Brunel University

| Team | Planned Work | Objectives | Progress | Publications |
 

Team
 
    Department of Manufacturing and Engineering Systems,
    Brunel University,
    Uxbridge, UB8 3PH, UK.
 
 
 
 
 

Dr. Johannes Andersen
Research Fellow
Tel: (01895) 274 000 x 2920
Fax: (01895) 812556
Email: johannes.andersen@brunel.ac.uk

Dr. Atulya Nagar
Research Fellow
Tel: (01895) 274 000 x 2920
Fax: (01895) 812556
Email: Atulya.Nagar@brunel.ac.uk
 
 
 
 

Planned Work

High quality data is a prerequisite to the introduction of high levels of information processing for both strategic planning and operational management. In this regard, state and parameter estimation could play a crucial role. A state-estimator is an algorithm that computes the current state of a system from on-line measurements.When applied to water networks it can be viewed as an on-line monitoring system capable of tracking the time varying flows and pressures in real-time. However, the results of such an algorithm depend crucially on the quality of the data it uses. Uncertainty in many of the measurements and parameters, coupled with a high sensitivity between pressure and flow, will lead to inaccurate state estimates.

Some water networks will be amenable to state-estimation whilst others will not and so it is important to know which systems are in which category.

A direct spin-off from some methods of state estimation is on-line data validation and burst detection. It is proposed to couple state estimation with parameter estimation. Parameter estimation is a method of calibrating and adjusting model parameters such that the difference between actual and calculated measurements is minimised. Parameter estimation could, for instance, be used for estimating the size of a burst or the size of background leakage. Uncertainty information is crucial in parameter estimation, as the more uncertain parameters are the ones that will tuned.
 

Objectives
 

  1. Devise methods for robust automatic state and parameter estimation (S. A. P. E.) for eventual on-line, real-time monitoring of large-scale water distributionnetworks with few on-line meters.
  2. Devise an analytical approach that will supersede the ‘observability test’ by addressing the uncertainty associated with network parameters in general and demand values in particular. This will enable assessments to be made before a state-estimator is installed as to its potential for monitoring the system accurately.
  3. Devise diagnostic systems in order to distinguish between measurement errors, bursts and other topological anomalies.

Progress

In the space of less than on year, a very significant amount of progress has been made towards the first two objectives:

  1. An environment has been created under Windows NT for the validation of state-estimation algorithms for pseudo-online simulation. The environment supports the water network simulator, a telemetry simulator and operators’ interface.
  2. Data have been acquired from both Thames Water Utilities Ltd. and South West Water Services Ltd. A new network simulator has been devised and validated against the results of Epanet for several networks, including the Thames Water data. This new, loop-based, simulator has advantages over most other packages when dealing with so-called ‘controlling elements’, such as PRVs and NRVs [1].
  3. A new formulation has been designed for the solution of the hydraulic equations in the state-estimation problem. This is an extension of the simulator design. Instead of solving the state equations to find nodal pressures, the method determines nodal demands directly [2].
  4. An exhaustive, in-depth study into methods of modelling uncertainty has been carried out and trials are under way using Matlab to examine the different methods. The research has investigated ‘linear fractional transformations’ and ‘total robust least squares’.


Publications

[1] Andersen, J.H. Powell, R.S. 'Simulation of Water Networks containing Controlling Elements'. Journal of Water Resources Planning and Management, ASCE May/June 1999, vol 125, issue 3, pp 162-169.

[2] Andersen, J.H. Powell, R.S. 'A loop based Simulator and Implicit State-Estimator'. Submitted to: International Conference on Computing and Control for the Water Industry CCWI99 .

|  Main | Last update: 28/06/99 |  Steve Mounce |