An object-oriented dynamics simulator
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An Object-Oriented Dynamics Simulator (OODS) has been developed by incorporating dynamics theory and numerical methods into the concepts of object-oriented programming (OOP). (X)DS is a response to the need for easily readable, reusable, and extensible general purpose multibody simulation programs. In the development of the dynamics theory, emphasis is placed on the automatic formulation of system equations and their numerical solutions. The system equations consist of the equations of motion, generalized momentum definitions, constraint equations, and generalized force definitions. These equations are highly nonlinear and loosely coupled differential-algebraic equations. The Newton-Raphson method and a stiffly-stable integration method are combined to build a corrector method. Two standard predictor methods are adopted to complete the solution scheme of the system equations. In the development of the new program, the above simulation algorithms are organized using objects and classes to take advantage of the power of OOP. The new program has been written in Smalltalk-80 which is one of the pure OOP languages. It has been shown that the new program is easy to understand, debug, and extend. Test runs for several types of one- and two-body systems have been successfully completed using OODS. The test results reveal that (X)DS is reliable in its formulation of system equations and their numerical solutions. It has been also concluded that (X)DS is applicable to larger systems because the simulation algorithms and programming of OODS have been designed in general terms. Finally, some recommendations are made for potential improvement of (30DS. Specific applications in mechanical engineering practice and education are encouraging.