Nobuaki Nakazawa

Control of a robot hand emulating human's hand-over motion

In medical and household applications, it is necessary to consider the hand-over of an object between a human and a robot. In this paper, a physiological method motivated by the study of human hands is discussed for a robot to grasp an object or release a grasped object stably without using an object model as a man does. A humans grasping behavior is analyzed by measuring the grasp and friction forces simultaneously as a man grasps an experimental device which is designed for grasping or hand-over. The human controls the grasp force by sensing the friction force, that is, the weight of the object which is felt on his hand, but when the slip is detected by sensing skin acceleration, the grasp force becomes much greater than the minimum force required for grasping by adding the force which is proportional to the acceleration. And two methods that can predict when and how fingers will slip upon a grasped object are discussed. The experimental results show the smooth hand-over of an object between a man and a robot hand.

Force control of a robot gripper based on human grasping schemes

Abstract This paper describes the force control of a robot gripper that is modeled on the basis of human grasping schemes. In the cases in which fluctuation in load is induced by movement of the object, human beings are able to precisely change the grasping forces according to changes in fingertip forces perpendicular to the grasping direction. The characteristics of strengthening and weakening of forces vary with respect to the safety margin. Here, a model for determining the grasping force of a robot gripper, which depends on the objects acceleration, is described. In this model, unexpected subtle load forces can be compensated by minimal required forces to prevent slip.

Development of welfare support-equipment for personal computer operation with head tilting and breathing

This paper describes support-equipment of operating a personal computer for users who have an obstacle on the regions of upper limb. The user wears a head set device with an angle sensor, and holds a plastic pipe connected to a pressure sensor in his or her mouth. Tilting his or her head and breathing are used for a mouse cursor operation and characters input. The voluntary tilt angle range and breath strength are memorized to the controller beforehand, so that operations can be performed without fatigue by considering users body situations. In mouse operation, cursor can be moved according to the tilt angle, and click operations are executed by breathing in or out to the plastic pipe. In characters input, character board on which LEDs are distributed with a matrix form is prepared for indicating HIRAGANA characters in front of a CRT monitor. Tilting motions change the indicated character and breathing motions can input the selected character.

A Design Method for Two-Degree-of-Freedom Multi-Period Repetitive Control Systems

Multi-period repetitive controllers improve the disturbance attenuation characteristic of the modified repetitive control system that follows the periodic reference input with a small steady state error. Recently, the parameterization of all stabilizing multi-period repetitive controllers was studied. However, when the parameterization of all stabilizing multi-period repetitive controllers is used, the input-output characteristic and the feedback characteristic cannot be specified separately. From the practical point of view, it is desirable to specify the input-output characteristic and the feedback characteristic separately. In addition, the parameterization is useful to design stabilizing controllers. Therefore, the problem of obtaining the parameterization of all stabilizing two-degree-of-freedom multi-period repetitive controllers that can specify the input-output characteristic and the disturbance attenuation characteristic separately is important to solve. In this paper, we propose the parameterization of all stabilizing two-degree-of-freedom multi-period repetitive controllers.

A Design Method for Robust Stabilizing Modified Repetitive Controllers for Time-Delay Plants

In this paper, we examine the parameterization of all robust stabilizing modified repetitive controllers for time-delay plants. The modified repetitive control system is a type of servomechanism designed for a periodic reference input. When modified repetitive control design methods are applied to real systems, the influence of uncertainties in the plant must be considered. The stability problem with uncertainty is known as the robust stability problem. Recently, the parameterization of all stabilizing modified repetitive controllers was obtained. Since the parameterization of all stabilizing modified repetitive controllers was obtained, we can express previous study of robust stabilizing modified repetitive controller in a uniform manner and can design a stabilizing modified repetitive controller systematically. However, the parameterization of all robust stabilizing modified repetitive controllers for time-delay plants has not been obtained. In this paper, we clarify the parameterization of all robust stabilizing modified repetitive controllers for time-delay plants.

Psychological evaluations of fusion motions emulating exercises of human's arm extension with shoulder movements

This work deals with psychological evaluations of fusion motions for a robot manipulator emulating exercise of humans arm extension with shoulder movements. In cases where the goal position is put in a further place than the length of the extended arm, not only the velocity profile of the hand by extension exercise but also that of the shoulder by anteflexion exercise are bell-shaped. These two exercise are simultaneously performed, but the hand velocity becomes a peak earlier in comparison with the shoulder one. Reproducing the measured human data, the exercises of a three-link arm with shoulder or body movements are simulated and the characteristics of a human-likeness fusion are examined by shifting the start time of the shoulder movement. Evaluation result says that the relation between the velocity peak positions of the hand and shoulder remarkably influences on the human-likeness.

Development of an intuitive interface based on facial orientations and gazing actions for auto-wheel chair operation

This paper suggests an intuitive interface based on the facial orientations and gazing actions for auto-wheel chair operation. The real-time image of the operators face was taken to the computer through the USB camera to observe the operational intention. The changes in the darkness area of the both nostrils were utilized for recognition of the face orientations. When the operator faced to up and downward, the darkness areas of both nostrils were increased and decreased, respectively. On the other hand, the difference between two nostril areas could be caused in cases where the face was turn to the side. Here, these characteristics were utilized for the recognition of the face orientations. Moreover, gazing actions was recognized by the curve ratio of the operators eye lines. Only when the operator gazed to the control computer, the facial orientation was reflected to operate the auto-wheelchair, instead of a joystick interface.

Hand-free interface based on facial orientations

This paper suggests a hand-free interface based on the facial orientations. The operators face was observed by the USB camera and the changes in the darkness area of the both nostrils were utilized for recognition of the face orientations. When the operator faced to up and downward, the darkness areas of both nostrils were increased and decreased, respectively. On the other hand, the difference between two nostril areas could be caused in cases where the face was turn to the side. Here, these characteristics were reflected to the recognition of the face orientations. The facial orientations were applied to the auto-wheelchair operations, instead of a joystick device.

Development of an interface based on face orientations for operation of auto-wheelchair

This paper describes the non-contact Man-Machine in terface based on the face orientations. The real-time image of the operators face was observed by the USB camera and the changes in the darkness area of the both nostrils were utilized for recognition of the face orientations. When the operator faced to up and downward, the darkness areas of both nostrils were increased and decreased, respectively. On the other hand, the difference between two nostril areas could be caused in cases where the face was turn to the side. Here, these characteristics were reflected to the recognition of the face orientations. The developed interface was applied for the operation of the electrical wheelchair.

Development of an Interface Based on Mouth Open/Close Motions

This paper suggests a new type interface using the user’s mouth open/close motions. The user’s face was observed by the USB camera and the changes in the darkness on the mouth image were utilized as an interface. In order to improve the procedure speed, the only image around the mouth was used for image processing. This focused image area could be moved according to the movement of the user’s face, based on the displacement of the nostril with respect to the original position. Moreover, the developed interface was applied to the operations of the meal support manipulator. In the test operation, the developed interface could be successfully used after a few times practices.