Kinematic modelling and motion analysis of a humanoid torso mechanism

Matteo Russo, Marco Ceccarelli, Daniele Cafolla

Research output: Contribution to journalArticlepeer-review


This paper introduces a novel kinematic model for a tendon‐driven compliant torso mechanism for humanoid robots, which describes the complex behaviour of a system characterised by the interaction of a complex compliant element with rigid bodies and actuation tendons. Inspired by a human spine, the proposed mechanism is based on a flexible backbone whose shape is controlled by two pairs of antagonistic tendons. First, the structure is analysed to identify the main modes of motion. Then, a constant curvature kinematic model is extended to describe the behaviour of the torso mechanism under examination, which includes axial elongation/compression and tor-sion in addition to the main bending motion. A linearised stiffness model is also formulated to estimate the static response of the backbone. The novel model is used to evaluate the workspace of an example mechanical design, and then it is mapped onto a controller to validate the results with an experimental test on a prototype. By replacing a previous approximated model calibrated on experimental data, this kinematic model improves the accuracy and efficiency of the torso mechanism and enables the performance evaluation of the robot over the reachable workspace, to ensure that the tendon‐driven architecture operates within its wrench‐closure workspace.

Original languageEnglish
Article number2607
JournalApplied Sciences (Switzerland)
Issue number6
Publication statusPublished - Mar 2 2021
Externally publishedYes


  • Assistive robotics
  • Cable‐driven robots
  • Compliant mechanisms
  • Humanoid robotics
  • Kinematics
  • Mechanism design
  • Motion analysis
  • Service robotics
  • Underactuated mechanisms
  • Work-space

ASJC Scopus subject areas

  • Materials Science(all)
  • Instrumentation
  • Engineering(all)
  • Process Chemistry and Technology
  • Computer Science Applications
  • Fluid Flow and Transfer Processes


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