{"id":2425,"date":"2026-09-01T01:00:52","date_gmt":"2026-09-01T01:00:52","guid":{"rendered":"https:\/\/robotcncparts.com\/?p=2425"},"modified":"2026-10-21T07:45:48","modified_gmt":"2026-10-21T07:45:48","slug":"humanoid-robot-actuators","status":"publish","type":"post","link":"https:\/\/robotcncparts.sytech.site\/fr\/humanoid-robot-actuators\/","title":{"rendered":"Humanoid Robot Actuators: The Complete Engineering Guide"},"content":{"rendered":"

As the demand for humanoid robots grows, so does the importance of robot actuator design.<\/p>\n

In this guide, we’ll look at actuators, walking-related stresses, gear ratio, heat dissipation, controls, sensors, and the key considerations for optimal performance.<\/p>\n

What is a Robot Actuator?<\/h2>\n

Robot actuators are the mechanism responsible for causing motion in a robot. We use actuators to convert forms of energy like electricity into mechanical energy, which moves the joints, wheels, or any other movable part of the robot. They function as the muscles of a robot.<\/p>\n

Types of Humanoid Robot Actuators<\/h2>\n

\"Types<\/p>\n

Here are the two types of humanoid robot actuators:<\/p>\n

Rotary Actuators: The Rotating Joints<\/h3>\n

We use rotary actuators for joints requiring continuous rotation, such as the shoulder, hip, elbow, and wrist joints. These actuators comprise BLDC<\/a> motors along with the gear reducer, usually a harmonic drive with a ratio of 50:1\u2013160:1. This combination offers high torque in a compact design. They offer great accuracy but are more susceptible to shock loading.<\/p>\n

Linear Actuators: The Thrusting Joints<\/h3>\n

We utilize linear actuators for joints<\/a> that experience high loads, such as the knee and ankle joints. With the aid of a screw mechanism, like a planetary roller screw, these actuators convert the rotation of the motor into thrust and deliver forces in excess of 10,000 N.<\/p>\n

The Walking Problem: Why Humanoid Break Actuators<\/h2>\n

While working on actuators for humanoid robots, walking becomes one of the most complicated problems to be solved. Contrary to industrial machines that work in defined load conditions, humanoid actuators are subjected to thousands of impacts daily.<\/p>\n

When a robot performs about 5,000 steps hourly, it gets more than 40,000 load cycles during 8 hours of its work, which means that every step is followed by shock loads twice or even three times higher than the robot\u2019s weight. Repeated impacts soon show their negative effect on mechanisms of gears, bearings, and constructions.<\/p>\n

In our practice, the problem was not the generation of sufficient force or torque but high performance with low weight. Every extra kilogram makes every step harder.<\/p>\n

The Actuator Count: How Many Does It Take?<\/h2>\n

\"The<\/p>\n

It depends on the targeted capabilities of the robot; however, for a full-scale humanoid robot, we would need 40 to 55 actuators. Robots with extremely dexterous hands can have more than 70 actuators. However, in our opinion, what really matters is placing the proper actuator in the proper place.<\/p>\n

Legs<\/h3>\n

In our designs, we give the legs 12 to 14 actuators, with six to seven per leg. Three actuators operate the hip, one actuator operates the knee, and two to three actuators operate the ankle for balancing and foot movements. These joints are the most loaded; therefore, the actuator selection here has great importance for walking and durability.<\/p>\n

Arms<\/h3>\n

For the arms, we give 14 to 16 actuators or 7 to 8 actuators per arm. Three actuators operate the shoulder, one or two actuators operate the elbow, and two or three actuators operate the wrist. As a general rule, we prefer to use rotary actuators for manipulating tasks.<\/p>\n

Hands<\/h3>\n

In the hands, the actuators have the maximum density, with 10-20 actuators being common. However, even more actuators are used by some advanced humanoids. For example, Optimus Gen 3 from Tesla uses 25 actuators to realize 22 degrees of freedom with tendon drive in the hands.<\/p>\n

Torso and Neck<\/h3>\n

The actuator requirement for the torso and neck is in the range of 3 to 5 actuators. Though the number of actuators used is low, the joint is critical for balance and coordination of movements.<\/p>\n

The Pros and Cons of Gear Reduction<\/h2>\n

Gear reduction has a greater impact on actuator performance than engineers may realize at first. It affects not only the torque for each joint, but also its efficiency, speed, and reliability under real-world loads.<\/p>\n

Pros of Gear Reduction<\/h3>\n