Design, analysis and control of the series-parallel hybrid RH5 humanoid robot
This addresses the problem of bulky and limited humanoids for researchers and engineers in robotics, offering a novel hybrid design for improved performance, though it is incremental in combining existing methods.
The paper tackles the challenge of designing a high-performance humanoid robot by introducing the RH5, a 2 m tall, 62.5 kg series-parallel hybrid robot capable of dynamic tasks with 5 kg payloads per hand, using whole-body trajectory optimization and an improved DDP algorithm for stable walking.
Last decades of humanoid research has shown that humanoids developed for high dynamic performance require a stiff structure and optimal distribution of mass--inertial properties. Humanoid robots built with a purely tree type architecture tend to be bulky and usually suffer from velocity and force/torque limitations. This paper presents a novel series-parallel hybrid humanoid called RH5 which is 2 m tall and weighs only 62.5 kg capable of performing heavy-duty dynamic tasks with 5 kg payloads in each hand. The analysis and control of this humanoid is performed with whole-body trajectory optimization technique based on differential dynamic programming (DDP). Additionally, we present an improved contact stability soft-constrained DDP algorithm which is able to generate physically consistent walking trajectories for the humanoid that can be tracked via a simple PD position control in a physics simulator. Finally, we showcase preliminary experimental results on the RH5 humanoid robot.