A structural optimization method of actuators and sensors composed of piezoelectric・piezoresistive materials and flexible structures

Piezoelectric materials can convert electric energy into mechanical energy, and vice versa. When traction is applied to the surface of a piezoelectric device, an electric potential is obtained. Conversely, when an electric charge is applied to the surface of a piezoelectric device, a mechanical deformation is obtained. In contrast, piezoresistive materials exhibit changes in their electrical resistivity in response to changes in mechanical strain. When either of such materials are utilized as actuators and sensors, the device works in concert with a flexible structure in order to provide the deformation in the specified direction and to magnify the deformation in the case of actuator designs, and to specify the deformation to be measured and to obtain a sufficient degree of sensitivity in the case of sensor designs. Such actuators and sensors are usually designed using a trial and error approach, and an integrated optimization method for their design has yet to be established. In order to overcome this problem, an integrated optimum design method for the design of flexible structures incorporating piezoelectric or piezoresistive materials was constructed, based on the concept of topology and multi-objective optimizations. In the first stage of this research, a structural optimization method for the design of actuators using piezoelectric materials was developed. First, the design specifications were clarified and the objective functions satisfying the required specifications were formulated. A multi-objective optimization problem was formulated for use in finding an optimal structure that incorporates all the design specifications. An optimization algorithm was then constructed and several design examples were presented to confirm the utility of the proposed method. The developed method was extended to the design of actuators capable of performing multiple actuations. Several actuator prototypes were developed, and their performance was confirmed by experiments. For the second stage of this research, a structural optimization method for the design of sensors using piezoresistive materials was developed. In these design cases, the design specifications were also clarified first and objective functions satisfying the required specifications were then formulated. A multi-objective optimization problem was also formulated for use in finding an optimal structure incorporating all the design specifications. An optimization algorithm was constructed, and several design examples were presented to confirm the validity of the proposed method.