Communications: electrical – Continuously variable indicating – Using a particular modulation
Patent
1988-09-13
1990-01-30
Yusko, Donald J.
Communications: electrical
Continuously variable indicating
Using a particular modulation
34087042, 324207, 365228, 377 17, 377 26, H04Q 900
Patent
active
048976474
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to absolute position detection in which position detection is performed with high accuracy by interpolation between feedback pulses generated as an object of position detection moves, and more particularly, to a method and an apparatus for absolute position detection, in which the command displacement upon application of power supply can be calculated with high accuracy, the method and the apparatus entailing only small electric power consumption.
BACKGROUND ART
In an absolute positioning system in which pulses of a quantity corresponding to a command displacement, which is obtained by subtracting the present absolute position from a command absolute position, are delivered to effect positioning control, if the present position upon application of power supply is unknown, a reference point return operation must be performed, since the command displacement cannot be precisely calculated on the basis of the command absolute position only. In order to obviate such an awkward situation, as is conventionally known, an absolute position detector, e.g., an absolute pulse encoder, may be subjected to battery-backup so that a detected absolute position upon termination of power supply is retentively stored even after the power is turned off, and the reference point return operation when the power is turned on again can be omitted. As is also conventionally known, feedback pulses, which are generated from a pulse encoder as an object of position detection moves, may be divided by means of interpolation pulses, thereby improving the detection resolution.
However, if an absolute counter and an interpolation counter for counting the feedback pulses and the interpolation pulses, respectively, are both subjected to battery-backup, in order to obtain the advantages of both these prior art arrangements, substantial electric power consumption is required, that is, the system is uneconomical.
DISCLOSURE OF THE INVENTION
The object of the present invention is to provide a method and an apparatus for absolute position detection which permits high-accuracy calculation of a command displacement when the power is on, and entails less electric power consumption.
In order to achieve the above object, a method for absolute position detection according to the present invention comprises steps of: (a) generating a feedback pulse having a polarity corresponding to the moving direction of an object of position detection each time the object of position detection moves for a first predetermined distance; (b) updating a stored value indicative of an approximate absolute position of the object of position detection each time the feedback pulse is generated; (c) generating an interpolation pulse each time the object of position detection moves for a second predetermined distance shorter than the first predetermined distance; (d) storing and retaining the stored value even after the power is turned off; (e) counting the interpolation pulses generated during the time interval which elapses from the instant that the power is turned on again until the first one of the feedback pulses is generated, and temporarily storing the count value obtained; (f) calculating the absolute position of the object of position detection reached when the power is turned on again, in accordance with the stored value retentively stored in the step (d), the count value of the interpolation pulses stored in the step (e), the first and second predetermined distances, and the moving direction designated by a movement command delivered when the power is turned on again.
An apparatus for absolute position detection according to the present invention comprises: a first pulse generating means for generating a feedback pulse having a polarity corresponding to the moving direction of an object of position detection each time the object of position detection moves for a first predetermined distance; second pulse generating means for generating an interpolation pulse each time the object of position detection moves for a sec
REFERENCES:
patent: 4764767 (1988-08-01), Ichikawa et al.
patent: 4779075 (1988-10-01), Zagelein et al.
patent: 4795927 (1989-01-01), Mori et al.
Nakayama Akihito
Sakamoto Keiji
Fanuc Ltd.
Queen Tyrone
Yusko Donald J.
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