Emerson FM-3 Manuel D’Utilisation

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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.

The power of the state-space control algorithm is that there is no guessing and no “fine 
tuning” as needed with user-specified 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.