[Edaily Reporter Shin Yeong-bin ] KNR SYSTEMS Inc.(199430)announced on the 4th that it has completed the development of a high-torque “QDD (Quasi-Direct Drive) actuator” for use in the lower-body joints of humanoid robots and has begun preparations for its launch.

The QDD actuator is a drive unit that combines a motor with a low-reduction-ratio gear and is primarily used in the joints of humanoid and quadruped robots. The reduction gear serves to increase torque—the rotational force that moves the joint—while reducing the motor’s rotational speed.

The product incorporates “bidirectional drive gear (BGD)” technology into its composite planetary gear structure. It is designed so that when an external force is applied to the joint while the motor is moving it, the rotation is transmitted back toward the motor. The company explains that this ensures both reverse drive capability—which allows for flexible response to external forces—and the rigidity needed to withstand loads.

A humanoid robot’s hip, knee, and ankle joints must support the robot’s body weight and operational loads while also adapting to changes in the ground surface and external impacts. Conventional QDD actuators were often designed with low reduction ratios to ensure reverse drive capability, which created limitations: achieving high torque required larger motors and resulted in increased heat generation.

KNR SYSTEMS Inc. announced that by utilizing a composite planetary gear system, it has reduced the axial thickness and increased the reduction ratio by 2 to 4 times or more compared to conventional QDDs. The design is intended to maintain back-driving capability even at high reduction ratios, enabling its use in high-load operations and for shock absorption.

The product measures 110 mm in diameter and 83 mm in height, and weighs 1.76 kg. The rated torque that can be sustained during continuous operation is 121 Nm, and the peak instantaneous torque is 308 Nm.

Following its hydraulic actuators and hybrid actuators with a maximum torque of 1,600 Nm, KNR SYSTEMS Inc. has now developed this electric actuator. The company plans to expand its product portfolio to suit various robot platforms and application areas, and aims to establish a comprehensive actuator lineup encompassing hydraulic, hybrid, and electric types by 2027.

Kim Myung-han, CEO of KNR SYSTEMS Inc., stated, “We have once again demonstrated our capabilities in developing key robot components for next-generation humanoid robot lower-limb joints, where both high power and flexible shock compliance are required.” He added, “We will quickly establish a complete full lineup ranging from hydraulic to hybrid and electric actuators to transform into a comprehensive actuator specialist.”