Virtual Inertia as an Energy Dissipation Element for Haptic Interfaces

Adding virtual damping to dissipate energy has been a major tool for designing stable haptic interfaces in most passivity-based approaches. However, virtual damping is known to dissipate a limited amount of energy. It even generates energy during high-velocity interaction because of the digitization effect, such as zero-order hold and quantization. Therefore, no proper energy dissipation element has been available to stabilize the interaction when the virtual damping is no longer functioning. This paper investigates the possibility of using virtual inertia as a complementary energy dissipation element of virtual damping for stable haptic interfaces. This paper analyzes the energy behavior of virtual inertia in the digital domain and finds that it can dissipate energy even in higher velocity interactions, unlike digital damping and digital springs. Furthermore, this paper proposes a unidirectional virtual inertia that can dissipate a considerable amount of energy compared with the conventional virtual inertia by storing energy and disappearing without returning it to the system. Simulation and experimental studies using a PHANToM haptic interface proved the performance of the proposed method.