Penn State Altoona

Altoona, PA, United States

Penn State Altoona

Altoona, PA, United States
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Comanescu M.,Penn State Altoona
Proceedings of the IEEE International Conference on Industrial Technology | Year: 2017

The paper presents a method to estimate the inverse of the rotor time constant of the induction motor. The estimation is done using a sliding mode observer under the assumption that the stationary frame fluxes are known. These fluxes are first obtained using a voltage model observer; they are also used for field orientation. With measured voltages, currents, known fluxes and speed, the rotor time constant is estimated using a pseudo-MRAS sliding mode observer with dual feedback terms. The paper shows the design of this observer - this works well under ideal conditions. However, if the speed is inaccurate or if the magnetizing inductance saturates, the estimation accuracy suffers. The paper develops a model for the saturated induction motor and, using the equivalent controls that correspond to the sliding mode terms, attempts to estimate the saturation level - however, it is found that this is not possible. © 2017 IEEE.


Comanescu M.,Penn State Altoona
2014 International Symposium on Power Electronics, Electrical Drives, Automation and Motion, SPEEDAM 2014 | Year: 2014

The paper discusses the problem of estimating the speed, the flux magnitude and the rotor flux angle of the induction motor (IM) and presents an estimation method based on two Sliding Mode Observers (SMOs) and the Model Reference Adaptive System (MRAS) technique. The method is based on implementation of two SMOs that both yield the magnitude of the rotor flux; one observer is the reference model, the other is the adjustable model. The MRAS method is used to adapt the speed signal which is an input into both SMOs. The reference model is designed using the equations of the IM in the rotating reference frame. It is shown that its estimated flux magnitude is insensitive to the input speed. The adjustable model uses the IM equations in the stationary reference frame. Its output fluxes have magnitudes inverse proportional with the input speed; however, their phases are always accurate (this allows estimation of the flux angle). Using MRAS, the speed is corrected such that the flux magnitudes coming out of the two models match. Based on the structure developed, the paper also a speed estimation method. The simulations validate the theoretical development. © 2014 IEEE.


Comanescu M.,Penn State Altoona
Proceedings - ISIE 2011: 2011 IEEE International Symposium on Industrial Electronics | Year: 2011

The paper discusses the problem of integrating the equations of state observers associated with direct field orientation (DFO) of motor drives and studies the influence of the discretization method used on the accuracy of integration. In a typical implementation, discrete-time integration is done using Euler's discretization method (forward rectangular rule) - the method is simple and integration is accurate when the drive operates at low and medium speed. However, as the frequency increases, the integration becomes inaccurate because the Euler approximation starts losing more and more area from under the curve. Theoretically, the problem could be alleviated by increasing the sampling frequency; however, this cannot always be done. Another idea would be to adopt a more accurate (but more computationally intensive) integration method, for example, trapezoidal integration (Tustin method). The paper shows that, at high frequency, under ideal conditions, trapezoidal integration performs better than the Euler method. In a real implementation, however, conditions are non-ideal since the measured signals bring dc offsets and imperfections into the terms to be integrated - as a result, pure integration must be replaced with quasi-low pass filtering. Under these conditions, the paper compares the Euler, Tustin and backward rectangular methods from the point of view of integration accuracy. The implications related to direct field orientation of motor drives are studied by considering a full-order observer for the PMSM - this is discretized using the three methods considered and the results are compared. At high frequency, neither integration method gives perfect results; the Euler method yields a waveform that leads the expected one while the backward rectangular method yield a waveforms that lags it. The paper finds that, surprisingly, when quasi-low pass filtering is used, the Tustin method is not significantly more accurate than the other ones - the waveform obtained lags the expected one by an angle comparable with the lead angle of the Euler method. It is shown that the integration accuracy depends on the frequency, sampling time, filter bandwidth and on the integration method used. Accurate high frequency drive DFO control would require correction of the magnitude/phase of the estimates. © 2011 IEEE.


Comanescu M.,Penn State Altoona
IECON Proceedings (Industrial Electronics Conference) | Year: 2012

The paper discusses the problem of sensorless rotor flux angle/rotor position estimation for the permanent magnet synchronous motor (PMSM) and for the induction motor (IM) and presents a family of sensorless observer designs that use a speed estimate. In sensorless AC drive control, it is typical to measure the motor's voltages and currents and to estimate the other quantities of interest: speed, fluxes (EMFs) and rotor position. The simultaneous estimation of these quantities is possible, however, the methods available are rather complicated and the accuracy is often questionable, especially under parameter variations. The paper proposes a sequential approach which is simpler: first, estimate the drive's speed; then, use this speed estimate along with the measurements to estimate the states of the motor model and to obtain the field orientation angle. A family of observers for the IM and the PMSM is presented - these are constructed using their models in the stationary reference frame. The observers are developed assuming that the speed estimate obtained is different from the real speed; it is shown that despite this inaccuracy, with special gain designs, the correct field orientation angle is obtained. The observers are developed using Sliding Mode and/or Lyapunov methods. They can be directly applied in sensorless field-oriented drives that do not require the magnitude of the flux. © 2012 IEEE.


LaDage L.D.,Penn State Altoona
Integrative and Comparative Biology | Year: 2015

Synopsis Previous to the 1980s, the prevailing neuroscience dogma held that no new neurons were produced in the brains of adult mammals. Now, we understand that the production of new neurons, or neurogenesis, is a common and plastic process in the adult brain. To date, however, researchers have not come to a unified understanding of the functional significance of neurogenesis. Several factors have been shown to modulate hippocampal neurogenesis including spatial learning, stress, and aspects of environmental change, but questions still remain. How do these modulating factors overlap? Which aspects of environmental change induce a stress response? Is there a relationship between hippocampal neurogenesis, the stress response, and environmental change? Can this relationship be altered when taking into consideration other factors such as perception and predictability of the environment? Finally, do results from neurobiological research on laboratory rodents translate to wild systems? This review attempts to address these questions and synthesize research from the fields of ecology, psychology, and behavioral neuroscience.


Comanescu M.,Penn State Altoona
Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC | Year: 2016

The paper presents the design of a speed and flux observer for the sensorless induction motor (IM) drive. The design is based on the full-order model of the IM in the stationary reference frame. The proposed method consists of an observer with linear feedback that yields the motor fluxes and also estimates the speed using an adaptive law. Convergence conditions are formulated based on Lyapunov's nonlinear stability theory - the design of the feedback gains is done using Sylvester criterion. While this observer structure was discussed in the literature previously, the novelty of the method is given by the Sylvester criterion formulation - this uncovers interesting inequalities and offers insight into the design choices and stability margins of the observer. The method can be used to obtain the field orientation angle and speed needed in a sensorless IM drive. The theory is supported by simulations and experiments. © 2016 IEEE.


Comanescu M.,Penn State Altoona
Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC | Year: 2016

The paper presents a speed adaptive observer for the induction motor (IM) drive that can be used in a sensorless implementation. The observer is based on the model of the IM in the stationary reference frame: it uses linear feedback terms to estimate the fluxes and an adaptive law to estimate the speed. The feedback gains are designed using Lyapunov's nonlinear stability method. The investigation finds that the initial design only performs in limited speed range - as the speed increases, the speed estimate of the observer becomes inaccurate. Based on the initial design, the paper develops a hybrid observer: this uses a speed signal as an additional input (this input speed signal is relatively inaccurate - it can be an initial estimate of the motor speed or an estimate of the synchronous speed). It is shown that the hybrid design can be tuned to perform well in wide speed range: it yields relatively accurate estimates of the fluxes and speed. The theoretical developments are supported with simulations and experiments. © 2016 IEEE.


Comanescu M.,Penn State Altoona
IEEE International Symposium on Industrial Electronics | Year: 2010

The paper discusses the problem of rotor position estimation for the nonsalient permanent magnet synchronous motor (PMSM) and presents a Sliding Mode (SM) EMF observer that is based on the machine's model in the stationary reference frame. The speed of the PMSM which is an input of the proposed sliding mode observer is obtained from a speed estimator. The paper assumes that the speed estimate is different from the real speed and shows that the gains of the SM observer can be designed such that the EMF estimates produced by the SM observer tend to the real EMFs. The observer is designed and analyzed in the framework of nonlinear control using Lyapunov's theory and is validated using simulations. The method proposed is relatively simple and can be used to estimate the rotor position of the PMSM in a sensorless drive. © 2010 IEEE.


Comanescu M.,Penn State Altoona
IECON Proceedings (Industrial Electronics Conference) | Year: 2010

The paper presents an EMF and speed estimator for the nonsalient permanent magnet synchronous motor (PMSM). The method uses two cascaded sliding mode (SM) observers and is realized using only the measured voltages and currents of the motor. A first SM observer estimates the EMFs of the machine in the stationary reference frame. These EMFs are passed as inputs to a second SM observer that estimates the motor speed and reestimates the EMFs. The method is applicable in a sensorless PMSM speed control scheme where the estimated EMFs are used to obtain the rotor position and the estimated speed is used for speed feedback. The paper verifies the existence conditions of the sliding mode motion and proves the convergence of the observers. The theoretical findings are validated with simulation results that show that the estimated EMFs and speed are of good quality. The advantages of the proposed method compared to the state of the art are discussed. © 2010 IEEE.


Like a dependable flock of third-shift insect-control workers, little brown bats emerged from the wildlife educational center's bat boxes and fluttered in a cloud over the heads of the families pausing during night hikes to watch the show. This spectacle was a nightly summer tradition for thousands of area residents that rivaled drive-ins and double-headers. For the past few years, these families waited alone. During the last decade, a mysterious fungal disease has decimated much of the region's cave-dwelling bat populations, the once plentiful nocturnal master of the summer nights in the northeast, and cratered entire bat species. In some areas, colony populations fell 80 to 100 percent. Penn State researchers are still holding out hope that these mammals, often considered the official "spokescreature" of horror movies and spooky Halloween tales, won't remain forever relegated to the fringes of folklore and the recesses of the human imagination, but will be restored to the inky black night time skies and returned to their important ecological function. About 10 years ago, researchers documented the first case of the fungal disease—later dubbed white-nose syndrome (WNS)—affecting bats in New York, according to Michael Gannon, professor of biology at Penn State Altoona and one of the experts on the front lines of preserving the bat population. A few years later, millions of bats—including some of the area's most common, such as the little brown bat, the Indiana bat and the small-footed bat—were dead, and colonies of the area's leading consumer of insects and pests were whittled down to fractions of their former sizes. While the exact mechanism behind the disease is still unknown, researchers suggest that the white-nose fungus causes the cave-dwelling bats to wake early from their winter hibernation. Once roused, without any insects to feed on and facing cold winter temperatures, the bats starve to death or die from exposure. As a naturalist and program director at Shaver's Creek Environmental Center, Doug Wentzel witnessed the devastation of the bat population first-hand and, as an educator, continues to endure the aftereffects of one of the center's favorite exhibits. Wentzel began his career as an intern in 1990, when the center's little brown bat population thrived. The center even built bat boxes next to the bald eagle cage of Shaver's Creek's raptor center, to better incorporate the creature into the center's everyday educational programs. "In the summer of 1990, as an intern, I was treated to the joy of watching these bats come out of the bat boxes," said Wentzel. "Every summer during our Friday night campouts, people would gather and watch the bats stream out, which became a summer tradition at Shaver's Creek." In 2007, coincidentally just about the time white-nose syndrome began its deadly march through bat colonies, Shaver's Creek staff began to count their bats each year. In that year, there were 1,400 little brown bats. The next year there were 1,300. Wentzel then ticked off the population numbers, emphasizing how severe the effects of the syndrome were. In 2010, the center was down to 900 bats and in 2011, there were 151, he said. When the staff counted again in 2012, there were 69 bats, and they found only 9 in 2013. "Last year and this year, we have two bats," Wentzel added. "Part of Shaver's Creek mission is to connect people to the natural world and part of me feels like we just lost this ambassador for the natural world, this beautiful phenomena that kids at summer camp are going to miss out on." Losing bats—and their voracious appetites for insects—could cost Pennsylvania millions of dollars a year and result in billions of additional costs country-wide, according to Gannon, who has written several books about bats, including Bats of Pennsylvania. Each bat can eat about 3,000 insects every night. Without these flying pest-control workers on duty, federal and state agencies are expecting that 2.4 million pounds of insects, including many crop pests, will not get eaten—and, according to Gannon, that number does not include the millions of more pounds of offspring that these insects would have during the summer. Farmers would be expected to pick up the additional costs of insect control. Gannon added that each bat is worth approximately $74 each year to farmers who will now need to find insect-control alternatives. Some of those options to curb the insect population will not be the most environmentally friendly. "The bats provide what is essentially insect control, basically for free, but if they are not there, ultimately farmers will have to pay additional money for pesticides and, of course, there are all sorts of other problems associated with pesticides in the environment," said Gannon. Researchers nationally are investigating how to combat white-nose syndrome, including bat inoculation, hibernaculum disinfection and bacterial treatments, with some insights slowly gained. "We know more than we did ten years ago," said Gannon. "But I don't think the research is there, yet." Gannon said he has some concerns about plans to disinfect caves or inoculate bats, and if there may be unintentional negative effects to the environment. Nature and evolution are ultimately in charge of the recovery process, he added. Some bats have survived the disease, which may increase the likelihood that their offspring will also adapt. "At this point, I don't see that there's anything that we can do to alleviate this problem, other than to wait it out and hope for the best," he said. "The bats will eventually co-evolve with this and develop an immunity, or it would cause them to go into extinction." Regardless of these efforts, the level of decimation to the bat population is such that any recovery will be a long, slow process. "Even if they start recovering, we won't see the numbers the way they were for many, many years," said Gannon. "The reason for that is because bats only produce one offspring a year, so it takes a very long time for those numbers to increase again." If—or, let's be optimistic—when bats do return, Penn State experts hope that, in their absence, the hearts of many will have grown fonder for the once-maligned mammal. Once mistakenly feared as rabies-carrying, blood-sucking, possible vampires, bats are now more likely seen as a helper, and even beautiful, in a mouse-with-wings-and-claws kind of way. "Certainly a sad story, as bats were gaining in popularity, and people were putting up bat boxes," said Wentzel. "But, in the long view, maybe they will rebound and will be treasured more than ever before." What You Can Do To Help Explore further: Bat in your house? Don't touch it or kill it

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