Question:
How does the 9300EP positioning controller behave when the position target is reached, while the standstill or the determined final speed (velocity changeover) could still not be reached and the drive must consequently override the target?
Answer:
An
overriding of the position-target by the profile generator (POS-SETPOS) can generally only occur in following cases:
- in general, when the profile parameters (position-target, traversing speed, acceleration, deceleration and final speed) are modified during positioning,
- e. g. when the function 'Neue Fahrprofil-Parameter' (POS-PARAM-RD) is used,
- in case of touch-probe-positioning, when the touch probe residual distance is shorter than the required braking torque,
- when a positioning is not started in standstill, but in starting speed, like a following profile during velocity changeover.
When a motion profile is started in standstill and the traversing profile is not modified during positioning, in the position-target the standstill or the determined final speed is exactly reached (restriction: If a final speed ≠ 0 is preselected, the set traverse path and the acceleration ramp must allow the reaching of the final speed).
In all other cases the position-target may be overridden. Further differentiations of the
behaviour of the positioning controller after override of the position-target can be made dependent on the final speed:
Positioning to
standstill (final speed = 0):
- The drive decelerates with the determined deceleration to the standstill, whereby the position-target is overridden.
- Then the drive reverses, is positioned back to the position-target and is decelerated to standstill.
- Positioning is finished, the message that the target is reached, is set (POS-IN-TARGET) and the program sets are continued to be processed.
Positioning with
velocity changeover (final speed ≠ 0):
- With the determined acceleration/deceleration the final speed is tried to be reached.
- When the position-target is reached, the message, that the target is reached, will immediately be set (POS-IN-TARGET), even if the final speed has not already been reached.
- With the speed that has been reached the processing of the program sets is continued.
- The following positioning will then begin with this speed.
Tip:
By using this behaviour you can achieve e. g. the following:
- The drive positions continuously by velocity changeover and touch probe positioning without stop, when the touch probe signal is set in the corresponding program set.
- Only if the touch probe signal is not set in the touch probe program set, there will be a branch to another program set and positioned e. g. to standstill.
