Showing papers in "Transactions of the Institute of Measurement and Control in 1999"

Plant modelling for human supervisory control

Abstract: This paper provides an overview of multilevel flow modelling (MFM) and its application for design of displays for the supervisory control of industrial plant. The problem of designing the inforrrza...

Laboratory studies of trust between humans and machines in automated systems

Abstract: In supervisory control, operators are expected to monitor automation and to intervene if there is an opportunity to improve system productivity or if faults develop which cannot be managed by the a...

Active fault-tolerant flight control systems design using the linear matrix inequality method

Abstract: This paper discusses the issues of robust control law design for fault-tolerant systems. Based on the assumption that the effects of faults can be expressed in linear-fractional-transformation (LFT...

Open versus minimally invasive surgery: a man-machine system approach:

Abstract: Minimally invasive surgery is one of the important developments in surgery. In this type of surgery, the actual operation is performed through a number of small incisions in the skin. Special instruments are inserted via trocars, i.e. tubes that allow the surgeon to bring instruments or sensors into the body. The view at the operating field comes from a camera presenting a two-dimensional image on a monitor. The minimally invasive surgical technique has many potential benefits for the patients. However, compared to open surgery there are severe disadvantages for the surgeon, such as the loss of three-dimensional visual feedback, the disturbed eye-hand co-ordination and the poor ergonomic design of the surgical instrumentation. At this moment the differences between open and minimally invasive surgery can mainly be ascribed to differences in the manual control task. In this paper, the man-machine aspects of the traditional open operation process will be compared with those of the minimally invasive surgery...

Modelling the controller of a process

Abstract: Models of humans (operators, controllers) in human-machine systems have tacitly assumed that humans must have a model of the process in order to control it. Humans have therefore traditionally been described as information processing systems with an internal or mental model of the process as an important component. A more systemic or cybernetic view acknowledges that the human must be a model of the process in order to control it. This suggests a different approach to modelling, which is functional rather than structural, and where the emphasis is on how the joint human-machine system can maintain control of a situation. A specific model, called the Contextual Control Model (COCOM), which is based on the principles of cognitive systems engineering, illustrates the approach, COCOM provides a foundation for analysing controller performance as well as implementing controller needs.

Multimedia and process control interfaces: signals or noise?:

Abstract: Multimedia interfaces are examined and the nature of current input and output media identified. A number of design objectives for multimedia inteifaces are suggested - improving efficiency, learning and providing a stimulating problem-solving environment. The key problem of how to choose an appropriate medium for a particular interface situation is analysed and the concept of a signal-to-noise ratio for measuring media expressiveness is tentatively postulated. Some recent work in process control is then examined and the results interpreted from the signal-to-noise ratio viewpoint. These are then related to the concept of media expressiveness.

The design of a real-time engineering flight simulator for the rapid prototyping of avionics systems and flight control systems

Abstract: This paper describes the design of a real-time flight simulator, which is based on a modular architecture of PCs coupled by Ethernet. The simulator is required to provide a rapid prototyping environment to support the design and evaluation of avionics systems and flight control systems. Methods are described to ensure real-time implementation of the equations of motions using a standard PC and the provision of real-time graphics to simulate aircraft displays using SVGA. The paper includes analysis of the performance of the flight modelling methods and the simulation of aircraft displays. The paper concludes that high fidelity flight models and aircraft displays can be implemented using standard PC platforms and Ethernet cards, if attention is given to the design of the simulator architecture. The resultant simulator provides a rapid prototyping environment, standardising on the packet format and low-level packet protocols of Ethernet,

Human-machine systems:

Abstract: A brief overview of theoretical, experimental and industrial issues that are typical for studies on human-machine systems is given. The paper distinguishes three human-machine interaction modes: direct control, intermittent control and supervisory control. It is shown that a technology-driven engineering approach drives human-machine interaction out of the loop. It is challenging to use developments, such as multimedia, for all control modes, to enhance rather than abolish human-machine interaction. Design of any of the control modes requires a human-centred design approach. This overview refers to other papers in a series dedicated to human-machine systems.

Multivariable control analysis of a hydraulic turbine

Abstract: Dinorwig is a pumped storage hydroelectric power generation station which is used for frequency regulation on the national grid. Its control system consists of separate PID governors for each of the six 300 MW turbine-generators. Accuracy and speed of response in counteracting supply frequency disturbances is improved by increasing the PID gains but recent experience has shown that this can sometimes lead to oscillatory behaviour. At Dinorwig, water is supplied to the turbines by means of a common tunnel from the upper lake which is then split by a manifold into six separate penstocks for individual machines. This paper uses a linearised multivariable model of two machines, coupled through a non-elastic water column, to show that this reduces the system's stability margin and that PID parameters tuned for optimum single machine operation are not suitable when two (or more) machines are in use. The Direct Nyquist Array method is then used to design a control system, consisting of a decoupling compensator a...

Using limit cycle data for parameter estimation

Abstract: Exact expressions for the periods and amplitudes of limit cycles in relay controlled loops, with first order plus dead time (FOPDT) and second order plus dead time (SOPDT) transfer functions have been obtained using the A-locus method. The method has also been extended to unstable FOPDT and SOPDT transfer functions since it is possible to have unstable transfer function models for some chemical processes. For these processes, it is shown that analysis using the DF method can give large errors. Several examples have been given to illustrate application of the method and it has been shown that the method will work well for small measurement errors when compared with the DF method.

The laser in manufacture - its use in the soldering of electronic assemblies:

Abstract: As a means of applying heat energy for soldering, lasers can offer a realistic solution to certain problem areas in electronics assembly. There are, however, limitations as well as advantages to the technique and an understanding of both is essential for its successful application. The Laser Soldering Group at Hull has been investigating the use of lasers for soldering purposes and in this paper we are concerned with the application of semiconductor diode lasers to the soldering of electronic assemblies. Using specific industrial applications as examples this paper highlights the difficulties as well as the benefits in the use of lasers for soldering.

Human supervisory control of aircraft, rail and highway vehicles

Abstract: This paper reviews recent trends in control of aircraft, rail and highway vehicles toward supervisory control. Supervisory control means the human operator intermittently specifies goals, constraints and procedural information to a computer, monitors synoptic displays of state information, and tasks the computer to execute the instructions automatically. This trend has been driven by new sensor, communication and computer technology. Full automation of these transport systems is currently unacceptable, not only for reasons of safety, but also because radical departure from present systems is technologically and economically infeasible, in addition to which the public does not like radical change. Commercial and military aircraft are easily the most advanced of the three transportation modes. Rail and highway systems are currently undergoing rapid transformation, nevertheless impeded by economic and other societal constraints. Examples of new technological developments are given for each mode. Common probl...

Stabilization of longitudinal motion of a hypersonic transport aircraft

Abstract: Hypersonic transport (HST) aircraft are the subject of much current research as the need to reduce block times on long haul flights becomes more pressing. The dynamics of such HST aircraft are strongly influenced by the close interdependence of the aerodynamic and propulsion systems. The key dynamic features of such aircraft are their dynamically unstable longitudinal motion, and extremely sluggish response in pitch attitude, which make aircraft of this type difficult to fly. This paper presents the design of an automatic flight control system which can provide the required degree of stability and the required flying qualities. The optimal feedback control law was derived from the use of linear quadratic regulator (LQR) theory, in which the state weighting matrix was calculated from known closed-loop eigenvalues which were specified by the designer to obtain the required stability and flying qualities. The effectiveness of the multivariable control law is illustrated by means of dynamic responses obtained...

On the design of command and stability augmentation systems for advanced technology aeroplanes

Abstract: There exists an enormous wealth of published material describing the application of so called, 'modern control methods' to the design of fliglat control systems for piloted aeroplanes. It is also evident, with the exception of a very small number of recent applications, that there is a conspicuous lack of enthusiasm on the part of the airframe manufacturers to adopt this design technology, especially for the design of command and stability augmentation systems for piloted aeroplanes. It is possible to speculate on the reasons for this apparent lack of interest, but to do so might well result in a misplaced condemnation of modern control methods. Since evidence exists to suggest that some modern control system design strategies have overlooked important flight dynamics considerations, the discussion is turned around here by drawing attention to some of the more important considerations in command and stability augmentation system design. The object is, therefore, to inform the designer, of whatever persuas...

LQG Feedforward/feedback stochastic optimal control and marine application

Abstract: The solution of a 31/2 degree-of-freedom H, stochastic optimal control problem is discussed. The system is assumed to be scalar and includes a 21/2 degree-of-freedom tracking controller, together with a feedforward control action. The optimisation is based upon an extended cost-function which allows separate costing of the terms due to the feedback, reference and feedforward controllers. This enables the amount of feedforward action to be varied relative to the feedback action and the robustness of the feedback-loop to be shaped independently of the tracking performance. The use of a separate cost term to be able to vary the amount of feedforward action and the resulting design steps are novel and important in applications. Previous solutions did not allow separate cost tuning of the feedforward control terms, A ship positioning design study, that utilises feedforward action, is presented to illustrate the benefits of the approach.

The application of actuator performance limits to aeroservoelastic compensation

Abstract: An interaction between an aircraft's structural dynamics, unsteady aerodynamics and flight control system can have serious effects on the aircraft both in terms of structural integrity and rigid body stability. The effects of such an interaction, known as aeroservoelasticity, are poorly understood and as a result, very conservative flight control system design methods are used in order to achieve flight clearance. This paper demonstrates how the use of nonlinear actuation system models predicts a maximum boundary for the amplitude of the structural response as a result of the performance limits of the nonlinear actuation system. This envelope of maximum structural response can then be used to allow relaxation of the current design criteria for the structural mode filters. The procedure is demonstrated using a representative aircraft system model. Finally, the results of single input frequency response tests of a representative actuation system are presented in support of the earlier results.

Design of a controller for a highly coupled V/STOL aircraft

Abstract: This paper describes the design of a controller for a vertical/shart take-off and landing (V/STOL) aircraft using the Robust Inverse Dynamic Estimation (RIDE) control theory to improve aircraft performance and reduce pilot workload throughout the transition phase from jet to wing-borne flight and vice versa. The controller is required to be effective throughout the speed envelope from hover to 200 knots, during which the aircrafi undergoes significant changes in its dynamics characteristics. The design of the controller is based on a mathematical model of the aircraft linearised at 120 knots, is developed using realistic actuator and sensor models and is extended across the speed range, resulting in the transition envelope controller which is capable of providing acceptable pilot workloads and handling qualities throughout the transition phase. Controller design issues such as the choice of feedback variables, the selection of pilot inceptor configurations and functionalities, and the use of integrator anti-windup techniques in the presence of actuator saturation are discussed. Pilot-in-the-loop simulation studies show that the controller provides good control and handling qualities throughout the transition phase.

Evaluating deterministic errors in low - bandwidth digital filters using Taylor series expansions

Abstract: A method is presented to show how deterministic errors in low-bandwidth digital filters may be expressed in terms of the input signal and its derivatives. By applying a Taylor series expansion to the delayed terms of the difference equation implemented by the digital filter, the difference equation may be written as a differential equation which allows easy computation of the deterministic errors, The paper also demonstrates the importance of performing error analysis as part of the digital filter design process.

Fault diagnosis and fault-tolerant estimation of a rail traction system via fuzzy observers:

Abstract: This paper studies the fault diagnosis and fault-tolerant estimation problems of a rail traction system. The main idea is to use a bank of fuzzy observers to detect faults and to isolate failed sensors. Once the failed sensor is isolated, the fuzzy observer driven by healthy sensors provides reliable torque and flux estimates which are used for the control purpose. The concept and design procedures for fuzzy observers are presented in this paper. A fuzzy observer is able to produce accurate state estimations and generate robust residuals for non-linear dynamic systems such as a rail traction system. The fault diagnosis and fault-tolerant estimation scheme proposed for the rail traction system is demonstrated using simulations.

Management of a robotised system on an Ethernet network

Abstract: One of the most important problems for industrial implantation of Flexible Manufacturing Systems is communication between different devices and computers. The standardised use of local area networks (LANs), together with the power of available computers has significantly reduced communications difficulties. The next key challenge to be addressed is that of enhanced robot programming to implement integrated manufacturing processes. A proposal to operate a robotised system through an Ethernet network is presented in this paper. The system uses LAN features and socket programming to (i) implement a computer-robot link to allow an off-line robot programming, (ii) share the robotised system from a computer server and (iii) monitor all tasks, and corresponding status of the system from any node in the LAN.