Filter definition

@FILTER_DEFINITION {
@FILTER_NAME {FilterName} {
@FILTER_TYPE {FilterType}
@FILTER_ORDER {N}
@CUT_OFF_FREQUENCY {Ωc}
@COMMENTS {CommentText}
}
}

Notes

  1. Filters are used to condition the output of signals. Various filter types are available, based on the values of the parameter FilterType.
    • If FilterType = BUTTERWORTH, a Butterworth filter is implemented. This option requires two input parameters, the filter order, N, and cutoff frequency, Ωc.
    • If FilterType = CHEBYSHEV, a Chebyshev filter is implemented.
  2. It is possible to attach comments to the definition of the object; these comments have no effect on its definition.

Example

In this example, a signal SignalTotalLift extracts the total lift of a four bladed rotor; this total lift is shown in fig. 1. Next, a Butterworth low-pass 2nd order filter of this signal is performed; with Ωc = 1.93 rad/sec. Figure 2 shows the filtered signal.

@SIGNAL_DEFINITION {
@SIGNAL_NAME {SignalTotalLift} {
@SENSOR_NAME {SensorTotalAirloads}
@CHANNEL_NUMBER {4}
@SIGNAL_CONDITIONING_NAME {Filter}
}
}
Figure 1. Output created by signal SignalTotalLift.                        Figure 2. Output created by the lowpass filter ButterWorth.