Science+Robotics
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RAIBO Runs over Walls with Feline Agility... Ready for Effortless Search over Mountaineous and Rough Terrains
< Photo 1. Research Team Photo (Professor Jemin Hwangbo, second from right in the front row) >
KAIST's quadrupedal robot, RAIBO, can now move at high speed across discontinuous and complex terrains such as stairs, gaps, walls, and debris. It has demonstrated its ability to run on vertical walls, leap over 1.3-meter-wide gaps, sprint at approximately 14.4 km/h over stepping stones, and move quickly and nimbly on terrain combining 30° slopes, stairs, and stepping stones. RaiBo is expected to be deployed soon for practical missions such as disaster site exploration and mountain searches.
Professor Jemin Hwangbo's research team in the Department of Mechanical Engineering at our university announced on June 3rd that they have developed a quadrupedal robot navigation framework capable of high-speed locomotion at 14.4 km/h (4m/s) even on discontinuous and complex terrains such as walls, stairs, and stepping stones.
The research team developed a quadrupedal navigation system that enables the robot to reach its target destination quickly and safely in complex and discontinuous terrain.
To achieve this, they approached the problem by breaking it down into two stages: first, developing a planner for planning foothold positions, and second, developing a tracker to accurately follow the planned foothold positions.
First, the planner module quickly searches for physically feasible foothold positions using a sampling-based optimization method with neural network-based heuristics and verifies the optimal path through simulation rollouts.
While existing methods considered various factors such as contact timing and robot posture in addition to foothold positions, this research significantly reduced computational complexity by setting only foothold positions as the search space. Furthermore, inspired by the walking method of cats, the introduction of a structure where the hind feet step on the same spots as the front feet further significantly reduced computational complexity.
< Figure 1. High-speed navigation across various discontinuous terrains >
Second, the tracker module is trained to accurately step on planned positions, and tracking training is conducted through a generative model that competes in environments of appropriate difficulty.
The tracker is trained through reinforcement learning to accurately step on planned plots, and during this process, a generative model called the 'map generator' provides the target distribution.
This generative model is trained simultaneously and adversarially with the tracker to allow the tracker to progressively adapt to more challenging difficulties. Subsequently, a sampling-based planner was designed to generate feasible foothold plans that can reflect the characteristics and performance of the trained tracker.
This hierarchical structure showed superior performance in both planning speed and stability compared to existing techniques, and experiments proved its high-speed locomotion capabilities across various obstacles and discontinuous terrains, as well as its general applicability to unseen terrains.
Professor Jemin Hwangbo stated, "We approached the problem of high-speed navigation in discontinuous terrain, which previously required a significantly large amount of computation, from the simple perspective of how to select the footprint positions. Inspired by the placements of cat's paw, allowing the hind feet to step where the front feet stepped drastically reduced computation. We expect this to significantly expand the range of discontinuous terrain that walking robots can overcome and enable them to traverse it at high speeds, contributing to the robot's ability to perform practical missions such as disaster site exploration and mountain searches."
This research achievement was published in the May 2025 issue of the international journal Science Robotics.
Paper Title: High-speed control and navigation for quadrupedal robots on complex and discrete terrain, (https://www.science.org/doi/10.1126/scirobotics.ads6192)YouTube Link: https://youtu.be/EZbM594T3c4?si=kfxLF2XnVUvYVIyk
2025.06.04 View 252 -
A Quick but Clingy Creepy-Crawler that will MARVEL You
Engineered by KAIST Mechanics, a quadrupedal robot climbs steel walls and crawls across metal ceilings at the fastest speed that the world has ever seen.
< Photo 1. (From left) KAIST ME Prof. Hae-Won Park, Ph.D. Student Yong Um, Ph.D. Student Seungwoo Hong >
- Professor Hae-Won Park's team at the Department of Mechanical Engineering developed a quadrupedal robot that can move at a high speed on ferrous walls and ceilings.
- It is expected to make a wide variety of contributions as it is to be used to conduct inspections and repairs of large steel structures such as ships, bridges, and transmission towers, offering an alternative to dangerous or risky activities required in hazardous environments while maintaining productivity and efficiency through automation and unmanning of such operations.
- The study was published as the cover paper of the December issue of Science Robotics.
KAIST (President Kwang Hyung Lee) announced on the 26th that a research team led by Professor Hae-Won Park of the Department of Mechanical Engineering developed a quadrupedal walking robot that can move at high speed on steel walls and ceilings named M.A.R.V.E.L. - rightly so as it is a Magnetically Adhesive Robot for Versatile and Expeditious Locomotion as described in their paper, “Agile and Versatile Climbing on Ferromagnetic Surfaces with a Quadrupedal Robot.” (DOI: 10.1126/scirobotics.add1017)
To make this happen, Professor Park's research team developed a foot pad that can quickly turn the magnetic adhesive force on and off while retaining high adhesive force even on an uneven surface through the use of the Electro-Permanent Magnet (EPM), a device that can magnetize and demagnetize an electromagnet with little power, and the Magneto-Rheological Elastomer (MRE), an elastic material made by mixing a magnetic response factor, such as iron powder, with an elastic material, such as rubber, which they mounted on a small quadrupedal robot they made in-house, at their own laboratory. These walking robots are expected to be put into a wide variety of usage, including being programmed to perform inspections, repairs, and maintenance tasks on large structures made of steel, such as ships, bridges, transmission towers, large storage areas, and construction sites.
This study, in which Seungwoo Hong and Yong Um of the Department of Mechanical Engineering participated as co-first authors, was published as the cover paper in the December issue of Science Robotics.
< Image on the Cover of 2022 December issue of Science Robotics >
Existing wall-climbing robots use wheels or endless tracks, so their mobility is limited on surfaces with steps or irregularities. On the other hand, walking robots for climbing can expect improved mobility in obstacle terrain, but have disadvantages in that they have significantly slower moving speeds or cannot perform various movements.
In order to enable fast movement of the walking robot, the sole of the foot must have strong adhesion force and be able to control the adhesion to quickly switch from sticking to the surface or to be off of it. In addition, it is necessary to maintain the adhesion force even on a rough or uneven surface.
To solve this problem, the research team used the EPM and MRE for the first time in designing the soles of walking robots. An EPM is a magnet that can turn on and off the electromagnetic force with a short current pulse. Unlike general electromagnets, it has the advantage that it does not require energy to maintain the magnetic force. The research team proposed a new EPM with a rectangular structure arrangement, enabling faster switching while significantly lowering the voltage required for switching compared to existing electromagnets.
In addition, the research team was able to increase the frictional force without significantly reducing the magnetic force of the sole by covering the sole with an MRE. The proposed sole weighs only 169 g, but provides a vertical gripping force of about *535 Newtons (N) and a frictional force of 445 N, which is sufficient gripping force for a quadrupedal robot weighing 8 kg.
* 535 N converted to kg is 54.5 kg, and 445 N is 45.4 kg. In other words, even if an external force of up to 54.5 kg in the vertical direction and up to 45.4 kg in the horizontal direction is applied (or even if a corresponding weight is hung), the sole of the foot does not come off the steel plate.
MARVEL climbed up a vertical wall at high speed at a speed of 70 cm per second, and was able to walk while hanging upside down from the ceiling at a maximum speed of 50 cm per second. This is the world's fastest speed for a walking climbing robot. In addition, the research team demonstrated that the robot can climb at a speed of up to 35 cm even on a surface that is painted, dirty with dust and the rust-tainted surfaces of water tanks, proving the robot's performance in a real environment. It was experimentally demonstrated that the robot not only exhibited high speed, but also can switch from floor to wall and from wall to ceiling, and overcome 5-cm high obstacles protruding from walls without difficulty.
The new climbing quadrupedal robot is expected to be widely used for inspection, repair, and maintenance of large steel structures such as ships, bridges, transmission towers, oil pipelines, large storage areas, and construction sites. As the works required in these places involves risks such as falls, suffocation and other accidents that may result in serious injuries or casualties, the need for automation is of utmost urgency.
One of the first co-authors of the paper, a Ph.D. student, Yong Um of KAIST’s Department of Mechanical Engineering, said, "By the use of the magnetic soles made up of the EPM and MRE and the non-linear model predictive controller suitable for climbing, the robot can speedily move through a variety of ferromagnetic surfaces including walls and ceilings, not just level grounds. We believe this would become a cornerstone that will expand the mobility and the places of pedal-mobile robots can venture into." He added, “These robots can be put into good use in executing dangerous and difficult tasks on steel structures in places like the shipbuilding yards.”
This research was carried out with support from the National Research Foundation of Korea's Basic Research in Science & Engineering Program for Mid-Career Researchers and Korea Shipbuilding & Offshore Engineering Co., Ltd..
< Figure 1. The quadrupedal robot (MARVEL) walking over various ferrous surfaces. (A) vertical wall (B) ceiling. (C) over obstacles on a vertical wall (D) making floor-to-wall and wall-to-ceiling transitions (E) moving over a storage tank (F) walking on a wall with a 2-kg weight and over a ceiling with a 3-kg load. >
< Figure 2. Description of the magnetic foot (A) Components of the magnet sole: ankle, Square Eletro-Permanent Magnet(S-EPM), MRE footpad. (B) Components of the S-EPM and MRE footpad. (C) Working principle of the S-EPM. When the magnetization direction is aligned as shown in the left figure, magnetic flux comes out of the keeper and circulates through the steel plate, generating holding force (ON state). Conversely, if the magnetization direction is aligned as shown in the figure on the right, the magnetic flux circulates inside the S-EPM and the holding force disappears (OFF state). >
Video Introduction: Agile and versatile climbing on ferromagnetic surfaces with a quadrupedal robot - YouTube
2022.12.30 View 17000