This library contains functions to create excitation waveforms for exciting a system and measuring its response. This library is compatible with Arduino and with CMake build systems.
Use the Arduino Library Manager to install this library or clone to your Arduino/libraries folder. In addition, this library requires the Bolder Flight Systems Units library to be installed. This library is added as:
#include "excitation.h"An example Arduino executable is located at examples/arduino/excitation_example/excitation_example.ino. Teensy 3.x, 4.x, and LC devices are used for testing under Arduino and this library should be compatible with other devices.
CMake is used to build this library, which is exported as a library target called excitation. The header is added as:
#include "excitation.h"The library can be also be compiled stand-alone using the CMake idiom of creating a build directory and then, from within that directory issuing:
cmake ..
make
This will build the library, an example executable called excitation_example. The example executable source file is located at examples/cmake/excitation_example.cc.
This library is within the namespace bfs.
This class implements a pulse.
Pulse(const float dur_s, const float amp) Creates a pulse, specifying the pulse duration (seconds) and amplitude.
/* Creates a 10 second pulse, amplitude of 2 */
bfs::Pulse pulse(10.0f, 2.0f);float Run(const float time_s) Computes the excitation output given the time since the start of the excitation.
/* Get the excitation output at 3 seconds */
float y = pulse.Run(3.0f);This class implements a 1-cos pulse.
Pulse1Cos(const float dur_s, const float pause_s, const float amp) Creates a pulse, specifying the duration of the 1-cos (seconds), pause time at peak amplitude (seconds), and amplitude. The total duration of the pulse is the 1-cos duration plus the pause time.
/* Creates a 10 second 1-cos pulse, a 2 second pause, amplitude of 2 */
bfs::Pulse1Cos pulse(10.0f, 2.0f, 2.0f);float Run(const float time_s) Computes the excitation output given the time since the start of the excitation.
/* Get the excitation output at 3 seconds */
float y = pulse.Run(3.0f);This class implements a doublet.
Doublet(const float dur_s, const float amp) Creates a doublet give the duration of one of the steps (seconds) and amplitude. The total duration of the excitation is 2 times the step duration.
/* Creates a 5 second doublet, amplitude of 2 */
bfs::Doublet doublet(5.0f, 2.0f);float Run(const float time_s) Computes the excitation output given the time since the start of the excitation.
/* Get the excitation output at 3 seconds */
float y = doublet.Run(3.0f);This class implements a 1-2-1 doublet.
Doublet121(const float dur_s, const float amp) Creates a 1-2-1 doublet give the duration of one of the steps (seconds) and amplitude. The total duration of the excitation is 4 times the step duration.
/* Creates a 5 second doublet, amplitude of 2 */
bfs::Doublet121 doublet(5.0f, 2.0f);float Run(const float time_s) Computes the excitation output given the time since the start of the excitation.
/* Get the excitation output at 3 seconds */
float y = doublet.Run(3.0f);This class implements a 3-2-1-1 doublet.
Doublet3211(const float dur_s, const float amp) Creates a 3-2-1-1 doublet give the duration of one of the steps (seconds) and amplitude. The total duration of the excitation is 7 times the step duration.
/* Creates a 5 second doublet, amplitude of 2 */
bfs::Doublet3211 doublet(5.0f, 2.0f);float Run(const float time_s) Computes the excitation output given the time since the start of the excitation.
/* Get the excitation output at 3 seconds */
float y = doublet.Run(3.0f);This class implements a linear chirp.
LinearChirp(const float dur_s, const float amp_start, const float amp_stop, const float freq_start, const float freq_stop) Creates a linear chirp given the chirp duration (seconds), starting and stopping amplitude, and starting and stoping frequency (rad/s).
/* Creates a 5 second chirp, amplitude from 2 to 0.5 and frequency from 1 rad/s to 6 rad/s */
bfs::LinearChirp chirp(5.0f, 2.0f, 0.5f, 1.0f, 6.0f);float Run(const float time_s) Computes the excitation output given the time since the start of the excitation.
/* Get the excitation output at 3 seconds */
float y = chirp.Run(3.0f);This class implements a log chirp.
LogChirp(const float dur_s, const float amp_start, const float amp_stop, const float freq_start, const float freq_stop) Creates a log chirp given the chirp duration (seconds), starting and stopping amplitude, and starting and stoping frequency (rad/s).
/* Creates a 5 second chirp, amplitude from 2 to 0.5 and frequency from 1 rad/s to 6 rad/s */
bfs::LogChirp chirp(5.0f, 2.0f, 0.5f, 1.0f, 6.0f);float Run(const float time_s) Computes the excitation output given the time since the start of the excitation.
/* Get the excitation output at 3 seconds */
float y = chirp.Run(3.0f);This class implements a multisine.
MultiSine(const float dur_s) Creates a multisine excitation given the duration.
/* 10 second multisine */
bfs::MultiSine multisine(10.0f);float Run(const float time_s, float * const amp, float * const freq, float * const phase, const size_t len) Computes the excitation output given the time since the start of the excitation, pointers to arrays and of the amplitude, frequency (rad/s), and phase (rad) and the length of the arrays. Note that the arrays must all be the same length.
float freq[5] = {0.6283185307179586, 4.360530603182633, 8.092742675647308, 11.824954748111981, 15.557166820576658};
float phase[5] = {6.174200357528524, 5.448037839217776, 3.8454607850193847, 1.6650584957876886, 3.9242402680243402};
float amp[5] = {0.19810717087274396, 0.19810717087274396, 0.19810717087274396, 0.19810717087274396, 0.19810717087274396};
/* Get the excitation output at 3 seconds */
float y = multisine.Run(3.0f, amp, freq, phase, 5);This class implements a user-defined excitation.
Sampled(const float dur_s, const float dt_s) Creates a user-defined excitation specifying the excitation duration (seconds) and sample rate of the provided data (seconds).
/* 10 second duration excitation defined by the array samp, which is spaced at 1 second intervals */
bfs::Sampled<10> sampled(10, 1);float Run(const float time_s, float * const data, const size_t len) Computes the excitation output given the time since the start of the excitation and an array of output values. Note that this class simply computes the appropriate index in the array of output values, based on the input time and sample rate, and outputs that value. No interpolation or extrapolation is used.
/* Get the excitation output at 3 seconds */
float samp[10] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
float y = sampled.Run(3.0f, samp, 10);