A Handheld Stiffness Display with a Programmable Spring and Electrostatic Clutches for Haptic Interaction in Virtual Reality.

Handheld haptic devices often face challenges in delivering stiffness feedback with both high force output and good backdrivability, especially under practical constraints on power consumption, size, and weight. These difficulties stem from the inherent performance limitations of conventional actuation mechanisms. To address this issue, we propose a lightweight, low-power handheld device that provides wide-range stiffness feedback through a novel dual actuation design composed of two key components. A programmable spring (PS), implemented via an adjustable lever arm, enables tunable physical stiffness. Two electrostatic clutches (ECs) are integrated to compensate for the inherent limitations of PS-based interactions in stiffness display range, rendered object size, and free motion capability. The feedback force arises passively from the reaction of the PS and ECs to user input, effectively lowering both power consumption and actuator torque demands. A fully integrated prototype was developed, incorporating wireless communication, control, and power modules. The results of the evaluation experiments and user studies demonstrate that the device effectively renders stiffness across the full range, from free motion to full rigidity, and delivers more realistic elastic feedback compared to conventional electric motor-based systems.