Korea Institute of Machinery and Materials Develops 'Wheel and Mobile' Robot Technology Mimicking Liquid Principles

A wheel and mobile robot technology capable of smoothly passing obstacles such as stairs and rocks by mimicking the principle of surface tension of liquid droplets has been developed.

The Korea Institute of Machinery and Materials (KIMM) announced on the 2nd that it has succeeded in developing the world's first morphing wheel based on this principle and applying it to mobile platforms.

This technology was developed by a team led by Principal Researcher Song Seonghyeok and Director Park Dongil of the Advanced Robotics Research Center at KIMM's AI Robotics Laboratory.

Since it can adjust stiffness according to the shape of obstacles to pass over objects, it is expected to be widely applicable to all mobile platforms where overcoming road obstacles is crucial.

A wheelchair equipped with a morphing wheel is easily overcoming an obstacle (stairs). Photo by Korea Institute of Machinery and Materials

The morphing wheel developed by the research team can freely adjust stiffness solely by changes in surface tension applied to smart chain blocks, without complex mechanical devices or sensors.

It normally operates as a rigid circular wheel, but when overcoming obstacles, the wheel softens and can freely deform according to the height and shape of the obstacle, which is its distinctive feature.

Previously, there were technologies that configured the inside of wheels with flexible structures like non-pneumatic tires. However, existing technologies continuously caused large deformations to the wheel even on flat surfaces, reducing driving efficiency and stability.

In contrast, the morphing wheel developed by the research team can adjust stiffness as desired, maintaining the same stiffness as a conventional wheel when driving at high speed on flat ground, and only softening the wheel in real time when encountering obstacles to overcome them.

The morphing wheel consists of smart chain blocks and flexible structures. The outermost part of the wheel is the smart chain block, and a wire spoke structure that controls the surface tension of the smart chain block is connected to the wheel’s hub structure.

When the hub structure rotates or changes distance, the wire spoke structure is either strongly pulled or loosened, causing the surface tension of the smart chain block structure to change.

The wire spoke refers to the spokes connecting the wheel hub, located at the center of rotation generating rotational force, to the outermost structure of the wheel.

Center Director Dongil Park (left) and Senior Researcher Seonghyeok Song (right). Provided by Korea Institute of Machinery and Materials

The research team completed verification of the variable stiffness wheel’s change mechanism in October last year. Recently, they also developed modular technology that can be easily applied to various mobile platforms. The mechanism for changing stiffness was miniaturized and lightened to be inserted inside the wheel, and modularized to establish a foundation for application to mobile systems such as two-wheel based wheelchairs.

The two-wheel based wheelchair system can change the wheel stiffness in real time, enabling stable movement and is advantageous for maneuvering in narrow spaces such as turning on the spot. It can easily move over obstacles like rocks or stairs up to 18 cm high.

The research team tested the obstacle overcoming performance by applying this technology to a four-wheel based mobile platform and confirmed that it can stably overcome obstacles up to 1.3 times the wheel radius in height.

Principal Researcher Song Seonghyeok said, “Quadruped or biped walking robots designed to overcome obstacles have low movement efficiency on flat ground and inevitably experience shaking during movement. However, the morphing wheel developed by our team is meaningful in that it maintains the high mobility efficiency of conventional wheels while enabling obstacle overcoming, which was previously a limitation of wheels.”

Director Park Dongil said, “The surface tension mimicking wheel technology can overcome the limitations of complex mechanical devices such as legged robots and wheel clusters used for obstacle overcoming. We expect the technology developed by our team to be widely utilized in the future not only for wheelchairs but also for mobile robots and ride-on transportation devices.”

This content was produced with the assistance of AI translation services.