Locomotion and Obstacle Avoidance of a Worm-like Soft Robot

TL;DR

The paper addresses robust locomotion and obstacle avoidance for a worm-like soft robot operating in unknown, confined environments. It introduces a modular three-segment robot actuated pneumatically using both longitudinal and radial expansion, coupled with onboard proprioceptive sensing from phototransistors and copper tape sensors to navigate without external vision. The control strategy combines peristaltic-like locomotion with circumnutation-inspired oscillations and obstacle-driven reorientation, guided by real-time sensor feedback to reach a light source. Results identify optimal actuation parameters, demonstrate convergence toward targets in cluttered settings, and point to mobile future versions by removing the pneumatic tether for broader practical impact in search-and-rescue, environmental monitoring, and subterranean exploration.

Abstract

This paper presents a soft earthworm robot that is capable of both efficient locomotion and obstacle avoidance. The robot is designed to replicate the unique locomotion mechanisms of earthworms, which enable them to move through narrow and complex environments with ease. The robot consists of multiple segments, each with its own set of actuators, that are connected through rigid plastic joints, allowing for increased adaptability and flexibility in navigating different environments. The robot utilizes proprioceptive sensing and control algorithms to detect and avoid obstacles in real-time while maintaining efficient locomotion. The robot uses a pneumatic actuation system to mimic the circumnutation behavior exhibited by plant roots in order to navigate through complex environments. The results demonstrate the capabilities of the robot for navigating through cluttered environments, making this development significant for various fields of robotics, including search and rescue, environmental monitoring, and medical procedures.

Figures (5)

• Figure 1: Illustration of obstacle navigation in biological earthworm and a soft earthworm robot. A. Earthworm navigating through a challenging environment with rigid acrylic pegs regularly distributed on the surface. B. Our soft earthworm robot imitates this behavior. C. Feature description of our robot which includes one two-chambered linear soft actuator, two radial actuators, phototransistor light sensors, and copper tape contact sensors.
• Figure 2: Control and sensing system of the robot. The robot's nose cone circuit includes a microcontroller, phototransistor light sensors, and copper tape contact sensors. The sensory information is transmitted wirelessly to the pressure control circuit that includes an Arduino control board, four QB3 pneumatic regulators, an air supply, and a manifold to distribute the air. Note that electrical connections are noted in green and pneumatic connections are noted in blue.
• Figure 3: The top and side view of the experimental test setup. The setup consists of cylindrical pegs (d = 7.5 cm), six foam ground mats (60 cm x 60 cm) covered with an acrylic sheet (150 cm X 90 cm), and a light source. The pegs are covered The fixed obstacles are affixed to the structure to prevent the robot from colliding with them while traveling toward the light source. Conversely, the unfixed obstacles are positioned strategically to support the weight of the acrylic sheet.
• Figure 4: Peristaltic Gait of biological and robotic earthworm.A. Earthworm moves from left to right with a peristaltic gait Perastaltic, B. the locomotion cycle of an earthworm-like robot. The value of X is the net displacement due to one cycle of locomotion.
• Figure 5: Locomotion of the robot towards the light source while navigating obstacles. A.The trajectories of the nose from five separate runs to reach the light source on the far side of the testing environment B.Similarly, trajectories of five runs to reach a target at the top of a testing environment.