Experimental Study on the Closed-Loop Control of a Soft Ring-Shaped Actuator for In-vitro Gastric Simulator

In-vitro gastric simulators are soft robotic systems that reproduce the change of the food or drug by emulating the stomach's motility functions. The control of gastric simulators traditionally lies in tuning the actuators via open-loop approaches. However, the lack of precise position control, external disturbances, sensitivity to model uncertainties, and continues retuning are solid motivations for employing closed-loop methods to control gastric simulators. A bellows-driven viscoelastic soft ring-shaped pneumatic actuator (RiSPA), including five spring-like bellows, was developed for stomach simulators' primary actuation system. This article studies the implementation of closedloop methods equipped with the online feedback system on the RiSPA for the first time. All technical aspects for implementing the closed-loop control and the sensor-actuator integration are discussed in detail. A model-based closedloop method has been implemented and compared with a classic model-free method to show the closed-loop system's ability to reject model uncertainties. The experimental results in both the tracking trajectory and the regulation performances are thoroughly compared to the open-loop approach, where the superiority of closed-loop techniques is demonstrated. A mechanical setup is designed to show the ability of the closed-loop approach in dealing with the disturbances and external loads as well.

Automated summary

This study implements closed-loop methods for controlling gastric simulators for the first time, demonstrating the superiority of closed-loop techniques over open-loop approaches through experimental results. By using the RiSPA bellows-driven soft pneumatic actuator as the main actuation system, all technical aspects of implementing closed-loop control and sensor-actuator integration are discussed in detail.