Experimental Dynamic Characterization of Rigid-Flex PCB Systems

Rigid-flex printed circuit boards (PCBs) are used in many applications that range from mobile electronic devices to low-volume medical tools. Rigid-flex PCBs in robotics allow for novel advances in robotic design. In many of these applications, it is critical to understand the system’s dynamics. Dynamic characterization of a rigid-flex system is difficult because the system exhibits large deformation in the joints, panel-to-panel contact, and other sources of dynamic nonlinearities and complexities not present in traditional PCBs. To date, rigorous test methods for the dynamic characterization of rigid-flex PCB systems have not been proposed. The objective of this paper is to present a nonlinear characterization and modal testing protocol for rigid-flex PCB structures that sufficiently characterizes the frequencies, mode shapes, damping, and nonlinear properties of the structure. To accomplish this, a variety of modal testing techniques historically used for nonlinear systems are examined to dynamically characterize a rigid-flex robotic system from NASA JPL, PUFFER (Pop-Up Folding Flat Explorer Robot). Based on the testing results, a modal testing procedure is proposed to most effectively identify the dynamic properties of rigid-flex PCB structures.