Abstract: Overconstraint determination is the key and bottleneck of mobility calculation. Starting from its engendered nature, the linear dependence of constraint, a novel approach to overconstraint determination combined with linkgroup parameter matrix is presented to make it easier and faster based on a new mobility theory. To ascertain displacement parameters when the angle of parallel R link group (linkgroup including revolute joints with parallel rotation axis) is not zero, the validity of its vertical component is proposed which only takes parallel constraints of screw linear dependence into account in the midst of varied geometric spaces. The number and types of overconstraint are analyzed in three different situations which derive from its generation. Meanwhile the principles of common constraint and parallel-redundant-constraint determination are concluded. A typical mechanism is taken as an instance and elicited the number and characters of its overconstraint applying the above approach to further verify the rationality and applicability of the proposed approach and principles.

Key words: mobility;overconstraint;parallel-redundant-constraint;displacement parameters of linkgroup