Patent GB-798984-A (GB)
Abstract: 798,984. Measuring bearings. NAAMLOOZE VENNOOTSCHAP HOLLANDRE SIGNAALAPPARATEN.Aug. 13, 1954, No. 23596/54. Class 97(2) '[Also in Group XXXVI] The radial component Vx in a reference plane of the velocity of an object D moving in space is determined by evaluating the expression Vx= #Vy dB+C where Vy is the transverse component of velocity, B is the angular co-ordinate of the body in said plane and C is a constant which is adjusted so that Vx corresponds to the rate of change of the radial distance L in said plane. In a first embodiment, Fig. 2, C is adjusted so that Vx #L and in a second embodiment, Figs. 3 and 8, C is adjusted so that # Vx dt=L. A generative tracking system incorporating the Fig. 3 embodiment is described with respect to Figs. 5 and 6 and Fig. 7 (not shown). In this system during a first non-regenerative tracking period the slant range A, bearing B and elevation E of a moving target as determined by a known form of director R, e.g. a radar, are fed to the tracker which computes and stores three constants from which the instantaneous position of the target can be computed assuming that the target is following a rectilinear path with uniform velocity. The tracker is then switched to generative operation in which, condition it computes the co-ordinate values and controls the director in accordance with these values. If the director is not then aimed correctly at the target, signals corresponding to the errors in range, elevation and bearing are generated manually and applied to the tracker to correct the values of the computed co-ordinates and of the stored constants so as to reduce the errors to zero. For semi-generative operation the tracker computes only the angular co-ordinates B, E and accepts the value of A from the director. The three constants are L Vy=L<SP>2</SP>B; the constant C in the expression Vx= # Vy dB+C and the component of velocity Vz perpendicular to the reference plane. The initial digit of each reference numeral denotes the Figure to which it relates. In the first embodiment, Fig. 2, the disc 202 of a ball and disc variable-ratio gearing A is controlled by an input B and the angular displacement of shaft 201 controlling the displacement of the ball carriage 204 is controlled by an input Vy so that the angular displacement of cylinder 203 is equal to # Vy dB and this is applied to one input of a differential gear 205. The other input to differential gear 205 is controlled by a motor 208 and corresponds to the constant C so that the position of output shaft 210 corresponds to Vx and the value of C is determined by comparing, by means of a selsyn transmitter 219 and a control selsyn 206, the position of shaft 210 with the output shaft 217 of a differentiating mechanism B whose position corresponds to L; any difference signal from selsyn 206 being applied through an amplifier 211 to actuate motor 208. The differentiator B is similar to that disclosed in Specification 626,291 [Group XXXVIII] and comprises a ball and disc gearing, the disc 215 being rotated at constant speed and the ball carriage 216 being adjusted by a motor 222 so that the velocity of cylinder 218 corresponds to that of a shaft 213 whose position corresponds to L; when the condition obtains the position of shaft 217 corresponds to L. As shown the motor 222 is controlled by the output voltage from a control circuit comprising the relayer transmitter 219, a differential relayer 220 coupled to the cylinder 218 and a control relayer 221 coupled to the shaft 213, the effect of the relayer transmitter 219 being to stabilize the system. In the second embodiment as shown in Fig. 3 the gearing A and differential 306 correspond to gearing A and differential 205 in Fig. 2 but the output Vx from differential 306 is integrated with respect to time by a ball and disc gearing B whose disc 310 is rotated at constant speed so that the position of cylinder 311 corresponds to # Vx dt and the value of C is adjusted by a motor 321 so that the rate of change of # Vx dt is equal to the rate of change of the position of a shaft 316 which is controlled in accordance with the observed value of L, any difference between these two quantities as determined by the electrical comparison system comprising a differential selsyn. 312, selsyn transmitter 314 and control selsyn 319 being applied to.actuate the motor 321. During regenerative tracking switches 318 and 324 are changed over so that the output from comparison system 312, 314, 319 now controls motor 315 such that the position of shaft 316 corresponds to the computed value of L. If this computed value differs from the observed value of L, a connection is made by rotating handwheel 326 which by means of tacho generators 323, 325 amplifier 320 and motor 321 causes a corresponding rotation of shaft 322 thereby adjusting the value of the constant C and also, by the consequent displacement of selsyn 319 in the comparison circuit 312, 314, 319, adjusting the value of L as given by shaft 316. When the output voltage from tacho generator 325 is very large the rate of correction of the computed value of L may be limited by the restricted range of movement of the ball carriage 308 and this is avoided by a clutch 327 which is operated by the motor control signal from amplifier- 320 such that the clutch is disengaged when said signal exceeds a predetermined value. The motor 321 then rapidly adjusts the setting of the L shaft 316 by means of selsyns 312, 314, 319 and motor 315, and the rate of displacement of handwheel 326 is then reduced thereby reducing the control signal below the predetermined value when the clutch 327 engages and motor 321 thereafter adjusts both the ball carriage 308 and the L shaft 316. Alternatively clutch 327 may be manually operated. In order to reduce the duration of the non-regenerative tracking period, tacho generator 325 may be used to set the ball carriage 308 in correspondence with the expected path of the target; during this initial adjustment switch 324 must be in its regenerative position and clutch 327 must be engaged. Alternatively the ball carriage 308 can be set to a selectable one of a number of predetermined positions by means of a corresponding plurality of control circuits for motor 321. An alternative form of the second embodiment, Fig. 8, uses tacho generators for integrating instead of ball and disc bearings. The shaft 801 of the tacho generator 802 is controlled by B and the resultant output voltage (proportional to B) is multiplied by the factor L Vy by potentiometer 803 and applied to a differential amplifier 807 together with the output from a tacho generator 805 after multiplication by the factor L by means of potentiometer 804, the output from amplifier 807 being applied to actuate a motor 806 which controls tacho generator 805 such that the two inputs of amplifier 807 are equal; when this condition obtains the speed of the motor 806 is proportional to Vy B and consequently its position is proportional to # Vy dB. The constant C is added by a differential gear 810 giving a resultant shaft position Vx which controls a potentiometer 812 to give a corresponding voltage which is integrated by the servo controlled motor 815 so that the position of the motor shaft 816 is proportional to # Vn dt. The position of shaft 816 is compared by means of selsyns 817, 818 with that of the shaft of a motor 820 which corresponds to the observed value of L and any error signal from selsyn 817 actuates a motor 809 to so adjust the value of C that the error is reduced to zero. Feedback tacho generators 808 and 813 are associated with the servo motors 809 and 815 respectively to provide stabilization and an output from the tacho generator 808 is also - applied to the potentiometer 812 and to the amplifier 813 associated with the servo motor 815. During regenerative tracking switch 821 is changed over so that the differential output from selsyns 817, 818 now controls the motor 820 such that the position of its shaft corresponds to the computed value of L. Any necessary correction is inserted by manually rotating a tacho generator 819 which in conjunction with the tacho generator 808 causes a corresponding adjustment of the constant C; the output from the tacho generator 808 to potentiometer 812 and amplifier 813 cause also a direct adjustment of the computed value of L as given by shaft 816. Generative tracking system, Figs. 5 and 6. Computation of constants (all switches in the positions shown). During the non- regenerative tracking period the values of B, A and E as determined by the director appear as corresponding rotations of the shafts 516, 510 and 504 which are transferred to shafts 623, 532 and 533 respectively by means of selsyns 520, 624; 515, 522 and 508, 523 and servo motor 621, 528 and 529. 'Shafts 533 and 532 control the angular and axial positions respectively of a camoid 534 such that the displacements of the cam contacts 535 and 537 are proportional to the plan range L and the height H respectively, these displacements being converted to corresponding rotations of a selsyn tranmitter 536 and a control selsyn respectively. The height H is differentiated in the height register to give the third constant Vz by means of a device substantially as disclosed in Specification 626,291 comprising a ball and disc gearing whose disc 551 is rotated at constant speed, the 'ball carriage 552 being positioned by a servo motor 553 controlled by the output of a control selsyn 538 which is electrically coupled to a selsyn transmitter 547 on the shaft of cylinder 549 such that when the angular position of cylinder 549 corresponds to the displacement of cam pin 537 the position of the ball carriage 552 is proportional to Vz; values of H and Vz are applied to a predictor Rta by selsyns 547 and 556. The differential gear 548 stabilizes the operation of the differentiator as described in