Fuzzy Control of Waves Generation in a Towing Tank

Abstract

This paper presents the results of research related to the transformation of electrical energy into potential and kinetic energy of waves generated on the water surface. The waves are generated to model the environmental conditions for the needs of the model tests. The model tests are performed on model-scale objects to predict the features of full-scale maritime objects. It is done to improve human safety and the survivability of constructions. Electrical energy is transformed into the energy of the water waves using a wave maker. The wave maker considered is a facility with an electrohydraulic drive and an actuator submerged into the water. The actuator movement results in the waves being mechanically-generated in accordance with the wave maker theory. The study aimed to investigate the advantage of the newly implemented fuzzy-logic controller over the hitherto cascading proportional-integral controllers of the wave maker actuator. The research was focused on experimental investigation of the transformation process outcomes harvested under the fuzzy-logic controller, versus the cascading proportional-integral controllers. The waves were generated and measured in the real towing tank, located in the Maritime Advanced Research Centre (CTO S.A.). The investigation confirmed the advantage of the fuzzy-logic controller. It provides more accurate transformation of energy into the desired form of the water waves of specified parameters—frequency and amplitude—and more flat amplitude-frequency characteristic of the transformation process.

Application of the ISE Optimized Proportional Control of the Wave Maker in a Towing Tank

“…Consequently, the flap movement amplitude decreases when the desired wave frequency increases. The control methods used in the past [21], [39]- [41], [46] did not provide a flat frequency response of the wave maker, as a result of which the amplitudes of successive harmonic frequencies of the white noise were VOLUME 10, 2022 reduced. The ISE optimization method was expected to improve the control system to ensure a constant amplitude along the applied frequencies and meet the required wave modeling accuracy [1], [2].…”

“…9) is optimal -in the ISE (21) [56] sense -for large enough values of k C 1 and k C 2 . The proportional terms of the cascaded controllers seem to be sufficient for minimizing the ISE (21). Thus, the system was finally approved for application with the PCs of stroke piston position (18) and hydraulic cylinder position (22).…”

“…The transfer function between the flap movement and the generated wave has already been presented in literature and follows from the linear wave maker theory [15]- [19]. It is specific to the geometry of the actuator and can be numerically derived [20], [21]. The experimental research has shown that the linear theory, named the 1 st order theory, is applicable when generating waves of low steepness [22]- [25].…”

“…In the first attempt, the control system consisted of proportional-integral controllers optimized in accordance with the Ziegler-Nichols parameters, wherein the ultimate gains and periods were collected using the Åström-Hägglund relay method [40], [41]. In the next attempt, the system consisted of the rulebased Mamdani-type fuzzy-logic control of flap position and velocity, according to the expertise of the authors [21]. The developed solution allowed to meet the required accuracy following from the procedures and guidelines regarding towing tanks [1], [2], [42]- [44], within the scope of the models of wave spectra applied and analysed at that time [12], [45].…”

“…The white noise model of spectra applied in the new method of RAO evaluation [13], [14] established the need to develop a new controller for the wave maker, which would have even more flat amplitude characteristic than those previously delivered [21]. This flat amplitude characteristic was expected to preserve constant amplitude of the white noise along a higher frequency bands.…”