Dynamic Lever: Key to Automotive Transmission and Drivetrain Dynamics

Lever analogy has been developed for more than 30 years. The powerful tool can greatly simplify transmission analysis and has been widely used for transmission powerflow analysis, selection, and control synthesis. In the past two decades, automatic transmissions have undergone a rapid growth with continual increase in the number of speeds and electrification. The increase in the system complexity has presented great challenges to system integrations. Many unpredicted issues have been NVH related and difficult to troubleshoot, partially due to the lack of proper modeling and analysis tool to capture the drivetrain dynamics including transmission components. Although the lever analogy has played important roles in the system design, the current form is not adequate and has never been used for dynamic analysis for the transmission and drivetrain system. In this article, we will introduce the dynamic lever model framework and analysis method to address the dynamic aspect of a transmission and drivetrain system. This analytical model framework allows one, for the first time, to systematically comprehend all possible dynamic structures within a drivetrain system. We will show that the dynamic lever framework can add the desired dynamic analysis capability to the existing lever analogy-based methods and will be a powerful tool proven to be effective in transmission analysis, control design, and troubleshooting.