Todd V. Elliott

Performance Assessment of Wireless Sensor Networks in Agricultural Settings

Wireless Sensor Network (WSN) utilizes radios operating primarily in the 900 MHz and 2.4 GHz frequency bands. In general, as frequency increases, bandwidth increases allowing for higher data rates but power requirements are also higher and transmission distance is considerably shorter. In general, depending on the operating environment, significant signal loss can occur at these frequencies particularly when the radios require line-of-sight for optimal performance, with 2.4 GHz more susceptible than 900 MHz. For agricultural applications, WSN must be able to operate in a range of environments, from bare fields to orchards, from flat to complex topography, and over a range of weather conditions, all of which affect radio performance. However, there are limited data on radio performance as affected by agricultural setting and no standard tests are available for quantifying WSN performance in agricultural applications. Using a low powered, 10 mW 900 MHz frequency hopping spread spectrum radio, we developed a range of tests intended to quantify the performance of agricultural WSN in fields, vineyards, and orchards over a range of crop and weather conditions. Performance data include different metrics of radio performance such as packet delivery and signal strength along with power consumption tests under different supply strategies. This paper evaluates the extent to which various tests can be used to quantify WSN performance and how WSN perform under various cropping systems.

A Remote Irrigation Monitoring and Control System for continuous move systems. Part A: description and development

Continuous move irrigation systems have been modified since the 1990s to support variable rate irrigation. Most of these systems used PLC (Programmable Logic Controllers) technology that performed well for on-site control but were very expensive to add remote, real-time monitoring and control aspects that have been made possible by wireless sensor networks and the Internet. A new approach to the monitoring and control of continuous move irrigation systems is described. This system uses a Single Board Computer (SBC) using the Linux operating system to control solenoids connected to individual or groups of nozzles based on prescribed application maps. The main control box houses the SBC connected to a sensor network radio, a GPS (Global Positioning System) unit, and an Ethernet radio creating a wireless connection to a remote server. A C-software control program resides on the SBC to control the on/off time for each nozzle group using a “time on” application map developed remotely. The SBC also interfaces with the sensor network radio to record measurements from sensors on the irrigation system and in the field that monitor performance and soil and crop conditions. The SBC automatically populates a remote database on the server in real time and provides software applications to monitor and control the irrigation system through the Internet.

WISE: a web-linked and producer oriented program for irrigation scheduling

The Washington Irrigation Scheduling Expert (WISE) Software was developed to meet the needs of Washington state irrigators. WISE was written in JAVA with NetBeans DeveloperX2 components to allow cross platform operation and easy access to reference evapotranspiration from Washington states sixty Public Agriculture Weather System stations. The graphical user interface is intuitive and helps the user input their field-specific parameters such as crop type/timing, soil moisture status and irrigation system specifications. WISE employs a short-term water balance that can be adjusted for existing soil-moisture conditions. WISE is not a black box calculation of when and how much to irrigate since important steps are displayed and made apparent to the user. This feature also makes WISE an educational tool that teaches the principles of irrigation scheduling.

A Remote-Real-Time Continuous Move Irrigation Control and Monitoring System

Continuous move irrigation systems have been modified since the 1990s to support variable rate irrigation. Most of these systems used PLC (Programmable Logic Controllers) technology that did a good job of on-site control but were expensive to add remote, real-time monitoring and control aspects made possible by wireless sensor networks and the Internet. A new approach to control and monitoring continuous move irrigation systems is described. This system uses a Single Board Computer (SBC) using the Linux operating system to control solenoids connected to individual or groups of nozzles based on prescribed application maps. The main control box houses the SBC connected to a sensor network radio, a GPS unit, and an Ethernet radio creating a wireless connection to a remote server. A C-software control program resides on the SBC to control the on/off time for each nozzle group using a “time on” application map developed remotely. The SBC also interfaces with the sensor network radio to record sensors on the irrigation system monitoring performance and in the field monitoring irrigation soil and crop conditions. The SBC automatically populates a remote data base on a server in real time and provides software applications to monitor and control the irrigation system from the Internet.

Performance of a Continuous Move Irrigation Control and Monitoring System

Precision irrigation systems can have inherent errors that affect the accuracy of variable water application rate and affect the transferability of the control system. The objective of this paper was to assess the performance, and transferability of a remote irrigation monitoring and control system (RIMCS) designed for precision water management on continuous move irrigation systems. The RIMCS varies water application rate by pulsing nozzles controlled by solenoids connected via relays to a single board computer (SBC) with wireless Ethernet connection to a remote server. The system also monitors irrigation system flow, pressure, and position and accommodates wireless sensor networks installed in the field. The system was installed on a linear move (LM) irrigation system in the lower Yakima Valley of eastern Washington State and on a LM in the Nesson Valley of western North Dakota. For the Washington LM, four pre-defined irrigation patterns were imposed under each of two spans and variable rates were applied as a percentage of the nozzle base application rate. Each nozzle was pulsed to create the intended irrigation pattern across the span length and along the LM travel direction. Tests were conducted in the months of June, August and September 2005. For the North Dakota LM, a quadratic pattern was imposed pulsing banks of nozzles along the LM travel direction. Standard catch can tests were performed at the middle of the irrigation pattern blocks, at the blocks boundaries and for the typical LM sprinkler application pattern. The system performance was evaluated using catch can water depth error assessment when compared to set target values. Variable water application depths using the RIMCS created the target application patterns with application accuracies in the range of uniform application uniformity coefficients of 88 – 96%. The RIMCS was successfully transferred to another LM in North Dakota.

Precision Irrigation with Wireless Monitoring and Control System Technology

Continuous move irrigation systems have been modified since the 1990s to support variable rate irrigation. Most of these systems used PLC (Programmable Logic Controllers) technology but were expensive to add remote, real-time monitoring and control through wireless sensor networks and the Internet. This article presents new technology to monitor and control continuous move irrigation systems. Two different systems were developed and installed on 2 spans of a 4-span Linear Move irrigation system: a) a Single Board Computer (SBC) connected via relays to solenoid valves/spray nozzles, sensor network radios, a GPS, an Ethernet radio, and a remote server; and b) a single wire (SW) monitoring and control system that uses a five-wire conductor cable, with 2 wires to carry 24VAC power, 2 wires to support RS-485 communications signals, and one wire as a common ground. A nozzle controller interfaces the RS-485 wire and each solenoid. The ubiquitous protocol MODBUS was implemented on all controllers for receiving and transmitting information to individual controllers. One main difference between the SBC and the SW system is the significant number of wires that is reduced using the latter system. This system reduced the cost of materials significantly and cut the installation requirements to a small fraction of the previous system in which each nozzle was wired individually to a control board. Both systems can be managed through the internet by means of an applied interface program.