AXY:PLS On/Off delay

PLS (Programmable Limit Switch) is a mechanism by which a system output is triggered when a specified position is reached.

The Problem

In application the use of PLS is to control an external device. Can be a situation that there is an asymmetric behavior in enabling and disabling timing of the device. As the indication to PLS is the position without dependency on the external device there can be a case when the disabling (for example) takes longer then enable and finished later then expected. So the PLS has to be set in different timing depend on the enable/disable of the device.

Solution offered

The solution is by different timing delays that will be define for enable and disable. This timing will be taken into consider when calculating the timing when the PLS has to be set. Again if the disable timing is Tdis then the PLS has to be set Tdis before the original PLS position is reached. The PLS will be calculated
t = (PLSPropagationDelay+Tdis) *1000 + Δt

Limitation

• If the delay time is smaller the the position error delay the time can't be reached. If this option is requested a new look ahead algorithm has to be implement.
• The assumption here is that the enabling-disabling requests are followed each other, so there is no condition for two follow PLS that indicate the same setting (enable/disable).

Properties (suggestion)

PLSEnableDelay

• Type = double
• Range = 0 - MAXD
• Units = ms
• Default = 0
• Scope = Task, Terminal
• Limitation =
• Example = PLSEnableDelay = 4

PLSDisableDelay

• Type = double
• Range = 0 - MAXD
• Units = ms
• Default = 0
• Scope = Task, Terminal
• Limitation =
• Example = PLSDisableDelay = 2

See also

• PLSPropagationDelay
• PLS Timing Issues
  

Manz's Bugs related to this issue:

Issue 5151 F: asymmetric plspropagationdelay