Development of very high force hydraulic McKibben artificial muscle and its application to shape-adaptable power hand

By applying ultra high strength PBO fiber sleeves to McKibben artificial muscle, new hydraulic artificial muscles have been developed. While conventional McKibben muscles are driven by maximum pneumatic pressure of 0.7 MPa, the newly developed muscles are driven by water hydraulic of maximum pressure of 4 MPa, resulting in very high force capability. This paper shows the new artificial muscle, its performance and application to shape-adaptable power hand. The developed muscles were evaluated by four parameters, namely force density per volume (FDV), force density per mass (FDM), energy density per volume (EDV) and energy density per mass (EDM) for comparisons with other conventional linear actuators. The prototype artificial muscle, which is 40 mm in diameter and 700 mm in length can achieve the maximum contracting force of 28 kN, FDV of 32.3×10^-3 N/mm³, FDM of 9.44×10³ N/kg, EDV of 2600×10^-3 J/mm³ and EDM of 762×10³ J/kg. These values are 1.7 to 33 times larger than these of the typical conventional actuators. The developed muscles have been applied to a power hand which has shape adaptability to grasped objects. This hand can generate high force and grasp objects, which weighs about 230 kg both in horizontal and vertical direction.