SIMATIC S7-1500: Rapid Traverse/Creep Speed Positioning (2SpeedPositioning)
An axis can be positioned in many different ways. In this context, especially TIA Portal with the S7-1200 and S7-1500 controller families provides support in the form of technology objects. Very high positioning accuracy of the axis can be achieved. However, this is also reflected in the hardware used to control these axes.
If an axis is to be positioned with relatively little hardware or with lower, controlled accuracy, this can be achieved with the aid of position monitoring and a simple contactor circuit. To this end, the positioning axis can be moved at two different speeds and simply switched off at the desired target position at the appropriate time using a contactor. With this method, called rapid traverse/creep speed positioning, relatively high positioning accuracy of the axis can be achieved.
Controlled positioning in rapid traverse/creep speed mode first moves the positioning axis towards the target position at a high speed (rapid traverse). At a defined position, the speed is switched to a lower speed (creep speed) at which the axis can then be moved to the target position.
To implement the two speed levels of rapid traverse/creep speed positioning, for example, pole-changing motors with a simple contactor circuit or simple frequency converters that allow speed selection through digital inputs can be used. The axis position can be detected with incremental or absolute encoders.
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