Implementing Virtual Walls and High-Frequency Haptic Taps on a 3 Degree-of-Freedom Wrist Exoskeleton
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Haptic interactions have traditionally been rendered using desktop devices that rely on stylus-based interactions with a virtual environment. Less explored is the potential to render salient kinesthetic and cutaneous haptic interactions via exoskeletonbased devices. To date, developers have used closed-loop control to create kinesthetic forbidden regions of the workshop that the user cannot enter, or simulating hard stops on the exoskeleton in software, usually based on joint range of motion limitations. Cutaneous cues such as vibration have typically be rendered in tandem to the kinesthetic feedback, requiring the incorporation of a second set of high bandwidth actuators to overlay vibraiton on the primary kinesthetic cues. This approach increases system cost an complexity. In this work, we present methods for realizing high-fidelity kinesthetic feedback in a wrist-based exoskeleton device, the MAHI OpenWrist. We also present a method for conveying high-frequency “taps” or vibrations through the exoskeleton, leveraging the gap between exoskeleton and actuator bandwidths to reduce wrist motion on cue application and provide high-frequency haptic cues without need for additional actuation. Our open-architecture virtual wall generation system was developed and implemented on the OpenWrist device. These virtual walls are defined with multiple wall parameters including location, surface friction coefficient, normal restoring force, and normal damping all configurable to generate unique haptic effects. The user experience with the rendered virtual walls is enhanced using the traditional God Object rendering technique. These haptic rendering methods extend the capabilities of the OpenWrist device, and can be extended to other exoskeleton type haptic feedback systems.
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Timpe, Nick Kendrick. "Implementing Virtual Walls and High-Frequency Haptic Taps on a 3 Degree-of-Freedom Wrist Exoskeleton." (2023) Master’s Thesis, Rice University. https://hdl.handle.net/1911/115168.