Design, analysis, and experimental validation of a novel seamless automatic transmission for electric vehicle

The transmission system has an important influence on the dynamic performance, endurance mileage, and energy saving in an all-electric vehicle. This article proposes an innovative two-speed seamless dry-friction automatic transmission system to improve the dynamic performance and endurance mileage of an all-electric vehicle with the existing battery technology. The proposed system consists of two-stage epicyclical gear sets without outer ring gears, a dry-friction clutch, and a brake band, realizes a seamless shifting between any two speeds in an electric vehicle. Based on the working principle and dynamic modeling of the proposed seamless dry-friction automatic transmission system, the ratio optimization was carried out to improve the dynamic performance and the power consumption at the same time, and the combination of the weight ratio method and the multi-island genetic algorithm method was introduced to solve the optimization problem. It is shown both theoretically and experimentally that the proposed seamless dry-friction automatic transmission method demonstrates a better dynamic performance and shifting comfort when compared to the automated manual transmission with same transmission ratio