| Spatial parallel mechanism has become a hot research area in domestic and foreignscholars and industrial applications, in particular, is lower-mobility parallel mechanism.DOF of mechanism must be the first determined no matter in the design process of parallelmechanisms or the industrial applications of manufacturing technology.In this paper, based on the screw theory analysis method, this research exploresautomatic calculation about DOF of lower-mobility parallel mechanism, reduces thecalculation time and provides convenience for users of parallel mechanisms. The detailsare as follows:Firstly, based on the screw theory basic knowledge, multiple degrees of freedom(MDOF) pairs can be expressed by a few single degree of freedom (SDOF) pairs.According to spatial distribution characteristics, SDOF pairs can be written as screwexpressions and form different types of branches; to facilitate calculating rank of screwmatrix with programming language, the mathematics transformation model is built aboutplanimetric rectangular coordinates and spatial rectangular coordinate.Basic components and chains models are created by using SolidWorks software.Then based on VB, the secondary development system is created by using the plug-inmacro of SolidWorks; known lower-mobility parallel mechanisms can be built accordingto the rules of constructing parallel mechanisms; under the VB interface, constraintscrews of mechanisms can be calculated in initial position.After position of3D object model changed, by using SolidWorks native intelligentcollection-point functionality, a kinematic screw system of the parallel mechanism can becalculated and provide convenience for other related computing by inputting pointcoordinates of each pair.Finally, the paper shows operating steps of the software system, after calculatingconstraint screws of mechanisms, calculated DOF about a number of the typical lower-mobility parallel mechanism by hand, the results shows that this system can bepracticable. |
