Abstract
State observers are essential components of a modern control system. It is often designed based on a mathematical model of the process, thus requiring detailed process knowledge. However, in the existing state estimation methods, equal delays are commonly assumed for all communication lines, which is unrealistic and poses problems such as instability and a degraded performance of observers when unequal time delays exist. In this paper, a design of observers considering the measurement delays is presented. To deal with this problem, a chain-based observer has been proposed in which each chain deals with one output delay, performs prediction for the unavailable output value, and passes it to the next chain. Convergence of each chain observer as well as overall state estimation were proven. To illustrate the performance of the proposed scheme, simulation studies were performed on a benchmark continuous stirred tank heater (CSTH) process.
Highlights
Model-Based Observer DesignState observers play a key role in process monitoring, control, and automation by providing estimates of internal state variables using hardware output measurements
One of the profound challenges in state estimation is that sensor measurements are often time delayed from the actual process outputs
When designing an observer or controller for a system affected by such delays, it is often expedient to lump the measurement delay together with any system and actuation delay, as they are indistinguishable in terms of the ideal closed-loop dynamics of the system [9]
Summary
State observers play a key role in process monitoring, control, and automation by providing estimates of internal state variables using hardware output measurements. For linear systems, when the system model is available, there exists literature to deal with equal output delays in state estimation [10,11,12]. This paper intends to extend the Luenberger observer design proposed in [16] to account for equal and unequal measurement delays. It was proven that the proposed chain observer had the desired stability properties with delay-free measurements, and the design followed a two-step strategy. It obtained the delayed state trajectories using delayed measurements with the delay-free observer.
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