Capacitive Tactile Sensing

A tactile-sensing method that infers contact force from the change in capacitance as pressure alters electrode spacing or a dielectric layer.

Capacitive tactile sensing is one of the main tactile-sensor principles, alongside piezoresistive, piezoelectric, magnetic, and vision-based sensing. The basic structure is two layers of electrodes sandwiching a compressible dielectric material: pressure changes the spacing or overlap area between the electrodes, which changes the capacitance, and readout circuitry converts that into pressure; arranging many such cells (taxels) into an array gives a full contact-pressure distribution. The advantages are high sensitivity, the ability to make sensors small, thin, and flexible, ease of covering large surfaces, and the ability to sense a hand approaching before contact; the drawbacks are susceptibility to parasitic capacitance and electromagnetic interference, temperature drift, and hysteresis introduced by the elastic dielectric layer. A well-known example is the large-area capacitive skin the Italian Institute of Technology (IIT) built for the iCub humanoid, with an improved version using a 3D fabric dielectric layer to reduce hysteresis.

ExampleA layer of capacitive tactile skin stuck to a collaborative robot arm’s casing sees a sudden capacitance change when a human hand touches or approaches a given region, and the controller immediately slows down or stops in response.

Also called

Capacitive Sensor, Capacitive Skin

Related

Tactile Sensor · Piezoresistive Tactile Sensing · Piezoelectric Tactile Sensing · Electronic Skin · Taxel · Proximity Sensor

Sources

A Flexible and Robust Large Scale Capacitive Tactile System for Robots (arXiv 1411.6837)
Tactile sensor - Wikipedia
Capacitive sensing - Wikipedia