FB_FirstOrderIIRFilter (Function Block)

Applies an exponential moving average (EMA) to the input signal.

On the first call the output is set to the current input. On subsequent calls:

\[y[k] = \alpha \cdot u[k] + (1 - \alpha) \cdot y[k-1]\]

where \(\alpha\) is Alpha. A value of 0 passes the input through unchanged. A value of 1 holds the output at the first input value.

Note

The block is FINAL and must be instantiated, not extended. Use FB_init to set fAlpha at declaration time.

Extends: FB_SisoComponent

Properties

Alpha

Type: LREAL

Gets or sets the smoothing factor.

Controls the balance between the current input and the previous output. A value closer to 0 produces a smoother, slower-responding output. A value closer to 1 tracks the input more closely with less smoothing. Values outside 0..1 are clamped.

Methods

FB_init

Inputs

Name	Type	Description
`bInitRetains`	`BOOL`	if TRUE, the retain variables are initialized (warm start / cold start)
`bInCopyCode`	`BOOL`	if TRUE, the instance afterwards gets moved into the copy code (online change)
`fAlpha`	`LREAL`	Smoothing factor. Clamped to 0..1.

Reset

Sets the output to zero. On the next Run() call the output will reinitialise to the current input.

Run

Advances the filter by one time step.

On the first call the output is initialised to the current input to avoid a transient caused by a zero initial state. Subsequent calls apply the exponential moving average.