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The application of control systems in precision irrigation is critical to ensure the accurate distribution of water in crops under various uncertainties. Shifts in the loading of the water supply on the control valve can be a significant uncertainty. Changes in weather and the uncertainty of the water level in the reservoir are also challenging issues. Sliding Mode Control (SMC) is a robust control technique that is simple to apply to deal with uncertainty, while Fast Terminal Sliding Mode Control (FTSMC) has the benefit of the rapid convergence. The DC electric motor, which is a common component of electric control valves, can be employed in designing control techniques for precision irrigation applications. This study aims to design a proposed experimental-based method, namely FTSMC for valve regulation under water load uncertainty for precision irrigation application. Modification of the signum function should be used to eliminate the chattering effect in real experiments.The results of experiments showed that the proposed method was superior to the conventional Proportional Integral Derivative (PID) and traditional SMC techniques in terms of overshoot, convergence rate and error. Because of those reasons, the FTSMC approach should be implemented on control valves against load uncertainty in precision irrigation applications.

The purpose of this study was to produce an application program for the data processing unit of a web base rain gauge calibrator. The application program was developed using Studio XE2 of C ++ RAD (Rapid Application Development) software. Testing result shows that what you get was what you command or there was no different between the result and the command.

Rain gauges in Indonesia need recalibration at least twice a year, viz. at the end of dry season where the rain gauges will soon work harder and at the end of rainy season where usually there are many garbage on each rain gauge orifice. Based on the direct surveys in the fields and discussions at some rain gauge calibration laboratories in Indonesian western, central, and eastern parts, the calibration officers in the visited offices generally used manual rain gauge calibrators to recalibrate rain gauges on their fields. Therefore, the dependency of calibration results to the human beings is very high. Meanwhile to avoid data gathering discontinuation, rain gauges should be recalibrated in situ. To cope with this problem and other issues related to rain gauge calibrators, a research to develop a web based rain gauge calibrator was carried out. The research result using research and development method showed that this calibrator can work well as an in situ and ex situ rain gauge calibrator.

This paper presents a simple and straightforward design of a discrete-time fractional-order odd-harmonics repetitive controller (RC). Unlike general RC designs, the proposed method utilizes an internal model with a half-period delay and a stabilizing controller with a fractional phase lead compensator. First, the odd-harmonics internal model representing odd-harmonics frequencies is constructed by using the information of the reference’s basis period and the preferred tracking bandwidth. Secondly, an optimization problem synthesized from the stability condition of the RC closed-loop system is solved to obtain the fractional phase lead compensator. Finally, the fractional term of the stabilizing controller is realized by using a causal and stable infinite impulse response (IIR) filter, where the filter coefficients are computed by applying the Thiran formula. Simulation and experimental validation on a servomotor system are conducted to verify the effectiveness of the proposed design.

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