United Technologies Corporation

David J Verzella

Stuart C Wright

William C Fischer, Jr

Don L Adams

Lou S Cotton

Raymond G Johnson, Jr

Troy J LaMontagne

Arthur Lawrence Sivigny

Byron Graham, Jr

A control system, having an input command signal and driving a prime mover, is provided with variable magnitude and/or rate input signal limiting that is adjusted by maps 68,70,72,74 which set the limits for a variable magnitude limiter 14 and a variable rate limiter 22 as a function of the prime mover rate. The limiting is adjusted dynamically as the prime mover rate changes. When the prime mover enters an undesirable operating condition, the maps only limit the command signal in the direction of such condition. The adjustable limiting is enabled or disabled based on the position, rate, and/or acceleration of the prime mover.

Adaptive control system input limiting

A heading trim reference system provides beep commands indicative of a desired heading/attitude change to the roll channel of an AFCS as roll commands at slow speed in a conventional manner, and to the yaw channel as yaw commands at cruise speed. At cruise speed, the yaw synchronizing integrator responds to the beep commands and provides an error signal to existing turn coordination logic to turn the aircraft.

Heading reference trim system

The directions of travel of an inner and an outer loop actuator are monitored for movement in opposite directions within selected ranges and the outer loop actuator is disabled under selected conditions. These conditions may include movement of both the inner and outer loop actuators in opposite directions, any one of which has been detected moving at a rate greater than a selected rate or to a position outside a selected range. The invention is particularly suited for an aircraft trim actuator shutdown monitor system.

Aircraft trim actuator shutdown monitor system and method

In a dual actuator system, runaways are identified by comparing the position and rate of one actuator to another. When there is a threshold position discrepancy and a sustained rate discrepancy, a fault is indicated. The faster actuator is identified as the runaway.

Dual-actuator monitor

The sense (direction) of outer-loop commands is compared with the sense (direction) of inner-loop signals in an aircraft AFCS. A disparity in sense indicates an outer-loop failure. To reduce nuisance failures the comparison is made only when inner-loop signal thresholds are exceeded and, in the context of outer-loop commands which are pulses, only at the onset of an outer-loop command and for a limited time thereafter.

Outer-loop monitor for aircraft automatic flight control system

An improved PBA shutdown monitor circuit senses collective pitch control position rate of change magnitude and inhibits PBA shutdown in response to the continuous presence of sensed magnitude within a range of selected collective pitch rate magnitudes bounded by a slow rate limit signal value and a fast rate limit signal value.

Shutdown monitor for a helicopter pitch bias actuator

In an aircraft automatic flight control system, automatic shutdown (42) of the roll axis thereof (FIG. 1) as a consequence of faults detected therein also provides automatic shutdown of the yaw axis thereof (180) in the same fashion as detection of faults in the yaw axis (171, 167) provides shutdown of the yaw axis. Coupling of the roll axis shutdown into the yaw axis shutdown allows determining which of three axes cause lighting of a single trim shutdown indicator by resetting the yaw shutdown register (145) and simultaneously resetting both the pitch and roll shutdown registers by means of a single cyclic pitch control switch. Automatic yaw trim outer loop and yaw inner loop stability systems are disclosed (FIG. 2).

Aircraft roll-yaw fault protocols

In an aircraft automatic flight control system having a reference parameter synchronizing system (70) operable in response to a trim release switch (44), an initial trim release period (139), on the order of a large fraction of a second (137) causes (217, 218) a relatively slow effect trim reference integrator (208, 211) time constant, for smooth transitions of any error signal, followed by a relatively fast (216) effective reference integrator time constant for close, rapid tracking of the reference signal with the actual aircraft parameter.

Dual response aircraft reference synchronization

In an automatic flight control system, failure of dual inner loop actuators (12, 13) to track position (22, 23) within a permissible tolerance (182) of each other will cause automatic shut down (185, 190) of an outer loop actuator (37) which is responsive (61) to the same proportional signals (54, 55) as are the inner loop actuators. The invention is disclosed in a system in which automatic flight control positioning of the control surfaces of the aircraft is through a fast, limited authority inner loop, the authority of which is centered by repositioning of the outer loop.

Dual inner loop fault inhibit of aircraft outer loop

An aircraft automatic flight control system having a roll channel (FIG. 1), a yaw outer loop trim system (bottom of FIG. 2) and a yaw stability inner loop (top of FIG. 2) provides proportional (129) and integral (114) lateral acceleration inputs to the yaw trim system (106, 93) during coordinated turns, and provides proportional (130) and lagged (131) roll rate inputs to the trim system to provide initial coordination to the turns.

Aircraft coordinated turn with lagged roll rate

In an aircraft automatic flight control system, a flight path controlling, full authority outer loop actuator (37) operated in response to the integral (41) of commands thereto, is shutdown (111, 113-115) in response to the sensing (31, 32) of force on the related pilot control member (27). After removal of force (118), the outer loop is continued to be shut down for a time interval (119) to allow the aircraft to resettle toward the trim point before building up error in the integrator, unless high input demand (122) is indicated.

Pitch stick force inhibit of aircraft automatic outer loop

In an aircraft automatic flight control system, proportional commands (54, 55) provided to fast, limited authority inner loop actuators (12, 13) are integrated (41), and when the integrator output indicates that the inner loop actuators 12, 13 have been driven a certain percentage of their authority, a comparator (130, 132) activates a pulse generator (137, 138) to provide timed excitation of an actuator (150), thereby to position the aircraft control system outer loop by a commensurate increment. Driving the actuator for a longer time than the desired pulse width is detected (165-169) and causes automatic shutdown (190) of the actuator. Resetting the integrator at the start of each pulse (162, 104), and pulse-controlled gating of the pulse circuits (172, 135, 136) allow sensing of authority transitions which occur within a pulse, and permit a subsequent pulse in response thereto.

Pulsed aircraft actuator

In an aircraft automatic flight control system (FIG. 4) the application of force to a control member (35R, FIG. 5) forces (222, 216, 217, 212, 213) the flight path controlling, full authority outer loop to be disengaged. Once disengaged by force, the outer loop remains disengaged (224) until force is removed (225) and a signal indicates (226) a need to reestablish the outer loop. Reestablishment may be indicated by beeping (228) or by the controlled attitude (54R, 55R) being restored to within a predetermined level (230).

Roll attitude inhibit of aircraft automatic outer loop

An aircraft automatic flight control system includes a pair of fast, limited authority inner loop actuators (12, 13) responsive to signals (52-55) indicative of aircraft attitude (68, 69) or other flight parameters such as airspeed (84), the inner loop being recentered by an outer loop actuator (37) responsive to attitude or other aircraft parameter-indicating signals (54, 55). Commands (40) applied to the outer loop are applied in a lagged fashion (58, 59) in opposite direction so as to drive the inner loop actuators (12, 13) back toward the center of their authority. The rate of response of the outer loop (FIG. 2, FIG. 5) is adaptive in dependence upon airspeed (93, 96, 212, 213) and in response to magnitude of inner loop input (101, FIG. 2). An integral gain (41), pulsed (39), open loop drive of the outer loop actuator (37) and outer loop automatic shutdown (38) are disclosed.

Automatic outer loop centering of aircraft inner loop

In a helicopter automatic flight control system having both automatic pitch attitude retention (70, 71) and automatic airspeed hold (84) and responsive both to pitch attitude error (206) and integrated (241) airspeed error (230), saturation of either the attitude error or integrated airspeed error circuitry is avoided by sensing (171) integrated airspeed error buildup to a threshold magnitude (which may be a significant fraction of the instantaneous authority of the automatic flight control system), and causing (169, 167) automatic slewing of the pitch attitude reference signal toward the current pitch attitude and reduction of the integrated airspeed error. In a disclosed embodiment, the correction of attitude reference and reduction of airspeed error is effected by utilizing an equal effective time constant (220, 221; 258, 259) for both actions over the same period of time (170, 168, 175).

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Guilford, CT, United States of America

David J Verzella