Standing in a field, the four-legged robot almost looks cute. And then it moves.

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It is … unsettling. At first, it’s hard to not reflexively react in the way one might when encountering an eight-legged arachnid in an unexpected place, like your bed or a bag of flour. As you’d guess, there’s a practical reason for developing a four-legged spider-like robot, namely carrying stuff from place to place.

Robotics researchers at the Suzumori Endo Lab at the Tokyo Institute of Technology were working to prove that insect-style quadruped robots could walk as fast as mammal style robots, so they built the terrifying Titan-XIII to prove it. They published their results in ROBOMECH Journal in 2016 and they released footage of the Titan-XIII scuttling around a grassy field on Tuesday, which looks like video of a second set of experiments on how insect robots are better at moving on uneven ground than mammal robots.

Titan-XIII
Titan-XIII, cutest when not moving.

Mammalian-type quadruped robots have legs that are mostly vertical and many robots have been styled after mammals, because researchers thought the style of walking was faster and more mechanically efficient, making them more cost-effective. And since walking robots are being designed to carry stuff over uneven ground, this has made mammal-robots desirable.

However, the researchers Satoshi Kitano, Gen Endo, Koichi Suzumori, and Shigeo Hirose, point out in their paper that insectoid robots have lower centers of gravity, and greater stability than mammal-robots, making them better suited to carrying things over uncertain ground. Even with potentially less efficient legs (the top leg segment of sprawling-type insect robots is horizontal) they think these guys are better suited to carrying things.

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To prove this, they changed how sprawling robots move. Instead of moving one leg at a time, the Titan-XIII trots – moving diagonal pairs of legs forward at the same time. Mammalian robots do this because it’s more efficient, but researchers had stuck to moving a single leg at a time in insect robots to maximize stability. When Titan-XIII trots it remains stable because if it falls it’s designed to swing around the stable diagonal legs until it’s standing up on three legs.

Titan XIII leg structure
The left drawing is the basic structure of Titan XIII legs and range of motion in each joint. On the left is the detailed version of the leg with the locations of all the motors. 

Each leg of the Titan-XIII can be replaced and has three axes of movement, similar to a shoulder or hip joint. There are four little motors, one for each leg, and there are two pulleys and two wires that act like muscle tendons to move the spider legs. The little dude is wifi-controlled by a computer program, so it’s not an autonomous spider nightmare — yet.

The original paper showed the Titan-XIII walking in a flat lab environment, so the footage from out in a yard looks like the beginnings of a second set of experiments on more uneven ground. Maybe Titan-XIII will be the replacement for the Marine’s robot dogs.

Photos via  Kitano et al. 2016, Kitano et al. 2016, Suzumori Endo Lab, Tokyo Institute of Technology