Having Trouble Traversing the Sands of Mars? A Lizard Robot Might Help

Mars exploration vehicles typically have wheels, allowing them to traverse some challenging terrain on the Red Planet. However, eventually, their systems start to wear down, and one of their wheels gets stuck. The “Free Spirit” campaign in 2009 was the most widely known case. Unfortunately, that campaign wasn’t successful, and now, 15 years later, Spirit remains stuck in its final resting place. Things might have been different if NASA had adopted a new robot paradigm developed by Guangming Chen and his colleagues at the Nanjing University of Aeronautics & Astronautics Lab of Locomotion Bioinspiration and Intelligent Robots. They devised a robot based on a desert lizard, with adaptable feet and a flexible “spine” that, according to their calculations, would be well suited to traversing over Martian regolith.

Planning for traversing tough terrain isn’t limited to rovers that are stuck. Curiosity and Perseverance, perhaps the two best-known operating rovers on Mars, currently spend a lot of their time trying to avoid areas where they might become entangled. This limits their ability to capture any data from those areas, potentially missing out on some cool rocks, like the pure sulfur that Curiosity recently found for the first time on Mars. 

A lizard-inspired robot, on the other hand, would have no trouble traversing such terrain. It also has some advantages over traversing different types of terrain, such as rocks. Most rovers don’t have enough leg lift to get over medium-sized rocks, whereas a legged robot would, especially one with adjustable “toes” that would allow it to grip a rock tighter than would otherwise be possible with typical legged robots.

The design for the robot itself is relatively simple – it has four “feet” that are offset from each other by a chassis that essentially looks like a desert lizard. It even has a tail for counterbalancing. Each foot has a series of three “toes” powered by springs. They also have a servo for ankle articulation and a bearing for rotational control. This combination allows the lizard robot to walk on all fours effectively and adjust each leg to best adapt to the surface it is “walking” over.

The authors performed a series of kinematic calculations for different types of terrain to help understand how the robot would interact with each of those surfaces. Kinematic calculations are typically used in robotics when designers attempt to find the best way to move a specific robot part. The calculations are relatively detailed in this case, given the number of variable parts. However, a control algorithm is possible using just on-board computation, allowing for some basic autonomous terrain navigation if architecture is ever adopted for use in space.

Building an actual prototype would be a great way to work on that navigation algorithm, and that’s precisely what the researchers did. They 3D printed many of the parts for the chassis and foot, embedded some batteries and controllers in the head and tail sections, and started testing the prototype on simulated Martian test terrain.

They tested everything from grasping loose regolith to climbing over small rocks, and their algorithm seemed to work effectively for handling the relatively simple terrain in the test bed. However, the robot’s actual speed of movement was slower than originally simulated, mainly due to technical difficulties in balancing the motions of the springs and the spine. 

Despite any problems that arose during physical testing, this new robot iteration is a step in the right direction, as this lab has been designing similar systems for years. They also plan to continue to another version, including mounting a continuous power supply and fully implementing an autonomous navigation algorithm. Their research is funded by both Jiangsu Province and the Chinese Ministry of Science and Technology, so it seems it will continue to gain support, at least for the foreseeable future.

Learn More:
Chen et al. – Development of a Lizard-Inspired Robot for Mars Surface Exploration
UT – Spirit Extrication, Day 1: Drive Stopped After 1 Second
UT – Bio-Mimicry and Space Exploration
UT – Robots Might Jump Around to Explore the Moon

Lead Image:
Image of the prototyped lizard biomimetic robot.
Credit – Chen et al.