The steering systems in modern automobiles provide an everyday example of carefully tuned haptic interfaces that enable high performance human-machine interaction. Cars sold today still use a mechanical linkage as did vehicles nearly a century ago, but there are potential advantages of steer-by-wire systems, for instance improved crash worthiness, packaging under the hood, and real-time tuning the steering ratio and power assist. In designing a steer-by-wire system, a set of sensors and actuators must be selected and these devices have limitations such as bandwidth and resolution. Additionally, a communication link with limited bandwidth must be selected to connect the steering wheel to the front wheels. Our research on steer-by-systems draws from the fields of haptics, tele-operation and linear feedback control theory to answer questions about the design of the control system and selection of sensors, actuators and communication. We seek fundamental design limitations and trade-offs when analyzing system performance in terms of transparency, passivity and stability robustness.
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