  Myoelectric prosthetic hands are intended to replace the function of the
amputee's lost arm. Therefore, developing robotic prosthetics that can mimic
not only the appearance and functionality of humans but also characteristics
unique to human movements is paramount. Although the impedance model was
proposed to realize biomimetic control, this model cannot replicate the
characteristics of human movements effectively because the joint angle always
converges to the equilibrium position during muscle relaxation. This paper
proposes a novel biomimetic control method for myoelectric prosthetic hands
integrating the impedance model with the concept of the $\lambda$-type muscle
model. The proposed method can dynamically control the joint equilibrium
position, according to the state of the muscle, and can maintain the joint
angle naturally during muscle relaxation. The effectiveness of the proposed
method is evaluated through simulations and a series of experiments on
non-amputee participants. The experimental results, based on comparison with
the actual human joint angles, suggest that the proposed method has a better
correlation with the actual human motion than the conventional methods.
Additionally, the control experiments showed that the proposed method could
achieve a natural prosthetic hand movement similar to that of a human, thereby
allowing voluntary hand opening and closing movements.
