Patent GB-777915-A (GB)
Title: Improvements in and relating to hydraulic servomotors, more particularly for steering apparatus of dirigible craft
IPC: G05D1/00
Filed: 1953-06-19
Abstract: 777,915. Automatic steering and attitude control systems. BOULY, H. G. (Minneapolis- Honeywell Regulator Co.). June 19, 1953, No. 17107/53. Class 38 (4). [Also in Group XXIX] An automatic pilot for a helicopter is controlled by three differential hydraulic servomotors (see Group XXIX) each having a manually controlled section and an automatically controlled section either of which is operative to move the output of the servomotor and the automatically controlled section of which is controlled by a balanceable electric network of the parallel voltage summing type. Figs. 1 and 2 show a differentially acting automatic pilot for a helicopter having a yaw control section 10, a roll or bank attitude control section 11, and a pitch control section 211, Fig. 2, each having a differential hydraulic servomotor. The output member 14 of the yaw control section varies the pitch of the blades of a counter torque rotor and is operated by the differential servomotor 15 having a manual section 17 controlled from the rudder bar 19 and an automatic section 16, the control valve of which is actuated by a discriminator amplifier 27. The amplifier 27 is fed through a summing point 43 from signal generators 31, 46, 58, 70, 93, 106 with signals corresponding respectively to the position of the manual control or rudder bar 19, the rate of yaw as registered by a gyro yaw rate indicator 24, the craft's heading as registered by the compass unit 25, the bank attitude of the craft as registered by the gyro vertical 26, the out-ofbalance of the network 23, and the position of the output member 14. The signal generator 58 is rendered ineffective by the disengagement of a magnetic clutch 65 when the rudder bar 19 is moved from its central position. When a switch 77 is moved over from a contact 80 to a contact 81 the out-of-balance signal of the network 23 is fed to an amplifier 28 controlling a centring motor 29 arranged to adjust the signal generator 93 so as to balance the network 23. The bank control section 11 has a differential hydraulic servomotor 115 with a manual section 117 controlled by movements of the control column 119 about the longitudinal axis of the craft and an automatic section 116 controlled by an amplifier 127 by signals from a network 123. The latter is fed with signals from signal generators 70, 131, 146, 157, 169, ahese responding respectively to the bank tttitude of the craft, the position of the control column 119 relative to the craft's longitudinal axis, the rate of roll as registered by a gyro turn indicator 124, the out-of-balance of the network 123, and the position of the output member 114. The latter cyclically adjusts the pitch of the blades of the supporting rotor or rotors to maintain the craft stabilizer about its longitudinal axis. As in the yaw control section 10, a switch 178 is provided to feed the out-of-balance signal of the network 123 into an amplifier 167 which controls a centring motor 165 in turn adjusting the signal generator 157, the output of which is fed back into the network 123 through a resistor 162. The pitch control section 211 is generally similar to the sections 10, 11 and has a differential hydraulic servomotor 181 with a manual section 183 controlled through a connection 194 from the control colunm 119 by movements of the latter about the lateral axis of the craft and an automatic section 182, the control valve 206 of which is operated against a centring spring 210 by a solenoid energized under the control of an electronic amplifier 221. The output member 180 of the servomotor operated to adjust the pitch of the supporting rotor blades cyclically to maintain or effect a change in the attitude of the craft about its lateral or pitch axis. The amplifier 221 is fed from a summing point 225 with signals from a control stick position compensating signal generator 227, a craft pitch rate signal generator 238 responsive to movements of a gyro turn indicator 248, a pitch attitude signal generator 250 responding to pitch changes registered by a gyro vertical 256, a control stick position displacement signal generator 258, a synchronizing signal generator 260, a rebalancing signal generator 282 responsive to movements of the output member 180 and providing a follow-up signal. Two-way switches 290, 295 are provided to cut out the signals from the generators 250, 258, 260 when it is desired to operate the arrangement purely as a basic lagged rate auto pilot. In this case the signals from the generators 258 and 250 are applied through the amplifier 270 to control a centring motor 268 which in turn controls the synchronizing signal generator 260. The latter supplies balancing signals to the part of the network which is cut out. The sub-network 243 of the pitch rate control gives components of rate and integrated rate (or displacement). The signal generators each comprises a potentiometer such as 32 with an earthed centre tapping 35 and a slider 33 co-operating with a resistor such as 34 across which is a constant voltage. The tapped voltage is applied to sub-networks such as 31 comprising the capacities 31, 40 and resistors 39, 42. Specification 777,916 is referred to.