Development of a Quadruped Robot System with Torque-Controllable Modular Actuator Unit

This article presents an overview of Artificial DIgitigrade for Natural Environments (AiDIN-VI), a force-controllable quadruped robot system with incorporated mandatory abilities of speed, efficiency, and mobility for providing real-world services. This article describes the design methodologies and principles employed to implement these requisite capabilities on a single robot platform; particularly, the torque sensing method, along with the components and modularization method of the torque-controllable actuator unit are elucidated herein. The developed robot platform is equipped with all necessary components, including onboard PCs (for motion generation and vision mapping), a battery, modular actuator units, a wireless network router, and a remote e-stop controller for autonomous and manual locomotion control. The robot is subdivided into joints, legs, and robots, and its performance is experimentally tested. The capability of the robot with regard to joint torque control ($\pm$70 Nm), leg force control (350 N along the z-axis), and robot (vertical loading 25 kg, pulling force 200 N) was experimentally verified, and locomotive performances (walk, pace, trot, and jump) on various terrains were executed. A maximum trot gait speed of 1.2 m/s was recorded, along with minimum costs of transport of 1.187 and 1.15 at a speed of 1.0 m/s and under loading conditions, respectively.