Tendon-driven (TD) hyper-redundant manipulators (HRMs) enable inspection in confined and hazardous environments by relocating the robot's actuators outside the workspace. In a fully-actuated architecture, however, tendon elasticity, friction, hysteresis, and mechanical play generate slack that a constant pre-tensioning system cannot compensate for during operation. This dissertation presents the design and experimental testing of an active-tensioning (AT) system for a fully-actuated TD HRM, in which one motor drives an antagonistic pair of tendons per joint. The AT concept simultaneously applies controllable tension only to the loose actuation tendon of each pair, using a single additional motor. Based on foundational work on a TD HRM, the robot's inherited static model is updated according to the AT concept, and compared with the original pre-tensioning solution through simulation. The concept is then integrated into a revised actuation box that supports eight joints. Additionally, a CAD-based virtual prototype of the sixteen-tendon routing, two per joint, ensures a collision-free layout before manufacture. Experimental validation is conducted on the five-joint polymeric prototype (LORY-5JP). Three campaigns are reported: static tests with the arm in a fixed straight configuration, motion tests under reconfiguration between prescribed poses, and a complementary stiffness campaign on the same arm, only summarised here. The characterisation is limited to a five-joint polymeric arm, while extension to the eight-joint layout and to a metallic version of the arm is left to future work. In parallel with the main dissertation's scope, the author contributed to the Interreg Central Europe project Small and Medium-sized Enterprises Ready for the Future (SMERF), developing a support framework for small and medium-sized enterprises in the involved regions, and collaborated with the German Aerospace Centre (DLR) on an active palm designed to improve the multi-object grasping capability of a robotic hand.
Design and Testing of an Active-Tensioning System for a Hyper-Redundant Tendon-Driven Manipulator
MANARA, FEDERICO
2026-11-05
Abstract
Tendon-driven (TD) hyper-redundant manipulators (HRMs) enable inspection in confined and hazardous environments by relocating the robot's actuators outside the workspace. In a fully-actuated architecture, however, tendon elasticity, friction, hysteresis, and mechanical play generate slack that a constant pre-tensioning system cannot compensate for during operation. This dissertation presents the design and experimental testing of an active-tensioning (AT) system for a fully-actuated TD HRM, in which one motor drives an antagonistic pair of tendons per joint. The AT concept simultaneously applies controllable tension only to the loose actuation tendon of each pair, using a single additional motor. Based on foundational work on a TD HRM, the robot's inherited static model is updated according to the AT concept, and compared with the original pre-tensioning solution through simulation. The concept is then integrated into a revised actuation box that supports eight joints. Additionally, a CAD-based virtual prototype of the sixteen-tendon routing, two per joint, ensures a collision-free layout before manufacture. Experimental validation is conducted on the five-joint polymeric prototype (LORY-5JP). Three campaigns are reported: static tests with the arm in a fixed straight configuration, motion tests under reconfiguration between prescribed poses, and a complementary stiffness campaign on the same arm, only summarised here. The characterisation is limited to a five-joint polymeric arm, while extension to the eight-joint layout and to a metallic version of the arm is left to future work. In parallel with the main dissertation's scope, the author contributed to the Interreg Central Europe project Small and Medium-sized Enterprises Ready for the Future (SMERF), developing a support framework for small and medium-sized enterprises in the involved regions, and collaborated with the German Aerospace Centre (DLR) on an active palm designed to improve the multi-object grasping capability of a robotic hand.
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