Design of active/passive hybrid compliance in the frequency domain-shaping dynamic compliance of humanoid shoulder mechanism

Design and control of mechanical compliance would be one of the most important technical foci in making humanoid robots really interactive with humans. For task execution and safety insurance the issue must be discussed and offers useful and realistic solutions. We propose a theoretical design principle of mechanical compliance. Passive compliance implies a mechanically embedded compliance in drive systems and is reliable but not tunable in nature, while active compliance is a controlled compliance and, therefore, widely tunable, but less reliable specially in the high frequency domain. The basic idea of the paper is to use active compliance in the lower frequency domain and to rely on passive compliance in the higher frequency. H_∞ control theory based on systems identification allows a systematic method to design the hybrid compliance in frequency domain. The proposed design is applied to the shoulder mechanism of a humanoid torso robot. Its implementation and experiments are to be shown with successful results