Template Class LowPassFilter

Inheritance Relationships

Base Type

  • public filters::FilterBase< T >

Class Documentation

template<typename T>
class LowPassFilter : public filters::FilterBase<T>

A Low-pass filter class.

This class implements a low-pass filter for various data types based on an Infinite Impulse Response Filter.

In particular, this class implements a simplified version of an IIR filter equation :

\(y(n) = b x(n-1) + a y(n-1)\)

where:

  • \( x(n)\) is the input signal

  • \( y(n)\) is the output signal (filtered)

  • \( b \) is the feedforward filter coefficient

  • \( a \) is the feedback filter coefficient

and the Low-Pass coefficient equation:

  • \( a = e^{\frac{-1}{sf} \frac{2\pi df}{10^{\frac{di}{-10}}}} \)

  • \( b = 1 - a \)

where:

  • \( sf \) is the sampling frequency

  • \( df \) is the damping frequency

  • \( di \) is the damping intensity (amplitude)

Usage

The LowPassFilter class is meant to be instantiated as a filter in a controller but can also be used elsewhere. For manual instantiation, you should first call configure() (in non-realtime) and then call update() at every update step.

Public Functions

bool configure() override

Configure the LowPassFilter (access and process params).

bool update(const T &data_in, T &data_out) override

Applies one iteration of the IIR filter.

Parameters:

  • data_in – input to the filter

  • data_out – filtered output

Returns:

false if filter is not configured, true otherwise

inline bool update(const geometry_msgs::msg::WrenchStamped &data_in, geometry_msgs::msg::WrenchStamped &data_out)
inline bool update(const std::vector<double> &data_in, std::vector<double> &data_out)