Advancements in parallel actuation: modeling, design, and applications

Parallel actuation is both a solution and a challenge. Compared to serially actuated systems, it offers significant advantages in speed, accuracy, and efficiency. These improvements arise from transmitting motion through multiple mechanical branches simultaneously. However, this same characteristic also introduces new challenges at two distinct levels. First, the usable work-space is often significantly reduced, leading to designs that are highly task-specific. Second, the complexity of modeling increases, which has historically hindered the widespread adoption of optimal control algorithms compared to serial architectures. Furthermore, modern demands for increased robot compliance — to enhance adaptability, energy efficiency, and safety — stand in contrast to the inherently rigid nature of traditional parallel robots.

This work addresses these challenges through various approaches. In the first part, belt-driven designs that lie at the intersection of serial and parallel architectures are explored. It is demonstrated that such systems enable high-speed movements within large work-spaces, thereby applying trajectory optimization methods. Additionally, the possibility to extend the usable work-space of parallel kinematic machines is exemplified. The second part focuses on compliant parallel actuation, showing that stiffness control can be achieved with a minimal number of actuators. It also introduces a novel concept combining soft-shell actuation with parallel linkages. The third part investigates various dynamic modeling techniques for parallel kinematic machines and provides a comparative analysis of their suitability for trajectory optimization.