Method CatchAndMove

Alignment method CatchAndMove first applies a low current to gently align the magnetic fields by changing the commutation angle. Subsequently, by changing the commutation angle in opposite direction while applying a higher current the method determines whether the alignment was successful. Overall, this method can be split into four phases. This section describes these phases and visualizes them in Current and commutation angle (demand and actual) profile for method CatchAndMove.

1. Phase I:

   1. Ramp: The commutation angle is forced to PositiveAngle or NegativeAngle depending on the sign of DeltaAngle and the current is ramped to LowCurrent in RampTime seconds.

   2. Hold: Both the demand angle and the current are fixed for HoldTime seconds.

2. Phase II:

   1. Move: The commutation angle is increased to the angle set in step 1.a plus DeltaAngle in MoveTime seconds and the current is held at LowCurrent.

   2. Hold: The demand angle is held at the value set in 2.a and the current is held at LowCurrent during HoldTime seconds.

3. Phase III:

   1. Ramp: The demand angle is left unchanged compared to the value set in step 2.a while the current is ramped up to HighCurrent in RampTime seconds.

   2. Hold: The demand angle and the applied current are held at the value reached in step 3.a for HoldTime seconds.

4. Phase IV:

   1. Move: The demand angle is set to to PositiveAngle or NegativeAngle depending on the sign of DeltaAngle in MoveTime seconds and the current is unchanged compared to the value set in step 3.b.

   2. Hold: The demand angle and the applied current are held at the value reached in step 4.a respectively step 3.a for HoldTime seconds.

Two optional limit switches can be connected. The input LimitSwitchPositive (if DeltaAngle \(\geq\) 0) or LimitSwitchNegative (if DeltaAngle \(<\) 0) is monitored at the start and end of each Ramp section and during the whole Move section. If the input is active during any point while monitoring, the alignment method is repeated once with opposite sign of DeltaAngle.

After completion of all phases the alignment error ActualError \(\epsilon\) is calculated as:

\[\epsilon = \left \lvert 1-\frac{a-b}{A-B} \right \rvert\]

When ActualError exceeds the configured ErrorMargin and no limited switches were configured the alignment method is repeated once with opposite sign of DeltaAngle. In all cases, with or without alignment inputs configured, alignment is aborted and the alignment state goes to Error if the retry is unsuccessful.

At the end of successful execution of this alignment method, the commutation offset \(\Theta\) is calculated as:

\[\Theta = \frac{(A-a)+(B-b)}{2}\]

Current and commutation angle (demand and actual) profile for method CatchAndMove

Signals

The signals applicable for this method are given in Alignment signals for method CatchAndMove.

Alignment signals for method CatchAndMove

Name	Data type	R/W	Description
PositiveAngle	Float	RW	Positive initial angle [rad], supported interval \([0,2\pi]\).
NegativeAngle	Float	RW	Negative initial angle [rad], supported interval \([0,2\pi]\).
DeltaAngle	Float	RW	Angle to move [rad], supported interval \([-4\pi,4\pi]\).
HighCurrent	Float	RW	High current.
LowCurrent	Float	RW	Low current.
RampTime	Float	RW	Ramp time [s].
HoldTime	Float	RW	Hold time [s].
MoveTime	Float	RW	Move time [s].
ErrorMargin	Float	RW	Maximum error margin \([0,1]\).
ActualError	Float	R	Calculated error \([0,1]\).

Inputs

For this method two limit switches can be connected and monitored. The inputs are given in Alignment inputs for method CatchAndMove.

Alignment inputs for method CatchAndMove

Input name	Description
LimitSwitchPositive	Input optionally connecting to signal containing value of positive limit switch.
LimitSwitchNegative	Input optionally connecting to signal containing value of negative limit switch.

Run exceptions

The CatchAndMove alignment method can fail with the run exceptions given in Alignment run exceptions for method CatchAndMove.

Alignment run exceptions for method CatchAndMove

Run exception	Description
TimeoutException	The configured timeout was exceeded.
AbortedException	The alignment procedure was aborted due to one of the following reasons: Axis left state Operation enabled, e.g. to Fault, during alignment procedure. Determined ActualError is larger than configured ErrorMargin. Limit switch activated during retry of alignment. The exact abort reason is given by the exception message available via the RunException property on the Alignment interface.