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2020-07-16
Ni, Ming, Xue, Yusheng, Tong, Heqin, Li, Manli.  2018.  A cyber physical power system co-simulation platform. 2018 Workshop on Modeling and Simulation of Cyber-Physical Energy Systems (MSCPES). :1—5.

With the tighter integration of power system and Information and Communication Technology (ICT), power grid is becoming a typical cyber physical system (CPS). It is important to analyze the impact of the cyber event on power system, so that it is necessary to build a co-simulation system for studying the interaction between power system and ICT. In this paper, a cyber physical power system (CPPS) co-simulation platform is proposed, which includes the hardware-in-the-loop (HIL) simulation function. By using flexible interface, various simulation software for power system and ICT can be interconnected into the platform to build co-simulation tools for various simulation purposes. To demonstrate it as a proof, one simulation framework for real life cyber-attack on power system control is introduced. In this case, the real life denial-of-service attack on a router in automatic voltage control (AVC) is simulated to demonstrate impact of cyber-attack on power system.

Farivar, Faezeh, Haghighi, Mohammad Sayad, Barchinezhad, Soheila, Jolfaei, Alireza.  2019.  Detection and Compensation of Covert Service-Degrading Intrusions in Cyber Physical Systems through Intelligent Adaptive Control. 2019 IEEE International Conference on Industrial Technology (ICIT). :1143—1148.

Cyber-Physical Systems (CPS) are playing important roles in the critical infrastructure now. A prominent family of CPSs are networked control systems in which the control and feedback signals are carried over computer networks like the Internet. Communication over insecure networks make system vulnerable to cyber attacks. In this article, we design an intrusion detection and compensation framework based on system/plant identification to fight covert attacks. We collect error statistics of the output estimation during the learning phase of system operation and after that, monitor the system behavior to see if it significantly deviates from the expected outputs. A compensating controller is further designed to intervene and replace the classic controller once the attack is detected. The proposed model is tested on a DC motor as the plant and is put against a deception signal amplification attack over the forward link. Simulation results show that the detection algorithm well detects the intrusion and the compensator is also successful in alleviating the attack effects.

2020-07-10
Javed Butt, Usman, Abbod, Maysam, Lors, Anzor, Jahankhani, Hamid, Jamal, Arshad, Kumar, Arvind.  2019.  Ransomware Threat and its Impact on SCADA. 2019 IEEE 12th International Conference on Global Security, Safety and Sustainability (ICGS3). :205—212.
Modern cybercrimes have exponentially grown over the last one decade. Ransomware is one of the types of malware which is the result of sophisticated attempt to compromise the modern computer systems. The governments and large corporations are investing heavily to combat this cyber threat against their critical infrastructure. It has been observed that over the last few years that Industrial Control Systems (ICS) have become the main target of Ransomware due to the sensitive operations involved in the day to day processes of these industries. As the technology is evolving, more and more traditional industrial systems are replaced with advanced industry methods involving advanced technologies such as Internet of Things (IoT). These technology shift help improve business productivity and keep the company's global competitive in an overflowing competitive market. However, the systems involved need secure measures to protect integrity and availability which will help avoid any malfunctioning to their operations due to the cyber-attacks. There have been several cyber-attack incidents on healthcare, pharmaceutical, water cleaning and energy sector. These ICS' s are operated by remote control facilities and variety of other devices such as programmable logic controllers (PLC) and sensors to make a network. Cyber criminals are exploring vulnerabilities in the design of these ICS's to take the command and control of these systems and disrupt daily operations until ransomware is paid. This paper will provide critical analysis of the impact of Ransomware threat on SCADA systems.
2020-07-06
Chai, Yadeng, Liu, Yong.  2019.  Natural Spoken Instructions Understanding for Robot with Dependency Parsing. 2019 IEEE 9th Annual International Conference on CYBER Technology in Automation, Control, and Intelligent Systems (CYBER). :866–871.
This paper presents a method based on syntactic information, which can be used for intent determination and slot filling tasks in a spoken language understanding system including the spoken instructions understanding module for robot. Some studies in recent years attempt to solve the problem of spoken language understanding via syntactic information. This research is a further extension of these approaches which is based on dependency parsing. In this model, the input for neural network are vectors generated by a dependency parsing tree, which we called window vector. This vector contains dependency features that improves performance of the syntactic-based model. The model has been evaluated on the benchmark ATIS task, and the results show that it outperforms many other syntactic-based approaches, especially in terms of slot filling, it has a performance level on par with some state of the art deep learning algorithms in recent years. Also, the model has been evaluated on FBM3, a dataset of the RoCKIn@Home competition. The overall rate of correctly understanding the instructions for robot is quite good but still not acceptable in practical use, which is caused by the small scale of FBM3.
Castillo, Anya, Arguello, Bryan, Cruz, Gerardo, Swiler, Laura.  2019.  Cyber-Physical Emulation and Optimization of Worst-Case Cyber Attacks on the Power Grid. 2019 Resilience Week (RWS). 1:14–18.

In this paper we report preliminary results from the novel coupling of cyber-physical emulation and interdiction optimization to better understand the impact of a CrashOverride malware attack on a notional electric system. We conduct cyber experiments where CrashOverride issues commands to remote terminal units (RTUs) that are controlling substations within a power control area. We identify worst-case loss of load outcomes with cyber interdiction optimization; the proposed approach is a bilevel formulation that incorporates RTU mappings to controllable loads, transmission lines, and generators in the upper-level (attacker model), and a DC optimal power flow (DCOPF) in the lower-level (defender model). Overall, our preliminary results indicate that the interdiction optimization can guide the design of experiments instead of performing a “full factorial” approach. Likewise, for systems where there are important dependencies between SCADA/ICS controls and power grid operations, the cyber-physical emulations should drive improved parameterization and surrogate models that are applied in scalable optimization techniques.

2020-06-22
Cai, Huili, Liu, Xiaofeng, Cangelosi, Angelo.  2019.  Security of Cloud Intelligent Robot Based on RSA Algorithm and Digital Signature. 2019 IEEE Symposium Series on Computational Intelligence (SSCI). :1453–1456.
Considering the security of message exchange between service robot and cloud, we propose to authenticate the message integrity based on RSA algorithm and digital signature. In the process of message transmission, RSA algorithm is used to encrypt message for service robot and decrypt message for cloud. The digital signature algorithm is used to authenticate the source of the message. The results of experiment have proved that the proposed scheme can guarantee the security of message transmission.
2020-06-19
Cha, Suhyun, Ulbrich, Mattias, Weigl, Alexander, Beckert, Bernhard, Land, Kathrin, Vogel-Heuser, Birgit.  2019.  On the Preservation of the Trust by Regression Verification of PLC software for Cyber-Physical Systems of Systems. 2019 IEEE 17th International Conference on Industrial Informatics (INDIN). 1:413—418.

Modern large scale technical systems often face iterative changes on their behaviours with the requirement of validated quality which is not easy to achieve completely with traditional testing. Regression verification is a powerful tool for the formal correctness analysis of software-driven systems. By proving that a new revision of the software behaves similarly as the original version of the software, some of the trust that the old software and system had earned during the validation processes or operation histories can be inherited to the new revision. This trust inheritance by the formal analysis relies on a number of implicit assumptions which are not self-evident but easy to miss, and may lead to a false sense of safety induced by a misunderstood regression verification processes. This paper aims at pointing out hidden, implicit assumptions of regression verification in the context of cyber-physical systems by making them explicit using practical examples. The explicit trust inheritance analysis would clarify for the engineers to understand the extent of the trust that regression verification provides and consequently facilitate them to utilize this formal technique for the system validation.

2020-05-11
Kinkelin, Holger, Hauner, Valentin, Niedermayer, Heiko, Carle, Georg.  2018.  Trustworthy configuration management for networked devices using distributed ledgers. NOMS 2018 - 2018 IEEE/IFIP Network Operations and Management Symposium. :1–5.
Numerous IoT applications, like building automation or process control of industrial sites, exist today. These applications inherently have a strong connection to the physical world. Hence, IT security threats cannot only cause problems like data leaks but also safety issues which might harm people. Attacks on IT systems are not only performed by outside attackers but also insiders like administrators. For this reason, we present ongoing work on a Byzantine fault tolerant configuration management system (CMS) that provides control over administrators, restrains their rights, and enforces separation of concerns. We reach this goal by conducting a configuration management process that requires multi-party authorization for critical configurations to prevent individual malicious administrators from performing undesired actions. Only after a configuration has been authorized by multiple experts, it is applied to the targeted devices. For the whole configuration management process, our CMS guarantees accountability and traceability. Lastly, our system is tamper-resistant as we leverage Hyperledger Fabric, which provides a distributed execution environment for our CMS and a blockchain-based distributed ledger that we use to store the configurations. A beneficial side effect of this approach is that our CMS is also suitable to manage configurations for infrastructure shared across different organizations that do not need to trust each other.
2020-05-08
Ali, Yasir, Shen, Zhen, Zhu, Fenghua, Xiong, Gang, Chen, Shichao, Xia, Yuanqing, Wang, Fei-Yue.  2018.  Solutions Verification for Cloud-Based Networked Control System using Karush-Kuhn-Tucker Conditions. 2018 Chinese Automation Congress (CAC). :1385—1389.
The rapid development of the Cloud Computing Technologies (CCTs) has amended the conventional design of resource-constrained Network Control System (NCS) to the powerful and flexible design of Cloud-Based Networked Control System (CB-NCS) by relocating the processing part to the cloud server. This arrangement has produced many internets based exquisite applications. However, this new arrangement has also raised many network security challenges for the cloud-based control system related to cyber-physical part of the system. In the absence of robust verification methodology, an attacker can launch the modification attack in order to destabilize or take control of NCS. It is desirable that there shall be a solution authentication methodology used to verify whether the incoming solutions are coming from the cloud or not. This paper proposes a methodology used for the verification of the receiving solution to the local control system from the cloud using Karush-Kuhn-Tucker (KKT) conditions, which is then applied to actuator after verification and thus ensure the stability in case of modification attack.
Lavrova, Daria, Zegzhda, Dmitry, Yarmak, Anastasiia.  2019.  Using GRU neural network for cyber-attack detection in automated process control systems. 2019 IEEE International Black Sea Conference on Communications and Networking (BlackSeaCom). :1—3.
This paper provides an approach to the detection of information security breaches in automated process control systems (APCS), which consists in forecasting multivariate time series formed from the values of the operating parameters of the end system devices. Using an experimental model of water treatment, a comparison was made of the forecasting results for the parameters characterizing the operation of the entire model, and for the parameters characterizing the flow of individual subprocesses implemented by the model. For forecasting, GRU-neural network training was performed.
2020-05-04
Wang, Fang, Qi, Weimin, Qian, Tonghui.  2019.  A Dynamic Cybersecurity Protection Method based on Software-defined Networking for Industrial Control Systems. 2019 Chinese Automation Congress (CAC). :1831–1834.

In this paper, a dynamic cybersecurity protection method based on software-defined networking (SDN) is proposed, according to the protection requirement analysis for industrial control systems (ICSs). This method can execute security response measures by SDN, such as isolation, redirection etc., based on the real-time intrusion detection results, forming a detecting-responding closed-loop security control. In addition, moving target defense (MTD) concept is introduced to the protection for ICSs, where topology transformation and IP/port hopping are realized by SDN, which can confuse and deceive the attackers and prevent attacks at the beginning, protection ICSs in an active manner. The simulation results verify the feasibility of the proposed method.

Li, Mingxuan, Yang, Zhushi, He, Ling, Teng, Yangxin.  2019.  Research on Typical Model of Network Invasion and Attack in Power Industrial Control System. 2019 IEEE 4th Advanced Information Technology, Electronic and Automation Control Conference (IAEAC). 1:2070–2073.

Aiming at the operation characteristics of power industry control system, this paper deeply analyses the attack mechanism and characteristics of power industry control system intrusion. On the basis of classifying and sorting out the attack characteristics of power industrial control system, this paper also attaches importance to break the basic theory and consequential technologies of industrial control network space security, and constructs the network intrusion as well as attack model of power industrial control system to realize the precise characterization of attackers' attack behavior, which provides a theoretical model for the analysis and early warning of attack behavior analysis of power industrial control systems.

Chen, Jiaojiao, Liang, Xiangyang.  2019.  L2 Control for Networked Control Systems Subject to Denial-of-Service Attacks. 2019 International Conference on Computer Network, Electronic and Automation (ICCNEA). :502–505.
This paper focuses on the issue of designing L2 state feedback controller for networked control systems subject to unknown periodic denial-of-service (DoS) jamming attacks. Primarily, a resilient event-triggering mechanism is introduced to counteract the influence of DoS jamming attacks. Secondly, a switching system model of NCSs is set up. Then, the criteria of the exponential stability analysis is obtained by the piecewise Lyapunov functional approach based on the model. Thirdly, a co-design approach of the trigger parameters and L2 controller is developed. Lastly, a practical system is used for proving the efficiency of the proposed approach.
2020-04-17
Brugman, Jonathon, Khan, Mohammed, Kasera, Sneha, Parvania, Masood.  2019.  Cloud Based Intrusion Detection and Prevention System for Industrial Control Systems Using Software Defined Networking. 2019 Resilience Week (RWS). 1:98—104.

Industrial control systems (ICS) are becoming more integral to modern life as they are being integrated into critical infrastructure. These systems typically lack application layer encryption and the placement of common network intrusion services have large blind spots. We propose the novel architecture, Cloud Based Intrusion Detection and Prevention System (CB-IDPS), to detect and prevent threats in ICS networks by using software defined networking (SDN) to route traffic to the cloud for inspection using network function virtualization (NFV) and service function chaining. CB-IDPS uses Amazon Web Services to create a virtual private cloud for packet inspection. The CB-IDPS framework is designed with considerations to the ICS delay constraints, dynamic traffic routing, scalability, resilience, and visibility. CB-IDPS is presented in the context of a micro grid energy management system as the test case to prove that the latency of CB-IDPS is within acceptable delay thresholds. The implementation of CB-IDPS uses the OpenDaylight software for the SDN controller and commonly used network security tools such as Zeek and Snort. To our knowledge, this is the first attempt at using NFV in an ICS context for network security.

2020-03-27
Romagnoli, Raffaele, Krogh, Bruce H., Sinopoli, Bruno.  2019.  Design of Software Rejuvenation for CPS Security Using Invariant Sets. 2019 American Control Conference (ACC). :3740–3745.

Software rejuvenation has been proposed as a strategy to protect cyber-physical systems (CSPs) against unanticipated and undetectable cyber attacks. The basic idea is to refresh the system periodically with a secure and trusted copy of the online software so as to eliminate all effects of malicious modifications to the run-time code and data. This paper considers software rejuvenation design from a control-theoretic perspective. Invariant sets for the Lyapunov function for the safety controller are used to derive bounds on the time that the CPS can operate in mission control mode before the software must be refreshed. With these results it can be guaranteed that the CPS will remain safe under cyber attacks against the run-time system. The approach is illustrated using simulation of the nonlinear dynamics of a quadrotor system. The concluding section discusses directions for further research.

Lin, Nan, Zhang, Linrui, Chen, Yuxuan, Zhu, Yujun, Chen, Ruoxi, Wu, Peichen, Chen, Xiaoping.  2019.  Reinforcement Learning for Robotic Safe Control with Force Sensing. 2019 WRC Symposium on Advanced Robotics and Automation (WRC SARA). :148–153.

For the task with complicated manipulation in unstructured environments, traditional hand-coded methods are ineffective, while reinforcement learning can provide more general and useful policy. Although the reinforcement learning is able to obtain impressive results, its stability and reliability is hard to guarantee, which would cause the potential safety threats. Besides, the transfer from simulation to real-world also will lead in unpredictable situations. To enhance the safety and reliability of robots, we introduce the force and haptic perception into reinforcement learning. Force and tactual sensation play key roles in robotic dynamic control and human-robot interaction. We demonstrate that the force-based reinforcement learning method can be more adaptive to environment, especially in sim-to-real transfer. Experimental results show in object pushing task, our strategy is safer and more efficient in both simulation and real world, thus it holds prospects for a wide variety of robotic applications.

2020-03-02
Vatanparvar, Korosh, Al Faruque, Mohammad Abdullah.  2019.  Self-Secured Control with Anomaly Detection and Recovery in Automotive Cyber-Physical Systems. 2019 Design, Automation Test in Europe Conference Exhibition (DATE). :788–793.

Cyber-Physical Systems (CPS) are growing with added complexity and functionality. Multidisciplinary interactions with physical systems are the major keys to CPS. However, sensors, actuators, controllers, and wireless communications are prone to attacks that compromise the system. Machine learning models have been utilized in controllers of automotive to learn, estimate, and provide the required intelligence in the control process. However, their estimation is also vulnerable to the attacks from physical or cyber domains. They have shown unreliable predictions against unknown biases resulted from the modeling. In this paper, we propose a novel control design using conditional generative adversarial networks that will enable a self-secured controller to capture the normal behavior of the control loop and the physical system, detect the anomaly, and recover from them. We experimented our novel control design on a self-secured BMS by driving a Nissan Leaf S on standard driving cycles while under various attacks. The performance of the design has been compared to the state-of-the-art; the self-secured BMS could detect the attacks with 83% accuracy and the recovery estimation error of 21% on average, which have improved by 28% and 8%, respectively.

Bhat, Sriharsha, Stenius, Ivan, Bore, Nils, Severholt, Josefine, Ljung, Carl, Torroba Balmori, Ignacio.  2019.  Towards a Cyber-Physical System for Hydrobatic AUVs. OCEANS 2019 - Marseille. :1–7.
Cyber-physical systems (CPSs) encompass a network of sensors and actuators that are monitored, controlled and integrated by a computing and communication core. As autonomous underwater vehicles (AUVs) become more intelligent and connected, new use cases in ocean production, security and environmental monitoring become feasible. Swarms of small, affordable and hydrobatic AUVs can be beneficial in substance cloud tracking and algae farming, and a CPS linking the AUVs with multi-fidelity simulations can improve performance while reducing risks and costs. In this paper, we present a CPS concept tightly linking the AUV network in ROS to virtual validation using Simulink and Gazebo. A robust hardware-software interface using the open-source UAVCAN-ROS bridge is described for enabling hardware-in-the-loop validation. Hardware features of the hydrobatic SAM AUV are described, with a focus on subsystem integration. Results presented include pre-tuning of controllers, validation of mission plans in simulation and real time subsystem performance in tank tests. These first results demonstrate the interconnection between different system elements and offer a proof of concept.
Zhao, Zhijun, Jiang, Zhengwei, Wang, Yueqiang, Chen, Guoen, Li, Bo.  2019.  Experimental Verification of Security Measures in Industrial Environments. 2019 IEEE International Conference on Computational Science and Engineering (CSE) and IEEE International Conference on Embedded and Ubiquitous Computing (EUC). :498–502.
Industrial Control Security (ICS) plays an important role in protecting Industrial assets and processed from being tampered by attackers. Recent years witness the fast development of ICS technology. However there are still shortage of techniques and measures to verify the effectiveness of ICS approaches. In this paper, we propose a verification framework named vICS, for security measures in industrial environments. vICS does not requires installing any agent in industrial environments, and could be viewed as a non-intrusive way. We use vICS to evaluate the effectiveness of classic ICS techniques and measures through several experiments. The results shown that vICS provide an feasible solution for verifying the effectiveness of classic ICS techniques and measures for industrial environments.
2020-01-21
Hou, Ye, Such, Jose, Rashid, Awais.  2019.  Understanding Security Requirements for Industrial Control System Supply Chains. 2019 IEEE/ACM 5th International Workshop on Software Engineering for Smart Cyber-Physical Systems (SEsCPS). :50–53.

We address the need for security requirements to take into account risks arising from complex supply chains underpinning cyber-physical infrastructures such as industrial control systems (ICS). We present SEISMiC (SEcurity Industrial control SysteM supply Chains), a framework that takes into account the whole spectrum of security risks - from technical aspects through to human and organizational issues - across an ICS supply chain. We demonstrate the effectiveness of SEISMiC through a supply chain risk assessment of Natanz, Iran's nuclear facility that was the subject of the Stuxnet attack.

Fujdiak, Radek, Blazek, Petr, Mlynek, Petr, Misurec, Jiri.  2019.  Developing Battery of Vulnerability Tests for Industrial Control Systems. 2019 10th IFIP International Conference on New Technologies, Mobility and Security (NTMS). :1–5.

Nowadays, the industrial control systems (ICS) face many challenges, where security is becoming one of the most crucial. This fact is caused by new connected environment, which brings among new possibilities also new vulnerabilities, threats, or possible attacks. The criminal acts in the ICS area increased over the past years exponentially, which caused the loss of billions of dollars. This also caused classical Intrusion Detection Systems and Intrusion Prevention Systems to evolve in order to protect among IT also ICS networks. However, these systems need sufficient data such as traffic logs, protocol information, attack patterns, anomaly behavior marks and many others. To provide such data, the requirements for the test environment are summarized in this paper. Moreover, we also introduce more than twenty common vulnerabilities across the ICS together with information about possible risk, attack vector (point), possible detection methods and communication layer occurrence. Therefore, the paper might be used as a base-ground for building sufficient data generator for machine learning and artificial intelligence algorithms often used in ICS/IDS systems.

2020-01-20
He, Zecheng, Raghavan, Aswin, Hu, Guangyuan, Chai, Sek, Lee, Ruby.  2019.  Power-Grid Controller Anomaly Detection with Enhanced Temporal Deep Learning. 2019 18th IEEE International Conference On Trust, Security And Privacy In Computing And Communications/13th IEEE International Conference On Big Data Science And Engineering (TrustCom/BigDataSE). :160–167.
Controllers of security-critical cyber-physical systems, like the power grid, are a very important class of computer systems. Attacks against the control code of a power-grid system, especially zero-day attacks, can be catastrophic. Earlier detection of the anomalies can prevent further damage. However, detecting zero-day attacks is extremely challenging because they have no known code and have unknown behavior. Furthermore, if data collected from the controller is transferred to a server through networks for analysis and detection of anomalous behavior, this creates a very large attack surface and also delays detection. In order to address this problem, we propose Reconstruction Error Distribution (RED) of Hardware Performance Counters (HPCs), and a data-driven defense system based on it. Specifically, we first train a temporal deep learning model, using only normal HPC readings from legitimate processes that run daily in these power-grid systems, to model the normal behavior of the power-grid controller. Then, we run this model using real-time data from commonly available HPCs. We use the proposed RED to enhance the temporal deep learning detection of anomalous behavior, by estimating distribution deviations from the normal behavior with an effective statistical test. Experimental results on a real power-grid controller show that we can detect anomalous behavior with high accuracy (\textbackslashtextgreater99.9%), nearly zero false positives and short (\textbackslashtextless; 360ms) latency.
Warabino, Takayuki, Suzuki, Yusuke, Miyazawa, Masanori.  2019.  ROS-based Robot Development Toward Fully Automated Network Management. 2019 20th Asia-Pacific Network Operations and Management Symposium (APNOMS). :1–4.

While the introduction of the softwarelization technologies such as SDN and NFV transfers main focus of network management from hardware to software, the network operators still have to care for a lot of network and computing equipment located in the network center. Toward fully automated network management, we believe that robotic approach will be significant, meaning that robot will care for the physical equipment on behalf of human. This paper explains our experience and insight gained throughout development of a network management robot. We utilize ROS(Robot Operating System) which is a powerful platform for robot development and secures the ease of development and expandability. Our roadmap of the network management robot is also shown as well as three use cases such as environmental monitoring, operator assistance and autonomous maintenance of the equipment. Finally, the paper briefly explains experimental results conducted in a commercial network center.

2020-01-13
Zegzhda, Dmitry, Lavrova, Daria, Khushkeev, Aleksei.  2019.  Detection of information security breaches in distributed control systems based on values prediction of multidimensional time series. 2019 IEEE International Conference on Industrial Cyber Physical Systems (ICPS). :780–784.
Proposed an approach for information security breaches detection in distributed control systems based on prediction of multidimensional time series formed of sensor and actuator data.
2019-12-30
Kubo, Ryogo.  2018.  Detection and Mitigation of False Data Injection Attacks for Secure Interactive Networked Control Systems. 2018 IEEE International Conference on Intelligence and Safety for Robotics (ISR). :7-12.

Cybersecurity in control systems has been actively discussed in recent years. In particular, networked control systems (NCSs) over the Internet are exposed to various types of cyberattacks such as false data injection attacks. This paper proposes a detection and mitigation method of the false data injection attacks in interactive NCSs, i.e., bilateral teleoperation systems. A bilateral teleoperation system exchanges position and force information through the Internet between the master and slave robots. The proposed method utilizes two redundant communication channels for both the master-to-slave and slave-to-master paths. The attacks are detected by a tamper detection observer (TDO) on each of the master and slave sides. The TDO compares the position responses of actual robots and robot models. A path selector on each side chooses the appropriate position and force responses from the responses received through the two communication channels, based on the outputs of the TDO. The proposed method is validated by simulations with attack models.