A design method that makes a trade-off between noise reduction and stability requirements is suggested in the case when the process is modelled as a time invariant linear stable plant. The suggested controller is obta...
详细信息
A design method that makes a trade-off between noise reduction and stability requirements is suggested in the case when the process is modelled as a time invariant linear stable plant. The suggested controller is obtained by modifying the well known LQG-controller. Only the SISO-case is treated here. We give analytical expressions on how stability margins can be improved and how the stochastic properties will change using the suggested nonoptimal controller.
For an efficient identification of large scale systems it is advisable to decompose the entire system into separately treatable subsystems of lower complexity. In most applications these subsystems are of a certain st...
详细信息
For an efficient identification of large scale systems it is advisable to decompose the entire system into separately treatable subsystems of lower complexity. In most applications these subsystems are of a certain structure. In this paper a method is proposed for identifying the parameters of these subsystems by decomposing them into interconnected transfer functions which are linear in their parameters. The identification algorithm operating recursively/iteratively is derived by partitioning and optimizing a cost function with respect to the parameter vectors of the transfer functions. The advantage of this method is that the identification procedure for the subsystems is feasible by applying linear filters to each transfer function without calculating a common denominator, such that the number of parameters to be identified, is minimal and the system structure is saved during the identification procedure
A practical fault detection scheme based on a model discrimination approach is proposed for dynamical systems with various failure modes which can not he explicitly described by mathematical representations. Using ARX...
详细信息
A practical fault detection scheme based on a model discrimination approach is proposed for dynamical systems with various failure modes which can not he explicitly described by mathematical representations. Using ARX modelling, the Kullback Discrimination Information (KDI) is adopted as a model distortion measure to detect dynamics failures. In order to calculate the KDI for finite but large data sets with-out dealing with very large matrices, we derive an iterative algorithm of low dimension based on Baye' rule. The KDI is used as a detection index in a thresholding approach. This detection scheme can be combined with identification to diagnose the system operating mode. The effectiveness of the method has been confirmed through a simulation study of a second order servo system.
Three direct methods for the identification of a linear continuous-time system from the samples of input and output observations are considered. These are based on obtaining approximate expressions for the signals fro...
Three direct methods for the identification of a linear continuous-time system from the samples of input and output observations are considered. These are based on obtaining approximate expressions for the signals from their samples. The methods are (i) block-pulse functions, (ii) trapezoidal pulse functions, and (iii) cubic spline functions. In each case, the differential equations are integrated using these approximations and the results are used for estimating the parameters of a model of given order and structure which will provide the best fit in the least squares sense. Results of simulation are included which compare the relative performance of the three methods both in the absence and the presence of measurement noise.
The Kullback discrimination index can be used to test whether two models obtained from different data sets are equal or not. Such an index can be used for model validation, which then is carried out as a crossvalidati...
详细信息
The Kullback discrimination index can be used to test whether two models obtained from different data sets are equal or not. Such an index can be used for model validation, which then is carried out as a crossvalidation. However, the form of the index and its implementation differ from traditional crossvalidation. Some simple validation criteria are developed from this index, and also numerically illustrated.
Material transportation systems with constant flow feeding hoppers at their ends may be described by a variable dead time process with an integrator. Smith's predictor based control techniques will not perform wel...
Material transportation systems with constant flow feeding hoppers at their ends may be described by a variable dead time process with an integrator. Smith's predictor based control techniques will not perform well with these astatic processes. Therefore an adaptive control strategy, based on pole placement, is developed. The adaptive controller includes an integrator and a parallel correction network. The correction network output augments the process output and the controller acts on the basis of the combined signal. Hybrid simulation studies show that by properly choosing the poles, the desired performance and necessary immunity against noise can be obtained. The recovery following a disturbance is good without offset. The dead time variations are handled very well. To demonstrate its physical realization feasibility, the scheme is tested on a material transportation system with a nonlinear actuator. All the minor lags have been neglected and the process is approximately modeled as a variable dead time-integrator system. The performance is commendable for set point, load and dead time variations.
We investigate the design of identification experiments using some recent asymptotic expressions for the variance of the estimated transfer function. In particular we highlight a number of applications for which it is...
We investigate the design of identification experiments using some recent asymptotic expressions for the variance of the estimated transfer function. In particular we highlight a number of applications for which it is beneficial to let the experiment be carried out in closed loop.
The recently obtained evidence of the need for a positive real element in an adaptive system leaves us with a disturbing gap in adaptive control theory. It is a fact that in some applications adaptive controllers are ...
详细信息
The recently obtained evidence of the need for a positive real element in an adaptive system leaves us with a disturbing gap in adaptive control theory. It is a fact that in some applications adaptive controllers are performing well in practice. How can these systems behave well in practical situations which must contain modeling error? This paper introduces a preliminary result which indicates that it may be possible to maintain the needed positive real system in the presence of modeling error. The result shows that if a continuous-time system with large high frequency uncertainty is treated appropriately with antialiasing filters and sampled slowly enough, the resulting discrete-time system may contain very little uncertainty. With small enough uncertainty in the plant, a positive real system in the adaptive loop is possible.
In this paper, two theorems are quoted which, when applied together, provide much information about the robustness of adaptive control schemes. From these two theorems, another theorem is developed which can explain w...
详细信息
In this paper, two theorems are quoted which, when applied together, provide much information about the robustness of adaptive control schemes. From these two theorems, another theorem is developed which can explain why adaptive controllers can perform robustly in certain practical situations, while possibly failing in other situations. In particular, if the bandwidth constraints on a control systems are lenient enough to allow the use of a sampling frequency which is smaller than the frequency at which unstructured uncertainty becomes significant, an adaptive controller can behave robustly. Many, if not all, of the applications of adaptive control which have been successful employ relatively slow sampling of the process. Thus, the results of this paper provide a theoretical explanation of how certain adaptive controllers are performing robustly in practice. In addition, the final theorem is of a form which provides insight into what a priori knowledge is required to achieve robust adaptive control and how this knowledge say be used.
暂无评论