User Manual

Table Of Contents
Modes Description
Advanced Digital Motor Controller User Manual 147
SECTION 10
Closed Loop Speed and
Speed-Position Modes
This section discusses the controller’s Closed Loop Speed modes.
Modes Description
Close loop speed modes ensure that the motor(s) will run at a precisely desired speed. If
the speed changes because of changes in load, the controller automatically compensates
the output votlage so that the motor maintains a constant speed. Two closed loop speed
modes are available:
Closed Loop Speed Mode
This mode is the traditional closed loop technique where speed is measured with a speed
sensor. The speed is compared to the desired speed and the speed PID control loop
output provides the reference current (if FOC torque gains are set) or voltage (if the FOC
torque gains are zero) commands, in order to reach and maintain that speed. The internal
current control is described in the Field Oriented Control (FOC) operation chapter.
Speed Command
PWM
Motor
Speed Sensor
Speed Feedback
-
PID
FOC Current
Control
FIGURE 10-1. Closed Loop Speed Mode
Closed Loop Speed Position Control
In this mode, the controller computes the position at which the motor must be at every
1ms. Then a PID compares that expected position with the current position and applies
the necessary reference speed (if speed and FOC torque gains are set) or voltage (if the
speed and FOC torque gains are zero) command in order for the motor to reach that posi-
tion. This mode is especially effective for accurate control at very slow speeds.