Nonlinear Model Predictive Control of a Robotic Soft Esophagus

Abstract

Strictures caused by esophageal cancer can narrow down the esophageal lumen, leading to dysphagia. Palliation of dysphagia has driven the development of a Robotic Soft Esophagus (RoSE) to provide a novel in vitro platform for esophageal stent testing and food viscosity studies. In RoSE, peristaltic wave generation and control were done in an open-loop manner since the conduit lacked visibility and embedded sensing capability. Hence, in this work, RoSE version 2.0 (RoSEv2.0) was designed with embedded Time Of Flight (TOF) and pressure sensors to measure conduit displacement and air pressure, respectively, for modeling and control. Model Predictive Control (MPC) of RoSEv2.0 was implemented to govern the peristalsis and air pressure profile autonomously. The implemented MPC used Sparse Identification Nonlinear Dynamics with Control (SINDYC) models to estimate the future states of ROSEv2.0. The dynamic models were discovered from the TOF and pressure sensors captured data. Peristalsis waves of speed 20 mm/s, wavelength 75 mm, and amplitudes 5, 7.5, and 10 mm were successfully generated by the MPC. Additionally, RoSEv2.0 with the MPC was employed to perform stent migration testing with various food boluses consistencies.

Bio-Inspired Robots Imitating Human Organs with Embodied Intelligence Behaviour

“…As the conduit is soft, applying pressure to inflate these chambers cause the conduit to contract. The peristaltic wave in the esophagus is a sinewave-like that has been already specified in the literature [20]. Inflating three layers in the robot conduit produces a sine wave that can be controllable.…”

“…The sinewave characteristics such as amplitude and wavelength are controllable. Different control methods can be applied to achieve a desired sine wave inside the conduit either by open-loop control for generating spatiotemporal waves [21] or with closed-loop through nonlinear model predictive control [20]. The ability to control the peristaltic wave opens the door to simulate many behaviours, such as dysphagia.…”

“…In a robot that simulates the GI tract, adaptive behaviour is critical for generating the [20,21]). peristaltic wave.…”

“…Figure 3. A section of RoSEv2.0 in a cross-section view that illustrate a travelling peristaltic wave from top to bottom (adapted from[20,21]). …”