Electricity: motive power systems – Positional servo systems – Digital or numerical systems
Reexamination Certificate
2001-06-06
2002-06-11
Nappi, Robert E. (Department: 2837)
Electricity: motive power systems
Positional servo systems
Digital or numerical systems
C318S560000, C318S690000
Reexamination Certificate
active
06404160
ABSTRACT:
TECHNICAL FIELD
The present invention in general relates to a numerical control apparatus for synchronous control of two or more spindle motors or servo motors driven in a machine tool. More particularly, this invention relates to a numerical control apparatus capable of realizing synchronous control of higher precision.
BACKGROUND ART
Some of the machine tools are hitherto capable of executing synchronous control of two or more spindle motors or servo motors to be driven. For example, the numerical control apparatus executes the processing program commanded from a paper tape or the like, that is, executes the numerical control process written in the processing program, and the spindle motors or servo motors of the machine tool are driven to process the work as commanded.
FIG. 12
is an essential block diagram showing an outline of a conventional numerical control apparatus for driving spindle motors or servo motors of a machine tool.
As shown in
FIG. 12
, the conventional machine tool comprises a numerical control apparatus
101
for synchronously controlling a motor for driving a reference axis of a lathe and a motor for driving the synchronous axis, a processing program
102
in which a program for numerical control processing is written, the reference axis including a spindle amplifier
120
, a spindle motor
121
, a gear
122
, a reference spindle
123
, and an encoder
124
, and the synchronous axis including a spindle amplifier
140
, a spindle motor
141
, a gear
142
, a synchronous spindle
143
, and an encoder
144
, and the rotating speed of two spindles is synchronously controlled by the numerical control apparatus
101
, and further by closing chucks
125
and
145
, a work
200
is held between the reference spindle
123
and synchronous spindle
143
.
On the reference axis and synchronous axis, the spindle amplifiers
120
and
140
are installed between the numerical control apparatus
101
and spindle motor
121
, and between the numerical control apparatus
101
and spindle motor
121
, respectively, and the spindle amplifiers drive the corresponding spindle motors
121
and
141
. The reference spindle
123
and synchronous spindle
143
installed by way of the gears
122
and
142
are controlled according to the feedback position from the corresponding encoders
124
and
144
. The numerical control apparatus
101
comprises, as shown in the drawing, an analysis processing unit
103
for analyzing the information about the reference axis and synchronous axis, an interpolation processing unit
104
for issuing the interpolation position command or rotating speed command analyzed in the analysis processing unit
103
to subsequent circuits, a PLC circuit
105
for issuing a specified signal, a machine control signal processing unit
106
for processing the specified signal, a memory
107
for storing a processing program
102
, a parameter setting unit
108
for setting parameters, a screen display unit
109
for displaying the information in the memory
107
on a screen, axis control units
110
a
,
110
b
,
110
c
, . . . for issuing the information about the reference axis and synchronous axis, interpolation position command, and rotating speed command to the subsequent circuits depending on the spindle to be driven, a reference axis control unit
111
which controls the reference axis on the basis of the received information, a synchronous axis control unit
112
which control the synchronous axis on the basis of the received information, and a data input/output circuit
113
for issuing various information to the reference axis and synchronous axis.
The conventional numerical control apparatus will now be explained in detail. Herein, in the spindle motor
121
for driving the reference spindle
123
and the spindle motor
141
for driving the synchronous spindle
143
, the spindle synchronous control is explained.
In
FIG. 12
, for example, the processing program
102
being read in from a tape reader is read out and stored in the memory
107
. Since the spindle synchronous control is a control executed by the spindle synchronous command code, the spindle synchronous command coded described in the processing program
102
is read out into the analysis processing unit
103
in every block from the memory
107
.
The spindle synchronous command code thus being read out is analyzed in the analysis processing unit
103
, and the analysis processing unit
103
notices its analysis result, that is, the information about the reference axis and synchronous axis for synchronous control to the interpolation processing unit
104
.
Receiving this information, the interpolation processing unit
104
notices information about the reference axis, for example, to the axis control unit
110
b
(see
FIG. 12
) assigned to the reference axis, out of the axis control units
110
a
,
110
b
,
110
c
, . . . , and notices information about the synchronous axis to the axis control unit
110
c
(see
FIG. 12
) assigned to the synchronous axis. Herein, the spindle synchronous control is explained, but not in case of spindle synchronous control, for example, information about rotating speed is noticed to the axis control unit
110
a
(see
FIG. 12
) not assigned to either reference axis or synchronous axis. In this case, therefore, information about rotating speed command is directly noticed to the data input/output circuit
113
, and the spindle amplifier
120
receiving this rotating speed command controls the speed of the spindle motor
121
according to this command, and rotates the spindle
123
.
The axis control units
110
a
,
110
b
,
110
c
, . . . are assigned as shown in the diagram for the sake of convenience of explanation, but each axis control unit operates similarly when assigned to the reference axis, assigned to synchronous axis, or not assigned to either.
Consequently, the axis control unit
110
b
notices information about the reference axis, rotating speed command and other information to the reference axis control unit
111
as shown in the diagram, whereas the axis control unit
110
c
notices information about the synchronous axis to the synchronous axis control unit
112
. In the reference axis control unit
111
, the command position of the reference axis is calculated from the received rotating speed command, and notices this command position to the data input/output circuit
113
and synchronous axis control unit
112
. The synchronous axis control unit
112
calculates the command position of the synchronous axis according to the command position of the reference axis noticed from the referenced axis control unit
111
and the information about the synchronous axis is noticed to the data input/output circuit
113
.
Finally, the data input/output circuit
113
notices the received position commands to the spindle amplifiers
120
and
140
, and the spindle amplifier
120
having received the command position of reference axis rotates the reference spindle
123
by controlling the speed of the spindle motor
121
according to the received command position, and further the spindle amplifier
140
having received the command position of synchronous axis rotates the synchronization spindle
143
by controlling the speed of the spindle motor
141
according to the received command position. Thus, in the conventional numerical control apparatus, the synchronous axis control unit
112
controls the command position of the synchronous axis on the axis of the command position of the reference axis calculated by the reference axis control unit
111
, so that spindle synchronous control is executed between one reference spindle
123
and one synchronous spindle
143
.
In the conventional numerical control apparatus, however, synchronous control about two spindles in the machine tool is possible, but this control is limited within a set of reference axis and synchronous axis. It means that three or more spindles cannot be synchronously controlled at the same time.
The reason is as follows. For example, if each axis is synchronized by noticing the command position,
Sagasaki Masakazu
Yamada Yoshinori
Leykin Rita
Mitsubishi Denki & Kabushiki Kaisha
Nappi Robert E.
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