Drive-By-Wire

Abstract

Competitiveness to a company is given by innovations. The chassis as main part in vehicle design is incisive to the driving behavior of a car. On the one side, mechanical devices are well-engineered which means differentiation to competitors in mechanical devices is complex and costly. On the other side, improvements due to clients and legislator such as driving dynamics, CO₂ reduction, or pedestrian protection increase the requirements to the chassis concerning comfort, safety, handling, or individualization by less cost and maintenance.

This balancing act can be done by mechatronics systems which means the interaction of mechanic, electronic, and informatics devices. Basic mechatronics systems are used to assist the driver (e.g., power steering) or to overrule a wrong driver input (e.g., ABS brake). Different from this so-called by-wire systems are extensive mechatronics systems where the vehicle behavior and the driver feedback can be designed independently (there is no mechanical link between input and output).

Drive-by-wire, X-by-wire, or simply by-wire technology is already present nowadays. Starting with aeronautics, where fly-by-wire has been used extensively in the Airbus A320 family without mechanical backup. In passenger cars, by-wire functionality and by-wire systems are far more recent, but still already well known (VDI-Bericht 1828, 2004).

One can distinguish between by-wire functionality and by-wire system. The by-wire functionality can be reduced to the ability to control or even only apply a force by an electrical signal (through an electrical wire) to the vehicle. The definition by-wire system is that the line between the driver’s input interface and the actuation which produces force is partly designed by wire. Hence, in contrast to the by-wire functionality, the system has no permanent hydraulic or mechanic linkage between them.

Common advantages of by-wire systems are the freedom in functionality, package integration, reducing variants, design, and enabler for driver assistance functions. In Sect. 1, these general facts of by-wire systems, the vehicle-driver control loop, and aspects of the input module behavior will be shown. Afterward longitudinal and lateral dynamic systems and their functionality are explained in more detail (Sects. 2 and 3).

One benefit of by-wire systems is the system and functional integration. In Sect. 4 integrated corner modules are illustrated and analyzed as well as integrated control strategy aspects. The challenge of by-wire systems are the functional safety requirements, especially in terms of availability. The latter is the most important for the OEMs and customers. Any minor failure of the systems, which has to be displayed in the dash board, will reduce the customers’ faith in the car. These aspects will be explained in Sect. 5.