Peter H. Bauer

The mobile patient: wireless distributed sensor networks for patient monitoring and care

The concept of a three layer distributed sensor network for patient monitoring and care is introduced. The envisioned network has a leaf node layer (consisting of patient sensors), an intermediate node layer (consisting of the supervisory processor residing with each patient) and the root node processor (residing at a central monitoring facility). The paradigm has the capability of dealing with the bandwidth bottleneck at the wireless patient-root node link and the processing bottleneck at the central processor or root node of the network.

A necessary and sufficient condition for robust asymptotic stability of time-variant discrete systems

A necessary and sufficient condition for the stability of time-variant interval matrices is presented. This condition allows stability to be tested by checking only products of vertex (extreme) matrices. The implementation of the test in the form of an algorithm and two illustrative examples are provided. >

Conditioning and updating evidence

Abstract A new interpretation of Dempster–Shafer conditional notions based directly upon the mass assignments is provided. The masses of those propositions that may imply the complement of the conditioning proposition are shown to be completely annulled by the conditioning operation; conditioning may then be construed as a re-distribution of the masses of some of these propositions to those that definitely imply the conditioning proposition. A complete characterization of the propositions whose masses are annulled without re-distribution, annulled with re-distribution and enhanced by the re-distribution of masses is provided. A new evidence updating strategy that is composed of a linear combination of the available evidence and the conditional evidence is also proposed. It enables one to account for the ‘integrity’ and ‘inertia’ of the available evidence and its ‘flexibility’ to updating by appropriate selection of the linear combination weights. Several such strategies, including one that has a probabilistic interpretation, are also provided.

A stability analysis of two-dimensional nonlinear digital state-space filters

Two different methods for a stability analysis of 2-D nonlinear discrete state-space systems under zero input conditions are provided. The first method reduces the task of testing a 2-D discrete nonlinear or shift-varying system to a single 2-D linear stability test of a system matrix with nonnegative system matrix entries. The second method is based on a number of norm tests for products of extreme matrices, and can be considered the 2-D counterpart of the method for 1-D systems described by K.T. Erickson and A.N. Michel (1985). Both of the introduced methods are based on the sector description of the nonlinearity and can be used to analyze digital filter stability under finite-word-length effects. >

A computer-aided test for the absence of limit cycles in fixed-point digital filters

The problem of determining the existence of limit cycles in direct form digital filters with quantization nonlinearities is considered. A method based on an exhaustive search is introduced. It is applicable to all direct form digital filters regardless of the type of quantization arithmetic, the number of quantizers, and the order of the filter. The equivalence between the concept of global asymptotic stability and the exclusion of limit cycles is proved for linearly stable finite-wordlength digital filters. The robustness of this test with respect to coefficient perturbation in the digital filter is presented. The computational aspects of the algorithm are also discussed. The algorithm is shown to be capable of always determining the global asymptotic stability of the tested realization. >

Multidimensional control systems: case studies in design and evaluation

Multidimensional control systems have been the subject of much productive research over more than three decades. In contrast to standard control systems, there has been much less reported on applications where the multidimensional setting is the only possible setting for design or produces implementations that perform to at least the same level. This paper addresses the latter area where case studies focusing on control law design and evaluation, including experimental results in one case, are reported. These demonstrate that movement towards the actual deployment of multidimensional control systems is increasing.

Total delay compensation in LAN control systems and implications for scheduling

In the first part of this paper it is shown that long access delays are not necessarily detrimental to the stability of local area network embedded control systems. In the second part we show that (under some mild conditions on the control system) scheduling in the return path is not needed. This is a consequence of the fact that for local area networks the access delays can be exactly determined and completely eliminated from the system representation.

Realization of block floating-point digital filters and application to block implementations

Realization issues of block floating-point (BFP) filters such as complexity, roundoff noise, and absence of limit cycles are analyzed. Several new results are established. Under certain conditions, BFP filters perform better than fixed-point filters at the expense of a slight increase in complexity; convex programming can be used to minimize the roundoff noise; limit cycles will not be present if the underlying fixed-point system is free of quantization limit cycles. It is shown that BFP arithmetic can be efficiently combined with block implementations to further improve the roundoff noise and stability of the implementation and reduce the complexity of processing BFP data.

Robust stability of time-variant interval matrices

The stability of time-variant discrete interval matrices is analyzed, and conditions for asymptotic as well as bounded-input bounded-output stability are derived, making it necessary to test the Schur-stability of one of the 2/sup n*/ corner matrices. For certain classes of interval matrices this condition becomes necessary and sufficient.<<ETX>>

A novel approach to grid sensor networks

A novel approach to information processing in grid sensor networks is presented. Based on the Fornasini-Marchesini (FM) model, this highly scalable method can implement any general linear system in a grid sensor network in a fully distributed manner. It can significantly reduce the communication overhead and enable local actuation in response to local events. Quantization effects on the stability of such distributed filters are briefly discussed with models for quantization nonlinearities. A real world implementation of this distributed processing method on a sensor network is also presented.