Fault Management

At a Glance

Fault monitoring is essential for position control, due to the inherent risks associated with active moving parts.

The module automatically carries out checks internally.

Fault Types

The module detects 4 fault types:

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 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

Levels of Severity

Faults are classed according to 2 levels of severity:

The blocking or critical faults which cause the moving part to stop in the case 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 indicated,
- the moving part slows down until analog output is zero,
- deactivation of the speed drive enable relay,
- clearing of all memorized commands,
- wait for acknowledgement.
The fault must have disappeared and been acknowledged before the application can be re-started.
Non-critical faults which cause a fault to be signaled without stopping the moving part. The Control Expert must be programmed with what action to take in the event of this type of fault.

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).

Fault Programming

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.

Fault Indication

The module supports a wide range of information in the form of bits and status words, all accessible through the Control Expert program. These bits are used to process faults in hierarchical order :

to act on the main program,
to simply indicate the fault.

Level of Indicating

2 indicating levels are provided:

First level: general information

Bit	Error
CH_ERROR (%Ir.m.c.ERR)	Channel fault
AX_OK (%Ir.m.c.3)	No blocking error (with moving part stop) is detected
AX_FLT (%Ir.m.c.2)	Fault (assembles all faults)
HD_ERR (%Ir.m.c.4)	External hardware error
AX_ERR (%Ir.m.c.5)	Application fault
CMD_NOK (%Ir.m.c.6)	Command refused

Second level: detailed information

Module fault status words and axes CH_FLT(%MWr.m.c.2) and AX_STS(%MWr.m.c.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 Acknowledgement

When a fault appears:

The fault bits AX_FLT, HD_ERR, AX_ERR and the status word extract bits affected by the fault are put in position 1.
If it is a blocking fault, the AX_OK bit is set at 0.

When the fault disappears, all fault bits retain their status. A fault is stored until acknowledgement is obtained by setting the ACK_DEF %Qr.m.c.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 acknowledgement order will only act upon faults which have effectively disappeared. Persisting faults must by 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

Summary Table of the Different Fault Types

The following table summarizes the different fault types and associated bits:

Channel fault (Bit CH_ERROR: %Ir.m.c.ERR)	Process faults (Bit AX_FLT: %Ir.m.c.2)
	AX_OK: %Ir.m.c.3 (No blocking fault detected)		Command refused (CMD_NOK bit: %Ir.m.c.6)
	External hardware (HD_ERR bit: %Ir.m.c.4)	Application (AX_ERR Bit: %Ir.m.c.5)
Internal Communication Configuration External hardware Configuration or adjustment	Emergency stop Drive Encoder break Analog output short circuit Auxiliary output short-circuit Encoder supply Absolute encoder frame	Soft stops Overspeed Recalibration () Tracking error MAX_F1 Tracking error MAX_F2 () Stopping fault () Target window ()	Fault coding in the CMD_FLT word: %MWr.m.c.7

(*) These faults are non-blocking faults and have no influence on the AX_OK bit.

Description of Channel Faults

The CH_ERROR (%Ir.m.c.ERR) bit covers all faults at channel level:

Internal fault MOD_FLT (%MWr.m.c.2.4): module absent, inoperative, or in self-test mode.
Communication fault COM_FLT (%MWr.m.c.2.6): processor communication fault.
Communication fault CONF_FLT (%MWr.m.c.2.5): 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.