INTERNATIONAL JOURNAL OF AGRICULTURE & BIOLOGY 1560–8530/2007/09–1–59–63 http://www.fspublishers.org Design and Evaluation of Automatic Agricultural Land Leveling Control System for Scraper S.S. MOHTASEBI 1 , A. HOSSEINZADEH, M. OMID AND N. ABOLFATHI† Department of Bio-System Engineering, University of Tehran, Karaj, Iran †Mechanical Engineering Department, North Dakuta University, USA 1 Corresponding author's e-mail: mohtaseb@ut.ac.ir ABSTRACT An automatic land leveling control system (ALLCS) consists of different sections such as electronic circuitry, laser and hydraulic devices in order to adjust the height of scraper. A laser beam strikes a photocell array and then the electronic circuit detects the level of the laser beam. If the level of laser beam is not the same as set point, a control signal is transmitted in order to adjust the height of the scraper. In this paper, investigation on design and operation of different parts of the ALLCS are presented. The steady state and transient responses of the system are also discussed. First, the whole system and also the design of its components are described. The block diagram of control system and the mathematical model of its various sections are presented next. Then, based on these equations, the mathematical model of whole system is derived. This model is solved and analyzed by MATLAB's Simulink and the responses of system to different inputs are obtained. The transient response of system to inputs of 10 and -8.5 cm amplitude step functions for embankment and landscape, respectively were investigated. For the embankment, the response was over damped and the time to reach the steady state was 1.15 second. The difference between steady state error simulation and experiment was about 0.04 mm. For the landscape case, the response was over-damped too. However, the steady state response time was faster. This is due to the fact that the height for landscape case was smaller. Based on the experimental and simulation results, the validity of the model is confirmed. The model may be used as a reference to evaluate the functionality of the control system at different operating conditions. Key Words: Automatic control system; Precision farming; Agricultural land leveling; Computer simulation; Mathematical model; Scraper INTRODUCTION Now-a-days, in order to gain maximum efficiency, precision farming is applied and it is tried to use all entries with their optimum values. Moreover, precise land leveling is a prerequisite for achieving high irrigation efficiencies at the field level (Rajput & Patel, 2002). Roberts et al. (2000) conducted a research to introduce laser and satellite controllers and to investigation the dynamic behavior of those controllers. They installed each of controllers on height control machines such as distributor asphalt machine, bulldozer, mechanic hoe bucket and grader. Results showed that turbulences in laser systems are less than satellite systems and their responses are over-damped, however by filtering data, it is possible to decrease the turbulences of satellite control systems (Roberts et al., 2000). El-Yazal and Wissa (1990) did a research on cane fields to study the value of consuming water in Egypt in 1990. They concluded that in fields leveled with laser leveling machines, with mechanical leveling machines and without any controller (traditional), the quantity of required water are 18404, 23428 and 25488 m³/ha, respectively (Walker, 1989; Haynes, 1996). Also, the quantity of product when they used laser leveling machine, mechanical leveling machines and without any controller were 107.9, 88.7 and 71.9 ton/ha, respectively (El Yazal & Wissa, 1990). At present, land leveling machines with mechanical controllers are seldom used due to their low accuracy. For high accuracy, low cost and programming ability, in precision farming, electronic control systems are suitable substitution. Generally in land leveling systems with mechanical controller, the accuracy of operation depends on skills, experiences and safety of operator. In order to alleviate these problems, design and manufacture of an automatic electronic control system of height was conducted. If an automatic control system in leveling machines is used then it is not necessary; (i) to perform topography operation using topography cameras in order to determine the height of different points, (ii) to do engineering calculation, which is done in traditional methods and to pay attention to the quantity of landscape and embankment points. MATERIALS AND METHODS An automatic control system of leveling machine having laser control comprises of four main parts; laser transmitter, receiver, electronic circuits, hydraulic section, which are described as follows: Laser transmitter system. This section is separated from