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Control Theory and Applications, IEE Proceedings D

Issue 2 • Date Mar 1992

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Displaying Results 1 - 25 of 30
  • Sliding mode control of an electrically powered industrial robot

    Publication Year: 1992 , Page(s): 207 - 225
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1032 KB)  

    Considers the multivariable control of anthropomorphic robot manipulators, and its objective is to develop a control technique which exploits the full potential of the performance of robot arms. In its ideal form, the computed torque technique achieves the desired performance in nonlinear time-varying systems. However, its stability cannot be guaranteed, and its performance deteriorates rapidly with the presence of disturbances and parametric uncertainties. The variable structure control strategy which can guarantee stability, given bounded parametric uncertainty, is used as an additional input to rectify the uncertainties in the estimated control model of the computed torque technique. The benefits of the combined computed torque/variable structure controller are demonstrated practically on an electrically powered industrial robot, and the performance of the proposed controller is compared to that of the computed torque technique. View full abstract»

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  • Identification of linear time-invariant systems from frequency-response data corrupted by bounded noise

    Publication Year: 1992 , Page(s): 135 - 140
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (368 KB)  

    A unified approach is developed for identification of linear time-invariant systems. It is shown that, given the experimental frequency-response data of the system, the plant can be identified using a simple, numerically reliable algorithm. Further, an error bound is derived for exponentially stable systems when the frequency-response data are corrupted by bounded noise. An example is presented to illustrate the proposed algorithm. View full abstract»

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  • Design of algorithms for spatial-time reduction complexity of dynamic programming

    Publication Year: 1992 , Page(s): 172 - 180
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (464 KB)  

    The objective of the paper is the search for algorithms to reduce the spatial-time complexity of dynamic programming with the aim of using them to solve optimal control problems. These algorithms have been verified in second-order continuous systems, with indexes of performance where the time explicitly appears. The use of such algorithms is vital when dealing with third-order systems and second-order stochastic systems. View full abstract»

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  • Control of distributed parameter systems: localisation method

    Publication Year: 1992 , Page(s): 141 - 146
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (356 KB)  

    The problem of forming desired transients for systems which are governed by partial differential equations is discussed. It is assumed that information about external disturbances is incomplete and that there are finite dimensional controls. The design method called the localisation method is used. Such problems as choices of structure of the control law, realisability conditions, control accuracy, influence of the differentiating filters and noises, are considered. Simulation results are also presented. View full abstract»

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  • Parallel computation of robot inverse dynamics for high speed motions

    Publication Year: 1992 , Page(s): 226 - 236
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (692 KB)  

    The computation of the highly coupled dynamic equations has always posed a bottleneck in real-time dynamic control of robot manipulators. In the paper an attempt is made to review the subject of the parallel computation of robot dynamics. Moreover, a new and highly efficient technique is introduced to solve this problem. A simplified form of the Lagrange-Euler is divided into subtasks and distributed on to a parallel processing system. The development system employs several INMOS transputers running the OCCAM concurrent programming language. Further, the system is used to introduce parallelism to robot dynamics through different task allocation strategies. The cost effectiveness and speed of the algorithm are demonstrated by a case study. Comparisons are made between uniprocessor and parallel implementations of the algorithm. Several measures such as utilisation, efficiency, and speed up are used to evaluate the performance of the employed networks and task allocations. View full abstract»

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  • Application of frequency dependent Lyapunov equation of 2-dimensional problems

    Publication Year: 1992 , Page(s): 197 - 203
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (328 KB)  

    The application of the frequency dependent Lyapunov equation to the study of some problems in 2-dimensional discrete systems is examined. The stability of 2-dimensional discrete systems is first considered, and a new method for the evaluation of 2-dimensional complex integrals is then presented. View full abstract»

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  • Fault detection in large-scale stochastic dynamic systems

    Publication Year: 1992 , Page(s): 119 - 124
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (276 KB)  

    A new approach is developed for fault detection in linear stochastic interconnected dynamic systems, based on designing a set of decentralised Kalman filters for the subsystems resulting from overlapping decomposition of the overall large-scale system. The malfunctioning sensors can be detected and isolated by comparing the estimated values of a single state from different Kalman filters. The new method is applied to a sixth-order system represented by a ladder network. View full abstract»

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  • Multirate adaptive inferential estimation

    Publication Year: 1992 , Page(s): 181 - 189
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (456 KB)  

    An adaptive inferential algorithm is developed for estimation and control of multirate systems. The output y is measured J times slower than the secondary process output v and the input u, but an output estimate ye is produced at each sampling interval of v and u. Compared with previous work on multirate inferential systems, the proposed algorithm has a more formal theoretical basis. For example, the output y is related to the secondary output v not only through external stochastic disturbances but also through the internal system structure. Convergence properties are formally proven for the case of zero external stochastic disturbances, and a simplified algorithm is proposed for practical applications. Simulated results illustrate the convergence properties of the algorithm and the improvement obtained in simple feedback control systems. The algorithm has direct application in the process industries. View full abstract»

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  • Class of stabilising decentralised controllers for interconnected dynamical systems

    Publication Year: 1992 , Page(s): 125 - 134
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (624 KB)  

    A method is presented for the systematic design of stabilising decentralised controllers for large-scale interconnected dynamical systems. The design method is based on: decentralised implementation of global controllers obtained by using existing global controller design methods; model reduction of dynamical systems; and modelling of the interactions among the subsystems comprising the global closed-loop control system. This is used for generating local corrective control signals, which would account for these interactions. The resulting decentralised controller uses local information only to generate local control inputs. It comprises local state feedback controllers and feedforward compensators. Three distinct schemes for the implementation of the controller are proposed. They all guarantee near optimal performance. A four-station interconnected dynamical system is considered. Results of time simulation studies demonstrate that the overall performance of the system under the proposed global optimal controller. View full abstract»

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  • Adaptive implementation of internal model principle for continuous time systems

    Publication Year: 1992 , Page(s): 167 - 171
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (256 KB)  

    It is shown that without persistent excitation the adaptive control system with the internal model principle is globally stable in that the plant input and output remain bounded. It is also shown that the stability of the adaptive control system is still maintained in the presence of plant unmodelled dynamics and other bounded disturbances. View full abstract»

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  • Youla parameterised two and a half degrees of freedom LQG controller and robustness improvement cost weighting

    Publication Year: 1992 , Page(s): 147 - 160
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (772 KB)  

    A polynomial solution to the LQG optimal control problem is presented for a system with special controller structure and robust cost-weighting terms. The controller structure has the advantages of both single- and two-degrees-of-freedom designs. The effect of introducing a common robustness weighting term in the cost index is considered. It is shown that this leads to an additional gain term in the Youla parameterised form of the controller. To illustrate the advantages of the controller structure and the influence of the robustness weighting term, a flight control system design example is presented. View full abstract»

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  • Generalisation of conditioning technique for anti-windup compensation

    Publication Year: 1992 , Page(s): 109 - 118
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (708 KB)  

    For linear controllers, the anti-windup compensator based on conditioning technique is often treated as a special case of the generalised anti-windup compensator. The conditioning technique is then defined simply by a special observer in the generalised anti-windup compensator. Instead, in the paper the concept of back calculation or the modified setpoint is emphasised, which is indeed the conceptual basis for the derivation of the conditioning technique. The behaviour of the modified setpoint is investigated by use of a simple example, and an inherent weakness in the conditioning technique is demonstrated. A simple modification to the conditioning technique that reduces the effect of short-sightedness is presented, and its anti-windup compensation properties are investigated. Also, a general approach to the conditioning technique is proposed by introducing a filtered setpoint. This approach provides a parameterisation to deal not only with the short-sightedness problem but also with the other drawbacks of the conditioning technique. An important outcome of this generalisation is that it unifies and interprets through the conditioning technique a class of AWCs described in the literature. View full abstract»

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  • Polynomial optimisation of discrete-time multivariable regulators

    Publication Year: 1992 , Page(s): 190 - 196
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (452 KB)  

    The polynomial equation approach to the design of optimal discrete-time multivariable regulators is studied. Kucera's solution to the problem is rederived in the light of work concerning the role, and the necessity, of the various matrix diophantine equations which appear. In particular, a constructive derivation of the pair of coupled bilateral matrix diophantine equations, which the optimal controller matrices satisfy, is given. The conditions are reviewed under which only one of the bilateral equations may be used to calculate the unique optimal controller. As a simpler alternative, the conditions under which a single unilateral equation (related to the original couple of bilateral equations) may be used are also reviewed. Finally, guided by these theoretical results, a formal design procedure is given that exploits the advantages of using these simplifications. View full abstract»

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  • Recursive state and parameter estimation of SISO singular systems

    Publication Year: 1992 , Page(s): 204 - 206
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (156 KB)  

    Recursive algorithms are presented for the online state and parameter estimation of a linear time invariant single-input single-output discrete-time singular system. The model considered is in the canonical observable form. The approach is based on the generalised Kalman filter and can be developed in two steps. First, the parameters are estimated by recursive least squares method. These parameters are then used to estimate the state by the generalised Kalman filter in the second step. The results are illustrated by a numerical example. View full abstract»

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  • Integral variable structure control approach for robot manipulators

    Publication Year: 1992 , Page(s): 161 - 166
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (272 KB)  

    An integral variable structure control (IVSC) approach for robot manipulators is presented to achieve accurate servo-tracking in the presence of load variations, parameter variations and nonlinear dynamic interactions. A procedure is proposed for choosing the control function so that it guarantees the existence of the sliding mode and for determining the coefficients of the switching plane and the integral control gain such that the IVSC approach has the desired properties. Furthermore, a modified proper continuous function is introduced to overcome the chattering problem. The proposed IVSC approach has been simulated for the first three links of a PUMA 560 robot arm as an illustration. The simulation results demonstrate the potential of the proposed scheme. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Generalisation of conditioning technique for anti-windup compensators

    Publication Year: 1992 , Page(s): 109 - 118
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (855 KB)  

    For linear controllers, the anti-windup compensator based on conditioning technique is often treated as a special case of the generalised anti-windup compensator. The conditioning technique is then defined simply by a special observer in the generalised anti-windup compensator. Instead, in this paper the concept of back calculation or the modified setpoint is emphasised, which is indeed the conceptual basis for the derivation of the conditioning technique. The behaviour of the modified setpoint is investigated by use of a simple example, and an inherent weakness ('short-sightedness') in the conditioning technique is demonstrated. A simple modification to the conditioning technique that reduces the effect of short-sightedness is presented, and its anti-windup compensation properties are investigated. Also, a general approach to the conditioning technique is proposed by introducing a filtered setpoint. This approach provides a parameterisation to deal not only with the short-sightedness problem but also with the other drawbacks of the conditioning technique. An important outcome of this generalisation is that it unifies and interprets through the conditioning technique a class of AWCs described in the literature. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Fault detection in large-scale stochastic dynamic systems

    Publication Year: 1992 , Page(s): 119 - 124
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (344 KB)  

    A new approach is developed for fault detection in linear, stochastic, interconnected dynamic systems, based on designing a set of decentralised Kalman filters for the subsystems resulting from overlapping decomposition of the overall large-scale system. The malfunctioning sensors can be detected and isolated by comparing the estimated values of a single state from different Kalman filters. The new method is applied to a sixth-order system represented by a ladder network. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Class of stabilising decentralised controllers for interconnected dynamical systems

    Publication Year: 1992 , Page(s): 125 - 134
    Cited by:  Patents (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (751 KB)  

    A method is presented for the systematic design of stabilising decentralised controllers for large-scale interconnected dynamical systems. The design method is based on (i) decentralised implementation of global controllers obtained by using existing global controller design methods, (ii) model reduction of dynamical systems, and (iii) modelling of the interactions among the subsystems comprising the global closed-loop control system. This is used for generating local corrective control signals, which would account for these interactions. The resulting decentralised controller uses local information only to generate local control inputs. It comprises local state feedback controllers and feedforward compensators. Three distinct schemes for the implementation of the controller are proposed. They all guarantee near optimal performance. A four-station interconnected dynamical system is considered. Results of time simulation studies demonstrate that the overall performance of the system under the proposed decentralised controller is near that of the global optimal controller. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Identification of linear time-invariant systems from frequency-response data corrupted by bounded noise

    Publication Year: 1992 , Page(s): 135 - 140
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (455 KB)  

    A unified approach is developed for identification of linear time-invariant systems. It is shown that, given the experimental frequency-response data of the system, the plant can be identified using a simple, numerically reliable algorithm. Further, an error bound is derived for exponentially stable systems when the frequency-response data are corrupted by bounded noise. An example is presented to illustrate the proposed algorithm. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Control of distributed parameter systems: localisation method

    Publication Year: 1992 , Page(s): 141 - 146
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (441 KB)  

    In this paper, the problem of forming desired transients for systems which are governed by partial differential equations is discussed. It is assumed that information about external disturbances is incomplete and that there are finite dimensional controls. The design method called the localisation method is used. Such problems as choices of structure of the control law, realisability conditions, control accuracy, influence of the differentiating filters and noises, are considered. Simulation results are also presented. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Youla parameterised two and a half degrees of freedom LQG controller and robustness improvement cost weighting

    Publication Year: 1992 , Page(s): 147 - 160
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (940 KB)  

    A polynomial solution to the LQG optimal-control problem is presented for a system with special controller structure and robust cost-weighting terms. The controller structure has the advantages of both single- and two-degrees-of-freedom designs. The effect of introducing a common robustness weighting term in the cost index is considered. It is shown that this leads to an additional gain term in the Youla parameterised form of the controller. To illustrate the advantages of the controller structure and the influence of the robustness weighting term, a flight control system design example is presented. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Integral variable structure control approach for robot manipulators

    Publication Year: 1992 , Page(s): 161 - 166
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (345 KB)  

    An integral variable structure control (IVSC) approach for robot manipulators is presented to achieve accurate servo-tracking in the presence of load variations, parameter variations and nonlinear dynamic interactions. A procedure is proposed for choosing the control function so that it guarantees the existence of the sliding mode and for determining the coefficients of the switching plane and the integral control gain such that the IVSC approach has the desired properties. Furthermore, a modified proper continuous function is introduced to overcome the chattering problem. The proposed IVSC approach has been simulated for the first three links of a PUMA 560 robot arm as an illustration. The simulation results demonstrate the potential of the proposed scheme. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Adaptive implementation of internal model principle for continuous time systems

    Publication Year: 1992 , Page(s): 167 - 171
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (317 KB)  

    The paper presents an adaptive implementation of internal model principle for continuous time systems. It is shown that without persistent excitation the adaptive control system with the internal model principle is globally stable in that the plant input and output remain bounded. It is also shown that the stability of the adaptive control system is still maintained in the presence of plant unmodelled dynamics and other bounded disturbances. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Design of algorithms for spatial-time reduction complexity of dynamic programming

    Publication Year: 1992 , Page(s): 172 - 180
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (564 KB)  

    The objective of the paper is the search for algorithms to reduce the spatial-time complexity of dynamic programming. These algorithms have been verified in second-order continuous systems, with indexes of performance where the time explicitly appears. The use of such algorithms is vital when dealing with third-order systems and second-order stochastic systems. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Multirate adaptive inferential estimation

    Publication Year: 1992 , Page(s): 181 - 189
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (570 KB)  

    An adaptive inferential algorithm is developed for estimation and control of multirate systems. The output y is measured J times slower than the secondary process output v and the input u, but an output estimate ye is produced at each sampling interval of v and u. Compared with previous work on multirate inferential systems, the proposed algorithm has a more formal theoretical basis. For example, the output y is related to the secondary output v not only through external stochastic disturbances but also through the internal system structure. Convergence properties are formally proven for the case of zero external stochastic disturbances, and a simplified algorithm is proposed for practical applications. Simulated results illustrate the convergence properties of the algorithm and the improvement obtained in simple feedback control systems. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.