Real-Time, FEM-Based Control of a Soft Actuator With Force Sensing for Gastric Contraction Simulation

This article presents a force-controlled soft ring actuator technology for enhanced biomimetic fidelity in gastric simulation. Previous robotic gastric simulators, including our cross-sectional actuator (RiSPA) for pyloric antrum simulation, have achieved basic peristaltic motion but operated either with simplified control models or in open-loop configurations, lacking critical force sensing capabilities. We address these limitations through two key contributions: Integration of a real-time force sensing capability into the RiSPA platform, a first for gastric simulation systems, and development of a real-time finite element method control system that provides better fidelity compared to simplified models and enhanced physical interpretability versus machine learning approaches. We propose a hybrid position-force control methodology that dynamically switches between position tracking (when food bolus disappears) and force regulation (when food bolus exists), aligned with the physiological force profile from human in vivo measurements. Experimental validation demonstrates that our system achieves position tracking with 0 mm steady-state error and force regulation with only 0.06 N steady-state error, outperforming conventional PID approaches with a 37% reduction in force regulation overshoot. Testing with three distinct food bolus types (agar, jelly, and chewed peanuts with saliva) successfully demonstrated realistic mechanical responses, with the jelly gel (0.5 N fracture strength) exhibiting breakdown during force contraction at biologically relevant thresholds. These advancements improve biomechanical fidelity in artificial digestive systems for pharmaceutical testing, food digestibility studies, and medical device evaluation under physiologically accurate conditions.