A Curved Compliant Differential Mechanism With Neutral Stability

Abstract

Differential mechanisms are remarkable mechanical elements that are
widely utilized in various systems; nevertheless, conventional
differential mechanisms are heavy and difficult to use in applications
with limited design space. This paper presents a curved differential
mechanism that utilizes a lightweight, compliant structure. This
mechanism acquires its differential characteristic by having a high
rotational stiffness when the mechanism is symmetrically actuated on two
sides, while having a low rotational stiffness when actuated only on
one side. To make the mechanism neutrally stable, the intrinsic elastic
strain energy required for deformation of the compliant differential is
compensated for by the reintroduction of potential energy, which is
provided by two preloaded springs. The rotational stiffness of the
one-sided actuation of the compliant differential mechanism around the
neutral position is hypothesized to be adjustable by changing the
preload of the springs. The stiffness can be positive, zero, or
negative, indicating that the mechanism can be neutral or bistable. This
hypothesis is investigated using a simulated model in Ansys Parametric
Design Language (APDL) using optimized parameters to achieve the desired
stiffness for the mechanism. The simulated model is validated using an
experimental setup for both the one-sided and symmetrical actuation
stages. The experimental results showed a high correlation with the
simulation results. The mechanism with optimized dimensions and preload
demonstrated neutral stability over a 16deg
range. Bistability was discovered for preloads greater than the
optimized preload. At θ = 0, a linear relationship was discovered
between the spring preload and the rotational stiffness of the
mechanism. Furthermore, an output/input kinematic performance of 0.97
was found for the simulated results and 0.95 for the experimental
results.