Robust Resonant Frequency-Based Contact Detection With Applications in Robotic Reaching and Grasping

This paper presents a method for detecting contact by tracking a compliant structure's resonant frequency, which increases with external contact. The approach uses an inexpensive accelerometer mounted on or embedded inside the structure, and a phase locked loop circuit and actuator to oscillate the structure at its resonant frequency. This approach is applied to a robotic finger, and two contact detection metrics are compared. The first and best-performing metric detects changes in the frequency of oscillation. The second metric measures changes in the amplitude of the oscillation and detects contact based on amplitude attenuation. The frequency-based method was shown to be approximately three times as sensitive as the amplitude metric, capable of detecting contacts at between 0.03 and 1.65 N, depending on the contact location, approach velocity, and finger stiffness, while the amplitude-based metric detected contacts at between 0.1 and 8 N. The resonant frequency-based approach to contact detection resulted in reliable contact detection anywhere on the finger, including the finger pads, back of the finger, and even out of plane on the side of the finger.