Unitree H1

A full-size humanoid from Unitree

H1 is a humanoid robot made by Unitree Robotics, a Chinese company. Unitree released H1 on 15 August 2023 and described it as China's first full-size general-purpose humanoid robot able to run^[2]. The published figures put it at about 180 cm tall and about 47 kg^[1], close to the size of an adult person.

That size is the point of the design. A machine built to human dimensions is meant to use staircases, doorways, tools and workstations that already exist, instead of requiring the environment to be rebuilt around it. Being light for its height also matters: every kilogram in a leg has to be lifted and swung again with each step.

Speed

The listed moving speed is 3.3 m/s, and the company gives potential mobility above 5 m/s^[1]. That is well beyond ordinary walking pace, and running is the capability Unitree singles out in its description of the machine^[2]. Higher speed is the hardest test of a legged robot, because the machine has to keep its balance while the feet touch the ground only briefly and the forces on the legs grow.

Actuators and joints

Behind the speed are the leg motors. Unitree lists a peak torque density of 189 N·m/kg and a maximum joint torque of 360 N·m^[1]. Torque is the turning force a joint can produce; torque density is that force divided by the mass of the actuator producing it. A high torque density means a joint can be powerful without being heavy, which is what allows a fast leg on a light body.

The torque is not spread evenly. Unitree gives roughly 360 N·m at the knee, about 220 N·m at the hip, about 59 N·m at the ankle and about 75 N·m at the arm joints^[1]. The knee is the strongest joint in the list, which fits its job: it has to straighten the leg and absorb the landing force of the whole body during running and jumping.

Degrees of freedom

Each leg has 5 degrees of freedom and each arm has 4, and the arm degrees of freedom can be expanded^[1]. A degree of freedom is one independent axis a joint can rotate or slide around, so the count is a rough measure of how many postures a limb can take. Splitting 5 degrees of freedom across a leg means the hip, knee and ankle together can place the foot at different positions and angles. The expandable arms leave room for hands or wrists with more movement than the base configuration provides.

Sensing and power

For perception, H1 carries a 3D LiDAR together with a depth camera, which Unitree describes as 360-degree depth sensing^[1]. LiDAR measures distance by timing laser pulses, while a depth camera produces a distance map of the scene in front of it; the two together give the robot a picture of how far away things are in every direction, which is the basis for walking without a human steering it.

The battery is listed at 864 Wh and 15 Ah at a maximum voltage of 67.2 V, and Unitree says it can be replaced quickly^[1]. Watt-hours measure stored energy, so the pack sets how long the robot can work between charges. A quickly replaceable pack changes how the machine is used in practice: instead of standing still while it charges, it can be put back to work by swapping in a fresh battery.

The H1-2 variant

Unitree also lists a second configuration, H1-2, at about 178 cm tall and about 70 kg, with 27 degrees of freedom and a maximum speed below 2 m/s^[1]. Compared with the base H1 it is heavier, has more joints and is slower. In other words, the catalogue offers two trade-offs: one machine tuned for speed and one with more articulation and a lower top speed.

Where it sits

H1 is a full-size humanoid rather than a small demonstrator, and the specifications Unitree publishes — top speed, torque density, a quickly swappable battery — are the ones that matter for legged locomotion. Together with the H1-2 configuration, they show a machine whose published design is organised around moving on two legs, carrying its own power and sensing its surroundings in all directions.