Single-axis arm designed with an ultrasonic motor: Basic active/passive joint torque control

Fusaomi Nagata, Keisuke Ogiwara, Keigo Watanabe

Research output: Chapter in Book/Report/Conference proceedingChapter

1 Citation (Scopus)


This chapter highlights the active and passive joint torque control methods of a single-axis arm designed with an ultrasonic motor. Recently, many studies on assist robots have been conducted in which the development of a unique system is required to support aged persons, physically handicapped persons and/or carers. One of the representative systems is called the assist suit and is partially developed. The assist suit is a mechatronics device which can assist physical human actions. However, the current assist suit has a few problems with respect to cost, size, weight, longevity and so on. In this chapter, a fundamental study concerning a compact assist device is conducted. Where the assist device supports is one spot on the body such as a knee, an elbow or a shoulder. First of all, a simple single-axis arm is designed by using an ultrasonic motor which can generate high torque from a low velocity range. Then, a servo system with holding torque, a torque control system and a passive torque control system are proposed and their characteristics are evaluated. Here, the passive torque control includes a stiffness control, a compliance control and an impedance control.

Original languageEnglish
Title of host publicationMechatronics and Manufacturing Engineering
Subtitle of host publicationResearch and Development
PublisherElsevier Ltd
Number of pages15
ISBN (Print)9780857091505
Publication statusPublished - 2012


  • Assist device
  • Compliance control
  • Holding torque
  • Servo system
  • Single-axis arm
  • Torque control
  • Ultrasonic motor

ASJC Scopus subject areas

  • Engineering(all)


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