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A model predictive control (MPC) strategy based on optimal switching sequence concepts is presented for direct power control of grid-connected three-level neutral-point clamped converters. The proposed control strategy explicitly considers the modulator in its formulation along with the model of the system. Through two well-formulated optimal control problems, the proposed strategy is shown to optimally achieve control of the average trajectory of the active and reactive powers as well as the dc-link capacitor voltages without using weighting factors to tradeoff both control targets. Experimental results demonstrate this strategy produces improved steady-state performance with a well-defined output voltage spectrum and fixed-switching frequency while maintaining the inherent fast dynamic responses of MPC strategies. [ABSTRACT FROM AUTHOR]

This article proposes a computational trajectory optimization framework for solving the problem of multiobjective automatic parking motion planning. Constrained automatic parking maneuver problem is usually difficult to solve because of some practical limitations and requirements. This problem becomes more challenging when multiple objectives are required to be optimized simultaneously. The designed approach employs a swarm intelligent algorithm to produce the tradeoff front along the objective space. In order to enhance the local search ability of the algorithm, a gradient operation is utilized to update the solution. In addition, since the evolutionary process tends to be sensitive with respect to the flight control parameters, a novel adaptive parameter controller is designed and incorporated in the algorithm framework such that the proposed method can dynamically balance the exploitation and exploration. The performance of using the designed multiobjective strategy is validated and analyzed by performing a number of simulation and experimental studies. The results indicate that the present approach can provide reliable solutions and it can outperform other existing approaches investigated in this article. [ABSTRACT FROM AUTHOR]

We propose an efficient time-optimal trajectory planning algorithm for an environment with multiple static circular obstacles, which is based on dynamics for differential-wheeled mobile robots (DWMRs) including actuators. This problem is known to be complex particularly if obstacles are present and if full dynamics including actuators is considered. Given a geometric corridor, the proposed technique defines a portion of trajectory between obstacles as a section which is constituted of an arc, out-curve, and in-curve, each with constant control input satisfying bang–bang principle for time-optimization. Then, it designs time-optimal trajectory composed of multiple sections using common tangent between two tangent circles, in which it handles multiple consecutive obstacles without arcs. This method helps to treat complex environment considering dynamics with DWMR's actuators. Simulation results are shown to validate the efficiency of the proposed algorithm. [ABSTRACT FROM PUBLISHER]

In this paper, a novel reaching law for discrete-time sliding-mode control is proposed. The reaching law is established based on an exponential term that dynamically adapts to the variation of the switching function. The difference function is also employed to redefine the change rate as the second-order difference of the disturbance. Unlike existing works, the proposed reaching law is able to guarantee smaller width of the quasi-sliding-mode domain (QSMD) while decreasing the reaching time in the same time. The ultimate magnitude of the QSMD in proposed method is of the order O(T3). Moreover, the reaching steps for the system to converge to the sliding surface are obtained and the system dynamics in and out the QSMD are theoretically analyzed. Both numerical simulations and experimental investigations on a piezoelectric actuator are employed to validate the effectiveness of the proposed method. [ABSTRACT FROM PUBLISHER]

In this paper, we propose a novel offline minimum-time trajectory planning (MTTP) approach for underactuated overhead cranes. To the best of our knowledge, it is the first optimal solution to the MTTP problem for overhead crane systems, which simultaneously takes into account various constraints, including the bounded swing angle for the payload, bounded velocity, acceleration, and even jerk for the trolley. Different from existing approaches, by means of system discretization and augmentation, the quasi-convex optimization technique is successfully adopted to find the minimum-time solution while satisfying all the aforementioned constraints. Extensive simulation and experiments with comparisons to previously published methods are conducted to show the superior performance of the proposed method. Note that the results derived in this paper also serve as promising guidance in engineering applications, since it provides a performance limit, namely, the possible highest efficiency for automatic or manual operation of overhead cranes. [ABSTRACT FROM PUBLISHER]

There is a clear trend to increase the use of electrical systems in aircrafts, leading to a growing demand for electrical power in the aircraft. This increasing power consumption has resulted in increasing dc voltage levels, to reduce energy losses and the size of wiring, as a result of the reduced current levels. However, traditional protections such as circuit breakers are not adequate for the protection of the new systems in high dc voltage, and consequently, it is necessary to introduce new technologies in the field of protection devices. One of these is the solid-state power controller (SSPC), which combines the functions of connecting loads to the bus bars and protecting electrical installations against overload and short circuits. On the other hand, within these electrical systems, the connection of certain loads, such as highly capacitive ones (dc–dc, inverters, etc.), implies the need to develop new control strategies to improve the connection process by SSPCs. This paper presents and analyzes a new advanced control strategy that optimizes the performance during the connection of highly capacitive loads using SSPCs. [ABSTRACT FROM PUBLISHER]

This paper presents an accelerometer-based digital pen for handwritten digit and gesture trajectory recognition applications. The digital pen consists of a triaxial accelerometer, a microcontroller, and an RF wireless transmission module for sensing and collecting accelerations of handwriting and gesture trajectories. The proposed trajectory recognition algorithm composes of the procedures of acceleration acquisition, signal preprocessing, feature generation, feature selection, and feature extraction. The algorithm is capable of translating time-series acceleration signals into important feature vectors. Users can use the pen to write digits or make hand gestures, and the accelerations of hand motions measured by the accelerometer are wirelessly transmitted to a computer for online trajectory recognition. The algorithm first extracts the time- and frequency-domain features from the acceleration signals and, then, further identifies the most important features by a hybrid method: kernel-based class separability for selecting significant features and linear discriminant analysis for reducing the dimension of features. The reduced features are sent to a trained probabilistic neural network for recognition. Our experimental results have successfully validated the effectiveness of the trajectory recognition algorithm for handwritten digit and gesture recognition using the proposed digital pen. [ABSTRACT FROM PUBLISHER]

The following two types of resonant controllers are mainly employed to obtain high performance in voltage-source converters: 1) proportional + resonant (PR) and 2) vector proportional + integral (VPI). The analysis and design of PR controllers is usually performed by Bode diagrams and phase-margin criterion. However, this approach presents some limitations when resonant frequencies are higher than the crossover frequency defined by the proportional gain. This condition occurs in selective harmonic control and applications with high reference frequency with respect to the switching frequency, e.g., high-power converters with a low switching frequency. In such cases, additional 0-dB crossings (phase margins) appear; therefore, the usual methods for simple systems are no longer valid. In addition, VPI controllers always present multiple 0-dB crossings in their frequency response. In this paper, the proximity to the instability of PR and VPI controllers is evaluated and optimized through Nyquist diagrams. A systematic method is proposed to obtain the highest stability and avoidance of closed-loop anomalous peaks: it is achieved by the minimization of the inverse of the Nyquist trajectory distance to the critical point, i.e., the sensitivity function. Finally, several experimental tests, including an active power filter that operates at a low switching frequency and compensates harmonics up to the Nyquist frequency, validate the theoretical approach. [ABSTRACT FROM PUBLISHER]

In this paper, a real-time walking trajectory generation method with three-mass models at constant body height for 3-D biped robots is extended for a diagonal walking. By realization of the diagonal walking, the availability is improved. The modeling of this method is more precise than that of conventional real-time walking trajectory generation methods. In this method, the zero-moment point equation of a body is derived, and an analytic solution of a body trajectory at a constant body height in a single support phase is obtained. Because the analytic solution is used, real-time trajectory generation can be realized. In addition, this method has advantages of the body trajectory at the constant body height. The validities are confirmed from simulations of the 2-D walking and an experiment of the 3-D diagonal walking. [ABSTRACT FROM AUTHOR]