Modelling of an automated manual transmission system

Vehicles with automated manual transmissions (AMT) for gear shift control offer many advantages in terms of reduction of fuel consumption and improvement of driving comfort and shifting quality. Complexity, nonlinearity and high-order dynamics of the automated driveline, combined with strict requirements for high performance gear shifts, demand the development of driveline models, which include a detailed description of the actuators. These models can be useful for different purposes: (a) during system development, to evaluate the achievable performance and its dependency on system properties; (b) as simulation tools for gear shift control algorithm design. In this paper, physically-based detailed nonlinear models of the electro-hydraulic actuated gearbox and of the dry clutch electro-hydraulic actuator of an automated manual transmission are developed. In order to analyze their behavior and their impact on the drivetrain during gear shifts, actuator models are integrated with a simplified transmission shafts dynamics. A reduced-order model of the gearbox actuator, which is valid when dither signal is imposed to servovalves, is developed with the aim of analyzing its properties and performances.Model parameter identification has been performed mostly by means of theoretical relations and design data. Experimental tests, performed on a commercial car, confirm that the proposed model is able to describe the actuators behavior and the main phenomena characterizing system dynamics during gear shift.