Patent GB-1131669-A (GB)
Title: Redundant control system
IPC: B64C13/24
Filed: 1966-12-12
Abstract: 1,131,669. Fluid-pressure servomotor systems. BELL AEROSPACE CORP. Dec.12, 1966 [Dec.23, 1965], No.55511/66. Heading G3P. A redundant control system for use in positioning a multiplicity of controlled surfaces in response to input signals and adapted to detect and disable malfunctioning portions of the system comprises means for producing mechanical and electrical input signals, a plurality of control channels each including first and second signal summing means, such as 160, Fig.4a, each connected to receive mechanical and electrical input signals and to produce a separate output signal proportional to the received signals, positioning means, such as 173, 174 connected between each of the first and second signal summing means and one of the multiplicity of controlled surfaces, such as 151, means connecting the input signal generating means to the first and second signal summing means in each of the channels, sensing means for detecting separate output signals and producing a separate monitor signal in response to each output signal for a comparator, such as 177, which provides an error signal in response to a discrepancy between pre-selected monitor signals to disable the failed portions of the control channels responsible for the discrepancy. In the preferred embodiment, three servovalves 26, 36 and 46 providing pilot control of the roll, pitch and yaw of an aircraft each receive a mechanical signal through linkages 21, 31, and 41 from the pilot's wheel, stick or pedal controls and an electrical signal through liners 25, 35, 45 connected to transducers 23, 33, 43 through the appropriate sections of an autopilot (not shown). The latter also produces duplicate signals for the corresponding servovalves of the co-pilot's control system and the mechanical outputs of the two systems are combined as shown in Fig. 3 in which the pilot's roll and pitch signals, Rc and Pc, are applied to a mechanical mixer 103 and to an inverter 112 and mixer 115 to provide an inverted roll signal, -Rp, and sum and difference signals, Rp + Pp and Pp - Rp. Signals from the co-pilot system provide a similar plurality of output signals, such as Rc, Pc which are applied together with those derived from the pilot to the summing units 160, 201, 202 and 180 for operating the control surfaces on the right wing of the aircraft and to similar units (not shown) on the left wing. The signals are applied direct by a linkage, such as 163, to the two spool valves of each summing unit and through feed-in springs, such as 164 and 165, to the armature of a torque motor which also receives electrical signals through lines, such as I and J, from an automatic stabilizer (not shown). Output signals corresponding to the positions of the spool valves are applied to a comparator, such as 177, which operates a switching valve 169 to shut down the unit 160 when a discrepancy occurs. The comparator 185 receives signals from elevator control units on both wings of the aircraft so that an error signal causes switching from one portion of each summing unit to the other while a second failure in the same control channel puts the spool valves under manual control only from the linkage Pp. A similar control system is employed for the two elevons on each wing. The rudder of the aircraft has multiple control surfaces 1, 2 and 3, Fig.5, the surface 3 having a control system similar to that used for the ailerons and being arranged to operate only in conjunction with the mechanical input if necessary. Surfaces 1 and 2 are controlled by a system similar to that used for the elevons. To minimize the risk of losing the supply of fluid under pressure, three separate sources PS1, PS2 and PS3 are provided; the source PS1 being derived from pumps 301, 302 driven by engines 1 and 4, PS2 from pumps 305, 306 driven by engines 2 and 3, and PS3 from electrically driven pumps 307, 308 connected to alternators on all four engines.