A tri-modal dielectric elastomer actuator integrating linear actuation, sound generation, and self-sensing capabilities

This paper presents a concept of multi-modal dielectric elastomer actuator (DEA) that leverages a single voltage input to concurrently work as linear actuator and loudspeaker, while also integrating self-sensing capabilities. Low-frequency linear actuation is obtained by inducing tangential stretching of the DEA membrane surface, whereas high-frequency sound generation is concurrently achieved through transverse structural vibrations of the DEA membrane surface. Multi-mode actuation is combined with a new self-sensing paradigm: measuring the current signal arising from the dynamic acoustic excitation and processing it in real-time with capacitance estimation algorithms, the actuator low-frequency displacement can be reconstructed with no need for additional transducers or dedicated probing signals. The performance of the proposed self-sensing approach is evaluated using complex multi-harmonic driving signals, with a focus on analyzing the correlation between capacitance estimates and the low-frequency stroke of the device. Concurrent self-sensing and multi-mode actuation are finally demonstrated in a number of application scenarios, in which the intensity/frequency of the DEA acoustic output is adjusted in closed-loop as a function of externally induced deformations, such as impacts with obstacles, or interactions with a user. The multi-modality paradigm pursued in this work paves the way to new application opportunities, such as multi-sensory user interfaces (e.g. audio-tactile buttons), or highly integrated sensor-actuator units able to sense their state during operation and provide feedback (e.g., acoustic signaling) accordingly.