State Machine

The behavior of the system is managed by the state machine. The state machine for main axes is shown in next diagram. The states with bold line are superstates that have substates inside. In order to make the state machine more understandable, for some superstates their inner substates are not shown, and the “Not shown substates inside” label is shown. Refer to the diagrams bellow to get information about the inner substates for those superstates.

For elevation axis the CW substates are skipeed.

@startuml state NoInternalErrors ##[bold]{ state Idle state On ##[bold] { state PoweringOn ##[bold] PoweringOn : Not shown substates inside state Enable state DiscreteMove state JogMove state Homing ##[bold] Homing : Not shown substates inside state Tracking state Stopping state PoweringOff ##[bold] PoweringOff : Not shown substates inside state Exit<<exitPoint>> [*] --> PoweringOn PoweringOn --> Enable Enable --> DiscreteMove : Move DiscreteMove --> Enable : MoveCompleted Enable --> JogMove : MoveVelocity JogMove --> Stopping : Stop Stopping -left-> Enable : StopCompleted Enable -right-> Homing : Home Enable --> Tracking : EnableTrack Homing -left-> Enable : HomeDone Homing -left-> Enable : HomeFailed Tracking --> Stopping : Stop Enable -left-> PoweringOff : Power (off) PoweringOff -left-> Exit } state Fault ##[bold] Fault : Not shown substates inside state Reset##[bold] Reset : Not shown substates inside [*] --> Idle Idle -down-> On : Power (on) On -left-> Fault : Alarm Fault -up-> Reset : Reset Idle -left-> Reset : Reset Reset -right-> Idle : ResetFinished Exit -up-> Idle } state InternalErrors ##[bold] state CommandMemory state Init [*] -down-> CommandMemory CommandMemory -down-> Init : MemoryOk Init -down-> NoInternalErrors : InitOK NoInternalErrors -up-> InternalErrors : Error InternalErrors -left-> Init : Reset @enduml

For PoweringOn superstate the inner substates are shown in next diagram. All states named powering are states to power on elements.

@startuml state PoweringOn{ state HornAndLight state ClearingErrorsEIB state PoweringEIB state ResettingAxis state ClearingErrorsCW state PoweringCW state ApplyOffset state EnablingElectricalAngleFromEncoder state EnablingAxis state EnablingTrackingCW state ReleasingBrakes [*] -->HornAndLight HornAndLight-->ClearingErrorsEIB : GoOn ClearingErrorsEIB-->PoweringEIB : ClearErrorsEIBDone PoweringEIB-->ResettingAxis : PowerEIBDone ResettingAxis-->ClearingErrorsCW : AxisResetDone ClearingErrorsCW --> PoweringCW : ClearErrorsCWDone PoweringCW-->ApplyOffset : PowerCWDone ApplyOffset-->EnablingElectricalAngleFromEncoder : GoOn EnablingElectricalAngleFromEncoder-->EnablingAxis : Timer EnablingAxis-->EnablingTrackingCW : AxisEnabled EnablingTrackingCW-->ReleasingBrakes : EnableTrackingCWDone ReleasingBrakes --> [*] :BrakesReleased } @enduml

For PoweringOff superstate the inner substates are shown in next diagram. All states named powering are states to power off elements.

@startuml state PoweringOff{ state DisablingAxis state EngagingBrake state ResettingDrives state StoppingCW state PoweringCW state PoweringEIB [*] --> DisablingAxis DisablingAxis --> EngagingBrake : AxisDisabled EngagingBrake --> ResettingDrives : BrakesEngaged ResettingDrives --> StoppingCW : Timer StoppingCW --> PoweringCW : CableWrapStopDone PoweringCW --> PoweringEIB : PowerCableWrapDone PoweringEIB --> [*] : PowerEIBDone } @enduml

For Homing superstate the inner substates are shown in next diagram.

@startuml state Homing{ state startingEIBreferenceMode state FindingReference state StoppingAxis state Stabilization state SetAbsolutionPosition state NoReferenceStopping state Join <<Join>> state StoppingReferencing [*]-->startingEIBreferenceMode startingEIBreferenceMode --> FindingReference : StartingEIBReferenceDone / StartMove FindingReference --> StoppingAxis : ReferenceFound StoppingAxis --> Stabilization : StopCompleted Stabilization --> SetAbsolutionPosition : Timer SetAbsolutionPosition --> [*] : GoOn FindingReference --> NoReferenceStopping : Stop FindingReference --> NoReferenceStopping : ReferenceFailed NoReferenceStopping --> Join : StopCompleted startingEIBreferenceMode --> Join : Stop Join --> StoppingReferencing : GoOn StoppingReferencing --> [*] : StoppingReferencingDone } @enduml

For Fault superstate the inner substates are shown in next diagram.

@startuml state Fault{ state StoppingAxis state SafetyStopAxis state EngagingBrakes state DisablingAxis state StoppingCableWrap state PoweringCableWrap state WaitingForReset state fork_state <<fork>> [*]-->fork_state : FaultInitialTranstionActions fork_state --> StoppingAxis fork_state --> SafetyStopAxis StoppingAxis-->StoppingAxis : Check every 100ms StoppingAxis-left->SafetyStopAxis : FollowingError or NoAckFromAxiManager or NotStopping SafetyStopAxis-->EngagingBrakes StoppingAxis-->EngagingBrakes : MoveComplete or AxisManagerFault EngagingBrakes-->DisablingAxis : BrakesReleased or timeout DisablingAxis-->StoppingCableWrap : AxisDisabled or timeout StoppingCableWrap-->PoweringCableWrap : CableWrapStopped or timeout PoweringCableWrap-->WaitingForReset : CableWrapDisabled or timeout WaitingForReset --> [*] : Reset } @enduml

Homing superstate

As described in the EIB hardware working, to get the absolute position of the encoder, a procedure where the axis is moved must be done. Then the obtained reference is applied to the axis manager in order to generate setpoints for absolute values. This superstate, is in charge of managing all the actions to get the system ready to work as absolute position commanding.

The first action of homing procedure is to ask the EIB task to start looking for the reference (see command sequence for more info). Once the EIB is ready, the axis is moved to search for the reference mark. When the reference is found the axis is stopped. Then the system just waits for a stabilization time. This time ensures that the telescope is fully stopped in the desired position. After this time the absolute position published by the axis (Axis control) of the last 50ms is obtained and the mean of that period is applied as absolute position. With the configured stabilization time the error between the actual absolute position and the controlled position is always bellow the noise level of the encoder heads.

Other states of the superstates allow stopping the homing process by the user or to handle a failed reference.

Fault superstate

When entering the fault superstate the axis is commanded to stop, if there is no a FollowingError fault active. In the case the FollowingError is active or the axisManager does not answer to the stop state, state machine will go to safetyStopAxis state instead of to the stoppingAxis state.

In safetyStopAxis the safety system is asked to stop the axis.

The stoppingAxis state is checked every 100 ms (or faster, due to alarm triggers). This state will check if there FollowingError gets active and that the axis is stopping at a minimum speed rate of 1%. If one of these two conditions is not meet, then the safetyStop is triggered.

The stoppingAxis continues to EngagingBrakes if the axisManager detects a Fault or if the axisManager sends a movementCompleted.

The EngagingBrakes continues if Brakes are engaged or a timeout is ocurred.

From next substates up to WaitingForReset, the state machine goes on if the action is completed or a timeout for the action is reached. Also, for those cable wrap states, that are executed only for azimuth, a command failed also makes the system to continue to next state.

In last state WaitingForReset, the state machine will wait for a Reset command from the user or CSC.