Jaume Figueras

CORAL off-line: an object-oriented tool for optimal control of sewer networks

This paper describes a tool to aid in the analysis and design of combined sewer networks. Complex drainage systems include actuators, like flow-diversion gates and detention tanks, which should be optimally controlled in order to minimize flooding and combined sewer overflow (CSO). Through these optimisations volume to waste water treatment plants (WWTP) is maximised. CORAL is a tool able to model a combined sewer network, simulate rain events, calculate actuators optimal policies, reproduce past rain events and calculate different balances for all model elements.

Fault Detection and Isolation of Rain Gauges and Limnimeters of Barcelona's Sewer System Using Interval Models

Abstract In this paper, fault detection and isolation of rain gauges and limnimeters (water level sensors in the sewers) of Barcelonas urban sewer system is presented. The Barcelona urban drainage network has a telemetry network containing 22 rain gauges and more than 100 limnimeters used for the control system. In order to detect and isolate faulty instruments and to reconstruct faulty measurements from data fusion, a fault diagnosis system is necessary. The proposed fault diagnosis strategy is based on building an interval linear model for every instrument (Puig, 2002). Then, while the real measure is inside the interval of predicted behaviour (or envelope) generated using its interval model no fault can be indicated. However, when the measure is outside its envelope a fault can be indicated. Fault isolation is based on the matching of the real fault signature with the theoretical fault signature using structured residuals (Gertler, 1998).

FIRST RESULTS OF PREDICTIVE CONTROL APPLICATION ON WATER SUPPLY AND DISTRIBUTION IN SANTIAGO-CHILE

Abstract This paper deals with the use of predictive optimal control techniques for flow management in a large water system including reservoirs, open channels for water transport, water treatment plants, pressurized water pipe networks, flow/pressure control elements and a telemetry/telecontrol system. Predictive control is used to generate flow control strategies from the sources to the consumer areas to meet future demands with appropriate pressure levels, optimizing operational goals such as network safety volumes and flow control stability.

Fault-tolerant optimal control of sewer networks: Barcelona case study

Under the city of Barcelona, which has a population of three million in an area of 98 km2, there is a complex sewage system with almost 1500 km in length. That system is characterised as being unitary, that is, its collectors carry rain water and residual water. The yearly rainfall is not very high (600 mm/year), but it includes heavy storms typical of the Mediterranean climate that cause a lot of flooding problems and Combined Sewer Overflows (CSO) to the receiving waters. A control system capable of minimising flooding and the amount of water going into the sea (pollution) is desirable, especially during important meteorological phenomena4. The corresponding actions of control have to be applied over the active components of the sewer system (retain tanks, derivation gates, pump stations). Currently, the Barcelona sewer network has a global control under development. The actuator set points are determined in function of the state of the entire system, that is, the information received from more than one hundred sensors (rain gauges and level sensors). Furthermore, the control strategy is obtained by minimising flooding and pollution, optimising other performance aspects (i.e. levels in real tanks) and including fault tolerance in sensors and/or actuators without severe losses in the system performance. The application of global control on the system requires the use of an operative model of the system dynamics and the network constrains to calculate, in a future horizon, optimal strategies to handle actuators taking into account the actual system state information (given by sensors connected to a SCADA) and an adequate rain prediction4. One of the aims of this paper is to develop an application of Optimal Control technique over a part of Barcelona sewer network, which has a total surface of 22.6 km2. An important goal of this global control application is that it works effectively under very strong meteorological conditions. But it is possible that faults could appear in any of the sensors and/or malfunction of any of the derivation gates, retention gates or pump stations if these conditions are presented. Because of that, the sewer network optimal control should be fault tolerant14. Fault-Tolerant Control (FTC) is a relatively new concept which aims at improving control performance by treating faults and exemptions in the operation of technical processes in a systematic way2. The robustness of feedback control systems gives rise to an implicit fault tolerance. Faults that occur under closed-loop control are often compensated by the control action. The same applies when optimal control techniques are used. It has been furthermore demonstrated that even when knowledge of the fault is not available, when the estimation of external disturbances affecting the loop is performed in a special way and the input levels have hard constraints, the optimizationbased controller automatically takes advantage of actuator redundancy when available10.

MULTIPLE FAULT DIAGNOSIS SYSTEM DESIGN USING RELIABILITY ANALYSIS: APPLICATION TO BARCELONA RAIN-GAUGE NETWORK

Abstract This paper discusses the problem of designing a fault diagnosis system to be able to deal with multiple sequential fault occurrence using reliability analysis techniques. In complex systems with thousands of components this type of fault is very common since the continuous operation of the systems/processes is required. Then, a fault diagnosis algorithm should cope with multiple sequential faults, but degradation in its fault isolation capabilities is introduced until the point that they should be stopped because of the loss of isolability. Finally, an example based on the rain-gauge sensor network of the Barcelona sewer system will be used to illustrate how a proposed fault diagnosis system design algorithm behaves under multiple sequential fault occurrences.

FAULT DIAGNOSIS UNDER MULTIPLE SEQUENTIAL FAULTS OF THE RAIN-GAUGE NETWORK USED TO CONTROL THE BARCELONA SEWER SYSTEM

Abstract This paper discusses the problem of fault diagnosis under multiple sequential faults occurrence. In industrial applications this type of fault is the most common since the continuous operation of systems/processes is required. The fault diagnosis algorithms should cope with such type of multiple faults, but degradation in their fault isolation capabilities is introduced until the point that they should be stopped. A new algorithm to design the fault diagnosis system to be able to tolerate multiple sequential sensor faults is proposed. Finally, an example based on the rain-gauge sensor network of the Barcelona sewer system will be used to illustrate how the associated fault diagnosis system behaves under multiple sequential faults occurrence and to test the proposed algorithm.

Simulation analysis of a dynamic ridesharing model

A dynamic ridesharing service is a system that enables drivers and riders to arrange one-time shared rides, with sufficient convenience and flexibility to be used on a daily basis. The quality of a dynamic ridesharing service is critical for commuters who need to reach their end destination on time every day. To ensure satisfactory quality, the waiting times in a ridesharing service must be low. This paper describes a dynamic ridesharing model proposal for commuters living in a small community in the Barcelona metropolitan area. The proposal solves transport problems between the community and a communication hub served by trains and buses. A survey was sent to community residents to find out whether they would be interested in the idea and willing to participate in a pilot test. A simulation model was built to determine to most suitable type of dynamic ridesharing model given the limited numbers of responses received and the heterogeneous mobility patterns of drivers and riders in the community. Reasonable good results are obtained for the morning commute but improvements are needed for the return commute in the afternoon. Further work will be required to increase the number of drivers interested in the ridesharing service.

Formalizing geographical models using specification and description language: the wildfire example

In this paper we explore how we can use Specification and Description Language, to represent simulation models that make an intensive use of geographical information, like environmental simulation models. The purpose is to perform a complete unambiguous, graphical and formal representation of a wildfire simulation model. Specification and Description Language is a modern object oriented language that allows the definition of distributed systems. It has focused on the modeling of reactive, state/event driven systems, and has been standardized by the International Telecommunications Union (ITU) in the Z.100. Thanks to the graphical representation of the simulation model, the interaction between the experts that usually come from different areas is simplified. Also, due to the unambiguous and modular nature of the language, all the details of the model can be validated by personnel that do not necessarily are used with programming languages or simulation infrastructures.

Design of Structured Residuals Using Interval Models: Application to Multiple Sequential Fault Isolation in Sensor Networks

: In this paper,the design of a structured residual set to deal with multiple sequential fault isolation is proposed in case that the underlying model describing the system to be monitored is an “interval model”. In industrial applications, this type of fault is the mostcommon since the continuous operation of systems/processes is required. An example based on the rain-gauge sensor network of the Barcelona sewer system will be used to illustratethe effectiveness of the proposed approach.

DESIGN OF STRUCTURED RESIDUALS USING INTERVAL MODELS: APPLICATION TO MULTIPLE SEQUENTIAL FAULT ISOLATION IN SENSOR NETWORKS

Abstract In this paper, the design of a structured residual set to deal with multiple sequential fault isolation is proposed in case that the underlying model describing the system to be monitored is an “ interval model” . In industrial applications, this type of fault is the most common since the continuous operation of systems/processes is required. An example based on the rain-gauge sensor network of the Barcelona sewer system will be used to illustrate the effectiveness of the proposed approach.