Strong coupling core

Library for solving a system of strong coupled physical subsystems. Aimed to use in co-simulation, where each slave has mechanical connector points.

The library has support for a number of constraints, see subclasses of sc::Constraint. These can be used to mechanically constrain the connectors to each other.

Links

• Documentation
• Source code & downloads at Github

Usage

The code is typically used like so:

1. Create slaves (sc::Slave instances). These correspond to subsystems in your co-simulation.
2. Create connectors (sc::Connector instances) and add them to the slaves. The connectors are points on which you can connect to other subsystem connectors.
3. Constrain two connectors by creating instances of sc::Constraint.
4. Add slaves, connectors, constraints to the solver (sc::Solver).
5. For each time step in your stepping loop:
   1. Set position, quaternion, velocity and angular velocity of the connectors.
   2. Set future velocity and angular velocity of the connectors (you get this by stepping your system one time step forward).
   3. Set the jacobian for each equation in the system (each sc::Constraint contains at least one sc::Equation). The Jacobian can be imagined as the connector inertia in the constraint directions.
   4. Solve the system (sc::Solver::solve()).
   5. Get resulting constraint force and torque from the connectors. Apply these forces to your co-simulation slaves and then do a final step.

Sample code can be found in test/rigid.cpp

Install

Ubuntu/Linux

To make an out-of-source build in CMake, make a build directory and make it current:

mkdir build;
cd build;
cmake ..;

You need UMFPACK to continue. When running cmake, pass the locations of its include and library paths using -D flags:

cmake .. -DUMFPACK_INCLUDE_DIR=<path> -DUMFPACK_LIBRARY_DIR=<path>

In Ubuntu, UMFPACK is included in the suitesparse package.

Install suitesparse using the following command.

sudo apt-get install suitesparse

And then try running cmake like this:

cmake .. -DUMFPACK_INCLUDE_DIR=/usr/include/suitesparse -DUMFPACK_LIBRARY_DIR=/usr/lib

Finally, run make to compile the code.

make
make install    # optional

OSX

Install SuiteSparse via MacPorts

port install SuiteSparse;

CMakeLists.txt should add /opt/local/include and /opt/local/lib to the paths for you. Run:

mkdir build;
cd build;
cmake .. && make;

Windows

TODO

Documentation

You need Doxygen to generate the documentation. Build the documentation by doing this:

doxygen Doxyfile;

The HTML files will end up in docs/.

Project info

Funded in part by VINNOVA through project Simovate (dnr 2012-01235) and Umeå University, Umeå, Sweden.

Change log

0.1.0

• Started change log