| 1. |
- Bengtsson, Gunnar, et al.
(författare)
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A design scheme for incomplete state or output feedback with applications to boiler and power system control
- 1974
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Ingår i: Automatica. - : Elsevier BV. - 0005-1098. ; 10:1, s. 15-30
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Tidskriftsartikel (refereegranskat)abstract
- The problem of designing a linear feedback when all state variables are not available is discussed. The design scheme is based on computation of a complete state feedback and a reduction to a specified structure. The reduction is made by approximation of the eigenspace corresponding to a set of dominant eigenvalues. The method consists of successive choices of weightings on this space. The method is applied to the control of a boiler and a three-machine power system. In the power system case the complete state feedback can be replaced by local output feedback without significant decrease in performance.The examples indicate that the proposed method is a realistic design method for multivariable systems.
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| 2. |
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| 3. |
- Hagander, Per
(författare)
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Inversion of a dynamical system by an operator identity
- 1972
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Ingår i: Automatica. - : Elsevier BV. - 0005-1098. ; 8, s. 361-362
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Tidskriftsartikel (refereegranskat)abstract
- Inversion of a linear dynamical system is shown to be an operator equivalence to the well-known matrix lemma: (D + CLB)−1 = [D−1 − D−1C(L−1 + BD−1C)−1BD−1]
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| 4. |
- Hagander, Per
(författare)
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The use of operator factorization for linear control and estimation
- 1973
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Ingår i: Automatica. - : Elsevier BV. - 0005-1098. ; 9:5, s. 623-631
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Tidskriftsartikel (refereegranskat)abstract
- The linear filtering, prediction and smoothing problems as well as the linear quadratic control problems can very generally be formulated as operator equations using basic linear algebra.The equations are of Fredholm type II, and they are difficult to solve directly.It is shown how the operator can be factorized into two Volterra operators using a matrix Riccati equation. Recursive solution of these triangular operator equations is then obtained by two initial value differential equations.The proofs of smoothing and optimal control under known disturbances are in this way especially clear and simple.
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| 5. |
- Hansson, Anders, et al.
(författare)
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Existence of Minimum Upcrossing Controllers
- 1997
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Ingår i: Automatica. - 0005-1098. ; 33:5, s. 871-879
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Tidskriftsartikel (refereegranskat)abstract
- An optimal stochastic control problem that minimizes the probability that a signal upcrosses a level is solved by rewriting it as a one-parametric optimization problem over a set of LQG control problem solutions. Finding the optimal controller can be interpreted as finding an optimal costing transfer function. The existence of the optimal controller is investigated in a constructive way, and it is shown that it is equivalent to the existence of a controller with sufficiently small closed-loop variance of the controlled signal.
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| 6. |
- Hägglund, Tore, et al.
(författare)
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Industrial Adaptive Controllers Based on Frequency Response Techniques
- 1991
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Ingår i: Automatica. - : Elsevier BV. - 0005-1098. ; 27:4, s. 599-609
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes several adaptive techniques based on frequency response analysis, which are used in industrial controllers. Automatic tuning is used to obtain PID controller parameters, to build up gain schedules, and to initialize adaptive algorithms. A simple adaptive feedback algorithm which is based on the idea of tracking a point on the Nyquist curve is presented as well as an adaptive feedforward procedure. The adaptive techniques have been implemented in various industrial products. Industrial experiences from using the controllers are summarized in the paper.
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| 7. |
- Hägglund, Tore, et al.
(författare)
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Supervision of adaptive control algorithms
- 2000
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Ingår i: Automatica. - 0005-1098. ; 36:8, s. 1171-1180
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Tidskriftsartikel (refereegranskat)abstract
- An adaptive controller needs supervisoryfunctions in order to function well in an industrial environment.This paper describes these needs, and provides examplesof supervisory functions that presently are used in industrialadaptive controllers. These supervisory functions ensure thatadaptation only is performed when proper excitation is available.Supervisory functions that prohibit adaptation during the firstphase of a load disturbance response, during signal saturationand oscillations caused by nonlinearities are also proposed.
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| 8. |
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| 9. |
- Johansson, Rolf, et al.
(författare)
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Observer-based strict positive real (SPR) feedback control system design
- 2002
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Ingår i: Non-Linear Control Systems 2001, vols 1-3. - 0962-9505. ; 38:9, s. 1557-1564
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Konferensbidrag (refereegranskat)abstract
- This paper presents theory for stability analysis and design for a class of observer-based feedback control systems. Relaxation of the controllability and observability conditions imposed in the Yakubovich-Kalman-Popov (YKP) lemma can be made for a class of nonlinear systems described by a linear time-invariant system (LTI) with a feedback-connected cone-bounded nonlinear element. It is shown how a circle-criterion approach can be used to design an observer-based state feedback control which yields a closed-loop system with specified robustness characteristics. The approach is relevant for design with preservation of stability when a cone-bounded nonlinearity is introduced in the feedback loop. Important applications are to be found in robotics (force control) and nonlinear control in hybrid control. Copyright (C) 2001 IFAC.
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| 10. |
- Kuipers, Benjamin, et al.
(författare)
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The Composition and Validation of Heterogeneous Control Laws
- 1994
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Ingår i: Automatica. - : Elsevier BV. - 0005-1098. ; 30:2, s. 233-249
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Tidskriftsartikel (refereegranskat)abstract
- We present a method for creating and validating a nonlinear controller by the composition of heterogeneous local control laws appropriate to different operating regions. Like fuzzy logic control, these methods apply even in the presence of incomplete knowledge of the structure of the system, the boundaries of the operating regions, or even the control action to take. Unlike fuzzy logic control, these methods can be analyzed by a combination of classical and qualitative methods. Each operating region of the system has a classical control law, which provides high-resolution control and can be analyzed by classical methods. Operating regions are defined by fuzzy set membership functions. The global control law is the weighted average of the local control laws, where the weights are provided by the operating region membership functions. A heterogeneous control law can be analyzed, even in the presence of incomplete knowledge, by representing it as a qualitative differential equation and using qualitative simulation to predict the set of possible behaviors of the system. By expressing the desired guarantee as a statement in a modal temporal logic, the validity of the guarantee can be automatically checked against the set of possible behaviors. We demonstrate heterogeneous controllers and our qualitative methods for proving their properties, first for a simple level controller for a water tank, and second for a highly nonlinear chemical reactor.
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