中文摘要：

曲柄群驱动机构是一种特殊的传动机构，根据经典机构学的理论，它是一个超静定机构，文中将它视为一种特殊的并联机构，运用基于螺旋理论的自由度分析方法，对存在P个曲柄的该机构的自由度进行了分析，从约束螺旋的角度深入分析了其被约束的自由度，结果表明其自由度为1，破解了它的超静定问题，为该机构的应用提供了理论依据。

英文摘要：

Crank-group driving mechanism is a special kind of transmission mechanism. According to the classical theory of mechanism, it is a statically indeterminate structure. In this article, the crank-group driving mechanism has been treated as a kind of special parallel mechanism. By using the method of DOF analysis based on screw theory, the DOF for the mechanism of p cranks, has been analyzed. From the perspective of constraint screw, the constrained DOFs have been deeply analyzed. The results show that the DOF is 1. It has cracked its statically indeterminate problem, and provides the credible theoretical basis for the application of the such crank-group mechanism.