Patent GB-1267342-A (GB)
Title: Electro-mechanical function generator
Inventor: HAIGH RICHARD WOOLLISCROFT
IPC: F02D41/30
Filed: 1968-01-24
Abstract: 1,267,342. Generating functions of two. variables. JOSEPH LUCAS (INDUSTRIES) Ltd. 22 April, 1969 [24 Jan., 1968], No. 3653/68. Heading G4G. [Also in Division G1] Electromechanical apparatus for generating a function of two independent variables comprises a support 72 and a capacitative pick-up 75 movable in mutually transverse directions, the support bearing a number of conductors 74 defining a family of non-intersecting curves which represent graphs of the function against one of the variables v for a number of values of the other variable p. The support 72 and pickup 75 are carried on the ends of similar cranked levers pivoted at 17, 17<SP>1</SP> and actuated by coils 78, 79 and return springs 76, 77. The conductors 74 represent graphs in Cartesian co-ordinates of the first variable v and a current proportional to this variable is fed to the coil 78 and determines the position of the support 72. The conductors 72 are joined to the junctions of a chain 73 of impedances, e.g. resistances, across which an A.C. signal at about 5 kHz. is applied from an oscillator 84. A mechanism 86 having an output which represents the second variable p determines the position of the earthed slide of a potentiometer 85 connected across the impedance chain 73. The arrangement is such that one of the conductors 74 (determined by the instantaneous value of p) will be at earth potential and the phase of the signal picked up by the pick-up 75 will depend upon its position relative to this conductor. The A.C. output of the pick-up is fed to a tuned amplifier 88 having zero phase-shift and the output of the amplifier is fed to a phase-sensitive rectifier 89 which also receives a reference signal from the oscillator 84. The sign of the D.C. output of the rectifier depends upon the phase of the pick-up signal. The D.C. signal is amplified by amplifier 91 and fed to the coil 79 in such a way that the pick-up is driven towards whichever conductor 74 is at earth potential. The pick-up reaches an equilibrium position in which the driving current in coil 79 is sufficient to balance the tension in the spring 77. This current represents the required function of the two variables and part of it is fed via amplifier 92 to an output mechanism 93, 94, 95, 96. The apparatus may be applied to an I.C. engine, the device 94 being a fuel meter for the cylinders, the generator 80 of variable v being a tachometer and the mechanism 86, which determines p, a pressure transducer connected to the inlet manifold. Further control parameters may be introduced by connecting in the output of amplifier 91 resistors sensitive to the temperature of the atmosphere and the engine coolant. The support plate 72 of conductors 74 may be replaced by a cylinder or part-cylinder which rotates about an axis perpendicular to the axis of rotation of the pickup. The coil 79 and spring 77 may be replaced by a servo-mechanism in the form, e.g. of a motor driven cam which drives the pick-up to a position of zero input. Provided the impedance of the conductors 74 is sufficiently high, the chain of resistors 73 may be replaced by a chain of capacitors or inductors. In order to obtain smooth interpolation, the pick-up is wide enough to span the gap between two conductors 74. If the input p happens to be an electric oscillatory signal the potentiometer slide is dispensed with and the oscillatory source connected to one end of the impedance chain (Figs. 9, 10, not shown). Mechanical details.-The magnetic circuit for coils 78, 79 (not shown in Fig. 2) comprises bar magnets 11, 12, Fig. 2, with arcuate air gaps 32, 33. Fixed to the ends of magnet 12 are yokes 13, 14 each carrying a pair of bushes 17 and a bracket 15 or 16 to which the fixed end of a return spring is anchored. The lever systems 9 and 53, respectively for the pick-up arm 48 and support plate 59, are mounted for rotation in bushes 17 and are of similar construction. Arms 29 of lever system 9 extend on either side of the magnets 11, 12 and support between them the coil 79 with the arcuate end of magnet 12 extending through the coil. One end of return spring 45 is anchored to one of the arms 29. Electrical connections to the coil are made via the spring anchorages. The lever is also provided with arms 25 which carry between them a counterweight 27. The support 59 is in the form of a glass plate and the conductors and impedances may be printed on it. The pick-up consists of a screened lead 49 the end of which lies adjacent to but insulated from the conductors on the support.