Chikamune Wada

Pressure Sensor: State of the Art, Design, and Application for Robotic Hand

We survey the state of the art in a variety of force sensors for designing and application of robotic hand. Most of the force sensors are examined based on tactile sensing. For a decade, many papers have widely discussed various sensor technologies and transducer methods which are based on microelectromechanical system (MEMS) and silicon used for improving the accuracy and performance measurement of tactile sensing capabilities especially for robotic hand applications. We found that transducers and materials such as piezoresistive and polymer, respectively, are used in order to improve the sensing sensitivity for grasping mechanisms in future. This predicted growth in such applications will explode into high risk tasks which requires very precise purposes. It shows considerable potential and significant levels of research attention.

Recovery patterns in the physiological responses of the autonomic nervous system induced by mental workload

It is widely understood that mental stress produces various physiological changes. Though the relationship between mental stress and physiological feedback has been extensively reported, few reports have tried to clarify the relationships between physiological responses and the intensity level or type of stress. In this study, we investigated autonomic nervous system activities to find a physiological index based on which we can evaluate the intensity of mental stress. As a result, we found that some physiological indexes acquire certain characteristics during the recovery process, and we consider that these indexes might be related to the intensity of mental stress.

Improvement study for measurement accuracy on wireless shoe-type measurement device to support walking rehabilitation

We have developed a shoe-type measurement device which is able to measure gait information such as step length, width and pressure distribution while daily living. We hypothesized that a walking rehabilitation system could be realized by combining shoe-type device and comprehensively display which showed analytical results for gait with real time operation. From evaluation to first trial manufacture, it was found that our system was effective to let the patients, physicians and physical therapists know quantitative gait information. However, it was also found that there were some problems such as insufficient measurement area. Then, hardware of device was redesigned to enlarge measurement area but measurement accuracy decreased. Therefore, improvement method which could decrease measurement error was proposed and the efficacy of proposition was revealed by experimental results.

Development of a shoe-type device for collecting gait information

We are developing a measurement device by means of which gait information can be obtained that cannot be obtained by existent devices. We are also evaluating the effectiveness of the device in rehabilitation programs. The final goal of our work is to realize a space where patients can exe- cute their rehabilitation routines at any time. In this paper, we report the outline of our novel measurement device. That is to say, we describe our real-time measurement technique for measuring the position and angle of the feet to obtain the gait information, as well as our method of presenting the gait in- formation.

Proposal of a new tactile display method of speech signals as a nonverbal communication for the profoundly hearing impaired

We have designed a fingertip tactile vocoder which has a 16/spl times/4 vibrator matrix for the deaf. In order to investigate whether or not sweeping display method is useful for recognizing Japanese consonants, vibratory patterns corresponding to the speech spectrum of monosyllables were swept from right to left on a fingertip surface using 4 columns of the vibrator matrix at fixed speeds. The best sweeping velocity was estimated to be 10 cm/sec from the experimental results of the absolute threshold, the two-point threshold and the identification rate of monosyllables. The sweeping display method was shown to overcome the problems such as temporal masking for the consonants, especially for the plosives.<<ETX>>

Basic Study on Presenting Distance Information to the Blind for Navigation

Most electronic travel aids for the visually impaired and blind persons use voice instruction to inform the device users of the distance to the destination. However, presentation method of voice instruction have not been designed by taking into account the specific characteristics of human cognition, and so users sometimes would be confused. Then, in this paper, we would like to investigate optimal presentation method. From the results, we proposed a new distance-presentation method by voice instruction and revealed its efficacy.

Attitude Estimation Using Kalman Filtering: External Acceleration Compensation Considerations

Attitude estimation is often inaccurate during highly dynamic motion due to the external acceleration. This paper proposes extended Kalman filter-based attitude estimation using a new algorithm to overcome the external acceleration. This algorithm is based on an external acceleration compensation model to be used as a modifying parameter in adjusting the measurement noise covariance matrix of the extended Kalman filter. The experiment was conducted to verify the estimation accuracy, that is, one-axis and multiple axes sensor movement. Five approaches were used to test the estimation of the attitude: (1) the KF-based model without compensating for external acceleration, (2) the proposed KF-based model which employs the external acceleration compensation model, (3) the two-step KF using weighted-based switching approach, (4) the KF-based model which uses the threshold-based approach, and (5) the KF-based model which uses the threshold-based approach combined with a softened part approach. The proposed algorithm showed high effectiveness during the one-axis test. When the testing conditions employed multiple axes, the estimation accuracy increased using the proposed approach and exhibited external acceleration rejection at the right timing. The proposed algorithm has fewer parameters that need to be set at the expense of the sharpness of signal edge transition.

Influence of electrical stimulation on hip joint adductor muscle activity during maximum effort

[Purpose] This study investigated whether hip adductor activity was influenced by electrical stimulation of the tensor fascia lata muscle. [Subjects and Methods] The subjects were 16 nondisabled males. Each subject was asked to adduct the hip joint with maximum effort. The electromyogram of the adductor longus was recorded under two experimental conditions, with and without electrical stimulation of the tensor fascia lata. [Results] In the presence of electrical stimulation, muscle activity decreased to 72.9% (57.8–89.3%) of that without stimulation. [Conclusion] These results suggested that inactivation of the adductor group was promoted by electrical stimulation of the tensor fascia lata.

Complementary filter for orientation estimation: Adaptive gain based on dynamic acceleration and its change

An attitude and heading reference system that comprises a low-cost inertial measurement unit and a magnetometer is often inaccurate during highly dynamic motion. To mitigate sensor errors, we used a well-known complementary filter. The basic objective in using this filter was to compensate for the drift in the gyro by using the accelerometer and magnetometer as an assistance component. This paper presents the design of an adaptive mechanism to adjust filter gain using a fuzzy logic controller. We hypothesize that dynamic acceleration and change in dynamic acceleration can be used as inputs for the controller. The controller thus produces two adaptive gains for use as filter gains. The experimental result shows that the estimated angle has a good trend until a specific time, i.e., until the influence of the gyro-drift causes estimated angle divergence.

Analysis of Crutch Position in the Horizontal Plane to Estimate the Stability of the Axillary Pad in the Axilla during Single-crutch Walking

[Purpose] The aim of this study was to estimate the stability of the axillary pad in the axilla during single-crutch walking through kinematic analysis of the crutch position in the horizontal plane. [Subjects] The subjects were 19 healthy young males. [Methods] The subjects were instructed to walk 5 m in a straight line while using a single crutch. This was repeated 10 times. Repeated-measures analysis of variance and Tukey’s honest significance test were used to compare crutch angles across three time points during crutch stance (crutch contact, mid stance and crutch off) for each subject. [Results] A statistically significant effect of time was found in 17 of the 19 subjects. Sixteen of these 17 subjects rotated the crutch externally from crutch contact to crutch off. [Conclusion] External rotation of the crutch throughout the stance phase is important to enable the axillary pad to be held tightly against the chest wall. These results may lead to alterations of the instructions for crutch use and the prevention of falls.