Solar pump moved by fuzzy logic

Researchers from the American University of Sharjah in the United Arab Emirates have proposed an irrigation system featuring a standalone PV system, a single microcontroller-based platform that utilizes a fuzzy-logic algorithm for decision-making, and a wireless monitoring interface for remote monitoring.

Their proposal is based on a system that operates with 5.5 ​hours of constant bright sunshine per day, at an average ambient temperature of about 25 ​°C. “The irrigation system presented in this paper is designed for a miniature farm – this allows us to simulate and prototype on a smaller scale of the proposed irrigation system,” the researchers said.

The system is powered by a solar installation to provide electricity to a charge controller, which in turn charges a battery during the day. At night or during periods of low radiation, the charge controller draws power from the battery and feeds it into the irrigation system.

Core element

The scientist said that the core element of the system is the MyRIO controller, which is a real-time embedded evaluation board manufactured by U.S.-based National Instruments, featuring its own onboard field-programmable gate array (FPGA) and microprocessor. “FPGA has gained popularity due to its speed of operation, a relatively lower cost compared with traditional microprocessor units, reliability, and ease of long-term maintenance,” the researchers said.

The controller features 10 analog input channels, six analog output channels, 40 digital input/output lines, three embedded accelerometers, and a Wi-Fi adapter. “The controller digital and analog inputs are used to interface with the float switches, soil moisture sensor, humidity and temperature sensor, and flow rate sensors, which are connected to the controller,” the researchers wrote.

The board has a relay that acts as an interface between the diaphragm pump and a bilge pump to control the irrigation process.

Smart sensing

A smart sensing unit – featuring a controller, charge controller, buck converter, and relay board – performs all the fuzzy logic-based pump control operations.

Although it is based on mathematical concepts, fuzzy logic is known to provide clear solutions to complex problems, as it somehow seems to reflect human thinking and decision-making. While conventional logic works on precise inputs and produces definite outputs like “true” or “false” and “yes” or “no,” fuzzy logic includes a broader range of possibilities than just “yes” or “no,” like “certainly yes” or “possibly not,” for example.

In the proposed system, values from the sensors are fuzzed up into linguistic terms and the member functions are created accordingly. “The terms were named as “High,” “Medium,” and “Low” for the humidity and soil moisture sensors, and “Very hot,” “Hot,” “Cold,” and “Very Cold” for the temperature sensor,” the scientists said, noting that the number of linguistic terms and their names are completely up to the preference of each user.

The researchers claim that the fuzzy algorithm they developed can create fuzzy values for the outputs, based on the fuzzy values of the input. That can then be defuzzified into actual outputs. Previously, a set of “if-then” rules had to be created, based on the number of linguistic terms for each input, and the number of inputs. “The fuzzy logic algorithm was developed to analyze the environmental and soil conditions to decide when it should irrigate the farm,” the scientists explained.

Lab tests

The research team has tested the prototype in a lab environment to validate the overall system design from the perspective of the sensor interface, pumps interface, and fuzzy logic rules. “The system operated as desired in all modes including the remote access mode,” the researchers said.

They describe the system in IoT-solar energy powered smart farm irrigation system, which was recently published in the Journal of Electronic Science and Technology.