Axis Exception Action
The Axis Exception Action attributes are 64-element array of enumerated bytes that specify the action to take by the device for the associated standard or manufacturer specific exception, respectively. For a given exception, certain exception actions may not be supported. Attempting to do so results in an "Invalid Attribute Value" service error code (0x09). Each device product must specify the available actions for each exception that is supported. If a specific exception is not supported by the device, the only valid exception action enumeration is 'Unsupported'. Attempting to write any other value to the element associated with an unsupported exception results in an "Invalid Attribute Value" service error code (0x09) that is generated while the project is online with the controller. For drives that support
Rockwell Automation
specific axis exceptions, the 64-element CIP Axis Exception Action - RA and CIP Axis Exception Action 2 - RA arrays ares sent to the drive device.Axis Exception Action Definitions
Enum. | Usage | Name | Description |
|---|---|---|---|
0 | Optional | Ignore | Ignore instructs the device to completely ignore the exception condition. For some exceptions that are fundamental to the operation of the axis, it may not be possible to Ignore the condition. |
1 | Optional | Alarm | Alarm action instructs the device to set the associated bit in the Axis Alarm word but to otherwise not impact axis behavior. For some exceptions that are fundamental to the operation of the device, it may not be possible to select this action or any other action that leaves device operation unaffected. |
2 | Optional (XBD) Required (E) | Fault Status Only | Fault Status Only instructs the device to set the associated bit in the Axis Faults word but to otherwise not impact axis behavior. It is up to the controller to programmatically bring the axis to a stop in this condition. For some exceptions that are fundamental to the operation of the device, it may not be possible to select this action or any other action that leaves device operation unaffected. Converters (B) executing a Fault Status Only exception action continue to supply DC Bus Power and do not set the DC Bus Unload bit in Axis Status attribute and therefore do not disable drives in the converter's Bus Sharing Group. |
3 | Optional (FPV) | Stop Planner | Stop Planner instructs the drive device (D) to set the associated bit in the Axis Faults word and instructs the Motion Planner to perform a controlled stop of all planned motion at the configured Max Decel rate. For some exceptions that are fundamental to the operation of the device, it may not be possible to select this action or any other action that leaves device enabled. |
4 | Required (XBD) | Disable | Disable action results in the drive device (D) both setting the associated bit in the Axis Faults word and bringing the axis to a stop based on the factory set "best" available stopping method. This "best" stopping method includes both the method of decelerating the motor to a stop and the final state of the power structure given the expected level of control still available. The level of axis control available depends on the specific exception condition and on the configured control mode. The available deceleration methods are defined by the Stopping Action attribute. (See the Stopping Action section following this table for additional information.)If the application requires exception action that is a more severe stopping action than the factory set "best" method, the controller will initiate that action. If the application requires an exception action that is less severe than the factory set "best" method, the controller will configure the device axis instance for a Minor Fault exception action and handle the fault directly. This may put device and motor components at risk and is only be allowed by the device when there is an opportunity for the device to remain operational. This is important in applications where the value of the product is higher than the value of the motor or device. When the Disable exception action is applied to a converter device (B), stopping action is not applicable (0 = No Action). The final states of Disable or Shutdown for the converter are applicable, however, with Shutdown executing the configured Shutdown Action. In the Shutdown case, the DC Bus Unload bit of the converter's Axis Status attribute is set to generate a Bus Sharing exception on all drives in the converter's Bus Sharing Group. When multiple major faults occur with different stopping actions, the most severe of the associated stopping actions is applied, that is, the stopping action that requires the lowest level of control functionality. This rule also applies to the Stopping Action associated with a Disable Request. |
5 | Required (All) | Shutdown | While the final axis state after a Major Fault is the Major Faulted state, the Shutdown Exception Action forces the power structure into the Shutdown state, immediately disabling the drive's power structure. If Shutdown Action is configured to do so, this action also drops DC Bus power to the drive's power structure. Therefore, the Shutdown action overrides the drive's best stopping method. An explicit Shutdown Reset is required to restore the drive to an operational state. |
6-254 | Reserved | - | |
255 | Unsupported | The Unsupported Exception Action is the value assigned to Exceptions that are not supported by the device. Trying to assign an Exception Action other than Unsupported to an exception that is not supported by the device results in an "Invalid Attribute Value" service error code (0x09). |
Stopping action
Standard stopping actions, listed in decreasing levels of deceleration control, are as follows:
- Ramp Decel
- Current Limit Decel
- Coast
In general, the "best" stopping action is the most controlled deceleration method still available given the exception condition.
The final state of the power structure in response to the Major Fault exception action can be any one of the following states that are listed in decreasing levels of control functionality:
- Hold (stopped with Holding Torque)
- Disable (stopped with Power Structure Disabled)
- Shutdown (stopped with Shutdown Action)
The "best" final state of the power structure is the state with the most control functionality still available given the exception condition.
In all these final states a fault reset must be executed before the axis can be restored to enabled operation and commanded to move.
If a Start Inhibit condition is present at the time of the exception, the best final state for the exception action can only be Disable or Shutdown.
The specific stopping action and final state associated with a given Disable exception action is captured in the Axis Fault Action attribute that is included in the Fault Log record. Axis Fault Action enumerations are as follows:
Enumeration | Description |
|---|---|
Stop Action Enumerations | 0 = No Action 1 = (reserved) 2 = Ramped Stop 3 = Torque Limited Stop 4 = Coast |
State Change Enumerations | 0 = No Action 1 = Hold 2 = Disable 3 = Shutdown |
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