A new dual stack piezoelectric actuation device with improved performance

A new actuator design is introduced, which utilizes a pair of matching piezoelectric stack elements within the actuator housing. The stack elements are utilized in a mechanically opposing configuration and are electrically operated out-of-phase. Conventional piezoelectric stack actuators usually incorporate a compressive preload mechanism to protect the stack from tensile stresses. A common preload method is to incorporate a mechanical spring in parallel with the stack. However, the mechanical spring reduces the free stroke capabilities of the stack actuator. To demonstrate the performance advantages of the new concept, an analytical and experimental comparison study is conducted. The dual stack actuator is compared with two conventional internally preloaded single stack actuators in a parallel configuration, thus both actuator configurations are utilizing equivalent volumes of the piezoelectric material. The analysis indicates the dual stack actuator produces greater free stroke, output energy, and energy efficiency than two parallel single stack actuators. For experimental evaluations, a dual stack actuator and an internally preloaded single stack actuator are fabricated using the same materials, similar construction techniques, and the same piezoelectric stack elements. A testing procedure is formulated to determine the free stroke and blocked force of both actuators. Comparison of the experimental data reveals a number of performance advantages of the dual stack actuator over two traditional preloaded actuators in parallel: the free stroke is 1.3-1.2 times greater; the blocked force is 1.4-1.2 times greater; the output energy is 1.8-1.5 times greater; the specific output energy is 2.4-1.9 times greater; and the energy efficiency is 1.8-1.5 times greater.