B-2 Control System MN1902
B.1.1 Current (Torque) control
Setting the control mode to Current Control configures the FlexDrive
II
or Flex+Drive
II
as a
torque amplifier, as shown in Figure 43. Here, a torque reference is obtained from a specified
source.
H Mint / host command (profiled)
H High speed analog input (not profiled)
H Analog input (profiled)
H Fieldbus (profiled).
The source provides a signal that can either be fed directly into the Torque controller (only
when using the high speed analog input source), or through a profiler. The high speed
reference source is ideal for connecting to a motion controller (e.g. NextMove PCI) that will
have already profiled the signal and will provide optimum loop closure.
The profiler generates a torque demand signal that smoothly changes between successive
torque targets (reference values). This is achieved by specifying a rise time and fall time (see
the W orkBench v5 Parameters tool). The torque demand signal is fed into the torque controller
which determines the appropriate amount of current to apply to the windings of the motor.
This demand current is compared with the actual winding current measured from sensors, and
a suitable pulse width modulation (PWM) signal is generated. This PWM signal is fed to the
power electronics in the drive.
Torque
controller
Power stage
+ motor
Torque
demand
PWM
Torque
profiler
Torque
reference
Measured current
High speed
torque reference
Figure 43 - Control structure in Current (Torque) control mode
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