Continuously variable transmission design for optimum vehicle performance by analytical target cascading

The applicability of analytical target cascading (ATC) to the design of a continuously variable transmission (CVT) for optimum vehicle performance is studied. ATC is a powerful methodology for the optimisation of complex multilevel systems based on appropriate decomposition and coordination. Several time-dependent mathematical models of a mid-size truck's longitudinal dynamics, powertrain, and power-split CVT were developed and used to analyse the vehicle performance. A detailed geometric model of the CVT primary and secondary pulleys was also developed. These models were implemented in a three-level ATC formulation. In this paper, the decomposition and coordination procedure in the context of ATC is described. The development of system models and their level of detail are discussed with attention focused on tradeoffs between model complexity and computer execution speed. Practical aspects of the iterative process, the multi-criteria optimisation problems, and the selection of arbitrary parameters inherent to ATC are highlighted to offer insight to the practicing engineer. Numerical results of the study illustrate the applicability of ATC to simulation-based design of complex systems.