Reset Compensator Research Articles

WITHDRAWN: A 32-channels analog multiplexer with crosstalk compensation technique in 45nm CMOS

This paper presents a multiplexer that is capable of modulating 32-channels analog signal, which is a promising approach to simplify transmission system. An 8-channels prototype multiplexer with integral functionality and non-ideal factors is fabricated in 45 nm CMOS with area of 0.59 mm2, and verified in a QAM-256 system with 1.2V supply. The proposed multiplexer employs a semi-tree structure to achieve compromise between scale and speed. To relieve adverse effect caused by crosstalk between channels, the auxiliary reset compensation circuit combined with a dedicated timing sequence is utilized. Additionally, the proposed high-speed gate voltage bootstrap switch and high-bandwidth input buffer ensure that the signal remains linear during transmission. In the experimental result, the multiplexer can achieve a pulse width of at least 77ps in 8Gbps code rate, and the root mean square error due to nonlinearity between differential input and output is 1.869 %. The error vector magnitude (EVM) obtained by analyzing output versus input of multiplexer is less than 1.413 %.

Active Disturbance Rejection Control for Uncertain Nonlinear Systems With Sporadic Measurements

This paper deals with the problem of active disturbance rejection control (ADRC) design for a class of uncertain nonlinear systems with sporadic measurements. A novel extended state observer (ESO) is designed in a cascade form consisting of a continuous time estimator, a continuous observation error predictor, and a reset compensator. The proposed ESO estimates not only the system state but also the total uncertainty, which may include the effects of the external perturbation, the parametric uncertainty, and the unknown nonlinear dynamics. Such a reset compensator, whose state is reset to zero whenever a new measurement arrives, is used to calibrate the predictor. Due to the cascade structure, the resulting error dynamics system is presented in a non-hybrid form, and accordingly, analyzed in a general sampled-data system framework. Based on the output of the ESO, a continuous ADRC law is then developed. The convergence of the resulting closed-loop system is proved under given conditions. Two numerical simulations demonstrate the effectiveness of the proposed control method.

Reset control of integrating plus dead time processes

This work develops a tuning method for a reset compensator and an integrating plus dead time system. The reset compensator consists of a proportional integral compensator plus a Clegg integrator (PI+CI), and is equipped with a variable band resetting law, which allows to reduce the harmful effect of time-delay, and a switching reset ratio that obtains a superior performance in comparison with a well-tuned PI compensator. This work exposes a simple tuning rule for setting all the parameters of the PI+CI compensator with the aim of improving both setpoint tracking and load disturbance rejection. A case study is analyzed by simulation, discussing both performance and robustness of several PI+CI and PI compensators. Finally, an experiment of liquid level control shows the advantages of the proposed reset compensator.

Network-Based Reset Control Systems With Time-Varying Delays

Reset compensators have shown to have advantages over linear and time-invariant compensators, especially when used in control loops with time delays. In this work, the potentials of reset control in networked control systems are investigated. Specifically, stability conditions are developed for the case in which network-induced delays are time-varying. To this end, it is shown how a network-based reset control system may be represented as a discrete-time reset control system. In addition, both state-dependent and time-dependent discrete-time reset compensators are analyzed. Finally, a case study is developed and simulation results are discussed, showing the superior performance of reset compensation.

Reset Control of an Industrial In-Line pH Process

This work presents a reset/hybrid control application of an in-line pH process. The nonlinear process dynamic is linearized around different operating points, and as a result a second-order plus dead time plant with uncertain gain and delay is obtained for control purposes. A standard PI compensator and reset compensator are designed and tuned. The main aim of this work was to compare the performance of both compensators by practical experimentation. The results show the reset compensator is able to overcome fundamental limitations of linear and time invariant control with a faster tracking response and overall improvement in disturbance rejection.

Design of Reset Control Systems: The PI + CI Compensator

Reset compensation has been used to overcome limitations of linear and time invariant (LTI) compensation. In this work, a new reset compensator, referred to as proportional and integral (PI) + CI (Clegg integrator), is introduced. It basically consists of adding a Clegg integrator to a PI compensator, with the goal of improving the closed loop response by using the nonlinear characteristic of this element. It turns out that by resetting a percentage of the integral term in a PI compensator, a significant improvement can be obtained over a well-tuned PI compensator in some relevant practical cases, such as systems with dominant lag and integrating systems. The work is devoted to the development of PI + CI tuning rules for basic dynamic systems in a wide range of applications, including first and higher order plus dead time systems.

Tuning rules for a reset PI compensator with variable reset

The PI+CI compensator is a simple reset compensator, its base system is a PI, which has been shown to be effective in a number of practical applications. One fundamental parameter to be tuned is the reset ratio; for lag dominant systems or systems with integrators it is known to give good results overcoming PI compensation. In this work, a systematic method for the tuning of a variable reset ratio (variable at the reset instants) is developed for first and second order plants.

Limit cycles analysis of reset control systems with reset band

The reset band is a simple idea, and a must in practice, to improve reset compensation by adding extra phase lead in a feedback loop. However, a formal treatment of how the reset band can affect stability and performance of a reset control system is still an open issue. This work approaches the problem of the existence and stability of limit cycles of reset control systems with reset band. A frequency domain approach is given by using standard methods based on the describing function. In addition, closed-form expressions have been obtained for the describing function of arbitrary order full reset compensators with and without reset band.

Reset compensation for temperature control: Experimental application on heat exchangers

This work aims at improving the control of an industrial heat exchanger by using reset compensation. The goal is investigating the potentials of a hybrid compensator previously developed by the authors, the PI+CI reset compensator, in the robust control when significant uncertainty is present. To this end, a PI+CI compensator has been designed by using a two step method: firstly, a robust base PI compensator is tuned by using the Quantitative Feedback Theory to satisfy (robust) relative stability and tracking specifications; and secondly, a partial reset action is added to the base lineal PI compensator to improve transitory response. In addition, a PI compensator is tuned by using the Internal Model Control for comparison purposes. Finally, the reset conditions are simply modified in the PI+CI compensator to overcome the effect of the dominant time delay over the reset action, through the introduction of a reset band which can have fixed or variable values along the time.

A passivity-based approach to reset control systems stability

The stability of reset control systems has been mainly studied for the feedback interconnection of reset compensators with linear time-invariant systems. This work gives a stability analysis of reset compensators in feedback interconnection with passive nonlinear systems. The results are based on the passivity approach to L 2 -stability for feedback systems with exogenous inputs, and the fact that a reset compensator will be passive if its base compensator is passive. Several examples of full and partial reset compensations are analyzed, and a detailed case study of an in-line pH control system is given.

Delay-Independent Stability of Reset Systems

Reset control systems have potential advantages to overcome fundamental limitations of LTI compensation. However, since a reset compensator may destabilize a stable base LTI system, stability needs to be guaranteed in advance for a proper practical application of reset control. This works extends previous stability results of reset control systems to consider the case of LTI plants with time-delays. Stability independent of the delay criteria are developed both by means of LMIs and in the frequency domain by using the KYP Lemma.

Stability Analysis of reset control systems with reset band

Abstract Reset band is a simple idea, and a must in practice, to improve reset compensation by adding extra phase lead in a feedback loop. However, a formal treatment of how the reset band can affect stability and performance of a reset control system is still an open issue. This work approaches the problem of existence and stability of limit cycles of reset control systems with reset band. A frequency domain approach is given by using standard methods based on the describing function. In addition, closed-form expressions have been obtained for the describing funtion of arbitrary order full reset compensators with and without reset band.