High-Speed Humanoid Robot Arm for Badminton Using Pneumatic-Electric Hybrid Actuators

We describe the development of a robot configured to play badminton, a dynamic sport that requires high accuracy. We used pneumatic-electric hybrid actuators, each combining a pneumatic actuator, with high-speed and lightweight attributes, and an electric motor with good controllability. Our first objective was to develop hybrid actuators that are lightweight and compact and with integrated sections. Using parts made of lightweight materials such as plastics and aluminum coils, and using wire for power transmission, we made actuators much lighter and smaller than previous ones. In addition, for high accuracy and power, tension sensor units and a heat countermeasure mechanism were also incorporated. As practice partners, we consider badminton robots to be more useful if they were humanoid in appearance and have a variety of shots. We, therefore, developed a humanoid robot arm. By incorporating actuators as link structures, the overall weight was reduced, and both complex degrees of freedom (DoFs) and a large range of motion were realized. Subsequently, we developed a robot with seven DoFs, three DoFs for the shoulder, two for the elbow, and two for the wrist, similar to the configuration of human arms. The robot, therefore, roughly reproduces human movements. At 19 m/s, the maximum speed of the racket was quite fast. The hybrid control reduced the motion variance, allowing improvements in accuracy of more than three times that of motions with only pneumatic control. In addition, performing path planning and tracking control with high precision was possible, tasks that are difficult for conventional pneumatic dynamic robots.