The negative impedance characteristics of a constant power load (CPL) can easily lead to the instability of the DC bus voltage. To improve the stability of the DC bus voltage, an adaptive backstepping sliding mode control strategy for a boost converter with the CPL in DC microgrid is proposed. First, to carry out the backstepping control, the zero dynamic stability of the system under different output functions is studied by using input-output exact feedback linearization theory. The model is transformed into a linear system in Brunovsky canonical form, which solves the nonlinear problem caused by the CPL and the nonminimum phase problem of the boost converter. Then, under the premise of ensuring large signal stability, an adaptive mechanism is introduced into the design of the backstepping sliding mode control. The adaptive backstepping sliding mode controller is designed by adaptively updating the switching gain in real time. Furthermore, the Lyapunov theory is used to prove the global asymptotic stability of the overall closed-loop system. Finally, the numerical simulation and experimental results show that the proposed control strategy has better dynamic regulation performance and stronger robustness compared with the conventional double closed-loop PI control method.INDEX TERMS Constant power load, boost converter, exact feedback linearization, backstepping sliding mode control adaptive.
Self-reconfigurable or metamorphic robots can change their individual and collective shape and size to meet operational demands. Since these robots are constructed from a set of autonomous and connectable modules (or agents), controlling them is a challenging task. The difficulties stem from the facts that all locomotion, perception, and decision making must be distributed among a network of modules, that this network has a dynamic topology, that each individual module has only limited resources, and that the coordination between modules is highly complex and diverse. To meet these challenges, this paper presents a distributed control mechanism inspired by the concept of hormones in biological systems. We view hormones as special messages that can trigger different actions in different modules, and we exploit such properties to coordinate motions and perform reconfiguration in the context of limited communications and dynamic network topologies. The paper develops a primitive theory of bormone-based control, reports the experimental results of applying such a control mechanism to our CONRO metamorphic robots, and discusses the generality of the approach for a larger class of distributed autonomous systems.
This paper considers the analytical free time domain response and energy in an axially translating and laterally vibrating string. The domain of the string is either a constant or variable length, dependent upon the general initial conditions. The translating tensioned strings possess either fixed-fixed or fixed-free boundaries. A reflected wave superposition method is presented as an alternative analytical solution for a finite translating string. Firstly, the cycles of vibration for both constant and variable length strings are provided, which for the latter are dependent upon the variable string length. Each cycle is divided into three time intervals according to the magnitude and the direction of the translating string velocity. Applying d'Alembert's method combined with the reflection properties, expressions for the reflected waves at the two boundaries are obtained. Subsequently, superposition of all of the incident and reflected waves provides results for the free vibration of the string over the three time intervals. The variation in the total mechanical energy of the string system is also shown. The accuracy and efficiency of the proposed method are confirmed numerically by comparison to simulations produced using a Newmark-Beta method solution and an existing state space function representation of the string dynamics.
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