Hit Crossing (Simulink Reference)

Detect crossing point

Library

Discontinuities

Description

The Hit Crossing block detects when the input reaches the Hit crossing offset parameter value in the direction specified by the Hit crossing direction parameter.

The block accepts one input of type double. If the Show output port check box is selected, the block output indicates when the crossing occurs. If the input signal is exactly the value of the offset value after the hit crossing is detected, the block continues to output a value of 1. If the input signals at two adjacent points bracket the offset value (but neither value is exactly equal to the offset), the block outputs a value of 1 at the second time step. If the Show output port check box is not selected, the block ensures that the simulation finds the crossing point but does not generate output.

When the block's Hit crossing direction parameter is set to either, the block serves as an "Almost Equal" block, useful in working around limitations in finite mathematics and computer precision. Used for these reasons, this block might be more convenient than adding logic to your model to detect this condition.

The hardstop and clutch demos illustrate the use of the Hit Crossing block. In the hardstop demo, the Hit Crossing block is in the Friction Model subsystem. In the clutch demo, the Hit Crossing block is in the Lockup Detection subsystem.

Data Type Support

A Hit Crossing block outputs a signal of type boolean if Boolean logic signals are enabled (see Enabling Strict Boolean Type Checking). Otherwise, the block outputs a signal of type double.

Parameters and Dialog Box

Hit crossing offset: The value whose crossing is to be detected.
Hit crossing direction: The direction from which the input signal approaches the hit crossing offset for a crossing to be detected.
Show output port: If selected, draw an output port.
Enable zero crossing detection: Select to enable zero crossing detection. For more information, see Zero Crossing Detection in the Using Simulink documentation.

Characteristics

Direct Feedthrough
Yes

Sample Time
Inherited from driving block

Scalar Expansion
Yes

Dimensionalized
Yes

Direct Feedthrough	Yes
Sample Time	Inherited from driving block
Scalar Expansion	Yes
Dimensionalized	Yes

Ground IC