Active vibration control of a flexible rod moving in water

Nuclear energy has been used in many applications globally and especially in the developed countries, thanks to the development and advancement in nuclear technology. For instance, harnessing and using of nuclear power for industrial and domestic uses have been explored due to its large potential of supplementing other energy sources like electricity. Generally, refueling machines that transport nuclear fuel rods from one location to the other in the nuclear reactor consist of a trolley and a bridge. Consequently, the fuel rod undergoes transient and residual vibrations both during the transport and at the target position due to the drag and vortex-induced forces that impede their efficient transportation to the desired location. Furthermore, induced rod deflections can damage the material within the rod that may result in safety hazards. Therefore, it is of significant importance to eliminate the unnecessary rod vibrations as a way of ensuring reactor’s safety and thus researchers have identified simultaneous control of the trolley and the bridge of the refueling machine as a potential solution.

Recently, Dr. Umer Hameed Shah and Dr. Keum-Shik Hong at Pusan National University from School of Mechanical Engineering investigated simultaneous control of the bridge and a trolley of a refueling machine and its potential use in eliminating the unnecessary vibration during the transportation of the fuel rod. Their research work is currently published in the research journal, Automatica.

Briefly, the authors commenced their experimental work by developing a hybrid model of the refueling machine comprising of the bridge and trolley. The equations of motion for the system were derived through Hamilton’s principle. In addition, a boundary control scheme, through derivation of the control law, to simultaneously suppress both the lateral and transverse vibration during the transportation of the fuel rod was developed. The two control laws include one for the bridge and the other for the trolley. Lyapunov functions based on the stability were employed to evaluate the boundedness of the systems and its overall effectiveness. Eventually, experimental and simulation results were compared to verify the feasibility of the model.

The authors observed that the boundary control laws were capable of simultaneously suppressing both the transverse and lateral vibrations of the rod while at the same time controlling the position of the refueling machines accurately. It was necessary to perform a closed-loop system analysis that indicated that the errors for the rod vibrations and the position of the bridge and trolley were bounded uniformly in the presence of hydrodynamic forces. Furthermore, the simulations and experimental results agreed well thus indicating the accuracy of the developed model.

The study successfully developed a valid and feasible hybrid model for simultaneously controlling the position and vibration of a nuclear refueling machine for efficient transportation of nuclear fuel rods to the desired positions in the nuclear power reactors. The study provides more room for the advancement of nuclear reactors, which is a key consideration in ensuring efficiency and safety of nuclear reactors.