Siconos

A software package for the modeling and simulation of nonsmooth dynamical systems in C++ and in Python.

Siconos is an open-source scientific software primarily targeted at modeling and simulating nonsmooth dynamical systems:

• Mechanical systems (rigid or solid) with unilateral contact and Coulomb friction and impact (Nonsmooth mechanics, contact dynamics, multibody systems dynamics or granular materials).
• Switched Electrical Circuit such as electrical circuits with ideal and piecewise linear components: power converter, rectifier, Phase-Locked Loop (PLL) or Analog-to-Digital converter.
• Sliding mode control systems.
• Biology Gene regulatory networks.

Other applications are found in Systems and Control (hybrid systems, differential inclusions, optimal control with state constraints), Optimization (Complementarity systems and Variational inequalities), Fluid Mechanics, Computer Graphics, ...

Read more about Siconos at the Siconos homepage

Usage

Through your web browser

Perfect to understand and test the software or run lite simulations, demos, teaching ...

Prerequisite: a web browser and a network connection.

Pros: no installation prerequisites, nothing to do

Cons: limited resources. No long/important simulations.

Just click there

Jupyter Lab environment with siconos ready to use and a set of end-user examples:

Prerequisite: Docker installed and usable on your computer.

To use last Siconos release, run the command line bash docker run --rm -p 8888:8888 -ti gricad-registry.univ-grenoble-alpes.fr/nonsmooth/siconos-tutorials/siconoslab-master:latest You will get something like ... To access the server, open this file in a browser: ... http://127.0.0.1:8888/lab?token=b8a131ed7aed720c8fe1d7fae034cd2b669dcf686126c598 Copy this last line into your browser, and there you will be able to start a terminal or a notebook session.

You can also start a simple terminal to use Siconos through the command line with

bash docker run --rm --entrypoint /bin/bash -ti gricad-registry.univ-grenoble-alpes.fr/nonsmooth/siconos-tutorials/siconoslab-master:latest

From source

Assuming you have cloned the project into , to build and install the libraries and the python interface ::

• Create a user options file. Some templates are provided in /config_samples.
• Run

cmake -S <path-to-siconos-sources> -B build-siconos -DUSER_OPTIONS_FILE=<your-options-file> cmake --build build-siconos -j 4 # or the number of cores available on your computer. ctest --test-dir build-siconos # run tests, optional cmake --install build-siconos

More details in Siconos download and install guide.

Main components

Each component can be used either from a low-level language like C/C++ or from Python.

siconos/numerics (C)

Collection of low-level algorithms for solving optimization problems arising in the simulation of nonsmooth dynamical systems:

• Complementarity problems (LCP, MLCP, NCP)
• Friction-contact problems (2D or 3D)
• Second-order cone programming (SOCP)
• Primal or Dual Relay problems
• Finite dimensional Variational Inequality (AVI and VI)

siconos/kernel (C++)

Library for the modeling and simulation of nonsmooth dynamical systems.

• Dynamical systems formalism: first order systems, Lagrangian and Newton-Euler formulations
• Numerical integration techniques: Event-detecting (event-driven) and Event-Capturing (time-stepping) schemes
• Nonsmooth laws: complementarity, Relay, normal cone inclusion, Friction Contact, Newton impact, multiple impact law.

siconos/mechanics (C++)

Component for the simulation of mechanical systems in interaction with their environment: * Contact detection procedure between simple primitives (homemade) and meshes bullet3 * Contact detection between Brep representation based on oce. Open CASCADE Community Edition and on pythonOCC 3D CAD/CAM package for python

siconos/control (C++)

Library to add a controller to a simulation. For now almost all the implemented control schemes are based on sliding modes with an implicit discretization.

siconos/io (C++)

This component can be used to * serialize almost any simulation using boost::serialization * generate mechanical examples from HDF5 and to write HDF5 in view of visualization through vtk

License

Siconos is currently distributed under Apache Licenses (v2).

The archetypal example: "The bouncing ball"

```python from siconos.kernel import LagrangianLinearTIDS, NewtonImpactNSL,\ LagrangianLinearTIR, Interaction, NonSmoothDynamicalSystem, MoreauJeanOSI,\ TimeDiscretisation, LCP, TimeStepping from numpy import eye, empty

t0 = 0 # start time T = 10 # end time h = 0.005 # time step r = 0.1 # ball radius g = 9.81 # gravity m = 1 # ball mass e = 0.9 # restitution coeficient theta = 0.5 # theta scheme

the dynamical system

x = [1, 0, 0] # initial position v = [0, 0, 0] # initial velocity mass = eye(3) # mass matrix mass[2, 2] = 2. / 5 * r * r ball = LagrangianLinearTIDS(x, v, mass) weight = [-m * g, 0, 0] ball.setFExtPtr(weight) #set external forces

Interaction ball-floor

H = [[1, 0, 0]] nslaw = NewtonImpactNSL(e) relation = LagrangianLinearTIR(H) inter = Interaction(nslaw, relation)

Model

bouncingBall = NonSmoothDynamicalSystem(t0, T)

add the dynamical system to the non smooth dynamical system

bouncingBall.insertDynamicalSystem(ball)

link the interaction and the dynamical system

bouncingBall.link(inter, ball)

Simulation

(1) OneStepIntegrators

OSI = MoreauJeanOSI(theta)

(2) Time discretisation

t = TimeDiscretisation(t0, h)

(3) one step non smooth problem

osnspb = LCP()

(4) Simulation setup with (1) (2) (3)

s = TimeStepping(bouncingBall, t, OSI, osnspb)

end of model definition

computation

N = (T - t0) / h # the number of time steps

time loop

while s.hasNextEvent(): s.computeOneStep() s.nextStep()