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In terms of vehicle dynamics, four-wheel drive exhibits great capabilities as a power transmission system for high-performance passenger cars. There are now numerous different concepts for four-wheel drive configurations. To provide an overview of the different systems and their characteristics, this report first defines the design requirements for four-wheel drive systems. It then compares the alternative concepts in schematic form. Finally, the results of simulations and measurements are given to describe the characteristics of the quattro system developed by Audi in the various stages of its development.

This paper presents a novel encoding scheme as an alternative to Analog amplitude encoding for communicating sensor signals. The scheme has the potential of becoming a non-proprietary industrial standard for communicating sensor information to electronic control modules. Key features of the encoding scheme are the ability to communicate two sensor values using only 3 wires (power, ground and signal) with 12 bit resolution within 1ms. The scheme includes a checksum for error detection and a mechanism for reporting serial data such as low rate sensor information, part numbers or fault codes. Data is communicated to the receiving module by varying the time between discrete (single edge polarity) transitions. The encoding is self-calibrating and does not require an expensive crystal in the sending module (assumed to be a low-cost ASIC) to maintain signal integrity.