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Highly precise positioning control is based on mechatronics. Nanotechnology, especially nanometer positioning technology with high-speed and robust positioning feedback control, is used in various technical fields including measuring systems, magnetic recording and the semiconductor industry. To date, various actuator systems have been proposed, but the structural models have working distance of either less than a millimeter or more than ten millimeters. A structural model with working distance of several millimeters has not been reported in the relevant literature. We propose an actuator structural design that would enable production of actuator systems with such working distances. This actuator has a voice coil motor and a new guide with an elastic support mechanism consisting of a special spring that is restricted to movement in only one direction. This ESM causes no lost motion, friction with motion, or mechanical play. The voice coil motor thrusts and displaces the elastic support mechanism linearly. Therefore, highly precise positioning control can be realized using a simple controller. This paper describes evaluation of the positioning control method from the displacement of ESM and presents basic data for development of future nano-actuator systems.

Many methods for physical medicine and rehabilitation strategies have been developed for physically disabled people. Most of them have been determined by physical therapists based on anatomical and physiological assessment of the subject. With application of robot technology which allows smooth achievement of complex trajectories, and with loading or assisting designated muscles in an accurate manner, a better rehabilitation strategy can be developed. In this paper, we propose a new method to design the motion trajectory of lower limbs and the applied forces acting on the foot. In order to improve the rehabilitation effect in full consideration of biomechanical stability of the trajectory and musculo-skeletal model of each subject, we have applied genetic algorithm to search the parameters of spline curves for the trajectory and the applied force acting on subject's foot. The usefulness of the proposed method is confirmed through simulation results and the comparison with a conventional training trajectory.

To compare the sitting balance capabilities of healthy young women with those of women with idiopathic scoliosis, we performed experiments using a system for evaluating dynamic sitting balance. The system comprised a three-dimensional position and orientation sensor for measuring the upper body joint angle, a stabilometer for measuring the center of pressure (COP) trajectory and seat reaction force, and a six-degree-of-freedom platform for producing seat perturbation. The seat reaction force and joint angle of the upper body were used to calculate the joint torque of the 5th lumbar and 12th thoracic vertebra. During the experiments, 13 control subjects and 21 women with idiopathic scoliosis tried to maintain a sitting posture relative to the seat perturbation (0.25 Hz and 0.5 Hz, 5 deg amplitude). For seat perturbation of 0.5 Hz, the root mean square, mean velocity along the trajectory, and excursion area (COP parameters), and the joint torque of the 12th thoracic vertebra in women with idiopathic scoliosis were significantly higher than those in the control subjects. Results suggest that the dynamic sitting balance ability of women with idiopathic scoliosis is inferior and that a large physical load is necessary for them to maintain a sitting posture.

The authors proposed a new actuator for track following on a spin-stand that evaluated magnetic heads and media for high density magnetic recording with high speed. The new actuator was named “Nano-Motion Actuator (NMA)” by the authors. At the present time, effect of azimuth angle which causes between a center line of a head slider and a tangential direction of the track is increasingly actualized as a track pitch of the head becomes narrow. Therefore, if a discrete track media (DTM) will be put to practical use, the effect of the azimuth angle will be actualized more clearly. Because, DTM will have large RRO (Repeatable Run-Out) that is caused by eccentricity error between a medium and a hub of an air-spindle. Furthermore, NRRO (Non-Repeatable Run-Out) which is caused by mechanical vibration of the air-spindle, flutter of the medium, turbulence around a HGA (Head gimbals Assembly) and so on is overlapped with the RRO. Especially in case of the large NRRO, since the azimuth angle will rapidly change, compensations of the azimuth angle should be absolutely necessary. Therefore, precision positioning actuator with high speed on an X-Y plane which is coplanar will be required the evaluation of the high density magnetic recording. We proposed a new actuator which was consisted of a NMA mechanism and a translation mechanism. The translation mechanism was composed of a stacked piezoelectric that was supported by two elastic springs. The new actuator that was called “2D Nano-Motion Actuator (2D NMA)” could move within 10 square micrometer and be positioned by nanometer resolution with high speed.

As people grow older, the ability to walk becomes ever more important to live an independent life. A simple system that is useful for evaluation and analysis of gait is necessary. Our goal is to design a wearable gait analyzer. In this study, we estimated the floor reaction force vector using an ultra-thin pair of wearable sensor pads. The floor reaction force vector, when someone is walking, is in the direction of the body's center of gravity. The gap separating the floor reaction force vector and the body's center of gravity generates a rotation moment, which is what we used to create this equation. Our evaluation method will be useful for future development of sensor systems.

Humans have the ability to identify external physical properties because skilled object manipulation requires knowledge, or internal models, of object dynamics relating to applied force or movement. The accuracy of identification depends on those of the input and output signal to the object : motor command from brain as the input and information from multiple sensory modalities as the output. In this paper, control strategies of isometric contraction by hand are investigated. Subjects are asked to generate constant levels of force under two conditions : force production tasks a) by self scaling without visual feedback and b) with visual feed back of reference force levels. The results show subjective assessments of force are larger than objective one, and it is indicated that the variability is composed of signal dependent noise and error of human intention. It is also demonstrated that visual feedback information has an important role of generating accurate reference force level.

In case of a lower limb prosthesis, the most important parameter is the fitting between the cut section of the leg (stump) and the socket. It has been observed that the contact pressure between the socket and the stump changes after the alignment of the lower limb prosthesis changes and also during dynamic movement such as walking or running. The main aim of this research is to design a novel socket using smart materials, such as magneto-rheological (MR) fluid, which can transform the rigidity and capacity of the socket to accommodate the dynamic movement and alignment changes. In order to determine design parameters of the socket, we conducted various experiments such as subjective evaluation of pain by the contact pressure, measurement of the stiffness of the MR bag in which MR fluid was filled up. The MR socket was actually developed as a prototype based on the above experiments. The fitting between the stump and the socket was investigated subjectively and also based on the pressure sensors. The contact pressure and the pain felt by the amputee using a lower limb prosthesis have become smaller in the proposed MR socket, especially, on the patellar tendon. The proposed MR socket had a possibility to improve the fitting between the stump and the socket.

In this paper, we analyze a user-friendliness of wheelchair propulsion by using a dynamic index of the driving force. The index explains how much margin the user can take in joint moments to his maximum ability during wheelchair propulsion, and is expressed by the dynamic manipulating force ellipsoid (DMFE). The DMFE is illustrated from the measured values of maximum generated moments at the user's upper limb joints, and is used to understand quantitatively the margin of the user's ability for wheelchair propulsion. Based on the index, we have also proposed the concept of the driving force contribution figure (DFCF) to clarify how efficient the user accomplishes the wheelchair propulsion. The DFCF expresses the direction cosine of generated force on the handrim to the tangential direction. If the DFCF takes large value along the driving force direction, it means the applied force acts efficiently for wheelchair propulsion. In order to show the effectiveness of DMFE and DFCF, we measured the driving motion of the upper limb, hand force applied to the handrim, and the individual's muscular power characteristics for eight experienced wheelchair users. From the experimental data, it is shown that the users start driving the handrim at such posture where it is difficult to generate required hand force to drive the wheelchair. It is also shown that the user are driving the wheelchair taking the load of the upper limb and the efficiency of the wheelchair propulsion into consideration.

In this paper, we have applied the analysis method for the robot manipulators to the evaluation of the manipulation ability of the human upper limb. The set of maximum hand force based on individual's muscular power characteristics were expressed in the six-dimensional convex polyhedron (Manipulating Force Polyhedron). The spatial characteristic of the manipulation ability of the upper limb in three-dimensional space was clarified by the visualization of the six-dimensional convex polyhedron using a new vertex search algorithm. In order to show the effectiveness of the proposed method, we compared manipulating force polyhedron with measured maximum hand force. The manipulating force polyhedron was calculated from measured maximum joint torque of the upper limb depending on joint angle and rotation direction. Our evaluation method will be useful not only for the evaluation of the manipulation ability of the upper limb but also for the development of equipment based on individual's muscular power characteristics.

Central Pattern Generators (CPGs) are considered as the neural controllers for cadent human movements. Several walking simulators have been successfully constructed with CPGs. Although the CPGs serves as a reflex function of the neural system to generate rhythms of walking, it does not have adjustability to changes in the environment. It has been proposed as a hypothesis that CPGs will be modified to adapt when sensory organs sense a change of the environment during walking. According to the hypothesis, we propose to introduce a mechanism for modifying CPGs into a walking simulator in this paper. The proposed mechanism is tested in stair climbing. The signal patterns for input to CPGs are tuned according to the height of step. The proposed mechanism allows the walking simulator to adapt to different heights of step.

This paper discusses the integrated design of structural shape and controller of high-speed positioning actuators for magnetic recording test stands. To allow highly flexible shape design of the mechanism for the positioning actuator and to improve the calculation efficiency in the structural shape optimization, this paper proposes an integrated design method in which a structural shape is defined like as a skeleton and meats and a genetic algorithm is used to search the combination of the skeleton and meats for obtaining better performance of the closed-loop system in iterative design procedure. The iterative optimization procedure includes the shape and the controller updates. It is shown in design examples that the proposed integrated design method can improve the performance of the positioning actuator according to the performance indices, and the effect is verified.