Agriculture Reference
In-Depth Information
These networks provide a coverage range of up to 183 m and operate typically at a
frequency of 2.4 GHz.
5.5.3 O
N
-V
EHICLE
C
OMMUNICATIONS
With the introduction of microcontrollers to agricultural field machinery, it was not
long until equipment designers realized the need to share and manage information
between controllers. Following the lead of the truck, bus, and automotive industries,
equipment designers began looking for bus configurations and data structures to
support continuing machinery development. Quickly, most designers realized the
need for standardization to facilitate interoperability and interchangeability, and the
industry came to grips with hitching (ISO 730, 2009) and hydraulic systems (ISO
5675, 2008). The following discussion highlights some of the more significant mile-
stones in the evolution of on-vehicle communications and concludes with a brief
treatment of what the industry can expect in the near future.
The Landwirtschaftliches BUS System is regarded as the precursor to ISOBus.
Development of this protocol began in Germany in the late 1980s by a commit-
tee formed from the German Farm Machinery and Tractor Association (Stone et
al., 1999). CAN version 1 was used as the base for developing this new agricul-
tural communication bus protocol (Auernhammer, 1983). The protocol was devel-
oped with the goal of running distributed process control systems such as fertilizer
distribution, pesticide application, and irrigation (Munack and Speckmann, 2001).
Therefore, development on the protocol began with the goal of standardizing net-
work data exchange between electronic components on agricultural tractors and
implements. Based on the preliminary work by Auernhammer (1983) in Germany,
ISO was requested to begin the development of a standardized protocol for agricul-
tural equipment in the early 1990s.
ISOBus is a distributed network protocol specification (developed under ISO
11783) for equipment that use CAN technology for electronic communication in the
agricultural industry. Development of this ISO protocol began when a working group
was formed to develop an interim connector standard (ISO 11786). In 1992, ISO
11783 was formed to continue the development of the communications protocol stan-
dard. Initially, much of the ISOBus standard was based on protocols developed by
the automotive industry (SAE J1939); however, revisions have been made to support
applications in the agricultural and forestry equipment industries. The main goal of
ISO 11783 was to standardize electronic communications between tractor compo-
nents, implement components, and the tractor and implement (Stone et al., 1999).
FlexRay is a distributed network protocol that has been developed to improve on
existing CAN technology. These protocols were developed by the automotive indus-
try. Like CAN under ISO 11783, it is quite likely that FlexRay will be integrated into
agricultural vehicles in the near future. One of the problems associated with existing
CAN protocols is that in some cases, equipment manufacturers are at a point where
the CAN bus band width is nearing saturation. FlexRay offers the ability for data
to be transferred at higher frequencies (10 Mbps) compared to existing CAN proto-
cols (250 Kbps) typically used today (National Instruments, 2010). Another impor-
tant aspect of FlexRay is that it uses a time-triggered protocol that allows data to
