COMPAMM — A Simple and Efficient Code for Kinematic and Dynamic Numerical Simulation of 3-D Multibody Systems with Realistic Graphics

The theoretical foundations of a 3-D multibody program called COMPAMM (COM-Puter Analysis of Machines and Mechanisms) are presented. Instead of using Euler angles or Euler parameters in order to define the spatial orientation of a rigid body, COMPAMM uses the cartesian coordinates of two or more points and the cartesian components of one or more unit vectors rigidly attached to the body. With this coordinates the constraint equations are quadratic and then the jacobian matrix is a linear function of them, needing for its evaluation far less arithmetic operations than with other methods. In addition to this, the mass matrix in the inertial reference frame is constant and Coriolis or centrifugal forces do not appear in the formulation. COMPAMM has also very advanced interactive and graphical capabilities that are very briefly described in this paper. Finally some examples are presented.