Patent GB-1426827-A (GB)
Title: Engine member position predictor
IPC: G01D5/244
Filed: 1973-06-06
Abstract: 1426827 Angular position measurement ESSEX INTERNATIONAL Inc 6 June 1973 [12 Dec 1972] 27074/73 Heading G1N A system for producing signals interpolating between first and second reference position signals derived from a moving member comprises a clockpulse source 22, a first counter 24 for the clockpulses, which counter produces, for every N clockpulses an output pulse which is fed to second counter 28, control means 30 to start and stop the counters in response to the first and second reference signals respectively, first and second storage means 44, 46 for storing the respective counter contents at the second reference signal, a processor 48 for generating location signals having a period proportional to the contents of store 46 (position number), means for successively adding the contents of store 44 (correction number) to itself and means for delaying production of a location signal when the sum is equal to at least a predetermined number. The clockpulse frequency must be adequate to overfill counter 24 between the reference signals. As described, the system produces location signals relating to the rotary position of an I.C. engine. Metal lobes 12, 13, 14, 15 spaced around a rotary part of the engine produces pulses in magnetic transducer 18, each pulse being the second reference signal for the previous period and the first reference signal for the present period. Assuming coincidence between this pulse and a clockpulse (CK) flip-flop 32 and 33 are switched to the Q = 1 state. At the next clockpulse (2), flipflop 33 switches to Q = 0, closes gate 39 preventing clockpulses from reaching the counters and the output LD from NOR gate 38 transfers the readings of counters 24 and 28 to registers 44 and 46, and sets accumulater 70 to 1000000 2 . The next clockpulse (3) switches flip-flop 32 to Q = 0 and produces an output from gate RS which resets counter 28 to zero and counter 24 to 102 allowing for the two blocked clockpulses. The next clockpulse (4) sets flip-flop 33 to Q = 1 and enables gate 39 so that clockpulses flow to counter 24 (capacity 128) and each time this counter fills, it resets and passes a pulse on line 26 to counter 28. Counting is stopped by another reference signal which sets up the next cycle in the same way. The location pulses are produced at terminal 64 by circuits 48 and 66. After registers 46 and 44 have been loaded, the contents of 46 are transferred to down counter 50 by a signal via NOR gates 40 and 57 and one-shot 65. Thereafter counter 50 is counted down by clockpulses, a location pulse D being produced by NOR gate 52 each time the count reaches zero. If the output CO of the full adder 68 is zero, the location pulse is transmitted to terminal L and the counter reloaded via one-shot 65. If the output CO = 1, NOR gate 53 cannot transmit the location pulse, but the next clockpulse triggers flip-flop 72 and thence gates 54 and 55 producing a location pulse delayed by one clockpulse. At each load signal from one-shot 65, the contents of 7 bit register 44 is added to the value in the 7 bit accumulator 70. When this sum exceeds the capacity of register 44 (equal to that of counter 24) the signal at CO becomes a "1" and the pulse is delayed to improve the positional accuracy of the location pulses.