Programming
Fault management
Introduction
Fault types
Fault monitoring is essential for position control, due to the inherent risks associated with active moving parts.
The module automatically carries out checks internally.
l l
The module detects 4 fault types: l The module faults.These are internal hardware faults within the module. All the axes controlled by the module are thus affected when this type of fault occurs.
They can be detected during self-tests (on module reset) or during normal operation (I/O fault).
Hardware channel faults external to the module (for example, encoder break).
Application channel faults associated with the axes (for example, tracking l error).
Faults are constantly checked at axis level once the axis is configured.
Command refused channel faults.These are the faults, which may occur during execution of a movement command, a configuration transfer, an adjustment parameter transfer or an operating mode change command.
Note: The axis monitoring parameters may enable or inhibit the checking of some faults.These monitoring parameters can be adjusted in the adjustment screen.
In loop control disabled mode (DIRDV), checking of application faults is inhibited,
In measurement mode (OFF), checking of application faults except soft stop faults, is inhibited
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Programming
Levels of severity
Fault programming
Fault signalling
Faults are classed according to 2 levels of severity: l The blocking or critical faults which cause the moving part to stop in the case l l l l of an axis fault or moving parts managed by the module in the case of a module fault.The following processes then occur: the fault is signaled, the moving part slows down until analog output is zero, deactivation of the variable speed controller enable relay, erasing of all stored commands, l wait for acknowledgment.
The fault must have disappeared and been acknowledged before the application can be re-started.
l Non-critical faults which cause a fault to be signaled without stopping the moving part. The action to be taken when this type of fault is encountered must be programmed in PL7.
The fault signal disappears when the fault has disappeared and has been acknowledged (the acknowledgment is not stored and only comes into effect if the error has disappeared).
Faults can be viewed, corrected, and acknowledged from the debugging screen.
However it can be useful to be able to control the moving part and correct faults from a terminal during operation. For this purpose, all the information and commands necessary are available within the application.
The module offers a wealth of information in the form of bits and status words, all l l accessible through the PL7 program. These bits are used to process faults in hierarchical order: to act on the main program, to simply signal the fault.
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Programming
Levels of signalling
2 signalling levels are provided:
First level:general information
Bit
%Ixy.i.ERR
AX_OK (%Ixy.i.3)
AX_FLT (%Ixy.i.2)
HD_ERR (%Ixy.i.4)
AX_ERR (%Ixy.i.5)
CMD_NOK (%Ixy.i.6)
Error
Channel fault
No blocking fault (with moving part stop) is detected
Fault (for all faults)
External hardware fault
Application fault
Command refused
Second level:detailed information
Module and axis fault status words (%MWxy.i.2 and %MWxy.i.3)
Note: With a blocking fault, it is advisable to stop the sequential processing which is associated with the axis, and correct the fault by controlling the moving part in manual mode.Correction of the fault must be followed by a fault acknowledgment.
Fault acknowledgment
When a fault appears: l The fault bits AX_FLT, HD_ERR, AX_ERR and the status word extract bits affected by the fault are put in position 1.
l If it is a blocking fault, the AX_OK bit is set at 0.
When the fault disappears, all fault bits retain their current status.A fault is stored until acknowledgement is obtained by setting the ACK_DEF %Qxy.i.8 bit to 1 (or by resetting the module).The acknowledgment has to be made after the fault has disappeared (except for soft stop errors)
If several faults are detected, the acknowledgment order will only act upon faults which have actually disappeared.Faults that are still present must acknowledged again after their disappearance.
Note: Faults can also be acknowledged on PLC initialization, or when a new correct command is accepted in the case of a command refused fault
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Programming
Summary table of the different fault types
Description of channel faults
The following table summarizes the different fault types and associated bits:
Channel fault
(Bit %Ixy.i.ERR)
Process faults (Bit AX_FLT:%Ixy.i.2)
AX_OK:%Ixy.i.3 (No blocking fault detected)
External hardware
(HD_ERR bit:%Ixy.i.4)
Application (AX_ERR
Bit:%Ixy.i.5)
Command refused
(CMD_NOK bit:%Ixy.i.6)
Fault coding in the CMD_FLT word:%MWxy.i.7
l l l l l
Internal
Communication
Configuration
External hardware
Configuration or adjustment l l l l l l l
Emergency stop
Drive
Encoder break
Analog output short circuit
Auxiliary output short-circuit
Encoder supply
Absolute encoder frame l l l l l l l
Soft stops
Overspeed
Recalibration (*)
Tracking error
MAX_F1
Tracking error
MAX_F2 (*)
Stopping fault (*)
Target window (*)
(*) These faults are non-blocking faults and have no influence on the AX_OK bit.
l l l
The %Ixy.i.ERR bit covers all faults at channel level:
Internal error (%MWxy.i.2:X4):module absent, inoperative, or in self-test mode.
Communication fault (%MWxy.i.2:X6):processor communication fault.
Configuration fault (%MWxy.i.2:X5):difference between the module position declared in the configuration and the current position.
Note: In order to be updated, the %MW words require a READ_STS command.
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