Axis states (state diagram)

The state diagram displayed in the following defines the state of an axis and the state change from one state to another. It also shows which Motion Control function blocks are required for the state change and in which order they have to be carried out. Several Motion Control function blocks can be instructed at the same time.

State diagram (PLCopen state machine)

Accessible from all states: An error has occurred in the axis.

Accessible from all states: MC_Power . Status = FALSE and no error active

MC_Reset AND MC_Power . Status = FALSE

MC_Reset AND MC_Power . Status = TRUE AND MC_Power . Enable = TRUE

MC_Power . Enable = TRUE AND MC_Power . Status = TRUE

MC_Stop . Done = TRUE AND MC_Stop . Execute = FALSE

Comments on the state diagram
  • The state diagram refers to a single axis.
  • The axis is always in one of the states defined above.
  • For multi-axes movements, the following applies: Master and slave axes can be in different states. For each axis involved, the state diagram displayed above applies. Coupling a slave axis does not affect the state of the master axis.
  • The arrows between the states mark possible state changes (transitions). The dashed arrows mark state changes due to a motion command as well as system or error-dependent state change.
  • Motion commands are always processed sequentially.
  • The motion commands that cause a state change are listed above the corresponding state. The state change also changes the motion profile.
"Disabled" axis state

The " Disabled " device state describes the basic state of an axis:

  • The axis is inhibited.
  • No motion commands can be carried out.
  • There is no error in the axis.
Enable axis (switch on motion readiness)

The " Disabled " state changes to the " Standstill " state by calling the FB MC_Power when Enable = TRUE. Before the state change takes place, the axis reports the "axis is ready to move" state via MC_Power . Status = TRUE.

Axis state "Standstill"
  • The axis is enabled.
  • There is no error in the axis.
  • NO motion commands are active.
Note!

Please observe the following when using setpoint-manipulating FBs (particularly L_MC1P_AverageFilterSetValue and L_CT1P_OscillationComp ):

  • PLCopen status "Standstill" is entered as soon as the unmanipulated setpoint selection reaches a standstill.
  • For standstill detection in the application, the following can be used in addition if necessary: outputs xStandstillActVelocity and xInPosition in FBs MC_ReadMotionState or L_MC1P_AxisBasicControl , as well as output xInEqOut of the setpoint-manipulating FB.
Note!

When the FB MC_Stop is called in the " Standstill " state, it is changed to " Stopping " and then back to " Standstill " if the Execute input is reset to FALSE.

  • The " Stopping " state remains active as long as the Execute input is set to TRUE.
  • The Done status output is set to TRUE if the axis has been stopped via the deceleration ramp set at the FB MC_Stop .
Inhibit axis again (switch off motion readiness)

Except for " ErrorStop ", a change from every state to the " Disabled " basic state is possible by resetting the Enable input of the FB MC_Power to FALSE. The change is direct. All active motion commands are aborted (" CommandAborted ").

Axis state "ErrorStop"

The " ErrorStop " state has the highest priority and gets active in the event of an error. The error can be caused by a function block in the application or a monitoring function of the axis data. A change to the " ErrorStop " state also takes place if the connected drive has changed to an error state. For this purpose, the error bit in the status word is evaluated cyclically.

  • The axis is braked to standstill (unless it is already at standstill).
  • No further motion commands can be carried out.
  • The error occurred is displayed in the axis data and can be provided via the AxisErrorID output of the FB MC_ReadAxisError .
  • If in case of a drive error the device-specific error number is transmitted as PDO, it will be displayed in the axis data and can be provided via the DriveErrorID output of the FB MC_ReadAxisError .
  • A warning of the drive is signalled via the DriveWarning output of the FB MC_ReadAxisError .
  • The axis can be enabled or inhibited via the Enable input of the FB MC_Power (if permitted by the drive) without causing a state change to " Standstill " or " Disabled ".
  • The ErrorStop state can only be left by acknowledging the error via the FB MC_Reset if the error cause has been removed. Depending on the Enable input of the FB MC_Power , a change then takes place to " Standstill " or " Disabled ".