Experimental Investigation Into Particle Dynamics Induced by Steady-State Structure-Borne Traveling Waves

Abstract Structural wave propulsion is found in nature as a mode of locomotion both on land and in the sea. Wave-driven motion has been investigated as a method of propelling nature-inspired robots as well as transporting materials in manufacturing systems. Among the different ways to generate steady-state structure-borne traveling waves (SBTW), the two-mode excitation has been gaining more attention due to its flexibility and robustness. Two-mode excitation generates a traveling wave by exciting a complex operating deflection shape (ODS) and tuning the complexity to produce a pure traveling wave. This complex ODS is generated by exciting with two actuators at the same frequency but with a phase offset. Each actuator generates a standing wave which results from real ODS. The phase offset between these ODS introduces the complexity to the overall waveform and is tuned to produce steady-state SBTW in a finite structure. In SBTW generated using two-mode excitation, the frequency will determine the dominant modes in the wave and the shape of the active area on the plate’s surface, while the phase offset primarily influences the quality of the SBTW. Unlike active sink techniques, a control effort is not required for the generation of SBTW with the two-mode excitation, allowing for the control effort to be entirely focused on particle motion. This makes the technique well-suited for particle motion applications. While SBTW generated by two-mode excitation has shown promise for wave-driven propulsion of the structure itself, particle motion driven by such waves has yet to be examined. This paper experimentally investigates wave-driven particle motion, focusing on tracking particle dynamics and correlating it to the velocity field of 2D SBTW. For this purpose, an experimental setup that utilizes GoPro cameras is developed and integrated with real-time image processing techniques. The developed setup is capable of monitoring a particle moving on an excited plate, tracking its trajectory, and calculating approximate velocities and accelerations. The study employs a range of techniques for particle tracking that are applied using Python’s OpenCV library. Color space conversion and smoothing filters are implemented to manage reflections on surfaces. Techniques to smooth lighting irregularities on the plate ensured consistent visibility of the particle. Additionally, methods to enhance image resolution and predictive tracking facilitated the accurate monitoring of particle movement. Using the developed setup, the effectiveness of SBTW in moving particles located at various sections of the plate is evaluated. This procedure serves as the first step in developing robust methods for precision wave-driven motion applications.