In this paper, the problem of state constraints control is investigated for a class of output constrained flexible manipulator system with varying payload. The dynamic behavior of the flexible manipulator is represented by partial differential equations. To prevent states of the flexible manipulator system from violating the constraints, a barrier Lyapunov function which grows to infinity whenever its arguments approach to some limits is employed. Then, based on the barrier Lyapunov function, boundary control laws are given. To solve the problem of varying payload, an adaptive boundary controller is developed. Furthermore, based on the theory of barrier Lyapunov function and the adaptive algorithm, state constraints and output control under vibration condition can be achieved. The stability of the closed-loop system is carried out by the Lyapunov stability theory. Numerical simulations are given to illustrate the performance of the closed-loop system.
The aim of this paper is to isolate pure cultures that are capable of degrading paraquat (PQ) anaerobically with humic substances (humus) as the sole electron acceptor. Three facultative anaerobic bacteria (PQ-1, PQ-2, and PQ-3) were successively isolated from vegetable soil in Sanya city, China, via enrichment procedure with PQ and anthraquinone-2,6-disulphonate (AQDS) under anaerobic conditions. Batch experiments were conducted to investigate isolates PQ anaerobic degradation activity. Results showed that three strains were all capable of degrading PQ directly with AQDS as the sole electron acceptor (18.6% removal within 48h), and the microbial process might be AQDS dependent. The addition of low molecular weight organic substrate, such as sucrose, could enhance the anaerobic degradation of PQ from 18.6% to 34.2%, and the degradation rate reached 100% after 5-day incubation. This study was the first paper reporting that pure cultures have the ability to anaerobically degrade PQ with AQDS as the sole electron acceptor.
This paper deals with trajectory tracking problem of a spherical mobile robot, BHQ-1. First, a desired velocity is obtained by proposing a PD controller based on the kinematics. Then a PD controller with an RBF (Radial Basis Function) neural network is proposed based on the desired velocity and the inexact dynamics. The weights of the RBF network are designed with an adaptive rule based on the tracking error, and hence the network can compensate the uncertainties of the dynamics more effectively. Stability is presented via Lyapunov Theory and simulation results are provided to illustrate the tracking performance.
A LiFePO4/porous carbon nanocomposite was synthesized by using spontaneous precipitation combined with solid-state reaction. The microstructure, morphology and electrochemical properties of as-prepared samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), differential thermal analysis (TGA) and charge-discharge cycling tests. The results reveal that LiFePO4 particles are well-dispersed into porous carbon framework. The initial discharge of nanocomposite is 143 mAh g-1 at 0.1 C and 114 mAh g-1 at 1 C with satisfactory capacity retention. The superior electrochemical performance of the composites can be attributed to the nano-confined effect of conducting porous carbon and the nano-size of LiFePO4 particles in LiFePO4/porous carbon nanocomposite.
In this paper, the dynamic model is established for the two-link rigid-flexible manipulator, which is represented by nonlinear ordinary differential equations–partial differential equations (ODEs–PDEs). Based on the nonlinear ODE–PDE model, the boundary control strategy is designed to drive the manipulator to follow a given trajectory and eliminate the vibration simultaneously. Considering actuators saturation, smooth hyperbolic tangent function is introduced for dealing with control input constraints problem. It has been rigorously proved that the nonlinear closed-loop system is asymptotically stable by using LaSalle's invariance principle. Simulation results show that the proposed controller is effective.
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