Reset Control Research Articles

Dynamic modeling, adaptive control and energy performance simulation of a hybrid hydronic space heating system

A dynamic model of a hybrid hydronic heating system has been developed. The overall model consists of a boiler, a heat exchanger, a ground loop heat pump, a ground loop heat exchanger, baseboard heaters (convector–radiators), and radiant floor hydraulic piping system. Two control strategies for improving the overall system performance were explored: (1) a conventional proportional-integral (PI) control and (2) an adaptive gain control. The simulation results showed that the performance of the adaptive controller is better than the fixed gain PI controller in disturbance rejection and stability. Energy simulations under three different operating strategies were conducted: (1) a fixed set-point PI control, (2) an outdoor air temperature reset control, and (3) an optimal set-point adaptive PI control. It was shown that the outdoor temperature reset strategy can save 4.5 and 19.9% energy under cold day and mild day conditions compared to the fixed set-point PI control strategy. The optimal adaptive PI control strategy resulted in higher energy savings of 6.6 and 22% as compared to the PI control under cold and mild day conditions, respectively. Practical application: Energy efficiency and sustainability are a major issue of importance in the design and operation of space heating systems. The proposed hybrid system combines a ground-source heat pump and a hot water boiler for space heating of both residential and commercial building applications. The heating system consists of radiant floor piping for the residential zones and hot water baseboard heaters (convector–radiators) for the commercial zones. An energy optimal adaptive control strategy is designed to improve energy efficiency and temperature control performance of the hybrid system. The control strategy is simple and can be implemented on the existing building control systems.

室内気流連成型動的空調システムシミュレーションに関する研究 : 第3報-非定常温度環境下での温冷感を利用した空調の冷房運転における送風温度リセット制御とデマンド抑制制御が与える影響

室内気流連成型動的空調システムシミュレーションに関する研究 : 第3報-非定常温度環境下での温冷感を利用した空調の冷房運転における送風温度リセット制御とデマンド抑制制御が与える影響

Optimal adaptive reset control with guaranteed transient and steady state tracking error bounds

In this paper, a solution for improvement of transient performance in adaptive control of nonlinear systems is proposed. An optimal adaptive controller based on a reset mechanism and a prescribed performance bound is devised. The suggested controller has the structure of adaptive backstepping controller in which the estimated parameters are reset to an optimal value. The designed controller ensures both the transient bound and the asymptotical convergence of the states. It is shown that the tracking error satisfies the prescribed performance bound all the time, besides the speed of the convergence rate is increased by resetting the estimated parameters. The results have been proved through both the analytical and simulation studies. The proposed method is applied to an Augmented Quarter Car Model as a case study. Simulation results verify the established theoretical consequences that the prescribed performance bound based optimal adaptive reset controller can enhance the transient performance of the adaptive controller.

A transient model for the thermal inertia of chilled-water systems during demand response

Demand response (DR) of air-conditioning systems is important to shift or reduce the peak electricity demand of commercial buildings by shift or reduce the cooling load. Popular DR strategies of air-conditioning systems include zonal temperature reset and direct control of the main equipment. Many DR studies have been conducted on the thermal inertia of buildings for temperature resetting, but there are few studies on the thermal inertia of air-conditioning systems, which is relatively small but not negligible. In this paper, the thermal inertia of air-conditioning systems is defined as the character that causes the variation of the supply cooling capacity to zones lagging behind the variation of the cooling capacity from plants after DR strategies are implemented. This paper develops an inertia model of chilled-water systems with three sub-models, including chiller model, chilled-water pipe model and cooling coil model. The model describes the dynamic process from the cooling plant to terminal units when DR strategies on chillers are implemented. A new parameter Q(t) named the “refrigerant cooling capacity” is introduced in this study to simplify the thermal inertia model. The Q(t) patterns during the dynamic processes of two series of common chiller-side control strategies (On/Off control and resetting the chilled-water temperature) are obtained and validated using experiments and field tests. In the end, the entire transient model of air-conditioning systems is validated using experiments.

Controller Reset Strategy for Anti‐Windup Based on Switching Gain Analysis

AbstractWhen the calculated value of a control input approaches its limitations, resets of controllers are often used to prevent windup. However, an automatic reset should only be performed after confirmation that it will not adversely affect the transient performance and lead to another windup. In this study, we apply a switching gain analysis to a more appropriate evaluation of transient responses after a reset in order to propose an improved strategy for the automatic resets of controllers, such that windup does not accompany resets.

Wind Turbine Synchronous Reset Pitch Control

Reset controllers are commonly used to smooth the transient response of systems. We use this technique to improve a standard baseline pitch controller for offshore wind turbines (WTs). The introduction of this strategy enhances the overall performance of the WT. In particular, the fore-aft and side-to-side accelerations of the WT tower are significantly reduced, whilst a steadier power output is obtained, in comparison to the standard baseline pitch controller. Furthermore, our designed pitch control’s main advantage, with respect to the baseline, is its ease of implementation and reduced complexity as it does not require a gain-scheduling technique, nor pitch position measurement (thus, it is insensitive to pitch sensor faults). The proposed approach has been simulated on the NREL 5-MW prototype offshore turbine model, mounted on a jacket support. The simulations are carried out using the aero-hydro-servo-elastic simulator FAST, and key observations are thoroughly discussed.

Frequency-domain tools for stability analysis of reset control systems

The potential of reset controllers to improve the transient performance of linear (motion) systems has been extensively demonstrated in the literature. The design and stability analysis of these reset controllers generally rely on the availability of parametric models and on the numerical solution of linear matrix inequalities. Both these aspects may hamper the application of reset control in industrial settings. To remove these hurdles and stimulate broader application of reset control techniques in practice, we present new sufficient conditions, based on measured frequency response data of the system to be controlled, to guarantee the stability of closed-loop reset control systems. The effectiveness of these conditions is demonstrated through experiments on an industrial piezo-actuated motion system.

Investigation of the Demand Response Potentials of Residential Air Conditioners Using Grey-box Room Thermal Model

Abstract This paper investigates demand response (DR) potentials of residential air conditioners (AC) under different control strategies using a grey-box room thermal model. The proposed resistance-capacitance (RC) thermal model combines the essential prior knowledge of room thermal characteristics with data-driven techniques. With the aim of saving the optimization time and improving the reasonableness of the search results, undetermined parameters were physically estimated prior to the identification with nonlinear optimization method. A typical residential bedroom in Hong Kong was chosen to test the room thermal model. The root mean square errors (RMSE) between the sampled and predicted data sets for training and validation sessions were 0.25 °C and 0.28 °C respectively. After coupling the room RC thermal model and an empirical AC energy consumption model, we can get AC power reductions under different control strategies during the DR period. The simulation results show that the temperature set-point reset control strategies enable the power consumption to decrease during the DR event, and the peak reduction increases when the set-point is set higher. Besides, the precooling control strategy can help to further reduce the electric power.

Improved High-Order-Reset-Element Model Based on Circuit Analysis

In this brief, a generalized first-order reset element (GFORE) is first introduced, and its reset model is established based on circuit analysis. Then, a new class of models for the high-order reset element (HORE) is established by connecting several GFOREs and, defining a proper flow set and jump sets, the proposed model is more appropriate for describing the behavior of HORE than existing ones. Moreover, stability analysis results are presented for reset control systems containing high-order reset controllers. Finally, examples are given to show the superior performance of the proposed reset model and indicate the application prospect in networked control systems.

Experimental study of the pressure reset control strategy for energy-efficient fan operation: Part 1: Variable air volume ventilation system with dampers

This paper is the first part of a two-part series which investigate the energy saving potentials in a novel mechanical ventilation system by replacing terminal dampers with decentralized fans. In Part 1, a conventional variable air volume (VAV) ventilation system with dampers is studied as a reference for comparison with the novel ventilation system in Part 2. The present study (Part 1) proposes a new method to implement the pressure reset strategy in practice. A common strategy to control the supply fan speed in a VAV system is to install a pressure sensor in the supply duct system. Then the fan speed is controlled such that a constant static pressure is maintained at the sensor location. Further energy saving can be obtained by resetting the pressure setpoint to a lower value at partial load conditions. This strategy is known as pressure reset control or critical zone reset strategy in the literature. The proposed method has been evaluated through an experimental mock-up in a laboratory environment. Experimental results show a minimum reduction of about 20% in fan power demand with applying the reset strategy compared to a constant static pressure setpoint.

Impact of the duct static pressure reset control strategy on the energy consumption by the HVAC system

This article addresses different duct static pressure control strategies which could be implemented in variable air volume air-conditioning systems (VAV). Two pressure reset control strategies are compared to the commonly used control solution based on the “Constant static pressure” method. First pressure reset control strategy, known as PID Control, uses signals from VAV boxes controllers to reset duct static pressure in a way that one of the VAV dampers is maintained almost entirely open. Second strategy decreases static pressure setpoint until an adjustable number of pressure requests occur. As a response to the certain amount of requests, static pressure setpoint is increased. This strategy is called Trim & Respond. Both static pressure reset control strategies described in this paper are considered to have more significant potential for energy savings than the “Constant static pressure” method. In order to validate this potential, several simulations for different control strategies were carried out and the obtained results are compared and analysed. The theoretical limit of the energy savings - set of the optimal control actions, was estimated with Nelder-Mead algorithm and also presented in this article. General description of the static pressure control strategies Constant static pressure, PID Control and Trim & Respond is given.

Reset control to suppress the instability of cardiac-locomotor synchronization at running

Reset control to suppress the instability of cardiac-locomotor synchronization at running

외기온도 예측 및 보상제어가 난방시스템의 에너지 소비량에 미치는 영향

In this study, the effects of prediction and reset control of outdoor air temperature on energy consumption for central heating system are researched by using TRNSYS program package, and the control performances with the suggested methods of prediction and reset control of outdoor air temperature are compared with the existing ones. As a result, the value of coefficient of determination <TEX>$R^2$</TEX> for the predicted outdoor temperatures is improved and the suggested control method shows maximum 21.8% energy saving in comparison with existing control ones.

&lt;inline-formula&gt; &lt;tex-math notation="LaTeX"&gt;$\mathcal{L}_{2}$&lt;/tex-math&gt; &lt;/inline-formula&gt;-Gain Analysis for a Class of Hybrid Systems With Applications to Reset and Event-Triggered Control: A Lifting Approach

In this paper we study the stability and L 2 -gain properties of a class of hybrid systems that exhibit linear flow dynamics, periodic time-triggered jumps and arbitrary nonlinear jump maps. This class of hybrid systems is relevant for a broad range of applications including periodic event-triggered control, sampled-data reset control, sampled-data saturated control, and certain networked control systems with scheduling protocols. For this class of continuous-time hybrid systems we provide new stability and L 2 -gain analysis methods. Inspired by ideas from lifting we show that the stability and the contractivity in L 2 -sense (meaning that the L 2 -gain is smaller than 1) of the continuous-time hybrid system is equivalent to the stability and the contractivity in L 2 -sense (meaning that the l 2 -gain is smaller than 1) of an appropriate discrete-time nonlinear system. These new characterizations generalize earlier (more conservative) conditions provided in the literature. We show via a reset control example and an event-triggered control application, for which stability and contractivity in L 2 -sense is the same as stability and contractivity in l 2 -sense of a discrete-time piecewise linear system, that the new conditions are significantly less conservative than the existing ones in the literature. Moreover, we show that the existing conditions can be reinterpreted as a conservative l 2 -gain analysis of a discretetime piecewise linear system based on common quadratic storage/Lyapunov functions. These new insights are obtained by the adopted lifting-based perspective on this problem, which leads to computable L 2 -gain (and thus L 2 -gain) conditions, despite the fact that the linearity assumption, which is usually needed in the lifting literature, is not satisfied.

Applications of Control Algorithms for Dimming Operations of Electric Lighting Fixtures in a Small Office

This study examines the influence of system components of photoelectric dimming control systems on dimming control performance. Field measurements were performed and a series of computation were conducted. Continuous and integral reset control algorithms were used in connection with two photosensor shielding conditions. Results indicate that the change patterns of daylight illuminance of unshielded photosensor were similar to those of desktop illuminance. When continuous dimming control algorithm was used, unshielded photosensor conditions failed to meet a target illuminance. For the partially-shielded photosensor conditions, lighting fixtures overshot the desktop and less energy savings was achieved compared to the condition of unshielded photosensor. When the integral reset dimming control was used, the system failed to keep enough task illuminance. The desktop illuminance by electric light showed sudden peak values with no dimmed light for a particular time period. Partial shielding conditions were successful under overcast sky conditions, but no lighting energy savings was achieved. Desktop illuminance and light output correlated strongly. The ANOVA test results for the correlation were effective under a significance level of 0.01.

Observer-based reset law design for uncertain systems by using model predictive strategy

In reset control systems, the reset law determines reset values at reset times. This paper considers the observer-based reset law design for uncertain systems with both nonlinear uncertainties and time-varying parameter uncertainties. A model predictive strategy is proposed to design the reset law by minimizing a quadratic performance index. The optimization problem is transformed into a linear matrix inequalities (LMIs) formulation, and the reset law is solved by using an LMI technique. The proposed approach is applied to a typical continuous stirred-tank reactor system to show the effectiveness of the obtained results.

The Neural-Fuzzy Control of a Transformer Cooling System

In transformer cooling systems, oil temperature is controlled through the use of a blower and oil pump. For this paper, set-point algorithms, a reset algorithm and control algorithms of the cooling system were developed by neural networks and fuzzy logics. The oil inlet temperature was set by a <TEX>$2{\times}2{\times}1$</TEX> neural network, and the oil temperature difference was set by a <TEX>$2{\times}3{\times}1$</TEX> neural network. Inputs used for these neural networks were the transformer operating ratio and the air inlet temperature. The inlet set temperature was reset by a fuzzy logic based on the transformer operating ratio and the oil outlet temperature. A blower was used to control the inlet oil temperature while the oil pump was used to control the oil temperature difference by fuzzy logics. In order to analysis the performance of these algorithms, the initial start-up test and the step change test were performed by using the dynamic model of a transformer cooling system. Test results showed that algorithms developed for this study were effective in controlling the oil temperature of a transformer cooling system.

An impulsive dynamical systems framework for reset control systems

ABSTRACTImpulsive dynamical systems is a well-established area of dynamical systems theory, and it is used in this work to analyse several basic properties of reset control systems: existence and uniqueness of solutions, and continuous dependence on the initial condition (well-posedness). The work scope is about reset control systems with a linear and time-invariant base system, and a zero-crossing resetting law. A necessary and sufficient condition for existence and uniqueness of solutions, based on the well-posedness of reset instants, is developed. As a result, it is shown that reset control systems (with strictly proper plants) do not have Zeno solutions. It is also shown that full reset and partial reset (with a special structure) always produce well-posed reset instants. Moreover, a definition of continuous dependence on the initial condition is developed, and also a sufficient condition for reset control systems to satisfy that property. Finally, this property is used to analyse sensitivity of reset control systems to sensor noise. This work also includes a number of illustrative examples motivating the key concepts and main results.

On [formula omitted] gain performance improvement of linear systems with Lyapunov-based reset control

This paper considers reset rules design for linear systems for the purpose of improving L2 gain performance. Novel Lyapunov-based reset rules are proposed such that the L2 gain performance of reset control systems can be improved compared with the stable base systems, and the proposed method is then extended to observer-based design. Moreover, reset rules design for stabilizing unstable base systems are proposed such that prespecified L2 gain performance can be achieved. Illustrative examples are given to support our results.

Reset Control System - View of Internal Concept

Reset Control System - View of Internal Concept