This paper introduces a new planar flexible hinge of fractal configuration to be incorporated in out-of-plane-motion compliant stages that cover a wide stiffness range. The large-displacement fractal hinge consists of a series of scaled-down, concentric, circular-axis flexible segments that are connected in a folded manner by radial rigid links. In-plane and out-of-plane compliance matrices are derived for fractal hinges with variable planar geometry features. The flexible hinges are assembled in a radial architecture to form compliant stages that can be utilized for piston-type, out-of-plane sensing or actuation. The analytical model calculates the stage active, out-of-plane stiffness, as well as its parasitic, in-plane stiffness. The stage analytical stiffness is confirmed by the experimental testing of a prototype and by finite element simulation. Furthermore, analytical-model simulation is performed to evaluate the variations in the active and parasitic stiffnesses with key geometric parameters, which also enables optimization.

The paper proposes a new three-dimensional flexible hinge formed of several serially linked straight- and circular-axis segments that are disposed of in two layers. The novel hinge configuration is capable of large displacements and can be implemented in precision-compliant mechanisms that need to cover large spatial workspaces. Based on simplified geometry, an analytical compliance model is formulated that connects the loads to the displacements at one end of the hinge. Finite element simulation and experimental prototype testing of actual-geometry hinge configurations confirm the analytical model predictions. A related compliance-based analytical model evaluates the maximum loads that can be applied to the hinge and the resulting displacements. The two small-deformation analytical models are subsequently utilized to investigate the relationship between geometric parameters and the hinge performance qualifiers.

One of the critical problems in the design of autonomous insects is power consumption. The independent control of several legs is energetically expensive, while the energy capacity of typical electrochemical batteries is quite small. The net result is autonomous robotic insects that have extremely limited range. The authors propose an alternative approach to this problem that enables autonomous robot insects that exhibit extremely high movement efficiency, and thus are capable of long range missions. Specifically, the desired limb motion is obtained by designing a lightly damped skeletal structure and exciting the skeletal structure at an appropriate resonance. The approach is called elastodynamic locomotion. Rather than altering the open-loop dynamics of the machine, as is the case with conventional-scale machine control, the control actuator serves only as an excitation source that excites the open-loop dynamics of the skeleton structure. Since the motion of the insect limbs operate at their structural resonance, the acceleration and deceleration for each motion (i.e.: stride for a walking machine) requires no power, which results in a highly efficient machine. Since the motion of the insect limbs is determined by design and not by control, the primary focus of this work is in the design of a skeletal structure that will exhibit walking motion when vibrationally excited. This paper presents various insect designs that will generate a walking or flying motion with minimal actuation.

A new lumped-parameter matrix method is proposed to model the decoupled, in-plane longitudinal and transverse free undamped vibrations of a collinear system with fixed ends and formed of two end flexible and prismatic members linked by a middle rigid connector. The method calculates the natural frequencies associated with the system’s three degrees of freedom by solving a linear algebraic characteristic equation related to the dynamic matrix, which is obtained from the system compliance and mass matrices. The linear, small-displacement model characterizes either long or short beams by adequately formulating the compliance and mass matrices. The lumped-parameter model is comprehensively validated by two separate distributed-parameter models, which determine the system’s longitudinal-vibration and long-beam, bending-vibration natural frequencies. Numerical simulations are performed with the lumped-parameter model to identify the sensitivity of the natural frequencies to system parameters variations and model variants. The system’s matrices are also utilized to perform frequency-domain analysis of the three-member system in a displacement/acceleration sensing application. The method can be adapted and expanded to describe more complex configurations with multiple, non-collinear, and non-prismatic members.