Motors: expansible chamber type – Working member position feedback to motive fluid control – Electrical input and feedback signal means
Patent
1985-02-07
1986-09-23
Michalsky, Gerald A.
Motors: expansible chamber type
Working member position feedback to motive fluid control
Electrical input and feedback signal means
F15B 909
Patent
active
046128441
ABSTRACT:
An actuator of the type used in aircraft flight controls and similar applications is combined with a fail-passive electrohydraulic control system (11) that affords the usual actuator response to electrical input commands during normal operation, and responds to any of a number of possible failure conditions to dispose the actuator in a passive or neutral failure mode. The passive-failure mode allows the actuator (15) to remain in the last-known valid position or move in response to an external force such as provided by a redundant backup actuator thereby avoiding a possibly dangerous flight condition that can result from a "hard over" actuator response to a failure condition. First and second unbalanced eletrohydraulic servo actuator controls (14 and 16) are connected in back-to-back closed control loops bewteen the actuator (15) and electrical command inputs (14e and 16e) to form a balanced actuator configuration, and the separate control loops are synchronized by a synchronizing piston and associated electrical position transducer (24) that enable normal actuator operation so long as a predetermined relationship exists between the supply pressure Ps and the sum of the fluid pressure Pc1 and Pc2 applied to opposite sides of the actuator. Any failure condition results in unsynchronizing the separate control loops and equalizing the pressures at opposite sides of the actuator, thereby producing the fail-passive mode.
REFERENCES:
patent: 3901128 (1975-08-01), Swogger
Michalsky Gerald A.
The Boeing Company
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