Effects of Physical Hardness on the Perception of Rendered Stiffness in an Encountered-Type Haptic Display

Area of Science:

• Haptics and Human-Computer Interaction
• Robotics and Mechanical Engineering

Background:

• Rendering hard surfaces and free space simultaneously remains a significant challenge for current haptic devices.
• Previous work introduced an encountered-type haptic display system, demonstrating improvements over traditional methods by attaching a variable hardness plate to the device's end-effector.

Purpose of the Study:

• To evaluate how altering the end-effector's hardness influences the masking of device stiffness.
• To assess the impact of end-effector hardness on user perception during haptic interactions.

Main Methods:

• A human subject experiment was conducted using a haptic display with an interchangeable end-effector plate.
• Participants interacted with the system using an untethered stylus, experiencing varying degrees of end-effector hardness and device-rendered stiffness.

Main Results:

• Users found it difficult to perceive changes in rendered stiffness when the end-effector was made of a hard material.
• Conversely, stiffness changes were readily distinguishable when the end-effector was composed of a soft material.

Conclusions:

• The findings suggest that a hard end-effector material can effectively mask the inherent stiffness of the haptic device.
• This approach shows potential for overcoming limitations in rendering hard surfaces with existing haptic technology.