Using cyber-physical pitch-heave systems for both energy harvesting and propulsion*

We report on the use of a cyber-physical system to characterize and optimize the performance of both energy harvesting and propulsion modes using a pitch-heave hydrofoil in uniform flows. Expanding on previous work (e.g. Hover et al. 1997, Mackowski and Williamson 2011), a force-feedback cyber-physical system is used to achieve an elastically-mounted hydrofoil in which active kinematics and/or passive (mass-spring-damper) responses can be achieved in both heave and pitch. A wide range of parameters can be easily explored for use in both energy harvesting or propulsion applications. The system with a prescribed pitch motion and a passive heave motion is appropriate for energy harvesting and we identify the relationship between the forced pitch kinematics and the natural heave dynamics.  The effects of non-sinusoidal pitch dynamics, and nonlinear spring stiffness are reported.  Propulsion is achieved using active heave with a passive pitch response and the effects of non-sinusoidal kinematics and nonlinear structural dynamics for locomotion are also reported.