Showing papers on "Observer (quantum physics) published in 1994"

Applied system identification

Abstract: 1. Introduction. 2. Time-Domain Models. 3. Frequency-Domain Models. 4. Frequency Response Functions. 5. System Realization. 6. Observer Identification. 7. Frequency Domain System ID. 8. Observer/Controller ID. 9. Recursive Techniques. Appendix A: Fundamental Matrix Algebra. Appendix B: Random Variables and Kalman Filter. Appendix C: Data Acquisition.

Full-order observers for linear systems with unknown inputs

Abstract: This note presents a simple method to design a full-order observer for linear systems with unknown inputs. The necessary and sufficient conditions for the existence of the observer are given. >

Observer design for a class of nonlinear systems

Abstract: A viable design methodology to construct observers for a class of nonlinear systems is developed. The proposed technique is based on the off-line solution of a Riccati equation, and can be solved using commercially available software packages. For globally valid results, the class of systems considered is characterized by globally Lipschitz nonlinearities. Local results relax this assumption to only a local requirement. For a more general description of nonlinear systems, the methodology yields approximate observers, locally. The proposed theory is used to design an observer for a single-link flexible joint robot. This observer estimates the robot link variables based on the joint measurements.

On the development of discontinuous observers

Abstract: A framework is proposed for the development and analysis of robust observers for uncertain dynamical systems. A variable structure systems approach is used. Emphasis is placed upon the numerical tractability of the associated synthesis procedure. A selected numerical example is used to illustrate the proposed algorithm.

Adaptive output feedback control of nonlinear systems represented by input-output models

Abstract: We consider a single-input-single-output nonlinear system which can be represented globally by an explicit input-output model. The system is input-output linearizable by feedback and is required to satisfy a minimum phase condition. The nonlinearities are not required to satisfy any global growth condition. The model depends linearly on unknown parameters which belong to a known compact, convex set. We design a semiglobal adaptive output feedback controller which ensures that the output of the system tracks any given reference signal which is bounded and has bounded derivatives up to the (n+l)th order, where n is the order of the system. The reference signal and its derivatives are assumed to belong to a known compact set. It is also assumed to be sufficiently rich to satisfy a persistence of excitation condition. The design process is simple. First we assume that the output and its derivatives are available for feedback and design the adaptive controller as a state feedback controller in appropriate coordinates. Then we saturate the controller outside a domain of interest and use a high-gain observer to estimate the derivatives of the output. We prove, via asymptotic analysis, that when the speed of the high-gain observer is sufficiently high, the adaptive output feedback controller recovers the performance achieved under the state feedback one. >

Statistically defined backgrounds: performance of a modified nonprewhitening observer model.

Abstract: Research on human-observer performance for noise-limited tasks (such as those found in medical imaging) has recently progressed to investigations in which some signal or image parameters are statistically defined. In these cases the ideal-observer procedure is usually nonlinear, and analysis is mathematically intractable. Two suboptimal but linear observer models have been proposed for mathematical convenience. The Hotelling observer is the optimal linear model and has been found to give a good fit to most human results. The nonprewhitening (NPW) matched filter also has been useful for explanation of some human results. Rolland and Barrett [J. Opt. Soc. Am. A 9, 649 (1992)] recently reported human results for detection of signals in white noise superimposed on statistically defined (lumpy) backgrounds in experiments that simulated nuclear medicine imaging systems. They found that the Hotelling model gave a good fit, whereas the simple NPW matched filter gave a poor fit. It is shown that the NPW model can also fit their data if a spatial frequency filter of a shape similar to the human contrast-sensitivity function is added to the NPW observer model. The best fit is achieved by use of an eye-filter model E(f) = f1.3 exp(-cf2), with c selected to yield a peak at 4 cycles/deg.

Observer-based direct fiels orientation : analysis and comparison of alternative methods

Abstract: This paper focuses on methods of achieving direct field orientation (DFO) of induction machines based on closed-loop, stator, and rotor flux observers which are well suited to both zero and very high-speed operation. Both observer topologies are dominated by a current model at zero and low speeds, and a voltage model at high speeds. Application of such rotor and stator flux observers to both stator and rotor direct field orientation is presented, including experimental results for three different methods. The influence which flux regulation has on parameter sensitivity of the complete DFO system is analyzed. A rotor-flux-regulated and -oriented system is shown to be sensitive to leakage inductance under high slip (i.e., field weakened) operation

On the novel approach to the design of unknown input observers

Abstract: In the papers, a new method to design unknown input observer and its existence conditions are presented. We show that such conditions are equivalent to those generally adopted for unknown inputs observers. >

Robust control of robots via linear estimated state feedback

Abstract: In this note we propose a robust tracking controller for robots that requires only position measurements. The controller consists of two parts: a linear observer part that generates an estimated error state from the error on the joint position and a linear feedback part that utilizes this estimated state. It is shown that this computationally efficient controller yields semi-global uniform ultimate boundedness of the tracking error. An interesting feature of the controller is that it straightforwardly extends results on robust control of robots by linear state feedback to linear estimated-state feedback. >

On residual generation by observer and parity space approaches

Abstract: A unifying framework for observer design by eigenstructure assignment is described. A new technique for structured residual generation, based on this framework, is proposed. One of the main features of this technique is that the equivalence between residual generation by means of observers or parity space devices are made conspicuous. More precisely, from a computational point of view, the equations to solve in both cases are shown to be similar, and for implementation, both devices are shown to be identical. A necessary and sufficient condition for the existence of structured residuals is given. Finally the sensitivity of structured residuals to nondecoupled failures is studied and a procedure for maximizing this sensitivity is described. >

Observer-a concept for formal on-line validation of distributed systems

Abstract: Proposes the observer concept for designing self-checking distributed systems, i.e. systems that detect erroneous behaviors as soon as errors act at some observable output level. The approach provides a solution to build systems whose on-line behavior is checked against a formal model derived from a formal description. In other words, the actual implementation is continuously checked against a reference, this reference being a formal and verified model of some adequately selected aspects of the system behavior. The corresponding methodology, the software concepts and some applications of the observer are presented. General definitions are given first that theoretically define self-checking systems as systems that include and implement complete on-line validation. The basic concepts and the difficulties to implement self-checking validation are then given. In order to provide simple implementations, the previous definitions are weakened to design quasi-self-checking observers for LANs using a broadcast service. Three specific applications are given to illustrate the proposed approach: testing a virtual ring MAC protocol, checking the link and transport layers in an industrial LAN, and managing a complete OSI layering, from layer 2 to layer 6, in an open system architecture. >

Interpolation and numerical differentiation for observer design

Abstract: This paper explores interpolation and numerical differentiation as a basis for constructing a new approach to the design of nonlinear observers.

On the concepts of regulator and observer of fuzzy control systems

Abstract: Deals with design procedures for fuzzy regulators and fuzzy observers, which are the most important and basic concepts for fuzzy control system design. First, a design problem for a fuzzy regulator which consists of fuzzy state feedback laws is solved by extending the idea of modem control theory. Next, the concept of a fuzzy observer, which estimates the states of fuzzy dynamic plants, is introduced. Finally, a design algorithm for a fuzzy control system containing a fuzzy regulator and a fuzzy observer is constructed. The fuzzy regulator guarantees the stability of the fuzzy control system in accordance with the definition of stability in the sense of Lyapunov. The fuzzy observer guarantees that the estimation error for the states of the fuzzy dynamic plants converges to zero. The 'separate theorem', which guarantees that one should be able to design regulators and observers separately, cannot be applied to the case of the design of fuzzy regulators and fuzzy observers. >

Parameterization of linear observers and its application to observer design

Abstract: With the aid of the factorization approach linear observers and their estimation error dynamics are parameterized. This result provides a dual representation of the well-known linear controller parameterization and gives a new insight into the observer design which may be used for the observer construction and robust observer design. >

A reduced order observer based controller design for H/sub /spl infin//-optimization

Abstract: In this note the H/sub /spl infin// control problem with measurement feedback is investigated. It is well-known that for this problem, in general, we need controllers of the same dynamic order as the given system. However, in the case that some entries of the measurement vector are not noise-corrupted, we show that one can find dynamic compensators of a lower dynamical order. Note that this implies that the standard assumptions on the direct feedthrough matrices, as made in most papers on H/sub /spl infin// control, are not satisfied. Our result can be derived by using reduced order observer based controllers. >

A nonlinear reduced order observer for permanent magnet synchronous motors

Abstract: This paper introduces a nonlinear reduced order observer for speed and rotor position estimation in permanent magnet synchronous motors (PMSM). The observer is based on the model of the motor represented in the stationary two-axes coordinates. The theoretical principles of the proposed observer are discussed. Sufficient conditions for convergence as well as convergence speed are established. The observer is designed and tested by simulation. The results show that the observer gives a good estimation of speed and rotor position. In addition, it has low sensitivity to torque disturbances and perturbations of the mechanical parameters. >

Neural network observer for induction motor control

Abstract: In many practical problems the task is the control of a nonlinear plant, under parameter uncertainty, by a controller of known structure that uses the values of the state variables. However, it frequently is the case that some state variables cannot be measured. In this article this type of problem arises from the control requirements of an induction motor and is tackled by neural network based observer techniques so that the state variables are estimated while the variations of the unknown parameters are compensated for. Extensive simulations have shown that this scheme works well in the case of motor control. >

Recovering shape by purposive viewpoint adjustment

Abstract: We present an approach for recovering surface shape from the occluding contour using an active (i.e., moving) observer. It is based on a relation between the geometries of a surface in a scene and its occluding contour: If the viewing direction of the observer is along a principal direction for a surface point whose projection is on the contour, surface shape (i.e., curvature) at the surface point can be recovered from the contour. Unlike previous approaches for recovering shape from the occluding contour, we use an observer thatpurposefully changes viewpoint in order to achieve a well-defined geometric relationship with respect to a 3-D shape prior to its recognition. We show that there is a simple and efficient viewing strategy that allows the observer to align the viewing direction with one of the two principal directions for a point on the surface. This strategy depends on only curvature measurements on the occluding contour and therefore demonstrates that recovering quantitative shape information from the contour does not require knowledge of the velocities or accelerations of the observer. Experimental results demonstrate that our method can be easily implemented and can provide reliable shape information from the occluding contour.

Observer Design for Electronic Suspension Applications

Abstract: SUMMARY This paper proposes a new methodology for designing observers for automotive suspensions. Automotive suspensions are disturbance-affected dynamic systems. Semi-active suspensions are bilinear while active suspensions with hydraulic actuators are nonlinear. The proposed methodology guarantees exponentially convergent state estimation for both these systems. It uses easily accessible and inexpensive measurements. The fact that sprung mass absolute velocity of the suspension cannot be estimated in an exponentially stable manner with such measurements is also demonstrated. Controllers using estimated states are implemented experimentally on the Berkeley Active Suspension Test Rig. Experimental results for two cases are presented : use of observer states to improve ride quality in an active suspension and use of observer states to reduce dynamic tire loading in a semi-active heavy vehicle suspension.

A sliding mode controller in single phase voltage source inverters

Abstract: This paper deals with a sliding mode controller for a single phase inverter used in UPS applications. The proposed system provides overload and short circuit protection. It can operate in constant or variable frequency. The use of a reduced order observer eliminates the requirement of the load current measurement and improves the noise immunity. Experimental results obtained in laboratory are presented and they confirm the simulation and theoretical analysis. >

Observer-based sliding mode control of a robotic manipulator

Abstract: This paper presents a new approach for the design of variable structure control (VSC) of nonlinear systems. The approach is based on estimation of joint acceleration signals with introduction of load estimation with the asymptotic observer. The control system is insensitive to parameter variations for a chosen switching hypersurface in conditions when it is reached by the dynamic motion with the required dynamics. The parameter insensitive response provided by this control method is demonstrated on the model of the SCARA robot. Simulation results confirm the validity of accurate tracking capability and the robust performance.

Feedforward time-delay structures in state estimation: finite memory smoothing and continuous deadbeat observers

Abstract: The paper investigates the possibilities of using a feedforward time-delay structure for state estimation and smoothing in linear continuous dynamic systems. A fixed-lag finite-memory smoother and a continuous deadbeat observer are shown to be described by a linear combination of delayed measurements of the system inputs and outputs. To facilitate implementation of the observer-based controllers an infinite-memory deadbeat observer is introduced. Design methods are illustrated by numerical examples. >

Observing Complexity and the Complexity of Observation

Abstract: The distortions introduced by the measurement process can lead to drastic consequences for an observer’s ability to infer structure in its environment. Several examples illustrate the appearance of infinite complexity and irreducible indeterminacy in classical, deterministic processes. Along the way several notions of complexity and an approach to a general solution — hierarchical machine reconstruction — are reviewed.

Occluding Contour Detection Using Affine Invariants and Purposive Viewpoint Control

Abstract: We present an approach for identifying the occludin,p contour and determining its sidedness using an active (i.e., moving) observel: It is bused on the non-stationarity property of the visible rim: When the observer’s viewpoint is changed, the visible rim is a collection of curves that “slide,” rigidly or non-rigidly, over the surface. We show that the observer can deterministically choose three views on the tangent plane of selected sulface points to distinguish such curves from stationary surface curves (i.e., surface markings). Our approach demonstrates that the occluding con tour can be identijed directly, i.e., withoutjrst computing surface shape (distance and curvature).

Fuzzy logic based threshold adaption for fault detection in robots

Abstract: The residual evaluation of model-based fault detection methods is investigated for processes which exhibit unstructured disturbances, e.g. due to model simplifications. Since analytical methods can only be used for structured disturbances the use of heuristic knowledge for residual evaluation is appropriate. A fuzzy logic based threshold for residual evaluation is suggested. The benefit of this approach is demonstrated for an observer-based fault detection method of robots. >