West Control Solutions N8840 - Manual (Page 20)

Optimization at the set-point for 3-point stepping controller
With 3-point stepping controllers, the pulse attempt can be made with or without
position feedback. Unless feedback is provided, the controller calculates the
motor actuator position internally by varying an integrator with the adjusted
actuator travel time. For this reason, precise entry of the actuator travel time
(tt), as time between stops is highly important. Due to position simulation, the
controller knows whether an increased or reduced pulse must be output. After
supply voltage switch-on, position simulation is at 50%. When the motor actuator
was varied by the adjusted travel time in one go, internal calculation occurs, i.e.
the position corresponds to the simulation:
Simulation actual position
Internal calculation
tt
Internal calculation always occurs, when the actuator was varied by travel time
tt in one go , independent of manual or automatic mode. When interrupting the
variation, internal calculation is cancelled. Unless internal calculation occurred
already after self-tuning start, it will occur automatically by closing the actuator
once.
Unless the positioning limits were reached within 10 hours, a significant
deviation between simulation and actual position may have occurred. In this case,
the controller would realize minor internal calculation, i.e. the actuator would be
closed by 20 %, and re-opened by 20 % subsequently. As a result, the controller
knows that there is a 20% reserve for the attempt.
Operation
Self-tuning 20 8840 profiler