INTRODUCTION In recent years, new automatic transmission architectures have been introduced in order to meet regulatory and market requirements (such as CO 2 reduction, fuel economy improvement, and enhanced driving experience) [ 1,2]. The pressure on shortening the development cycles in automotive industry requires development of numerical methods and related software tools in support of those processes. For instance, in [3] an automated modeling procedure is developed, which enables search through all designs with different configurations, clutch locations, and operating modes with the aim of improving the hybrid electric powertrain efficiency. From the perspective of system dynamics analyses and control system designs, the development of methods that allow for automated generation of computationally efficient mathematical models is of a particular interest [ 4,5]. In the field of automatic transmissions (ATs), automated modeling would ultimately include generation of a full-order, minimum-realization state-space mathematical model directly from an AT schematic. The work presented in this paper makes a contribution toward fully-automated AT modeling by proposing a method for automated numerical generation of the full-order mathematical model from a bond graph that directly reflects the structure of AT. The proposed method is based on the use of 20-sim [6] and MATLAB software packages. 20-sim supports bond graph modeling and includes certain automated modeling features (e.g. Scripting Toolbox that allows automatic execution of 20-sim commands using MATLAB scripts, including the model export into MATLAB).In addition to automated generation of the full-order AT model, it is of interest to derive a method/tool for automated creation of a reduced-order model for an arbitrary clutch state. Namely, various control system simulation and optimizations studies, such as those presented in [ 7, 8, 9], are based on reduced-order AT dynamics models that are related to specific gears or shifts. In the available literature, generation of reduced-order model for a user-specified clutch state (i.e. gear or shift) is predominantly carried out in a "manual" way [10,11 ]. For example, the approach presented in [ 11] (and similarly in [ 10]) is based on "manual" modification of system matrices by applying boundary conditions for specific gear or shift. In this paper, an automated model-order reduction (MOR) method from [12] is incorporated into the tool for automated generation of the full-order AT model, thus creating a unique tool which generates a minimum realization AT model for an arbitrary clutch state directly from the bond graph model (BGM) implemented in 20-sim. The remaining part of the paper is organized as follows. The next (second) section presents the full-order gearbox model in bond graph and state-space forms. Two methods for automated generation of the full-order AT model based on the 20-sim-implemented BGM are presented in the third section. The fourth section outlines two methods for generation of the reduced-order AT model. Verification of automated modeling methods is presented in the fifth section. Concluding remarks are given in sixth section.A Bond Graph-Based Method of Automated Generation of Automatic Transmission Mathematical Model Vanja Ranogajec and Josko Deur University of Zagreb ABSTRACT The ever-present pressure on shortening the development cycle of transmission systems requires development of numerical methods and tools that would speed up those processes. This paper contributes to the field by proposing a method for automated generation of the full-order automatic transmission (AT) model from a bond graph model that directly reflects the AT structure. The proposed numerical method is implemented within the 20-sim and MATLAB software environments, where 20-sim is used to draw the bond graph and export it to a MATLAB script (or simulate it). A proposed method relies on a system identification method that