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A method for complex RF impedance sensing is proposed. The method is based on using a scalar impedance meter and an impedance tuning network for sensing the complex load impedance. The scalar measurements are conducted three times for different settings of the digitally controlled tuning network after which the load impedance is evaluated based on the scalar outputs from the reflectometer. The measurements of the prototype device are demonstrated. The target application for the presented system and method is the antenna-tuning front end of the multiantenna cellular handheld devices. [ABSTRACT FROM AUTHOR]

A systematic data-based design method for tuning proportional–integral–derivative (PID) controllers for disturbance attenuation is proposed. In this method, a set of closed-loop plant data are directly exploited without using a process model. PID controller parameters for a control system that behaves as closely as possible to the reference model for disturbance rejection are derived. Two algorithms are developed to calculate the PID parameters. One algorithm determines the optimal time delay in the reference model by solving an optimization problem, whereas the other algorithm avoids the nonlinear optimization by using a simple approximation for the time delay term, enabling derivation of analytical PID tuning formulas. Because plant data integrals are used in the regression equations for calculating PID parameters, the two proposed algorithms are robust against measurement noises. Moreover, the controller tuning involves an adjustable design parameter that enables the user to achieve a trade-off between performance and robustness. Because of its closed-loop tuning capability, the proposed method can be applied online to improve (retune) existing underperforming controllers for stable, integrating, and unstable plants. Simulation examples covering a wide variety of process dynamics, including two examples related to reactor systems, are presented to demonstrate the effectiveness of the proposed tuning method. [ABSTRACT FROM AUTHOR]

Highlights: [•] Simultaneous tuning of cascade controllers based directly on closed-loop data without resorting to process models. [•] The tuning method can be applied on-line to improve underperforming cascade controllers. [•] The inner loop achieves rapid attenuation of disturbances. [•] The primary controller tuning accurately accounts for inner-loop dynamics. [•] The tuning method can fulfill robustness specifications for inner and outer loops. [ABSTRACT FROM AUTHOR]

This paper presents a novel method for proportional-integral-derivative (PID) controller tuning directly using the step response data of the process without resorting to a process model. The required process data are collected from a one-shot step test that can be conducted under either closed-loop or open-loop conditions. The proposed method derives the PID parameters so that the resulting control system behaves as closely as possible to the prescribed reference model. Two structures of the reference model are considered for general design and improved disturbance rejection, respectively. A simple one-dimensional optimization problem is formulated to determine an appropriate reference model for the controlled process. Moreover, the proposed PID tuning method includes a robustness specification based on the maximum peak of sensitivity function that enables the user to explicitly address the trade-off between performance and robustness. Simulation examples are provided to illustrate the superiority of the proposed method over existing (model-based) tuning methods. [ABSTRACT FROM AUTHOR]