Synchronous controller

Details Synchronous controller Synchronous controller

2000-08-28

2001-11-13

Nappi, Robert E. (Department: 2837)

Electricity: motive power systems

Synchronous motor systems

C318S625000

Reexamination Certificate

active

06316903

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a synchronous controller for controlling a servo motor for driving a robot, a machine tool, etc., with constant torque.
2. Description of the Related Art
FIG. 8
is a diagram to show the configuration of a torque constant synchronous control system for supplying a workpiece to a main spindle with a material supply machine in a related art. In the figure, numeral
31
denotes a workpiece, numeral
32
denotes a main spindle for rotating with the workpiece
32
fixed, numeral
33
denotes a main control servo motor, numeral
34
denotes a main controller, numeral
35
denotes a main control drive for performing position control of the main spindle
32
by the main control servo motor
33
, numeral
36
denotes a material supply machine for supplying the workpiece
31
to the main spindle
32
and also giving a constant load to the workpiece
31
at the workpiece working time, numeral
37
denotes a torque control servo motor, numeral
38
denotes a torque controller, numeral
39
denotes a torque control drive for controlling the torque control servo motor
37
as constant torque so as to enable the material supply machine
36
to give a constant load to the workpiece
31
, and numeral
40
denotes a numerical control for outputting a position command to the main control drive
35
.
At the workpiece working time, the main control drive
35
performs axial position control of the main spindle
32
and the torque control drive
39
performs torque constant control so that the material supply machine
36
gives a constant load to the workpiece
31
during the workpiece working time.
In the torque constant synchronous control system in the related art, the main control drive
35
and the torque control drive
39
are controlled separately and as a result of the torque control drive
39
pressing the material supply machine
36
against the workpiece
31
under constant load by performing torque constant control, the main control drive
35
and the torque control drive
39
are operated synchronously.
FIG. 9
is a diagram to show the configuration of a complex lathe in a related art for working a workpiece in a state in which the workpiece is caught at both ends thereof, disclosed in JP-A-7-186007. In the figure, numeral
41
denotes a workpiece, numerals
42
and
43
denote face drivers touching the end face portions of the workpiece
41
in the vicinity of a rotation axis, numerals
44
and
45
denote head stocks on which a main spindle is mounted, numerals
46
and
47
denote Z-axis servo motors for driving the head stocks
44
and
45
, numerals
48
and
49
denote servo amplifiers for driving the Z-axis servo motors
46
and
47
, and numeral
50
denotes a numerical control (NC) for issuing a command to the servo amplifiers
48
and
49
and controlling the Z-axis servo motors
46
and
47
.
The complex lathe in the related art is a lathe for working the workpiece
41
while synchronously operating the head stocks
44
and
45
with the workpiece
41
sandwiched at both ends between the face drivers
42
and
43
attached to the head stocks
44
and
45
. At this time, the NC
50
performs torque constant synchronous control for synchronously operating the head stocks
44
and
45
with the workpiece
41
sandwiched therebetween at constant torque for at least either of the head stocks
44
and
45
.
FIG. 10
is a block diagram of the complex lathe shown in FIG.
9
. In
FIG. 10
, numerals
48
and
49
denote the servo motors, numeral
50
denotes the NC, numerals
51
a
and
51
b
denote parameters for setting data required for computing axis move data, etc., numerals
52
a
and
52
b
denote torque limit amounts for determining the torque amounts of the Z-axis servo motors
46
and
47
, numerals
53
a
and
53
b
denote position feedback of the Z-axis servo motors
46
and
47
for driving the head stocks
44
and
45
, numerals
54
a
and
54
b
denote press completion determination means for determining the head stocks
44
and
45
pressing against the workpiece
41
, numerals
55
a
and
55
b
denote position command values for moving the head stocks
44
and
45
toward the workpiece
41
, numerals
56
a
and
56
b
denote torque control means for controlling torque based on the torque limit amounts
52
a
and
52
b
, and numerals
57
a
and
57
b
denote power amplifiers for driving the Z-axis servo motors
46
and
47
.
In the complex lathe in the related art, to hold a workpiece, the head stocks
44
and
45
are moved toward the workpiece
41
and the face drivers
42
and
43
come in contact with the workpiece
41
and if it is made impossible to move the head stock
44
,
45
and the error amount from the position command value is increased, the torque control means
56
a
,
56
b
cuts the torque to the torque limit amount
52
a
,
52
b
and outputs the cut torque to the power amplifier
57
a
,
57
b
, thereby performing torque constant control.
In a state in which the torque is output so as to become the torque limit amount
52
a
,
52
b
, when the press completion amount becomes less than (position command value
55
a
—position feedback
53
a
) or the press completion amount becomes less than (position command value
55
b
—position feedback
53
b
), the press completion determination means
54
a
,
54
b
determines the pressing to be complete, and stops increasing the position command value.
The complex lathe in the related art is a lathe for sandwiching the workpiece
41
between the head stocks
44
and
45
at constant torque for holding the workpiece
41
and working the workpiece
41
in the state as in the above-described sequence.
In the torque constant synchronous control system in the related art shown in
FIG. 8
, as a result of the torque control drive
39
pressing the material supply machine
36
against the workpiece
31
under constant load by performing torque constant control, the main control drive
35
and the torque control drive
39
are operated synchronously. Thus, the torque constant synchronous control system cannot be used in applications wherein the torque control drive
39
cannot follow the motion of the main control drive
35
, for example, applications at the rapid acceleration or deceleration time or when excessive backlash exists because the workpiece
31
may fall out from the material supply machine
36
because of insufficient press load or may become deformed because of excessive press load; this is a problem of the torque constant synchronous control system.
To avoid torque instability of the press load caused by the fact that the torque control drive
39
cannot follow the motion of the main control drive
35
, a method of performing only torque constant control at the stop time and inputting a position command as a synchronous pattern from an external control section and accomplishing synchronous operation under position control at the moving time may be adopted. However, any of the following:
a. backlash caused by the mechanical structure of the torque control drive
39
, the material supply machine
36
,
b. torque variation caused by position droop variation caused by a warp in the workpiece
31
, etc.,
c. press load instability caused by counter force of synchronous shafts,
d. position droop at the torque constant control time, or the like may induce mechanical vibration because of excessive output of a torque command at the position control switch time, and it is difficult to perform stable and high-accuracy synchronous control; this is a problem.
Further, in the complex lathe in the related art shown in
FIGS. 9 and 10
, torque constant control of pressing with the torque limit amount set is executed and acceleration/deceleration based on acceleration/deceleration torque larger than the setup torque limit amount at the torque constant synchronous control time cannot be executed, thus the complex lathe cannot be used in applications wherein rapid load variation exists; this is a problem.
SUMMARY OF THE INVENTION
The invention is inte

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