Shape memory alloy actuators position

Materials that allow an intelligent or smart structure to adapt to its environment are known as actuators. These materials have the ability to change the shape, stiffness, position, natural frequency, damping, friction, fluid flow rate, and other mechanical characteristics of adaptronic structures in response to changes in temperature, electric field, or magnetic field. The most common actuator materials are shape memory alloys, piezoelectric materials, mag-netostrictive materials, electrorheological fluids, and magnetorheological fluids [2]. Actuators with these materials will be described in detail in Sects. 6.2 to 6.6 therefore you will find only a brief overview below. 

The installation of an additional position sensor is not always possible. Reasons may be costs and/or unavailable space. In this case, the internal sensoric effect displayed by some NiTiCu-alloys may be employed for indirect position sensing [84]. This leads to the use of a self-sensing actuator (cf. Sect. 6.9). In Fig. 6.58 the actuator length Ld of a NiTiCu shape memory wire is plotted against its electrical resistance Rd. The relation is free of hysteresis and is only slightly shifted by the actuators load. 

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