Rendering high-fidelity vibrotactile feedback on a plate via optimization of actuator driving signals

In recent years, many touchscreen devices have tried to implement vibrotactile feedback to improve the quality of interaction with users. While mobile devices with a small touchscreen have successfully implemented vibrotactile feedback, large touchscreens have not. Large touchscreens typically have complex vibration mode shapes that complicate the vibration control, and they can radiate considerable acoustic noise as they vibrate. Recent demand for high-fidelity vibrotactile feedback and quiescent electronic devices highlights these problems. This study presents a method to render high-fidelity vibrotactile feedback on a large plate via optimization of actuator driving signals. To optimize the driving signals, measured frequency response functions between the driving signals and the vibration response on the touch surface have been incorporated. The driving signals were optimized to minimize the root-mean-square surface vibration velocity while rendering specific vibration patterns on desired positions. We carried out experimental validation on a simplified touch surface composed of an acrylic plate and nine voice coil actuators. The results were compared with previous studies in terms of the fidelity of vibration and the effect of the optimization. This work provides a valuable technique for haptic designers who endeavor to portray a subtle sense of touch on touchscreens.