This paper presents a method for complete force analysis, including both statics and dynamics, of overconstrained, statically indeterminate spatial mechanisms. Of primary concern is the development of a method which is realistic and has general applicability. The usual tacit assumption of the vanishing of certain force and torque components in the analysis, such as zero axial forces at joints, is removed. The method combines an analytical technique—using the [3 × 3] screw matrix method—coupled with an experimental method to completely specify the dynamic state of an overconstrained mechanism. The indeterminate force is modeled using a characteristic equation simulated experimentally. The method is illustrated in the case of the UNI-LAT coupling which is a modified Hooke-type joint. Based on the analytical results, some physical insights are interpreted. It was found that overclosure affects mechanism performance and plays an important role in the dynamics of the UNI-LAT coupling. General guidelines on the design of the UNI-LAT coupling are also presented.

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