Siemens SINUMERIK 840Di Function Manual page 398

Detailed Description
2.3 Setpoint/actual-value system
Reference point approach is executed by the selected measuring system.
Each positioning measuring system must be referenced separately.
For an explanation of actual-value acquisition compensation functions, see:
References:
/FB2/Description of Functions, Extended Functions; Compensations (K3)
For an explanation of encoder monitoring, see:
References:
/FB1/Description of Functions, Basic Machine; Axis Monitoring, Protection Zones (A3)
Switching between measuring systems
You can switch between the two measuring systems using the NC/PLC interface signals:
DB31, ... DBX1.5 (positioning measuring system 1)
and
DB31, ... DBX1.6 (positioning measuring system 2).
References
/FB1/Description of Functions, Basic Machine; Various Interface Signals (A2)
It is possible to switch over measuring systems at any time, the axes do not have to be
stationary to do this. Switchover only takes place if a permissible deviation between the
actual values and the two measuring systems has not been violated.
The related tolerance is entered in machine data:
MD36500 $MA_ENC_CHANGE_TOL (maximum tolerance for position actual-value
switchover).
On switchover, the current difference between position measuring system 1 and 2 is
traversed immediately.
The permissible difference between the actual values of the two measuring systems must be
entered in machine data:
MD36510 $MA_ENC_DIFF_TOL.
This tolerance setting must not be exceeded during cyclical comparison of the two
measuring systems or an error message will be generated.
Related monitoring is not active if MD35510=0, if 2 measuring systems are not
active/available on the axis or if the axis is not referenced (at least current control measuring
system).
Types of actual-value acquisition
The encoder type used must be defined in machine data:
MD30240 $MA_ENC_TYPE (type of actual-value acquisition (position actual value)).
Simulation axes
The speed control loop of an axis can be simulated for test purposes.
The axis "traverses" with a following error, similar to a real axis.
A simulation axis is defined by setting machine data:
MD30130 $MA_CTRLOUT_TYPE[n] (setpoint output type)
and
2-24
Velocities, Setpoint/Actual-Value Systems, Closed-Loop Control (G2)
Function Manual, 08/2005 Edition, 6FC5397-0BP10-0BA0