Zero-Crossing Events

class pathsim.events.zerocrossing.ZeroCrossing(func_evt=None, func_act=None, tolerance=0.0001)[source]

Bases: Event

Subclass of base ‘Event’ that triggers if the event function crosses zero. This is a bidirectional zero-crossing detector.

Monitors system state by evaluating an event function (func_evt) with scalar output and testing for zero crossings (sign changes).

func_evt(time) -> event?

If an event is detected, some action (func_act) is performed on the system state.

func_evt(time) == 0 -> event -> func_act(time)

Example

Initialize a zero-crossing event handler like this:

# define the event function
def evt(t):
    # here we have a zero-crossing at 't==10'
    return t - 10

# define the action function (callback)
def act(t):
    # do something at event resolution
    pass

# initialize the event manager
E = ZeroCrossing(
    func_evt=evt,  # the event function
    func_act=act   # the action function
    )
Parameters:

  • func_evt (callable) – event function, where zeros are events

  • func_act (callable) – action function for event resolution

  • tolerance (float) – tolerance to check if detection is close to actual event

detect(t)[source]

Evaluate the event function and check for zero-crossings

Parameters:

t (float) – evaluation time for detection

Returns:

  • detected (bool) – was an event detected?

  • close (bool) – are we close to the event?

  • ratio (float) – interpolated event location as ratio of timestep

class pathsim.events.zerocrossing.ZeroCrossingUp(func_evt=None, func_act=None, tolerance=0.0001)[source]

Bases: Event

Modification of standard ‘ZeroCrossing’ event where events are only triggered if the event function changes sign from negative to positive (up). Also called unidirectional zero-crossing.

detect(t)[source]

Evaluate the event function and check for zero-crossings

Parameters:

t (float) – evaluation time for detection

Returns:

  • detected (bool) – was an event detected?

  • close (bool) – are we close to the event?

  • ratio (float) – interpolated event location as ratio of timestep

class pathsim.events.zerocrossing.ZeroCrossingDown(func_evt=None, func_act=None, tolerance=0.0001)[source]

Bases: Event

Modification of standard ‘ZeroCrossing’ event where events are only triggered if the event function changes sign from positive to negative (down). Also called unidirectional zero-crossing.

detect(t)[source]

Evaluate the event function and check for zero-crossings

Parameters:

t (float) – evaluation time for detection

Returns:

  • detected (bool) – was an event detected?

  • close (bool) – are we close to the event?

  • ratio (float) – interpolated event location as ratio of timestep