Optimized Design Of A Dynamically-based Motion Generating Spatial Four-bar Mechanism On Rigid Multibody Systems

The four-bar spatial mechanism is the most basic chain that can be composed of four links andrncan include joints with any combination of rotational and translational freedom used inrnthousands of applications. This thesis will present some of the techniques and introduce solutionrntools that were not needed for planar motion. One of the new techniques known as the Eulerrnparameters will be considered in this work.rnThe thesis includes modeling, optimizing computer-aided dynamic analysis and simulationrnof four-bar spatial mechanism composed of rigid bodies that are used for different applications ofrnspatially moving motion generating mechanisms. The Motions of the rigid bodies are predictedrnby numerically integrating Differential-Algebraic Equations (DAEs) developed from principlesrnof mechanics by the Newton-Euler’s approach.rnThe computer program, MSC.ADAMS2005 will be used to model, solve, simulate, and optimizernthe dynamics of the appraised spatial four-bar mechanism as a lens-polishing mechanism byrnintegrating the differential equations.rnUnlike analytical synthesis, optimization allows direct incorporation of a greater number ofrndesign constraints, thus resulting in solutions that are more practical. In this thesis, an efficientrnalgorithm known as the Generalized Reduced Gradient (GRG) is used to synthesize all kinematicrnlinkages of the spatial mechanism. This approach will allow monitoring and controllingrnobjectives and constraints, which will yield practical solutions to realistic mechanism designrnproblems with lower kinematic pairs.rnIn addition to the above mentioned points, a mobility analysis has been done for the RSSRrnmechanism, which is a one degree of freedom, single loop, and spatial mechanism.rnThus, this thesis specifically discusses a practical example of a lens polishing four-bar spatialrnmechanism that simply substitutes the extremely expensive existing polishing robots. Thisrnmechanism is applicable in polishing lenses of military fire control instruments found in thernEthiopian Defence Forces. Thus, the design presented in this thesis provides a relatively low-costrnsolution for the existing problem as compared to the robots. This can be created with ease ofrnmanufacture in a machine shop quickly and simply. Numerical results obtained in this thesis arerncompared with existing literatures.

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