filter.c File Reference

This is a collection of functions for generating and implementing discrete SISO filters for arbitrary transfer functions. More...

#include <stdio.h>
#include <math.h>
#include <string.h>
#include <stdlib.h>
#include <stdint.h>
#include <rc/math/filter.h>
#include <rc/math/polynomial.h>
#include "algebra_common.h"

Include dependency graph for filter.c:

Functions
rc_filter_t	rc_filter_empty (void)
	Critical function for initializing rc_filter_t structs. More...
int	rc_filter_alloc (rc_filter_t *f, rc_vector_t num, rc_vector_t den, double dt)
	Allocate memory for a discrete-time filter & populates it with the transfer function coefficients provided in vectors num and den. More...
int	rc_filter_alloc_from_arrays (rc_filter_t *f, double dt, double *num, int numlen, double *den, int denlen)
	Like rc_filter_alloc(), but takes arrays for the numerator and denominator coefficients instead of vectors. More...
int	rc_filter_duplicate (rc_filter_t *f, rc_filter_t old)
	duplicates a filter More...
int	rc_filter_free (rc_filter_t *f)
	Frees the memory allocated by a filter's buffers and coefficient vectors. Also resets all filter properties back to 0. More...
double	rc_filter_march (rc_filter_t *f, double new_input)
	March a filter forward one step with new input provided as an argument. More...
int	rc_filter_reset (rc_filter_t *f)
	Resets all previous inputs and outputs to 0. Also resets the step counter & saturation flag. More...
int	rc_filter_print (rc_filter_t f)
	Prints the transfer function and other statistic of a filter to the screen. More...
int	rc_filter_enable_saturation (rc_filter_t *f, double min, double max)
	Enables saturation between bounds min and max. More...
int	rc_filter_get_saturation_flag (rc_filter_t *f)
	Checks if the filter saturated the last time step. More...
int	rc_filter_enable_soft_start (rc_filter_t *f, double seconds)
	Enables soft start functionality where the output bound is gradually opened linearly from 0 to the normal saturation range. More...
double	rc_filter_previous_input (rc_filter_t *f, int steps)
	Returns the input 'steps' back in time. Steps=0 returns most recent input. More...
double	rc_filter_previous_output (rc_filter_t *f, int steps)
	Returns the output 'steps' back in time. Steps = 0 returns most recent output. More...
int	rc_filter_prefill_inputs (rc_filter_t *f, double in)
	Fills all previous inputs to the filter as if they had been equal to 'in'. More...
int	rc_filter_prefill_outputs (rc_filter_t *f, double out)
	Fills all previous outputs of the filter as if they had been equal to 'out'. More...
int	rc_filter_multiply (rc_filter_t f1, rc_filter_t f2, rc_filter_t *f3)
	Creates a new filter 'out' by multiplying f1*f2. More...
int	rc_filter_multiply_three (rc_filter_t f1, rc_filter_t f2, rc_filter_t f3, rc_filter_t *out)
	Creates a new filter 'out' by multiplying f1*f2*f3. More...
int	rc_filter_c2d_tustin (rc_filter_t *f, double dt, rc_vector_t num, rc_vector_t den, double w)
	Creates a discrete time filter with similar dynamics to a provided continuous time transfer function using tustin's approximation with prewarping about a frequency of interest 'w' in radians per second. More...
int	rc_filter_normalize (rc_filter_t *f)
	Normalizes a discrete time filter so that the leading demoninator coefficient is 1. More...
int	rc_filter_first_order_lowpass (rc_filter_t *f, double dt, double time_constant)
	Creates a first order low pass filter. More...
int	rc_filter_first_order_highpass (rc_filter_t *f, double dt, double time_constant)
	Creates a first order high pass filter. More...
int	rc_filter_butterworth_lowpass (rc_filter_t *f, int order, double dt, double wc)
	Creates a Butterworth low pass filter of specified order and cutoff frequency. More...
int	rc_filter_butterworth_highpass (rc_filter_t *f, int order, double dt, double wc)
	Creates a Butterworth high pass filter of specified order and cutoff frequency. More...
int	rc_filter_moving_average (rc_filter_t *f, int samples, double dt)
	Makes a FIR moving average filter that averages over specified number of samples. More...
int	rc_filter_integrator (rc_filter_t *f, double dt)
	Creates a first order integrator. More...
int	rc_filter_double_integrator (rc_filter_t *f, double dt)
	Creates a second order double integrator. More...
int	rc_filter_pid (rc_filter_t *f, double kp, double ki, double kd, double Tf, double dt)
	Creates a discrete-time implementation of a parallel PID controller with high-frequency rolloff using the forward-Euler integration method. More...
int	rc_filter_third_order_complement (rc_filter_t *lp, rc_filter_t *hp, double freq, double damp, double dt)
	Creates a third order symmetric complementary pair of high/low pass filters. More...

Detailed Description

This is a collection of functions for generating and implementing discrete SISO filters for arbitrary transfer functions.

Author

James Strawson

Date

2016