Composed continuum mechanism for compliant mechanical postural synergy: An anthropomorphic hand design example

Continuum mechanisms have recently been used in various manipulator designs, often for medical applications. Instead of forming manipulators, a multi-backbone continuum mechanism, in a composed configuration, can be alternatively used as a transmission unit to generate an arbitrary number of translating outputs that are linearly combined from two independent inputs. This CCM (Composed Continuum Mechanism), applicable in other design scenarios, is applied as mechanical postural synergies of an anthropomorphic robotic hand. In this hand, three actuators actuate the CCM in its coordinated motion mode to drive the eleven hand joints according to two synergy inputs to form synergy-based hand poses in a pre-grasp phase. Then, the CCM closes the fingers in its synchronized motion mode. Joint-level compliance was selectively introduced based on a statics analysis to help achieve the stable grasping and pinching of many daily life objects. The compliance calculation, postural synergy synthesis, system descriptions and experimental characterizations of this hand with Compliant Mechanical Postural Synergy (the CoMPS hand) are expounded. The efficacy of the hand, demonstrated by the experimental results, can inspire its use as a prosthesis, as a training device for synergy control, or in a humanoid robot, showing the potentials of the proposed CCM.