Novel Supernumerary Robotic Limb based on Variable Stiffness Actuators for Hemiplegic Patients Assistance

Student thesis: Master's Thesis


Loss in upper extremity motor control and function is an unremitting symptom in post-stroke patients. This would impose hardships in accomplishing their Daily-Life-Activities. Supernumerary-Robotic-Limbs (SRLs) were introduced as a solution to regain the lost degrees-of-freedom (DoFs) by introducing an independent new limb. The actuation systems in SRL can be categorized into rigid and soft actuators. Soft Actuators have proven advantageous over their rigid counterparts through their intrinsic safety, cost, and energy efficiency. However, they suffer from low stiffness, which jeopardizes their accuracy. Variable-Stiffness-Actuators (VSAs) are newly developed technologies that have been proven to ensure both accuracy and safety. In this thesis, we introduce the novel Supernumerary-Robotic-Limb based on Variable-Stiffness-Actuators. Based on our knowledge, the proposed proof-of-concept SRL is the first which utilizes Variable Stiffness Actuators. The developed SRL would assist post-stroke patients in Bi-manual tasks, e.g., eating-with-fork-and-knife. The modeling, design, and realization of the system are illustrated. The proposed SRL was evaluated and verified for its accuracy via predefined trajectories. The safety was verified by utilizing the momentum observer for collision detection, and several post-collision reaction strategies were evaluated through the Soft-Tissue-Injury Test. The assistance process is qualitatively verified through a standard user satisfaction questionnaire.
Date of AwardJul 2022
Original languageAmerican English


  • Supernumerary-Robotic-Limbs
  • Variable-Stiffness-Joints
  • Post-Stroke Assistive Devices
  • Human-Robot Interaction.

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