What Roles Do Different Lead Screws Play in Robots?

A lead screw is a mechanical drive device that converts rotary motion into linear motion, primarily consisting of a screw and a nut, which work through the matching principle of threads to achieve transmission. In the field of robotics, lead screws are widely used in joint motion control, precise positioning, and load transfer, providing accurate and reliable position control for robots, helping them achieve precise posture adjustments and motion path planning.

Lead screws are generally categorized into trapezoidal lead screws, ball screws, and planetary roller screws. In humanoid robots, different types of lead screws have slightly different applications: trapezoidal lead screws offer good stability and high load-bearing capacity, making them suitable for areas such as elbows and hips; ball screws feature high precision, efficiency, and speed, commonly used in areas requiring fast and precise movement, such as wrists and ankles; planetary roller screws are characterized by high precision, high load-bearing capacity, high rotational speed, and long lifespan, although they come at a higher cost.

1.Lead Screw

Characteristics of trapezoidal sliding lead screws include high transmission efficiency, stable operation, and easy maintenance. However, compared to other types of lead screws, they have lower precision and poorer load-bearing capacity.

2.Ball Screw

Ball screws are widely used in humanoid robot manufacturingcfor joint transmission. Their core components include the screw, nut, balls, and retainer. By precisely controlling the movement of the ball screw, humanoid robots can adjust their posture, maintain balance, and accurately control end-effectors such as hands and feet. Ball screws feature high transmission accuracy, low friction resistance, high transmission rigidity, long service life, and reversibility, making them highly applicable in industrial automation and precision machinery fields.

3.Planetary Roller Screw

Planetary roller screws primarily consist of a lead screw shaft, nut, and multiple roller bodies. Unlike ball screws, they utilize threaded rollers. The main advantages of planetary roller screws are high load capacity and long lifespan, with an applicable load approximately 3-5 times that of standard ball screws and a lifespan up to 15 times longer. This results in significantly increased stability for products or machines, reduced maintenance costs, and minimized downtime, making them ideal for future widespread applications in humanoid robots. Although their manufacturing cost is relatively high, efforts have been made to reduce it, making them more affordable for many users.

Planetary roller screws can be categorized into five types based on functional characteristics: standard, reverse, recirculating, differential, and bearing types, each suited for specific working methods and applications.

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