Accessing tubular environment is critical in medicine. For example, gastrointestinal tract related cancers are the leading causes of cancer deaths globally. To diagnose and treat these cancers, clinicians need accessing the gastrointestinal tract, for example, colon and small intestine, which are soft biological tubes. Soft balloon assisted locomotion is one of the promising methods for accessing bio-duct. It has been widely used in enteroscopy and other medical devices. However, the interaction between the balloon and the soft tube is seldom studied, such as the interaction pressure and the anchoring force. In this work, we present the first modeling of the interaction between soft balloon actuators and soft tubular environment. The free inflation model of soft balloon actuators was first presented. Then a constrained inflation model of the soft balloon in a soft tube was established. Finally, the anchoring force model between the soft balloon and the soft tube was developed. On average, the mean error of the predictions in these three models is 0.228 kPa (or 3.14%), 0.56 kPa (or 7.8%), and 0.22 N (or 14.7%), respectively. In the future, these models could be used for guiding balloon-actuator designs by minimizing the interaction pressure while maintaining sufficient anchoring force during the locomotion in soft tubes.
Keywords: highly deformable robots; soft interaction; soft locomotion.