Time-Delayed Control of SISO Systems for Improved Stability Margins

Abstract

While time delays typically lead to poor control performance, and even instability, previ-ous research shows that time delays can, in some cases, be beneficial. This paper presents a new benefit of time-delayed control (TDC) for single-input single-output (SISO) linear time invariant (LTI) systems: it can be used to improve robustness. Time delays can be used to approximate state derivative feedback (SSD), which together with state feedback (SF) can reduce sensitivity and improve stability margins. Additional sensors are not required since the state derivatives are approximated using available measurements and time delays. A systematic design approach, based on solution of delay differential equa-tions (DDEs) using the Lambert W method, is presented using a scalar example. The method is then applied to both single- and two-degree of freedom (DOF) mechanical sys-tems. The simulation results demonstrate excellent performance with improved stability margins. [DOI: 10.1115/1.4028528]

Fully Time-Based PID Controller for a High Frequency Buck Converter

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“…A number of studies address the utilization of time delays in state feedback control scheme to approximate integral and derivative terms [29,30,62]. In a recent research, Ulsoy [62] proved the positive effect of time delayed control on the disturbance rejection capability and tracking ability of a single input single output (SISO) system. Delay differential equation (DDE) was solved using the Lambert-W functions.…”

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