Agriculture Reference
In-Depth Information
personal protection equipment (PPE) at all during the handling of pesticides. The
majority of those reporting wearing PPE, 52%, wore only gloves or long pants. In
addition, substantial numbers of tractors used in chemical applications are still open-
stationed, which increases the risk of chemical exposure to farm workers.
The combined effect of limited PPE use during the handling of pesticides with the
high probability of exposure increases the potential for negative effects of pesticides
on operators' health. This effect places a premium on the development of systems,
which limit the required handling of the pesticide by the operator (during mixing and
cleaning processes), as well as the reduction in the amount of pesticides encountered
inadvertently through spray drift and off-target application. These requirements of
chemical spray technology have been the drivers of continuous advancement of vari-
ous aspects of application automation technology as detailed in the next section.
10.3
AUTOMATION OF CHEMICAL APPLICATION SYSTEMS
10.3.1 B
ACKGROUND
Automation and mechanization in chemical application systems has undergone a con-
tinuous evolution for more than a half century to address various concerns explained
in Section 10.2. Although the first pressurized agriculture sprayer was developed in
1883 by John Bean (Brann, 1956), it was not until 1947, when Ray Hagie invented
the first commercially successful self-propelled sprayer, that a dedicated mechani-
cal platform existed for developing automated chemical application systems. Since
this time, sprayer development has progressed to meet growing demands for more
efficient, higher capacity sprayers.
The fundamental goal of automation in chemical application technology is to
improve the precision and uniformity of chemical application while increasing
biological efficacy and reducing environmental impact. The purpose is to achieve
safe, economical, and efficient pesticide applications. These three components have
served as a unique driving force for rapid development of the chemical application
industry and the underlying automation technology. Many different types of control-
lers are used in chemical application systems to optimize system performance that
helps achieve this overall goal. Generally, various control mechanisms being used
by a state-of-the-art chemical application system (Figure 10.3) can be classified into
four groups: (1) rate control, (2) nozzle/droplet control, (3) section control, and (4)
boom/tower control.
Sprayers use rate controllers to adjust the volume delivery rate to achieve a more
consistent formulation application rate based on a number of disturbances to the
system including changes in spray swath width due to boom or nozzle section control
in boom sprayers, changes in the application rate due to commanded changes from
a field computer implementing variable rate control, and acceleration or deceleration
of the vehicle. To fully implement variable rate control, flow control needs to be
implemented along the spray structure (e.g., boom in boom sprayers), so that higher
spatial resolution can be achieved in the lateral dimension(s) across the sprayer, in
addition to what is already implemented in the direction of travel. Such lateral rate
control enables the correction of application rate based on high-resolution spatial
