Biosystems Engineering (2006) 94 (2), 165–177 doi:10.1016/j.biosystemseng.2006.02.012 AE—Automation and Emerging Technologies Fuzzy Greenhouse Climate Control System based on a Field Programmable Gate Array Rodrigo Castan˜ eda-Miranda; Eusebio Ventura-Ramos Jr.; Rebeca del Rocı´o Peniche-Vera; Gilberto Herrera-Ruiz Biotronics Laboratory, Faculty of Engineering, Universidad Auto´noma de Quere´taro, Cerro de las Campanas s/n, Quere´taro, Qro. Me´xico. CP., 76010, Mexico; e-mail of corresponding author: rcast@uaq.mx (Received 25 January 2006; accepted in revised form 16 February 2006; published online 21 April 2006) Fuzzy control is a practical alternative for the design of a great variety of control applications. It provides an advisable method for the design of non-linear controllers using heuristic information. This article presents the development of a greenhouse intelligent climate control system that uses a fuzzy controller, based on a field programmable gate array (FPGA). The FPGA has a great potential for use in agricultural technology development due to its characteristics to produce fast prototypes of complex hardware designs with an effective production cost. A low-cost intelligent system designed in a single chip with the task to carry out the complete functionality for the greenhouse climate control was developed. The system proposed here is a good option to unload the low-level tasks (monitoring of climate variables and operation of actuators, such as heaters and windows to control the greenhouse inside temperature) from the main control system, in order to leave to the main controller the high-level tasks as plant monitoring, control of vegetative development, production planning, irrigation system control, which need a high computational power. The system developed in this work consists of: a signal conditioning sub-system, a data-acquisition sub-system, digital/ analogue conversion sub-system and a FPGA sub-system. The FPGA sub-system has three units: the synchronisation unit, the personal computer interface unit and the fuzzy logic unit, all implemented within a FPGA-integrated circuit, conforming to a system-on-a-chip (SoC). The design, compilation and simulation of the FPGA sub-system were carried out in the Active-HDL environment using the hardware description language VHDL. The Co-simulation Active-HDL/Simulink and experiments that show the performance of the complete system are presented. r 2006 IAgrE. All rights reserved Published by Elsevier Ltd 1. Introduction Under greenhouse production, the climate control is a tool used for crop yield manipulation which maximise the entrepreneurial benefits. Once the objectives that optimise crop growth and development are defined, the control engineer must design and implement automatic control systems that make possible to obtain a maximum crop yield at minimum production costs. In this sense, control engineering has undergone a considerable devel- opment. Researchers have used many control techniques in different fields, from the conventional or classic strategies [proportional integral derivative (PID) control, cascade], artificial intelligence (AI) (fuzzy control, neural networks, genetic algorithms), advanced control techni- ques (predictive control, adaptive), to robust control strategies, no-linear and optimal control. Specifically, they have been applied in the area of greenhouse climatic control (Lees et al., 1996; Hanan, 1998; Tap, 2000). Conventional control techniques are difficult to implement in greenhouse systems due to their multi- variable and non-linear nature, where inter-relations between internal and external variables are complex (physical non-linear phenomena that governs these systems dynamics are complicated). This provides justification for the use of intelligent control techniques as a good alternative. In this way, fuzzy logic as part of AI techniques is an attractive and well-established ARTICLE IN PRESS 1537-5110/$32.00 165 r 2006 IAgrE. All rights reserved Published by Elsevier Ltd