HaptArm

Mixed-reality | Tangible Interaction | Wearable Device
Individual Project (Mar. 2025 - Oct. 2025)

HaptArm is a wearable device designed for XR environments that delivers haptic feedback to enhance affordance and communicate tactile messages—such as the sensation of pushing a rusted handle. The device is powered by two field-oriented controlled (FOC) BLDC motors, providing both degrees of freedom (DOF) and customizable haptic patterns.

Serving as an input interface, HAPTIControl bridges the gap between physical and virtual experiences, making digital interactions more tangible. The design also draws on the concept of Force Image Schema (FIS) to inform the design of metaphorical haptic sensations, enriching the expressive potential of touch in extended reality contexts.

Introduction - XR Haptics

Tactile feelings are a screen for our body to ‘see’ the world and understand meanings. I am especially intrigued by how haptic feedback has become an increasingly important part of tangible and embodied interaction. The design references show that actuated or simple systems can simulate nuanced physical sensations.

Yet, most current designs stop at replicating physical resistance or texture without fully exploring how actuation could encode meaning, guide behaviour, or create new affordances. Therefore, I arrive at this research question.

Research Question

How can haptic feedback in tangible interaction design based on actuated technology enhance users' perception of affordance and intuitive interaction of controls in virtual environment?

Controls: Button, switch, handle ...

Key Concepts

Cybernetic Control Loop

Actuated technology today is no longer just hidden in the mechanics of industry but something to motivate users. A cybernetic control loop, or closed-loop is an appropriate technical solution, so that the input and output, sensor and actuator, are self-calibrating for the best performance.

Force Image Schema

FIS is particularly relevant here. Evidence shows that FIS can be used both physically and metaphorically in tangible interaction design to communicate messages, mimic environments, and direct action.

This concept is useful for me because it allows the development of distinct haptic patterns that communicate and differentiate user interactions across virtual controls.

Force image schemas can always be useful design aids when representing or mediating real physical forces through the user interface (e.g. control rooms in factories and chemical plants). The type of instantiation may differ: from providing physical force feedback to a visualization of movement trajectories.

- http://dx.doi.org/10.1145/2677199.2680553

Brainstorm

I decided to develop the third concept for its potential to actively exert forces on the hand during different interactions, thereby enhancing affordance.

System Diagram

Developed from Concept 3, my design aims to provide user with haptic feedback using two FOC motors to maximize ways of controls in virtual scenarios.

Mechanics

Prototype 1.0

This setup with GT2 pulley, MT6701 magnetic encoder and 2804 FOC motor proved the validation of the interactivity and its function to provide movement and haptic feedback.

Selection of Modes

Strong endpoint on both sides

On-Off switch

Return-to-center

Prototype 2.0

Circuit Diagram

Developed from the first prototype, the second version features a simplified electronic system. I specifically chose the M5Stack RollerCAN as the FOC motor module because it is open-source, flexible, and provides stable angle and torque control.

Codes & Haptic Feedback Based on Scenario

Final Outcome

Reflection

Although the prototype has been validated and tested by myself, further development would involve testing with a wider range of users to explore how the design creates affordances and guides interaction.

Citation

scottbez1. “DIY haptic input knob: BLDC motor + round LCD.” Youtube, 11 March 2022, https://www.youtube.com/watch?v=ip641WmY4pA. Accessed 26 November 2024.

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