Michihiko Koseki

Group robots forming a mechanical structure-development of slide motion mechanism and estimation of energy consumption of the structural formation

This study deals with group robots forming a mechanical structure. The group robots consist of identical cellular robots with same mechanical structure and information processing. To realize the group robots in hardware, we propose a slide motion mechanism that supports a large mechanical loading. We report the performance test, and energy consumption required for transformation of the cellular robot under various configurations. This paper also discusses the shortest route with minimum energy in transformation when an initial configuration and a final one are given.

Development of pneumatic cellular robots forming a mechanical structure

This study deals with group robots forming a mechanical structure. In this paper, we address the concrete motion mechanisms of the robots. Each robot has a cubic shape with pneumatic actuators. It rotates with a corner of the robot as an axis. To realize the movement, we propose two kinds of mechanical devices. One is a stabilization mechanism that the pneumatic actuator stably forms an arched shape. The other one is a rotary selective valve for minimizing pneumatic elements. This paper also reports a demonstration of the pneumatic robots in hardware.

Flexible Hermetically-Sealed Mobile Robot for Narrow Spaces Using Hydrostatic Skeleton Driving Mechanism

Almost all of conventional mobile robots for narrow spaces exploration, e.g. rescue robots, adopt crawler or wheel mechanisms. However, in narrow spaces, such robot is often stuck because the robot body is sandwiched between both sides of a terrain. Especially, with normal crawler or wheel mechanisms, it is impossible to penetrate into narrow spaces lower than the height of the robot. In addition, sealing bushes of drive shaft cause unignorable energy loss because of rotational resistances. In order to solve these problems, this study proposes an innovative flexible robot with new hydrostatic skeleton driving mechanism. The main components of the robot are a hermetically-sealed outer cover with looped structure and flexible crawlers with hydrostatic skeleton named HS crawlers. This new robot provides remarkable advantages in narrow spaces as listed below: i) The robot can change its shape adapting to terrain; ii) All ground contact areas of the robot are driven toward the same direction. Thus, the robot is able to penetrate into narrow spaces changing its shape even if the terrain is rather narrower than the size of the robot. This paper describes the mechanisms of the robot and the detail of the HS crawler. Driving force of the HS crawler is discussed with comparison of simulation and experiment. Performance of first prototype robot is verified by experiments of wireless driving and passing narrow space. The prototype robot could pass through a space of 300 mm height, whereas the ordinary height of the robot is 420 mm

Cellular Robots Forming a Mechanical Structure

This paper deals with group robots called CHOBIE that cooperatively transform a mechanical structure. The CHOBIE have slide motion mechanisms with some mechanical constraints for large stiffness even in movement. First of all, a way of structural transformation including the mechanical constraints is discussed. Second, dissipative energy in the structural transformation based on experimental data of the CHOBIE is estimated. Third, for autonomy of the robots, CHOBIE II is developed and the performance test is demonstrated.

Reconfigurable group robots adaptively transforming a mechanical structure - Crawl motion and adaptive transformation with new algorithms

This paper describes group robots adaptively construct a mechanical structure. The feature of the robots is high rigidity by adopting sliding mechanisms. This study discusses algorithms of crawl motion and adaptive construction considering mechanical constraints of the robots. The proposed algorithm is based on local communication of the robots. We introduce a scheme of a temporary leader which is autonomously specified by form of the structure. The scheme decreases amount of information in communication between the robots. The experimental demonstrations are also shown in this paper

A new metal artifact reduction algorithm based on a deteriorated CT image.

BACKGROUND Computed tomography (CT) is an established imaging technology primarily used as a non-invasive diagnostic tool that reconstructs axial images. However, significant problems with metal artifacts remain. A metal artifact is a strong radial noise in an image, which makes it difficult to diagnose patients and inspect products containing metal implants. Historically, studies related to metal artifact reduction used projection data, though the data is not typically saved after processing. OBJECTIVE This study proposes a new metal artifact reduction algorithm that does not require projection data, for new applications and for accurate diagnostic techniques. METHODS The algorithm utilizes reconstructed images and is based on iterative reconstruction. By reproducing an accurate forward projection on simulation and combining it with an iterative calculation, discrepancies causing metal artifacts are eliminated. RESULTS Validation was completed with numerical phantom models. Our results indicate that the proposed algorithm effectively reduces metal artifacts, even if numerous complex-shaped metal pieces were embedded in the cross-section. CONCLUSIONS We developed a novel reconstruction algorithm for metal artifact reduction in CT imaging that only requires reconstructed images and projection conditions. Any historical CT data containing metal artifacts could be improved with this method.

Three-dimensional Display System of Individual Mandibular Movement

It is expected to develop an intelligible diagnostic system of temporomandibular disorders (TMD) for both medical doctors and patients. This study proposes a display system that visualizes motion of the human mandible. The system integrates two engineering methods. One is an optical motion capture technique for measuring the mandibular movements. The other is an individual modeling method based on the X-ray CT data. It is important to know exact mandibular movements for the proper diagnosis. This paper discusses experimental verification of the total performance of the system using a device of hinge movement. The verification clearly shows that precision of the model has a great effect on accuracy of the movements. The total performance of the system is achieved within an accuracy of 0.2mm at the hinge of the device. The system provides not only three-dimensional visual information of the mandibular movements as animations but also quantitative information of position, velocity and acceleration at an arbitral point of the model. The system will be useful for informed consent in medical treatments of TMD.

Patient Specific Finite Element Modeling of a Human Skull

This paper presents automated finite element modeling method and application to a biomechanical study. The modeling method produces a finite element model based on the multi-sliced image data adaptively controlling the element size according to complexity of local bony shape. The method realizes a compact and precise finite element model with a desired total number of nodal points. This paper challenges to apply this method to a human skull because of its intricate structure. To accomplish the application of the human skull, we analyze characteristics of bony shape for a mandible and a skull. Using the analytical results, we demonstrate that the proposed modeling method successfully generates a precise finite element model of the skull with fine structures.

Estimation Of Masticatory Forces ForPatient-specific Analysis Of The Human Mandible

This paper proposes an estimation method of the masticatory forces using an objective function composed of three criteria: efficiency of muscular activities, moment balance between muscular and biting forces, and reaction forces at condyles. The method is applied to a patient whose jaw has a severe deformity, and the influence of the criteria is examined. The muscular forces of the numerical result with the consideration of the all three criteria well agree to the analysis of EMG signals. Individual stress analysis under the estimated mechanical condition is also performed. There is no stress concentration and little difference in stress distribution on both left and right sides in spite of the asymmetrical mandibular shape and masticatory condition. The numerical result suggests mechanical adaptation of mandible by the masticatory forces.

Pedicle Screw Loosening after Posterior Spinal Fusion for Adolescent Idiopathic Scoliosis in Upper and Lower Instrumented Vertebrae Having Major Perforation

Study Design. A retrospective chart review. Objective. The aim of this study was to investigate the incidence and characteristics of screw loosening in surgically treated adolescent idiopathic scoliosis (AIS) patients. Summary of Background Data. Pedicle screws are widely used in posterior spinal fusion for AIS, although postoperative loosening can occur. However, few reports exist on screw loosening after pedicle screw fixation in young scoliosis patients and the etiology of loosening is not well known. Methods. One hundred twenty AIS patients (9 males, 111 females; mean age: 15.0 years) who had received pedicle screw fixation were retrospectively reviewed. All patients underwent routine computed tomography (CT) reconstruction scans at 6 months postoperatively to assess screw position, bony fusion, and the presence of screw loosening. The perforation status of each pedicle screw was assigned a grade of 0 to 3 using Rao classification. Results. Forty-three of 1624 (2.6%) screws showed evidence of loosening on CT. Screw loosening rates according to vertebral insertion level were upper instrumented vertebra (UIV): 9.6%; lower instrumented vertebra (LIV): 5.4%; one vertebra below the UIV: 1.8%; one vertebra above the LIV: 0.5%; two vertebrae below the UIV: 1.2%; and three vertebrae below the UIV: 0.9%. Screw loosening rates based on screw perforation grade were Grade 0: 1.4%; Grade 1: 3.1%; Grade 2: 15.5%; and Grade 3: 15.2%. Multivariate analysis revealed a distance from the UIV or LIV of one vertebra as well as the presence of major perforation to be independent factors affecting screw loosening. The odds ratios (ORs) of UIV/LIV insertion and major perforation were 73.4 and 17.2, respectively. When major perforations occurred in the UIV or LIV, the OR for loosening approached 1262. Conclusion. Pedicle screw loosening after posterior spinal fusion in AIS patients tend to occur in the UIV or LIV. Major screw perforation is also significantly associated with screw loosening. The risk of loosening becomes compounded when major perforations are present in the UIV or LIV. Level of Evidence: 4