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Faridi Rad, Nafise

University of British Columbia

Haptic interfaces play a pivotal role in providing force feedback to users, enabling them to sense and interact with virtual environments. However, simulating these environments can introduce instability due to factors like sampling time, discretization, and time delays. Controllers are designed to maintain stability, often using the concept of passivity, which ensures stability without requiring detailed knowledge of the user's properties. One emerging tool for haptic controller design is the Time-Domain Passivity Approach (TDPA), which is less conservative and induces fewer changes in feedback force than other conventional passivity controllers. However, the discontinuous operation of TDPA can lead to abrupt force changes, affecting user experience. This thesis addresses these challenges in both single and multi-degree-of-freedom (DOF) haptic interfaces. In response to the issues with TDPA, this thesis presents three key contributions. First, an Adaptive Energy Reference TDPA is proposed, which smooths the operation of TDPA by creating an adaptive reference in each push-and-release interaction in the virtual environment. Second, this approach is extended to multi-DOF haptic systems, considering both force direction and magnitude to maintain transparency by solving an optimization problem. The first and second contributions of this thesis are rooted in the premise that the parameters characterizing the haptic interface remain constant throughout a single interaction, but they can change between interactions. This assumption is reconsidered in the third contribution. Addressing highly variable haptic interfaces, even within a single interaction, a novel solution termed the Predictive Passivity Filter is introduced. Based on the prediction of the current passivity level in the haptic interface, the predictive passivity filter forms gradual adjustments of the force feedback. The proposed methods are validated through experiments conducted on the PHANToM OMNI haptic device in virtual environments. The results demonstrate the effectiveness of the approaches in reducing abrupt force changes and preserving transparency, thus enhancing the user's experience with haptic interfaces.

Text

2025-04-30

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/88094

Mechanical Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/