An Inductive Power Transfer System for Powering Wireless Sensor Nodes in Structural Health Monitoring Applications

Inductive power transfer (IPT) has been extensively used to power the sensor nodes embedded into reinforced concrete structures for structural health monitoring (SHM) applications. Due to high dielectric absorption in concrete and hysteresis loss and eddy current loss in reinforced steel, this approach suffers from heavy attenuation and short transmission distance. To tackle the issue, a multicoil inductive power repeater system is proposed, in which the coil not only performs as a power relay but also supplies energy to the local load. Based on the physical model of multicoil coupling, the equivalent circuit is built. The effect of various design parameters (e.g., operating frequency, concrete strength, moisture, and steel types) on the power transfer capability of the proposed IPT system is investigated. A flexible design method using coupling modulation is proposed to achieve equal power distribution among various power relay circuits. Experimental results show that the proposed method can simultaneously provide equal power of 0.6 W to four local loads embedded into reinforced concrete structures with a power variation of less than 7.2%. The IPT system achieves a long distance of 51.5 cm and an efficiency of 47.7%. The results indicate the feasibility of the proposed design method in SHM applications.