Drive-by-Wire Systems Recent Devlopments Drive-by-Wire Structures with and Drive-by-Wire Systems

Abstract

Automotive systems are increasingly being devel- oped with integrated electronic sensors, actua- tors, microcomputers, information processing for single components, and engine, drive- train, suspension,andbrake systems.These are characterized by the integration of components (hard- ware) and signal-based functions (software), resulting in autonomous functionality. Examples of first steps toward mechatronic systems for automobiles were the arrival of digi- tally controlled combustion engines with fuel injection in 1979 and digitally controlled antilock brake systems (ABS) in 1978. Todays combustion engines are completely microcomputer controlled, typically with five electrical, electrohydraulic, or electropneumatic actuators and several measured output variables, taking into account different operating phases such as startup, warming up, idling, and normal operation. The only input fromthe driver is generated by the accelera- tor pedal and transferred to the throttle (spark-ignition en- gines) or the injection pump (diesel engines) This article begins with a review of electronic driver as- sisting systems such as ABS, traction control (TCS), electronic stability control (ESP), and brake assistant (BA).We then review drive-by-wire systems with and without me- chanical backup. Drive-by-wire systems consist of an oper- ating unit (steering wheel, brake pedal) with an electrical output, haptic feedback to the driver, bus systems, micro- computers, power electronics, and electrical actuators. For their design safety, integrity methods such as reliabil- ity, fault tree and hazard analysis, and risk classification are required. Different fault-tolerance principles with vari- ous forms of redundancy are considered, resulting in fail-operational, fail-silent, and fail-safe systems. Fault-de- tection methods are discussed for use in low-cost compo- nents, followed by a review of principles for fault-tolerant design of sensors, actuators, and communication.We eval- uate these methods and principles and show how they can be applied to low-cost automotive components and drive-by-wire systems.Arecently developed brake-by-wire system with electronic pedal and electric brakes is then considered in more detail, showing the design of the com- ponents and the overall architecture. Finally, we present conclusions and an outlook for further development of drive-by-wire systems.