Multibody Dynamics Simulation




Concurrent Dynamics creates high fidelity Multibody Dynamics Simulation programs to assess dynamics and control performances of mechanisms and robotics. They expedite:

  • Concept Feasibility Evaluation

  • Control System Design and Testing

  • Hardware-in-the-Loop Simulation

  • System Failure Analysis, etc..

Fig. 1.   NASA-JPL-Robosimian-robot (courtesy: NASA)


Fig. 2   A 6 link robot arm

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 simx3r.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 mechanisms. Three packages are shown below and more on the space vehicle 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 and dynamics input/output/plot data list. It also shows how to build a nominal control system for the mechanism 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 mechanism/robotics 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.

Arm6x : The model is a ground fixed 6 joint robotic arm with a nominal position control system. The package has examples on how to move the arm from one configuration to another. manual 

OneCylinderEngine: Combustion force profile and crank/piston friction forces determine engine performance. The simulaitions run under two-stroke and four-stroke modes. manual 

Inv_Pendulum : The model is a cart carrying an inverted pendulm. The package has examples showing how the pendulum is held upright while moving the cart to a commanded position. manual 


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  3. Review of multibody dynamics software ( )
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Last modified: April 19, 2014