The T-Blep: A Soft Optical Sensor for Stiffness and Contact Force Measurement.

Area of Science:

• Robotics
• Materials Science
• Sensor Technology

Background:

• Accurate material property characterization is crucial for robotic manipulation and material science research.
• Existing tactile sensors often lack the versatility to measure both stiffness and force effectively.
• Soft sensors offer advantages in compliance and safety for human-robot interaction.

Purpose of the Study:

• To present the Tactile Blep (T-Blep), a novel optical soft sensor capable of measuring material stiffness and force.
• To demonstrate the T-Blep's ability to switch between stiffness and force detection modes.
• To evaluate the performance and accuracy of the T-Blep in various experimental conditions.

Main Methods:

• Development of an optical soft sensor (T-Blep) with an inflatable membrane and internal optical elements.
• Implementation of a pressure modulation technique to switch between stiffness and force detection modes.
• Utilizing simulations and experimental validation for force and stiffness measurements.

Main Results:

• Simulations showed a 1 mm-thick membrane can differentiate between extra-soft, soft, and rigid targets.
• Force detection experiments demonstrated a sixfold increase in detectable force range with varying internal pressure (10-40 kPa), achieving a peak force of 5.43 N and sensitivity up to 331 mV/N.
• A piecewise force reconstruction method achieved high accuracy (R2>0.994), and stiffness detection yielded a classification accuracy of 97%.

Conclusions:

• The Tactile Blep (T-Blep) is a versatile optical soft sensor for accurate material stiffness and force measurement.
• The sensor's performance, including sensitivity and force range, can be tuned by adjusting internal pressure.
• The T-Blep shows significant potential for applications requiring precise material characterization in soft robotics and beyond.