Development of a nonlinear viscoelastic actuator for mastication robot

在这项研究中，我们提出并证实了非线性粘弹性驱动器的咀嚼机器人的有效性。人体肌肉可以近似地建模为两个元件，即收缩元件和串联弹性元件。收缩元件包括弹性元件和粘性元件。在咀嚼食物的情况下，肌肉的刚度变得很高，我们针对肌肉的这些特性，设计并制作了一种机械非线性粘弹性驱动器。数学模型的建立：提出了A、B、C三种数学模型。A型为“X”型，B型为“<"型，C型为”<"型。我们证实了所有的数学模型的弹性非线性作为计算机模拟的结果。此外，通过计算机模拟证实了C型肌的非线性粘弹性，即力的增加与肌肉的伸长和收缩速度呈非线性关系。力学模型的建立：建立了"<"型力学模型。旋转阻尼器（粘性元件）与螺旋扭转弹簧（弹性元件）并联。通过附着肌腱牵引机器人下颌骨，将两个元件的旋转特性转化为非线性特性，并对所建立的力学模型进行了力-位移-速度特性的基础实验测量。所建立的力学模型的力-位移和力-速度特性均表现出力-位移-速度关系的非线性。

In this research, we have proposed and confirmed the effectiveness of a nonlinear viscoelastic actuator for a mastication robot. Human muscle can be approximately modeled as two elements, that is, a contraction element and a serial elastic element. The contraction element includes an elastic and a viscous element. In case of chewing a food, the muscle's stiffness becomes high We focused on these characteristics of the muscle, and designed and made a mechanical nonlinear viscoelastic actuator. Three research steps, development of mathematical models, development of a mechanical model, and basic experiment of the mechanical model were performed.Development of mathematical models : Three mathematical models, type A,B,and C have been proposed. Type A is 'X' shaped model, type B in '<' shaped model, and type C is '<' shaped model. We confirmed the elastic nonlinearity on all mathematical models as results of computer simulations. Furthermore, we confirmed the nonlinear viscoelasticity on type C by computer simulations, that is, the force increases in nonlinear to the elongation and the contraction velocity of the muscle.Development of a mechanical model : A '<' shaped mechanical model was made. A rotary damper (viscous element) was connected in parallel with a helical torsion spring (elastic element). These two elements' characteristics that they have rotary characteristics are transferred into nonlinear characteristics by the attached tendon that pulls robot's mandible.Basic experiment was performed to measure the force-displacement-velocity characteristic of the developed mechanical model. Both of the force-displacement and the force-velocity characteristics of the developed mechanical model showed the nonlinearity in force-displacement-velocity relationships.As conclusions, a nonlinear viscoelastic actuator that has a rotary damper and a helical torsion spring was developed.