Takashi Hamaguchi

Safety securing approach against cyber-attacks for process control system

Abstract After the appearance of Stuxnet, the safety assurance against cyber-attacks has been a serious problem for process control. For safety assurance, not only information system securing approaches but also process control original measures are necessary. In this paper, a new protection approach is proposed. Application of an information system securing technique called “zones and conduits” to process control is discussed. By dividing the control system network into plural zones, higher possibility of detecting cyber-attacks and preventing operational accidents can be achieved. By defining detectability and reachability matrices, zone division for cyber-attack detection can be designed.

Design and Control of HIDiC

Energy conservation in ethanol refinement was discussed in this paper. Ethanol is a candidate of the bio-energy that is useful for a crude oil remarkable rise and for global warming restraint. A new structure of HIDiC (Heat Integrated Distillation Columns) with alternating trays of rectifying section and stripping section was proposed in this research. Because it is a tray column, the correspondence of trays, between which heat is exchanged, is fixed and precise evaluation of exchanged heat can be performed. In not only HIDiC but also normal distillation columns, the realizable product purities have limits. If the desired purities are closed to the limits, the control is very difficult. Because the proposed HIDiC has large heat exchange area, high separate capability can be achieved without reboiler or condenser. Its controllability is higher than HIDiC in which only wall is the heat exchange area. Its superiority was shown in control simulation against the feed concentration changes

A Method of Designing Plant Alarm Systems with Hierarchical Cause-Effect Model

Plant alarm systems are important because they enable safe and reliable operations at chemical plants. Takeda et al. proposed a method of designing alarm systems for plants based on a plant cause-effect (CE) model. We propose a method of designing alarm systems for plants with a hierarchical CE model to improve the selection of fault origins to distinguish them with the systems and a procedure for designing the systems.

Use of two-layer cause-effect model to select source of signal in plant alarm system

Alarm systems provide an interface between operators and the machinery in a chemical plant because they allow abnormalities or faults caused by operators to be detected at an early stage. Alarms should be used to enable operators to diagnose faults and plan countermeasures, and nuisance alarms should be eliminated. We propose the use of a selection algorithm of sets of pairs of alarm variables and their signs. The signs mean the upper or lower limits of the alarm variables. The selected sets of pairs are theoretically guaranteed to be able to qualitatively distinguish all assumed faults. We propose using a two-layer cause-effect model for the algorithm, which represents the cause and effect relationship between state variables based on the topology of a plant. This model is applied to a simple process. The simulation results illustrate the usefulness of our method.

Detection of Cyber-attacks with Zone Dividing and PCA☆

Abstract Recently cyber-attacks become serious threats even for control systems. For process control, not only security but also safety must be assured. For safety assurance, the effects of cyber-attacks such as concealed remote operation and maneuvering must be evaluated. We proposed a securing method to divide field networks into plural zones. Even when a zone is intruded and attacks are concealed, the effects appear in other zones. In this paper, an automatic cyber-attacks detection system using PCA (Principal Component Analysis) is proposed. There are many kinds of relationships among variables included plural zones. Cyber-attacks change some of them. PCA is effective to detect the changes.

Anti-saturation discrete-time nonlinear controllers and observers

Abstract In this paper, a nonlinear controller design method based on a nonlinear state space model is proposed. By adding differentiable saturation elements, this controller design scheme can deal with the saturation of the manipulated variables. Linear approximation is successively executed at each sampling time. The velocity-type controller and observer are designed based on the linear model. For the calculation of linear approximation, the information of the states at the previous sampling time must be known. A nonlinear observer using integration of nonlinear state equations is adopted for the state estimation. The observer gain of the linear observer is applied to the nonlinear observer. This control system can stabilize open-loop unstable processes and non-minimum phase systems. The performance is demonstrated by its successful application to control problems of a CSTR, which has two stable points and one unstable steady-state point.

Strategic security protection for industrial control systems

Even though serious accidents such as explosion or leakage of poisonous substances have not occurred yet, several cyber-attacks, e.g. Stuxnet, Havex and etc. have been developed to attack industrial control systems (ICS) and succeeded to hinder the operation of industries for long term. These mal wares utilized zero-day exploits and concealment. Although countermeasures against them have been developed, new kinds of cyber-attacks will be developed. It looks a vicious spiral. Especially for ICS, safety should be maintained even if the cyber-attacks utilize unknown vulnerability. In this paper, a systematic approach to design protection systems against cyber-attacks for ICS is proposed. Not only the vulnerabilities of the control network but also properties of the process safety are considered to design and evaluate them. The investment for cyber-security should be proposed according to the seriousness of possible hazards, required security level and budgets. The proposed approach enables the strategic decision making. Moreover, the scenarios of incident responses to care safety and security are discussed.

Abnormal situation correction based on controller reconfiguration

Abstract It is desirable to support operator activity in abnormal correction of chemical plants. Although fault diagnosis systems have very fertile grounds for theoretical and industrial development, multiple possibilities of faults are diagnosed. A countermeasure against one cause might be dangerous when used against another cause. A countermeasure might be effective to multiple causes. Countermeasure planning is necessary to complete fault diagnosis. An operator manipulates one variable while observing one variable in each countermeasure. It resembles the controller configuration of a single loop controller. An algorithm for controller reconfiguration is proposed for the first stage of countermeasure planning.

An Evaluation Method for Plant Alarm System Based on a Two-Layer Cause-Effect Model

Abstract Industrial plant alarm system forms the core element of almost all modern operator interfaces used to automatically monitor plant conditions and alert plant operators to any significant changes that require diagnosis and/or countermeasures. In this paper, we propose a method for quantitatively evaluating the diagnostic and timely characteristics of alarm system that uses a two-layer cause-effect model to measure three rates used as indices: effective, recall, and timeliness rates. The effective and recall rates are used to evaluate the diagnostic abilities of the alarm system in identifying root causes of assumed malfunctions. The timeliness rate is used to evaluate the plant alarm systems ability to generate diagnostic alarms quickly enough for operators to respond in a timely manner and correct the problem. The case study demonstrated the feasibility of the proposed method.

Study on safety operation support system by using the risk management information

In case of abnormal situation of chemical process plant, it is required to judge the plant condition correctly and carry out the unerring response. Many operation support systems were proposed to help the plant operator with such judgment and operation decision making, but most of them could not indicate the rationale for operation, because they used only information on the result of plant design. Therefore, plant operator could not get the theoretical information for operation decision making from it. This paper proposes the safety operation support system which helps the operation decision making based on the risk management information (RMI). The RMI is useful one for the theoretical operation decision making, because it is considered and updated through the plant life cycle (PLC) and includes the information on the design rationale (DR) of the safety countermeasure, the intents of corresponding operation, etc. PVC batch process is used for verifying the effectiveness of proposed method.