may farther include a valve spool mounted for sealed sliding movement within a body, and a spring operatively arranged to cause the fail-safe valve spool to move toward its closed position.

A fluid pressure, supplied to the servoactuator as its hydraulic input signal, may urge the fail safe spool to move toward its open position.

4 The following is a more detailed description of some embodiments of the invention, by way of example, reference being made to the accompanying drawings in which:

Figure I is a schematic view of a first prior art redundant control system in which two integrated servoactuators are coupled to a common load, Figure 2 is a schematic view of a second prior art redundant control actuation system in which two physically-separate servoactuators are coupled to a common load, Figure 3 is a schematic view of a third prior art control system in which two physically-separate servoactuators are coupled to a common load, and Figure 4 is a schematic view of an embodiment of a redundant control actuation system according to the present invention, which provides hydraulic logic cross-couplincy between physically-separate redundant servoactuators connected to a common load.

At the outset it should be clearly understood that like reference numerals are intended to identify the same structural elements, portions or surfaces, consistently throughout the several drawing figures, as such elements, portions or surfaces may be further descnibed or explained by the entire written specification, of which this detailed description is an integral part. Unless otherwise indicated, the drawings are intended to be read (e.g., cross-hatching, arrangement of parts, proportion, degree, etc.) together with the specification, and are to be considered a portion of the entire written description of this invention. As used in the following description, the terms "horizontal", "vertical", "left", "right", "up", and "down", as well as adjectival and adverbial derivatives thereof (e.g., horizontally", "rightwardly", "upwardly", etc.), simply refer to the orientation of the illustrated structure as the particular drawing figure faces the reader. Similarly, the terms "inwardly" and "outwardly" generally refer to the orientation of a surface relative to its axis or elongation, or axis of rotation, as appropriate.

The present invention broadly provides an improved servoactuator for use in a redundant control actuation system, and to a redundant control actuation system employing such improved servoactuators. However, before proceeding to a discussion of the improve ment according to the present invention, it is deemed advisable to review three prior art servoactuators, and redundant control systems incorporating same, in order that the signifi cance of the present invention may be better understood.

Referring now to Fig. 1, a first prior art redundant control actuation system is generally indicated at 20. This control system generally has two servoactuators. The left ward servoactuator is indicated as being servoactuator 21A, and the right servoactuator is to indicated as being servoactuator 21B. As used herein, the suffix "A" will refer to the parts, portions or surfaces of left servoactuator 21A, and the suffix "B" will refer to the corre sponding parts, portions or surfaces of right servovalve 21B. These two servoactuators are mirror images of one another, and are coupled by a common tandem piston actuator, gener ally indicated at 22.

Actuator 22 is shown as having two axially-spaced pistons 23A, 23B mounted on a common rod 24. Left piston 23A is mounted for sealed sliding movement within a left cylinder 25A, and right piston 23B is mounted for sealed sliding movement within a right cylinder 25B. The two servoaCEuators are otherwise mirror images of one another, except as described herein. Hence, only left servoactuator 21A will be explicitly described, it being understood that the corresponding reference numeral, albeit identified with suffix letter "B" rather than "A", refers to the corresponding part, portion or surface of right servoactuator 2 1 B. Servoactuator 2 1 A is shown as broadly including a two-stage four-way electro hydraulic servovalve, generally indicated at 26A, a bypass valve 28A, a fail-safe valve 29A, and a pilot solenoid valve 30A.

Servovalve 26A is arranged to be supplied with pressurized hydraulic fluid Psi from a suitable source (not shown), and is connected to a first fluid return R,. Servovalve 26A may, for example, be of the type disclosed in U.S. Patent No. 3,023, 782, the aggre gate disclosure of which is incorporated by reference. Suffice it to say here that this servo valve is known, and includes an electrical section 31A and a hydraulic section 32A. This type of servovalve is used to produce a differential hydraulic output at outlet ports C,, C2 in proportional response to an input electrical signal supplied via conductors 33A to the electri cal section of the servovalve.

Bypass valve 28A is shown as having a three-lobed valve spool 34A mounted for sealed sliding movement within a cylinder. The spool is biased to move leftwardlY to the position shown by a spring 35A in the right spool right end chamber.

The fail-safe valve 29A is also shown as having a three-lobed valve spool 36A mounted for sealed sliding movement within a body or cylinder. The spool is biased to move leftwardly by a spring 38A in the right spool end chamber. An actuator Piston 39A is operatively arranged in a cylinder, and has a stub shaft arranged to bear against the left end of spool 36A.

Solenoid valve 30A is also arranged to be provided with pressurized fluid from source P,,, and communicates with return R,. Solenoid valve 30A is a conventional three- way two-position solenoid valve. When the solenoid is de-energized (as shown), conduit 40A communicates with return R,. When the solenoid is supplied with an energization cur rent i,, pressurized fluid from source Ps, is supplied to conduit 40A, and to the right spool end chamber of fail-safe valve 29B. Conversely, another conduit 40B communicates sole noid valve 30B with the left end chamber of actuator piston 39A.

The structure shown in Fig. 1 is in a depressurized and de-energized condition.

When the system is energized and pressurized, supply pressure Psf and Ps2 are provided to servoaCEuators 21 A, 2113, where indicated. Similarly, the return ports commu nicate with separate fluid returns R, and R2. An electrically-commanded hydraulic pressure differential is produced at the outlet ports C,, C2of each servovalve in response to the elec trical signal supplied to the associated servovalve.

The solenoid valves 30A, 30B are energized with currents i,, '2 respectively.

Hence, supply pressure Psi exists in conduit 40A and is applied to the right end chamber of piston 39B. This displaces fail-safe valve spool 36B leftwardly, compressing spring 38B.

Conversely, supply pressure Ps2 exists in conduit 4013, and is applied to the left end chamber of actuator piston 39A, to displace fail-safe valve spool 36A rightwardly, compressing spring 38A. When the two fail-safe valve spools are so displaced by the respective supply pressures of the other servoactuator, the conduits containing the restricted orifices, severally indicated at 41A, are covered. Thus, such energization and pressurization overcomes the opposing bias of springs 39A, 3913, and shifts each fail-safe valve spool hard-over to enable unrestricted flow from the associated bypass valve through the associated fail-safe valve to the opposing chambers of the associated actuator.

Supply pressure is also supplied to the left spool end chamber of each bypass valve. This shifts each bypass valve spool hard-over, compressing springs 35A and 35B, respectively. This displacement of each bypass valve spool selectively communicates the servovalve outlet ports C,, C, with the opposing actuator chambers via the now-displaced bypass and fail-safe valve spools.

The control system 20 shown in Fig. I is arranged to operate in any of three modes: an active-active mode in which both servovalves are simultaneously operated to control the flows of fluid with respect to their respective actuator chambers, an active-free bypass mode in which one servovalve controls the movement of the actuator, while the other is "feathered" (i.e., with the opposed chambers of the associated actuator being in communi cation with one another without purposeful flow restriction), and afail- safe mode in which both actuators no longer control the operation of the actuator, but, rather, offer impedance and resistance to movement of the actuator rod.

As noted above, when both servoactuators, are pressurized and energized, the bypass valve spools and fail-safe valve spools are shifted to their respective displaced posi tions. Hence, each servovalve communicates directly with the opposing chambers of its associated actuator piston. Hence, when both servoactuators are normally pressurized and energized, the device operates in an active-active mode.

Suppose now that there is an energization or pressurization failure of servoact uator B. Either situation will cause solenoid valve 30B to move to its alternative position in which conduit 40B communicates with return R,. The right spool end chamber of bypass valve 34B, and the right spool end chamber of fail-safe valve 29B, will both be vented to return R2. Hence, bypass valve 28B will shift from its displaced or energized state, back to the position shown in Fig. 1. However, because servoactuator A is still operational in this example (i.e., is still pressurized and energized), supply pressure P., will continue to be provided through conduit 40A to the right end chamber of fail-safe valve 29B. Hence, this will keep the fail-safe valve spool 36B shifted leftwardly. Hence, the opposing chambers of the right actuator will communicate with one another through bypass valve 28B and fail-safe valve 29B, the spool of which is still displaced. In other words, the opposing chambers of the rightward actuator will be connected via a series of connected passageways such that the right actuator will be "feathered". Hence, it may move freely, the only intended resistance being the pressure to move the fluid through the series of connected passageways. Thus, in the situation where there is a pressurization or energization failure of servovalve B, control of the actuator will still,be continued by servoactuator A, and servoactuator B will be in free-bypass or "feathered" mode. Of course, if servoactuator A were to be depressurized or de-energized, while servovalve B continued to operate, the situation would be reversed.

Alternatively, if there is a pressurization and/or energization failure of both servoactuators, solenoid valves 30A and 30B would communicate conduits 40A and 40B with returns R, and R,, respectively Hence, the bypass valve springs and the fail-safe valve springs would both expand to urge their respective valve spools to move back to the posi- Eions shown in Fig. 1. In this condition, the opposing chambers of both actuators communi cate with their respective fluid returns via passageways containing restricted orifices 41A, 41B, respectively. Hence, in this third fail-safe mode, neither servovalve controls the oper ation of the load, but, passageways containing restricted orifices communicate the actuator opposing chambers with their respective returns. While not controlling the movement of the load, this load restraint is customarily sized to prevent "flutter" and other forms of dynamic instability of the load.

Therefore, this first embodiment offers three modes of operation. However, one disadvantage of this arrangement was that the device generally employed a tandem piston actuator in a common body. This was acceptable for some applications, but not for others.

Second Prior Art Embodiment (Fig. 2

Fig. 2 depicts another prior art redundant control actuation system, generally indicated at 50. Here again, this system included a left servoactuator 5 1 A and a right servo actuator 51B. These two servoactuators are arranged as mirror images of one another.

Here again, only the left servoactuator will be described, it being understood that the same reference numeral, albeit with the suffix letter "B", will refer to the corresponding part, portion or surface of the right servoactuator.

Each servoactuator has its own separate actuator connected to a common load 52. Another difference is that the fail-safe valve has been omitted, in favor of a solenoid operated damped-bypass valve, as described infta. Servoactuator 5 1 A includes a two-stage electrohydraulic servovalve 53A, again having an electrical section and a hydraulic section.

This servovalve may also be of the type shown and described in U.S. Patent No. 3,023,782.

Alternatively, other types of servovalves may be employed. Servovalve 53A is adapted to be supplied with pressurized fluid Psi from a suitable source, and is adapted to communicate with a fluid return R,. Servoactuator 51A also includes a pilot solenoid valve 54A, a dam ped-bypass valve 55A, and an actuator 56A. Solenoid valve 54A is a threeway two-posi tion solenoid-operated valve adapted to be energized by a current i,. When solenoid valve 54A is de-energized, conduit 58A communicates with the fluid return R,. When solenoid valve 54A is energized, supply pressure Psi, is provided to conduit 58A. Similarly, when solenoid valve 54B is de-energized, conduit 58B communicates with return R2. When sole noid 54B is energized, supply pressure Ps2 is provided to conduit 58B.

Bypass valve 55A is shown as having a three-lobed valve spool 59A mounted for sealed sliding movement within a body. A spring 60A urges the spool 59A to move leftwardly to the position shown.

To avoid interchanging logic information between the two separated servoactu ators, the system shown in Fig. 2 was operated in a active-standby mode. In other words, one servoactuator was energized and pressurized, while the other was not. Hence, for example, if servoactuator 5 1 A was pressurized and energized, the supply pressure Ps, would be applied through conduit 58A to shift bypass valve spool 59A rightwardly, while com pressing spring 60A. This enabled fluid communication between servovalve control ports Cl., C2 with the opposing chambers of actuator 56A. If servoactuator 5 1 A was used to control the movement of the load, servoactuator 51B was normally depressurized and de-en ergized, and the condition of its various parts was as shown in Fig. 2. In other words, spring 60B expanded to urge bypass valve spool 59B rightwardly. Hence, fluid could flow with respect to other opposed chamber of actuator 56B via restricted orifices, severally indicated at 6 1 B. Thus, by virtue of these restricted orifices, when one system was operated and the other was not, the non-operable servoactuator provided additional dead load that had to be overcome for the active servoactuator to displace the load 52. Hence, the servoactua tors; were built oversized to accommodate this additional load, and this unnecessary size compromised performance and expense.

If servoactuator 5 1 A failed by becoming depressurized or de-energized, servo actuator 5 1 B would be immediately pressurized and energized. The failure of servovalve 51A would cause spring 60A to expand to move bypass valve spool 59A to the position shown in Fig. 2, while servoactuator 51B was simultaneously energized and pressurized.

Thus, the situation would be reversed with respect to that previously described, with servo actuator 51B thereafter controlling movement of the load, and servoactuator 51A being switched to a damped-bypass mode.

Alternatively, if both servoactuators failed by being either depressurized or deenergized, both bypass valve spools would move to the position shown in Fig. 2. Hence, restricted orifices 61A and 61B would provide impedance to prevent dynamic instability of the load, notwithstanding the fact that neither servoactuator thereafter affirmatively con trolled the load.

Third Prior Art Embodiment (Fie. 3)

Fig. 3 illustrates a third prior art arrangement, generally indicated at 70, that avoided the interchange of hydraulic logic information between servoactuators 71A, 71B.

This system also included two separate servoactuators, 71a, 71b. Here again, both servo- actuators were configured as mirror images of one another. Hence, only the left servoactu ator will be explicitly described, it being understood that the corresponding parts. portions -to- or services of the right embodiment are indicated by the same reference numeral, albeit with suffix letter "B".

Servoactuator 7 1 A broadly included electrohydraulic servovalve 72A, a bypass valve 73A, a two-position solenoid-operated valve 74A, and a fail-safe valve 75A controlled by the operation of a solenoid 76A. Solenoid valve 74A was adapted to be energized with a current i,. Conversely, solenoid valve 74B was adapted to be energized with a current '2 Solenoid 76A was adapted to be energized with two separate summed currents, i, + '2, and solenoid 76B was also adapted to be energized with two separate summed currents, i, + '2- The two actuators 78A, 78B are connected to a common load 79.

Here again, electrohydraulic servovalve 72A could be a two-stage four-way servovalve, such as shown in U.S. Patent No. 3,023,782, and is adapted to be supplied with a supply pressure P., to communicate with a fluid return R, and to selectively produce a differential hydraulic outputs at its control ports C,, C2.

When solenoid valve 74A is energized, supply pressure P., will exist in conduit 79A.

Conversely, when solenoid valve 74A is de-energized, conduit 79A will com municate with return R,.

Bypass valve 73A is shown as having a three-lobed valve spool 80A mounted for sealed sliding movement within a body. The valve spool is biased to move leftwardly relative to the body by a spring 8 IA. Conduit 79A communicates with the spool left end chamber.

The fail-safe valve 75A is also shown as including a three-lobed valve spool 82A mounted for sealed sliding movement within a body. A spring 83A biases spool 82A to move leftwardly toward the position shown. When solenoid 76A is energized, spool 82A will be displaced rightwardly by compression of spring 83A.

This redundant control system was adapted to be operated primarily in an active-active manner. Normally, both servoactuators would be energized and pressurized.

Hence, each of the respective logic valve spools would be shifted in the appropriate direc tion against the urging of its associated return spring. Hence, each servovalve would com municate directly with its associated actuator.

Should there be a pressurization failure of servoactuator 71A, spring 81A would expand to move the bypass valve spool 80A to the position shown in Fig. 1. Howev er, since both servoactuators would still be energized, the two summed energization cur rents, i, + '2, would continue to hold valve spool 82A in a rightwardly- displaced condition.

Thus, in this arrangement, when servoactuator 7 1 A was depressurized but not de-energized, the opposing chambers of actuator 78A could communicate with the return. In effect, a depressurization of servoactuator 71A would cause the actuator 78A to switch to a free bypass mode, while servovalve B would continue in an active mode to control movement of the load.

Alternatively, if there was a de-energization of servovalve A (but not a de pressurization), then i, would be lost. This would cause solenoid valve 74A to move to its deenergized position. Spring 81A would expand to shift valve spool 80A leftwardly to the position shown. However, even though there was an absence of current il, current '2 from still-energized servoactuator 71 B would be sufficient to hold fail-safe valve spool 82A in a rightwardly-displaced condition. Hence, in this condition, servoactuator A would be in a firee-bypass mode.

Alternatively, if both servoactuators failed, either electrically or hydraulically, currents i, and '2 would be removed from solenoids 76A and 7613, permitting the fail-safe springs 83A, 83B would expand to urge the fail-safe valves 82A, 82B, respectively, to move to the positions shown in Fig. 3. In this condition, both actuators would be switched to their damped-bypass modes such that flow with respect to the actuator chamber would be constrained to pass through restricted orifices 84A, 84B.

The Fmbodiment of a Control System (Fig. 4) According to the invention, the embodiment of a redundant control actuation system is generally indicated at 100 in Figure 4. This arrangement also includes two sepa rateservoactuators, the, left being indicated as servoactuator IOIA and the right being indi cated as servoactuator 10113. Here again, these two servoactuators are substantially mirror images of one another, and the suffixes "A" and "B" will be used to distinguish the corre sponding parts, portions or surfaces of the two systems. Servoactuator IOIA is shown as including an electrohydraulic servovalve 102A provided with a supply pressure Ps, com municating with a return R, and adapted to provide differential hydraulic output at its outlet ports C,, C2, respectively. Servoactuator IOIA also includes a solenoid- operated valve 103A, a bypass valve 104A, a fail-safe valve 105A and an actuator 106A. The two actua tors are coupled to a common load 108. A conduit 109A communicates the outlet of sole noid valve 103A with the left spool left end chamber of by-pass valve 104A. When sole noid valve 103A is energized by current i,, supply pressure will exist in conduit 109A and will shift the bypass valve spool I IOA rightwardly, overcoming the bias of spring I I IA.

Conversely, when solenoid valve 103A is de-energized, conduit 109A communicates with return R, In this condition, spring I I 1A expands to move bypass valve spool I 10A left- wardly to the position shown.

The fail-safe valve 105A is shown as being a three-lobed valve spool 112A mounted for sealed sliding movement within a body. A spring 113A urges valve spool 1 12A to move rightwardly toward the position shown. An actuator I 14A has a piston I I 5A arranged to act against the right end of fail-safe valve spool 112A. The right end chamber of actuator 114A is provided with the pressure in conduit 109B via conduit 1. 16. Converse ly, the pressure in conduit 109A is provided by a conduit 118 to the left end chamber of actuator 114B. The left chamber of actuator 114A, and the right chamber of actuator 114B are vented to the atmosphere.

Thus, when servoactuator IOIA is both pressurized and energized, supply pressure Psi, will exist in conduits 109A and 118, and will shift the bypass valve spool I IOA leftwardly. Conversely, the pressure in conduit 109B will be transmitted by conduit 116 to the right end chamber of actuator I 14A to displace the fail-safe valve spool leftward ly. Conversely, the pressure in conduit 109A will be transmitted via conduit 118 to the left end chamber of actuator 114B to shift fail-safe valve spool 112B rightwardly from the posi tion shown. Thus, when both servoactuacors are energized and pressurized, the bypass valve spools and fail-safe valve spools are shifted from the positions shown in Fig. 4 to their displaced positions, thereby allowing control of each actuator by its associated servovalve.

Should solenoid 103A be de-energized while solenoid 103B remains energized, conduit 109A will communicate, with the return. Hence, bypass valve spool I IOA will shift leftwardly to the position shown. This will isolate servovalve 102A from actuator 106A.

However, the opposed chambers of actuator 106A will communicate with the return. In this regard, it should be noted that the pressurized signal from conduit 109B is transmitted via conduit 116 to keep fail-safe valve spool 112A shifted leftwardly. This allows actuator 106A to operate in its free-bypass mode.

Alternatively, should ser-voactuator A fail by being depressurized (but not deenergized), then the pressure in conduit 109A will again fall to the return pressure R, Spring 111 A will expand to urge the bypass valve spool 11 OA to move to the position shown in Fig. 4. However, the pressure of still-functioning servoactuator 10113 will be transmitted via conduit 116 to the right end chamber of actuator 1 14A to hold fail-safe valve spool 112A in its leftwardly-displaced position. Thus, in this alternative situation, the op posing chambers of actuator 106A will communicate with the return.

Alternatively, if both servoactuators become either depressurized and/or de-en ergized, conduits 109A and 109B will communicate with their returns R,, R2, respectively.

Hence, the bypass valve spool will be shifted back to the position shown in Fig. 4. Conver sely, loss of supply pressure in conduits 109A and 10913, will be transmitted via conduits 13 116.118, and the fail-safe valve spool springs 113A, 113B, will expand to move their respective valve spools to the position shown. In this condition, the opposed chambers of actuator 106A will communicate with return R, via restricted orifices I I 5A, I I 5A, while the opposed chambers of actuator 106B will communicate with return R, via restricted orifices 115B, 115B.

Therefore, in summary, with the invention shown in Figure 4, the two servoactuators may be operated simultaneously or independently. In other words, both servo actuators may be separately pressurized and energized to control movement of the load.

Alterriatively, only one servoactuator need be pressurized and energized. The other will be in a standby mode, as desired. Thus, if the improved device is operated initially in an active active mode, and there is a pressurization or energization failure to either servoactuator, the affected servoactuator will be immediately shifted to afree-bypass or standby mode, with the unaffected servoactuator continuing to maintain control over the load. Alternatively, if both servovalves fall, then both servoactuators move to a damped-bypass mode in which free movement of the load is restrained by passage of fluid through the restricted orifices.

Modifications Many changes and modifications may be made to the system described above with reference to Figure 4. For example, the servovalves may be two-stage four-way electrohydraulic servovalves, such as shown and described in U.S. Patent No. 3,023,782.

Alternatively, other types of servovalves may be substituted therefor. In the aircraft environment, it is generally desired that pressure sources P, and P,, be independent of one another. However, while desirable, this is not critical to the operation of the invention. Fluid sources P,, and P,2may therefore be independent of one another, or provided from a common source. Similarly, returns R, and R, may connect with a common return, or may be wholly independent of one another. The bypass and fail-safe valves may be rearranged in position between the control valve and the actuator and yet provide the same functions. The bypass valve and fail-safe valve may be spool valves, as shown, or may be of some other type or configuration. Similarly, the solenoid valves may be pilot-type poppet or spool valves. They may be integrated with the bypass valves, or the bypass function may be integrated with the control valve.

14 Therefore, while the presently preferred form of the embodiment of the redundant control system according to the invention has been shown and described, and several modifications thereof discussed, persons skilled in this aft will readily appreciate that various additional changes and modifications may be made without departing from the spirit of the invention, as defined and differentiated by the following claims.

Claims

A servoactuator for use in a redundant control actuation system, said servoactuator comprising a control valve arranged to provide a hydraulic output in response to a control signal, a hydraulic actuator arranged to move a load in response to the hydraulic output from said control valve, and logic valve means operatively associated with said control valve and actuator, said logic valve means being supplied with hydraulic and electrical input signals, said logic valve means being operatively arranged between said control valve and said actuator to either (a) permit control operation of said actuator in response to said control signal, (b) permit said actuator to move freely and independently of said control signal, or (c) restrain movement of said load independently of said control signal, as a function of said supplied input signals, said logic valve means being arranged to provide a hydraulic output signal.

2. A servoactuator according to claim I wherein said control valve is an electro hydraulic servovalve.

3. A servoactuator according to claim I or claim 2 and further comprising a first flow passageway arranged to selectively communicate the opposing chambers of said actuator when said logic valve means permits said actuator to move freely and independently of said control signal.

4. A servoactuator according to claim 3 and further comprising a second flow passageway having a restrictive orifice, said second flow passageway being arranged to selectively communicate the opposing chambers of said actuator when said logic valve means causes said actuator to restrain movement of said load independently of said control signal.

5. A servoactuator according to any one of claims 1 to 4 wherein said logic valve means includes a bypass valve and a fail-safe valve connected hydraulically between said control valve and said actuator.

16 6. A servoactuator according to claim 5 wherein said bypass valve is movable between a first position in which fluid is pen-nitted to flow between said control valve and actuator, and a second position in which fluid is prevented from flowing between said control valve and actuator but is freely bypassed between the opposing chambers of said actuator, and wherein said bypass valve is biased toward said second position.

7. A servoactuator according to claim 6 wherein said bypass valve includes a valve spool mounted for sealed sliding movement within a body, and wherein a spring is operatively arranged to cause said bypass valve spool to move toward said second position, and wherein a fluid pressure is operatively arranged to cause said bypass valve spool to move toward said first position.

8. A servoactuator according to claim 7 and further comprising a source of pressurized fluid and a solenoid valve operatively arranged between said source and said bypass valve, said solenoid valve communicating with said source and being arranged such that energization of said solenoid valve by said electrical input signal will cause pressurized fluid from said source to move said bypass valve spool to said first position and to provide said hydraulic output signal.

9. A servoactuator according to any one of claims 5 to 8 wherein said fail-safe valve is movable between an open position in which fluid is permitted to flow between said bypass valve and said actuator, and a closed position in which fluid is prevented from flowing between said bypass valve and said actuator, and wherein said fail-safe valve is biased toward said closed position.

10. A servoactuator according to claim 9 wherein said fail-safe valve includes a valve spool mounted for sealed sliding movement within a body, and a spring operatively arranged d fail 1 1 to cause sal 1 -safe valve spool to move toward said closed position and wherein a fluid pressure is supplied to said servoactuator as said hydraulic input signal and is operatively arranged to cause said fail-safe valve spool to move toward said open position.

17 11. A redundant control actuation system, comprising first and second servoactuators, each servoactuator having a control valve arranged to provide a hydraulic output in response to a control signal, a hydraulic actuator arranged to move a load in response to the hydraulic output from the associated control valve, and logic valve means operatively associated with said control valve and actuator, each logic valve means being supplied with hydraulic and electrical input signals, each logic valve means being operatively arranged between the associated control valve and actuator to either (a) permit control operation of said actuator in response to said control signal, (b) permit said actuator to move freely and independently of said control signal, or (c) restrain movement of said load independently of said control signal, as a function of said supplied input signals, each logic valve means being arranged to provide a hydraulic output signal, and wherein the hydraulic output signal of each servoactuator is provided as the hydraulic input signal to the other servoactuator.

12. A redundant control actuation system according to claim I I wherein each control valve is an electrohydraulic ser-vovalve.

13. A redundant control actuation system according to claim 12 wherein said control valves are identical to each other.

14. A redundant control actuation system according to claim 11 or claim 12 wherein each servoactuator further comprises a first flow passageway arranged to selectively communicate the opposing chambers of the associated actuator when the associated logic valve means pen-nits said associated actuator to move freely and independently of said control signal.

15. A redundant control actuation system according to claim 14 wherein each servoactuator farther comprises a second flow passageway having a restrictive orifice, said second flow passageway being arranged to selectively communicate the opposing chambers of the associated actuator when said logic valve means causes said associated actuator to restrain movement of said load independently of said control signal.

18 16. A redundant control actuation system according to any one of claims I I to 15 wherein said each logic valve means includes a bypass valve and a fail-safe valve connected hydraulically between the associated control valve and the associated actuator.

17. A redundant control actuation system according to claim 16 wherein each bypass valve is movable between a first position in which fluid is permitted to flow between the associated control valve and the associated actuator, and a second position in which fluid is prevented from flowing between said associated control valve and said associated actuator but is freely bypassed between the opposing chambers of said actuator, and wherein each bypass valve is biased toward said second position.

18. A redundant control actuation system according to claim 17 wherein each bypass valve includes a valve spool mounted for scaled sliding movement within a body, and wherein a spring is operatively arranged to cause said bypass valve spool to move toward said second position, and wherein a fluid pressure is operatively arranged to cause said bypass valve spool to move toward said first position.

19. A redundant control actuation system according to claim 18, wherein each servoactuator fiirther comprises a source of pressurized fluid and a solenoid valve operatively arranged between said source and the associated bypass valve, each solenoid valve conununicating with said source and being arranged such that energization of said solenoid by said supplied electrical input signal will cause pressurized fluid from said source to move the associated bypass valve to said first position and to provide said hydraulic output signal.

20. A redundant control actuation system according to claim 15 wherein each fail-safe valve is movable between an open position in which fluid is permitted to flow between the associated bypass valve and the associated actuator, and a closed position in which fluid is prevented from flowing between the associated bypass valve and the associated actuator, and wherein each fail-safe valve is biased toward said closed position.

21. A redundant control actuation system according to claim 20 wherein each fail-safe valve includes a valve spool mounted for sealed sliding movement within a body, and a 19 spring operatively arranged to cause said fail-safe valve spool to move toward said closed position, and wherein a fluid pressure is supplied to said servoactuator as said hydraulic input signal and is operatively arranged to cause said fail-safe valve spool to move toward said open position.

22. A redundant control actuation system substantially as hereinbefore described with reference to Figure 4 of the accompanying drawings.

AMENDMENTS TO THE CLAIMS HAVE BEEN FILED AS FOLLOWS:

I A servoactuator for use in a redundant control actuation system, said servoactuator comprising a control valve arranged to provide a hydraulic output in response to a control signal, a hydraulic actuator arranged to move a load in response to the hydraulic output from said control valve, and logic valve means operatively associated with said control valve and actuator, said logic valve means being supplied with external and internal hydraulic input signals and external electrical input signals, said logic valve means being operatively arranged between said control valve and said actuator to either (a) permit control operation of said actuator in response to said control signal, (b) permit said actuator to move freely and independently of said control signal, or (c) restrain movement of said load independently of said control signal, as a function of said supplied input signals, said logic valve means being arranged to provide a hydraulic output signal which is a function of said hydraulic and electrical input signals.

2. A servoactuator according to claim I wherein said control valve is an electrohydraulic servovalve.

3. A servoactuator according to claim I or claim 2 and further comprising a first flow passageway arranged to selectively communicate the opposing chambers of said actuator when said loalc valve means permits said actuator to move freely and independently of said control signal.

4. A servoactuator according to claim 3 and further comprising a second flow passageway having a restrictive orifice, said second flow passageway being arranged to selectively communicate the opposing chambers of said actuator when said logic valve means causes said actuator to restrain movement of said load independently of said control signal.

5. A servoactuator according to any one of claims I to 4 wherein said logic valve means includes a bypass valve and a fail-safe valve connected hydraulically between said control valve and said actuator.

6. A servoactuator according to claim 5 wherein said bypass valve is movable between a first position in which fluid is permitted to flow between said control valve and actuator, and a second position in which fluid is prevented from flowing between said control valve and actuator but is freely bypassed between the opposing chambers of said actuator, and wherein said, bypass valve is biased toward said second position.

7. A servoactuator according to claim 6 wherein said bypass valve includes a valve spool mounted for sealed sliding movement within a body, and wherein a spring is I operatively arranged to cause said bypass valve spool to move toward said second position, and wherein a fluid pressure is operatively arranged to cause said bypass valve spool to move towards said first position.

11 8. A servoactuator according to claim 7 and further comprising a source of pressurized fluid and a solenoid valve operatively arranged between said source and said bypass valve said solenoid valve communicating with said source and being arranged such that energization of said solenoid valve by said electrical input signal will cause pressurized fluid from said source to move said bypass valve spool to said first position and to provide said hydraulic output signal.

9. A servocatuator according to any one of claims 5 to 8 wherein said fail-safe valve is moveable between an open position in which fluid is permitted to flow between said by pass valve and said actuator, and a closed position in which fluid is prevented from flowing between said bypass valve and said actuator, and wherein said fail-safe valve is biased toward said closed position.

10. A servoactuator according to claim 9 wherein said fail-safe valve includes a valve spool mounted for sealed sliding movement within a body, and a spring operatively arranged to cause said fail-safe valve spool to move toward said closed position and wherein a fluid pressure is supplied to said servoactuator as said hydraulic input signal and is operatively arranged to cause said fail-safe valve spool to move toward said open position.

n 11. A redundant control actuation system comprising first and second separate servoactuators, each servoactuator having a control valve arranged to provide a hydraulic output in response to a control signal, a hydraulic actuator arranged to move a load in response to the hydraulic output from the associated control valve and logic valve means operatively associated with said control valve and actuator, each logic valve means being supplied with external and internal hydraulic input signals and external electrical input signals, each logic valve means being operatively arranged between the associated control valve and actuator to either (a) permit control operation of said actuator in response to said control signal, (b) permit said actuator to move freely and independently of said control signal, or (c) restrain movement of said load independently of said control signal, as a function of said supplied input signals, each logic valve means being arranged to provide a hydraulic output signal which is a function of said hydraulic and electrical input signals, and wherein the logic control of each servoactuator is a function of the hydraulic output signal of the other servoactuator.

12. A redundant control actuation system according to claim I I wherein each control valve is an electrohydraulic servovalve.

13. A redundant control actuation system according to claim 12 wherein said control valves are identical to each other.

74 14. A redundant control actuation system according to claim I I or claim 12 wherein each servoactuator further comprises a first flow passageway arranged to selectively conununicate the opposing chambers of the associated actuator when the associated logic valve means permits said associated actuator to move freely and independently of said control signal.

15. A redundant control actuation system according to claim 14 wherein each servoactuator further comprises a second flow passageway having a restrictive orifice, said second flow passageway being arranged to selectively communicate the opposing chambers of the associated actuator when said logic valve means causes said associated actuator to restrain movement of said load independently of said control signal.

16. A redundant control actuation system according to any one of claims 11 to 15 wherein said each logic valve means includes a bypass valve and a fail-safe valve connected hydraulically between the associated control valve and the associated actuator.

17. A redundant control actuation system according to claim 16 wherein each bypass valve is moveable between a first position in which fluid is permitted to flow between the associated control valve and the associated actuator, and a second position in which fluid is prevented from flowing between said associated control valve and said associated ? actuator but is freely bypassed between the opposing chambers of said actuator, and wherein each bypass valve is biased toward said second position.

18. A redundant control actuation system according to claim 17 wherein each bypass valve includes a valve spool mounted for sealed sliding movement within a body, and wherein a spring is operatively arranged to cause said bypass valve spool to move toward said second position, and, wherein a fluid pressure is operatively arranged to cause said bypass valve spool to move toward said first position.

19. A redundant control actuation system according to claim 18, wherein each servoactuator further comprises a source of pressurized fluid and a solenoid valve operatively arranged between said source and the associated bypass valve, each solenoid valve communicating with said source and being arranged such that energization of said solenoid by said supplied electrical input signal will cause pressurized fluid from said source to move the associated bypass valve to said first position and to provide said hydraulic output signal.

20. A redundant control actuation system according to claim 20 wherein each fail-safe valve includes a valve spool mounted for sealed sliding movement within a body, and a spring operatively arranged to cause said fail-safe spool to move toward said closed position, and wherein a fluid pressure is supplied to said servoactuator as said hydraulic input signal and is operatively arranged to cause said fail-safe valve spool to move toward said open position.

21. A redundant control actuation system according to claim 20 wherein each fail-safe valve includes a valve spool mounted for sealed sliding movement within a body, and a spring operatively arranged to cause said fail-safe valve spool to move toward said closed position, and wherein a fluid pressure is supplied to said servoactuator as said hydraulic input signal and is operatively arranged to cause said fail-safe valve spool to move toward said open position.

22. A redundant control actuation system substantially as hereinbefore described with reference to Figure 4 of the accompanying drawings.