Constrained and Unconstrained Nonlinear Control of Rubber Tyred Gantry Crane (RTGC) with DC Motor Using Sliding Mode Controller

The increasing exchange of goods between countries and continents necessitates efficient transportation facilities, with cargo seaports playing a vital role. Within each cargo seaport, the Rubber Tyred Gantry Crane (RTGC) stands out as crucial heavy equipment that requires automation to manage heavy cargo traffic and eliminate bottlenecks. While linear control methods are commonly employed to address this challenge, the inherent nonlinear behavior of the system must be considered. This paper focuses on designing a nonlinear control method, specifically the Sliding Mode Controller (SMC), to create an effective MIMO controller for managing the position, cable length, and sway of the gantry crane system. Two DC motors serve as actuators for controlling the trolley position and cable length, which hoists the container. The nonlinear gantry crane model, integrated with the nonlinear DC motor model, is elaborately derived. Subsequently, the designed non-linear SMC control law and sliding surface are simulated to assess control performance. Acknowledging the limitation of the power source and DC motor specifications, the paper also explores control performance when the voltage to control R TGC is constrained within a specified range. The results demonstrate that the proposed method yields excellent control performance for both constrained and unconstrained control outputs.