Smart composite material system with sensor, actuator and processor functions - A model of holding and releasing a ball

A composite material system has been constructed as an intelligent material or a smart material, which has three functions of sensor, actuator and processor. As an example to show functions of the composite material system, a model of holding and releasing an object, e.g. baseball, was constructed by using a carbon fiber reinforced plastic (CFRP) plate, two wires of Ti-Ni shape memory alloy (SMA), an optical sensor, a temperature sensor and a simple processor unit. Each SMA wire, which is 1 mm in a diameter and 120 mm in a length, has been memorized to be a semi-circle shape. Two SMA wires are sandwiched between a CFRP plate and an elastic rubber to form a shape of arch. These are combined with rubber glue to construct a composite material. A nichrome wire is rolled on each SMA wire in order to heat the SMA wire. The SMA heating provides a transformation of the composite material to be a closed shape of arch, and the composite material holds a baseball. After spontaneously cooling of the SMA wires, the composite material becomes to be an open shape of arch, and then the baseball is released. The composite material has a characteristic of reversible response with respect to temperature. A simple processor receives signals from the optical and temperature sensors and handles providing a current on the nichrome wires for SMA heating. The model can hold and release a baseball with consideration. Examples of the considerations are to recognize an existence of a baseball, to count the number of baseballs, to decide to hold a baseball, and so on. A calculation of the holding force for this model was performed, and that is consistent with the measurement.