 |
 |
 |
 |
 |
| Top | Research | Publications | Bio Sketch | Link |
|
|
|
|
|
| Top | Research | Publications | Bio Sketch | Link |
Research Topics
| Legged motion control | Multiple robots | ||
 |
 |
||
| Vision system | Space robots and Manipulator | ||
 |
 |
||
Dynamically stable gaits for quadruped walking vehicles
To realize dynamically stable walking for a quadruped walking robot, the combination of the trajectory planning of the body and leg position (feedforward control) and the adaptive control using sensory information (feedback control) is indispensable. We propose a new body trajectory named the 3D sway compensation trajectory for a stable trot gait. This trajectory has a lower energy consumption than the conventional sway trajectory that we have proposed. In addition, for the adaptive attitude control method during the 2-leg supporting phase, we propose the use of rotation of body along the diagonal line between supporting feet and vertical swing motion of recovering legs.
| Recovering leg's motion | Stabilization of unsymmetrical trot gait |
 |
 |
Papers
Energy Efficiency for quadruped walking vehicles
Though a legged robot has high terrain adaptability as compared with a wheeled vehicle, its moving speed is considerably low in general. For attaining a high moving speed with a legged robot, a dynamically stable gait,such as running for a biped robot and a trot gait or a bound gait for a quadruped robot, is a promising solution. However, the energy efficiency of the dynamically stable gait is generally lower than the efficiency of the stable gait such as a crawl gait.
We are conducting an experimental study on the energy efficiency of a quadruped walking vehicle. Energy consumption of two walking patterns for a trot gait is investigated through experiments using a quadruped walking vehicle named TITAN-VIII. The obtained results show that the 3D sway compensation trajectory proposed in our previous paper has advantages in view of energy efficiency as compared with the original sway compensation trajectory.
Stable gait control for a biped robot
We develop the sway compensation trajectory for a biped robot, and show that dynamically stable walking is realized. This method makes it quite easy to design stable ZMP and COG (center of gravity) trajectories, which have been regarded as a very complicated and delicate problem. The effectiveness of the proposed method is verified through computer simulations and walking experiments by a humanoid robot, HOAP-1.
| Walking experiment | Dance by HOAP | Omni-directional walking motion |
Step climbing | Step climbing | Dance step by fusing dynamically and statically stable walking |
 |
 |
 |
 |
 |
 |
Straight legged walking for a biped robot
We propose a new methodology for generating a straight legged walking pattern for a biped robot utilizing up-and-down motion of an upper body. Firstly, we define two new indexes, the Knee Stretch Index (KSI) and the Knee Torque Index (KTI), which indicate how efficiently the knee joints are utilized. Next, up-and-down motion of the upper body is automatically planned so that these indexes are optimized and straight legged walking is realized. The basic idea of the proposed method is, i) when a large number of DOFs of motion are required for controlling the ZMP, a robot makes its body height lower, ii) when there is a extra number of DOFs of motion, the body is lifted and the knee joint is stretched. By stretching the knee joints, human-like natural walking motion is obtained.Moreover, energy efficiency is improved since required torque and energy consumption to support the body weight become small at knee joints.
| Straight Legged Walking | Straight Legged Walking |
 |
 |
Proactive Human Interface based on Enbodied Agents
We are conducting research on "Embodied Proactive Human Interface". The aim of this research is to develop a new human-friendly active interface based on two key technologies, an estimation mechanism of human intention for supporting natural communication named "Proactive Interface", and a tangible device using robot technology. We have developped the humanoid-type two-legged robot named "PICO-2", which was developed as a tangible telecommunication device for the proactive human interface. In order to achieve the embodied telecommunication with PICO-2, we propose new tracking technique of human gestures using a monocular video camera mounted on PICO-2, and natural gesture reproduction by PICO-2 which absorbs the difference of body structure between the user and the robot. Remote communication experiments were also carried out using two PICO-2 robots placed at distant campuses.
| PICO | PICO-2 | PICO-2 | PICO-2K |
 |
 |
|
 |
| Mimic gestures | ZMP balance control | Mimic gestures | Omnidirectional motion |
On-board IEEE1394 Camera |
 |
 |
 |
 |
 |
| Motion tracking by monocular camera | Remote communication experiments |
 |
 |
Cooperative positioning system for multiple robots, CPS
For autonomous mobile robots, a high precision positioning method in unstructured and dynamically changing environments is indispensable. Dead reckoning is a popular method but due to the error accumulation from wheel slippage, its reliability is low for measurement of long distances especially on uneven surfaces. Another popular method is the landmark method, which estimates current position relative to known landmarks, but the landmark method's limitation is that it cannot be used in an uncharted environment. GPS (Global Positioning System) has high performance as a three-dimensional positioning system on the ground level. However, it cannot be used in the environment where radio waves cannot reach such as indoors or underground. To overcome these shortcomings, we have been proposing a new method called "Cooperative Positioning System(CPS)". The main concept of CPS is to divide the robots into two groups, A and B where group A remains stationary and acts as a landmark while group B moves and then group B stops and acts as a landmark for group A. This process is repeated until the target position is reached. Compared with dead reckoning, CPS has a far lower accumulation of positioning errors, and can also work in three dimensions. Furthermore, CPS employs inherent landmarks and therefore can be used in uncharted environments unlike the landmark method. We have developed several CPS machine models named CPS-I, CPS-II and CPS-III, and demonstrated their performance for several tasks, such as floor cleaning and surveying in an unknown environment.
| CPS-I | CPS-II | Floor cleaning experiment with CPS-III |
Accurate positioning in outdoor with CPS-IV |
Laser sensing robots, CPS-V |
 |
 |
 |
|
 |
| Cleaning robot |
 |
| Mechanical wall following robot | Wall following experiment １ | Wall following experiment 2 |
 |
 |
 |
| Mechanical wall following robot | Wall following experiment 3 | Automatic map creation experiment |
 |
 |
 |
Rapid 3D geometrical modeling using Fast Level Set Method
The level set method, introduced by S. Osher and J. A. Sethian, has attracted much attention as a method that realizes a topology free active contour modelling. This method utilizes an implicit representation of a contour to be tracked, and is able to handle the topological change of the contour intrinsically. Various applications based on the level set method have been presented including motion tracking, 3D geometric modelling, and simulation of crystallization or semiconductor growth. However, the calculation cost of reinitialization and updating of the implicit function is considerably expensive as compared with the cost of conventional active contour models such as ``Snakes''.
We propose an efficient calculation algorithm for the level set method named the Fast Level Set Method (FLSM). Characteristics of the proposed FLSM are as follows: i) the use of the extension velocity and the high speed construction of the extension velocity field using the Fast Narrow Band Method, ii) the frequent execution of the reinitialization process of the implicit function which requires little calculation cost. The efficiency of the proposed method is verified through computer simulations, and two kinds of typical applications; realtime tracking of moving objects in video images and fast 3D surface reconstruction from scattered point data.
| Bunny (Stanford Univ.) |
Wired basket |
 |
 |
Realtime tracking of multiple objects using Fast Level Set Method
| Simultaneous tracking of moving objects |
Fast detection of moving objects |
Labeling | Skeleton extruction |
 |
 |
 |
 |
Development of robust motion capture system using FLSM and stereo cameras
We are developing a new motion capture system using the Fast Level Set Method and multiple stereo cameras. This system can capture multiple motion data performed by several people simultaneously even if they are occluded each other.
| Motion | Captured data | After texture mapping |
Motion capture |
 |
 |
 |
 |
Patient-specific 3D bone shape estimation of femur from two radiographs
We are conducting joint researches with Medical School of Kyushu University and Osaka University. The research topics include the navigation system for endoscopic robotics surgery, 3D diagnosis system for hip replacement surgery, image guide for endotracheal intubation, etc. For instance, we propose a method to estimate a 3D shape of patient's femur from two radiographs and a parametric femoral model. Firstly, we develop the parametric femoral model utilizing statistical procedure of 3D femoral models taken by CT images of a number of patients. Then, the pose and patient-specific shape parameters of the parametric model are estimated from two 2D radiographs using a distance map constructed by the Level Set Method. Experiments using synthesized images, fluoroscopic images of a phantom femur, and in vivo images for hip prosthesis patients are successfully carried out, and it is verified that the proposed system has practical applications.
 |
 |
Kaori Nakamura, Ryo kurazume, Toshiyuki Okada, Yoshinobu Sato, Nobuhiko Kanno, Tsutomu Hasegawa, 3D reconstruction of a femoral shape using a parametric model and two 2D radiographs, Meeting on Image Recognition and Understanding 2006 (MIRU2006), OS2B-3, (2006 7) in Japanese
2D-3D Registration for Navigation System of Surgical Robot
We have proposed a new registration algorithm of 2D color images and 3D geometric models for the navigation system of surgical robot. A 2D-3D registration procedure is used to precisely superimpose a tumor model on an endoscopic image and is therefore indispensable for the surgical navigation system. Thus, the performance of the 2D-3D registration procedure influences directly the usability of the surgical robot operating system. One of the typical techniques that has been developed is the use of external markers. However, the accuracy of this method is reduced by the breathing or heartbeat of the patient, as well as other unknown factors. For precise registration of 3D models and 2D images without external markers or special measurement devices, a new registration method is proposed that utilizes the 2D images and their distance maps as created by the Fast Marching Method.
| 2D-3D registration | Tracking a 3D object | Endoscopic image | Endoscopic image |
 |
 |
 |
 |
2D-3D alignment based on geometrical consistency
We have proposed a new registration algorithm of a 2D image and a 3D geometrical model for reconstructing a realistic 3D model of indoor scene settings. One of the typical techniques of pose estimation of a 3D model in a 2D image is the method based on the correspondences between 2D photometrical edges and 3D geometrical edges projected on the 2D image. However, for indoor settings, features extracted on the 2D image and jump edges of the geometrical model, which can be extracted robustly, are limited. Therefore, it is difficult to find corresponding edges between the 2D image and the 3D model correctly. For this reason, in most cases, the relative position has to be manually set close to correct position beforehand. To overcome this problem, in the proposed method, firstly the relative pose is roughly estimated by utilizing geometrical consistencies of back-projected 2D photometrical edges on a 3D model. Next, the edge-based method is applied for the precise pose estimation after the above estimation procedure is converged. The performance of the proposed method is successfully demonstrated with some experiments using simulated models of indoor scene settings and actual environments measured by range and image sensors.
| 2D-3D alighment | Alignment result |
 |
 |
Visual servo using redundancy
 |
 |
Geometrical and photometrical modeling of real objects using laser range
finders and digital cameras
Tokyo University, Ikeuchi Lab.
| Textured image of Kamakura Great Buddha |
 |
In order to construct three dimensional shape models of large scale architectures by a laser range finder, a number of range images are normally taken from various viewpoints and these images are aligned using post-processing procedure such as ICP algorithm. However in general, before applying ICP algorithm, these range images have to be registered to correct positions roughly by a human operator in order to converge to precise positions. In addition, range images must be overlapped sufficiently each other by taking dense images from close viewpoints.
We proposes a new measurement system for large scale architectures using a group of multiple robots and an on-board laser range finder. Each measurement position is identified by the highly precise positioning technique named Cooperative Positioning System or CPS which utilizes the characteristics of multiple robots system. The proposed system can construct 3D shapes of large scale architectures without any post-processing procedure such as ICP algorithm and dense range measurements.
(5MB)
(5MB)
| A group of robots equipped with laser range finder, CPS-V |
 |
|
3D map of large scale architecture |
  |
| Demo movie | |||
|
 |
 |
 |
We are conducting the research project named Robot Town Project.
The aim of this research is to develop a distributed sensor system such as cameras, laser range finders, and IC tags, and its management system so that autonomous robots can work with humans in an ordinary environment for daily human life. Research topics include i) a sensor network system consisting of distributed cameras and laser range finders for multiple objects tracking, and ii) a human motion capturing system using multiple distributed cameras.
| Tracking of multiple targets | Tracking of 11 perpole by singe particl filter | Tracking in a house |
 |
.jpg){kind=tracking} |
 |
| Human motion capturing by distributed cameras |
Robot control by gesture |
 |
 |
Motion analysis of free flying robots| Free flying robot |
|
Impedance/Inertia matching for serial link manipulators
We propose a new index for dynamic performance analysis of serial link manipulators named Impedance/Inertia Matching Ellipsoid, or IME. Several indexes have been proposed for indicating static and dynamic performance of robot manipulators. For example, Dynamic Manipulability Ellipsoid (DME) characterizes distributions of hand acceleration produced by normalized joint torque. Manipulating-Force Ellipsoid (MFE) denotes static torque-force transmission efficiency from actuators at joints to a hand. On the other hand, the proposed IME characterizes dynamic torque-force transmission efficiency from actuators at joints to a load held at the hand of the manipulator. The IME includes a wide range of concepts proposed so far as measures of manipulator's performance. The DME and the MFE are both derived from the IME as limiting forms about the load mass. We demonstrate the IME with some numerical examples including the selection of an optimal leg posture for jump robots, optimum active stiffness control, and an extension for manipulators mounted on satellites in outer space.
| IME, DME, and MFE | Experiments using PA-10 |
 |
 |
