SVPWM SWITCHING PATTERN FOR Z-SOURCE INVERTER, SIMULATION AND APPLICATION

The voltage source inverter (VSI) and current voltage source inverter (CSI) are widely used in industrial application. But the traditional VSIs and CSIs have one common problem: can’t boost or buck the voltage come from battery, which make them impossible to be used alone in Hybrid Electric Vehicle (HEV/EV) motor drive application, other issue is the traditional inverter need to add the dead-band time into the control sequence, but it will cause the output waveform distortion. This report presents an impedance source (Z-source network) topology to overcome these problems, it can use one stage instead of two stages (VSI or CSI + boost converter) to buck/boost the voltage come from battery in inverter system. Therefore, the Z-source topology hardware design can reduce switching element, entire system size and weight, minimize the system cost and increase the system efficiency. Also, a modified space vector pulse-width modulation (SVPWM) control method has been selected with the Z-source network together to achieve the best efficiency and lower total harmonic distortion (THD) at different modulation indexes. Finally, the Z-source inverter controlling will modulate under two control sequences: sinusoidal pulse width modulation (SPWM) and SVPWM, and their output voltage, ripple and THD will be compared.

Production of liquid core-polymer shell microcapsules

Polylactide (PLA) is a biodegradable polymer that has been used in particle form for drug release, due to its biocompatibility, tailorable degradation kinetics, and desirable mechanical properties. Active pharmaceutical ingredients (APIs) may be either dissolved or encapsulated within these biomaterials to create micro- or nanoparticles. Delivery of an AIP within fine particles may overcome solubility or stability issues that can result in early elimination or degradation of the AIP in a hostile biological environment. Furthermore, it is a promising method for controlling the rate of drug delivery and dosage. The goal of this project is to develop a simple and cost-effective device that allows us to produce monodisperse micro- and nanocapsules with controllable size and adjustable sheath thickness on demand. To achieve this goal, we have studied the dual-capillary electrospray and pulsed electrospray. Dual-capillary electrospray has received considerable attention in recent years due to its ability to create core-shell structures in a single-step. However, it also increases the difficulty of controlling the inner and outer particle morphology, since two simultaneous flows are required. Conventional electrospraying has been mainly conducted using direct-current (DC) voltage with little control over anything but the electrical potential. In contrast, control over the input voltage waveform (i.e. pulsing) in electrospraying offers greater control over the process variables. Poly(L-lactic acid) (PLLA) microspheres and microcapsules were successfully fabricated via pulsed-DC electrospray and dual-capillary electrospray, respectively. Core shell combinations produced include: Water/PLLA, PLLA/polyethylene glycol (PEG), and oleic Acid/PLLA. In this study, we designed a novel high-voltage pulse forming network and a set of new designs for coaxial electrospray nozzles. We also investigated the effect of the pulsed voltage characteristics (e.g. pulse frequency, pulse amplitude and pulse width) on the particle’s size and uniformity. We found that pulse frequency, pulse amplitude, pulse width, and the combinations of these factors had a statistically significant effect on the particle’s size. In addition, factors such as polymer concentration, solvent type, feed flow rate, collection method, temperature, and humidity can significantly affect the size and shape of the particles formed.

Adaptive control of sinusoidal brushless DC motor actuators

Electrical Power Assisted Steering system (EPAS) will likely be used on future automotive power steering systems. The sinusoidal brushless DC (BLDC) motor has been identified as one of the most suitable actuators for the EPAS application. Motor characteristic variations, which can be indicated by variations of the motor parameters such as the coil resistance and the torque constant, directly impart inaccuracies in the control scheme based on the nominal values of parameters and thus the whole system performance suffers. The motor controller must address the time-varying motor characteristics problem and maintain the performance in its long service life. In this dissertation, four adaptive control algorithms for brushless DC (BLDC) motors are explored. The first algorithm engages a simplified inverse dq-coordinate dynamics controller and solves for the parameter errors with the q-axis current (iq) feedback from several past sampling steps. The controller parameter values are updated by slow integration of the parameter errors. Improvement such as dynamic approximation, speed approximation and Gram-Schmidt orthonormalization are discussed for better estimation performance. The second algorithm is proposed to use both the d-axis current (id) and the q-axis current (iq) feedback for parameter estimation since id always accompanies iq. Stochastic conditions for unbiased estimation are shown through Monte Carlo simulations. Study of the first two adaptive algorithms indicates that the parameter estimation performance can be achieved by using more history data. The Extended Kalman Filter (EKF), a representative recursive estimation algorithm, is then investigated for the BLDC motor application. Simulation results validated the superior estimation performance with the EKF. However, the computation complexity and stability may be barriers for practical implementation of the EKF. The fourth algorithm is a model reference adaptive control (MRAC) that utilizes the desired motor characteristics as a reference model. Its stability is guaranteed by Lyapunov’s direct method. Simulation shows superior performance in terms of the convergence speed and current tracking. These algorithms are compared in closed loop simulation with an EPAS model and a motor speed control application. The MRAC is identified as the most promising candidate controller because of its combination of superior performance and low computational complexity. A BLDC motor controller developed with the dq-coordinate model cannot be implemented without several supplemental functions such as the coordinate transformation and a DC-to-AC current encoding scheme. A quasi-physical BLDC motor model is developed to study the practical implementation issues of the dq-coordinate control strategy, such as the initialization and rotor angle transducer resolution. This model can also be beneficial during first stage development in automotive BLDC motor applications.

MIMO waveform design using continuous phase modulation

Hybrid MIMO Phased-Array Radar (HMPAR) is an emerging technology that combines MIMO (multiple-in, multiple-out) radar technology with phased-array radar technology. The new technology is in its infancy, but much of the theoretical work for this specific project has already been completed and is explored in great depth in [1]. A brief overview of phased-array radar systems, MIMO radar systems, and the HMPAR paradigm are explored in this paper. This report is the culmination of an effort to support research in MIMO and HMPAR utilizing a concept called intrapulse beamscan. Using intrapulse beamscan, arbitrary spatial coverage can be achieved within one MIMO beam pulse. Therefore, this report focuses on designing waveforms for MIMO radar systems with arbitrary spatial coverage using that phenomenon. With intrapulse beamscan, scanning is done through phase-modulated signal design within one pulse rather than phase-shifters in the phased array over multiple pulses. In addition to using this idea, continuous phase modulation (CPM) signals are considered for their desirable peak-to-average ratio property as well as their low spectral leakage. These MIMO waveforms are designed with three goals in mind. The first goal is to achieve flexible spatial coverage while utilizing intrapulse beamscan. As with almost any radar system, we wish to have flexibility in where we send our signal energy. The second goal is to maintain a peak-to-average ratio close to 1 on the envelope of these waveforms, ensuring a signal that is close to constant modulus. It is desired to have a radar system transmit at the highest available power; not doing so would further diminish the already very small return signals. The third goal is to ensure low spectral leakage using various techniques to limit the bandwidth of the designed signals. Spectral containment is important to avoid interference with systems that utilize nearby frequencies in the electromagnetic spectrum. These three goals are realized allowing for limitations of real radar systems. In addition to flexible spatial coverage, the report examines the spectral properties of utilizing various space-filling techniques for desired spatial areas. The space-filling techniques examined include Hilbert/Peano curves and standard raster scans.