The human earcanal can accommodate several types of in-ear devices including hearing aids, earphones, hearing protectors, and earplugs. This canal-type home has a neighbor called the temporomandibular joint (TMJ) whose movements slightly deform the shape of the earcanal. While these cyclic deformations can influence the positioning, comfort, and functioning of ear-fitted devices, they can also provide a significant amount of energy to harvest. Given their importance, the TMJ movements and earcanal deformations have been well studied. However, their mutual actions are still not fully understood. This paper presents the development of a six-bar kinematic TMJ simulator capable of replicating the complicated motion of the jaw. The development relies on a two-phase mechanism design algorithm to numerically optimize and analytically synthesize linkage mechanisms for which the classical optimization approaches cannot return a converged solution. The proposed algorithm enables the design of a kinematic simulator to generate the TMJ path with an average error as low as 1.65% while respecting all the hinge-axis parameters of the jaw. This algorithm can be subsequently used to solve nonlinear complex linkage synthesis problems, and ultimately, the developed kinematic simulator can be used to further investigate TMJ–earcanal interactions.
Journal of Mechanisms and Robotics Open Issues