Bumpless Transfer Problem Research Articles

Output Regulation Bumpless Transfer Control for Discrete-Time Switched Linear Systems

This paper mainly focuses on the output regulation (OR) bumpless transfer (BT) control problem for discrete-time switched linear systems (DSLSs). A procedure for solving the OR BT control problem is given by means of the multiple Lyapunov functions technique. Firstly, the definition of the performance of BT for DSLS is introduced. Next, the state-dependent switching law and a group of BT feedback controllers for solving the OR BT problem are designed. Then, a sufficient condition and its deformation form are obtained without the solvability requirement of OR BT control problem for every subsystem. Finally, the Chua’s circuit example is presented and the results of the simulation verify the effectiveness of the proposed control scheme.

H∞ bumpless transfer for switched LPV systems and its application

ABSTRACTIn this paper, the approach of the control bumps limitation is generalised and applied to the problem of H∞ bumpless transfer for a class of switched linear parameter-varying (LPV) systems. The H∞ bumpless transfer problem is to design a controller with the amplitude limitation and a parameter and modes-dependent switching law to reduce control bumps of the switched LPV systems and satisfy an H∞ performance index. The key point is to guarantee the bumps limitation constraint of the switched LPV systems by dual design of controllers and a switching law, even though the constraint for each subsystem is unsatisfied. First, a set of switching signals depending on parameters and modes are designed, and a family of switched LPV controllers with the bumps limitation objective are developed via multiple parameter-dependent Lyapunov functions. Then, a sufficient condition ensuring the H∞ bumpless transfer performance for a switched LPV system is presented in the format of numerically tractable conditions. Finally, the effectiveness of the proposed control design scheme is illustrated by its application to the control design of an aero-engine.

Observer-based bumpless switching control for switched linear systems with sensor faults

This paper investigates the bumpless transfer problem of switched linear systems with sensor faults. The framework of the switched control systems includes two kinds of controllers, one is for normal use and the other is for fault-tolerant control when sensor faults have occurred. Considering that the information of the sensor faults is unknown to the controller, an observer is designed for the fault-tolerant controller. Moreover, in view of the issue that the output difference between the online and offline controllers may induce undesired oscillations in control input at the switching instant, a bumpless transfer compensator is presented based on sliding mode control. Due to the reasonably designed compensator, the difference can be minimized to a small value to guarantee smooth transitions of the control input when sensor faults have occurred. Finally, numerical simulations verify the effectiveness of the proposed method.

Bumpless switching control for switched systems with partial actuator failures

ABSTRACTThis study is concerned with the bumpless transfer problem for switched systems with partial actuator failures, in order to obtain smooth system performance output transition. Taking into account that the system requires a controller switching from current sub-controller to a fault-tolerant sub-controller after actuator fault. And bumpless transfer for control input cannot be traditionally designed when the actuator fault occurs, while performance smoothing can be considered and it is actually the ultimate goal of bumpless transfer. Specifically, the actuator fault model is firstly established and partial actuator fault is considered. Then, the system performance output signal is deemed as the main design variable of bumpless transfer, and closed-loop control systems both previous and after controller switching are constructed. Moreover, by using model matching thought and the adaptive sliding mode control technique, a bumpless transfer compensator design strategy is given to drive the performance output variable (after controller switching) to track the one of reference model. At last, simulation results of numeric and application examples demonstrate the effectiveness of the proposed bumpless transfer strategy.

Input/output structure of the infinite horizon LQ bumpless transfer and its implications for transfer operator synthesis

AbstractThe steady‐state input/output structure of the infinite horizon LQ bumpless transfer topologies for strictly proper controllers is analyzed. It is found that in these topologies (1) the steady‐state gain of the transfer function from the output of the online controller to that of the offline one is unity/asymptotically unity, and (2) the steady‐state gain of the transfer function from the input of the online controller to the output of the offline one is zero/asymptotically zero, for essentially all strictly proper controllers with the input dimension being no less than the output one. These facts (1) reveal the steady‐state gain structure of the closed‐loop transfer matrix in the standard LQ tracking problems, (2) demonstrate that the LQ bumpless transfer technique solves the ideal bumpless transfer problem for controllers with an integrator in each of their output channels, (3) reveal the structure of unavoidable signal discontinuities in the controller input/output upon transfer between controllers with non‐integrating channels, and (4) provide guidance for minimizing the above signal discontinuities and the resulting bumps in the plant output in bumpless transfer synthesis. Copyright © 2009 John Wiley & Sons, Ltd.

Full Operating Range Robust Hybrid Control of a Coal-Fired Boiler/Turbine Unit

Multi-input-multi-output robust controllers recently designed for the megawatt output/throttle pressure control in a coal-fired power plant boiler/turbine unit have demonstrated performance robustness noticeably superior to that of the currently employed nonlinear PID-based controller. These controllers, however, have been designed only for the range of 150–185MW around the 185MW nominal operating point, exhibiting a significant loss of performance in the lower range of 120–150MW. Through system identification, the reason for this performance loss is demonstrated in the current work to be a pronounced dependence of the boiler/turbine unit steady state gains on the operating point. This problem is addressed via a hybrid control law consisting of two robust controllers and a robust switch between them activated by the set point change. The controllers are designed to cover the corresponding half-ranges of the full operating range. This permits attainment of the desired overall performance as well as reduction of modeling uncertainty induced by the operating point change to approximately 25% of that associated with the previous designs. Robust switching is accomplished through a novel hybrid mode of behavior—robustly controlled discrete transition. The latter mode is produced through realizing that the off-line transfer speedup suggested by Zaccarian and Teel (2005, “The L2(l2) bumpless Transfer Problem for Linear Parts: Its Definition and Solution,” Automatica, 41, pp. 1273–1280) can be taken to the limit and incorporating the result into a robust bumpless transfer technique recently developed by the authors. As demonstrated by simulation results, the proposed strategy provides an adequate solution to the problem of robust boiler/turbine unit performance over the full operating range. This fact combined with numerical algorithm tractability, relative ease of its design, its insensitivity to implementation nonidealities, and accompanying identification methodology for nominal model generation makes it a viable candidate for industrial acceptance.

The [formula omitted] ( [formula omitted]) bumpless transfer problem for linear plants: Its definition and solution

A novel characterization of bumpless transfer among alternative controllers, both in continuous and discrete time, is introduced. The bumpless transfer problem is to design a compensation scheme guaranteeing an L 2 (respectively, l 2 ) bound on the mismatch, after the switching time between the actual plant output and a particular target, ideal response. Minimization of the gain from initial plant state mismatch to L 2 (respectively, l 2 ) plant output mismatch provides improved transients. A solution to the bumpless transfer problem is given, both for plants without input saturation and for plants with input saturation. The solution guarantees anti-windup features in the latter case.

A common framework for anti-windup, bumpless transfer and reliable designs

In this paper, the L2 anti-windup approach introduced in Teel and Kapoor (Proceedings of the Fourth ECC, Brussels, Belgium, July 1997) is generalized and applied to the problem of bumpless transfer in (saturated) multi-controller systems, and to the problem of designing highly reliable saturated control systems exploiting hardware redundancy. We first illustrate the L2 anti-windup technique and apply it to a simple physical example and then demonstrate the performance of its extension to the above-mentioned problems using this example and an example taken from the literature.

Linear quadratic bumpless transfer

The problem of bumpless transfer is posed in the linear quadratic context, and formulae derived for a full-information gain which minimises a certain cost function. These formulae incorporate two weighting matrices to add flexibility to the design, and they can also be used when the controllers in question are non-invertible. Results are given for both continuous and discrete time cases, and both 1 and 2 DOF bumpless transfer is considered. When extended to the infinite horizon, the formulae depend only on known matrices and the solution to a single Riccati equation. Finally, it is shown that the formulae given here reduce to the Hanus Conditioned Transfer formulae under certain circumstances; that is, the results here could be considered as a generalisation of the Hanus technique.

Dynamic transfer among alternative controllers and its relation to antiwindup controller design

Advanced control strategies and modern consulting provide new challenges for the classical problem of bumpless transfer. It can, for example, be necessary to transfer between an only approximately known existing analog controller and a new digital or adaptive controller without accessing any states. Transfer ought to be bidirectional and not presuppose steady state, so that an immediate back-transfer is possible if the new controller should drive the plant unstable. We present a scheme that meets these requirements. By casting the problem of bidirectional transfer into an associated tracking control problem, systematic analysis and design procedures from control theory can be applied. The associated control problem also has a correspondence to the design of antiwindup controllers. The paper includes laboratory and industrial applications.

Dynamic Transfer among Alternative Controllers

Advanced control strategies and modern consulting provide new challenges for the classical problem of bumpless transfer. It can, for example, be necessary to transfer between an only approximately known existing analogue controller and a new digital or adaptive controller without accessing any states. Transfer ought to be bi-directional and not presuppose steady state, so that an immediate back-transfer is possible if the new controller should drive the plant unstable. In this paper we present a scheme that meets these requirements. By casting the problem of bi-directional transfer into an associated control problem, systematic analysis and design procedures from systems theory can be applied. The paper includes laboratory and industrial applications.