Design and Development of the Linear Actuator for Enhanced Agility in Humanoid Robot

In this paper, we will discuss the development of linear actuators for agile humanoid robots. Most linear actuators have greater rigidity than rotary actuators and are configured to be used in high-load environments using large deceleration ratios or hydraulic systems. However, to apply the linear actuator to a very dynamic humanoid robot, in addition to the large rigidity capable of withstanding impact, it must satisfy requirements such as accurate speed control, low impedance force control, and high power density [1]. In partic-ular, for high-bandwidth force control, mechanical impedance in the joint stage must be minimized. To compensate for these shortcomings, this paper proposes a linear actuator that minimizes mechanical impedance and ultimately has excellent back-drive performance by directly fastening only ball screws with large screw gaps to high power density BLDC motors. Taking into account these characteristics, a linear actuator controller was designed and the performance and function of the controller were verified on the actual actuator. Finally, we demonstrate that it is optimized for humanoid robots with agile motor performance by applying linear actuators to the leg of humanoid robots for actual bipedal walking.