The World Is Getting Closer to Flying Humanoid Robots. Why Does It Matter?

A few years ago, the Jet-HR1 biped robot was revealed, under development at Guangdong University of Technology. The robot had small fans mounted on its legs and could cross very large gaps by using the thrust from the fans to shift its center of gravity.

The Jet-HR1 weighed 6.5 kg and stood 65 cm tall. Each leg ended in a ducted fan jet unit weighing only 232 g, yet capable of producing 2 kg of thrust, which is almost a third of the robot's weight. In one experiment, the robot was tasked with stepping across a 37 cm gap. This required the step length to be 80% of the leg length.

The robot spun up the fan while extending a leg outward. The fan supported the leg and kept the robot from tipping forward. Once the jet-powered leg was on the far side of the gap, it repeated the procedure with the rear leg to complete the move. The entire process took less than a minute.

The researchers then suggested that this general method could be adapted to many more complex situations, helping robots maintain balance when facing large obstacles they need to step over, or simply keeping them from falling on rough terrain. Because the jet engines let the robot dynamically adjust its center of gravity without needing specific contact with the ground, you can imagine all kinds of crazy things it could do.

This is already impressive, but let's look at the next logical step and see what happens when these fans are spun up as high as they can go. Of course, this is only a first small test jump in the air, but by the end of the video it is clear that stabilization works very well. Although this is not a fully controlled process, the progress is already noticeable.

The Jet-HR2 humanoid robot was developed in 2019 to demonstrate the potential of jet propulsion for improving the locomotion of humanoid robots. When we use a humanoid robot in certain emergencies, we do not want it to climb stairs step by step to reach the site where the task must be performed.

The robot can use jet thrust to reach its destination faster, flying or jumping long distances to complete the task.

The Jet-HR2 has 10 degrees of freedom for ground movement, plus four ducted fans (two statically mounted on the robot's waist and two inside the feet) that can be driven by ankle movements. Each fan can produce 5 kg of thrust, for a total of 20 kg. That is more than enough to lift the 17 kg robot.

The thrust-to-weight ratio here is small, which is the core control challenge: without a lot of spare power, thrust must be distributed very carefully. However, the demonstrated system can effectively suppress tipping and rotation, resulting in a stable (though not fully controllable) flying humanoid robot.

There are not many strong reasons to build a humanoid robot. So what makes a flying humanoid robot truly useful? The scientists explained their view in a paper.

"Various humanoid robots for disaster response have recently been invented, with unique control theories and other mechanisms for overcoming rough terrain. Traditional humanoid robots overcame these obstacles by walking and climbing, but these strategies lack efficiency, especially in hazardous environments such as impassable obstacles and geological faults.

To carry out urgent tasks in complex real-world scenarios, humanoid robots are expected to have dynamic aerial skills: high or long jumps, short-distance flight, and hovering several times the length of their body," the researchers said.

They said the performance of humanoid robots still falls short of human levels, especially as mass increases. On the other hand, even at human levels, robots can seem helpless on loose, collapse-prone or rocky terrain.

This seems to be a limitation of using current actuators to generate force. In their study, the researchers developed a new humanoid robot that can fly using an exhaust fan propulsion system, to explore its potential value for search and rescue in difficult conditions.

Many may have anticipated this: robots for disaster relief and search and rescue tend to be a universal justification for strange mobility concepts without obvious applications. On the other hand, this is actually one reason why building a humanoid may be a good idea.

Having robots that can go where people go can be useful. Practical humanoid robots are very complex, but if they can fly, they will become incredibly useful.