Patent GB-1206745-A (GB)
Title: Body motion decoupler
Inventor: HAWES RALPH E JR
IPC: F41G7/22
Filed: 1969-02-17
Abstract: 1,206,745. Radio navigation. GENERAL DYNAMICS. 17 Feb., 1969 [15 March, 1968], No. 8559/69. Heading H4D. A body motion decoupler is described which is an integral part of a proportional navigation guidance system for a vehicle such as an aerial missile 14, Fig. 1. Energy from a radar 10 is reflected from a target 12 to receptor means 16 which are rigidly affixed to the missile 14. In a first embodiment, for a rolling missile, a pair of receptors 20, 22, Fig. 2, such as circularly polarized slip-cast fused silica polyrods, are mounted on the missile body 18 and their outputs are fed directly to respective microwave mixers 24, 26. Separate phase shifters 28, 30 fed by an oscillator 32 and by a phase shift driver 34 are respectively coupled with the mixers 24, 26, which feed into a summer 48. Mounted within the missile body is spinning magnetized free gyroscope 36 around which is provided a position sensing coil 38. The e.m.f. generated in the coil 38 is fed through a gain and phase adjuster 40, a modulator 42, and a filter 44 to the phase shift driver 34. A precession coil 46 is also provided around the gyroscope 36. Output from the summer 48 is fed through an amplitude detector 50, a filter 52, a modulator 54, a phase and gain adjuster 56, and an amplifier 58 to the precession coil 46. Output from the phase and gain adjuster 56 is also fed to the missile control system (not shown). A Hall-effect generator 60 fed by a direct current and by the gyroscope magnetic flux is coupled to both the modulator 42 and the modulator 54 to vary their outputs in accordance with the strength of the flux. In operation, the target angle data #-# (Fig. 1) is derived from the phase difference of the target signals at the receptors 20, 22. The e.m.f. induced in the coil 38 by the spinning magnetized gyroscope 36 is indicative of the position of the gyroscope relative to the missile body 18 and also of any missile body motion # which occurs. It is fed into the circuitry of Fig. 2 and is utilized, together with the receptor outputs, to precess the magnetized gyroscope 36 by inducing a field in the precession coil 46. By properly providing near-unity gain between the coil 38 and the phase shifters 28, 30, any body motion sensed by the fixed body receptors 20, 22 can be cancelled by the body motion sensed by the coil 38 from the magnetized gyroscope 36. The error output from the phase and gain adjuster 56 will therefore be proportional only to the missile to target line of sight rate of change #. In a second embodiment (Fig. 3, not shown), for a non-rolling missile, four fixed receptors are mounted at 90 degree intervals around the periphery of the missile body, and are grouped into two pairs of diametrically opposed receptors. Each pair of receptors is associated with a pair of microwave mixers, a pair of phase shifters, an oscillator, and a phase shift driver. The output of the gyroscope position sensing coil is fed to a gain and phase adjuster, and is then split into two channels, one for each phase shift driver. The outputs of the four microwave mixers are fed to a summer, which is followed by circuitry as in the first embodiment for deriving an error output and a precession coil signal.