Altering Perceived Softness of Real Rigid Objects by Restricting Fingerpad Deformation

Title of the Paper

Using Fingerpad Deformation Restriction to Alter the Perception of Softness in Rigid Objects

Paper Information

• Field of Study: Human-Computer Interaction, Haptic Devices, Virtual Reality
• Keywords: Haptic illusion, compliance, wearable haptic devices, tactile interaction, virtual reality, augmented reality, softness, rigidity

Research Background and Problem

• Identified Challenges:

  • Most wearable haptic devices provide virtual softness experiences by covering the fingerpad, which limits users' ability to perceive the texture of real objects.
  • Current methods require instrumenting objects themselves, altering their properties to achieve changes in perceived softness.
  • Investigating how to change the perception of softness in rigid objects without instrumenting the objects.

• Significance:

  • Perception of softness or hardness is a key dimension in tactile interaction, influencing users' recognition and manipulation of objects.
  • Achieving changes in perceived softness without altering the object's intrinsic properties can enhance interaction experiences in virtual reality (VR) and augmented reality (AR).

• Research Motivation and Related Work:

  • Existing studies simulate softness through visual or vibrational methods but fail to provide sufficient tactile realism.
  • This study aims to explore an innovative approach that induces changes in perceived softness by restricting fingerpad deformation, without physically modifying objects (e.g., buttons, VR props).

Solution

• Method and Principle:

  • A haptic device was designed to gently compress the sides of the fingerpad using a framed structure, restricting lateral deformation of the fingerpad and broadening the tactile contact area.
  • This restriction makes the contact area of the fingerpad on rigid surfaces resemble that on soft surfaces, thereby inducing a perception of softness.

• Innovative Features:

  • Unlike traditional devices, this device creates a sense of softness while preserving the ability of the central part of the fingerpad to freely contact the object, allowing users to perceive the actual texture of the object.
  • Achieves changes in perceived softness without modifying the object itself.

• Implementation Steps and Key Technologies:

  • Apply slight lateral pressure using a hollow frame to restrict fingerpad deformation.
  • Design a portable device incorporating a 3D-printed frame, miniature motors, a Bluetooth module, and force sensors.
  • Introduce perception adjustment based on PID control to ensure consistent force feedback from the device.
  • Validate the effectiveness of the device through psychophysical studies and user experience research.

Research Results

• Specific Findings:

  • In psychophysical experiments, the device reduced the perceived hardness of rigid materials with Shore A hardness ranging from 50A to 90A to an average of approximately 40A.
  • In user experience studies, participants generally agreed that the device enhanced the tactile realism in interactive applications.

• Experiments and Evaluation:

  • The first experiment verified that the device increased the perception of softness when touching rigid objects, with data showing significant enhancement of softness even for harder objects.
  • In the second experiment, participants interacted with two application scenarios (VR shopping, game controllers), with most preferring the interaction method using the device, citing improved tactile feedback realism.

• Comparison with Existing Methods:

  • Does not require object modification; simpler technical implementation with more significant effects compared to instrumented or vibration-based simulation methods.
  • Applicable to everyday objects and 3D-printed components, offering high versatility.

• Limitations and Future Directions:

  • The device is only suitable for objects or protrusions smaller than the fingerpad area and is not ideal for large surface operations.
  • Current softness perception switching is limited to a simple "on/off" mode; future work could explore adjustable degrees of softness.
  • In some practical applications, the device still faces limitations in size and motor vibrations, but its design may inspire further optimization in future research.