Tsukasa Ogasawara

Development of the NAIST-Hand with Vision-based Tactile Fingertip Sensor

This paper introduces a multifingered robotic hand eNAIST-Handf and a grip force control by slip margin feedback. The developed prototype finger of the NAIST-hand has a new mechanism by which all 3 motors can be placed inside the palm without using wire-driven mechanisms. A method of grip force control is proposed using an incipient slip estimation. A new tactile sensor is designed to active the proposed control method by the NAIST-Hand. This sensor consists of a transparent semispherical gel, an embedded small camera, and a force sensor in order to implement the direct slip margin estimation. The structure and the principle of sensing are described.

Behavior recognition based on head pose and gaze direction measurement

To build smart human interfaces, it is necessary for a system to know a users intention and point of attention. Since the motion of a persons head pose and gaze direction are closely related to his/her intention and attention, detection of such information can be utilized to build natural and intuitive interfaces. In this paper, we describe a behavior recognition system based on the real-time stereo face tracking and gaze detection system to measure head pose and gaze direction simultaneously. The key aspect of our system is the use of real-time stereo vision together with a simple algorithm which is suitable for real-time processing. Our system we can significantly simplify the algorithm for 3D model fitting to obtain the full 3D pose of the head compared with conventional systems that use monocular camera. The recognition of attentions and gestures of a person is demonstrated in the experiments.

Study of deformation and insertion tasks of a flexible wire

Insertion of a flexible wire into a hole is a difficult task because the wire has a tendency to buckle under external forces. Moreover, the plastic deformation occurs on a flexible wire when the force acting on the wire is big. In this paper, we propose a method of inserting a flexible wire whereby a force acts on the wire and the shape of the wire is observed by stereo vision. A strategy to transform the deformed wire to the straight one and to insert the wire into a hole is presented. Finally, some experimental results are shown.

Pinpointed muscle force control using a power-assisting device: System configuration and experiment

The demand for rehabilitation robots is increasing for the upcoming aging society. Power-assisting devices are considered promising for enhancing the mobility of elderly and disabled people. Other potential applications are for muscle rehabilitation and sports training. The main focus of this paper is to control the load of selected muscles by using a power-assisting device, thus enabling ldquopinpointedrdquo motion support, rehabilitation, and training by explicitly specifying the target muscles. By taking into account the physical interaction between human muscle forces and actuator driving forces during power-assisting, the feasibility of this muscle force control is analyzed as a constrained optimization problem. A prototype power-assisting device driven by pneumatic rubber actuators is developed. A control system is developed with a graphical user interface that provides an easy operation to designate desired forces for target muscles. The validity of the method is confirmed by experiments by measuring surface electromyographic (EMG) signals for target muscles.

Indoor Navigation for a Humanoid Robot Using a View Sequence

Humanoid robots are expected to work in the human environment due to their similarity to the human shape, and they are required to achieve localization and navigation autonomously. In this paper, indoor navigation is realized based on a view-based approach using a camera mounted on the head. In the case of a humanoid robot, image blur and swing due to walking is a crucial issue for image matching during localization. The quantitative effect of walking on the image is firstly investigated by utilizing a motion capture system. Then a method to generate a stable view sequence is proposed based on the detection of optical flows. The navigation function with the proposed method was implemented on a humanoid robot HRP-2, and the effectiveness was confirmed by indoor walking experiments.

Development of an optical 2-axis force sensor usable in MRI environments

This paper presents a MR compatible force sensor. Recently, MRI are widely used in various fields, from medical purpose to brain science, and simultaneous measurement of force information enables more precise investigations of obtained images of living tissue. However, conventional metal force sensors which contaminate the true signals of MRI cannot be used in MRI environments. Furthermore, present MR compatible force sensors have limitation in accuracy, dynamic range and multi axis sensibility. In this paper, an optical 2-axis force sensor without any metal and electronic components in the sensing element is developed with photo sensors and optical fibers.

An optical 6-axis force sensor for brain function analysis using fMRI

This paper presents an 6-axis optical force sensor which can be used in fMRI. Recently, fMRIs are widely used for studying human brain function. Simultaneous measurement of brain activity and peripheral information, such as grip force, enables more precise investigations in studies of motor function. However, conventional force sensors cannot be used in fMRI environment, since metal elements generate noise which severely contaminate the signals of fMRI. An optical 2-axis force sensor has been developed using photo sensors and optical fibers by Tada et. al.(2002), that resolved these problems. The developed force sensor removed all magnetic components from the sensing part. It detected minute displacements by measure amount of light and light traveled through the optical fibers. However, there still remain several problems on this optical force sensor. Firstly, the accuracy is not high compared to the conventional force sensors. Secondly, the robustness is not enough against the contact force to the optical fibers. In this paper, the problems concerning to the accuracy and the sensor output stability has been improved by novel methods of fixing fibers and arithmetic circuit. Furthermore, an optical 6-axis force sensor is developed based on these improvements, and usefulness of our sensor for brain function analysis is confirmed in fMRI experimentations.

Study of insertion task of a flexible wire into a hole by using visual tracking observed by stereo vision

Measuring the force on a flexible wire is difficult by using force/torque sensors when the flexural rigidity of the wire is small because the wire buckles and the force on the wire is smaller than the force that can be measured by a force/torque sensor. This paper presents a method of calculating the force on a wire from its shape observed by stereo vision. We propose a method of inserting the wire into a hole in a wall by using the estimated force. Three experiments have been successfully carried out.

Methods to detect contact state by force sensing in an edge mating task

Methods to detect the contact state of an end-effector and the environment by force sensing, which is a useful technique for very small motions, are described. One method estimates the position of the contact point, while another method detects the transition of the contact state. These methods are implemented on an edge-mating task. The contact position is estimated with two sets of observed relative force and moment, and the forces to be applied for the estimation are determined based on the singular value decomposition technique. Transition detection is achieved by monitoring the relation between observed force and moment. Experiments demonstrate the effectiveness of this technique, which is robust against force noise caused by friction and the characteristics of the manipulator control.<<ETX>>

Manipulating deformable linear objects - contact states and point contacts

The task of handling non-rigid one-dimensional objects by a robot manipulation system is investigated. To distinguish between different non-rigid object behaviors, five classes of deformable objects from a robotic point of view are proposed. Additionally, an enumeration of all possible contact states of one-dimensional objects with polyhedral obstacles is provided. Finally, the qualitative motion behavior of linear objects is analyzed for stable point contacts. Experiments with different materials validate the analytical results.