In order to explore the particularity of terminal constraint form of"parallel+parallel"type lower mobility hybrid mechanisms,taking(3-RPS)+(2-RCR)mechanisms as research object,a method for solving the intersection of screw systems corresponding to terminal constraint issue was proposed.Firstly,the composition principle of terminal constraint/mobility of(3-RPS)+(2-RCR)mechanisms was introduced,and the calculation formula of terminal constraint/mobility was given.Secondly,the number of terminal mobility of the mechanisms was analyzed using line geometry under different geometric configurations.Then,the ruled surface and generatrix equation corresponding to sub-constrained screw systems were established by analytic geometry theory and screw theory,and the intersection analytic model of three-screw system and four-screw system was obtained,and the terminal constraint of the mechanisms was determined.Thirdly,the terminal constraint/mobility properties were discussed under different geometric configurations.Finally,numerical examples of the mechanisms were given to solve the terminal constraint under three different configurations.The re-sults show that terminal constraint of the mechanisms is not a constraint force/couple,but the general form of wrench under the general configuration.The method of solving the intersection of screw sys-tems provides an effective way to solve the terminal constraint problems of this kind of hybrid mecha-nisms.
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