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J. Dyn. Sys., Meas., Control. 2018;141(4):041001-041001-11. doi:10.1115/1.4041757.

Motor speed synchronization is important in gear shifting of emerging clutchless automated manual transmissions (AMT) for electric vehicles and other kinds of parallel shaft-based powertrains for hybrid electric vehicles. This paper proposes a speed synchronization controller design for a kind of system integrating a traction motor and a dual clutch transmission (DCT), using optimal control and disturbances compensation. Based on the relativity between magnitudes of different system parameters, the optimal control law is simplified into the proportional (P) one to ease design and analysis. Relationship between the feedback gain and the duration of speed synchronization process is derived in an explicit way to facilitate model-based determination of controller parameters. To alleviate overshoot while maintaining predesigned performances, the explicit nominal speed trajectory rather than the fixed setpoint speed is chosen as the reference signal. To improve robustness of the controller, a time-domain disturbance observer (DO) is added to cancel effects from parameter drift, unmodeled dynamics, and other exogenous disturbances. As a result, the proposed controller possesses merits of few controller parameters to be determined, good transient response, and robustness. These features make it suitable for practical engineering use. Simulation and experiment results verify its effectiveness in attaining both a fast and small-overshoot speed synchronizing process.

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 2018;141(4):041002-041002-9. doi:10.1115/1.4041664.
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In this paper, we present a method to accurately predict the wheel speed limits at which mobile robots can operate without significant slipping. The method is based on an asymptotic solution of the nonlinear equations of motion. Using this approach, we can predict wheel slipping limits of both the inside and outside wheel when the robot is in a constant circular motion of any radius. The analytical results are supported by experiments, which show that the inside wheel slipping limits for circular motions of various radii occur very close to the predicted values. The method is then applied to predict wheel speed profiles for general motion without slipping and experimentally verified for a sinusoidal path.

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 2018;141(4):041003-041003-11. doi:10.1115/1.4041703.

This paper deals with the problem of rigid formation control using directed graphs in both two-dimensional (2D) and three-dimensional (3D) spaces. Directed graphs reduce the number of communication, sensing, and/or control channels of the multi-agent system. We show that the directed version of the gradient descent control law asymptotically stabilizes the interagent distance error dynamics of minimally persistent formation graphs. The control analysis begins with a (possibly cyclic) primitive formation that is grown consecutively by Henneberg-type insertions, resulting at each step in two interconnected nonlinear systems, which are recursively analyzed using the stability of interconnected systems. Simulation and experimental results are presented for the directed formation controller in comparison to the standard undirected controller.

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 2018;141(4):041004-041004-7. doi:10.1115/1.4041812.

In this paper, a new aging detection method of a supercapacitor is proposed through the study of the charge process. Good indicators to describe this aging are equivalent series resistance (ESR) and capacitance evolution, which are online unmeasurable parameters of the component model. The proposed model belongs to the class of state and parameter affine nonlinear system. A new adaptive nonlinear observer is designed to estimate, under different aging phases, both states and parameters using measurements only available at each sampling instant. This unusual observer contains an adaptive gain, an unknown parameter into the measured output equation, and the control signal into state matrix. This discrete-continuous observer is proved to be globally exponentially convergent under some sufficient conditions. Theoretical results are implemented for two cases of study, the first one through some simulations and the second one applied on real data for different sampling times and different values of observer gain. Results highlight good performances of the observer in online parameter estimation; thus, the component aging is clearly shown.

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 2018;141(4):041005-041005-9. doi:10.1115/1.4041712.

This paper considers the observer design problem for a class of discrete-time system whose nonlinear time-varying terms satisfy incremental quadratic constraints. We first construct a circle criterion based full-order observer by injecting output estimation error into the observer nonlinear terms. We also construct a reduced-order observer to estimate the unmeasured system state. The proposed observers guarantee exponential convergence of the state estimation error to zero. The design of the proposed observers is reduced to solving a set of linear matrix inequalities. It is proved that the conditions under which a full-order observer exists also guarantee the existence of a reduced-order observer. Compared to some previous results in the literature, this work considers a larger class of nonlinearities and unifies some related observer designs for discrete-time nonlinear systems. Finally, a numerical example is included to illustrate the effectiveness of the proposed design.

Commentary by Dr. Valentin Fuster

Technical Brief

J. Dyn. Sys., Meas., Control. 2018;141(4):044501-044501-8. doi:10.1115/1.4041977.

This paper studies the design and implementation of an interactive real-time cloud supervisory control and data acquisition (SCADA) platform. The platform relying on C# and client/server architecture provides full support for data supervision of the cloud control system (CCS). Users are allowed to design supervisory interfaces by dynamically creating and customizing virtual instruments, which are seamlessly integrated into the platform by reconstructing it. Both the scalar and matrix data from different cloud nodes are supported for supervising simultaneously in real-time through receiving data asynchronously. The user can tune the parameters of the CCS online via duplex channels based on the transmission control protocol/internet protocol (IP). To overcome the disturbance of network delays to data display, a stable data and real-time data communication scheme are proposed. All the supervised data can be stored in separate files for further analysis. Finally, the online simulation and experiment are provided to demonstrate the feasibility of the designed SCADA platform.

Commentary by Dr. Valentin Fuster

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