Shih-Ming Yang

Vibration Control of a Composite Plate with Embedded Optical Fiber Sensor and Piezoelectric Actuator

Smart structures, structures containing sensor(s) and actuator(s) along with computational and control capabilities, are considered one of the best candidates for vibration control applications. A [0/90]6s glass-fiber composite plate embedded with one optical fiber and six piezoelectric elements has been fabricated, analyzed, and experimentally validated. It is shown that by using the in-situ optical fiber as a Michelson interferometer to detect the structural displacement and the piezoelectric elements as actuator, bending vibrations of the composite laminated plate can be effectively reduced.

Development of a self-organized neuro-fuzzy model for system identification

It has been known that it is difficult to establish a fuzzy logic model with effective fuzzy rules and the associated membership functions. Neural network with its learning capability has been incorporated to make the fuzzy model more adaptive and effective. A self-organized neuro-fuzzy model by integrating the Mamdani fuzzy model and the back-propagation neural network is developed in this paper for system identification. The five-layer network adaptively adjusts the membership functions and dynamically optimizes the fuzzy rules. A benchmark test is applied to validate the model accuracy in nonlinear system identification. Experimental verifications on the dynamics of a composite smart structure and on an acoustics system also demonstrate that the neuro-fuzzy model is superior to the neural network and to an adaptive filter in system identification. The model can be established systematically and is shown to be effective in engineering applications.

Vibration Control of a Rotating Shaft: An Analytical Solution

It has been shown that a rotating shaft in the Rayleigh beam model has only a finite number of whirl speeds and vibration modes when the rotating speed is higher than half of the whirl speed. The systems unbalanced response can therefore be written analytically by the vibration modes and the generalized coordinates. This paper presents an analytical controller design of optimal sensor/actuator location and feedback gain for minimizing the steady-state unbalanced response. Because all of the critical speeds and vibration modes are included in the controller design, there will be no residual mode, hence no spillover. An example is used to illustrate that the controller design in collocated or noncollocated configuration not only guarantees the closed-loop stability but also effectively suppresses the unbalanced response.

On the Spillover of Steady State Unbalance Response of a Rotating Shaft Under Velocity Feedback

It has been stated that a uniform rotating shaft in the Rayleigh beam model has only a finite number of critical speeds and precession modes. This paper presents a controller design of optimal sensor/actuator location and feedback gain for steady state unbalance response of a rotating shaft operating in a speed range. For systems under order-limit constraint such that only part of the precession modes can be included in the reduced-order controller design, the system stability can be evaluated. The example of a hinged-hinged rotating shaft is employed to illustrate the controller design of velocity feedback in collocated and noncollocated senor/actuator configuration. Analyses show that the reduced-order controller not only guarantees the closed loop system stability but also effectively suppress the unbalance response.

Synthesis of Reference Signal in Adaptive Feedback Controller for Structure Vibration Suppression

Adaptive control has been known to be desirable to accommodate the system parameter variations and adapt to operational requirements in smart (intelligent) structures. Conventional feedforward controller requires both the reference sensor to measure the disturbance and the error sensor to measure the residual vibration; however, the reference sensor measurement may be impractical because the disturbance is often not known a priori in structural vibration. This study presents an adaptive feedback controller design in which the reference signal is synthesized by the error sensor measurement and the system dynamics identification, which is a prerequisite also in adaptive feedforward controller design. The infinite impulse response (IIR) adaptive filter for system identification and the finite impulse response (FIR) adaptive filter for feedback controller are implemented on digital signal processor for effective on-line vibration suppression. Experimental results show that the controller performance is strongly influenced by the accuracy of system identification. The controller achieves broadband attenuation and remains robust under parameter variations.

Design of quantum well thermoelectric energy harvester by CMOS process

This work aims at improving the energy harvester performance by using low-dimensional thermoelectric materials. A micro-thermoelectric generator with quantum well thermocouples is developed by state-of-the-art CMOS (Complementary metal-oxide semiconductor) process. A relaxation-time model is applied to analyze the characteristic length of silicon germanium quantum well, and a thermal model is also applied to calculate the thermocouple size for optimal performance by matching the thermal/electrical resistance. Analysis based on TSMC 0.35μm 3P3M (3-poly and 3-metal layers) BiCMOS process shows that the quantum well thermocouples (0.05 μm Si0.9Ge0.1 quantum well on 0.300 μm P-thermoleg and 0.280 μm N-thermoleg) has the best performance. that the power factor and voltage factor is 0.241 μW/cm2K2 and 10.442 V/cm2K.