Xavier Litrico

Cyber Security of Water SCADA Systems—Part I: Analysis and Experimentation of Stealthy Deception Attacks

This brief aims to perform security threat assessment of networked control systems with regulatory and supervisory control layers. We analyze the performance of a proportional-integral controller (regulatory layer) and a model-based diagnostic scheme (supervisory layer) under a class of deception attacks. We adopt a conservative approach by assuming that the attacker has knowledge of: 1) the system dynamics; 2) the parameters of the diagnostic scheme; and 3) the sensor-control signals. The deception attack presented here can enable remote water pilfering from automated canal systems. We also report a field-operational test attack on the Gignac canal system located in Southern France.

Stealthy deception attacks on water SCADA systems

This article investigates the vulnerabilities of Supervisory Control and Data Acquisition (SCADA) systems which monitor and control the modern day irrigation canal systems. This type of monitoring and control infrastructure is also common for many other water distribution systems. We present a linearized shallow water partial differential equation (PDE) system that can model water flow in a network of canal pools which are equipped with lateral offtakes for water withdrawal and are connected by automated gates. The knowledge of the system dynamics enables us to develop a deception attack scheme based on switching the PDE parameters and proportional (P) boundary control actions, to withdraw water from the pools through offtakes. We briefly discuss the limits on detectability of such attacks. We use a known formulation based on low frequency approximation of the PDE model and an associated proportional integral (PI) controller, to create a stealthy deception scheme capable of compromising the performance of the closed-loop system. We test the proposed attack scheme in simulation, using a shallow water solver; and show that the attack is indeed realizable in practice by implementing it on a physical canal in Southern France: the Gignac canal. A successful field experiment shows that the attack scheme enables us to steal water stealthily from the canal until the end of the attack.

H/sub /spl infin// control of an irrigation canal pool with a mixed control politics

This paper presents a method to design efficient automatic controllers for an irrigation canal pool, that realize a compromise between the water resource management and the performance in terms of rejecting unmeasured perturbations. This mixed controller design is casted into the H/sub /spl infin// optimization framework, and experimentally tested on a real canal located in Portugal. The experimental results show the effectiveness of the method. We also interpret classical control politics for an irrigation canal (local upstream and distant downstream control) using automatic control tools, and show that our method enables to combine both classical politics, keeping the distant downstream control water management while recovering the local upstream control real-time performance with respect to the user.

Cyber Security of Water SCADA Systems—Part II: Attack Detection Using Enhanced Hydrodynamic Models

This paper investigates the problem of detection and isolation of attacks on a water distribution network comprised of cascaded canal pools. The proposed approach employs a bank of delay-differential observer systems. The observers are based on an analytically approximate model of canal hydrodynamics. Each observer is insensitive to one fault/attack mode and sensitive to other modes. The design of the observers is achieved by using a delay-dependent linear matrix inequality method. The performance of our model-based diagnostic scheme is tested on a class of adversarial scenarios based on a generalized fault/attack model. This model represents both classical sensor-actuator faults and communication network-induced deception attacks. Our particular focus is on stealthy deception attacks in which the attackers goal is to pilfer water through canal offtakes. Our analysis reveals the benefits of accurate hydrodynamic models in detecting physical faults and cyber attacks to automated canal systems. We also comment on the criticality of sensor measurements for the purpose of detection. Finally, we discuss the knowledge and effort required for a successful deception attack.

Robust IMC flow control of SIMO dam-river open-channel systems

The paper deals with the automatic control of a dam river system, where the action variable is the upstream discharge and the controlled variable the downstream discharge. The system is a cascade of single input-single output (SISO) systems, and can be considered as a single input-multiple output (SIMO) system, since there are multiple outputs given by intermediate measurement points distributed along the river. A generic robust design synthesis based on internal model controller (IMC) design is developed for internal model based controllers. The robustness is estimated with the use of a bound on multiplicative uncertainty taking into account the model errors, due to the nonlinear dynamics of the system. Simulations are carried out on a nonlinear model of the river.

Boundary control of hyperbolic conservation laws using a frequency domain approach

The paper uses a frequency domain method for boundary control of hyperbolic conservation laws. We show that the transfer function of the hyperbolic system belongs to the Callier-Desoer algebra, for which the Nyquist theorem provides necessary and sufficient conditions for input-output closed-loop stability. We examine the link between input-output stability and exponential stability of the state. Specific results are then derived for the case of proportional boundary controllers. The results are illustrated in the case of boundary control of open-channel flow

Brief paper: Boundary control of linearized Saint-Venant equations oscillating modes

The Saint-Venant equations describe the dynamics of one dimensional open-channel flow. The paper investigates linearized Saint-Venant equations modes and their control. We show that it is possible to suppress the oscillating modes over all the canal pool by a well-designed boundary dynamic controller using only the water level measurement at the downstream end of the pool. This controller is infinite dimensional, and also not strictly proper, which makes it difficult to implement on a real canal. However, a static control of the oscillating modes can be performed with a well-designed hydraulic structure. We therefore study the specific case of a constant proportional controller on the oscillating modes and show that they can be asymptotically attenuated by using a controller that depends only on local flow characteristics. Experimental results on a laboratory canal pool show the effectiveness of the proposed control.

Feed-Forward Control of Open Channel Flow Using Differential Flatness

This brief derives a method for open-loop control of open channel flow, based on the Hayami model, a parabolic partial differential equation resulting from a simplification of the Saint-Venant equations. The open-loop control is represented as infinite series using differential flatness, for which convergence is assessed. A comparison is made with a similar problem available in the literature for thermal systems. Numerical simulations show the effectiveness of the approach by applying the open-loop controller to irrigation canals modeled by the full Saint-Venant equations.

Unknown Input Observers Design for Time-Delay Systems Application to An Open-Channel

This paper deals with the problem of full-order observers design for linear continuous delayed state and inputs systems with unknown input (UI) and time-varying delays. A method to design an Unknown Input Observer (UIO) for such systems is proposed based on a delay-dependent stability conditions of the state estimation error system. A Fault Detection and Isolation (FDI) scheme using a bank of such UIO, is also presented and tested on a (FDI) problem related to irrigation canals.

Infinite dimensional modelling of open-channel hydraulic systems for control purposes

This paper provides a new computational method to obtain a frequency domain model of Saint-Venant equations, linearized around any stationary regime, including backwater curves. The obtained model is analyzed by characterizing the maximum achievable performance using inner-outer factorization, and a method to compute the poles of the system is indicated. The paper also provides a way to obtain an accurate rational approximation of the system.