Which products are affected?
TensionControl template V2.0 + V2.2
What happens?
When the gearbox ratio has been changed over by means of the variables g_bGear1 and g_bGear2 the additional torque required for compensating the friction losses in the machine is not precontrolled correctly.
In case of a tension-controlled rewinder the web tension is too low. In case of an unwinder it is too high.
When does the problem occur?
The problem occurs if the friction compensation function of the templates (FrictionCompensation) is used and at the same time the gearbox factor is changed over.
The friction losses in the machine are basically determined by the gearbox. As a result, different gearbox ratios lead to different friction characteristics. However, the template always uses the same characteristic.
Possible diagnostics?
The value in g_MCTRL_nMAct_a shall more or less be equal to the setpoint of the friction compensation g_nMFriction_a if a reel has once been accelerated to any speed and is in the constant speed mode afterwards. The tension setpoint must be equal 0 during this process. If the two values mentioned before differ from each other, the friction compensation is executed according to a wrong friction characteristic.
Short-term measures/recommendations?
The friction characteristic can be identified in case of every gearbox factor possible. The characteristics are to be saved in different arrays. According to the current ratio the corresponding characteristic is to be copied to the array in the template (POUFrictionCompensation.anFrictionCurve_a).
Evaluation:
In closed-loop controlled systems an inappropriate friction compensation is in most cases compensated unnoticed. In case of purely open-loop controlled systems the faulty compensation causes a deviation between tension setpoint and tension actual value.
If this deviation is relevant for the application the cause can easily be identified. A remedy suitable to be applied in practice has been described above.
