At present, cantilever structure used widely in civil structures will generate continuous vibration by external force due to their low damping characteristic, which leads to a serious impact on the working performance and service time. Therefore, it is very important to control the vibration of these structures. The active vibration control is the primary means of controlling the vibration with high precision and strong adaptive ability. Nowadays, there are many researches using piezoelectric materials in the structural vibration control. Piezoelectric materials are cheap, reliable and they can provide braking and sensing method harmless to the structure, therefore they have broad usage. They are used for structural vibration control in a lot of civil engineering research currently. In traditional sensor applications, information exchanges with the monitoring center or a computer system through wires. If wireless sensor networks(WSN) technology is used, cabling links is not needed, thus the cost of the whole system is greatly reduced.
Based on the above advantages, a wireless control system is designed and validated through preliminary tests. The system consists of a cantilever, PVDF as sensor, signal conditioning circuit(SCM), A/D acquisition board, control arithmetic unit, D/A output board, power amplifier, piezoelectric bimorph as actuator. DSP chip is used as the control arithmetic unit and PD control algorithm is embedded in it. PVDF collects the parameters of vibration, sends them to the SCM after A/D conversion. SCM passes the data to the DSP through wireless technology, and DSP calculates and outputs the control values according to the control algorithm. The output signal is amplified by the power amplifier to drive the piezoelectric bimorph for vibration control. The structural vibration duration reduces to 1/4 of the uncontrolled case, which verifies the feasibility of the system.
Piezoceramic based transducers are widely researched and used for structural health monitoring (SHM) systems due
to the piezoceramic material's inherent advantage of dual sensing and actuation. Wireless sensor network (WSN)
technology benefits from advances made in piezoceramic based structural health monitoring systems, allowing easy
and flexible installation, low system cost, and increased robustness over wired system. However, piezoceramic
wireless SHM systems still faces some drawbacks, one of these is that the piezoceramic based SHM systems require
relatively high computational capabilities to calculate damage information, however, battery powered WSN sensor
nodes have strict power consumption limitation and hence limited computational power. On the other hand,
commonly used centralized processing networks require wireless sensors to transmit all data back to the network
coordinator for analysis. This signal processing procedure can be problematic for piezoceramic based SHM
applications as it is neither energy efficient nor robust. In this paper, we aim to solve these problems with a
distributed wireless sensor network for piezoceramic base structural health monitoring systems. Three important
issues: power system, waking up from sleep impact detection, and local data processing, are addressed to reach
optimized energy efficiency. Instead of sweep sine excitation that was used in the early research, several sine
frequencies were used in sequence to excite the concrete structure. The wireless sensors record the sine excitations
and compute the time domain energy for each sine frequency locally to detect the energy change. By comparing the
data of the damaged concrete frame with the healthy data, we are able to find out the damage information of the
concrete frame. A relative powerful wireless microcontroller was used to carry out the sampling and distributed data
processing in real-time. The distributed wireless network dramatically reduced the data transmission between
wireless sensor and the wireless coordinator, which in turn reduced the power consumption of the overall system.