The Research Of The Software Of Brake-By-Wire System

By-wire systems have been established for several years in the area of aircraft constructions. There is the visible trend to realize by-wire applications without mechanical or hydraulic backup systems in vehicles. The required electronic systems must evidently be available and safe. This paper addresses a new automotive architecture approach using the time-triggered fault-tolerant TTP protocol that has been designed for class C safety related control applications, like brake-by-wire or steer-by-wire, due to the SAE classification. As an example we present this approach within a brake-by-wire research car without mechanical backup. The intention of this architecture is to tolerate one arbitrary fault - excepting faults of actuators - without any effects of the brake performance. For this purpose we use redundancy in communication (TTP) and electric components like sensors, actuators and power supply.In the past few years there is the tendency in vehicle construction to increase the safety of vehicles by introducing intelligent assistance systems (e.g., Anti Braking System ABS, Brake-Assistant (BA), Electronic Stability Program (ESP), etc.) that help the driver to cope with critical driving situations. Typically for these functions is the active control of the driving dynamic by distributed assistant systems, which need a communication network. Faults in the electronic components, which control these functions are safety critical. However the assistance functions deliver only an add-on service in accordance with a fail-safe strategy for the electronic components. If there is any doubt about the correct behavior of the assistance system, it will be shut down. For brake-by-wire systems without a mechanical backup a new dimension of safety requirements for automotive electronics is reached. After a fault the system has to be fail-operational until a safe state (e.g., vehicle stands) will be reached.1. Discussed the advantages and disadvantages of two kinds of Brake-by-Wire System, and chose Electro-Mechanical Brake system as research object. We also established redundant disposure of hardware in Brake-by-Wire system.2. Introduced On-vehicle communication network and protocol-TTP communication net work for class C, which is applied in by-wire system. TTP/C network is time-triggered and applicable for real-time vehicle control system. The communication between every node of the TTP/C network and Brake-by-Wire Manager are regular. 3. Base on the redundant system, design a frame of the pedal node of brake -by-wire system, the problem of pedal fail lead to the function loss has been solved, discuss how to achieve the fault-tolerant concept and relevant problem.4. Give a concrete research and analyze to the frame software of the brake-by-wire system, define a communication time Scheduler, design the way to achieve the fault tolerant of the software, make sure the function of the brake-by-wire system running under a safe and steady condition.