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Torii A.,Tokyo Technology | Sivic J.,French Institute for Research in Computer Science and Automation | Pajdla T.,Czech Technical University | Okutomi M.,Tokyo Technology
Proceedings of the IEEE Computer Society Conference on Computer Vision and Pattern Recognition | Year: 2013

Repeated structures such as building facades, fences or road markings often represent a significant challenge for place recognition. Repeated structures are notoriously hard for establishing correspondences using multi-view geometry. Even more importantly, they violate the feature independence assumed in the bag-of-visual-words representation which often leads to over-counting evidence and significant degradation of retrieval performance. In this work we show that repeated structures are not a nuisance but, when appropriately represented, they form an important distinguishing feature for many places. We describe a representation of repeated structures suitable for scalable retrieval. It is based on robust detection of repeated image structures and a simple modification of weights in the bag-of-visual-word model. Place recognition results are shown on datasets of street-level imagery from Pittsburgh and San Francisco demonstrating significant gains in recognition performance compared to the standard bag-of-visual-words baseline and more recently proposed burstiness weighting. © 2013 IEEE.

Wakita K.,Japan Science and Technology Agency | Takami M.,Tokyo Technology | Hosobe H.,Hosei University
IEEE Pacific Visualization Symposium | Year: 2015

The paper tackles the problems of the 'giant hairballs', the dense and tangled structures often resulting from visualization of large social graphs. Proposed is a high-dimensional rotation technique called AGI3D, combined with an ability to filter elements based on social centrality values. AGI3D is targeted for a high-dimensional embedding of a social graph and its projection onto 3D space. It allows the user to rotate the social graph layout in the high-dimensional space by mouse dragging of a vertex. Its high-dimensional rotation effects give the user an illusion that he/she is destructively reshaping the social graph layout but in reality, it assists the user to find a preferred positioning and direction in the high-dimensional space to look at the internal structure of the social graph layout, keeping it unmodified. A prototype implementation of the proposal called Social Viewpoint Finder is tested with about 70 social graphs and this paper reports four of the analysis results. © 2015 IEEE.

Yamamoto K.,Tokyo Technology | Nakamura Y.,University of Tokyo
Proceedings - IEEE International Conference on Robotics and Automation | Year: 2010

Humanoid robots should be able to stand and walk in the presence of external disturbances. This paper addresses the robustness of a humanoid robot to unknown disturbances. Applying the maximal CPI set, it becomes possible to consider the physical constraint explicitly in the COG-ZMP inverted pendulum model control. In our previous research, the convergence speed of COG was improved by applying the switching control based on the maximal CPI set to the stabilization control assuming the contact region is constant. This paper presents updating calculation method of the maximal CPI set when the contact region changes, and the authors propose a falling avoidance control as an application of it. Detecting the stepping necessity based on the maximal CPI set enables to unify the upright position stabilization and stepping motion for falling avoidance. The validity of the proposed method is verified with experiments. ©2010 IEEE.

Okada M.,Tokyo Technology | Takeishi J.,Tokyo Technology
IEEE/RSJ 2010 International Conference on Intelligent Robots and Systems, IROS 2010 - Conference Proceedings | Year: 2010

To prevent the human injury or breakage of the robot caused by interaction or collision with the robot and its environment, it is an important issue to introduce robot softness. However, because not only softness but also stiffness is required for precise task execution, the simultaneous realization of softness and stiffness using time varying stiffness is required in the real environment. We focus on the robot motion, and propose a realization method of time varying stiffness using robot motion and nonlinear passive stiffness. To realize the purpose-designed property of the time dependent stiffness, the nonlinear property of the passive stiffness has to be arbitrary designed considering the robot dynamics. In this paper, we propose the nonlinear property design method of passive stiffness based on kineto-statics with closed kinematic chain. The mechanism is synthesized based on the optimization of the generative force or torque, and purpose-designed stiffness is realized. The proposed method is evaluated by simulations and experiments using the prototype of the landing mechanism. ©2010 IEEE.

Okada M.,Tokyo Technology | Watanabe M.,Tokyo Technology
IEEE/RSJ 2010 International Conference on Intelligent Robots and Systems, IROS 2010 - Conference Proceedings | Year: 2010

Skill or motion transfer from someone to other persons is always required for dance teaching, rehabilitation, sports and so on. For teaching or transfer of motion, a dance notation and display of sequence of motion are often used effectively. However, these contain only the instantaneous postures of motion or professional subjective sense, it is not easy for beginners to understand the dynamical knack of motion. In this paper, we propose "pseudo- reference" that is a virtual target posture in the human motion. The pseudoreference is developed based on the modeling of the human motion by the attractor design method which realizes an autonomous system. By comparing the nonlinear controller with conventional control systems (1DOF and 2DOF control system), the pseudo-reference is obtained as an embodiment of the implicit reference. The proposed method is performed with the inverted pendulum system and the tap dancing robot, and the validity and feasibility for motion transfer of the pseudo-reference are evaluated. ©2010 IEEE.

Yamamoto K.,Tokyo Technology | Okada M.,Tokyo Technology
Proceedings - IEEE International Conference on Robotics and Automation | Year: 2011

In the densely-populated urban areas, pedestrian flows often cross each other and congestion occurs. It may cause discomfort feeling or pedestrian accidents. In order to reduce the congestion or the risk of accidents, it is required to control swarm flows of pedestrian. This paper proposes an implicit control method of the crossing pedestrian flows. Pedestrian flow is modeled with the continuum fluid model and its congestion degree is calculated as the fluid density. From a simulation of the crossing flows with the continuum model, it is verified that diagonal stripe pattern of the congestion degree emerges. Moreover, the authors propose an implicit control method to improve average flow velocity by moving guides. Focusing on periodic phenomenon of the crossing flows, we investigate the relationship between its temporal and spatial frequency and a periodic motion of guides. From this relationship, a control method based on the temporal and spatial frequency is proposed. © 2011 IEEE.

Okada M.,Tokyo Technology | Ando T.,Tokyo Technology
IEEE International Conference on Intelligent Robots and Systems | Year: 2011

It is an important issue to make a disaster reduction plans for overcrowded population in the urban cities. In this paper, we focus on evacuation guidance to prevent the damage from spreading. The personal navigation system cannot deal with evacuation guidance for the human crowd with large numbers of individuals because of time constraints and extraordinary communication error. An implicit guidance based on dynamical characteristic of swarm behavior is efficient and effective with a few guidance operators. We propose a modeling and control method of swarm based on vector field. The evacuee behavior model contains intention of evacuation, field of view, collision avoidance and evacuee group, which are represented by vector field. The guidance operator model contains indicating direction. By giving the desired vector field that indicates the safe route for evacuation, the position of guidance operators are optimally distributed. Moreover, the number of guidance operators is minimized based on the contribution index. The proposed modeling and control method is applied to the swarm robot and the effectiveness is evaluated by the experiments. © 2011 IEEE.

Okada M.,Tokyo Technology | Miyazaki T.,Tokyo Technology
IEEE International Conference on Intelligent Robots and Systems | Year: 2013

This paper proposes an off-line periodic motion pattern design method using dimensional reduction. A human periodic motion is measured by a motion capture system, and it is projected onto a low dimensional space based on principal component analysis. The low dimensional motion pattern is modified, so that the high dimensional motion pattern satisfies the motion conditions, dynamical consistency and joint angle and torque limitations. The proposed method is applied to the motion pattern design of the planar bipedal robot. The moon-walk performed by a human is transformed to the robot motion. In this case, the motion conditions are the kinematic closed loop condition and the ground contact states of foot links. The floor reaction force condition and the satisfaction of the motion equation are given for dynamical consistency. © 2013 IEEE.

Yamamoto K.,EcoTopia Science Institute | Okada M.,Tokyo Technology
Proceedings of the SICE Annual Conference | Year: 2013

There are a lot of pedestrian flows in the commercial facility. These flows often cross each other, and change goals, e.g. reception desk or ticket-vending machine. Moreover, too long people queue at a goal sometimes blocks up other flows and makes us uncomfortable. In order to reduce the congestion and realize the amenity space the environmental design considering the swarm behavior of people is required. In this paper, the authors focus on the formation control of people queue at a goal and propose the formation control method by optimizing the layout of movable partitions. The effectiveness of the proposed method is verified with simulations.

Okada M.,Tokyo Technology | Takeda Y.,Tokyo Technology
Proceedings - IEEE International Conference on Robotics and Automation | Year: 2012

In this paper, we develop a design method of nonlinear profile of gear ratio to utilize a DC servo motor effectively for a jumping robot. Because the larger ground force yields the higher kinetic energy of the robot body, the optimal gear ratio is obtained by the maximization of the ground force from statics point of view. Moreover, the varying gear ratio during the jump motion is obtained through a simulation which connects statics-based optimization and robot dynamics. A non-circular gear is synthesized which realizes the obtained optimal varying gear ratio. The effectiveness of the proposed method is evaluated by simulations. © 2012 IEEE.

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