Electricity: measuring and testing – Electrical speed measuring – Including speed-related frequency generator
Patent
1979-12-13
1982-05-25
Krawczewicz, Stanley T.
Electricity: measuring and testing
Electrical speed measuring
Including speed-related frequency generator
340672, G01P 348, G01P 354
Patent
active
043319173
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
TECHNICAL FIELD
This invention relates to systems for detecting the speed and direction of motion of a moving part by performing logic functions on signal level transitions which are generated as portions of the part travel past a sensor. The system is capable of distinguishing between signals which result from substantially continuous motion of the part and signals which result from intermittent motion reversals or "jitter".
BACKGROUND ART
It is known to determine the motion of a part such as a rotating gear, wheel, or shaft by generating a signal exhibiting alternately opposite transitions between two discrete signal levels as a surface of the part travels past a sensor. Such a signal may be generated by locating a magnetic pickup adjacent the periphery of a gear such that an electrical signal of varying amplitude is produced in the pickup as the gear teeth rotate. The speed of rotation may be readily determined as a function of rate of occurrence of the signal transition. See for example U.S. Pat. No. 4,028,686, issued June 7, 1977 to Michael A. Wilson et al and the prior art cited therein.
In a system of the type described above, signal transitions can result not only from continuous rotation of the gear past the magnetic pickup but also from "jitter"; i.e., intermittent rotation in alternately opposite directions wherein a given gear tooth simply moves back and forth past the magnetic pickup. To distinguish between continuous motion and "jitter" the aforementioned patent to Wilson et al teaches the use of multiple sensors to generate a plurality of phase-shifted signals each representing motion of the same part and the logical combination of those signals to produce a sequence of related signal quantities. True continuous motion is indicated only by the occurrence of a complete sequence of the related signals, a partial sequence being taken as the result of "jitter".
The system of Wilson et al described above exhibits the disadvantage of requiring three or more sensors each with its attendant signal paths and magnetic pickup means. Moreover, the system of Wilson et al does not yield information identifying the direction of part motion or the net travel of a part moving for a significant period of time in one direction and later reversing to move for a significant period of time in the opposite direction.
The U.S. Pat. No. 4,142,152, issued Feb. 27, 1979 to Fincher teaches that the direction of movement of a rotating part can be obtained using only two sensors. However, the rotating part must itself be specially constructed so as to exhibit magnetic sections of precise circumferential length such that the two spaced sensors can be simultaneously actuated by a single magnetic section.
The present invention is directed to overcoming one or more of the problems as set forth above.
DISCLOSURE OF INVENTION
In one aspect of the invention a system is provided for monitoring the motion of a conventional dynamic part such as a rotating gear by generating two phase-shifted signals exhibiting transitions between discrete signal levels. The system distinguishes between continuous motion and "jitter", and, in addition, yields information pertaining to the direction of motion. In general, this is accomplished in a system which comprises sensor means for generating first and second phase-shifted signals which vary cyclically between opposite signal levels at a rate dependent upon the speed of part motion, decoder means connected to receive the first and second phase-shifted signals for generating a sequence of discrete output quantities representing different relationships between the input signal levels, an up/down counter, and logic means interconnecting the output of the decoder means to the counter in such a fashion as to count up when the decoder output sequence occurs in one order, to count down when the decoder output sequence occurs in the opposite order, and to refrain from counting at all unless and until a complete sequence of decoder outputs occurs.
BRIEF DESCRIPTION OF DRAWINGS
F
REFERENCES:
patent: 2926335 (1960-02-01), Bower
patent: 3436656 (1969-04-01), Brano, Jr.
patent: 3728565 (1973-04-01), O'Callaghan
patent: 4028686 (1977-06-01), Wilson et al.
patent: 4142152 (1979-02-01), Fincher
patent: 4142153 (1979-02-01), Smith
Crisp, Asynchronous Direction of Motion Detection, IBM Technical Disclosure Bulletin, vol. 15, No. 1, Jun. 1972, pp. 114, 115.
Crisp, Direction & Speed Detection Circuit, IBM Technical Disclosure Bulletin, vol. 15, No. 4, Sep. 1972, p. 1198, 1199.
Jackson, Logical Motion & Direction Detection, IBM Technical Disclosure Bulletin, vol. 14, No. 12, May 1972, pp. 3672, 3673.
Armstrong, Jr. John T.
Render Michael L.
Caterpillar Tractor Co.
Krawczewicz Stanley T.
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