Many people are already creeped out by quadruped robots, which walk on four legs instead of rolling on wheels or tracks. Well, the MARVEL robot likely won't do much to change such feelings, as it can walk straight up ferromagnetic metal walls.
Its name an acronym for "Magnetically Adhesive Robot for Versatile and Expeditious Locomotion," MARVEL was designed by a team at the Korea Advanced Institute of Science and Technology (KAIST) led by Prof. Hae-Won Park.
Each of the robot's four feet incorporate both an electro-permanent magnet (EPM) and a magneto-rheological elastomer (MRE) sole.
Unlike a conventional electromagnet, the EPM requires power only to switch between magnetic and non-magnetic states – in other words, it doesn't use any power to maintain its magnetic force. The MRE used in the soles is made up of urethane rubber mixed with iron particles, resulting in a material that is both elastic and ferromagnetic.
To climb up vertical metal surfaces – or even to walk upside-down across metal ceilings – MARVEL simply switches the magnetism of its feet on and off as it moves each one forward. While the EPMs provide all the attractive force, the MRE soles provide the grip needed to keep the robot from sliding downwards.
The combination of the two technologies allows MARVEL to maintain its position on a metal wall or ceiling even when an external vertical force of up to 54.5 kg (120 lb) or a horizontal force of up to 45.4 kg (100 lb) is applied. MARVEL itself weighs about 8 kg (18 lb).
In tests conducted so far, the robot was able to climb walls at a maximum speed of 70 cm (28 in) per second, and to walk across ceilings at up to 50 cm (20 in) per second. It had no difficulty transitioning between walking on floors, walls and ceilings, plus it could step over 5-cm (2-in)-tall obstacles.
The latter capability gives MARVEL a distinct advantage over tracked or wheeled wall-climbing robots, which would likely be thwarted by such challenges.
Additionally, even when vertical metal surfaces were coated in paint, dust or rust, the robot was still able to climb at a rate of 35 cm (14 in) per second. This is an important consideration for its possible real-world applications, which include the inspection, maintenance and/or repair of things like ships, bridges, radio towers, storage tanks and iron girders at construction sites.
"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," said Park. "We believe this would become a cornerstone that will expand the mobility and the places of pedal-mobile robots can venture into."
MARVEL is described in a paper that was recently published in the journal Science Robotics. The bot can be seen in action, in the video below.
Source: KAIST