Optimal joint placement and modal disparity in control of flexible structures

Joints with variable stiffness are used to introduce modal disparity in a frame structure. The joint stiffness can be set at two distinct values and thus the structure can be characterized by two stiffness states. The placement of a small number of these joints on the structure is optimized to achieve a maximum measure of modal disparity. This allows the migration of vibration energy from modes that are not controlled to modes that are, and facilitates the design of simpler and less expensive controllers. An example 3D frame is used for illustration.