Chapter 9
173
Logic programming – Function blocks
9.8.12 Ramp down detection
Function block diagram
General description
The Ramp down detection function block checks whether a connected drive has been
stopped, meaning that for a configurable time no pulses have been detected from the
encoder system (e.g. from a HTL encoder or proximity switches). Depending on the
result of this check e.g. a safety door lock can be unlatched.
The ramp down detection is started by a falling edge of the Drive released input
signal. A stop of the drive is detected when no signal change (falling or rising edge) at
any Incremental input has occurred for at least the configured Min. time between
signal changes. In this case the Ramp down ended output will change to High. If the
Drive released input signal becomes High, this will immediately set the Ramp down
ended output to Low and will also cancel a currently running ramp down detection.
During the running state (i.e. while the Drive released input is High) and during the
stop detected state (Ramp down ended output is High) the Incremental inputs are
not monitored for signal changes (see Figure 163).
The function block allows an optional plausibility check of the Incremental inputs to
detect cable interruptions, provided that the encoder provides appropriate signals, e.g.
complementary outputs or proximity switches and a tooth-wheel with 270° tooth width
and 180° phase shift. If the plausibility check is enabled, at least one signal within a
signal pair must be High at any time. The Plausibility error incremental output is set
to High, if this condition is not fulfilled for two consecutive logic cycles. This means that
both inputs of a pair may be Low for the duration of the logic execution time without
causing an error (see also Figure 164).
The Plausibility error incremental output is reset to Low if at least one signal within
a signal pair is High and the Drive released input is Low.
The Fault present output is set to High if any Plausibility error incremental output is
High. The Fault present output is set to Low, if all error outputs are Low.
Figure 158:
Function block diagram for
the Ramp down detection
function block
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