KAIST

KAIST's quadrupedal walking robot 'RAIBO', which ran freely on the beach, was newly developed into 'RAIBO2' and achieved the world's first record of participating in and successfully completing its run in a full-course marathon event.

< Photo 1. A group photo of RAIBO2 and the team after completing the full-course marathon >

KAIST (President Kwang Hyung Lee) announced on the 17th of November that Professor Je Min Hwangbo's research team of the Department of Mechanical Engineering participated in the 22nd Sangju Dried-Persimmon Marathon and completed the full-course race (42.195 km) with a time of 4 hours 19 minutes and 52 seconds.

< Photo 2. RAIBO2 after completing the full-course marathon with its official record presented on the photo wall >

The Sangju Dried Persimmon Marathon has a course with two 50m hills, each at the 14km and 28km points which could cause unexpected energy losses, making it a challenging task for walking robots, and is known to be difficult even for seasoned amateur marathoners. 

< Photo 3. RAIBO2 with the completion medal around its neck >

The research team developed a walking controller using a reinforcement learning algorithm to enable stable walking by creating various environments such as slopes, stairs, and icy roads in the 'RaiSim' simulation environment developed by Professor Hwangbo.

In particular, the joint mechanism with high torque transparency was able to efficiently charge energy on the downhill slope and absorb some of the energy used to climb the steep hill.

In addition, the stability of the robot was greatly improved through joint development effort by RAION ROBOTICS Co., Ltd., a start-up company founded by the researchers from Professor Hwangbo’s lab.

< Figure 1. Conceptual diagram of power flow employed by the quadrupedal robot >

< Figure 2. The process of leg posture change of RAIBO2 walking at the most efficient walking speed of 3 m/s. By reducing the ground contact speed of the feet, the collision energy loss was reduced, and by minimizing the slipperiness of the foot upon contact, the body's kinetic energy was maintained towards the direction of the movement. >

Due to the nature of walking, pedal robots must employ highly complex systems that can withstand periodic vibrations from the frequent impacts that occur upon contact with the ground surface. Immediately after development, high efficiency was already recorded in short-distance experiments in the laboratory at the beginning of the year, but the manufacturing technology of RAION ROBOTICS played a major role in safely running for a prolonged time of more than 4 hours among random pack of people in an actual marathon.

Compared to previous studies on improving walking efficiency, where external parts or software could not be changed and only limited improvements were made in some areas, Professor Hwangbo’s research team cited the fact that they were able to comprehensively solve problems by developing all steps and parts in-house, including mechanism design, electrical design, software, and artificial intelligence, as a key factor in improving efficiency.

Following the development of RAIBO1, the research team developed RAIBO2 and optimized all areas, and in particular, internalized the motor driver circuit to minimize actuator loss and increase the control bandwidth, greatly improving walking efficiency and stability.

< Photo 4. RAIBO2 running the full-course marathon along human participants >

Choongin Lee, a Ph.D. Student that co-first author of the studies on RAIBO, said, “Through the marathon project, we have shown that RAIBO2 has the walking performance to stably execute services such as delivery and patrol in urban environments with many people and random objects,” and “In follow-up research, we will add autonomous driving functions to RAIBO and strive to achieve the world’s best walking performance in mountainous and disaster environments.”

< Photo 5. RAIBO2 and co-first authors of the related research at the Ph.D. program of the Department of Mechanical Engineering at KAIST. (From left) Choongin Lee, Donghoon Youm, and Jeongsoo Park >

This research was conducted with the support of Samsung Electronics Future Technology Promotion Center and RAION ROBOTICS Co., Ltd.