
B–62073E–1/04 2. INTERFACE BETWEEN CNC AND PMC–NA OR NB
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2.3.82 Torque control based on PMC axis control
Usually, position control is applied to the CNC–controlled axes. This function can apply torque control to CNC–
controlled axes, so that the servo motors generate the torque specified by the NC.
PMC axis control is used to switch from position control to torque control. The CNC also controls the position
while torque control is applied. Reference position return is not, therefore, required when torque control is sub-
sequently switched to position control.
(1) Switching from position control to torque control
The following table lists the block data signals and torque control mode signal, which are used for torque
control:
Axis control block data
signal
Specified value or
data range
Data units Description
Axis control command
code signals
CDxX7 ~ CDxX0
0 E H Specifies torque control.
Feedrate specification
signals
FDxX15 ~ FDxX0
1 to 32767 rpm
(cm/min)
Specifies the maximum feedrate to be allowed while
torque control is applied, in rpm. A servo alarm is issued
if there is no object for which a torque is to be generated,
or if the feedrate exceeds the specified maximum while
torque control is applied.
The units are cm/min when a linear motor is being used.
Axis control data sig-
nals
DTxX31 ~ DTxX0
+99999999
to
–99999999
0.00001 Nm
(0.001N)
Specifies the torque data. Specify a positive value when
torque is to be applied in the positive direction, or a nega-
tive value when torque is to be applied in the negative
direction.
The units are 0.001 N when a linear motor is being used.
Torque control mode
signal
TRQMx
Indicates that torque control mode is currently selected.
1 Specifying torque–controlled axes
Specify the axes to which torque control is to be applied, using parameter No. 1951 (TRQX). Specify
the torque constant parameter (No. 1998) for each torque–controlled axis. This parameter can be au-
tomatically set to the standard value specific to the motor, by turning on the power with parameter No.
1804 (DGPRM) set to 0.
2 Controlling the position in torque control mode
Parameter No. 1409 (TRQFU) can be used to specify whether follow–up is to be performed in torque
control mode. When follow–up is not performed, a servo alarm (SV126) is issued if the accumulated
travel (error counter) exceeds the value set in parameter No. 7767. Follow–up is performed upon the
return to position control even if the parameter specifies that follow–up is not to be performed.
3 Direction and speed of movement in torque control mode
In torque control mode, the servo motor attempts to generate the torque specified with the axis control
data signals. The tool is, however, moved in the same direction as in position control, according to
the sign of the torque data, while there is no object for which torque is to be generated or when the
output torque is less than the specified torque. If the feedrate exceeds the value specified with the
feedrate specification signal, a servo alarm (SV125) is issued.
4 Timing for switching to torque control
Switch from another mode to torque control mode once the position deviation has entered the in–posi-
tion range.
5 Changing the torque data
To change the specified torque data in torque control mode, set the new axis control block data (torque
data) in the execution wait buffer, then skip the current block by using the feedrate command skip sig-
nal (VCSKPx).