Akihito Ito

Relative movement evaluation between developed distributed-type tactile sensor and the contacting object

This paper describes an output algorithm that measures forces and moment acting on a developed distributed-type tactile sensor and evaluates relative movement with the contacting object. To realize advanced manipulation, it is necessary to acquire forces and moments acting on the fingertips of the robot hand; it is also necessary to evaluate the relative movement between the contacting object and the sensor. An output algorithm for evaluating the relative movement for developed tactile sensor was created whose effectiveness was shown by experiments.

Quantitative evaluation of unrestrained human gait on change in walking velocity.

In human gait motion analysis, which is one useful method for efficient physical rehabilitation to define various quantitative evaluation indices, ground reaction force, joint angle and joint loads are measured during gait. To obtain these data as unrestrained gait measurement, a novel gait motion analysis system using mobile force plates and attitude sensors has been developed. On the other hand, a human maintains a high correlation among the motion of all joints during gait. The analysis of the correlation in the recorded joint motion extracts a few simultaneously activating segmental coordination patterns, and the structure of the intersegmental coordination is attracting attention to an expected relationship with a control strategy. However, when the evaluation method using singular value decomposition has been applied to joint angles of the lower limb as representative kinematic parameters, joint moments related to the rotational motion of the joints have not yet been considered. In this paper, joint moments as kinetic parameters applied on the lower limb during gait of a normal subject and a trans-femoral amputee are analyzed under change in walking velocity by the wearable gait motion analysis system, and the effectiveness for quantitatively evaluate the rotational motion pattern in the joints of the lower limb by using joint moments is validated.

Motion control of parallel manipulator using pneumatic artificial actuators

In this paper, we describe the motion control of a parallel manipulator with two degrees of freedom. The parallel manipulator uses three pneumatic artificial actuators. We adopted the minimum number of pneumatic artificial actuators that are required to move a joint with two degrees of freedom because this manipulator is applied to the joint of a robot hand. It is known that the relationship between the inner pressure and contraction ratio of pneumatic artificial actuators is highly nonlinear and includes a hysteresis characteristic. Therefore, in this study, we perform motion control using a control system with integrated hysteresis compensation.

Structural optimization of the thin-type four-axis force/moment sensor for a robot finger using response surface methodology and desirability function

A multi-axis force/moment sensor, which can measure force and moment, is helpful for robotic force control. However, the smallest multi-axis force/moment sensor has excessive height, which restricts postures in tasks by a robot hand. Therefore, we aim to optimize the structure of the thin-type four-axis force/moment sensor that we developed, which can measure the twisting moment on the finger cushion of a robot hand as if it were human, including strain gauge. As a result of applying structural optimization techniques using response surface methodology and desirability function on the four-axis force/moment sensor by finite element analysis, we obtained optimum design variables and validated the effectiveness of the proposed techniques.

Characteristics of tactile sensor and movement detection of attached object

To realize a dexterous robot hand, we must acquire information at the robots fingertips. A tactile sensor has been developed for dexterous robot hands. Since this tactile sensor consists of multiple three-axis force sensors with strain gauges, it enables to get force and torque information at robots fingertips. In this paper, the static characteristics of the three-axis force sensor that is a part of the tactile sensor are demonstrated, and the best experimental method to obtain accurate and precise force values is proposed. Furthermore, theoretical and experimental results of attached object movement detection with this tactile sensor are described in this paper.

Estimation of joint center and measurement of finger motion by inertial sensors

The authors developed a wearable finger motion measurement system using inertial and geomagnetic sensors. Using this system, motion and posture of the hands and fingers can be measured. However, the joint center and segment axis cannot be accurately measured in a previous study using the sensors. Therefore, the authors proposed a method of estimating the joint center and segment lengths. This method utilizes the fact that the calculation formula of the rotational acceleration in the sensors coordinate system is the vector product. However, because the vector product is irreversible, the rotation center was calculated by using a position vector placed on an intersection line of two planes constituted by rotational acceleration. As a result of the verification, estimation error was small. In addition, finger motion was measured using posture measurement and rotation center estimation. This measured motion, joint angle and segment lengths estimated by the finger motion measurement system were compared with a motion capture system. As a result, the initial MP and PIP joint angles had some differences, but there was no difference for the MP and PIP joint angles during movement and the other joint angles. Therefore, we need to improve the estimation method of the PIP and DIP joint centers.

Characterization and performance evaluation of a vertical seismic isolator using link and crank mechanism

In recent years, various seismic isolators have been developed to prevent earthquake damage to valuable art and other rare objects. Many seismic isolators only defend against horizontal motions, which are the usual cause of falling objects. However, the development of a seismic isolator designed for vertical vibration is necessary since such great vertical vibration earthquakes as the 2004 Niigata Prefecture Chuetsu Earthquake have occurred, and their increased height characteristics are undesirable. In this study, we developed a vertical seismic isolator that can be installed at a lower height and can support loads using a horizontal spring without requiring a vertical spring. It has a mechanism that combines links and cranks. The dynamic model was proposed and the frequency characteristics were simulated when the sine waves were the input. Shaking tests were also performed. The experimental value of the natural frequency was 0.57 Hz, and the theoretical values of the frequency characteristics were close to the experimental values. In addition, we verified this vertical seismic isolators performance through shaking tests and simulation for typical seismic waves in Japan. We verified the seismic isolations performance from the experimental result because the average reduction rate of the acceleration was 0.21.

Kinematic analysis of low dimensional structure in walking and running

Humans walk and run at various speeds by coordinating their whole-body movements skillfully, where they regulate the movements in accordance with the speed. However, it remains unclear what kinds of locomotion parameters they regulate and how to regulate the parameters. In the present study, to clarify the human strategy for regulating the whole-body movements in accordance with the speed, we measured human joint angles on sagittal plane during walking and running and analyzed the measured data by extracting low dimensional structure of the joint movements using singular value decomposition. Our results suggest a formation mechanism of human gaits, which contributes to elucidating the adaptation mechanism of human locomotion.

Measurement of rehabilitation in thumb MP joint subluxation due to rheumatoid arthritis.

As treatment for subluxation due to rheumatoid arthritis (RA), rehabilitation by hand therapy is one option, but the number of therapist is not sufficient. Therefore, a device for rehabilitation of thumb metacarpophalangeal (MP) joint subluxation has been developed. To improve the device, it is necessary to measure in close proximity to the actual rehabilitation. Therefore, the authors tried to measure two kinds of rehabilitation by using motion capture and a contact force sensor. To measure rehabilitation movements, three markers were attached to the metacarpal bone, six markers were attached to each side of the interphalangeal (IP) joint, MP joint and proximal phalanx of the right thumb of the subjects, and a finger model was created by these markers. Further, three markers were placed on the left index of the therapist, and force direction was calculated by these markers. Measurement was conducted on healthy subjects, Rehabilitation was performed by the person who is not a therapist, but received the guidance of the doctor who is coauthor. As a result, the authors could measure rehabilitation by hand therapy, force, point of action and displacement. The results suggest that rehabilitation with traction twice as efficient as that without traction. Furthermore, it was found that rehabilitation is possible with calculated force, and the force is reproducible by the actuator in the device.

Dynamic Analysis for Golf Swing using of Mode Synthetics Method for Suggesting an Optimal Club

Abstract: Advance of measurement system permits the measurement of high accuracy data. This study proposes analysis of shaft movement using this system. Firstly, we made a shaft model using finite element method and a club head model as concentrated mass. Secondly, we reduced amount of calculation by applying mode synthetics method. Input data for simulation is inertia force and torque calculated from swing data that is measured by motion capturing system and is treated data manually. Finally, we simulated shaft movement using these data, we cloud repeat shaft movement of face direction and toe direction.