User guide

Control Loops CME 2 User Guide
132 Copley Controls
11.7.4: Position Loop Gains
The following gains are used by the position loop to calculate the velocity command:
Gain
Description
Pp -
Position loop
proportional
The loop calculates the position error as the difference between the actual and
limited position values. This error in turn is multiplied by the proportional gain
value. The primary effect of this gain is to reduce the following error.
Vff -
Velocity feed forward
The value of the profile velocity is multiplied by this value. The primary effect of
this gain is to decrease following error during constant velocity.
Aff - Acceleration feed
forward
The value of the profile acceleration is multiplied by this value. The primary effect
of this gain is to decrease following error during acceleration and deceleration.
Gain Multiplier
The output of the position loop is multiplied by this value before being passed to
the velocity loop.
11.7.5: Position Loop Feedback
Some Copley Controls amplifiers feature dual-sensor position loop feedback, configured
as follows:
 Single sensor. Position loop feedback comes from the encoder or resolver on the
motor.
 Dual sensor. Position loop feedback comes from the encoder attached to the load.
(Note that in either case, velocity loop feedback comes from the motor encoder or
resolver.) For more information, see Feedback Notes (p 52).
Position Loop Output
The output of the position loop is a velocity command used as the input to the velocity
loop.
11.7.6: Position Wrap
The position wrap feature causes the position reported by the amplifier to “wrap” back to
zero at a user-defined value instead of continually increasing. Once set, the reported
position will be between 0 and n-1 where n is the user entered wrap value. This feature is
most useful for rotary loads that continually turn in one direction and only the position
within a revolution is of interest to the user.
Relative moves with the wrap value set will move the relative distance called for. Example;
if the wrap value is set to 1000 and a relative move of 2500 is commanded, the axis will
turn 2 ½ revolutions.
Absolute moves will move the shortest distance to arrive at the programmed position. This
could be in the positive or negative direction. Moves programmed to a point greater then
the wrap value will cause an error.
To configure the position wrap feature, see Enter Basic Position Loop (p. 124).