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IN THIS ISSUE

### Research Papers

J. Dyn. Sys., Meas., Control. 2016;138(10):101001-101001-11. doi:10.1115/1.4033414.

In this paper, a novel direct adaptive fuzzy moving sliding mode proportional integral (PI) tracking control of a three-dimensional (3D) overhead crane which is modeled by five highly nonlinear second-order ordinary differential equations is proposed. The fast and robust position regulation and antiswing control can be achieved based on the proposed approach. Due to universal approximation theorem, fuzzy control provides nonlinear controller, i.e., fuzzy logic controllers, to perform the unknown nonlinear control actions. Simultaneously, in order to achieve fast and robust regulation and to enhance robustness in the presence of disturbance and parameter variations, moving sliding mode control (SMC) is introduced to tradeoff between reaching phase and sliding phase. Hence, the sliding surface is moved by changing the magnitude of the slope by adaptive law and varying the intercept by tuning algorithm. Simulations performed using a scaled 3D mathematical model of the crane confirm that the proposed control scheme can keep the horizontal position of the payload invariable and suppress the swing of the payload effectively during the hoisting or lowing process.

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 2016;138(10):101002-101002-6. doi:10.1115/1.4033408.

An adaptive controller based on sliding mode condition is developed with estimated pseudopartial derivative (PPD) of data-driven scheme. The controlled plant is considered as a class of unknown discrete-time systems with only output feedback, which allows the proposed controller to be applicable for practical plants operated by computerization systems. The convergence of estimated PPD is analyzed by Lyapunov direct method under reasonable assumptions. The control law is derived by the estimated PPD and reaching condition of sliding surface as a model-free of controlled plant. The performance of the proposed control scheme is validated by theoretical analysis and experimental system with direct current (DC) motor current control.

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 2016;138(10):101003-101003-8. doi:10.1115/1.4033557.

In this paper, we have addressed a sliding-mode switching control scheme with disturbance observer for a class of single-input single-output (SISO) discrete switched nonlinear systems which suffer from uncertain parameters. To overcome the influences, the external disturbances, and uncertainty, an application of the boiler steam temperature control systems has been modeled as the control plant, and a disturbance compensator observer from the sliding-mode dynamics has been proposed to enhance robustness and decrease the system chattering. With the presented control scheme, using the feedback linearizable method and average dwell time technique, the closed-loop switching system is stable such that the output tracking error converges to a small neighborhood nearby zero and the sliding-mode surface can be well obtained. Experimental results of the superheated steam temperature systems have developed the better performance of the proposed control scheme over traditional sliding control strategy, which have demonstrated good accuracy of tracking error performance.

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 2016;138(10):101004-101004-9. doi:10.1115/1.4033840.

The energy efficiency of the piston pumps is one of the considerable important factors in design and analysis of hydraulic system, especially in the process of real-time tracking of energy dissipation in a variety of loading conditions. The existing methods for obtaining the energy efficiency curve of piston pumps are either time-consuming or inaccurate. In order to quantify the energy efficiency of the piston pumps quickly and accurately, the leakage and friction energy loss caused by the clearances in the sliding pairs are analyzed, and an overall efficiency model was established, which contains two constants to be determined by two test points. The accuracy of the model was verified based on a test rig for a hydraulic pump, and it can be improved by selecting appropriate test points via the method of deviation analysis. The results show that the proposed efficiency models are in good agreement with the experimental results, and the best test points are in the range of 0–25% and 51–75% of the peak pressure of the investigated piston pump.

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 2016;138(10):101005-101005-9. doi:10.1115/1.4033630.

This paper integrates a previously developed iterative learning identification (ILI) (Liu, N., and Alleyne, A. G., 2016, “Iterative Learning Identification for Linear Time-Varying Systems,” IEEE Trans. Control Syst. Technol., 24(1), pp. 310–317) and iterative learning control (ILC) algorithms (Bristow, D. A., Tharayil, M., and Alleyne, A. G., 2006, “A Survey of Iterative Learning Control,” IEEE Control Syst. Mag., 26(3), pp. 96–114), into a single norm-optimal framework. Similar to the classical separation principle in linear systems, this work provides conditions under which the identification and control can be combined and guaranteed to converge. The algorithm is applicable to a class of linear time-varying (LTV) systems with parameters that vary rapidly and analysis provides a sufficient condition for algorithm convergence. The benefit of the integrated ILI/ILC algorithm is a faster tracking error convergence in the iteration domain when compared with an ILC using fixed parameter estimates. A simple example is introduced to illustrate the primary benefits. Simulations and experiments are consistent and demonstrate the convergence speed benefit.

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 2016;138(10):101006-101006-15. doi:10.1115/1.4033708.
OPEN ACCESS

Precise image capture using a mechanical scanning endoscope is framed as a resonant structural-deflection control problem in a novel application. A bipolar piezoelectric self-sensing circuit is introduced to retrofit the piezoelectric tube as a miniature sensor. A data-driven electromechanical modeling approach is presented using system identification and system inversion methods that together represent the first online-adaptive control strategy for the scanning fiber endoscope (SFE). Trajectory tracking experiments show marked improvements in scan accuracy over previous control methods and significantly, the ability of the new method to adapt to changing operating environments.

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 2016;138(10):101007-101007-11. doi:10.1115/1.4033841.

Mobile manipulators have reduced maneuverability and risk rolling over when operated at high speeds. One of the main contributing factors is the higher center of gravity (CG) due to the manipulator arm. This paper proposes a new dynamic weight-shifting method that uses the manipulator arm on the mobile robot to improve maneuverability and reduce rollover risk. A control law is developed such that the manipulator arm keeps a low CG and the contribution of the reaction moments from its inertia is small in comparison to the reaction moments due to gravity. A linear dynamic model is used to analyze the effect of the arm design (link length, mass, etc.) on the roll dynamics. A higher fidelity nonlinear simulation is used to evaluate roll reduction and the impact on handling dynamics. Last, the dynamic weight-shifting method is implemented in hardware. With regard to reducing rollover risk, simulation results from the nonlinear model (NLM) show a 29% reduction in wheel normal load transfer by using the proposed method. In terms of improving maneuverability, experimental results with hardware demonstrate a 13% increase in lateral acceleration when using dynamic weight-shifting. By reducing the vehicle's roll motion, dynamic weight-shifting can increase safe operating speeds and maneuverability.

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 2016;138(10):101008-101008-17. doi:10.1115/1.4033865.

Presented are reduced-order models of one-dimensional transient two-phase gas–liquid flow in pipelines. The proposed model is comprised of a steady-state multiphase flow mechanistic model in series with a transient single-phase flow model in transmission lines. The steady-state model used in our formulation is a multiphase flow mechanistic model. This model captures the steady-state pressure drop and liquid holdup estimation for all pipe inclinations. Our implementation of this model will be validated against the Stanford University multiphase flow database. The transient portion of our model is based on a transmission line modal model. The model parameters are realized by developing equivalent fluid properties that are a function of the steady-state pressure gradient and liquid holdup identified through the mechanistic model. The model ability to reproduce the dynamics of multiphase flow in pipes is evaluated upon comparison to olga, a commercial multiphase flow dynamic code, using different gas volume fractions (GVF). The two models show a good agreement of the steady-state response and the frequency of oscillation indicating a similar estimation of the transmission line natural frequency. However, they present a discrepancy in the overshoot values and the settling time due to a difference in the calculated damping ratio. The utility of the developed low-dimensional model is the reduced computational burden of estimating transient multiphase flow in transmission lines, thereby enabling real-time estimation of pressure and flow rate.

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 2016;138(10):101009-101009-14. doi:10.1115/1.4034019.

Position control and vibration damping of flexible-link mechanisms are still challenging open issues in robotics. Finding solutions for these problems can lead to improvement in the operation and accuracy of the manipulators. In this paper, the synthesis of robust controllers based on $H∞$ loop shaping and $μ$-synthesis for both position control and vibration damping in a spatial flexible L-shape mechanism with gravity is presented. The design of the controllers is based on the evaluation of an uncertainty model which takes into account a $±20%$ uncertainty in the elasticity and mass density of the links. The response of each controller is tested also in the presence of external disturbances with the aid of highly accurate numerical simulations; furthermore, a comparison between the robust performances of synthesized controllers is presented in order to show the effectiveness of synthesized control systems.

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 2016;138(10):101010-101010-12. doi:10.1115/1.4033946.

This paper derives several well-posedness (existence and uniqueness) and stability results for nonlinear stochastic distributed parameter systems (SDPSs) governed by nonlinear partial differential equations (PDEs) subject to both state-dependent and additive stochastic disturbances. These systems do not need to satisfy global Lipschitz and linear growth conditions. First, the nonlinear SDPSs are transformed to stochastic evolution systems (SESs), which are governed by stochastic ordinary differential equations (SODEs) in appropriate Hilbert spaces, using functional analysis. Second, Lyapunov sufficient conditions are derived to ensure well-posedness and almost sure (a.s.) asymptotic and practical stability of strong solutions. Third, the above results are applied to study well-posedness and stability of the solutions of two exemplary SDPSs.

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 2016;138(10):101011-101011-10. doi:10.1115/1.4033907.
OPEN ACCESS

Health monitoring of automated manual transmission (AMT) in modern vehicles can play a critical role to avoid its malfunctions and ensure vehicle functional safety. In order to meet this demand, this paper presents a model-based fault detection and identification (FDI) scheme for AMT. After developing the fault model of AMT, structural analysis (SA)-based fault detectability and isolability is realized with the available set of sensors, prior to design and development of residuals. The residuals are generated by employing the theory of SA, where the concepts of analytical redundant relationship (ARR) are utilized to make residuals stable and robust. Finally, the proposed FDI scheme is successfully evaluated to detect and isolate the sensor faults in EcoCAR2 AMT.

Commentary by Dr. Valentin Fuster

### Technical Brief

J. Dyn. Sys., Meas., Control. 2016;138(10):104501-104501-5. doi:10.1115/1.4033313.

In this paper, a systematic procedure for controller design is proposed for a class of nonlinear underactuated systems (UAS), which are non-feedback linearizable but exhibit a controllable (flat) tangent linearization around an equilibrium point. Linear extended state observer (LESO)-based active disturbance rejection control (ADRC) is shown to allow for trajectory tracking tasks involving significantly far excursions from the equilibrium point. This is due to local approximate estimation and compensation of the nonlinearities neglected by the linearization process. The approach is typically robust with respect to other endogenous and exogenous uncertainties and disturbances. The flatness of the tangent model provides a unique structural property that results in an advantageous low-order cascade decomposition of the LESO design, vastly improving the attenuation of noisy and peaking components found in the traditional full order, high gain, observer design. The popular ball and beam system (BBS) is taken as an application example. Experimental results show the effectiveness of the proposed approach in stabilization, as well as in perturbed trajectory tracking tasks.

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 2016;138(10):104502-104502-6. doi:10.1115/1.4033839.

A wavelet domain forward differential Ricatti formulation is proposed in this paper for control of linear time-varying (LTV) systems. The control feedback gains derived are time-frequency dependent, and they can be appropriately tuned for each wavelet scale or frequency band. The gains in the proposed forward formulation are functions of the present and past states and hence lead to a nonlinear controller. This nonlinear controller does not require information or approximation about future system matrices. The proposed controller is suitable for systems with time-varying (TV) system matrices and also for controlling transient dynamics. The performance of the proposed controller is compared with two other control strategies, namely, a TV linear quadratic regulator (LQR) based on a backward formulation of the differential Ricatti equation (DRE) and a multiscale wavelet-LQR controller based on asymptotic assumptions. Two numerical examples demonstrate promising results on the performance of the controller.

Commentary by Dr. Valentin Fuster