Sliding Mode Control with Dynamical Correction for Time-Delay Piezoelectric Actuator Systems

In piezoelectric actuators (PEAs), which suffer from inherent nonlinearities, sliding mode control (SMC) has proven to be a successful control strategy. Nonetheless, in micropositioning systems with time delay, integral proportional control (PI), and SMC, feedback control schemes have a tendency to overcompensate and, consequently, high controller gains must be rejected. This may produce a slow and inaccurate response. This paper presents a novel control strategy that deals with time-delay micropositioning systems aimed at achieving precise positioning by combining an open-loop control with a modified SMC scheme. The proposed SMC with dynamical correction (SMC-WDC) uses the dynamical system model to adapt the SMC inputs and avoid undesirable control response caused by delays. In order to develop the SMC-WDC scheme, an exhaustive analysis on the micropositioning system was first performed. Then, a mixed control strategy, combining inverse open-loop control and SMC-WDC, was developed. The performance of the presented control scheme was analyzed and compared experimentally with other control strategies (i.e., PI and SMC with saturation and hyperbolic functions) using different reference signals. It was found that the SMC-WDC strategy presents the best performance, that is, the fastest response and highest accuracy, especially against sudden changes of reference setpoints (frequencies >10 Hz). Additionally, if the setpoint reference frequencies are higher than 10 Hz, high integral gains are counterproductive (since the control response increases the delay), although if frequencies are below 1 Hz the integral control delay does not affect the system’s accuracy. The SMC-WDC proved to be an effective strategy for micropositioning systems, dealing with time delay and other uncertainties to achieve the setpoint command fast and precisely without chattering.

THE MODEL OF SCATTERING OF NEUTRAL QUANTUM PARTICLE ON A NON-STATIONARY CURVE

The model describing the scattering of neutral quantum massive particle on the evolving curve has been constructed by methods of non-relativistic scattering theory. The first "dynamical" correction for scattering wave function has been calculated for the case of small non-stationary perturbation of straight line.

The Defect Identification of LED Chips Based on Bayesian Classifier

The types, causes and image properties of the defective and damaged chips are been analyzes. On the basis of analyzing the image properties, Bayesian classifier and identification method are proposed. Based on the Bayesian decision theory, five kinds of image features such as the number of light spot, dark spot, edge spot, block and area are applied. Normal distribution is made use to building classifier and studying the correction strategy of model. In the process of identification, dynamical correction and model parameters completion make the classifier have some degree of self-learning feature and higher identification accuracy. Keywords: defect; feature; classifier; decision