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### Research Papers

J. Dyn. Sys., Meas., Control. 2019;141(5):051001-051001-13. doi:10.1115/1.4042090.

This research was carried out based on the significance of protecting the environment by preventing the contamination of water caused from effluents discharge from dyeing industries, effective nanocomposite were prepared to solve this problem. The poly(azomethine), ZnO, and poly(azomethine)/ZnO nanocomposites were prepared and characterized by Fourier transform-infrared spectroscopy, ultraviolet (UV)–visible spectroscopy, powder X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDAX), scanning electron Microscope (SEM), and transmission electron microscopy (TEM) techniques. Methylene blue (MB), Malachite green (MG), and Bismarck brown (BB) were degraded from water using poly(azomethine) (PAZ), zinc oxide (ZnO), PAZ/ZnO (PNZ) nanocomposites as photocatalyst in the presence of natural sunlight. The degradation efficiency and reaction kinetics were calculated, and the outcome of the photocatalytic experiments proved that the PAZ/ZnO nanocomposites reveals excellent photocatalytic activity and effective for decolorization of dye containing waste water than PAZ and ZnO in the presence of natural sunlight. The maximum degradation efficiency 97%, 96%, and 95% was obtained for PNZ nanocomposites at optimum dosage of catalyst as 500 mg and 50 ppm of MB, MG, and BB dye concentration, respectively. The maximum degradation time was 5 h. After photocatalytic study, the samples were characterized by Fourier-transform infrared spectroscopy (FT-IR) and UV–visible spectroscopy.

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 2019;141(5):051002-051002-14. doi:10.1115/1.4042133.

This paper demonstrates the ride comfort and road holding performance enhancement of the new road vehicle series active variable geometry suspension (SAVGS) concept using an $H∞$ control technique. In contrast with the previously reported work that considered simpler quarter-car models, the present work designs and evaluates control systems using full-car dynamics thereby taking into account the coupled responses from the four independently actuated corners of the vehicle. Thus, the study utilizes a nonlinear full-car model that represents accurately the dynamics and geometry of a high performance car with the new double wishbone active suspension concept. The robust $H∞$ control design exploits the linearized dynamics of the nonlinear model at a trim state, and it is formulated as a disturbance rejection problem that aims to reduce the body vertical accelerations and tire deflections while guaranteeing operation inside the existing physical constraints. The proposed controller is installed on the nonlinear full-car model, and its performance is examined in the frequency and time domains for various operating maneuvers, with respect to the conventional passive suspension and the previously designed SAVGS $H∞$ control schemes with simpler vehicle models.

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 2019;141(5):051003-051003-9. doi:10.1115/1.4042253.

This paper develops a new computational approach for energy management in a hydraulic hybrid vehicle. The developed algorithm, called approximate stochastic differential dynamic programming (ASDDP) is a variant of the classic differential dynamic programming algorithm. The simulation results are discussed for two Environmental Protection Agency drive cycles and one real world cycle based on collected data. Flexibility of the ASDDP algorithm is demonstrated as real-time driver behavior learning, and forecasted road grade information are incorporated into the control setup. Real-time potential of ASDDP is evaluated in a hardware-in-the-loop (HIL) experimental setup.

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 2019;141(5):051004-051004-12. doi:10.1115/1.4042196.

Model predictive control (MPC) has drawn a considerable amount of attention in automotive applications during the last decade, partially due to its systematic capacity of treating system constraints. Even though having received broad acknowledgements, there still exist two intrinsic shortcomings on this optimization-based control strategy, namely the extensive online calculation burden and the complex tuning process, which hinder MPC from being applied to a wider extent. To tackle these two drawbacks, different methods were proposed. Nevertheless, the majority of these approaches treat these two issues independently. However, parameter tuning in fact has double-sided effects on both the controller performance and the real-time computational burden. Due to the lack of theoretical tools for globally analyzing the complex conflicts among MPC parameter tuning, controller performance optimization, and computational burden easement, a look-up table-based online parameter selection method is proposed in this paper to help a vehicle track its reference path under both the stability and computational capacity constraints. matlab-carsim conjoint simulations show the effectiveness of the proposed strategy.

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 2019;141(5):051005-051005-11. doi:10.1115/1.4042146.

For gasoline engine with an exhaust gas recirculation loop, a challenging issue is how to achieve maximum brake efficiency while providing the desired torque. This paper presents a solution to this challenging issue via dynamical control approach which consists of two phases: optimal equilibrium point generation and feedback regulation of the optimized operating mode. First, a mean-value model is developed to represent the dynamical behavior of the intake manifold and exhaust manifold focused on gas mass flows. Then, the control scheme is constructed based on the control-oriented model. Mainly, the optimal set-points are designed by solving the optimal programming problem of maximizing the brake efficiency under demand torque constraint which is the first control design stage, and the dynamical model to the feedback stabilization regulation control for improving transient performance is at the second stage. Lyapunov-based design is used for the derivation of the state feedback law. Furthermore, the proposed exhaust manifold pressure estimator is also coupled into the controller to replace the cost prohibitive exhaust pressure sensor. Finally, experimental validations on the test bench are provided to evaluate the proposed controller.

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 2019;141(5):051006-051006-11. doi:10.1115/1.4042252.

In-cylinder pressure is a critical metric that is used to characterize the combustion process of engines. While this variable is measured on many laboratory test beds, in-cylinder pressure transducers are not common on production engines. As such, accurate methods of predicting the cylinder pressure have been developed both for modeling and control efforts. This work examines a cylinder-specific pressure model for a dual fuel compression ignition engine. This model links the key engine input variables to the critical engine outputs including indicated mean effective pressure (IMEP) and peak pressure. To identify the specific impact of each operating parameter on the pressure trace, a surrogate model was produced based on a functional Gaussian process (GP) regression approach. The pressure trace is modeled as a function of the operating parameters, and a two-stage estimation procedure is introduced to overcome various computational challenges. This modeling method is compared to a commercial dual fuel combustion model and shown to be more accurate and less computationally intensive.

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 2019;141(5):051007-051007-12. doi:10.1115/1.4042145.

Theoretical and experimental modal analyses are treated for hydraulic systems modeled by discrete capacities, inductances, resistances, and fluid lines with dynamic laminar flow. Based on an approximate multi-degrees-of-freedom description, it is shown how hydraulic natural frequencies, damping ratios, and mode shapes can be identified from measured frequency response functions between flow rate excitation and pressure response. Experiments are presented for a pipeline system that includes three side branches and an accumulator. In view of practical applications, two different types of servovalve excitation as well as impact hammer excitation are considered. Pressure is measured by 19 sensors throughout the system. Results are compared in terms of frequency response functions between 50 and 850 Hz, the first five hydraulic modes, and weighted auto modal assurance criteria of experimental mode shapes. Out of the tested excitation devices, the servovalve is clearly preferred; if valves cannot be used, the impact hammer offers a reasonable workaround. For a reduced number of five sensors, different sensor arrangements are assessed by the respective weighted auto modal assurance criteria of experimental mode shapes. A theoretical hydraulic modal model provides a similar assessment. The quality of the theoretical model is confirmed by the weighted modal assurance criterion of theoretical and experimental mode shapes from servovalve excitation.

Commentary by Dr. Valentin Fuster