Kai Zhao
   - Single Actuator

Larry Funke
   - Multiple Actuators

Morphing Mechanisms Research

Shape-Changing Mechanisms with a Single Actuator

This work focuses on the development of synthesis theory to design both rigid and compliant mechanisms for a wide range of morphing applications.

A general synthesis procedure for planar shape-changing rigid-body mechanisms include segmentation and mechanization processes. The basic design strategy of segmentation is to divide a morphing curve into a morphing chain consisting of several rigid-body segments connected by revolute joints. Then, each segment of the morphing chain is regarded as part of an independent building block at the mechanization stage. The building blocks are located in an assembly position to generate a 1-DOF mechanism using a numerical optimization method. A genetic algorithm is employed to search the highly nonlinear design space and identify viable solution mechanisms by evaluating each candidate mechanism based on both the matching error and the mechanical advantage.

Example: Design of A Morphing Aircraft Wing using Rigid-Body Shape-Changing Mechanism

To generate a distributed compliant mechanism approximating a shape change, rigid-body mechanism topologies are employed here in a novel manner. The topology of a rigid-body solution mechanism is either directly evaluated via dimensional synthesis or else used to define an initial element network for an optimization to find solution compliant mechanism topologies and dimensions simultaneously. An improved design domain parameterization scheme that combines the ground structure and load path representation methods defines design variables for the optimization. A multi-objective genetic algorithm is employed to search the design space, and the deformation is evaluated using geometrically nonlinear finite element analysis.

Example: Design of Adaptive Antennas using Compliant Shape-Changing Mechanisms

Mechanism Approximating Two Open-Curve Profiles of an Adaptive Antenna

Mechanism Approximating Three Open-Curve Profiles of an Adaptive Antenna

Shape-Changing Mechanisms with Multiple Actuators

The theory developed by Kai Zhao for single actuator shape-changing mechanisms is being extended to include two and three actuator mechanisms by Larry Funke. The current approach is to design a four-bar subsystem and connect two or three of these together to obtain a two or three actuator system respectively. The use of these subsystems narrows the design space, but allows the actuator coordination problem to be solved analytically. The current solution to this problem is to run all actuators from the initial to final postion at the same time until the mechanism is within a certain threshold of a singularity. At that point, whichever combination of actuation moves the mechanism farthest from the singularity, while still moving towards the final position, is used until the mechanism is outside of this threshold again, or reaches its final position. Future work includes incorporating mechanical advantage and checking for links in the middle of the changing shape into the fitness function used by the genetic algorithm to find mechanisms. The use of Assur Class mechanisms will also be investigated. Using this class should help with certain limitations in the current approach, such as its inability to match certain profiles, but will likely come at the cost of significantly greater computation time since many of the equations involved cannot be solved analytically.

Good mechanisms have been found for both two and three actuator systems which can match either two or three target shapes. Videos of mechanisms matching three positions using two and three actuators have been made and are embedded below.

2 DOF mechanism matching 3 positions

3 DOF mechanism matching 3 positions

This video shows the same mechanism from two different points of view. The left window shows the entire mechanism, while the right side is zoomed in to show the target profiles more closely.

Journal Publications

Conference Publications