Leveraging the Open-Loop Stiffness of Pneumatic Actuators to Enable High-Stiffness Surface Simulation in Impedance-Type Haptic Interfaces

Abstract

The stable simulation of high-stiffness surfaces remains a challenge in impedance-type haptic simulation of mechanical environments. In this paper, the authors propose an approach to achieving a stable, high-stiffness surface in a haptic interface by leveraging the open-loop properties of pneumatic actuators. By utilizing the open-loop component of actuator stiffness as the primary component of stiffness simulation in a haptic interface, the system requires a comparatively small component of simulated stiffness from closed-loop control of the actuator. A stability analysis is presented indicating that this approach enhances significantly the range of passivity of haptically simulated high-stiffness surfaces. Experimental results both with and without a human operator are presented that demonstrate the effectiveness of the approach.