Agriculture Reference
In-Depth Information
be transmitted and received at predetermined time intervals that helps to eliminate
errors that can occur when multiple messages are sent simultaneously on the bus.
Additionally, the FlexRay protocol is capable of operating as a multidrop bus, star,
or hybrid (using both multidrop and star) networks. This allows the protocol to be
adapted easily into existing bus protocols while also providing increased reliability
where desired with the star network. As automotive and agricultural vehicles develop
in the future, FlexRay will certainly be the next network protocol used to ensure
efficient and reliable data communication.
5.5.4 D
ATA
S
TRUCTURES
Although on-vehicle communication has relatively well-defined data structures (ISO
11783), standards for transfer of data between the farm office and field machinery
continue to evolve. The latter is being driven for the most part by software develop-
ers who recognize the need to reconcile data transfer from the farm office to field
machinery and back again. Today, the need to reconcile data is being driven by map-
based application. “Prescription maps” direct where and how inputs will be applied
to crop production systems. Data regarding input metering and placement is further
complicated by the nature of field equipment application inputs. Crop production
managers and suppliers have multifaceted data transfer needs that range from mov-
ing prescription maps from the farm office to field equipment and then returning
field operation verification files along sensor data for summarizing crop health and
performance to the field office.
One attempt at coordinating data transfer has been proposed and adopted by Macy
(2003) and is termed the Field Operations Data Model (FODM). FODM was created
as a framework to document field operations, and more recently has been expanded
to support business functions. FODM is based on three components: description of
field operation, framework, and a general machine model (GMM). Field operations
are described using one of four models; whole-field, product-centric, operations-
centric, or precision agriculture. The FODM framework is object-based and includes
resources (people, machines, products, and domains) and operation regions (space
and time). Data logged to summarize field operations can either be infrequently
changing data or frequently changing data. The GMM provides a description of the
physical features of field machines including components, sensors, and product stor-
age or containers. An example of a machine definition using the GMM is shown in
Figure 5.2.
5.5.5 A
UTOMATED
G
UIDANCE
Systems designed to accomplish automated guidance on agricultural vehicles can be
seen as far back as the 1920s when furrows were used to guide tractors across fields
with reduced effort from the operator. Since that time, as technology improved, auto-
mated guidance evolved from mechanical sensing to electronic sensors, machine
vision, and GPS to successfully navigate equipment across the field (Reid et al.,
2000). In most cases, operators use automatic guidance to follow parallel paths
through the field. At the beginning of field operations, an A-B line is input into the
