Natsuki Miyata

Modeling deformable human hands from medical images

This paper presents a new method for constructing an example-based deformable human hand model from medical images. Realistic animation of human hands requires good estimates of the joint structure and properly weighted skeleton-driven surface deformation. For this purpose, we propose a method based on medical images of hands in several poses. Our method consists of the following 3 steps: First, using the measured bone shapes, we estimate the link structure (joint rotation centers) and the joint angles of each scan. Second, we construct a mutually consistent polygonal mesh of all the scans. For this purpose, a polygonal mesh of one pose, the base mesh, is deformed using skeletal subspace deformation, and then fitted interactively to the measured meshes from the other scans. Finally, the hand is deformed using a weighted pose space deformation. We demonstrate results of deformable hand models consisting of 100,000 triangle meshes derived from CT scans.

Cooperative transport by multiple mobile robots in unknown static environments associated with real-time task assignment

This paper deals with a task-assignment architecture for cooperative transport by multiple mobile robots in an unknown static environment. The architecture should satisfy three features: deal with a variety of tasks in time and space, deal with a large number of tasks compared with the number of robots, and decide the behavior in real time. The authors propose the following approach: we consider the unit of task (task instance) as the job that should be done in a short time by one robot. Based on the environmental information, task instances are dynamically generated using task templates. The priority of task instances is evaluated dynamically based on the number of robots and the configuration in the workspace. In addition, we avoid generating too many task instances by suppressing object motion. The main part of the architecture consists of two real-time planners: a priority-based task-assignment planner solved by using the linear programming method, and motion planners based on short-time estimation. The effectiveness of the proposed architecture is verified by a cooperative transport simulation in an unknown environment.

Virtual humanoid robot platform to develop controllers of real humanoid robots without porting

This paper presents a virtual humanoid robot platform (V-HRP for short) on which we can develop the identical controller for a virtual humanoid robot and its real counterpart. The unification of the controllers for the virtual and real robot has been realized by introducing software adapters for two robots respectively and employing ART-Linux on which real-time processing is available at the user level. Thanks to the unification, the controllers can share softwares with the dynamics simulator of V-HRP, including the parameter parser, kinematics and dynamics computations and the collision detector. This feature can make the development of the controllers more efficient and the developed controllers more reliable.

Transferring and regrasping a large object by cooperation of multiple mobile robots

This paper deals with a motion planning of mobile robots during transferring a large object cooperatively by a group of multiple mobile robots (a robot group). This problem has the following characteristics: 1) a real time planning is essential because mobile robots move in an open and dynamic area in comparison to articulated robots; 2) both the object and the robot group need to avoid collision against obstacles; and 3) the object needs to be grasped stably by the robot group. The authors propose the following approach to solve this complicated problem: 1) regrasping strategy of the object is introduced in order avoid obstacles and to transfer the object stably; and 2) the motion planning is divided into two steps: the object and that of the robot group. The former step is accomplished by extending the virtual impedance method, which was proposed by authors. The latter step is realized by using nonlinear programming method, that optimizes a penalty index indicating the performance for obstacle avoidance and for stable grasping. Effectiveness of the proposed method is verified by a simulation of transferring a large circle-shaped object with three robots.

Modeling of human hand link structure from optical motion capture data

This paper proposes the total protocol to determine the link structure of a human hand using optical motion capture data. The difficulty in capturing hand motion comes from the hands relatively high degrees of freedom located in very small space. To deal with the problem caused by closeness between markers, the number of markers is reduced. The effect of reduced markers is compensated by simplifying the problem. The adverse effect of skin movement and the limited range of movement is avoided by regulating the calibration motion appropriately. A link estimation experiment is performed to show the effectiveness of the proposed method.

Measurement and comparison of humanoid H7 walking with human being

Abstract This paper describes our research efforts aimed at understanding human being walking functions. Using a motion-capture system, force plates and distributed force sensors, walk motion of both human being and humanoid H7 was captured. Experimental results are shown. Comparisons in between human being and H7 walk made using the following characteristics: (1) ZMP trajectories; (2) torso movement; (3) free leg trajectories; (4) joint angle usage; (5) joint torque usage. Furthermore, implications of the comparisons to the humanoid robot are discussed.

Cooperative transport system with regrasping car-like mobile robots

This paper deals with motion planning of cooperative transfer with regrasping by a group of car-like mobile robots. In order to realize this transfer task by actual car-like robots, three aspects should be considered: the nonholonomic characteristic of car-like robots, how to control the force and avoid too large a force by position-controlled robots, and control cycle of the system. Based on algorithms from previous works, the authors propose the following approach: 1) designing robot hand mechanism; 2) constructing hybrid planning architecture composed of centralized and decentralized system including an object motion observer. A simple transport experiment by an actual robot system is made to show the effectiveness of this mechanism. Validity of the proposed method is verified by a transport simulation.

An Analysis of Hand Measurements for Obtaining Representative Japanese Hand Models

In order to create digital models representing the variation in hands of adult Japanese, 82 measurements were taken for 103 subjects using traditional methods. Factor analysis of the measurements was performed, and the first 2 factors were used to calculate measurements for 9 members of the boundary family. A 3D digital model was created for each family member by deforming a generic model by minimizing the total difference of 40 measurements between the generic model and the target hand model. The generic model with 36 degrees of freedom was created from medical images of a subject captured in 4 different posture.

Finger joint kinematics from MR images

Accurate and quantitative analysis of human hand motion requires an understanding of the kinematics of the proximal and distal interphalangeal joints in three dimensions. This paper presents a technique to investigate in-vivo finger joint kinematics using magnetic resonance (MR) imaging. Bone surface models were extracted from MR images of the right hand of ten healthy subjects in four different postures. The relative motion of adjacent bones for all subjects was calculated and expressed as the helical axis and the angles around the axes of local bone coordinate system. The motion data indicated the change of axis orientation with flexion. After carefully selecting the subject and a pose with an appropriate flexional angle, studies determined that the mean inclination between the axes of the proximal and distal interphalangeal joints was approximately 14 [deg].

Optimization-Based Grasp Posture Generation Method of Digital Hand for Virtual Ergonomics Assessment

Automatically generating humanlike grasp postures of the digital hand is a key issue for the virtual ergonomic assessment of the industrial products. In this paper we propose a new optimization-based approach for generating the realistic grasp posture. As an objective function, we use the number of the contact points, the fit of the specific part of the hand surface for the feature edges of the product surface and the margin for the constraints on the joint angle limits of the figures. The experimental studies on the grasp posture generation for the digital camera indicate that more realistic grasp posture could be generated using the proposed optimization-based method than the one using our former method.