A Novel Pneudraulic Actuation Method to Enhance Soft Robot Control

Modern industrial and medical applications require soft actuators with practical actuation methods, capable of precision control and high-speed performance. Within the realm of medical robotics, precision and speed imply less complications and reduced operational times. Soft fluidic actuators (SFAs) are promising candidates to replace the current rigid endoscopes due to their mechanical compliance, which offers safer human-robot interaction. However, the most common techniques used to operate SFAs, pneumatics, and hydraulics present limitations that affect their performance. To reduce manufacturing complexity, enhance response time, improve control precision, and augment the usability of SFAs, we propose a Pneudraulic Actuation (PHA) system that, for the first time, combines a pneumatic and hydraulic circuit in series. To examine this proposal, a comparative assessment of the proposed actuation technique with the common techniques was carried out, in terms of bending performance and generation of audible noise level during functioning. The analysis provides insights into the performance of various fluidic actuation methods for SFAs, highlighting significant effects related to fluid-structure interactions and the presence of trapped air. Thereafter, a comparative assessment of different fluidic circuits is performed, illustrating how tubing length, inner and outer diameter, as well as the amount of different fluidic medium impact the dynamic behavior of the system, amplifying the importance of fluid mechanics for design optimization. Furthermore, we propose a model-based control strategy that solely focuses on fluid dynamics, utilizing the hydraulic-electric analogy and the resistor-inductor-capacitor circuit theory. Our PID controller improved actuation speed by 52.63% and reduced audible noise by 17.17%.