The disadvantage of a small speed range about traditional transmission is overcome by the emergence of controlling differential continuously variable transmission

but it also brings a new problem about a closed loop power while expanding the speed range.Circulating power in the device can not be avoided

under the circumstances

the study of optimal distribution of the closed loop power flow for zero speed regulating device to achieve the principle of minimum power loss of the device and improve the transmission efficiency

thus to achieve the best transmission effect

and a basis for the optimal design of such device is provided.