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In this paper, a new model predictive control (MPC) approach suitable for high precision linear motion drive operating with repetitive tracking tasks is presented. For the proposed predictive controller, the feedforward controller of the conventional MPC has been modified to provide zero-phase learning property. This is achieved by augmenting the reference trajectory with a phase-compensated term that is updated with the historical tracking error. The proposed approach attempts to combine the merits of both the conventional MPC and repetitive control schemes. Experimental results have demonstrated that the system effectively reduces the tracking error from the periodic disturbance caused by the friction. Its performance under varying reference conditions and different loadings shows that the system is robust. Index Terms--Finite impulse response, friction compensation, linear motor, model predictive control (MPC), repetitive control.

Pulse design is investigated for time-reversal (TR) imaging as applied to ultrawideband (UWB) breast cancer detection. Earlier it has been shown that a suitably-designed UWB pulse may help to improve imaging performance for a single-tumor breast phantom with predetermined lesion properties. The current work considers the following more general and practical situations: presence of multiple malignancies with unknown tumor size and dielectric properties. Four pulse selection criteria are proposed with each focusing on one of the following aspects: eliminating signal clutter generated by tissue inhomogeneities, canceling mutual interference among tumors, improving image resolution, and suppressing artifacts created by sidelobe of the target response. By applying the proposed criteria, the shape parameters of UWB waveforms with desirable characteristics are identified through search of all the possible pulses. Simulation example using a numerical breast phantom, comprised of two tumors and structured clutter distribution, demonstrates the effectiveness of the proposed approach. Specifically, a tradeoff between the image resolution and signal-to-clutter contrast (SCC) is observed in terms of selection of the excitation waveforms. Index Terms--Breast cancer detection, pulse design, pulse shape, time-reversal (TR), ultrawideband (UWB) microwave imaging.

Uninterruptible power supplies (UPSs) have been used in many installations for critical loads that cannot afford power failure or surge during operation. It is often difficult to upgrade the UPS system as the load grows over time. Due to lower cost and maintenance, as well as ease of increasing system capacity, the parallel operation of modularized small-power UPS has attracted much attention in recent years. In this paper, a new scheme for parallel operation of inverters is introduced. A multiple-input-multiple-output state-space model is developed to describe the parallel-connected inverters system, and a model-predictive-control scheme suitable for paralleled inverters control is proposed. In this algorithm, the control objectives of voltage tracking and current sharing are formulated using a weighted cost function. The effectiveness and the hot-swap capability of the proposed parallel-connected inverters system have been verified with experimental results. Index Terms--Inverter, model predictive control (MPC), uninterruptible power supply (UPS).

This paper studies the possibility of distinguishing between benign and malignant masses by exploiting the morphology-dependent temporal and spectral characteristics of their microwave backscatter response in ultra-wideband breast cancer detection. The spiculated border profiles of 2-D breast masses are generated by modifying the baseline elliptical rings based upon the irregularity of their peripheries. Furthermore, the single- and multilayer lesion models are used to characterize a distinct mass region followed by a sharp transition to background, and a blurred mass border exhibiting a gradual transition to background, respectively. Subsequently, the complex natural resonances (CNRs) of the backscatter microwave signature can be derived from the late-time target response and reveal diagnostically useful information. The fractional sequence CLEAN algorithm is proposed to estimate the lesions' delay intervals and identify the late-time responses. Finally, it is shown through numerical examples that the locations of dominant CNRs are dependent on the lesion morphologies, where 2-D computational breast phantoms with single and multiple lesions are investigated. The analysis is of potential use for discrimination between benign and malignant lesions, where the former usually possesses a better-defined, more compact shape as opposed to the latter. Index Terms--Breast cancer detection, complex natural resonances (CNRs), lesion classification, lesion modeling, ultrawideband (UWB) microwave imaging.

A new microwave imaging method is given for breast tumor detection using an ultrawideband (UWB) imaging system. By combining the time of arrival (TOA) measurements from different sensors, the presence and location of small malignant lesions can be identified. At each sensor, the generalized sequence CLEAN (GS-CLEAN) algorithm is proposed to resolve the impulse response (IR) components into bins smaller than the duration of the sounding pulse. This novel deconvolution technique, working well with largely continuous image content, also solves an inverse problem to estimate the unknown tumors' morphological/dielectric properties and delay intervals. Subsequently, the TOA data fusion step is applied to obtain an estimate of the locations of dominant scattering sources such as cancerous tumors. We also apply the entropy-based approaches to collectively estimate the tumor morphological and electrical features based on the information acquired at various antenna elements. Preliminary two-dimensional (2-D) analysis and simulations demonstrate that the system developed is feasible to detect small breast malignant masses using this approach. Index Terms--Breast cancer detection, data fusion, statistical clutter modeling, time-of-arrival (TOA), two-dimensional (2-D) analysis, ultrawideband (UWB) microwave imaging.

In developing a hard disk drive servo system, there are multiple design control objectives to be met simultaneously. While some of the objectives are constraint objectives, others are simply optimization objectives. In this paper, we investigate a new multiobjective genetic algorithm (GA) for tuning servo controller parameters such that the resultant performance can satisfy all the desired requirements. Unlike the conventional single-objective GA, this new approach is able to place higher priority on the constraint objectives than the optimization objectives. Experimental results that are based on a commercial hard disk drive are presented. Index Terms--Genetic algorithms (GAs), hard disks, motion control, motor drive.

This paper proposes a new model for the pulsed neural network. In this model, the information is coded in terms of firing times of pulses that are generated by the neuron. The pulses transmit through the network and excite the dynamics of the neuron. Their synchronism is utilized to design the architecture of the neural network such that it acts as a radial basis function (RBF) network. A new network-learning algorithm is also developed for this pulsed RBF network. The RBF neurons are generated based on the feature of the training data, and the synaptic delays can be adjusted to distribute these RBF neurons in the training data space. The pulse neural network has been implemented compactly with multiplierless approach for both the forward computation and learning algorithm with a field programmable gate array board. As an application demonstration, it is extended to a nonlinear look-up table and applied to estimate the friction occurs in a precision linear stage. Index Terms--Field programmable gate array (FPGA), linear motors, pulsed neural network, radial basis function (RBF) neural network.

We conduct a two-dimensional study of pulse design for electromagnetic time-reversal (TR) imaging as applied to ultrawideband (UWB) breast cancer detection. We consider the situation when a tumor located in the human breast is surrounded by a large number of small tissue inhomogeneities that create strong signal clutter. When applying the TR algorithm, the excitation pulse should be properly designed such that there are distinguishable differences between the tumor and clutter responses. In this paper, we propose four pulse design criteria for the TR-based tumor detection. The modulated and modified Hermite polynomials (MMHPs) that fit well into the real pulse shapes are used as a general waveform template for the design process. Finally, numerical examples are used to demonstrate the usefulness of the proposed analytical framework. This paper can be a guide in the selection of suitable waveforms for which the tumor response can be enhanced and/or the clutter interference can be suppressed. The investigation is also well suited for applications to surface-penetrating radar using UWB signals. Index Terms--Breast cancer detection, pulse shape, time reversal, two-dimensional (2-D) model, ultrawideband (UWB) microwave imaging.

In this paper, a zero-phase odd-harmonic repetitive control scheme is proposed for pulse-width modulation inverters. The proposed repetitive controller combines an odd-harmonic periodic generator with a noncasual zero-phase compensation filter. It occupies less data memory than a conventional repetitive controller does. Moreover, it offers faster convergence of the tracking error, and yields very low total harmonics distortion (THD) and low tracking error. Analysis and design of the proposed system are presented. Experimental results with the proposed repetitive controller are presented to validate the approach. The phenomena of even-harmonic residues in the proposed control system is discussed and experimentally demonstrated. Index Terms--Even harmonic, odd harmonic, pulse-width modulation (PWM) inverter, repetitive control, zero phase compensation.

This paper presents the development of a single-phase ac power source, which is capable of generating high quality sinusoidal waveforms with adjustable amplitudes and frequencies over a wide range. Moreover, various types of arbitrary waveforms can also be generated. The system consists essentially of a well-controlled single-phase pulsewidth modulated inverter. To perform tight closed-loop control of the inverter, a digital controller based on the generalized predictive control approach has been developed. The controller gains are determined by minimizing a cost function that reduces both the tracking error and control signals. To evaluate the proposed approach, a digital-signal-processor-based experimental prototype has been constructed. Experimental results under various loading conditions have demonstrated that the system performs well. Index Terms: Power supplies, predictive control, pulsewidth modulated inverters.

This paper proposes a new control approach for a brushless dc motor drive using the generalized predictive control (GPC) algorithm. based on the same least-squares framework as in the controller design, we further develop the method to design an observer. The GPC algorithm uses the receding horizon approach whereby the control signals are determined by minimizing a quadratic cost function. Our study shows that the rise time and settling time of the servo system have an approximate linear relationship with the prediction horizon. Thus, it is used to tune the controller of the drive. Moreover, the control weighting factor can be used to smoothe the controller output. The proposed algorithm has been implemented using a digital signal processor (DSP) and tested in real time with a prototype system. The performance and robustness of the algorithms have been evaluated both in simulation and experiment. The results show that the drive performs reasonably well despite load changes and step changes in the position setpoint. Furthermore, it is fairly robust against motor parameters change.

In this paper, robust position control of a direct drive using a state space model predictive control (MPC) algorithm is presented. The proposed controller consists of a state feedback regulator and a feedforward controller. Their gains are obtained by minimizing a cost function that is a sum of the position tracking errors and the control cost over some user defined time horizons. The effects of the controller parameters on the dynamic performance and the robustness of the direct drive are investigated. To provide good estimates of the state variables in the presence of load disturbance, a new observer based on the receding horizon concept is also formulated. Experimental results are presented to demonstrate the effectiveness of the approach. Index Terms--Brushless rotating machines, observers, predictive control, robustness.