Triaxis Static Force Sensing for Langevin-Type Ultrasonic Tools Using Lead-Zirconate-Titanate Ceramic Rings

A novel triaxis static force sensor that uses lead zirconate titanate (PZT) ceramic rings is proposed. The actuator ring is driven at the resonance frequency of the thickness vibration mode to generate ultrasonic waves in the detector rings. The electric potential between the top and bottom surfaces of the detector ring due to the direct piezoelectric effect is measured. The sensing mechanism is based on the variation of the compliance coefficient with the applied force. The bolt-clamped Langevin transducer is the most widely used ultrasonic actuator in ultrasonic machining. The proposed design composed of two PZT ceramic rings imparts triaxis static force sensing capability to the Langevin transducer without the use of external components. The statics model, relationship between stress and the compliance coefficient, and decoupling matrix were derived to estimate the forces on the tool tip based on the voltages at the electrodes on the detector ring. The mean differences between the calculated and experimental results in terms of
${F} _{\textbf {x}}$
,
${F} _{\textbf {y}}$
, and
${F} _{\textbf {z}}$
were 1.92%, 2.54%, and 4.26%, respectively, the full range of ±150 N. The experiments were conducted using different weights and a multiaxis force reference sensor.