@Article GS06,
author = "Giraud, Fr\'ed\'eric and Semail, Betty",
title = "A torque estimator for a traveling wave ultrasonic motor - application to an active claw",
journal = "IEEE Transaction on Ultrasonics, Ferroelectrics and Frequency Control",
number = "8",
volume = "53",
pages = "1468--1477",
year = "2006",
}