A multi-terminal lateral spin valve consisting of three ferromagnetic nanopillars on a Cu/Nb bilayer has been fabricated. We investigated the influence of the spin injection on the superconducting ...properties at the Cu/Nb interface. The non-local spin valve signal exhibits a clear spin insulation signature due to the superconducting gap of the Nb. The magnitude of the spin signal is found to show the probe configuration dependence. From the careful analysis of the bias current dependence, we found the suppression of the superconductivity due to the exchange interaction between the Cooper pair and accumulated spin plays an important role in the multi-terminal spin injections. We also discuss about the possibility of the Cooper-pair formation due to the spin injection from the two injectors with the anti-parallel alignment.
This paper discusses velocity measurement for motor drives with optical encoders. Although many methods on velocity measurement have been proposed, accurate measurement was not achieved in a ...high-speed range. This paper therefore proposes synchronous-measurement method (S method) that measures the velocity synchronized with the alteration of pulse numbers in each sampling period. Accurate velocity measurement is achieved in all speed ranges with this method. Furthermore, other velocity prediction methods are applicable in addition to the method. Simulation and experimental results verify the validity of the proposed method.
Almost 2 million Japanese citizens use Navitime, a mobile phone-based navigation service that incorporates various modes of transportation. User experiences reveal implications for designing ...urban-computing services. Location-based services are a key pervasive computing application that could deeply influence urban spaces and their inhabitants. Recent advances in mobile phones, GPS, and wireless networking infrastructures are making it possible to implement and operate large-scale location- based services in the real world.
Motion control for advanced mechatronics Ohnishi, K.; Shibata, M.; Murakami, T.
IEEE/ASME transactions on mechatronics,
03/1996, Letnik:
1, Številka:
1
Journal Article
Recenzirano
Motion control is now recognized as a key technology in mechatronics. The robustness of motion control will be represented as a function of stiffness and a basis for practical realization. Target of ...motion is parameterized by control stiffness which could be variable according to the task reference. However, the system robustness of motion always requires very high stiffness in the controller. The paper shows that control of acceleration realizes specified motion simultaneously with keeping the robustness very high. The acceleration is a bridge to connect such robustness and variable stiffness. For practical applications, a technique to estimate disturbance is introduced to make motion controller to be an acceleration controller. Motion control of flexible structure and identification of mechanical parameters are also described.
In this paper, a method that makes biped robots track zero-moment-point (ZMP) reference trajectories is proposed. The biped robots have flat rectangular soles with force sensors at each corner. The ...sensors detect reaction force from the ground. Sensor information is transformed into useful structure, which is defined as ldquoenvironmental modes.rdquo The environmental modes represent contact states between the ground and the soles and are extracted by the information of four force sensors at each corner of the rectangular soles. The environmental modes consist of the following four modes: 1) heaving; 2) rolling; 3) pitching; and 4) twisting. These modes are related to the ZMP, by which walking stability is evaluated. Therefore, command values of the environmental modes can be derived by the ZMP reference trajectory. By tracking the command values, the walking motion becomes more stable. The conventional study on controlling the environmental modes takes only the rolling and pitching modes into account. However, it is not sufficient to stabilize the walking motion, because the heaving mode has been neglected. The heaving mode is also very important to stabilize the walking motion. Therefore, in this paper, we extend the conventional method for considering the heaving mode to track the ZMP reference trajectory. Validity of the proposed method was confirmed by experimental results.
In this paper, an intelligent wheelchair robot for adaptation to an unknown environment is developed. Environmental information is a key factor to comply to an unknown and/or unstructured ...environment. Since the environment has an infinite number of modes, the environmental information should be classified into some modes. This paper develops a novel viewpoint of robot motion control based on quarry of environmental information. The robot adapts to the environment based on the remote and contact information. In order to adapt to the remote environment, the obstacle avoidance problem is treated. This kind of robot motion control is based on position control. On the contrary, in order to adapt to the contact information, compliance control is applied to a robot. If the robot collides with the obstacles, the impact force is relaxed by the method, and safety is improved. This controller, on the other hand, is based on force control. In this paper, position control and force control are integrated in the acceleration dimension based on acceleration control. The robust acceleration control is attained by the disturbance observer. Finally, a semiautonomous function is installed for the improvement of human operationality. The numerical and experimental results show viability of the proposed method
We describe observations carried out by the MOA group of the Galactic bulge during 2000 that were designed to detect efficiently gravitational microlensing of faint stars in which the magnification ...is high and/or of short duration. These events are particularly useful for studies of extrasolar planets and faint stars. Approximately 17 deg2 were monitored at a sampling rate of up to six times per night. The images were analysed in real time using a difference imaging technique. 20 microlensing candidates were detected, of which eight were alerted to the microlensing community whilst in progress. Approximately half of the candidates had high magnifications (≳10), at least one had very high magnification (≳50), and one exhibited a clear parallax effect. The details of these events are reported here, together with details of the on-line difference imaging technique. Some nova-like events were also observed and these are described, together with one asteroid.
We report the detection of the cool, Jovian-mass planet MOA-2007-BLG-400Lb. The planet was detected in a high-magnification microlensing event (with peak magnification A max = 628) in which the ...primary lens transited the source, resulting in a dramatic smoothing of the peak of the event. The angular extent of the region of perturbation due to the planet is significantly smaller than the angular size of the source, and as a result the planetary signature is also smoothed out by the finite source size. Thus, the deviation from a single-lens fit is broad and relatively weak (approximately few percent). Nevertheless, we demonstrate that the planetary nature of the deviation can be unambiguously ascertained from the gross features of the residuals, and detailed analysis yields a fairly precise planet/star mass ratio of , in accord with the large significance () of the detection. The planet/star projected separation is subject to a strong close/wide degeneracy, leading to two indistinguishable solutions that differ in separation by a factor of ~8.5. Upper limits on flux from the lens constrain its mass to be M < 0.75 M (assuming that it is a main-sequence star). A Bayesian analysis that includes all available observational constraints indicates a primary in the Galactic bulge with a mass of ~0.2-0.5 M and thus a planet mass of ~0.5-1.3 M Jup. The separation and equilibrium temperature are ~5.3-9.7 AU (~0.6-1.1 AU) and ~34 K (~103 K) for the wide (close) solution. If the primary is a main-sequence star, follow-up observations would enable the detection of its light and so a measurement of its mass and distance.
This paper presents a framework of hand-eye relation for visual servoing with more precision, mobility, and global view. Mainly, there are two types of camera utilization for visual servoing: ...eye-in-hand and eye-to-hand configurations. Both have own merits and drawbacks regarding to precision and view limit that oppose each other. Based on both behaviors, this paper employs a mobile manipulator as the second robot to hold the camera. Here, the camera architecture is eye-to-hand configuration for the main robot, but mainly behaves as eye-in-hand configuration for the second robot. Having this framework, the drawback of each configuration is resolved by the benefit of the other. Here, the camera becomes mobile with more precision and global view. In addition, since there is no additional camera, the vision algorithm can be kept simple. In order to gain real-time visual servoing, this paper also addresses real-time constraints on vision system and data communication between robot and vision. Here, a hexagon pattern of artificial marker with a simplified image processing is developed. A grasp positioning problem is considered with position-based dynamic look and move visual control through object pose estimation. The system performance is validated by the experimental result.
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