Tuning Procedures; Overview; Pid Vs. State-Space - Emerson Control Techniques Epsilon Eb Series Reference Manual

Epsilon Eb and EN Drives Reference Manual

Overview

The drive uses closed loop controllers to control the position and velocity of the attached
motor. These position and velocity controllers and the associated tuning parameters are in
effect when the drive is in velocity or pulse mode and have no effect when the drive is in
Torque mode.
Classic closed loop controllers are tuned using proportional, integral and derivative (PID)
gains which require skilled "tweaking" to optimize. The drive uses a revolutionary tuning
approach utilizing state-space algorithms. Using this method a drive can control the motor
more accurately and with more robustness than the older PID algorithms.
The drive's default settings are designed to work in applications with up to a 10:1 load to
motor inertia mismatch. Most applications can operate with this default setting.
Some applications may have performance requirements which are not attainable with the
factory settings. For these applications a set of measurable parameters can be specified which
will set up the internal control functions to optimize the drive performance. The parameters
include Inertia Ratio, Friction, Response and Line Voltage. All the values needed for
optimization are "real world" values that can be determined by calculation or some method
of dynamic measurement.

PID vs. State-Space

The power of the state-space control algorithm is that there is no guessing and no "fine
tuning" as needed with PID methods. PID methods work well in controlled situations but tend
to be difficult to setup in applications where all the effects of the system are not compensated
for in the PID loop. The results are that the system response is compromised to avoid
instability.
The drive state-space control algorithm uses a number of internally calculated gains that
represent the wide variety of effects present in a servo system. This method gives a more
accurate representation of the system and maximizes the performance by minimizing the
compromises.
You need only to setup the system and enter three parameters to describe the load and the
application needs. Once the entries are made the tuning is complete - no guessing and no
"tweaking". The drive uses these entries plus motor and amplifier information to set up the
internal digital gain values. These values are used in the control loops to accurately set up a
stable, repeatable and highly responsive system.
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Tuning Procedures

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