SCA

• Menu: 4.9.45

Description

The SCA safety sub-function sends a safe output signal via the safe process data that indicates whether the actual position is within a defined positioning range (cam window). The cam window is defined with an upper and lower limit position.

When the cam window is entered, the SCA status bit (parameter group Diagnostics > MOVISAFE® CS.. > F process data) is set. If, following a direction reversal, the cam window is exited in the direction from which the safe cam was approached, the Position hysteresis parameter (parameter group Basic settings) becomes active. The SCA status bit remains set until the limit position ± position hysteresis is reached. This prevents accidental switching of the SCA status bit (toggling), for example, if the drive stops at the lower or upper limit position of the cam window.

If the cam window is exited in the direction of movement without a direction reversal, the position hysteresis has no effect. The status of the SCA status bit changes immediately.

Example: activation of position hysteresis

The following variables are given in the example:

Size	Value
Lower limit position of cam window	80
Upper limit position of cam window	120
Position hysteresis	10

Actual position	Status bit SCA
60	0
70	0
80	1
90	1
100	1
90	1
80	1
70	1
60	0

Actual position	Status bit SCA
60	0
70	0
80	1
90	1
100	1
90	1
100	1
90	1
80	1
70	1
60	0

Actual position	Status bit SCA
60	0
70	0
80	1
90	1
100	1
110	1
120	1
130	0
140	0

To execute the safety sub-function, the following requirements must be met:

• The encoder system must be referenced.

• The cam window must be within the application limits that are defined in the parameter group Encoder function for the position modes Absolute position with limited travel distance or Modulo absolute position.
• The distance between the upper and lower limit positions must be greater than twice the position hysteresis.