Kongjun Zhu

Semi-active Vibration Control of a Composite Beam using an Adaptive SSDV Approach

In this paper, an improved semi-active control method is proposed and applied to the vibration control of a composite beam. This method is an improved version of the previously developed SSDV (synchronized switch damping on voltage) approach. In SSDV, a voltage source is connected to the shunting branch, in series with the inductor, which can magnify the inverted voltage and hence improve the control performance. Optimization of the voltage source is an important issue in all SSDV techniques. In the proposed approach, called adaptive SSDV, the voltage coefficient that controls the damping effectiveness is adjusted adaptively. An improved switching algorithm, which prevents the switch from over-frequently switching on-and-off and accordingly improves the control performance, is also proposed. Compared with previous SSDV techniques, this adaptive SSDV is the most stable, is independent of the excitation level, and is more flexible because the voltage coefficient is adjusted adaptively to achieve optimal control performances. The adaptive SSDV has been applied to the vibration control of a composite beam and its control results were compared with those of previously developed SSDV techniques. The effectiveness of the new switching algorithm was also verified by comparing it with the conventional switch. An experimental setup of a semi-active control system for the cantilever composite beam was established, and control experiments were carried out using different SSDV methods.

Multi-modal vibration control using a synchronized switch based on a displacement switching threshold

A new semi-active method for multi-mode vibration control using the nonlinear synchronized switch damping (SSD) approach based on a displacement switching threshold is proposed in this paper. Several extensions of the SSD approach, including SSDI (SSD on inductance), SSDV (SSD on a voltage source), enhanced SSDV, and adaptive SSDV, have been developed to improve the control of the single-mode vibration, but the weakness of the SSD approach for multi-modal vibration control has not been solved. In all these extensions of the SSD approach, the switch is controlled by the same algorithm, that is, it reverses the voltage of the piezoelectric element at all extrema of displacement. This switching algorithm is effective in single-mode control, but it leads to over-frequent switching in multi-mode control. In the method proposed in this study, an improved switching algorithm based on a displacement threshold, which prevents the switch in the shunt circuit from over-frequent on-and-off actions and accordingly increases the converted energy to improve the control performance, is proposed. The switching algorithm is applied to an SSDI system and used in the vibration damping of a beam with two excited modes. Compared to the classical SSDI approach, the control performance of the first mode is improved from 3.7 to 18.2 dB, but that of the second mode is slightly worse, having changed from 3.46 to 2.6.

Tracking control of piezoelectric actuator system using inverse hysteresis model

The intrinsic hysteresis behavior of piezoelectric materi al limits the tracking control accuracy of the actuators. Th is paper describes a tracking control method for piezoelectric actuators based on the combination of feedforward and feedback loops. The hysteresis of piezoelectric actuators is linear ized in feedforward loop with an inverse hysteresis model based on a neural network. The number of parameters in the neural network based inverse model is relatively small and the parameters are easy to identify. The feedback loop is used to reduce the accumulated error produced by the inverse hysteresis model. The experimental results show that the accuracy is significantl y improved in tracking control by using the combination of feedback and feedforward control.

Metal core piezoelectric ceramic fiber rosettes for acousto-ultrasonic source localization in plate structures

This paper presents an approach for acousto-ultrasonic source (passive damage or impact) localization based on metal core piezoelectric fiber (MPF) rosettes. MPF is a new ty pe piezoelectric ceramic device with small size and has high directivity to sense Lamb waves. The response of surface-bonded MPF sensors to Lamb-wave fields is explored theoretical ly and experimentally. The good directional properties of MPF are used to determine the direction of propagation of the acoustic waves by mounting three MPF sensors in a rosette configuratio n. Two suitably spaced rosettes are used to locate the source of the ultrasound by taking the intersection of the directio n given by each rosette. The performance of the rosettes for source location is validated on an aluminum plate.

A semi-passive vibration damping system powered by harvested energy

This paper designs and investigates a vibration damping system powered by harvested energy with the implement of the so-called SSD (Synchronized Switch Damping) technique, which is a semi-passive approach. In the semi-passive approach, the piezoelectric element is switched from open circuit to closed circuit synchronously with the structure motion. Due to this switching procedure, a phase shift induced between the strain of vibration and the resulting voltage, thus creating energy dissipation. A low-power version of the switching circuit for nonlinear processing of voltage has been designed, and by combining the switching circuit with an energy harvesting subsystem, a semi-passive vibration damping system without external power supply has been successfully developed. Its effectiveness in the single-mode resonant damping of a composite beam is validated by the experimental results.

Self-powered structural vibration damping based on the self-sensing semi-passive technique

In the application of vibration damping systems using piezoelectric elements, there are three approaches: active control, passive control, semi-passive control. However, active approach has been limited by their requirement for complicated signal processing system and bulky power amplifier, and the passive vibration control systems are simpler, but they are sensitive to variation of the system parameters. In order to overcome these drawbacks, a new method of semi-active vibration control has been developed recently. In this paper, a self-powered version of the electronic nonlinear processing circuit has been successfully developed. By supplying the power collected from the piezoelectric materials to the switching circuit, the self-powered self-sensing vibration damping system suppress the vibration effectively by controlling the switch which switches turn on a shunt impedance for short periods, in accord with mechanical vibrations. Its effectiveness in the single-mode resonant damping of a steel beam is validated by the experimental results. The experimental results show that 7.89dB attenuation for the first mode was achieved. The total power dissipation of the control circuit is only 0.322mW.

Fabrication of lead-free barium titanate piezoelectric ceramics from barium titanate powders with different particle sizes synthesized by hydrothermal method

In this study, three types of BaTiO3 powders with different particle sizes synthesized by hydrothermal method were used to fabricate the lead-free barium titanate piezoelectric ceramics. The BaTiO3 ceramics from these three types of BaTiO3 powders were sintered at different temperature (1150-1350 ◦ C) using traditional sintering method, and their piezoelectric properties were investigated and compared. The results indicate that the BaTiO3 piezoelectric ceramics from BT03 powder exhibit highest d33 value (over 350 pC/N). The reasons were also investigated by comparing the properties of three kinds of BaTiO3 powders and their compacts sintered at different temperature.