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A.1.7.2 Position Loop Tuning using a step move
In the Move Type box select Position Step and select a reasonably small step change. For example
start with a position step change equivalent to 100 counts. Remember that the value entered here is in
”user units” and will therefore be scaled by the scale factor you entered earlier.
With only KVELFF set, you will get very little response. Since the step move demands an instantaneous
change in demand position, the demand speed will only last for one servo tick. The speed loop alone
will not be sufficient to achieve the position step change. The Proportional gain term KPROP should be
used to overcome the following error. Start with a small for of KPROP, for example 1
This will start to achieve the demanded position. As the value of KPROP increases, so will the rise
(response) time. As KPROP is increased further, eventually either an overshoot or ringing will occur.
Both these factors can be reduced by introducing a value for the damping terms KVEL and KDERIV.
The Step Response Statistics tab can be used to analyze the response to the step move:
A.1.7.3 Position Loop Tuning using a trapezoidal move type
Select the ‘Move Type’ as Position Trapezoid and select a move profile (acceleration, deceleration and
slew speed) to reflect the typical move your application will use. Remember that the values entered
here are in “user units” and will therefore be scaled by the scale factor you entered earlier.
With only KVELFF set there will be a resultant Following Error at the end of the move. Start increasing
the value of KPROP and repeat the move. Increasing the value of KPROP should allow the following
error through the slew period and at the end of the move to be almost eliminated.
During the acceleration and deceleration phases, the following error will be greater. This following error
will increase in relation to any increase in the acceleration or deceleration rates.
The KACCEL term can be applied to reduce the following error during the acceleration and deceleration
rates. This term can only be set in Mint WorkBench in the Terminal window.