Towards a multi-DOF passive balancing mechanism for upper limbs

Zhuoqi Cheng, Shaohui Foong, Defeng Sun, U. Xuan Tan

Research output: Chapter in book / Conference proceedingConference article published in proceeding or bookAcademic researchpeer-review

18 Citations (Scopus)


Gravity balancing has great significance in many rehabilitation applications and one example is in minimizing the resistance of lifting a patient's upper limb due to its own weight. As compared to commonly used active method in exoskeleton, passive weight compensation offers many other advantages such as elimination of motors which reduces the overall load acting on the patient. However, the torque about each joint due to the weight of the upper and fore arm is dependent on the orientation and location of each other, which makes it a challenge to compensate. Hence, this paper proposes and develop a passive method to compensate the torques on each joint. The proposed design includes a decoupling mechanism for isolating the torsional effect between various linkages and a realizable torsional compliant beam which can provide a specific torsional stiffness function to compensate the torque due to the arm's weight. In place of the usual expensive zero-length spring as the solution, an algorithm that generates the appropriate compliant beam design is also presented in this paper. The end result of the manipulator arm is a reduced required joint torque for gravity compensation using only passive means. A two-DOF prototype, with easy possible extension of additional DOF, has been built, and experiments are performed to illustrate, verify and quantify the effectiveness of the proposed method.

Original languageEnglish
Title of host publicationProceedings of the IEEE/RAS-EMBS International Conference on Rehabilitation Robotics
Subtitle of host publicationEnabling Technology Festival, ICORR 2015
EditorsDavid Braun, Haoyong Yu, Domenico Campolo
PublisherIEEE Computer Society
Number of pages6
ISBN (Electronic)9781479918072
Publication statusPublished - 28 Sept 2015
Externally publishedYes
Event14th IEEE/RAS-EMBS International Conference on Rehabilitation Robotics, ICORR 2015 - Singapore, Singapore
Duration: 11 Aug 201514 Aug 2015

Publication series

NameIEEE International Conference on Rehabilitation Robotics
ISSN (Print)1945-7898
ISSN (Electronic)1945-7901


Conference14th IEEE/RAS-EMBS International Conference on Rehabilitation Robotics, ICORR 2015

ASJC Scopus subject areas

  • Control and Systems Engineering
  • Rehabilitation
  • Electrical and Electronic Engineering


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