Strength and flexibility of a giraffe's neck inspired a new robot in Japan

When we think about robot flexibility, the best examples usually come from soft robots that mimic an octopus's tentacles or an elephant's trunk, which have some unique capabilities. But most animals are to some degree soft and flexible, typically combined with a rigid internal structure. 

This is a complex system, though with some significant advantages in power and control. Researchers from the Tokyo Institute of Technology experimented with imitating what may be one of the most impressive combinations of flexibility and strength in the animal world: the giraffe's neck. 

The work is still research-oriented and is meant only to help find ways to transfer the anatomy of a real animal to machinery. However, the robotic neck already moves similarly to its example and can even adapt to applied force (applied by the engineers' hands). The prototype is still far from everything living giraffes can do, but the engineers plan to increase its flexibility and endurance.

"The giraffe's neck has excellent characteristics that could serve as a good alternative for designing a large robotic mechanism. For example, the neck can move quickly when giraffes strike each other's necks. In addition, the giraffe's neck helps prevent impacts and adapts to the shape and hardness of the opponent's neck. In contrast, a conventional robotic mechanism is limited in its ability to achieve such power and flexibility characteristics, that is, to be powerful while also resisting impacts, and to have kinematic and dynamic adaptability to an opponent," the study says. 

Giraffe necks can weigh up to 150 kilograms and reach 2 meters in length, but over the course of evolution they became flexible and strong not only to reach tasty high-growing leaves, but also because male giraffes fight each other with their necks, sometimes to the death. What could be a better source of inspiration for developing large robots, right?

As a first step toward building a powerful and flexible robot, the researchers built a half-scale skeletal-muscular robot that imitates the structure and mechanism of the giraffe's neck based on anatomical knowledge, and reproduced some of its characteristics.

The device consists of a skeletal mechanism made with a 3D printer, a gravity compensation mechanism that imitates the nuchal ligament using rubber material and tensioners, a redundant muscle control system using thin artificial muscles, and a special joint using rubber discs and imitation ligaments.

The robotic giraffe neck does its best to imitate the structure of a real giraffe neck, with a similar arrangement of vertebrae and tendons and thin McKibben pneumatic artificial muscles providing contractile force, just as real muscles do. This is complex, but it provides significant flexibility.

The authors note that giraffes can use the strength and flexibility of their necks when contacting each other in a non-destructive way, which conventional mechanical systems cannot do.

Until now, researchers have not developed machines or robots with the same power and flexibility characteristics as a giraffe's neck. For example, if two real industrial cranes were to fight, it is easy to imagine the damage would be catastrophic, with both cranes breaking. Compare this with real giraffe necks, which are less destructive and do not do strange things.

In any case, the researchers suggest that developing a robotic system with a practical combination of power, flexibility and control may be easier to do with a giraffe neck model than with an elephant trunk model. Some softness and flexibility can be sacrificed, and the system can actually be made to work so that it can apply the force needed for industrial applications.

The name of this robot is "Giraffe Neck Robot No. 1". Although it is not the most creative, it suggests that other robots will follow. Apparently, the next step will be to increase power by several orders of magnitude by using hydraulic rather than pneumatic actuators.

"This study aims to apply these superior characteristics of the giraffe's neck to developing robotic mechanisms. In particular, roboticists and zooanatomists joined forces to develop a powerful and flexible long skeletal-muscular robot based on the anatomy of the giraffe's neck. The skeletal-muscular robot prototype is driven by thin McKibben pneumatic artificial muscles, which bend easily. The results confirm the coordination between muscles and ligaments and the adaptability of shape to external force," the researchers said. 

Experimental results indicate that the scientists managed to achieve, in the robotic analogue, mechanisms that can provide power and flexibility similar to those of giraffes. Given that evolution has produced all the best engineering solutions over four billion years, scientists have no choice but to look for solutions to their problems in nature.