Siemens SINUMERIK 840Di Function Manual page 448

Detailed Description
2.5 Optimization of the control
Description
Status of the power enable (pulse enable) of a
machine axis
Predefined range of values:
FALSE: no power enable
TRUE: power enable exists
Activation
The variable is predefined and can be used at any time acc. to the data type BOOL with
FALSE or TRUE. While communication with the drive is not yet established, the value 0
(FALSE) is supplied.
The synchronized actions, in which the variable is evaluated, should preferably be carried
out as soon as the control powers up, e.g. by starting an ASUB from the PLC. To make sure
that the synchronized actions remain continuously active and are not affected by the mode
change, we recommend that they are programmed as "static synchronized actions" (using
IDS as the vocabulary word).
Example
Output of the pulse enable of machine axis X1 to the first digital NCK output in all modes
IDS = 1 DO $A_OUT[1] = $VA_DPE[X1]
Supplementary conditions
The functional expansion is available for digital drives in all control variants providing
synchronized actions.
Control response with POWER ON, RESET, REPOS, etc.
After POWER ON, the value 0 is supplied while communication with the drive is not yet
established. Then, the system variable $VA_DPE always specifies the pulse enable value
acquired at the beginning of the interpolation cycle. The modeindependent evaluation or
retransmission should be carried out using static synchronized actions (vocabulary word
IDS).
2.5.6 Expansions for "deceleration axes"
Application
In the case of designconditioned nonlinearities and elasticities, as often occurs in material
handling and highbay racking technology, it is often necessary to sacrifice the position
control due to the unstable position control loop. The axes are, therefore, traversed closed-
loop controlled and not open-loop controlled. To this aim, the WF723 module offers the
special function of the "deceleration axes".
2-74
NCK variable
$VA_DPE [machine axis]
Velocities, Setpoint/Actual-Value Systems, Closed-Loop Control (G2)
Function Manual, 08/2005 Edition, 6FC5397-0BP10-0BA0