Integrated Motion on the EtherNet/IP Network
Rockwell Automation Publication MOTION-RM003I-EN-P - February 2018 21
The Motion Control Axis Object supports a No Control application mode where
there is not dynamic motor control function. This mode is often used to support
Feedback Only or Master Feedback functionality where a feedback channel in a
CIP Motion Drive device is serving as a master feedback source to the rest of the
control system. This mode could also be applied to integrated CIP Motion
Encoder device types where the CIP Motion interface is applied directly to an
Encoder.
In this No Control mode of operation, no setpoint value is supplied to the CIP
Motion device using the cyclic data connection, but actual position, velocity, and
acceleration can be supplied by the device to the controller using the cyclic data
channel, if applicable. The No Control mode for Feedback Only functionality is
illustrated in the following diagram:
No Control (Feedback Only)
No Control mode also applies to other CIP Motion device types, such as
standalone Bus Power Converters and dedicated Motion I/O device types. Since
there is no feedback channel that is associated with these device types, no actual
position is returned to the controller.
See also
Control Modes on page 16
Within this basic control paradigm, there is latitude for different control
methods, both closed loop and open loop. By closed loop, it is implied that there is
a feedback signal that is used to drive the actual dynamics of the motor to match
the commanded dynamics by servo action.
In most cases, there is a literal feedback device to provide this signal, and in some
cases the signal is derived from the motor excitation, for example,
sensorless/encoderless operation.
By open loop, it is implied that there is no application of feedback to force the
actual dynamics to match the commanded dynamics. While precision and
performance are the hallmarks of closed loop control, simplicity and economy are
the hallmarks of open loop control.
Control Methods
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