A Design Method for Instantaneous Force Generation Based on a Mantis Shrimp With Exoskeleton Spring

Biological organisms face multiple requirements to survive in their environments. This article describes a design method for multiobjective optimization to construct a bioinspired robot that performs multisprings-driven fast movements by exploiting several mechanical elements, such as springs, latches, and linkages. To control the duration required for preparatory loading and unloading, it is important for this power-amplification system to design the parameters of independent springs acting in the translational and rotational directions of the joint and the inertia of the arm. In our previous study, we designed an antagonistic drive mechanism with the exoskeletal springs that realizes a motion far exceeding the muscle contraction. However, the modulus of two types of elastic elements and the arm inertia were not considered. Here, we numerically simulate and experimentally demonstrate the effects of the elastic modulus of the two types of springs acting in the translational and rotational directions of the joint and arm inertia on the duration and the maximum speed and shock absorption of the arm of the mechanism. The results reveal that the compression spring stiffness to 100 N/mm (mass: 0 kg), 1000 N/mm (0.20 kg), and 100 000 N/mm (0.40 kg) minimizes the impact duration to 0.06 s, 0.121 s, and 0.148 s. In addition, varying the compression spring stiffness from 14 to 20 N/mm maximizes the arm speed to 6.4 m/s (mass: 0 kg), 3.3 m/s (0.20 kg), and 2.9 m/s (0.40 kg). Interestingly, when the inertia was low, the arm vibrated for the modulus exceeding 0.2 N/mm, with the loading duration progressively increasing. Based on these findings, a model in the multisprings-driven mechanism was proposed.