| 1. |
- Chi, Xiaoming, et al.
(författare)
-
Fractal superconducting nanowire single-photon detectors with reduced polarization sensitivity
- 2018
-
Ingår i: Optics Letters. - : OPTICAL SOC AMER. - 0146-9592 .- 1539-4794. ; 43:20, s. 5017-5020
-
Tidskriftsartikel (refereegranskat)abstract
- We demonstrate superconducting nanowire single-photon detectors (SNSPDs) based on a fractal design of the nanowires to reduce the polarization sensitivity of detection efficiency. We patterned niobium titanium nitride thin films into Peano curves with a linewidth of 100 nm and integrated the nanowires with optical microcavities to enhance their optical absorption. At a base temperature of 2.6 K, the fractal SNSPD exhibited a polarization-maximum device efficiency of 67% and a polarization-minimum device efficiency of 61% at a wavelength of 1550 nm. Therefore, the polarization sensitivity, defined as their ratio, was 1.1, lower than the polarization sensitivity of the SNSPDs in the meander design. The reduced polarization sensitivity of the detector could be maintained for higher-order spatial modes in multimode optical fibers and could tolerate misalignment between the optical mode and the detector. This fractal design is applicable to both amorphous and polycrystalline materials that are commonly used for making SNSPDs.
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| 2. |
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| 3. |
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| 4. |
- Guo, Chaoqun, et al.
(författare)
-
Fixed-time safe tracking control of uncertain high-order nonlinear pure-feedback systems via unified transformation functions
- 2023
-
Ingår i: Kybernetika (Praha). - : Institute of Information Theory and Automation. - 0023-5954 .- 1805-949X. ; 59:3, s. 342-364
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, a fixed-time safe control problem is investigated for an uncertain high-order nonlinear pure-feedback system with state constraints. A new nonlinear transformation function is firstly proposed to handle both the constrained and unconstrained cases in a unified way. Further, a radial basis function neural network is constructed to approximate the unknown dynamics in the system and a fixed-time dynamic surface control (FDSC) technique is developed to facilitate the fixed-time control design for the uncertain high-order pure-feedback system. Combined with the proposed unified transformation function and the FDSC technique, an adaptive fixed-time control strategy is proposed to guarantee the fixed-time tracking. The novel original results of the paper allow to design the independent unified flexible fixed-time control strategy taking into account the actual possible constraints, either present or missing. Numerical examples are presented to demonstrate the proposed fixed-time tracking control strategy.
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| 5. |
- Hu, C., et al.
(författare)
-
Distributed adaptive Kalman filter based on variational Bayesian technique
- 2019
-
Ingår i: Control Theory and Technology. - : South China University of Technology. - 2095-6983 .- 2198-0942. ; 17:1, s. 37-47
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, distributed Kalman filter design is studied for linear dynamics with unknown measurement noise variance, which modeled by Wishart distribution. To solve the problem in a multi-agent network, a distributed adaptive Kalman filter is proposed with the help of variational Bayesian, where the posterior distribution of joint state and noise variance is approximated by a free-form distribution. The convergence of the proposed algorithm is proved in two main steps: noise statistics is estimated, where each agent only use its local information in variational Bayesian expectation (VB-E) step, and state is estimated by a consensus algorithm in variational Bayesian maximum (VB-M) step. Finally, a distributed target tracking problem is investigated with simulations for illustration.
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| 6. |
- Hu, J., et al.
(författare)
-
Adaptive bipartite tracking control for coopetition networks
- 2015
-
Ingår i: 2015 34th Chinese Control Conference (CCC). - : IEEE Computer Society. - 9789881563897 ; , s. 7067-7072
-
Konferensbidrag (refereegranskat)abstract
- Cooperation and competition are two typical interactional relationships in natural and engineering networked systems. Some interesting collective behaviors can emerge through local interactions within the networked systems. This paper considers a bipartite consensus for a group of agents interacting both cooperatively and competitively. Meanwhile, the intrinsic nonlinear dynamics of all the agents are unknown for the neighboring agents. Thus, the interaction network, which we call a coopetition network, is firstly represented by a signed graph. Then, some adaptive estimate laws are proposed for the unknown dynamics. Finally, an adaptive tracking control is designed for each agent to reach a bipartite consensus on the state of the leader. Some sufficient conditions are derived for bipartite consensus of multi-agent systems with the help of a structural balance theory. Simulation results are provided to demonstrate the bipartite consensus formation.
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| 7. |
- Hu, J., et al.
(författare)
-
Bipartite consensus strategies for coopetition networks
- 2014
-
Ingår i: 2014 33rd Chinese Control Conference (CCC). - : IEEE Computer Society. - 9789881563842 ; , s. 1505-1510
-
Konferensbidrag (refereegranskat)abstract
- Cooperation and competition are two typical interactional relationships in natural and engineering networked systems. Some interesting collective behaviors can emerge through local interactions within the networked systems. This paper focuses on the coexistence of competition and cooperation (i.e., coopetition) at the network level and, simultaneously, the collective dynamics on such coopetition networks. The coopetition network is represented by a directed signed graph. The interaction relationship between the agents on the coopetition network is described by a multi-agent system. We investigate two bipartite consensus strategies for the agents such that all the agents converge to a final state characterized by identical modulus but opposite sign. Under a weak connectivity assumption that the signed network has a spanning tree, some sufficient conditions are derived for bipartite consensus of multi-agent systems with the help of a structural balance theory. Finally, simulation results are provided to demonstrate the bipartite consensus formation.
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| 8. |
- Hu, J., et al.
(författare)
-
Distributed shift target estimation using multiple cooperative agents
- 2009
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Ingår i: Proceedings of 2009 7th Asian Control Conference, ASCC 2009. - 9788995605691 ; , s. 117-122
-
Konferensbidrag (refereegranskat)abstract
- In this paper we discuss the estimation of a moving target by cooperative agents equipped with sensors. To locate a moving target, a distributed algorithm is given for the networked agents based on a time-based shift. A nonlinear filter with fusing collected sensor information is proposed to estimate the trajectory of the target with unknown dynamics. The convergence of the estimation in the sensor network is analyzed and proved via a theoretic approach.
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| 9. |
- Hu, Jiangping, et al.
(författare)
-
Nonlinear filtering in target tracking using cooperative mobile sensors
- 2010
-
Ingår i: Automatica. - : Elsevier BV. - 0005-1098 .- 1873-2836. ; 46:12, s. 2041-2046
-
Tidskriftsartikel (refereegranskat)abstract
- Collaborative signal processing and sensor deployment have been among the most important research tasks in target tracking using networked sensors In this paper the mathematical model is formulated for single target tracking using mobile nonlinear scalar range sensors Then a sensor deployment strategy is proposed for the mobile sensors and a nonlinear convergent filter is built to estimate the trajectory of the target.
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| 10. |
- Hu, J., et al.
(författare)
-
Nonlinear shift estimation and optimal sensor deployment for target tracking
- 2010
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Ingår i: 2010 8th IEEE International Conference on Control and Automation, ICCA 2010. - : IEEE. - 9781424451951 ; , s. 773-778
-
Konferensbidrag (refereegranskat)abstract
- In this paper, the mathematical model for target tracking using nonlinear scalar range sensors is formulated first. Sensors are classified into active sensors and submissive sensors according to the relative distances with the target. Then two different estimation algorithms accompanying with an optimal sensor deployment strategy are proposed for both active and submissive sensors to estimate the trajectory of the target. Finally, some numerical examples are given to validate the proposed tracking algorithm.
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| 11. |
- Hu, Jiangping, et al.
(författare)
-
Optimal Target Trajectory Estimation and Filtering Using Networked Sensors
- 2008
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Ingår i: PROCEEDINGS OF THE 27TH CHINESE CONTROL CONFERENCE, VOL 7. - HAIDIAN QU DISTRICT : BEIJING UNIV AERONAUTICS & ASTRONAUTICS PRESS. ; , s. 540-545
-
Konferensbidrag (refereegranskat)abstract
- Target tracking using distributed sensor network is in general a challenging problem because it always needs to deal with real-time processing of noisy information. In this paper the problem of using nonlinear sensors such as distance and direction sensors for estimating a moving target is studied. The problem is formulated as a prudent design of nonlinear filters fora linear system subject to noisy nonlinear measurements and partially unknown input, which is generated by an exogenous system. In the worst case where the input is completely unknown, the exogenous dynamics is reduced to the random walk model. It can be shown that the nonlinear filter will have optimal convergence if the number of the sensors are large enough and the convergence rate will be highly improved if the sensors are deployed appropriately. This actually raises an interesting issue on active sensing: how to optimally move the sensors if they are considered as mobile multi-agent systems? Finally, a simulation example is given to illustrate and validate the construction of our filter.
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| 12. |
- Hu, Jiangping, et al.
(författare)
-
Optimal target trajectory estimation and filtering using networked sensors
- 2008
-
Ingår i: Journal of Systems Science and Complexity. - : Springer Science and Business Media LLC. - 1009-6124 .- 1559-7067. ; 21:3, s. 325-336
-
Tidskriftsartikel (refereegranskat)abstract
- Target tracking using distributed sensor network is in general a challenging problem because it always needs to deal with real-time processing of noisy information. In this paper the problem of using nonlinear sensors such as distance and direction sensors for estimating a moving target is studied. The problem is formulated as a prudent design of nonlinear filters for a linear system subject to noisy nonlinear measurements and partially unknown input, which is generated by an exogenous system. In the worst case where the input is completely unknown, the exogenous dynamics is reduced to the random walk model. It can be shown that the nonlinear filter will have optimal convergence if the number of the sensors are large enough and the convergence rate will be highly improved if the sensors are deployed appropriately. This actually raises an interesting issue on active sensing: how to optimally move the sensors if they are considered as mobile multi-agent systems? Finally, a simulation example is given to illustrate and validate the construction of our filter.
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| 13. |
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| 14. |
- Hu, Xiaolong, et al.
(författare)
-
Fractal superconducting nanowire single-photon detectors and their applications in polarimetric imaging
- 2024
-
Ingår i: Advanced Photon Counting Techniques XVIII. - : SPIE.
-
Konferensbidrag (refereegranskat)abstract
- In this paper, we review the research and development of the fractal superconducting nanowire single-photon detectors (SNSPDs), including our demonstrations of high-performance devices and systems with over 80% system detection efficiency, negligibly low residual polarization sensitivity, and low timing jitter. Using the fractal SNSPDs, we demonstrate full-Stokes polarimetric imaging LiDAR.
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| 15. |
- Hu, Xiaolong, et al.
(författare)
-
Superconducting nanowire single-photon detectors at the infrared spectrum range : detection efficiency and timing jitter
- 2019
-
Ingår i: TERAHERTZ, RF, MILLIMETER, AND SUBMILLIMETER-WAVE TECHNOLOGY AND APPLICATIONS XII. - : SPIE. - 9781510624771
-
Konferensbidrag (refereegranskat)abstract
- This paper reviews some recent research progress in superconducting nanowire single-photon detectors (SNSPDs) at the infrared spectrum range, with particular emphasis on detection efficiency and timing jitter. For detection efficiency, we present fractal SNSPDs with reduced polarization sensitivity; for timing jitter, we present two mechanisms of device timing jitter - vortex-crossing-induced timing jitter and spatial-inhomogeneity-induced timing jitter.
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| 16. |
- Hu, Xiaolong, et al.
(författare)
-
Timing properties of superconducting nanowire single-photon detectors
- 2019
-
Ingår i: Quantum Optics and Photon Counting 2019. - : SPIE - International Society for Optical Engineering. - 9781510627215
-
Konferensbidrag (refereegranskat)abstract
- In this paper, we review theoretical and experimental research progress on timing properties of superconducting nanowire single-photon detectors, including six possible mechanisms that induce timing jitter and experiments towards ultra-low timing jitter.
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| 17. |
- Jiangping, Hu, et al.
(författare)
-
Cooperative shift estimation of target trajectory using clustered sensors
- 2014
-
Ingår i: Journal of Systems Science and Complexity. - : Springer Science and Business Media LLC. - 1009-6124 .- 1559-7067. ; 27:3, s. 413-429
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, a mathematical model for target tracking using nonlinear scalar range sensors is formulated first. A time-shift sensor scheduling strategy is addressed on the basis of a k-barrier coverage protocol and all the sensors are divided into two classes of clusters, active cluster, and submissive cluster, for energy-saving. Then two types of time-shift nonlinear filters are proposed for both active and submissive clusters to estimate the trajectory of the moving target with disturbed dynamics. The stochastic stability of the two filters is analyzed. Finally, some numerical simulations are given to demonstrate the effectiveness of the new filters with a comparison of EKF.
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| 18. |
- Lu, Y., et al.
(författare)
-
Fuzzy hegselmann-krause opinion dynamics with opinion leaders
- 2019
-
Ingår i: 2019 Chinese Control Conference (CCC). ; , s. 6019-6024
-
Konferensbidrag (refereegranskat)abstract
- In this paper, from the perspective of opinion dynamics theory, we investigate the intrinsic interaction principles of a group of autonomous agents and develop a fuzzy opinion dynamics model with leaders. First, this paper divides group agents into three subgroups: opinion followers, positive opinion leaders, and negative opinion leaders according to the opinion's update manner and influence. Then, we consider the uncertainty of the agents' opinion gaps and apply the Fuzzy Inference Machine to the effects of the leaders' opinions on a certain follower's opinion. The innovation of this paper is that the weight is distributed from 0 to 1 in accordance with the closeness among the opinion leaders and followers, which is closer to real life. Finally, the simulation results show that the proposed model can effectively explain the opinion interaction and evolution and conforms with the existing theoretical results in the field of opinion dynamics.
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| 19. |
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| 20. |
- Wang, Xiaoming, et al.
(författare)
-
Phosphate Sorption Speciation and Precipitation Mechanisms on Amorphous Aluminum Hydroxide
- 2019
-
Ingår i: Soil Systems. - : MDPI. - 2571-8789. ; 3:1
-
Tidskriftsartikel (refereegranskat)abstract
- Aluminum (Al) oxides are important adsorbents for phosphate in soils and sediments, and significantly limit Phosphate (P) mobility and bioavailability, but the speciation of surface-adsorbed phosphate on Al oxides remains poorly understood. Here, phosphate sorption speciation on amorphous Al hydroxide (AAH) was determined under pH 3-8 and P concentration of 0.03 mM-15 mM using various spectroscopic approaches, and phosphate precipitation mechanisms were discussed as well. AAH exhibits an extremely high phosphate sorption capacity, increasing from 3.80 mmol/g at pH 7 to 4.63 mmol/g at pH 3. Regardless of reaction pH, with increasing P sorption loading, the sorption mechanism transits from bidentate binuclear (BB) surface complexation with d(P-Al) of 3.12 angstrom to surface precipitation of analogous amorphous AlPO4 (AAP), possibly with ternary complexes, such as (equivalent to Al-O)(2)-PO2-Al, as intermediate products. Additionally, the percentage of precipitated phosphate occurring in AAP linearly and positively correlates with P sorption loading. Compared to phosphate reaction with ferrihydrite, phosphate adsorbs and precipitates more readily on AAH due to the higher solubility product (K-sp) of AAH. The formation of AAP particles involves Al-III release, which is promoted by phosphate adsorption, and its subsequent precipitation with phosphate at AAH surfaces or in the bulk solution.
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| 21. |
- Xu, Jianqiang, et al.
(författare)
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Design of Smart Unstaffed Retail Shop Based on IoT and Artificial Intelligence
- 2020
-
Ingår i: IEEE Access. - : Institute of Electrical and Electronics Engineers (IEEE). - 2169-3536. ; 8, s. 147728-147737
-
Tidskriftsartikel (refereegranskat)abstract
- Unstaffed retail shops have emerged recently and been noticeably changing our shopping styles. In terms of these shops, the design of vending machine is critical to user shopping experience. The conventional design typically uses weighing sensors incapable of sensing what the customer is taking. In the present study, a smart unstaffed retail shop scheme is proposed based on artificial intelligence and the internet of things, as an attempt to enhance the user shopping experience remarkably. To analyze multiple target features of commodities, the SSD (300x300) algorithm is employed; the recognition accuracy is further enhanced by adding sub-prediction structure. Using the data set of 18, 000 images in different practical scenarios containing 20 different type of stock keeping units, the comparison experimental results reveal that the proposed SSD (300x300) model outperforms than the original SSD (300x300) in goods detection, the mean average precision of the developed method reaches 96.1% on the test dataset, revealing that the system can make up for the deficiency of conventional unmanned container. The practical test shows that the system can meet the requirements of new retail, which greatly increases the customer flow and transaction volume.
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| 22. |
- Anisi, David A., et al.
(författare)
-
Active Observers for Mobile Robotic Systems
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- An important class of non-uniformly observable systems come from applications in mobile robotics. In this paper, the problem of active observer design for such systems is considered. The set of feasible configurations and the set of output flow equivalent states is defined. It is shown that the inter-relation between these two sets serves as the basis for design of active observers. The proposed observer design method is illustrated by considering a unicycle robot model, equipped with a set of range-measuring sensors.
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| 23. |
- Anisi, David A., 1977-, et al.
(författare)
-
Communication constrained multi-UGV surveillance
- 2008
-
Ingår i: IFAC World Congress. - Seoul, Korea.
-
Konferensbidrag (refereegranskat)abstract
- This paper addresses the problem of connectivity constrained surveillance of a given polyhedral area with obstacles using a group of Unmanned Ground Vehicles (UGVs). The considered communication restrictions may involve both line-of-sight constraints and limited sensor range constraints. In this paper, the focus is on dynamic information graphs, G, which are required to be kept recurrently connected. The main motivation for introducing this weaker notion of connectivity is security and surveillance applications where the sentry vehicles may have to split temporary in order to complete the given mission efficiently but are required to establish contact recurrently in order to exchange information or to make sure that all units are intact and well-functioning. From a theoretical standpoint, recurrent connectivity is shown to be sufficient for exponential convergence of consensus filters for the collected sensor data.
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| 24. |
- Anisi, David A., et al.
(författare)
-
Cooperative Minimum Time Surveillance With Multiple Ground Vehicles
- 2010
-
Ingår i: IEEE Transactions on Automatic Control. - 0018-9286 .- 1558-2523. ; 55:12, s. 2679-2691
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, we formulate and solve two different minimum time problems related to unmanned ground vehicle (UGV) surveillance. The first problem is the following. Given a set of surveillance UGVs and a polyhedral area, find waypoint-paths for all UGVs such that every point of the area is visible from a point on a path and such that the time for executing the search in parallel is minimized. Here, the sensors' field of view are assumed to have a limited coverage range and be occluded by the obstacles. The second problem extends the first by additionally requiring the induced information graph to be connected at the time instants when the UGVs perform the surveillance mission, i.e., when they gather and transmit sensor data. In the context of the second problem, we also introduce and utilize the notion of recurrent connectivity, which is a significantly more flexible connectivity constraint than, e.g., the 1-hop connectivity constraints and use it to discuss consensus filter convergence for the group of UGVs.
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| 25. |
- Anisi, David A., et al.
(författare)
-
Cooperative Surveillance Missions with Multiple Unmanned Ground Vehicles (UGVs)
- 2008
-
Ingår i: 47TH IEEE CONFERENCE ON DECISION AND CONTROL, 2008 (CDC 2008). - 9781424431243 ; , s. 2444-2449
-
Konferensbidrag (refereegranskat)abstract
- This paper proposes an optimization based approach to multi-UGV surveillance. In particular, we formulate both the minimum time- and connectivity constrained surveillance problems, show NP-hardness of them and propose decomposition techniques that allow us to solve them efficiently in an algorithmic manner. The minimum time formulation is the following. Given a set of surveillance UGVs and a polyhedral area, find waypoint-paths for all UGVs such that every point of the area is visible from a point on a path and such that the time for executing the search in parallel is minimized. Here, the sensor's field of view are assumed to be occluded by the obstacles and limited by a maximal sensor range. The connectivity constrained formulation extends the first by additionally requiring that the information graph induced by the sensors is connected at the time instants when the UGVs stop to perform the surveillance task. The second formulation is relevant to situation when mutual visibility is needed either to transmit the sensor data being gathered, or to protect the team from hostile persons trying to approach the stationary UGVs.
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| 26. |
- Anisi, David A., 1977-
(författare)
-
On Cooperative Surveillance, Online Trajectory Planning and Observer Based Control
- 2009
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The main body of this thesis consists of six appended papers. In the first two, different cooperative surveillance problems are considered. The second two consider different aspects of the trajectory planning problem, while the last two deal with observer design for mobile robotic and Euler-Lagrange systems respectively.In Papers A and B, a combinatorial optimization based framework to cooperative surveillance missions using multiple Unmanned Ground Vehicles (UGVs) is proposed. In particular, Paper A considers the the Minimum Time UGV Surveillance Problem (MTUSP) while Paper B treats the Connectivity Constrained UGV Surveillance Problem (CUSP). The minimum time formulation is the following. Given a set of surveillance UGVs and a polyhedral area, find waypoint-paths for all UGVs such that every point of the area is visible from a point on a waypoint-path and such that the time for executing the search in parallel is minimized. The connectivity constrained formulation extends the MTUSP by additionally requiring the induced information graph to be kept recurrently connected at the time instants when the UGVs perform the surveillance mission. In these two papers, the NP-hardness of both these problems are shown and decomposition techniques are proposed that allow us to find an approximative solution efficiently in an algorithmic manner.Paper C addresses the problem of designing a real time, high performance trajectory planner for an aerial vehicle that uses information about terrain and enemy threats, to fly low and avoid radar exposure on the way to a given target. The high-level framework augments Receding Horizon Control (RHC) with a graph based terminal cost that captures the global characteristics of the environment. An important issue with RHC is to make sure that the greedy, short term optimization does not lead to long term problems, which in our case boils down to two things: not getting into situations where a collision is unavoidable, and making sure that the destination is actually reached. Hence, the main contribution of this paper is to present a trajectory planner with provable safety and task completion properties. Direct methods for trajectory optimization are traditionally based on a priori temporal discretization and collocation methods. In Paper D, the problem of adaptive node distribution is formulated as a constrained optimization problem, which is to be included in the underlying nonlinear mathematical programming problem. The benefits of utilizing the suggested method for online trajectory optimization are illustrated by a missile guidance example.In Paper E, the problem of active observer design for an important class of non-uniformly observable systems, namely mobile robotic systems, is considered. The set of feasible configurations and the set of output flow equivalent states are defined. It is shown that the inter-relation between these two sets may serve as the basis for design of active observers. The proposed observer design methodology is illustrated by considering a unicycle robot model, equipped with a set of range-measuring sensors. Finally, in Paper F, a geometrically intrinsic observer for Euler-Lagrange systems is defined and analyzed. This observer is a generalization of the observer proposed by Aghannan and Rouchon. Their contractivity result is reproduced and complemented by a proof that the region of contraction is infinitely thin. Moreover, assuming a priori bounds on the velocities, convergence of the observer is shown by means of Lyapunov's direct method in the case of configuration manifolds with constant curvature.
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| 27. |
- Anisi, David A., 1977-
(författare)
-
Online trajectory planning and observer based control
- 2006
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The main body of this thesis consists of four appended papers. The first two consider different aspects of the trajectory planning problem, while the last two deal with observer design for mobile robotic and Euler-Lagrange systems respectively. The first paper addresses the problem of designing a real time, high performance trajectory planner for aerial vehicles. The main contribution is two-fold. Firstly, by augmenting a novel safety maneuver at the end of the planned trajectory, this paper extends previous results by having provable safety properties in a 3D setting. Secondly, assuming initial feasibility, the planning method is shown to have finite time task completion. Moreover, in the second part of the paper, the problem of simultaneous arrival of multiple aerial vehicles is considered. By using a time-scale separation principle, one is able to adopt standard Laplacian control to this consensus problem, which is neither unconstrained, nor first order. Direct methods for trajectory optimization are traditionally based on a priori temporal discretization and collocation methods. In the second paper, the problem of adaptive node distribution is formulated as a constrained optimization problem, which is to be included in the underlying nonlinear mathematical programming problem. The benefits of utilizing the suggested method for online trajectory optimization are illustrated by a missile guidance example. In the third paper, the problem of active observer design for an important class of non-uniformly observable systems, namely mobile robotics systems, is considered. The set of feasible configurations and the set of output flow equivalent states are defined. It is shown that the inter-relation between these two sets may serve as the basis for design of active observers. The proposed observer design methodology is illustrated by considering a unicycle robot model, equipped with a set of range-measuring sensors. Finally, in the fourth paper, a geometrically intrinsic observer for Euler-Lagrange systems is defined and analyzed. This observer is a generalization of the observer recently proposed by Aghannan and Rouchon. Their contractivity result is reproduced and complemented by a proof that the region of contraction is infinitely thin. However, assuming a priori bounds on the velocities, convergence of the observer is shown by means of Lyapunov's direct method in the case of configuration manifolds with constant curvature.
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| 28. |
- Aurell, Alexander, 1989-
(författare)
-
Topics in the mean-field type approach to pedestrian crowd modeling and conventions
- 2019
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis consists of five appended papers, primarily addressingtopics in pedestrian crowd modeling and the formation of conventions.The first paper generalizes a pedestrian crowd model for competingsubcrowds to include nonlocal interactions and an arbitrary (butfinite) number of subcrowds. Each pedestrian is granted a ’personalspace’ and is effected by the presence of other pedestrians within it.The interaction strength may depend on subcrowd affinity. The paperinvestigates the mean-field type game between subcrowds and derivesconditions for the reduction of the game to an optimization problem.The second paper suggest a model for pedestrians with a predeterminedtarget they have to reach. The fixed and non-negotiablefinal target leads us to formulate a model with backward stochasticdifferential equations of mean-field type. Equilibrium in the game betweenthe tagged pedestrians and a surrounding crowd is characterizedwith the stochastic maximum principle. The model is illustrated by anumber of numerical examples.The third paper introduces sticky reflected stochastic differentialequations with boundary diffusion as a means to include walls andobstacles in the mean-field approach to pedestrian crowd modeling.The proposed dynamics allow the pedestrians to move and interactwhile spending time on the boundary. The model only admits a weaksolution, leading to the formulation of a weak optimal control problem.The fourth paper treats two-player finite-horizon mean-field typegames between players whose state trajectories are given by backwardstochastic differential equations of mean-field type. The paper validatesthe stochastic maximum principle for such games. Numericalexperiments illustrate equilibrium behavior and the price of anarchy.The fifth paper treats the formation of conventions in a large populationof agents that repeatedly play a finite two-player game. Theplayers access a history of previously used action profiles and form beliefson how the opposing player will act. A dynamical model wheremore recent interactions are considered to be more important in thebelief-forming process is proposed. Convergence of the history to acollection of minimal CURB blocks and, for a certain class of games,to Nash equilibria is proven.
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| 29. |
- Blom Västberg, Oskar, et al.
(författare)
-
Optimal pedestrian evacuation using Model Predictive Control
- 2013
-
Ingår i: 2013 European Control Conference, ECC 2013. - : IEEE. - 9783033039629 ; , s. 1224-1229
-
Konferensbidrag (refereegranskat)abstract
- During an emergency in a building complex, an effective evacuation is essential to avoid crowd disasters. This article presents a route guiding that minimize the evacuation time during the evacuating of pedestrians from a building.
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| 30. |
- Cao, Yuexin, et al.
(författare)
-
Minimal Control Placement Of Networked Reaction-Diffusion Systems Based On Turing Model
- 2024
-
Ingår i: SIAM Journal of Control and Optimization. - : Society for Industrial & Applied Mathematics (SIAM). - 0363-0129 .- 1095-7138. ; 62:3, s. 1809-1831
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, we consider the problem of placing a minimal number of controls to achieve controllability for a class of networked control systems that are based on the original Turing reaction-diffusion model, which is governed by a set of ordinary differential equations with interactions defined by a ring graph. Turing model considers two morphogens reacting and diffusing over the spatial domain and has been widely accepted as one of the most fundamental models to explain pattern formation in a developing embryo. It is of great importance to understand the mechanism behind the various reaction kinetics that generate such a wide range of patterns. As a first step towards this goal, in this paper we study controllability of Turing model for the case of cells connected as a square grid in which controls can be applied to the boundary cells. We first investigate the minimal control placement problem for the diffusion only system. The eigenvalues of the diffusion matrix are classified by their geometric multiplicity, and the properties of the corresponding eigenspaces are studied. The symmetric control sets are designed to categorize control candidates by symmetry of the network topology. Then the necessary and sufficient condition is provided for placing the minimal control to guarantee controllability for the diffusion system. Furthermore, we show that the necessary condition can be extended to Turing model by a natural expansion of the symmetric control sets. Under certain circumstances, we prove that it is also sufficient to ensure controllability of Turing model.
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| 31. |
- Cao, Yuexin, et al.
(författare)
-
Minimal Control Placement of Turing's Model Using Symmetries
- 2023
-
Ingår i: 2023 62nd IEEE Conference on Decision and Control, CDC 2023. - : Institute of Electrical and Electronics Engineers (IEEE). ; , s. 1456-1461
-
Konferensbidrag (refereegranskat)abstract
- In this paper, the minimal control placement prob-lem for Turing's reaction-diffusion model is studied. Turing's model describes the process of morphogens diffusing and reacting with each other and is considered as one of the most fundamental models to explain pattern formation in a devel-oping embryo. Controlling pattern formation artificially has gained increasing attention in the field of development biology, which motivates us to investigate this problem mathematically. In this work, the two-dimensional Turing's reaction-diffusion model is discretized into square grids. The minimal control placement problem for the diffusion system is investigated first. The symmetric control sets are defined based on the symmetry of the network structure. A necessary condition is provided to guarantee controllability. Under certain circumstances, we prove that this condition is also sufficient. Then we show that the necessary condition can also be applied to the reaction-diffusion system by means of suitable extension of the symmetric control sets. Under similar circumstances, a sufficient condition is given to place the minimal control for the reaction-diffusion system.
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| 32. |
- Cao, Yuexin, et al.
(författare)
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Network Controllability of Turing Reaction and Diffusion Model
- 2022
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Ingår i: 2022 41St Chinese Control Conference (Ccc). - : IEEE. ; , s. 259-264
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Konferensbidrag (refereegranskat)abstract
- In this paper, the controllability problem of the reaction-diffusion (RD) model, or Turing model is studied. Turing model provides a valuable framework for self-organized system and has been widely used to explain to pattern formation in the real life. With the rapidly development of the biology technology, biologists are trying to control the pattern formation artificially and has achieved some progress. However, the influence that exerted on the pattern formation by the external factors, such as light and temperature, remains to be solved. In this work, The RD model is obtained following the assumptions in Turing's original paper and spatially discretized into square grids. The nodes in the outermost layer are considered as candidates for control. Controllability of the RD system with all such nodes as control is first shown. Then controllability of the RD system with minimal number of control nodes is studied. Our results show that nearly 87.5% control nodes can be saved while the system is still controllable. Numerical simulations are provided to demonstrate the effects of controlling the reaction and diffusion of the morphogens.
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| 33. |
- Cedervall, Simon, et al.
(författare)
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Active nonlinear observers for mobile systems
- 2004
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Ingår i: 2004 43RD IEEE CONFERENCE ON DECISION AND CONTROL (CDC), VOLS 1-5. - 0780386825 ; , s. 3898-3902
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Konferensbidrag (refereegranskat)abstract
- For nonlinear systems in general, the observability does not only depend on the initial conditions, but also on the control. This presents an interesting issue: how to design an observer together with the exciting control. In this paper a subproblem in the so called SLAM problem-the relocalization problem is studied, namely, observing the state of a mobile system based on distance sensor readings. An observer is proposed for a car-like robotic system.
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| 34. |
- Cedervall, Simon, et al.
(författare)
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Nonlinear observers for unicycle robots with range sensors
- 2007
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Ingår i: IEEE Transactions on Automatic Control. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9286 .- 1558-2523. ; 52:7, s. 1325-1329
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Tidskriftsartikel (refereegranskat)abstract
- For nonlinear mobile systems equipped with exteroceptive sensors, the observability does not only depend on the initial conditions, but also on the control and the environment. This presents an interesting issue: how to design an observer together with the exciting control. In this note, the problem of designing an observer based on range sensor readings is studied. A design method based on periodic excitations is proposed for unicycle robotic systems.
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| 35. |
- Cheng, Daizhan, et al.
(författare)
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An extension of LaSalle's invariance principle and its application to multi-agent consensus
- 2008
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Ingår i: IEEE Transactions on Automatic Control. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9286 .- 1558-2523. ; 53:7, s. 1765-1770
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Tidskriftsartikel (refereegranskat)abstract
- In the paper, an extension of LaSalle's Invariance Principle to a class of switched linear systems is studied. One of the motivations is the consensus problem in multi-agent systems. Unlike most existing results in which each switching mode in the system needs to be asymptotically stable, this paper allows that the switching modes are only Lyapunov stable. Under certain ergodicity assumptions, an extension of LaSalle's Invariance Principle for global asymptotic stability is obtained. Then it is used to solve the consensus reaching problem of certain multi-agent systems in which each agent is modeled by a double integrator, and the associated interaction graph is switching and is assumed to be only jointly connected.
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| 36. |
- Cheng, D., et al.
(författare)
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Semi-global non-regular linearization of nonlinear systems
- 2004
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Ingår i: 2004 5th Asian Control Conference. - 0780388739 ; , s. 520-526
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Konferensbidrag (refereegranskat)abstract
- In this paper the problem of global or semi-global non-regular static state feedback linearization of affine nonlinear systems is considered. Based on a normal form and a non-regular linearization technique developed recently by authors, this paper first provides a detailed algorithm for the linearization procedure. Then it also presents an easily verifiable condition to estimate the linearizable region, which solves the semi-global linearization problem. An example is included to describe the method and verify the efficiency of the estimation.
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| 37. |
- Cheng, D., et al.
(författare)
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Set stability and controllability for switched non-homogeneous linear systems
- 2007
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Ingår i: 2006 Chinese Control Conference Proceedings, CCC 2006. - : IEEE. - 7810778021 - 9787810778022 ; , s. 2171-2176
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Konferensbidrag (refereegranskat)abstract
- In this paper we consider some control problems of switched non-homogeneous linear systems. First, the set stability of switched non-homogeneous linear systems is considered. It is proved that as the linear parts have a common quadratic Lyapunov function the set stability is assured. The problem of searching smallest attracting set is then considered. Then we assume the switching law is controllable and investigate the controllability condition within the attracting region. Finally, we consider the aggregation and the control of aggregation of flocking behavior. Particularly, the results obtained are implemented to analyzing and manipulating of a group of mobile robots.
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| 38. |
- Cheng, D., et al.
(författare)
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Stabilization of switched linear systems via LaSalle's invariance principle
- 2008
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Konferensbidrag (refereegranskat)abstract
- This paper considers the stability of switched linear systems. Assume a common weak quadratic Lyapunov function exists and the switches satisfy certain ergodic property, we investigate two extensions of LaSalle's invariance principle. Unlike most existing results, the systems we investigated may have switching modes, which are not asymptotically stable. An application to the consensus of multi-agent systems is presented.
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| 39. |
- Deng, Juan, et al.
(författare)
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Coordination of multiple rigid bodies under distance-induced interaction topologies
- 2018
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Ingår i: IET Control Theory & Applications. - : INST ENGINEERING TECHNOLOGY-IET. - 1751-8644 .- 1751-8652. ; 12:15, s. 2067-2075
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Tidskriftsartikel (refereegranskat)abstract
- This study considers the coordination control problem of a group of moving rigid bodies. Each rigid body communicates with other bodies via the distance-induced neighbour graphs. The authors design the distributed control laws for the angular velocity and linear velocity of rigid bodies, and establish sufficient conditions without relying on the dynamical properties of neighbour graphs, to guarantee that the rigid bodies reach the attitude synchronisation and avoid collision with nearby bodies while the communication networks keep connected. Moreover, they introduce a leader into the system to guide all rigid bodies to the desired attitude. Simulation examples are given to illustrate the authors' results.
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| 40. |
- Deng, Juan, et al.
(författare)
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Pose Synchronization of Multiple Rigid Bodies Under Average Dwell Time Condition
- 2018
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Ingår i: Journal of Systems Science and Complexity. - : Springer-Verlag New York. - 1009-6124 .- 1559-7067. ; 31:1, s. 215-233
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Tidskriftsartikel (refereegranskat)abstract
- This paper considers the pose synchronization problem of a group of moving rigid bodies under switching topologies where the dwell time of each topology may has no nonzero lower bound. The authors introduce an average dwell time condition to characterize the length of time intervals in which the graphs are connected. By designing distributed control laws of angular velocity and linear velocity, the closed-loop dynamics of multiple rigid bodies with switching topologies can be converted into a hybrid dynamical system. The authors employ the Lyapunov stability theorem, and show that the pose synchronization can be reached under the average dwell time condition. Moreover, the authors investigate the pose synchronization problem of the leader-following model under a similar average dwell time condition. Simulation examples are given to illustrate the results.
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| 41. |
- Dimarogonas, Dimos, et al.
(författare)
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On the Number of Leaders Needed to Ensure Network Connectivity
- 2008
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Ingår i: 47TH IEEE CONFERENCE ON DECISION AND CONTROL, 2008 (CDC 2008). - : IEEE conference proceedings. - 9781424431243 ; , s. 1797-1802
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Konferensbidrag (refereegranskat)abstract
- In this paper we examine the leader-to-follower ratio needed to maintain connectivity in a leader-follower multi-agent network with proximity based communication topology. In the scenario we consider, only the leaders are aware of the global mission, which is to converge to a known destination point. Thus, the objective of the leaders is to drag the team to the desired goal. In the paper we obtain bounds on the number of leaders needed to complete the task while guaranteeing that connectedness of the communication graph is maintained. The results are first established for an initially complete communication graph and then extended to the incomplete case. The results are illustrated by computer simulations.
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| 42. |
- Dong, Yi, et al.
(författare)
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Coordinated control with multiple dynamic leaders for uncertain Lagrangian systems via self-tuning adaptive distributed observer
- 2017
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Ingår i: International Journal of Robust and Nonlinear Control. - : John Wiley & Sons. - 1049-8923 .- 1099-1239. ; 27:16, s. 2708-2721
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Tidskriftsartikel (refereegranskat)abstract
- This paper studies coordinated control of multiple Lagrangian systems with parametric uncertainties subject to external disturbances by proposing a fully distributed continuous control law based on the improved self-tuning adaptive observer inspired by non-identifier-based high-gain adaptive control technique. Under this distributed continuous control law, a group of Lagrangian systems are driven to the convex hull spanned by multiple heterogenous dynamic leaders, which can be any combination of step signals of arbitrary unknown magnitudes, ramp signals of arbitrary unknown slopes, and sinusoidal signals of arbitrary unknown amplitudes, initial phases, and any unknown frequencies. It is also worth to mention that this control law we propose, depending neither on any information of leader systems for uninformed followers, nor on external disturbances, even independent of neighbors' velocity, can achieve asymptotic tracking of multiple leaders without any additional condition instead of ensuring the ultimate boundedness of the containment error as in the literature.
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| 43. |
- Dong, Yi, et al.
(författare)
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Distributed control of periodic formations for multiple under-actuated autonomous vehicles
- 2017
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Ingår i: IET Control Theory & Applications. - : IET. - 1751-8644 .- 1751-8652. ; 11:1, s. 66-72
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Tidskriftsartikel (refereegranskat)abstract
- One of the unique global behaviours of a group of under-actuated autonomous vehicles is known as cyclic pursue, which requires a group of vehicles to uniformly distribute on circles and at the same time, to orbit around a centre point, while circumnavigation further requires those vehicles to circumnavigate a predefined target of interest. Such behaviours can also be called periodic formations. This paper further studies the periodic formations for multi-agent systems composed of a group of under-actuated autonomous vehicles and a target of interest by proposing a distributed strategy to maintain any required distance between two vehicles and desired angle difference between vehicle's heading and the line of sight that takes directly towards its pursuing vehicle. The authors' distributed control law, dependent only on the information of its pursuing vehicle and itself, can not only enable a network of autonomous vehicles to circulate around a target of interest, but also achieve any physically feasible periodic formations, which include forming regular polygons as a special case.
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| 44. |
- Dong, Yi, et al.
(författare)
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Generalized formation control for unicycles
- 2015
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Ingår i: Chinese Control Conference, CCC. - : IEEE Computer Society. - 9789881563897 ; , s. 7535-7540
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Konferensbidrag (refereegranskat)abstract
- This paper studies formation control of a group of unicycles, and proposes a distributed control law, depending only on the relative position and bearing angle of one nearby vehicle, to realize the circular formation and render more achievable general formations by designing the parameters in the control law. For circular formation, not only we can strictly prove that only two sets of equilibria are asymptotically stable, but also by choosing appropriate control parameters, determine the distances of two vehicles and the radius of the circle that all the unicycles converge to.
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| 45. |
- Dong, Y., et al.
(författare)
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Leader-following formation control problem of unicycles
- 2016
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Ingår i: Proceedings of the 35th Chinese Control Conference 2016. - : IEEE Computer Society. - 9789881563910 ; , s. 8154-8159
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Konferensbidrag (refereegranskat)abstract
- This paper proposes a distributed strategy to solve the leader-following formation problem for multiple under-actuated unicycles. Our distributed control law, dependent on the relative information of its nearest neighbor and itself, can not only enable a network of autonomous mobile agents to circulate around a target of interest, but also achieve any physically feasible formation.
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| 46. |
- Fontan, Angela, et al.
(författare)
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Interval Consensus : a novel class of constrained consensus problems for multiagent networks
- 2017
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Ingår i: 2017 IEEE 56th Annual Conference on Decision and Control, CDC 2017. - : IEEE. - 9781509028733 ; , s. 4155-4160
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Konferensbidrag (refereegranskat)abstract
- In the consensus problem considered in this paper, each agent can impose a lower and an upper bound on the achievable consensus values. We show that if such state constraints are implemented by saturating the value transmitted to the neighboring nodes, the resulting constrained consensus problem must converge to the intersection of the intervals imposed by the individual agents.
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| 47. |
- Fontan, Angela, et al.
(författare)
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Interval Consensus for Multiagent Networks
- 2020
-
Ingår i: IEEE Transactions on Automatic Control. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9286 .- 1558-2523. ; 65:5, s. 1855-1869
-
Tidskriftsartikel (refereegranskat)abstract
- The constrained consensus problem considered in this paper, denoted interval consensus, is characterized by the fact that each agent can impose a lower and upper bound on the achievable consensus value. Such constraints can be encoded in the consensus dynamics by saturating the values that an agent transmits to its neighboring nodes. We show in the paper that when the intersection of the intervals imposed by the agents is nonempty, the resulting constrained consensus problem must converge to a common value inside that intersection. In our algorithm, convergence happens in a fully distributed manner, and without need of sharing any information on the individual constraining intervals. When the intersection of the intervals is an empty set, the intrinsic nonlinearity of the network dynamics raises new challenges in understanding the node state evolution. Using Brouwer fixed-point theorem we prove that in that case there exists at least one equilibrium, and in fact the possible equilibria are locally stable if the constraints are satisfied or dissatisfied at the same time among all nodes. For graphs with sufficient sparsity it is further proven that there is a unique equilibrium that is globally attractive if the constraint intervals are pairwise disjoint.
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| 48. |
- Gao, S., et al.
(författare)
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Extended prescribed performance control with input quantization for nonlinear systems
- 2022
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Ingår i: International Journal of Robust and Nonlinear Control. - : Wiley. - 1049-8923 .- 1099-1239. ; 32:6, s. 3801-3821
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Tidskriftsartikel (refereegranskat)abstract
- For a class of MIMO nonlinear systems, comprised of interconnected subsystems in Brunovsky canonical form, with uncertain yet locally Lipschitz nonlinearities among subsystems and quantized inputs, the target is to form a closed-loop system that exhibits extended prescribed performance on states tracking (accuracy determined by maximum overshoot, minimum convergence rate, maximum steady-state error, and control gains), yet still a low-complexity control structure, without requiring any identification, approximation, and filtering techniques, regardless of uncertainties. In this article, a static, decentralized, continuous, yet computationally inexpensive controller is designed, without requiring parameters of quantizers. Inheriting the merit of pioneering prescribed performance control (PPC) methodology, it is required that the reference signal is (Formula presented.) function only, while, an essential difference and new feature is that, the pioneering PPC guarantees that state tracking errors are constrained by boundary functions (also known as prescribed performance functions, PPFs) only, while, the proposed extend PPC scheme achieves that state tracking errors are constrained by boundary functions and control gains simultaneously, in other words, without “tighter” PPFs, state tracking errors can still be adjusted to arbitrarily small by choosing proper control gains. Finally, comparative simulation results are given to verify the theoretical findings.
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| 49. |
- Gao, Shigen, et al.
(författare)
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Fuzzy adaptive automatic train operation control with protection constraints : A residual nonlinearity approximation-based approach
- 2020
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Ingår i: Engineering applications of artificial intelligence. - : Elsevier BV. - 0952-1976 .- 1873-6769. ; 96
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, we present fuzzy adaptive control based on residual nonlinearity approximation in the presence of protection constraints for the target trajectory tracking problem observed in automatic train operation. Herein, protection constraints refer to a condition wherein the speed and position of a controlled train are not allowed to surpass the boundaries imposed by automatic train protection and moving authority. By defining proper coordinate transformation, the protection constraints are converted to an error-prescribed performance control problem that facilitates operational efficiency by reducing the margin with respect to target trajectories. Based on the prescribed performance control methodology, we present an improved scheme using fuzzy residual nonlinearity approximation and establish the uniformly ultimately boundedness (UUB) property. A novel feature therein is that the ultimate boundary of the proposed scheme is simultaneously characterized by the prescribed performance functions and control parameters, with rigorous and analytically mathematical expressions; while pioneering the prescribed performance control methodology, the ultimate boundary is characterized solely by the prescribed performance functions. To verify the effectiveness and advantages of the proposed scheme, the controllers are applied to the automatic train operation on the Beijing Yizhuang line, which contains 13 operational intervals. Finally, comparative and simulation results are presented to validate the proposed method.
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| 50. |
- Ge, Quanbo, et al.
(författare)
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A Novel Adaptive Kalman Filter Based on Credibility Measure
- 2023
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Ingår i: IEEE-CAA JOURNAL OF AUTOMATICA SINICA. - : Institute of Electrical and Electronics Engineers (IEEE). - 2329-9266. ; 10:1, s. 103-120
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Tidskriftsartikel (refereegranskat)abstract
- It is quite often that the theoretic model used in the Kalman filtering may not be sufficiently accurate for practical applications, due to the fact that the covariances of noises are not exactly known. Our previous work reveals that in such scenario the filter calculated mean square errors (FMSE) and the true mean square errors (TMSE) become inconsistent, while FMSE and TMSE are consistent in the Kalman filter with accurate models. This can lead to low credibility of state estimation regardless of using Kalman filters or adaptive Kalman filters. Obviously, it is important to study the inconsistency issue since it is vital to understand the quantitative influence induced by the inaccurate models. Aiming at this, the concept of credibility is adopted to discuss the inconsistency problem in this paper. In order to formulate the degree of the credibility, a trust factor is constructed based on the FMSE and the TMSE. However, the trust factor can not be directly computed since the TMSE cannot be found for practical applications. Based on the definition of trust factor, the estimation of the trust factor is successfully modifled to online estimation of the TMSE. More importantly, a necessary and sufficient condition is found, which turns out to be the basis for better design of Kalman filters with high performance. Accordingly, beyond trust factor estimation with Sage-Husa technique (TFE-SHT), three novel trust factor estimation methods, which are directly numerical solving method (TFE-DNS), the particle swarm optimization method (PSO) and expectation max-imization-particle swarm optimization method (EM-PSO) are proposed. The analysis and simulation results both show that the proposed TFE-DNS is better than the TFE-SHT for the case of single unknown noise covariance. Meanwhile, the proposed EM-PSO performs completely better than the EM and PSO on the estimation of the credibility degree and state when both noise covariances should be estimated online.
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