The development and experimental evaluation of stabilizing control schemes for a continuous isothermal evaporative pilot crystallizer, equipped with on-line crystal size distribution (CSD) sensors and a system for fin...
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The development and experimental evaluation of stabilizing control schemes for a continuous isothermal evaporative pilot crystallizer, equipped with on-line crystal size distribution (CSD) sensors and a system for fines removal, are discussed. A first-principles modeling procedure is followed to derive models for the crystallizer and the CSD sensors. An output error optimization procedure is applied to estimate unknown empirical parameters of the process model with experimental process data. The experimental results reveal a strong influence of the fines removal rate on CSD dynamics. Two stabilizing control schemes are presented. The first is a simple proportional output feedback scheme which uses information on the number of fines to manipulate the fines removal rate. Experimental results indicate that sufficient stability and dampening can be achieved with this controller. The second scheme is an observer-based control scheme in which information on the actual process state is used to stabilize the CSD by manipulating the fines removal rate. Simulation results demonstrate that this state feedback approach exposes better performance compared to the output feedback approach.
This paper considers an adaptive minimal observer synthesis algorithm based upon a well-known model reference adaptive system strategy. This algorithm gives state and parameter estimation from output feedback alone fo...
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This paper considers an adaptive minimal observer synthesis algorithm based upon a well-known model reference adaptive system strategy. This algorithm gives state and parameter estimation from output feedback alone for single input single output processes and results are presented which illustrate its excellent convergence properties.
The behaviour of manipulators equipped with hydraulic actuators is dominated by the dynamics of the hydraulics. The aim of an inner/outer-loop control structure is to mask these hydraulic dynamics with an inner-loop. ...
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The behaviour of manipulators equipped with hydraulic actuators is dominated by the dynamics of the hydraulics. The aim of an inner/outer-loop control structure is to mask these hydraulic dynamics with an inner-loop. Constructing the inner-loop by using the inverse of the actuator dynamics, or by placing the poles of the actuator system, is fundamentally different. An analysis of these two options concludes that a pole placement is the best choice. First results of an actual implementation of a proposed method on an industrial hydraulic drive system shows the practical relevance of this controller.
We propose a technique for synthesizing robust feedback systems for plants described by nonlinear integro-differential equations (NIDE) with considerable coefficient uncertainties. The technique is based on the concep...
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We propose a technique for synthesizing robust feedback systems for plants described by nonlinear integro-differential equations (NIDE) with considerable coefficient uncertainties. The technique is based on the concept of generalized frequency response functions (GFRF), and exploits recent results that enable ready derivation of these from the NIDE description of the plant. A powerful synthesis procedure that combines the GFRF and quantitative feedback theory (QFT) technique is given. The proposed procedure has several advantages over the existing nonlinear QFT methods. A nonlinear chemical reactor example is solved using the procedure, and is found to yield satisfactory results. (C) 1997 Elsevier Science Ltd.
A model-based controller generally works better with the model than with the modelled plant due to the modelling error. This difference between the performances can be made small by selecting a model that is accurate ...
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A model-based controller generally works better with the model than with the modelled plant due to the modelling error. This difference between the performances can be made small by selecting a model that is accurate at the closed-loop relevant frequencies. In this paper it is shown that an iterative approach of identification and control design can lead to a model that is much better suited for feedback design than a model resulting from an unweighted open-loop identification. In this iteration each identification is performed such that a certain closed-loop criterion function is minimized. This is accomplished by closed-loop identification with persistent set-point excitation and a proper signal filtering Each control design step employs the latest identified model to construct an LOG compensator. The performance requirements are gradually increased during the iteration.
This paper illustrates a number of mathematical procedures associated with the implementation of a method for analysis of linear systems subject to pseudorandom input disturbances. The basic method associated with the...
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This paper illustrates a number of mathematical procedures associated with the implementation of a method for analysis of linear systems subject to pseudorandom input disturbances. The basic method associated with the two-level quantization of a given random input is discussed in detail in [1]. The generalized mean square error proposed by Spooner and Rideout [2] is employed as the performance index.
This paper deals with the problem of determining time-varying parameters in a system described by a linear differential equation from noise-free observations of input/output signals. For the special case of periodical...
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This paper deals with the problem of determining time-varying parameters in a system described by a linear differential equation from noise-free observations of input/output signals. For the special case of periodically varying parameters, two identifiability questions are discussed: 1) how to check whether the available experimental data allow unique determination of system parameters, and 2) how to design the experiment to accomplish this with a priori knowledge. Necessary and sufficient conditions for identifiability are obtained.
Recently, there has been a surge of research on a class of methods called feedback optimization. These are methods to steer the state of a control system to an equilibrium that arises as the solution of an optimizatio...
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This paper is concerned with the practical application control of a pneumatically actuated Stewart-Gough platform with 6-degrees of freedom （6-DOF）. The control approach for motion control of the platform is present...
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This paper is concerned with the practical application control of a pneumatically actuated Stewart-Gough platform with 6-degrees of freedom （6-DOF）. The control approach for motion control of the platform is presented using a modern control technique, namely, linear quadratic Gaussinn （LQG） with reference tracking. The LQG controller is the combination of a Kalman filter, i.e., a linear-quadratic estimator （LQE） with a linear-quadratic regulator （LQR）. The robustness of the control scheme is accessed under various load conditions, and the experimental results are shown.
作者：
VANDERHELM, FCTMan-Machine Systems Group
Laboratory for Measurement and Control Department of Mechanical Engineering Delft University of Technology Delft The Netherlands
The finite element method described in this study provides an easy method to simulate the kinetics of multibody mechanisms. It is used in order to develop a musculoskeletal model of the shoulder mechanism. Each releva...
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The finite element method described in this study provides an easy method to simulate the kinetics of multibody mechanisms. It is used in order to develop a musculoskeletal model of the shoulder mechanism. Each relevant morphological structure has been represented by an appropriate element. For the shoulder mechanism two special-purpose elements have been developed: a SURFACE element representing the scapulothoracic gliding plane and a CURVED-TRUSS element to represent muscles which are wrapped around bony contours. The model contains four bones, three joints, three extracapsular ligaments, the scapulothoracic gliding plane and 20 muscles and muscle parts. In the model, input variables are the positions of the shoulder girdle and humerus and the external load on the humerus. Output variables are muscle forces subject to an optimization procedure in which the mechanical stability of the glenohumeral joint is one of the constraints. Four different optimization criteria are compared. For 12 muscles, surface EMG is used to verify the model. Since the optimum muscle length and force-length relationship are unknown, and since maximal EMG amplitude is length dependent, verification is only possible in a qualitative sense. Nevertheless, it is concluded that a detailed model of the shoulder mechanism has been developed which provides good insight into the function of morphological structures.
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