
4.SERVO FUNCTION DETAILS B-65270EN/05
- 310 -
4.15 TORQUE CONTROL FUNCTION
(1) Overview
In PMC axis control, the torque control function can be used. The
servo motor produces a torque as specified by the NC. Note that the
user can switch between position control and torque control.
(2) Control types
Two types of torque control are supported: type 1 and type 2. The two
types are explained below.
(i) Torque control type 1
The motor produces a torque according to a torque command
specified by the PMC. A servo alarm is issued if the speed of the
motor exceeds the excessive speed alarm level specified by the
PMC.
A block diagram of torque control type 1 is shown below.
ServoPMC
Torque
command
Maximum
allowable
speed
Speed
monitoring
ctual
speed
Excessive
speed alarm
Fig. 4.15 (a) Torque control type 1
(ii) Torque control type 2
The motor produces a torque according to a torque command
specified by the PMC.
When the motor is loaded, it produces a torque according to a
torque command. When it is not loaded, it rotates at a constant
(allowable) speed.
To r que
command
+
Maximum
allowable
speed
To r que
limiter
Speed
control
ServoPMC
Fig. 4.15 (b) Torque control type 2
* Basically, torque control type 2 performs speed control to cause
the limiter to operate on a command from the speed controller
according to a torque command specified by the PMC. This
causes the motor to produce a torque that matches the torque
command when it is loaded and to rotate at a constant (allowable)
speed when it is not loaded.