Kepler KEPLERGEAR

KEPLERGEAR is a proprietary linear actuator developed by Kepler Robotics that uses a planetary roller screw transmission instead of a conventional ball screw. It is deployed in the main load-bearing joints of the Forerunner K2 humanoid — thighs, calves and arms — where high axial stiffness, large force density and precise position control are required.

Construction and operating principle

A planetary roller screw replaces the recirculating balls of a ball screw with multiple threaded rollers orbiting a central screw shaft. The larger continuous contact area carries the load, yielding higher force density, greater axial stiffness and longer service life than a comparable ball screw of the same diameter. In KEPLERGEAR the mechanism is coupled with an electric motor that drives the screw, converting rotary motion into precise linear motion.

Reported parameters

• Peak axial thrust: 8,200 N (8.2 kN)
• Energy conversion efficiency: 81.3%
• Idle power consumption: near-zero (vendor claim for load-bearing linear actuators)
• Companion K2 rotary actuators: up to 200 N·m peak torque, 0.01° repeatable positioning accuracy

Application

KEPLERGEAR is part of the hybrid drivetrain of the Forerunner series — Kepler uses planetary roller screw linear actuators in high-load areas (thighs, calves, arms) and rotary actuators in joints such as shoulders and waist. According to the manufacturer, this layout enables the K2 robot to carry 15 kg per arm (30 kg total) and walk at up to 4 km/h; in July 2025 the K2 completed an 8-hour continuous livestream at WAIC 2025, demonstrating runtime comparable to a full industrial shift.

The component is part of Kepler's closed platform — it is not offered as a standalone catalogue product and no public datasheet PDF is available.