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In this paper the problem of continuous and discrete state estimation for a class of linear switched systems is studied. The class of systems under study can contain nonminimum phase zeros in some of their “operating modes”. The conditions for exact reconstruction of the discrete state are given using structural properties of the switched system. The state-space is decomposed into the strongly observable part, the nonstrongly observable part and the unobservable part, to analyze the effect of the unknown inputs. A state observer based on high-order sliding-mode and Luenberger-like observers is proposed. For the case when the exact reconstruction of the state cannot be achieved, the ultimate bounds on the estimation errors are provided. The workability of the proposed method is illustrated by simulations. [ABSTRACT FROM PUBLISHER]

The paper discusses the problem of integrating the equations of state observers associated with direct field orientation (DFO) of AC motor drives and shows the results when the quasi-low pass filters used for integration are discretized based on the Zero Order Hold method (ZOH) and the First Order Hold method (FOH). In a typical observer implementation, the equations are discretized using the Euler method - this is a simple, straightforward approach. Integration is accurate only if the sampling time is small. However, in certain cases, it may not be possible to use a small sampling time. At higher sampling time and under special conditions (if the signals to be integrated are of high frequency), the integration process becomes more inaccurate because the Euler approximation starts losing significant area from under the curve. For a given sampling time, the integral output could be improved by using a more accurate integration method, for example, trapezoidal integration - this solution was already studied. The paper presents the results obtained when the observer equations are integrated with filters that are discretized using the ZOH and the FOH methods. The resulting integral outputs are compared with the ones of the Euler and trapezoidal methods. For illustration, a state observer for the permanent magnet synchronous motor is studied. The theoretical developments are supported with simulation results. [ABSTRACT FROM PUBLISHER]

The causes of position estimation delays and their effects on the sensorless control of permanent magnet synchronous motor drives are investigated. The position of a permanent magnet synchronous machine is estimated via the injection of high frequency voltage signals. The delays under investigation are due to the digital implementation of the control algorithm and to the digital filters adopted for decoupling the inspection signals from the fundamental components of the stator current measures. If not correctly modeled and compensated, such delays can reduce the performance of the control scheme. Experimental results are provided, proving the accuracy of the modeling approach and the effectiveness of the related compensation strategy. [ABSTRACT FROM PUBLISHER]