Optimization of Mono- and Bi-Articular Parallel Elastic Elements for a Robotic Arm Performing a Pick-and-Place Task

Actuation concepts such as Series Elastic Actuation (SEA), Parallel Elastic Actuation (PEA), and Biarticular Actuation (BA), which introduce elastic elements into the structure, have the potential to reduce the electrical energy consumption of a robot. This letter presents an optimization of the arrangement of springs for a 3 degrees of freedom robotic arm, with the aim of decreasing the electrical energy consumption for a given pick-and-place task. Through simulations and experimental validation, we show that the optimal configuration in terms of electrical energy consumption and complexity consists of rigid actuation on joint 1 and PEAs on joints 2 and 3. With this configuration, root mean square (RMS) and peak load torques for a specific pick-and-place task can be reduced respectively by up to 43% and 44% for joint 2, and by 15% and 21% for joint 3 compared to the configuration without springs.