Expand description
§signal-filters Rust Crate
This crate contains a collection of filters and utilities for digital signal processing.
This crate is no_std, no alloc, no panic, no unwrap, no expect, and the Minimum Supported Rust Version (MSRV) is Rust 1.89.
§Overview
This crate contains the following filters:
Pt1Filter, Pt2Filter, and Pt3Filter : basic first, second, and third order low-pass filters.
BiquadFilter: second order filter that can be used as a low-pass, high-pass, or notch filter.
MedianFilter3 and MedianFilter5: median filters for spike rejection.
SlewRateLimiter: filter that limits the rate of change of a signal.
MovingAverageFilter : simple moving average filter.
The filters have aliases for f32 and f64 versions:
f32 | f64 |
|---|---|
Pt1Filterf32 | Pt1Filterf64 |
Pt2Filterf32 | Pt2Filterf64 |
Pt3Filterf32 | Pt3Filterf64 |
BiquadFilterf32 | BiquadFilterf64 |
MedianFilter3f32 | MedianFilter3f64 |
MedianFilter5f32 | MedianFilter5f64 |
SlewRateLimiterf32 | SlewRateLimiterf64 |
MovingAverageFilterf32 | MovingAverageFilterf64 |
Additionally the all the filters except the Median Filters and Slew Rate Limiters have aliases for their vectorized forms for both f32 and f64 vectors.
So for Pt1Filter we have:
vector f32 | vector f64 |
|---|---|
Pt1FilterVector2f32 | Pt1FilterVector2f64 |
Pt1FilterVector3f32 | Pt1FilterVector3f64 |
Pt1FilterVector4f32 | Pt1FilterVector4f64 |
and similarly for the other filters.
§Rolling and Circular buffers
This crate also has basic circular and rolling buffers:
CircularBuffer<T, const N: usize> and RollingBuffer<T, const N: usize>.
A rolling buffer is similar to a circular buffer, except, once full, old items fall off the front when new items are added.
§Motivation
These filters have been developed for use in stabilized vehicles (self balancing robots and aircraft)and have been used to:
- Filter gyro and accelerometer output for use in the Attitude and Heading Reference System (AHRS).
- Filter motor encoder values for use in the motor controller.
- Filter derivative terms in a PID controller.
- Filter motor power input values to smooth the motor speed.
§Examples
use signal_filters::Pt1Filterf32;
use signal_filters::Pt1FilterVector3f32;
use signal_filters::BiquadFilterf32;
use signal_filters::BiquadFilterVector3f32;
use signal_filters::SignalFilter;
use vqm::Vector3f32;
//
// Pt1 low pass filter.
//
let mut filter = Pt1Filterf32::new();
let sample_interval_s: f32 = 0.001; // 1 kHz sampling rate
filter.set_cutoff_frequency(100.0, sample_interval_s);
let input: f32 = 2.7;
let output = filter.update(input);
//
// Pt1 low pass filter with vector input.
//
let mut filter = Pt1FilterVector3f32::new();
filter.set_cutoff_frequency(80.0, sample_interval_s);
let gyro = Vector3f32 { x: 0.2, y: 0.5, z: 1.5 };
let output = filter.update(gyro);
//
// Biquad filter used as low-pass filter.
//
let sample_interval_s: f32 = 0.001; // 1 kHz sampling rate
let q_factor: f32 = 2.0;
let cutoff_frequency_hz: f32 = 80.0;
let mut notch_filter = BiquadFilterf32::new().with_q(q_factor).with_sample_interval(sample_interval_s);
notch_filter.set_low_pass_frequency_assuming_q(cutoff_frequency_hz);
let input: f32 = 0.8;
let output = notch_filter.update(input);
//
// Biquad filter used as notch filter.
//
let notch_frequency_hz: f32 = 50.0; // 50 Hz power line hum filter
let q_factor: f32 = 10.0; // Narrow notch width
let mut notch_filter = BiquadFilterf32::new().with_q(q_factor).with_sample_interval(sample_interval_s);
notch_filter.set_notch_frequency_assuming_q(notch_frequency_hz);
let input: f32 = 0.8;
let output = notch_filter.update(input);
//
// Biquad notch filter with vector input.
//
let mut notch_filter = BiquadFilterVector3f32::new().with_q(q_factor).with_sample_interval(sample_interval_s);
notch_filter.set_notch_frequency_assuming_q(notch_frequency_hz);
let gyro = Vector3f32 { x: 0.8, y: 2.1, z: -0.2 };
let output = notch_filter.update(gyro);§Original implementation
I originally implemented this crate as a C++ library: Library-Filter.
§License
Licensed under either of:
- Apache License, Version 2.0, see: LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0
- MIT license, see: LICENSE-MIT or http://opensource.org/licenses/MIT
at your option.
Structs§
- Biquad
Filter - Second-order biquad IIR filter.
- Circular
Buffer CircularBuffer<T, const N: usize>.Nitems of typeT.- Median
Filter3 - Non-linear median-of-3 filter for spike rejection.
Maintains a window of the last three samples and returns the median value. - Median
Filter5 - Non-linear median-of-5 filter for spike rejection.
Maintains a window of the last three samples and returns the median value. - Moving
Average Filter - Simple moving average filter.
- Pt1Filter
- Discrete-time, first-order low-pass filter (Proportional Time element).
- Pt2Filter
- Discrete-time, second-order low-pass filter (Proportional Time element).
This is equivalent to two cascaded PT1 filters with the same time constant. - Pt3Filter
- Discrete-time, third-order low-pass filter (Proportional Time element).
This is equivalent to three cascaded PT1 filters. It provides a very steep 60dB/decade roll-off. - Rolling
Buffer RollingBuffer<T, const N: usize>.Nitems of typeT.
Once full, old items fall off the front when new items are pushed on the back.- Slew
Rate Limiter - Limits the maximum rate of change (dV/dt) of a signal.
It allows for different rates depending on whether the signal is increasing (rising) or decreasing (falling).
Traits§
- Limit
Slew - Adds
value.limit_slew_using(&mut slew_rate_limiter)method call toSlewRateLimiter. - Signal
Filter - Filter Definition trait.
filter.reset()filter.update(value) - Update
Filter - Adds
value.filter_using(&mut filter)method call syntax toSignalFilter.
Type Aliases§
- Biquad
Filter Vector2f32 BiquadFilterforVector2f32- Biquad
Filter Vector2f64 BiquadFilterforVector2f64- Biquad
Filter Vector3f32 BiquadFilterforVector3f32- Biquad
Filter Vector3f64 BiquadFilterforVector3f64- Biquad
Filter Vector4f32 BiquadFilterforVector4f32- Biquad
Filter Vector4f64 BiquadFilterforVector4f64- Biquad
Filterf32 BiquadFilterforf32- Biquad
Filterf64 BiquadFilterforf64- Median
Filter3f32 Median3Filterforf32- Median
Filter3f64 Median3Filterforf64- Median
Filter5f32 Median5Filterforf32- Median
Filter5f64 Median5Filterforf64- Moving
Average Filter Vector2f32 MovingAverageFilterforVector2f32- Moving
Average Filter Vector2f64 MovingAverageFilterforVector2f64- Moving
Average Filter Vector3f32 MovingAverageFilterforVector3f32- Moving
Average Filter Vector3f64 MovingAverageFilterforVector3f64- Moving
Average Filter Vector4f32 MovingAverageFilterforVector4f32- Moving
Average Filter Vector4f64 MovingAverageFilterforVector4f64- Moving
Average Filterf32 MovingAverageFilterforf32- Moving
Average Filterf64 MovingAverageFilterforf64- Pt1Filter
Vector2 Vector2f32 Pt1FilterforVector2Vector2f32- Pt1Filter
Vector2 Vector2f64 Pt1FilterforVector2Vector2f64- Pt1Filter
Vector2f32 Pt1FilterforVector2f32- Pt1Filter
Vector2f64 Pt1FilterforVector2f64- Pt1Filter
Vector3 Vector3f32 Pt1FilterforVector3Vector3f32- Pt1Filter
Vector3 Vector3f64 Pt1FilterforVector3Vector3f64- Pt1Filter
Vector3f32 Pt1FilterforVector3f32- Pt1Filter
Vector3f64 Pt1FilterforVector3f64- Pt1Filter
Vector4 Vector4f32 Pt1FilterforVector4Vector4f32- Pt1Filter
Vector4 Vector4f64 Pt1FilterforVector4Vector4f64- Pt1Filter
Vector4f32 Pt1FilterforVector4f32- Pt1Filter
Vector4f64 Pt1FilterforVector4f64- Pt1Filterf32
Pt1Filterforf32- Pt1Filterf64
Pt1Filterforf64- Pt2Filter
Vector2 Vector2f32 Pt2FilterforVector2Vector2f32- Pt2Filter
Vector2 Vector2f64 Pt2FilterforVector2Vector2f64- Pt2Filter
Vector2f32 Pt2FilterforVector2f32- Pt2Filter
Vector2f64 Pt2FilterforVector2f64- Pt2Filter
Vector3 Vector3f32 Pt2FilterforVector3Vector3f32- Pt2Filter
Vector3 Vector3f64 Pt2FilterforVector3Vector3f64- Pt2Filter
Vector3f32 Pt2FilterforVector3f32- Pt2Filter
Vector3f64 Pt2FilterforVector3f64- Pt2Filter
Vector4 Vector4f32 Pt2FilterforVector4Vector4f32- Pt2Filter
Vector4 Vector4f64 Pt2FilterforVector4Vector4f64- Pt2Filter
Vector4f32 Pt2FilterforVector4f32- Pt2Filter
Vector4f64 Pt2FilterforVector4f64- Pt2Filterf32
Pt2Filterforf32- Pt2Filterf64
Pt2Filterforf64- Pt3Filter
Vector2 Vector2f32 Pt3FilterforVector2Vector2f32- Pt3Filter
Vector2 Vector2f64 Pt3FilterforVector2Vector2f64- Pt3Filter
Vector2f32 Pt3FilterforVector2f32- Pt3Filter
Vector2f64 Pt3FilterforVector2f64- Pt3Filter
Vector3 Vector3f32 Pt3FilterforVector3Vector3f32- Pt3Filter
Vector3 Vector3f64 Pt3FilterforVector3Vector3f64- Pt3Filter
Vector3f32 Pt3FilterforVector3f32- Pt3Filter
Vector3f64 Pt3FilterforVector3f64- Pt3Filter
Vector4 Vector4f32 Pt3FilterforVector4Vector4f32- Pt3Filter
Vector4 Vector4f64 Pt3FilterforVector4Vector4f64- Pt3Filter
Vector4f32 Pt3FilterforVector4f32- Pt3Filter
Vector4f64 Pt3FilterforVector4f64- Pt3Filterf32
Pt3Filterforf32- Pt3Filterf64
Pt3Filterforf64- Slew
Rate Limiterf32 SlewRateLimiterforf32- Slew
Rate Limiterf64 SlewRateLimiterforf64