SERPENT: An SMA Exploration Robot for Planetary Environments and Navigating Terrain

Given the discovery of underground caves and tunnels on other celestial bodies, there is growing interest in creating sustainable living environments for advancing humanity’s multi-planetary future. A critical step to achieve this is to explore the potential of underground caves for human habitation using exploration robots. Thus, a snake robot that uses Shape Memory Alloys (SMA) for actuation is proposed to be used on Mars to mimic the flexibility of a snake required to navigate underground caves and tunnels. The design of the SMA Exploration Robot for Planetary Environments and Navigating Terrain (SERPENT) drew inspiration from the biological characteristics of how snakes traverse. The scales on the exteriors of snakes, coupled with the mechanics of serpentine locomotion, inspired the mechanical design and gait motion of SERPENT. The body of SERPENT consists of four links made of PET-G material connected by 3 Teflon rotational joints, providing 2 degrees of freedom per joint. A gait sequence was also created that replicates the serpentine locomotion of a snake, utilizing the serpentine motion for forward movement. An HC-SR04 ultrasonic sensor is also mounted on the front of SERPENT and was chosen to detect obstacles and trigger redirection. A two-link and four-link assembly yielded a linear displacement of 3.9 cm ± 0.1 cm and 6.7 cm ± 0.1 cm respectively over 20 minutes. When activated, one joint produced an angular displacement of 48°± 1°, between two links, and the entire four-link assembly produced a 69°± 1°. By designing the gait sequence such that only one SMA is activated at a time, the maximum power requirement for the forward motion of SERPENT is 11 W under Earth conditions. Given that SERPENT will be applied to the conditions on Mars, the power requirement is expected to be less than that on Earth conditions due to its thinner atmosphere. These results demonstrate the potential of SERPENT as an efficient and adaptable robot for planetary exploration.