Shuichiro Hashi

Numerical Study on the Improvement of Detection Accuracy for a Wireless Motion Capture System

A detection technique having an accuracy of better than 1 mm is required for body motion analysis in the field of medical treatment. A wireless magnetic motion capture system is one such effective detection technique. We propose a candidate system using an LC resonant magnetic marker (LC marker). Previous studies have showed that the system is capable of repeatable position detection accuracy of better than 1 mm if the system has an adequate signal-to-noise (S/N ratio). However, there are some cases in which the detection results include unignorable errors because some approximations, e.g. a magnetic dipole assumption of the LC marker, are applied to solve the inverse problem to determine the position and orientation of the LC marker. Therefore, a numerical analysis is employed to realize a motion capture system having a high detection accuracy. To elucidate the problem of detection error, the influence of variations in the sizes of the LC marker and the pick-up coil are considered in the numerical simulation. After studying the analysis, the main cause of detection error is determined to be the size of the pick-up coil rather than the size of the LC marker. It was also is found that a pick-up coil measuring 10 mm in diameter with a wound coil width of 1 mm achieves a detection accuracy of better than 0.1 mm.

A large thermal elasticity of the ordered FeRh alloy film with sharp magnetic transition

Thermal elasticity and electrical resistivity with the magnetic phase transition were studied in FeRh alloy films prepared by ion-beam sputtering and subjected to post-annealing. Fe/sub 49.7/Rh/sub 50.3/ and Fe/sub 48.9/Rh/sub 51.1/ films deposited on conventional glass substrate and subjected to post-annealing at 600/spl deg/C for 90 min, respectively. Both films show a considerably sharp transition. In particular, Fe/sub 49.7/Rh/sub 50.3/ film exhibits small thermal hysteresis of about 20/spl deg/C width, which is only about 2 times over than that of bulk. Furthermore, a large abrupt thermal strain over 2/spl times/10/sup -3/ was observed with the magnetic transition. These results indicate that strictly controlled an equiatomic composition is an effective way to obtain the FeRh film with abrupt magnetic phase transition under low temperature and short time annealing.

Methodology of Dynamic Actuation for Flexible Magnetic Actuator and Biomimetic Robotics Application

Recently, materials and locomotion control methods of micro robot have been developed for applying to the biomedical application. Especially, many researches of biomimetics locomotion and magnetic actuators have been introduced. In this paper, we introduced methodology of dynamic actuation of the flexible magnetic actuator so as to drive micro robot. Proposed methodology presents both static motion and dynamic motion by correlation between the magnetic moment and the rotating magnetic field. This method can provide much more active movement than the general control method of ac and dc magnetic field. Various actuations of the flexible magnetic actuator are applied to new swimming method of fish-like micro robot and locomotion of inchworm-like micro robot. Also, the flexible magnetic actuator based the micro robots have not only advantage of the dynamic actuation but also advantage of wireless control and no inserted battery.

Magnetic fish-robot based on multi-motion control of a flexible magnetic actuator.

This paper presents a biologically inspired fish-robot driven by a single flexible magnetic actuator with a rotating magnetic field in a three-axis Helmholtz coil. Generally, magnetic fish-robots are powered by alternating and gradient magnetic fields, which provide a single motion such as bending the fish-robots fins. On the other hand, a flexible magnetic actuator driven by an external rotating magnetic field can create several gaits such as the bending vibration, the twisting vibration, and their combination. Most magnetic fish-like micro-robots do not have pectoral fins on the side and are simply propelled by the tail fin. The proposed robot can swim and perform a variety of maneuvers with the addition of pectoral fins and control of the magnetic torque direction. In this paper, we find that the robots dynamic actuation correlates with the magnetic actuator and the rotating magnetic field. The proposed robot is also equipped with new features, such as a total of six degrees of freedom, a new control method that stabilizes posture, three-dimensional swimming, a new velocity control, and new turning abilities.

Development of real-time and highly accurate wireless motion capture system utilizing soft magnetic core

Highly accurate wireless motion capture system using LC resonant magnetic marker has been developed. The marker consists of soft magnetic core with wound coil and a chip capacitor without battery or electric wires, driven wirelessly by the action of electromagnetic induction. The system realized the position accuracy is less than 1 mm within the space of 150 mm from the pickup coil array. Compared with dc magnetic system, the proposed system is applicable for precision motion-capturing under optically isolated space without magnetic shielding because the system is not influenced very much by the earth field noise.

Study of Strain Sensor Using FeSiB Magnetostrictive Thin Film

We examined the strain sensor using the inverse magnetostriction effect to obtain high sensitivity. Since the sensor is composed of a conductive layer sandwiched between two magnetostrictive films, the impedance of the sensor is low compared with the former works. Therefore, sensitivity of the sensor can be significantly improved due to the increase of the impedance change ratio. The sensor using molybdenum as the conductive layer exhibited higher sensitivity with a large impedance change ratio caused by the anisotropy induced to the width direction of the magnetostrictive films. In this study, for the sensor sample whose size is 0.5 mm in width and 2 ¿m in thickness, we could obtain the highest sensitivity of 18 000.

Wireless Magnetic Motion Capture System—Compensatory Tracking of Positional Error Caused by Mutual Inductance

A wireless magnetic motion capture system using an LC resonant magnetic marker was developed and has been studied. The positional error of the system caused by mutual inductance between the exciting coil and the LC marker was examined. It has been found that the impedance change of the exciting coil due to a resonance of the LC marker perturbs the strength of the magnetic field which is used for marker excitation. The more a marker approaches the exciting coil, the larger it becomes. This fluctuation induces an error in the marker signal which is measured by the pickup coils and is necessary for positional calculation. Then, the compensatory process in consideration of the mutual inductance has been employed for positional calculation in order to improve the positional accuracy. From the compensation, the absolute positional accuracy is less than 2 mm within 140 mm of the pickup coil array

Wireless Magnetic Motion Capture System for Multi-Marker Detection

A wireless multi-motion capture system using five LC resonant magnetic markers has been developed and is demonstrated. Each marker has an individual resonant frequency, 157, 201, 273, 323, and 440 kHz, respectively. A new measuring technique is applied in order to reduce the acquisition time. In this new technique the markers are excited by a superposed wave corresponding to the all resonant frequencies, while the voltage signals induced through pick-up coils are separated in a frequency spectrum by FFT analysis. Regardless of the number of markers, the voltage amplitude for each resonant frequency can be easily obtained simultaneously and thus the proposed system can detect multiple markers. The positional accuracy for five markers is less than 2 mm within 100 mm of the pick-up coil array

IM6D: magnetic tracking system with 6-DOF passive markers for dexterous 3D interaction and motion

We propose IM6D, a novel real-time magnetic motion-tracking system using multiple identifiable, tiny, lightweight, wireless and occlusion-free markers. It provides reasonable accuracy and update rates and an appropriate working space for dexterous 3D interaction. Our system follows a novel electromagnetic induction principle to externally excite wireless LC coils and uses an externally located pickup coil array to track each of the LC coils with 5-DOF. We apply this principle to design a practical motion-tracking system using multiple markers with 6-DOF and to achieve reliable tracking with reasonable speed. We also solved the principles inherent dead-angle problem. Based on this method, we simulated the configuration of parameters for designing a system with scalability for dexterous 3D motion. We implemented an actual system and applied a parallel computation structure to increase the tracking speed. We also built some examples to show how well our system works for actual situations.

Hybrid magnetic mechanism for active locomotion based on inchworm motion

Magnetic robots have been studied in the past. Insect-type micro-robots are used in various biomedical applications; researchers have developed inchworm micro-robots for endoscopic use. A biological inchworm has a looping locomotion gait. However, most inchworm micro-robots depend on a general bending, or bellows, motion. In this paper, we introduce a new robotic mechanism using magnetic force and torque control in a rotating magnetic field for a looping gait. The proposed robot is controlled by the magnetic torque, attractive force, and body mechanisms (two stoppers, flexible body, and different frictional legs). The magnetic torque generates a general bending motion. In addition, the attractive force and body mechanisms produce the robot?s looping motion within a rotating magnetic field and without the use of an algorithm for field control. We verified the device?s performance and analyzed the motion through simulations and various experiments. The robot mechanism can be applied to active locomotion for various medical robots, such as wireless endoscopes.