X-By-Wire via ISOBUS Communication Network

Abstract

Satellite based guidance technology is a very challenging principle for future automation of agricultural machinery. The first generation types of systems are primarily self-contained solutions and added to the existing system set-up of the tractor. As being an important step towards robotics in agricultural machines, a better integration of this technology into the mechanical, hydraulic and especially the electronic architecture is a major issue. In principle, there are two main strategies for the integration. One is a concept based on a proprietary, manufacturer specific approach. The other one is to map as many functions as possible into the just state of the art becoming open and standardized ISOBUS. Within this paper, the capabilities of ISOBUS to be used for X-by-Wire applications are discussed from different point of views. In consequence, ISOBUS can only be used to create X-by-Wire applications with mechanical or hydraulic backup. Basic real-time capability with a reaction time of 100 ms seems to be achievable. However, some features of time-triggered protocols like determinism should be integrated by simulation on application layer level. Such concepts are the introduction of a heartbeat mechanism to serve as a coarse time synchronization and timeout reference. Additionally, the lack of unique and hard-wired addressing within ISOBUS demands new concepts like encryption algorithms. Based upon these theoretical considerations, a first proposal for a Steer-by-Wire approach via ISOBUS has been derived and implemented. First results are very promising, but further investigations like fault injection trials and extended network set-ups with pre-defined bus load scenarios are necessary.