Radiant energy – Photocells; circuits and apparatus – With circuit for evaluating a web – strand – strip – or sheet
Reexamination Certificate
2000-12-21
2002-02-19
Le, Que T. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
With circuit for evaluating a web, strand, strip, or sheet
C250S559330
Reexamination Certificate
active
06348695
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a position detection apparatus. More specifically, this invention relates to a position detection apparatus in which data representing a position of an object to be measured is calculated from an output of a sensor for detecting a position of the object.
BACKGROUND ART
Among position detection apparatus, there are some apparatuses in which data representing a position of an object to be measured is calculated from an output of a sensor, that is, some (not negligible) time is required for obtaining position data from the output of the sensor.
FIG. 10
shows one example of such a conventional position detection apparatus. This position detection apparatus
110
is a so-called optical rotary encoder, which is a type connected to a motor controller
132
by a serial transmission line
131
.
As shown in this figure, the position detection apparatus
110
comprises a light-emitting circuit
111
, a photo-detecting circuit
112
, a scale disc
113
and an amplifier
114
. The position detection apparatus
110
also comprises a sample holding section
115
, a multiplexer
116
, an A/D converter
117
, a microcomputer
18
, a serial signal conversion circuit
119
, and a serial signal transmission circuit
120
.
The light-emitting circuit
111
is a circuit including light emission elements
121
, M in number (M is a plural number). The photo-detecting circuit
112
is a circuit including photodetectors
122
, M in number, which convert light from the light emission elements
121
in the light-emitting circuit
111
to electric signals (analog signals), respectively. The scale disc
113
(also referred to as a slit disc or a code-disc) is turntable machined so that the intensity of light incident on the photodetectors
122
in the photo-detecting circuit
112
changes, and by means of the rotation of this scale disc
113
, M sine-wave signals or triangular wave signals having different periods or phases are output from the M photodetectors
122
in the photo-detecting circuit
112
. Sine-wave signals can be output when a scale disc
133
with a sine-wave slit is used. However, sine-wave signals can be output even when a rectangular slit is used. Because, when a rectangular slit is used, a substantially sine-wave signal (pseudo sine-wave signal) can be obtained due to the diffraction effect of the light. The scale disc
133
is generally attached to a rotation shaft of a motor which is controlled by the motor controller
132
.
The amplifier
114
is a circuit for amplifying the output of each photodetector
122
in the photo-detecting circuit
112
. That is to say, the amplifier
114
is a circuit for outputting manalog signals. The sample holding section
115
includes M sample holding circuits respectively connected to M amplifying circuits in the amplifier
114
. All the sample holding circuits in the sample holding section
115
are supplied with the sample holding signals from the microcomputer
118
. That is to say, the sample holding section
115
simultaneously holds M signals which change time-wise, output from the amplifying circuit
114
, when a sample holding signal instructing the holding operation is input, and subsequently continues to output the held M signals.
The multiplexer
116
outputs a signal instructed by the microcomputer
118
, among M signals output from the sample holding section
115
. The A/D converter
117
converts the analog signal output from the multiplexer
116
to a digital signal, and the control of the operation timing of the A/D converter
117
is also performed by the microcomputer
118
.
The serial signal conversion circuit
119
converts a parallel signal from the microcomputer
118
to a serial signal, and supplies the serial signal to the serial signal transmission circuit
120
. The serial signal conversion circuit
119
also performs a processing which is reverse to this. When a predetermined signal is supplied from the serial signal transmission circuit
120
(when a request signal is received by the serial signal transmission circuit
120
, and a signal corresponding to the request signal is supplied from the serial signal transmission circuit
120
), the serial signal conversion circuit
119
outputs a signal for informing the microcomputer
118
of this matter.
The serial signal transmission circuit
120
is an interface circuit with the motor controller
132
. The serial signal transmission circuit
120
prepares a transmission signal by subjecting the serial signal provided by the serial signal conversion circuit
19
to a predetermined processing (calculation of CRC, addition of start bit and stop bit, or the like), and supplies the prepared transmission signal to the motor controller
132
via the serial transmission line
131
. The serial signal transmission circuit
120
also performs a processing for preparing a serial signal corresponding to the transmission signal received from the motor controller
132
.
The microcomputer
118
is a control circuit of the position detection apparatus
110
. The microcomputer
118
includes an input circuit
123
, an output circuit
124
, a CPU
125
and a timer
126
, and the output of the A/D converter
117
is supplied to the CPU
125
via the input circuit
124
. The sample holding signal is output from the output circuit
125
under the control of the CPU
125
. The serial signal conversion circuit
119
is connected to the CPU
125
.
Moreover, though not shown, the position detection apparatus
110
is provided with a circuit for detecting that the scale disc
113
has made one revolution from the output of a specific photodetector
122
in the photo-detecting circuit
112
, and a multi-turn counter for counting how many revolutions the scale disc
113
has made based on the detection result of the circuit, and the multi-turn counter is also connected to the CPU
125
.
The overall operation of the position detection apparatus
110
will now be described, with reference to FIG.
10
and FIG.
11
. In
FIG. 11
, (A) illustrates a timing for the position detection apparatus
110
to receive a request signal from the motor controller
132
, (B) illustrates the time change in a value of a timer
126
in the microcomputer
118
. (C) illustrates the time change in the sample holding signal output from the microcomputer
118
to the sample holding section
115
, and (D) illustrates the time change in the contents of processing executed by the CPU
125
. Finally, (E) illustrates the timing when a position signal is transmitted from the position detection apparatus
110
.
The position detection apparatus
110
is an apparatus which supplies a position signal holding position data representing the position of the scale disc
113
at the time when it receives a request signal from the motor controller
132
via the serial transmission line
131
, as a response to the request signal, via the serial transmission line
131
to the motor controller
132
.
The position data handed over to the motor controller
132
comprises 2-byte data showing how many turns the scale disc
113
has made until then, and 2-byte data related to the angle of rotation of the scale disc
113
. The former data is obtained from the multi-turn counter, and hence required data related to the time can be obtained immediately. The data related to the angle of rotation, however, is calculated by numerical operation based on the output of the photo-detecting section
112
, and hence, relatively long period of time is required for the completion of processing to obtain the data. Accordingly, if it is so constructed that the processing is to be started at the time of reception of the request signal, the position data representing the position of the slit disc
113
at the time when the request signal is transmitted is received, after a while after the transmission of the request signal.
From the view point of the motor controller side, it is convenient that the position data representing the position of the scale disc
113
can be obtained at the time when the request signal is transmit
Okamuro Takashi
Sakuma Hirokazu
Le Que T.
Mitsubishi Denki & Kabushiki Kaisha
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