In this study a novel servo speed control system for travelling-wave ultrasonic motor (TWUSM) has been presented. A drive system has been built based on two-phase high-frequency inverter using mechanical resonant frequency of the ultrasonic motor. The TMS320F243 digital signal processor (DSP) is adapted to ultrasonic motor drive system. The speed control of ultrasonic motor has been implemented with driving frequency in the range of 41.3-43.3 kHz. The improved speed characteristics realised by the proposed drive and control system have been demonstrated and validated by experiments. (C) 2003 Elsevier B.V. All rights reserved.