Installation manual

73
Tuning Procedures
The drive uses closed loop controllers to control the position and velocity Travel Limit 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.
Many closed loop controllers require tuning using individual user-specified proportional, integral and derivative (PID)
gains which require skilled “tweaking” to optimize. The combination of these gains along with the drive gain, motor gain,
and motor inertia, define the system bandwidth. The overall system bandwidth is usually unknown at the end of the
tweaking process. The drive closes the control loops for the user using a state-space pole placement technique. Using
this method, the drive’s position control can be simply and accurately tuned. The overall system’s bandwidth can be
defined by a single user-specified value (Response).
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 setup the internal digital gain values. These values are used in the control loops to accurately
set up a stable, repeatable and highly responsive system.
Tuning Procedure
Once the initial setup has been completed, you can run the system to determine if the level of tuning is adequate for the
application. A drive can be tuned basically to four levels.
• No Tuning
• Basic Level
• Intermediate Level
• Fully Optimized Level
Each level is slightly more involved than the previous one requiring you to enter more information. If your system needs
optimization, we recommend that you start with the Basic Level, then determine if further tuning is needed based on axis
performance.
The setup procedures explained here assume that you are using PowerTools Pro software.
Initial Settings
Set the drive tuning parameters as follows:
• Inertia Ratio = 0
• Friction = 0
• Response = 50
• High Performance Gains = Enabled
• Feedforwards = Disabled
Tuning steps
If your Inertia Ratio is greater than 10 times the motor inertia, go directly to the Intermediate Level tuning.
No Tuning
No tuning will be required in most applications where the load inertia is 10 times the motor inertia or less.
Epsilon EP-B Base Drive Reference Manual