Patent GB-693821-A (GB)
Title: Apparatus for simulating radio navigation aids
IPC: G01S1/02
Filed: 1948-10-27
Abstract: 693,821. Electric indicating systems. DEHMEL, R. C. Oct. 27, 1948 [Nov. 12, 1947], No. 27888/48. Class 40 (i) [Also in Groups XXXVI and XL(c)] Training apparatus for simulating the navigation of a craft by means of an omni -directional radio beacon T along a course OD offset from the beacon, comprises means for making an initial adjustment in accordance with the co-ordinates of. point D with respect to the station T and the bearing angle # of the line OD, means for deriving potentials representing the simulated .instantaneous position of, the craft and computing means controlled by these factors for deriving indications of the simulated deviation of the craft from the course-line OD, the distance to the point D and the bearing of the point D with respect to the aircraft heading. Derivation of craft-position co-ordinate potentials, Fig. 4. The meters 11 and 12 indicating simulated airspeed and compass bearing respectively control the airspeed resolver which delivers alternating potentials V x  and V y  proportional to the components of airspeed. The wind velocity and direction are inserted manually on dials 13 and 14 respectively which control the wind-speed resolver which consequently delivers voltages W x , W y  proportional to the components of wind-speed. These potentials are compounded and integrated to produce voltages E x , E y  corresponding to the coordinates of the simulated position of the aircraft with respect to the station T as 'origin. Deviation from course and distance-to-go indication, Fig. 6. The slider arms of potentiometers 45 and 46, fed as shown from an A.C. source, are positioned manually in accordance with the distance TD which is indicated on dial 5. The sinecosine potentiometer 50 is similarly pre-set by means of the dial 4 in accordance with the angle #. Potentials from the potentiometers 45 and 46 are applied to the potentiometer 50 which consequently delivers potentials corresponding to the co-ordinates of the point D with respect to point T. These potentials are compounded with the potentials Ex, Ey derived by the apparatus shown in Fig. 4 in amplifiers 53 and 54 which deliver potentials corresponding to the co-ordinates of the craft measured with respect to the point D as origin. These potentials are applied to the rotary transformer 55 comprising a pair of rotable coils 56, 57 which are displaced through an angle # with respect to fixed coils 58, 59 by manual setting of the dial 3, The signal induced in coil 56 corresponds in magnitude and polarity with the deviation of the craft from the course-line OD and the output from this coil is applied to a phase-sensitive rectifier comprising a double-triode 64 and thence to a meter 65 which indicates the direction and magnitude of the deviation from course. The signal induced in coil 57 is proportional to the distance of the craft from the point D, provided that the deviation of the craft from the course line is small, and the output from this coil is applied to a phase-sensitive rectifier and thence to meter 73 which indicates the distance to go to reach the point D or the distance by which the point D has been passed. A servo arrangement comprising amplifier 77, motor 80, range-measuring potentiometer 84 and dial 78 may also be provided for the distance-to-go indication. Destination-bearing indication Fig. 8. The potentials, derived by the apparatus of Fig. 6, which measure co-ordinates of the craft with respect to the point D, are applied to the fixed coils 86, 87 of a rotary transformer 88, the rotatable coil 89 being rotated by a servo-motor system to a position in which no current is induced therein. This position corresponds to the compass bearing #<SP>1</SP> of the point D from the craft and winding 97 of rotary transformer 96 is positioned in accordance therewith. Winding 102 of selsyn transmitter 101 is rotated in accordance with the heading of the craft as determined by meter 12, Fig. 4. The signals induced in winding 100 are applied to winding 97 which consequently induces potentials in fixed winding 103 corresponding to the difference between craft heading and bearing of point D. These potentials are applied to the winding 104 of selsyn receiver 105, the .rotatable winding 106 of which consequently sets itself in accordance with the bearing of the destination point D with respect to the heading of the craft and positions indicator 107 accordingly. Display of simulated course. Fig. 4. The coordinate potentials E x , E y  are applied as indicated to sine-cosine potentiometers 15 and 16, the slider arms of which are attached to shaft 17 which is also attached to polar chart 18. Selected outputs from the potentiometers are applied to amplifier 22 the output of which energizes one winding of the two-phase motor 20. Generator 24 which is driven by motor 20 applies negative feed-back to the amplifier 22 to increase the stability of the servo-system. Motor 20 rotates shaft 17 until the combined input to the amplifier 22 becomes zero, when the chart 18 is rotated to a position corresponding to the direction of the craft from the beacon. Further outputs from the potentiometers 15 and 16 are applied to amplifier 34 in opposition with the output from a potentiometer 42 the slider arm of which is connected as shown to a lead screw 31 which is driven by motor 32 so that the potentiometer 42 delivers a potential proportional to range. The lead-screw is also connected to a pen 19 which consequently traces the simulated course of the craft on the chart 18. The lead screw is also connected to a further resistor 30 which controls an A.V.C. circuit in amplifier 22 to maintain the sensitivity of the servo system constant for all values of the potentials Ex and Ey. Duplicate apparatus. The amplifiers 53 and 54 Fig. 6 may be duplicated and energized with potentials corresponding to respective "destination" points. A change-over switch enables either pair of amplifiers to be connected into the apparatus and by means of comparing the respective indications on indicator 107 a fix on the simulated position of the craft may be obtained. Specifications 611,304 and 693,890 are referred to.