2[1]Ueha S,Tomikawa Y.Ultrasonic motors theory and applications.Oxford Science Publications,1993.
3[2]Akiyama Y.Present state of ultrasonic motors in Japan.JEE,1987,24(245):76～80.
4[4]Ueha S.Present status of ultrasonic motors.IEEE Ultrasonic Symposium,1989,749～753.
5[5]Kusakabe C,et al.Effect of pressing force applied to a rotor on disk type ultrasonic motor driven by self oscillation.Jpn.J.Appl.Phys,1998,37(5B):2966～2969.
6[6]Backes P G,et al.Multifunction Automated Crawling System.Proc.of 1997 IEEE Int.Conf.on Robotics and Automation,1997,(1):335～340.
