Baldor MicroFlex, Installation Manual

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B-4 Control System MN1919
B.1.3 Position (Step and Direction) control
Setting the control mode to Position Control (Step and Direction) configures the MicroFlex as a
positioning system, as shown in Figure 53, capable of following a position command signal.
The up down counter and gearing interpret the step and direction signals and use them to
generate a position demand signal.
The position demand signal is fed into a position controller and used, together with the position
measured from the feedback device, to generate a suitable speed demand signal. If the
position controller is tuned correctly, the measured position will accurately track the position
demand.
The speed demand signal from the position controller is fed into the speed controller and used,
together with the speed measured from the feedback device, to generate a torque demand
signal. If the speed controller is tuned correctly, the measured speed will accurately track the
speed demand.
Finally, the torque demand signal is fed into a 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.
Position
controller
Speed
controller
Torque
controller
Power stage
+ motor
Speed
demand
Torque
demand
PWM
Position
Position
Step
Measured current
Measured speed
Measured position
Direction
Gearing
Pulse
count Up/down
Counter
reference
Figure 53 - Control structure in Position control (Step and Direction)