Numerical Integration Software for Hybrid Systems
Beta-test distribution of MATLAB integration routines for the solution
of ordinary differential equations with state events (ODEs with
discontinuities or switching lines in the state space). Note: These
routines only work under MATLAB; they are invalid for SimuLink.
Note: These routines were tested to work under MATLAB 5.3,
MATLAB 6.1, MATLAB 6.5 (release 13 for unix) and MATLAB 7.4 (release
R2007a for unix); more recently they were tested under matlab_R2015b (mac version)
and still performed all the examples flawlessly.
Simply download the
hybrid_sim.zip file (377kB) to obtain and install the entire
set of files containing the algorithms, documentation and demonstrations
(models and scripts to run them).
Alternatively, the list below outlining these files may be used to acquire
any subset of them.
To use the entire distribution, I recommend that you create a new directory (e.g.,
> mkdir hybrid_sim - sorry, I only "speak" unix),
download hybrid_sim.zip into that location, and add that
directory to your MATLAB search path (i.e., append the full path to the new
directory onto the setenv MATLABPATH statement in your
.cshrc file, e.g.:
setenv MATLABPATH (stuff_already_there):/home1/jtaylor/Simulation/hybrid_sim
I also recommend (request) that you register with me, NOW
(jtaylor@unb.ca), so I can inform
you of updates and bug-fixes. Also, please let me know about any bugs
or defects you might discover (of course, this is highly
unlikely . . . ;-).
The following files are available individually for your information and use:
manual.pdf,
a short tutorial guide on how to use our approach and
software for modeling and simulating ODEs with discontinuous
right-hand sides
relay.m,
relay_seh.m,
run_relay.m,
a simple example of state-event handling (a relay switching a
double integrator to yield closed trajectories in the phase plane; the
mode switches from -1 to 1 and vice versa as a switching curve x1 = 0 is
crossed), and a demonstration macro for running it that compares
our method with the direct use of MATLAB's ODE45 (in its uncompiled or
m-file form)
rdz.m,
rdz_seh.m,
run_rdz.m,
a slightly more complicated model (involving a relay with
deadzone) that illustrates the use
of three mode levels (-1, 0 +1), plus a non-mode-based version of the
same model (rdz.m), and a demonstration macro for running them that
compares the simulation times for the state-event handling routines
with that of the old uncompiled ODE45 algorithm
twin_ball_reset.m,
run_tbr.m,
another slightly more complicated model
that illustrates state resetting as part of state-event handling,
and a macro for running it
stick.m,
stick_seh.m,
run_stick.m,
stick_seh.m represents
a more physical example of state-event handling, involving
an electro-mechanical system with saturation and stiction; the
mode switches from -1 or 1 to 0 (when the motor and load "stick" at zero
velocity) and vice versa (as the motor and load become "unstuck") --
also, stick.m models the same system without state-event handling
(for use with MATLAB's ode45), and run_stick.m
is a demonstration macro for running the models
trap_101.m,
a fixed-step trapezoidal method for state-event handling
ode45_101.m, a variable-step Runge-Kutta-Fehlberg
routine (ode45) extended to handle state events, and ode45m.m, if you
wish to compare these two methods (with and without the use of
modes)
Note: The integration routines trap_101.m and
ode45_101.m contain fragments (good-sized chunks) of
MATLAB's FZERO and ODE45 algorithms, with permission from MathWorks.
The tutorial guide manual.pdf contains a few listings and figures
for the examples that are discussed (to keep the guide relatively short); the models and
macros listed above may be run to obtain a larger variety of illustrative examples.
Note that we have extended this methodology to handle hybrid systems
comprised of a mixture of discrete- and continuous-time components.
The main focus of that effort was precise timing and coordination of
state and time events during simulation. The resulting
software, described in
ifac_wc_hsmns.pdf
(which is included in the zip file), has not
been tested sufficiently for distribution; it will
be made available here eventually . . . especially if there is demand!
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