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  1. This paper considers system identification for systems whose output is asymptotically periodic under constant inputs. The model used for system identification is a discretetime Lur’e model consisting of asymptotically stable linear dynamics, a time delay, a washout filter, and a static nonlinear feedback mapping. For sufficiently large scaling of the loop transfer function, these components cause divergence under small signal levels and decay under large signal amplitudes, thus producing an asymptotically oscillatory output. A leastsquares technique is used to estimate the coefficients of the linear model as well as the parameters of a piecewise-linear approximation of the feedback mapping.
  2. Self-excited systems arise in many applications, such as biochemical systems, mechanical systems with fluidstructure interaction, and fuel-driven systems with combustion dynamics. This paper presents a Lur’e model that exhibits biased oscillations under constant inputs. The model involves arbitrary asymptotically stable linear dynamics, time delay, a washout filter, and a saturation nonlinearity. For all sufficiently large scalings of the loop transfer function, these components cause divergence under small signal levels and decay under large signal amplitudes, thus producing an oscillatory response. A bias-generation mechanism is used to specify the mean of the oscillation. The main contribution of the paper is the presentation and analysis of a discrete-time version of this model.
  3. In some applications of control, the objective is to optimize the constant asymptotic response of the system by moving the state of the system from one forced equilibrium to another. Since suppression of the transient response is not the main objective, the feedback control law can operate quasistatically, that is, extremely slowly relative to the open-loop dynamics. Although integral control can be used to achieve the desired setpoint, three issues must be addressed, namely, nonlinearity, uncertainty, and multistability, where multistability refers to the fact that multiple locally stable equilibria may exist for the same constant input. In fact, multistability is the mechanism underlying hysteresis. The present paper applies an adaptive digital PID controller to achieve quasi-static control of systems that are nonlinear, uncertain, and multistable. The approach is demonstrated on multistable systems involving unmodeled cubic and backlash nonlinearities.
  4. To increase the number of minorities that enter highly demanding computing field, a conversational agent is being developed to serve as a supplemental virtual mentor for minority students pursuing the professoriate. As minority engineering and computing professoriate interest is limited in the literature, it is important to identify the level of interest and concerns minority students have in pursuing the professoriate. A survey was administered to undergraduate students at an HBCU enrolled in one of three computer science courses. The results identify likelihood of pursuing the professoriate, persuasive and discouragement themes for pursuing the professoriate, as well as frequently asked questions over several variables of the minority STEM professoriate experience. Questions and data on question type, grammar, syntax and word choice will be used to improve the knowledgebase of the virtual mentor.
  5. To increase the number of minorities that enter highly demanding computing field, a conversational agent is being developed to serve as a supplemental virtual mentor for minority students pursuing the professoriate. As minority engineering and computing professoriate interest is limited in the literature, it is important to identify the level of interest and concerns minority students have in pursuing the professoriate. A survey was administered to undergraduate students at an HBCU enrolled in one of three computer science courses. The results identify likelihood of pursuing the professoriate, persuasive and discouragement themes for pursuing the professoriate, as well as frequently asked questions over several variables of the minority STEM professoriate experience. Questions and data on question type, grammar, syntax and word choice will be used to improve the knowledgebase of the virtual mentor.
  6. Free, publicly-accessible full text available June 1, 2023
  7. Free, publicly-accessible full text available June 1, 2023