Autonomous electronic devices and sensors are essential to reduce expensive maintenance, increasing job security and reliability, avoiding battery replacements and wired systems. Industrial systems and civil structures vibrate dissipating an important amount of energy that can be harvested to power small devices. This work proposes a tunable multi-arm electromagnetic pendulum for ultra-low frequency vibrations energy harvesting as the significant evolution of a previous harvester. The paper starts from conceptual design, includes a detailed multiphysics dynamic simulation, presents the prototype development and experimental validation. Systematic experimental tests investigated different pendulum configurations in terms of magnetic spring stiffness and confirmed both the ultra-low frequency response (from 2 to 10 Hz), as predicted by the dynamic simulation, and the good voltage and power outputs.

The work focuses on the design and prototyping of a novel end-effector for a collaborative robotic arm allowing to grab and drag industrial packages without lifting them. The proposed solution consists of a passive 3D-printed end-effector manufactured using carbon fibre reinforced Onyx material. Thanks to the entirely passive mechanical actuation that exploits the compliance of the main chassis, this end-effector features a simple, scalable, and inexpensive structure. This lightweight end-effector is specifically designed for small and low payload collaborative robotic arms. Specifically, the proposed end-effector includes three main parts. First, a thin blade, with the main function of separating boxes that are close to each other. Second, a rocker arm - rod mechanism, which allows an opposable bracket to be moved in order to grab the correspondent package. This is proportionally and passively actuated by the contact pressure between the package, during its grip, and a paddle (third part), which is composed of a flat leverage and three flexural springs to counterbalance the pushing force. This paddle and the main body of the gripper were designed as a single part exploiting 3D printing manufacturing capabilities. Moreover, we implemented a Simscape dynamic model that predicts the functionality of the end-effector during standard operations. The work shows how to design, develop and validate a new low cost, passive end-effector mainly oriented to collaborative robots. The final prototype demonstrates its entire functionality, and proves fabricability through 3D printing, thus minimizing production costs, weight, and time.