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Steer by Wire systems provide many benefits in terms of functionality, and at the same time present significant challenges too. Chief among them is to make sure that an acceptable steering feel is achieved. Various aspects of this subjective attribute will be defined mathematically. A control system that is architected specifically to meet these challenges is presented. Furthermore, the design is made such that it would be robust to tire and loading variations. Supporting vehicle data and model results are shown as needed.

Electric power steering (EPS) is an advanced steering system that uses an electric motor to provide steering assist. Being a new technology it lacks the extensive operational history of conventional steering systems. Also conventional systems cannot be used to command an output independent of the driver input. In contrast EPS, by means of an electric motor, could be used to do so. As a result EPS systems may have additional failure modes, which need to be studied. In this paper we will consider the requirements for successful EPS operation. The steps required to develop diagnostics based on the requirements are also discussed. The results of this paper have been implemented in various EPS-based programs.

An Electric Power Steering (EPS) System will be considered in this report. The modeling of this dynamic system will be achieved with both simplicity and usability taken into account. As such, a Reduced Order Model that reveals the important dynamic distinctions of the system will be developed from a more complex one. This model will be used to analyze various closed loop effects such as torque performance, disturbance rejection, noise rejection, road feel, and stability. These fundamental effects (compromises) are used toward the design of a desired control system. This modeling philosophy together with a comprehensive understanding of system compromises is essential to an optimized EPS system.

Electric power steering is a technology that will define the future. It eliminates the need for a power steering pump, hoses, hydraulic fluids, and a drive belt and pulley on the engine. As a result, electric power steering is energy efficient and environmentally compatible - while offering extras like simplified tuning, packaging flexibility and engine-off steering assist. With superior performance, electric power steering will be the technology that challenges the familiar, 50-year-old concepts of hydraulics.