如果在两个自由度的差动轮系中用一个附加的传动把任意两个具有固定回转轴线的构件联结起来便可得到一个自由度的联动行星轮系。这类机构的效率计算仍未解决。其实问题并不复杂。因为只要差动器有一个输入输出端与外介直连,该端的输入或输出使是确定的,其余两个输入输出端功率流向便可知,继而连接两个差 A two degree-of-freedom differential geartrain can be obtained by combining any two members with a fixed axis of rotation with an additional transmission in a differential of two degrees of freedom. The calculation of the efficiency of such agencies remains unresolved. In fact, the problem is not complicated. Because as long as the differential has an input and output terminals directly connected with the external, the end of the input or output is to make sure the other two input and output power flow direction will be known, and then connect the two difference