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The automatic recognition of animal sounds is one of the powerful techniques for replacing the traditional ecological survey method that mainly depends on manpower, which is hence both costly and time consuming. This study developed an automatic frog call recognition system based on the combination of a pre-classification method of the syllable lengths and a multi-stage average spectrum (MSAS) method. In this system, the input frog syllables are first classified into one of the four groups determined by the pre-classification method according to syllable length. Then the proposed MSAS method is used to extract the standard feature template to analyze the time-varying features of each frog species and to recognize the input frog syllable by a template matching method. In all, 960 syllables recorded from 18 frog species are included in this study to evaluate the accuracy of the proposed frog call recognition system. The experimental results demonstrate that the proposed one-level (using the MSAS method only) and two-level (combining the syllable length pre-classification and MSAS methods) recognition methods can provide the best recognition accuracies of 91.9% and 94.3%, respectively, compared with other recognition methods based on dynamic time warping (DTW), spectral ensemble average voice prints (SEAV), k-nearest neighbor (kNN) and support vector machines (SVMs).

The development of the control algorithms for under-actuated systems is important. Decoupled sliding mode control has been successfully employed to control under-actuated systems in a decoupling manner with the use of sliding mode control. However, in such a control scheme, the system functions must be known. If there are uncertainties in those functions, the control performance may not be satisfactory.In this paper, the direct adaptive fuzzy sliding mode control is employed to control a class of under-actuated uncertain systems which can be regarded as a combination of several subsystems with one same control input. By using the hierarchical sliding control approach, a sliding control law is derived so as to make every subsystem stabilized at the same time. But, since the system considered is assumed to be uncertain, the sliding control law cannot be readily facilitated. Therefore, in the study, based on Lyapunov stable theory a fuzzy compensator is proposed to approximate the uncertain part of the sliding control law. From those simulations, it can be concluded that the proposed compensator can indeed cope with system uncertainties. Besides, it can be found that the proposed compensator also provide good robustness properties.

Summary This paper considers the design of simultaneous static output feedback controllers for a finite collection of time‐delay linear systems. By solving a minimization problem, we try to find an output feedback low‐gain controller such that all resultant closed‐loop time‐delay systems are internally stable and satisfy a prespecified H∞‐norm requirement. Based on the barrier method, necessary conditions for local optimum of the minimization problem are derived. An example is given for illustration.

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