This Small Business Innovation Research Phase I project concerns nonlinear modeling and control of Terfenol-D based actuators. Nonlinear models will be developed which will allow the design of control systems that extend the linear operating region of these materials. Although Terfenol-D is noted for large force and power densities, high stiffness, and the largest peak strain of all piezoelastic materials, the application of this material is limited by its inherent. nonlinear behavior. The nonlinearities result in higher harmonics when dynamic inputs are applied. These harmonics increase unwanted vibration and tracking error. Models will be derived using nonlinear magnetoelastic equations and lumped parameter modeling methods for magnetic, electrical, and mechanical subsystems. Hysteresis and saturation will be included in the nonlinear magnetoelastic equations. The resulting non linear dynamic model will be validated experimentally through open and closed loop control experiments. By extending the linear operating region, it is expected that harmonic content, and hence vibration and tracking error, will be reduced. Also a substantially higher force density will be achieved. This will result in the ability to design smaller, lighter, less expensive actuators for use in applications which demand precise positioning and/or extremely high force to weight ratios; such as, vibration and noise cancellation, high pressure pumps, and micropositioners. Development of the nonlinear controllers will allow up to a 50% increase in performance for dynamic applications, thus reducing size, mass and cost. As evidenced by the growing piezoelastic material market, commercial applications are increasing for these types of actuators. With twice the peak strain and an energy density of up to 15 times that of lead zirconate titanate (PZT), nonlinear control will allow these features to be used in a variety of dynamic applications. It is expected that Terfenol-D will replace other piezoelectric materials in rapid micropositioning, of large objects and vibration isolation.
