Experimental Design of Fast Terminal Sliding Mode Control for Valve Regulation under Water Load Uncertainty for Precision Irrigation

Abstract

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.

Sliding Mode Speed Control in Synchronous Motors for Agriculture Machinery: A Chattering Suppression Approach

“…Consider the irrigation system depicted in Figure 1. The water tank is fed from a nearby water source; according to [18], the pressure uncertainties occur due to the tank water level. The valve is controlled by a DC motor that controls the open position for irrigation needs.…”

“…where θ represents the DC motor's position to control the valve, and u is the control input [18]. Now, for simulation purposes, the sliding surface selected for the system is…”

“…This control technique is easy to implement and can deal with uncertainty for precision irrigation applications. To reduce the chattering phenomenon, sign function approximation demonstrates simplicity and good performance [18].…”