| 1. |
- Sato, T., et al.
(författare)
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Particle and Heavy Ion Transport code System, PHITS, version 2.52
- 2013
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Ingår i: Journal of Nuclear Science and Technology. - : Informa UK Limited. - 0022-3131 .- 1881-1248. ; 50:9, s. 913-923
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Tidskriftsartikel (refereegranskat)abstract
- An upgraded version of the Particle and Heavy Ion Transport code System, PHITS2.52, was developed and released to the public. The new version has been greatly improved from the previously released version, PHITS2.24, in terms of not only the code itself but also the contents of its package, such as the attached data libraries. In the new version, a higher accuracy of simulation was achieved by implementing several latest nuclear reaction models. The reliability of the simulation was improved by modifying both the algorithms for the electron-, positron-, and photon-transport simulations and the procedure for calculating the statistical uncertainties of the tally results. Estimation of the time evolution of radioactivity became feasible by incorporating the activation calculation program DCHAIN-SP into the new package. The efficiency of the simulation was also improved as a result of the implementation of shared-memory parallelization and the optimization of several time-consuming algorithms. Furthermore, a number of new user-support tools and functions that help users to intuitively and effectively perform PHITS simulations were developed and incorporated. Due to these improvements, PHITS is now a more powerful tool for particle transport simulation applicable to various research and development fields, such as nuclear technology, accelerator design, medical physics, and cosmic-ray research.
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| 2. |
- Hashimoto, K., et al.
(författare)
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Event-triggered intermittent sampling for nonlinear model predictive control
- 2017
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Ingår i: Automatica. - : Elsevier Ltd. - 0005-1098 .- 1873-2836. ; 81, s. 148-155
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we propose a new aperiodic formulation of model predictive control for nonlinear continuous-time systems. Unlike earlier approaches, we provide event-triggered conditions without using the optimal cost as a Lyapunov function candidate. Instead, we evaluate the time interval when the optimal state trajectory enters a local set around the origin. The obtained event-triggered strategy is more suitable for practical applications than the earlier approaches in two directions. First, it does not include parameters (e.g., Lipschitz constant parameters of stage and terminal costs) which may be a potential source of conservativeness for the event-triggered conditions. Second, the event-triggered conditions are necessary to be checked only at certain sampling time instants, instead of continuously. This leads to the alleviation of the sensing cost and becomes more suitable for practical implementations under a digital platform. The proposed event-triggered scheme is also validated through numerical simulations.
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| 3. |
- Hashimoto, K., et al.
(författare)
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Self-Triggered Model Predictive Control for Nonlinear Input-Affine Dynamical Systems via Adaptive Control Samples Selection
- 2017
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Ingår i: IEEE Transactions on Automatic Control. - : IEEE. - 0018-9286 .- 1558-2523. ; 62:1, s. 177-189
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we propose a self-Triggered formulation of model predictive control for continuous-Time nonlinear input-Affine networked control systems. Our control method specifies not only when to execute control tasks but also provides a way to discretize the optimal control trajectory into several control samples, so that the reduction of communication load will be obtained. Stability analysis under the sample-And-hold implementation is also given, which guarantees that the state converges to a terminal region where the system can be stabilized by a local state feedback controller. Some simulation examples validate our proposed framework.
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| 4. |
- Hashimoto, Kazumune, et al.
(författare)
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Self-triggered nonlinear model predictive control for networked control systems
- 2015
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Ingår i: Proceedings of the American Control Conference. - : IEEE conference proceedings. - 9781479986842 ; , s. 4239-4244
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Konferensbidrag (refereegranskat)abstract
- In this paper, we propose a self-triggered formulation of Model Predictive Control for continuous-time nonlinear networked control systems. Our control method derives not only when to execute control tasks but also provides the way to discretize the optimal control trajectory so as to alleviate the communication burden as much as possible. Stability analysis under the sample-and-hold implementation is also given in detail, which guarantees that the state converges to a terminal region where the local linear state feedback can stabilize the system. A simulation example verifies our proposed framework.
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| 5. |
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| 6. |
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| 7. |
- Hashimoto, K., et al.
(författare)
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A Collision-free Communication Scheduling for Nonlinear Model Predictive Control
- 2017
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Ingår i: IFAC-PapersOnLine. - : Elsevier. - 2405-8963. ; 50:1, s. 8939-8944
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we propose a framework to generate communication schedulings for nonlinear model predictive control. The proposed method considers the case where multiple plants share a communication network, and the goal is to pre-plan for each plant a timing to communicate with the controller to solve an optimal control problem. The desired communication schedulings are generated such that: (i) no network collisions occur; (ii) convergence to a prescribed local set around the origin is guaranteed for all plants. When formulating an algorithm, we additionally propose an optimization problem that is similar to the standard collision avoidance problem of controlling multi-agent systems. To validate our proposed scheme, a control problem of three inverted pendulums is simulated.
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| 8. |
- Hashimoto, Kazumune, et al.
(författare)
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Distributed event-based model predictive control for multi-agent systems under disturbances
- 2017
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Ingår i: 2014 7th International Conference on Network Games, Control and Optimization, NetGCoop 2014. - : Institute of Electrical and Electronics Engineers (IEEE). - 9788884435743 ; , s. 255-261
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Konferensbidrag (refereegranskat)abstract
- In this paper, we propose an aperiodic formulation of Distributed Model Predictive Control for the cooperation of multi-agent systems under additive bounded disturbances. In the proposed method, each agent solves an Optimal Control Problem only when certain control performances cannot be guaranteed according to certain triggering rules. This could lead to the reduction of energy consumption and the alleviation of over-usage of communication loads under critical resource constraints in networked control systems, such as limited communication power and the life-time of the battery. The triggering rule is derived for event-based case, where control inputs are executed based on the current state measurement. Our proposed method is also verified through a simple simulation example.
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| 9. |
- Hashimoto, K., et al.
(författare)
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Self-triggered control for constrained systems : A contractive set-based approach
- 2017
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Ingår i: American Control Conference (ACC), 2017. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781509059928 ; , s. 1011-1016
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Konferensbidrag (refereegranskat)abstract
- In this paper, a self-triggered control scheme for constrained discrete-time control systems is presented. The key idea of our approach is to construct a transition system or a graph structure from a collection of polyhedral sets, which are generated based on the notion of set-invariance theory. The inter-event time steps are then determined through a standard graph search algorithm to obtain the minimal total cost to a terminal state. The proposed strategy is illustrated through a numerical example.
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| 10. |
- Hashimoto, K., et al.
(författare)
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Time-constrained event-triggered Model Predictive Control for nonlinear continuous-time systems
- 2016
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Ingår i: Proceedings of the IEEE Conference on Decision and Control. - : IEEE conference proceedings. - 9781479978861 ; , s. 4326-4331
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Konferensbidrag (refereegranskat)abstract
- In this paper we propose a new event-triggered scheme for nonlinear continuous-time systems with additive bounded disturbances. Unlike existing results, the proposed event-triggered strategy is not derived from Lyapunov stability analysis. Instead, it is obtained from the time interval when the state reaches a local region around the origin. By guaranteeing that this time interval becomes smaller as the optimal control problem is solved, we ensure that the state converges to the prescribed set in finite time.
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