arXiv subjects

Rong Su

Publications and source records attributed to Rong Su.

63 records · Page 4Linked to original sources

arXiv2019

Synthesis of Successful Actuator Attackers on Supervisors

In this work, we propose and develop a new discrete-event based actuator attack model on the closed-loop system formed by the plant and the supervisor. We assume the actuator attacker partially observes the execution of the closed-loop system and eavesdrops the control commands issued by the supervisor. The attacker can modify each control command on a specified subset of attackable events. The attack principle of the actuator attacker is to remain covert until it can establish a successful attack and lead the attacked closed-loop system into generating certain damaging strings. We present a characterization for the existence of a successful attacker, via a new notion of attackability, and prove the existence of the supremal successful actuator attacker, when both the supervisor and the attacker are normal (that is, unobservable events to the supervisor cannot be disabled by the supervisor and unobservable events to the attacker cannot be attacked by the attacker). Finally, we present an algorithm to synthesize the supremal successful attackers that are represented by Moore automata.

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arXiv2019

Supervisor Obfuscation Against Actuator Enablement Attack

In this paper, we propose and address the problem of supervisor obfuscation against actuator enablement attack, in a common setting where the actuator attacker can eavesdrop the control commands issued by the supervisor. We propose a method to obfuscate an (insecure) supervisor to make it resilient against actuator enablement attack in such a way that the behavior of the original closed-loop system is preserved. An additional feature of the obfuscated supervisor, if it exists, is that it has exactly the minimum number of states among the set of all the resilient and behavior-preserving supervisors. Our approach involves a simple combination of two basic ideas: 1) a formulation of the problem of computing behavior-preserving supervisors as the problem of computing separating finite state automata under controllability and observability constraints, which can be efficiently tackled by using modern SAT solvers, and 2) the use of a recently proposed technique for the verification of attackability in our setting, with a normality assumption imposed on both the actuator attackers and supervisors.

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arXiv2018

Automatic Generation of Optimal Reductions of Distributions

A reduction of a source distribution is a collection of smaller sized distributions that are collectively equivalent to the source distribution with respect to the property of decomposability. That is, an arbitrary language is decomposable with respect to the source distribution if and only if it is decomposable with respect to each smaller sized distribution (in the reduction). The notion of reduction of distributions has previously been proposed to improve the complexity of decomposability verification. In this work, we address the problem of generating (optimal) reductions of distributions automatically. A (partial) solution to this problem is provided, which consists of 1) an incremental algorithm for the production of candidate reductions and 2) a reduction validation procedure. In the incremental production stage, backtracking is applied whenever a candidate reduction that cannot be validated is produced. A strengthened substitution-based proof technique is used for reduction validation, while a fixed template of candidate counter examples is used for reduction refutation; put together, they constitute our (partial) solution to the reduction verification problem. In addition, we show that a recursive approach for the generation of (small) reductions is easily supported.

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arXiv2017

A pedestrian hopping model and traffic light scheduling for pedestrian-vehicle mixed-flow networks

This paper presents a pedestrian hopping model and a traffic signal scheduling strategy with consideration of both pedestrians and vehicles in the urban traffic system. Firstly, a novel mathematical model consisting of several logic constraints is proposed to describe the pedestrian flow in the urban traffic network and its dynamics are captured by the hopping rule, which depicts the changing capacity of each time interval from one waiting zone to another. Based on the hopping mechanism, the pedestrian traffic light scheduling problems are formulated by two different performance standards: pedestrian delay and pedestrian unhappiness. Then the mathematical technique and the meta-heuristic approach are both adopted to solve the scheduling problem: Mixed integer linear programming (MILP) formulation for pedestrian delay model and discrete harmony search algorithm (DHS) for both pedestrian delay model and unhappiness model. Secondly, a mathematical model about the vehicle traffic network, which captures drivers psychological responses to the traffic light signals, is introduced. Thirdly, a traffic light scheduling strategy to minimize the trade-off of the delays between pedestrians and vehicles is proposed. Finally, we translate this traffic signal scheduling problem for both pedestrians and vehicles into a MILP problem which can be solved by several existing tools, e.g., GUROBI. Numerical simulation results are provided to illustrate the effectiveness of our real-time traffic light scheduling for pedestrian movement and the potential impact to the vehicle traffic flows by the pedestrian movement.

math.OC↗

arXiv2017

Modelling and Traffic Signal Control of Heterogeneous Traffic Systems

An urban traffic system is a heterogeneous system, which consists of different types of intersections and dynamics. In this paper, we focus on one type of heterogeneous traffic network, which consists of signalized junctions and non-signalized ones, where in the latter case vehicles usually follow the first-in-first-out principle. We propose a novel model describing the dynamic behaviors of such a system and validate it via simulations in VISSIM. Upon such a new model, a signal control problem for a heterogeneous traffic network is formulated as a mixed integer programming problem, which is solved by a Lagrangian multiplier based hierarchical distributed approach. Comparisons between a homogeneous traffic system and a heterogeneous one are provided, which leaves the door open for developing a systematic planning approach on deciding what traffic junctions require signal control to ensure a good traffic control performance, thus, have a great social and economic potentials, considering that it is rather expensive to have signal control in an urban area.

math.OC↗

arXiv2016

A weighted pair graph representation for reconstructibility of Boolean control networks

A new concept of weighted pair graphs (WPGs) is proposed to represent a new reconstructibility definition for Boolean control networks (BCNs), which is a generalization of the reconstructibility definition given in [Fornasini & Valcher, TAC2013, Def. 4]. Based on the WPG representation, an effective algorithm for determining the new reconstructibility notion for BCNs is designed with the help of the theories of finite automata and formal languages. We prove that a BCN is not reconstructible iff its WPG has a complete subgraph. Besides, we prove that a BCN is reconstructible in the sense of [Fornasini & Valcher, TAC2013, Def. 4] iff its WPG has no cycles, which is simpler to be checked than the condition in [Fornasini & Valcher, TAC2013, Thm. 4].

math.OC↗

arXiv2016

Supervisor Synthesis to Thwart Cyber Attack with Bounded Sensor Reading Alterations

One of the major challenges about cyber physical systems is how to prevent cyber attacks to ensure system integrity. There has been a large number of different types of attacks discussed in the modern control and computer science communities. In this paper we aim to investigate one special type of attacks in the discrete-event system framework, where an attacker can arbitrarily alter sensor readings after intercepting them from a target system in order to trick a given supervisor to issue control commands improperly, driving the system to an undesirable state. We first consider the cyber attack problem from an attacker point of view, and formulate an attack with bounded sensor reading alterations (ABSRA) problem. We then show that the supremal (or least restrictive) ABSRA exists and can be synthesized, as long as the plant model and the supervisor model are regular, i.e., representable by finite-state automata. Upon the synthesis of the supremal ABSRA, we present a synthesis algorithm, which ensures that a computed supervisor will be ABSRA-robust , i.e., either an ABSRA will be detectable or will not lead the system to an undesirable state.

cs.FL↗

arXiv2016

What Information Really Matters in Supervisor Reduction?

To make a supervisor comprehensible to a layman has been a long-lasting goal in the supervisory control community. One strategy is to reduce the size of a supervisor to generate a control equivalent version, whose size is hopefully much smaller than the original one so that a user or control designer can easily check whether a designed controller fulfils its objectives and requirements. After the first journal paper on this topic appeared in 1986 by Vaz and Wonham, which relied on the concept of control covers, in 2004 Su and Wonham proposed to use control congruences to ensure computational viability. This work is later adopted in the supervisor localization theory, which aims for a control equivalent distributed implementation of a given centralized supervisor. But after so many publications, some fundamental questions, which should have been addressed in the first place, have not been answered yet, namely what information is critical to ensure control equivalence, what information is responsible for size reduction, and whether the partial observation really makes things different. In this paper we will address these fundamental questions by showing that there does exist a unified supervisor reduction theory, which is applicable to all feasible supervisors regardless of whether they are under full observation or partial observation. Our theory provides a partial order over all control equivalent feasible supervisors based on their enabling, disabling and marking information, which can be used to categorize the corresponding reduction rates. Based on this result we can see that, given two control equivalent feasible supervisors, the one under full observation can always result in a reduced supervisor no bigger than that induced by a supervisor under partial observation.

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arXiv2016

Timed Supervisory Control for Operational Planning and Scheduling under Multiple Job Deadlines

In this paper, we model an operational planning and scheduling problem under multiple job deadlines in a time-weighted automaton framework. We first present a method to determine whether all given job specifications and deadlines can be met by computing a supremal controllable job satisfaction sublanguage. When this supremal sublanguage is not empty, we compute one of its controllable sublanguages that ensures the minimum total job earliness by adding proper delays. When this supremal sublanguage is empty, we will determine the minimal sets of job deadlines that need to be relaxed.

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