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Abstract:One
of the popular artefacts available in people's collections is introduced
as a highly expandable and collapsible structure. Starting by removing
the kinematic chains which do not influence the mechanism mobility, the
magic ball mechanism is hypothetically disintegrated into several
kinematic chains, and subsequently two platform-like kinematic
sub-chains which have three legs and four legs respectively. The theory
of a screw system and its reciprocal system is used lo examine the
virtual constraints and common constraints in each of the kinematic
sub-chains and to further examine the mobility of those sub-chains,
Based on a systematic analysis in mechanism decomposition and in the
analysis of virtual constraints, a theoretical basis for the mobility
analysis of the mechanism is produced and then its characteristics of
mobility are obtained. The result is verified by using the
loop-connectivity approach.
Key words: Mobility
Screw system Metamorphic mechanism Kinematic chain Platform
CLC No: TH112
国家自然科学基金资助项目(50075009). Received 20010726, received in revised form
20011105 |