A Wheel-to-Leg Transformable Robot

With the general audience preferring to engage in the search for anthropomorphization, the popularity of biped and quadruped robots has been growing. At the Worcester Polytechnic Institute, researchers have innovated a robotic system that they call the OmniWheg—a robotic system that adapts its configuration based on the surrounding environment that it is navigating. They introduced this robot in a paper in the IEEE IROS 2022, and pre-published it on arVix. OmniWheg has its origins in an updated version of whegs, which was a mechanism with a design to transform the wings or wheels of a robot into legs.

Although the researchers would have liked to make the robot capable of going everywhere they go, they found the cost of legs to be very high. While evolution has provided humans and animals with legs, the researchers found that a robot with legs would be highly energy inefficient. While legs could make the robot more human or animal-like, they would not be able to complete tasks quickly and efficiently. Therefore, rather than develop a robot with a single mechanism for locomotion, the team proceeded to create a system that switched between various mechanisms.

The team found that about 95% of the environments at homes and workplaces are flat, while the rest are uneven terrains that require transitioning. Therefore, they went on to develop a robot that performs with a high-efficiency wheel-like arrangement for 95% of the cases, specifically transforming to the lower-efficiency mechanism for the remaining 5%.

The researchers, therefore, created a wheel that changed its configuration for climbing stairs or for circumventing small obstacles. For this, they utilized the concept of whegs,  wing-legs, or wheel-legs, which is popular in the field of robotics.

In the past few years, the team developed and tested several wheel-leg systems. However, most of them were not successful, as the left and right sides of the wheel-leg system would not coordinate well or align properly when the robot tried climbing stairs.

Finally, the team could solve the coordination issues by using an omnidirectional wheel. This enabled the robot to align on-the-fly, but without rotating its body. Therefore, the robot can move forward, backward, and sideways at high efficiency, and remain in a stable position without expending any energy. At the same time, the robot can also climb stairs swiftly, when necessary.

For correct operation, the wheg system that the team developed requires a servo motor to be added to each wheel and operated with a simple algorithm. As the design is straightforward and basic, any other team can easily replicate it.

According to the researchers, the system has abundant advantages with very few drawbacks. The team feels it can pose a threat to the legged robots, and any robotic application can adopt this design.

The team has evaluated their OmniWheg robot system on a multitude of real-world indoor scenarios. This includes climbing steps of various heights, circumventing obstacles, and moving/turning omnidirectionally. They found the results to be highly promising, and the wheel-leg robot could successfully navigate the common obstacles quite flexibly and efficiently.