*Article* **A New Approach of Soft Joint Based on a Cable-Driven Parallel Mechanism for Robotic Applications**

**Luis Nagua \*,†, Carlos Relaño †, Concepción A. Monje and Carlos Balaguer**

Robotics Lab of the Carlos III University of Madrid, Avda de la Universidad 30, Leganés, 28911 Madrid, Spain; crelgib@gmail.com (C.R.); cmonje@ing.uc3m.es (C.A.M.); balaguer@ing.uc3m.es (C.B.)

**\*** Correspondence: lnagua@ing.uc3m.es; Tel.: +34-674859239

† These authors contributed equally to this work.

**Abstract:** A soft joint has been designed and modeled to perform as a robotic joint with 2 Degrees of Freedom (DOF) (inclination and orientation). The joint actuation is based on a Cable-Driven Parallel Mechanism (CDPM). To study its performance in more detail, a test platform has been developed using components that can be manufactured in a 3D printer using a flexible polymer. The mathematical model of the kinematics of the soft joint is developed, which includes a blocking mechanism and the morphology workspace. The model is validated using Finite Element Analysis (FEA) (CAD software). Experimental tests are performed to validate the inverse kinematic model and to show the potential use of the prototype in robotic platforms such as manipulators and humanoid robots.

**Keywords:** soft robotics; continuum mechanisms; modeling of complex systems; kinematic model of soft robots
