Patent GB-985977-A (GB)
Title: Dead reckoning information processor
IPC: G06G7/78
Filed: 1961-02-08
Abstract: 985,977. Aircraft indicators. MINISTER OF NATIONAL DEFENCE OF H.M. CANADIAN GOVERNMENT. Feb. 8, 1961 [Feb. 15, 1960], No. 4705/61. Heading B7W. [Also in Division G4] An apparatus for processing aircraft navigational information comprises a first ball resolver 100 having angular and linear input shafts 101, 102 for receiving respectively the analogues of aircraft true track and ground miles travelled along the aircraft track; sine and cosine output shafts 103, 105 for the resolver adapted to take off respectively the analogues of change in " east west miles " and change in " north south miles " components of the ground miles travelled; a second ball resolver 141; an angular input shaft 140 for applying as an input the said " north south miles " component to the second ball resolver, the cosine output shaft of the first ball resolver being adapted as an input shaft 155 to apply to the second ball resolver the analogue of the east-west miles co-ordinate component; the sine output shaft 157 taking off from the second ball resolver the analogue of change in convergency and the linear input shaft 155 of the second ball resolver being adapted to take off as an output from the second ball resolver the analogue of change in longitude. The data available in the aircraft will be true air speed true heading and wind speed and direction, and this information is fed to a mechanical triangle solver in combination with a Doppler radar drift finding device to determine the drift (Fig. 1, not shown). These devices are slaved together, in such a way that when the Doppler radar is operative the mechanical triangle solver acts merely as a memory for use in the event of Doppler failure, but when the Doppler radar is inoperative the triangle solver is in control. A ball and disc integrator coupled to the triangle solver provides an output which represents ground miles travelled (Fig. 2, not shown). The signal from the Doppler radar or mechanical triangle solver represent drift is used to control the motor 33 (Fig. 3) which positions the shafts of the synchro transmitter 38 and the control transformer 37 through the gearing 73, and the casing of an electromechanical differential 81 through the gearing 73, and the casing of an electromechanical differential 81 through the gearing 74. Thus a first input to the differential 81 is the analogue of drift angle. A second input to this differential is an electrical analogue of precise true heading, obtained from other instruments in the aircraft. The error signal generated by the differential is amplifier (at 82) and applied to the servomotor 83 which through gearing 84 supplies an analogue of the track made good to one side of the mechanical differential 68 and through gearing 85 to the 2 inch diameter ball resolver 100. The electrical analogue of ground miles travelled is applied via the motor 33a as a shaft rotation to the differential 68 to which there is also applied an analogue of track made good. This arrangement removes false inputs of ground miles caused by changes of track so that the analogue of ground miles travelled by the aircraft is applied to the linear input shaft 102 of the ball resolver 100. The sine and cosine output shafts of the resolver represent analogues of the X or east-west and Y or north-south components of the ground miles travelled in the forms of shaft rotations, the north-south component also being equivalent to the analogue of change in latitude. This component is fed via the gearbox 120, differential 130 and gear-box 131 to the angular input shaft of a second ball resolver 141 (of 1 inch diameter). The cosine output shaft of this ball resolver is coupled to the east-west output of the first resolver through a differential potentiometer 145, thus adapting the cosine output shaft of the second resolver as an input shaft. The normal linear input shaft 155 of the second ball resolver is adapted as an output shaft. At the potentiometer 145 is also developed an electrical error signal which is applied to the motor 151 through an amplifier 150, which drives the shaft 155 through a gearbox 154, and thus provides servo control over the output. This adaptation of a normal ball resolver enables the computer to be used effectively for navigation in polar regions. The output on shaft 157 will represent the analogue of change in convergency of meridians, since this represents change in longitude multiplied by sine of latitude and this information is transmitted to apparatus capable of using it. The analogues of change in latitude and change in longitude from shafts 105 and 155 are transmitted to remote counters 300, 300a through transmitters 261, 207 to indicate the dead reckoned position of the aircraft in terms of latitude and longitude. To allow for the correction of the dead reckoned position when direct observations are made, an analogue memory is provided to store changes determined by the computer while the correction is being set in. This is described in Specification 985,979. Furthermore when the equator or international date line is being crossed the latitude or longitude sections of the computer must be capable of allowing for the passing of the datum level, and sensing circuits 210, 220 are provided for this purpose. These are fully described in Specification 985,980. Specifications 803,412, 985,975, 985,976 and 985,978 also are referred to.