Kiminao Kogiso

Cyber-security enhancement of networked control systems using homomorphic encryption

This paper proposes a new concept of controller encryption for enhancement of the cyber-security of networked control systems and presents how to encrypt a linear controller using our modified homomorphic encryption schemes based on public-key RSA and ElGamal encryption systems. A remarkable advantage of the controller encryption is to be able to conceal several informations processed inside the controller device, such as controller parameters, references (recipes), measurements, control commands, and parameters of plant models in the internal model principal, maintaining an original function of the controller. Therefore, even if malicious users hacked the controller device by unauthorized accesses, it would take much time and cost to decipher and steal the control systems information. Finally, numerical examples confirm that only the scrambled parameters and signals can be seen in the controller device of the security-enhanced networked control system.

Hybrid nonlinear model of McKibben pneumatic artificial muscle systems incorporating a pressure-dependent Coulomb friction coefficient

This study presents a more precise hybrid nonlinear model of pneumatic artificial muscle (PAM) systems actuated by a proportional directional control valve and confirms the validity of the presented model using various commercial PAMs. To enhance the precision, the Coulomb friction coefficient was incorporated as a function of the PAM inner-pressure. To evaluate the contribution of the modification to the modeling of PAM behavior, the authors determine whether the parameters are effectively observed, whether precision of the model is improved, and whether the model is applicable to various commercial PAM products from ActiveLink and FESTO. Furthermore, this study investigates the impacts on time responses and parameters when the temperature increases from 293 to 313 K. In addition to investigations concerning the validity, the authors show that the achievement of this study is an extension of the previously proposed nonlinear PAM model.

Applications of UKF and EnKF to estimation of contraction ratio of McKibben pneumatic artificial muscles

This study applies the unscented Kalman filter (UKF) and the ensemble Kalman filter (EnKF) to estimate a contraction ratio of the McKibben pneumatic artificial muscle (PAM) and to present that the UKF is more effective than the EnKF in estimating the PAM length. Both filters were applied for a commercial PAM, FESTO DMSP-20-200N, to validate them. The estimation was conducted offline under three types of sinusoidal control signals, which are a voltage inputted to a proportional directional control valve. The inner pressure in those cases travels in low, high, and whole ranges between 0.2 and 0.7 [MPa] respectively. An alternative technique of measuring the length using a sensor device is important in making full use of the PAMs merit.

Code review participation: game theoretical modeling of reviewers in gerrit datasets

Code review is a common practice for improving the quality of source code changes and expediting knowledge transfer in a development community. In modern code review, source code changes or patches are considered to be assessed and approved for integration by multiple reviews. However, from our empirical study, we found that some patches are reviewed by only one reviewer, and some reviewers did not continue the review discussion, which can have negative effects on software quality. To understand these reviewers behaviors, we model the code review situation based on the snowdrift game, which is used to analyze social dilemmas. With this game-theoretical modeling, we found that it can explain reviewers behaviors well.

Simultaneous Estimation of Contraction Ratio and Parameter of McKibben Pneumatic Artificial Muscle Model Using Log-Normalized Unscented Kalman Filter

Using an unscented Kalman filter (UKF), the paper estimates the contraction ratio and unknown parameters in a mathematical model of McKibben pneumatic artificial muscle. In an application study, the UKF effectively estimated the contraction ratio and the unknown parameters at various the measured pressures.

Application of Particle Swarm Optimization to Parameter Estimation of a McKibben Pneumatic Artificial Muscle Model

In this study, the authors apply particle swarm optimization to estimate the unknown parameters of a McKibben pneumatic artificial muscle model. The estimation results show that the best parameters are obtained without trial and error of the heuristic method.

Transition models of equilibrium assessment in Bayesian game

This study proposes two novel deterministic transition models of a belief and a Bayesian Nash equilibrium (BNE) for static Bayesian games. The transition models can be obtained from the Karush-Kuhn-Tucker condition, and as a result, they are expressed in a discrete-time time-varying autonomous system in the state-space representation that expresses evolution of the belief and the BNE. As well, this study analytically checks stability of the models. A contribution of this study is to make it possible to apply our model-based fashions to analysis and design problems related to the Bayesian game.

Security enhancements of networked control systems using RSA public-key cryptosystem

To enhance the security of networked control systems, we propose the concept of secured control rules that is defined as a method that achieves concealing both signals over communication channels and parameters within controllers. Our method proposed in this study uses the homomorphism of the RSA cryptosystem to determine control signals directly from encrypted feedback signals and control parameters without performing any decryption processes. A numerical simulation confirms that the proposed method contributes to the improvement of security.

Parameter extraction for identifying product type of mckibben pneumatic artificial muscles

This study demonstrates that various unknown parameters used in nonlinear models of McKibben pneumatic artificial muscles (PAMs) can characterize the features of McKibben PAM products. By focusing on a parameter space in the PAM model, this study employs a support vector machine (SVM) to determine which unknown parameters characterize each PAM product. For validation, three different PAM products are analyzed to observe whether the resulting minimal combination of parameters will help to identify the product. The observation is expected to provide prior PAM knowledge that can be used to develop efficient parameter estimation and capture aging degradation, which are important for robust estimation and control in PAM systems.

Steady-state analysis of autonomous system in equilibrium assessment of Bayesian game

This study presents an analysis result in connection between Bayesian Nash equilibrium (BNE) and parameters of an autonomous dynamical system expressing transitions of an equilibrium assessment in a static Bayesian game. A numerical example of the Bayesian game confirms that the analysis result is useful for determining the systems parameters.