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In this paper, we have presented an analytical solution to extract the effective properties of acoustic metamaterials from the measured complex transmission and reflection coefficients when the metamaterial and impedance tube have different sizes. We have first modeled this problem as a bilayer metamaterial located inside a duct and treated the air gap as a separate domain. Then we have mathematically proved that the effective properties of acoustic metamaterial can be obtained by solving a set of eight linear equations when the dimensions are known. Finally, we have evaluated the proposed method with results from numerical simulations. It is shown that the proposed method can calculate the effective refractive index and impedance with an error of below 1\%. This method provides an efficient approach to analyzing the effective properties of acoustic metamaterials of various sizes., Comment: 5 pages, 3 figures

Breaking reciprocity has recently gained significant attention due to its broad range of applications in engineering systems. Here, we introduce the first experimental demonstration of a broadband mechanical beam waveguide, which can be reconfigured to represent wave nonreciprocity. This is achieved by using spatiotemporal stiffness modulation with piezoelectric patches in a closed-loop controller. Using a combination of analytical methods, numerical simulations, and experimental measurements, we show that contrary to the conventional shunted piezoelectrics or nonlinearity based methods, our setup is stable, less complicated, reconfigurable, and precise over a broad range of frequencies. Our reconfigurable nonreciprocal system has potential applications in phononic logic, wave diodes, energy trapping, and localization.

We will report our efforts in designing feedback for the thruster-assisted walking of a bipedal robot. We will assume for well-tuned supervisory controllers and will focus on fine-tuning the desired joint trajectories to satisfy the performance being sought. In doing this, we will devise an intermediary filter based on the emerging idea of reference governors. Since these modifications and impact events lead to deviations from the desired periodic orbits, we will guarantee hybrid invariance in a robust fashion by applying predictive schemes within a short time envelope during the double support phase of a gait cycle. To achieve the hybrid invariance, we will leverage the unique features in our robot, i.e., the thruster., Comment: 7 pages, accepted in American Controls Conference (ACC) 2020

This paper proposes an adaptive neuro-fuzzy framework to improve drug infusion rate in closed-loop control of anesthesia. The proposed controller provides a sub-optimal propofol administration rate as input to reach the desired bispectral index, which is the output of the system, in both induction and maintenance phases. In this controller, a critic agent assesses the plant output and produces a reinforcement signal to adapt the controller parameters and minimize the propofol administration rate. The controller is applied to a conventional pharmacokinetic-pharmacodynamics model of anesthesia to evaluate its applicability in closed loop-control of anesthesia. To simulate the designed controller, physiological parameters of 12 patients are used in the mathematical model. The simulation results show that the proposed controller can overcome current challenges in the closed-loop control of anesthesia like inter patient variability, model uncertainties and surgical disturbances without overdose or underdose in a time range of 2 to 4 minutes. Analytical comparison of results shows the strength of the controller in closed-loop control of anesthesia., Comment: 10 pages, 11 figures

Over the past decade, there has been an unprecedented international focus on improved quality and availability of medical care, which has reignited interest in clinical automation and drawn researchers toward novel solutions in the field of physiological closed-loop control systems (PCLCs). Today, multidisciplinary groups of expert scientists, engineers, clinicians, mathematicians, and policy-makers are combining their knowledge and experience to develop both the next generation of PCLC-based medical equipment and a collaborative commercial/academic infrastructure to support this rapidly expanding frontier. In the following article, we provide a robust introduction to the various aspects of this growing field motivated by the recent and ongoing work supporting two leading technologies: the artificial pancreas (AP) and automated anesthesia. Following a brief high-level overview of the main concepts in automated therapy and some relevant tools from systems and control theory, we explore -- separately -- the developments, challenges, state-of-the-art, and probable directions for AP and automated anesthesia systems. We then close the review with a consideration of the common lessons gleaned from these ventures and the implications they present for future investigations and adjacent research., Comment: 39 pages, 13 figures

Two-wheeled inverted pendulum robots are designed for self-balancing and they have remarkable advantages. In this paper, a new configuration and consequently dynamic model of one specific robot is presented and its dynamic behavior is analyzed. In this model, two cantilever beams are on the two-wheeled base and they are excited by voltages to the attached piezoelectric actuators. The mathematical model of this system is obtained using the extended Hamilton's Principle. The results show that the governing equations of motion are highly nonlinear and contain several coupled terms. These complex equations are solved numerically and the natural frequencies of the system are extracted. The system is then simulated in both lateral and horizontal plan movements. This paper proposes a new model of two-wheeled two-flexible-beam inverted pendulum Robot and investigates its complex dynamic; however, the derived equations will be validated experimentally and a suitable control strategy will be applied to the system to make it fully automated and more applicable in the future works., Comment: 9 pages, 11 figures, journal