ABSTRACT Due to the multitude of external design constraints, such as increasing fuel economy standards, and the increasing number of global vehicle programs, developers of automotive transmission controls have had to cope with increasing levels of system complexity while at the same time being forced by the marketplace to improve system quality, reduce development costs, and improve time to market. GM Powertrain (GMPT) chose to meet these challenges through GM's Road-to-Lab-to-Math (RLM) strategy, particularly the Math based method of a virtual vehicle simulation environment called System Simulation. The use of System Simulation to develop transmission control algorithms has enabled GMPT to improve product quality and reduce development times and costs associated with the dependence on physical prototypes. Additionally, System Simulation has facilitated the reuse of GMPT controls development assets, improving overall controls development efficiency. The Mathworks Simulink® tool forms the basis for the GMPT Transmission System Simulation environment, or virtual vehicle. This paper describes this virtual vehicle environment, its key components, and its application to transmission algorithm development. INTRODUCTION GM's Road-to-Lab-to-Math (RLM) initiative is a fundamental engineering strategy leading to higher quality design, reduced structural cost, reduced reliance on physical test and hardware and improved product development time [1]. A key strategic element of the GM's RLM is to move engineering activities and processes that require vehicles onthe road to Lab or Math. Using Math based methods and moving algorithm development to the early stage of product development cycle offers opportunities for numerous benefits: improved system engineering and quality (e.g., system tradeoff study), reduced development costs by avoid using expensive development vehicles, and improved time to market. In order to do transmission algorithm development using Math based methods, not relying on physical vehicle and hardware, a transmission system simulation is required. The system simulation and its usage for algorithm development are not new in automotive industry. However, this paper presents a unique approach of developing TCM control software consisting of both handcode and autocode algorithms using a transmission system simulation. In this paper, a transmission system simulation is established, transmission algorithm development using this system simulation is described, and, finally, the benefits of this new way of transmission algorithm development are summarized. TRANSMISSION SYSTEM SIMULATION What is a Transmission System Simulation? Instead of answering directly, it may be easier to explain by highlighting key attributes of the Transmission System Simulation. The Transmission System Simulation is a non real-time and closed-loop system, which includes TCM application software and vehicle plant model. The vehicle plant model includes engine, transmission gearbox with control hardware, and vehicle dynamics. The Transmission System Simulation runs on a computer and thus no vehicle or extra hardware are required. Compared to a transmission TCM hardware-in-loop Transmission Algorithm Development using System Simulation (Virtual Vehicle)2011-01-1233 Published 04/12/2011 Xuefeng Tao, Michael Kropinski, Colin Hultengren, Kenneth Lang and Manmeet Mavi General Motors Company Copyright © 2011 SAE International doi:10.4271/2011-01-1233Downloaded from SAE International by Univ of California Berkeley, Friday, July 27, 2018 (HIL) bench, the Transmission System Simulation are similar in terms of common plant models and testing TCM control software and may be referred as to a virtual HIL. As the goal of the Transmission System Simulation is to simulate the vehicle behaviors (in terms of transmission functionality) as close as possible to a physical vehicle, it can be thought as a virtual vehicle on the computer. The Figure 1 below illustrates th