Multibody Dynamics Simulation




Concurrent Dynamics delivers high fidelity Multibody Dynamics Simulation programs to assess dynamics and control performances of mechanisms and mobile vehicles. They expedite:

  • Concept Feasibility Evaluation

  • Control System Design and Testing

  • Hardware-in-the-Loop Simulation

  • System Failure Analysis, etc..

pictures credits: NASA

Our simulations run on PC's with Window XP and Window 7/8 OS equipped with Matlab/Simulink. We build streamlined mdl files by encapsulating all dynamics computations and i/o processes in one functional block, namely xsv01.dll. This dynamics engine has an easy to work with i/o interface to connect it with the user supplied control system. In short, our simulation programs:

  • Autogenerate minimal state multibody dynamics equations for each vehicle or mechanism being simulated 

  • Solve the dynamics equations efficiently (by order(N) method) so you can concentrate on the design and testing of control systems

  • Make it easy to modify model parameters and control systems to achieve simulation goals quickly

We are putting together ready-to-use simulation packages for a variety of vehicles and for different operations. Four packages are shown below and more are on the robotics page and in the works. Models in these packages are as accurate as those built using major commercial codes. They run significantly faster than programs built by the same. Moreover, they can be modified easily to fit user's immediate needs. In all cases, one can run the supplied simulations the same day they are installed. 

Manual in each package explains how to define a model_file using the tool, buildx.exe. This definition encompass  mass property of bodies and wheels, force objects, gravity model selection and dynamics input/output/plot data list. It also shows how to build a nominal control system for the vehicle represented by the model_file. The result is a simulation program in the form of an mdl file that runs in Simulink. Examples are presented for illustration.

Our packages are excellent tools for engineers engaged in control system design and testing. They are geared for scientific and realtime simulations. Their model fidelity and ease-of-use eliminate, for practical purposes, the cost of formulating, programming, GUI design, testing and validating simulation programs. They are most valuable to projects that encounter frequent model/control system changes or need major model rebuild. These tools are also ideal for university courses that  teach multibody dynamics and control systems, robotics or mechatronics. Students would use them to test and verify the dynamics and control algorithms generated to solve problems at hand. We welcome suggestions on the kind of vehicle simulation packages that you would like us build.

We invite you to get a free Project license for a package below by sending your request to click 'manual' below to see how the model is created using the model editor, buildx.exe, and how the mdl file is designed for that application and more.

SV1sim: The model is a vehicle with 4 wheels and 8 jets with a nominal rwa ACS and a jet ACS. Package has examples on how to design LVLH control with reaction wheels and jets. manual 

Arraysim: This is an expanded version of SV1sim vehicle. It retains the same ACS, but now has two arrays each with a yoke and 3 panels. Examples show how the arrays are deployed in a coordinated manner under the action of 'gear' and 'lock' constraints. manual 

Tethersim: This simulation uses SV1sim to deploy a payload with a tether. Tether length and pushoff force are adjustable. Examples show different system response between a small pld/vehicle mass ratio and a high ratio. Deployment dynamics depends on other parameters as well. manual 

CMG4sim: This is a vehicle with 4 SGCMG's and 8 jets. It has a nominal CMG ACS and a momemtum management system. The package has examples showing the operation of the vehicle with/without momentum mgmt. Users can design different CMG mounting configurations and test the correspoinding cmg control system for ACS. LVLH control is shown, sun-nadir ACS can be done also. manual 


See robotics/mechanisms page

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Interesting Websites:

  1. Multibody System Dynamics- Research Activities ( )
  2. Space flight news ( )
  3. Review of multibody dynamics software ( )
  4. Aerospace news (
  5. Robotics news (
  6. Robots news 1 (
  7. Robots news 2 (



Copyright Concurrent Dynamics International
Last modified: April 19, 2014