Yumeko Imamura

Motion-based design of elastic belts for passive assistive device using musculoskeletal model

We are developing a passive power assist supporter called Smart Suit Lite. Smart Suit Lite is a compact and lightweight power assist device that utilizes the elastic force of elastic belts. To design the Smart Suit Lite, we developed a motion-based assist method and an extended musculoskeletal model. The motion-based assist method was used to design the arrangements and properties of the elastic belts by utilizing the relation between the target motions and the corresponding muscle forces. To analyze the assistive forces provided by the elastic belts, skin segments that represent the surface of the human body features the extended musculoskeletal model and can reproduce changes in length of the body surface with changes in posture. In this study, we used the developed method to produce the Smart Suit Lite for care workers. Furthermore, through a trial experiment, we found that wear comfort was strongly correlated with the assistance perceived the user. Thus, we have improved the Smart Suit Lite from the aspect of wear comfort, and verified the enhancement of the assistance provided by the device. In user testing, 90% of the participants reported a decrease in load on the low back during care work.

New evaluation framework for human-assistive devices based on humanoid robotics

This paper presents the new application of a humanoid robot as an evaluator of human-assistive devices. The reliable and objective evaluation framework for assistive devices is necessary for making industrial standards in order that those devices are used in various applications. In this framework, we utilize a recent humanoid robot with its high similarity to humans, human motion retargeting techniques to a humanoid robot, and identification techniques of robot’s mechanical properties. We also show two approaches to estimate supporting torques from the sensor data, which can be used properly according to the situations. With the general formulation of the wire-driven multi-body system, the supporting torque of passive assistive devices is also formulated. We evaluate a passive assistive wear ‘Smart Suit Lite (SSL)’ as an example of device, and use HRP-4 as the humanoid platform. Graphical Abstract

Fundamental study on evaluation of KEIROKA(fatigue-reduction) technology in using UD shovel for removing snow by Musculo-Skeletal Dynamics Simulator

Our purpose in this study is to achieve an independent life and a social involvement for the elderly using KEIROKA (fatigue-reduction) Technology which makes it possible to improve the quality of chores and occupations by removing excessive strain and tiredness. Along the way, various assistant technologies for work and task supports have been suggested. However, they are used for evaluation of short-term effects and their design and assessment in a long-term standpoint are not performed. Therefore, final purpose in this research is to examine the possibility to evaluate KEIROKA(fatigue-reduction) Technology using Musculo-Skeletal Dynamics Simulator. So, experiments were performed to measure movements of subject using a conventional shovel with straight-line hilt and a UD shovel with flexural hilt by using three-dimensional motion analysis system and analyzed the physical strain caused by differences of shovels using Musculo-Skeletal Dynamics Simulator.

Verification of assistive effect generated by passive power-assist device using humanoid robot

We are developing a passive power assist supporter called Smart Suit Lite. Smart Suit Lite is a compact and lightweight power assist device that utilizes the elastic force of elastic belts, and its purpose is reduction of lumbar load. We have proposed the design method of Smart Suit Lite based on a digital human model and motion measurements. This paper presents the basic experiment using humanoid robot HRP-4C for verifying the design model of the elastic force and its assistive effect. In the experiment, the joint torques of the robot and the elastic force of Smart Suit Lite were measured. We observed the decrease of the chest torque by the assistive force during forward bending motion. Furthermore, the comparison between the simulation results and the experimental result is described.

Lumbar joint torque estimation based on simplified motion measurement using multiple inertial sensors

We estimate lumbar torque based on motion measurement using only three inertial sensors. First, human motion is measured by a 6-axis motion tracking device that combines a 3-axis accelerometer and a 3-axis gyroscope placed on the shank, thigh, and back. Next, the lumbar joint torque during the motion is estimated by kinematic musculoskeletal simulation. The conventional method for estimating joint torque uses full body motion data measured by an optical motion capture system. However, in this research, joint torque is estimated by using only three link angles of the body, thigh, and shank. The utility of our method was verified by experiments. We measured motion of bendung knee and waist simultaneously. As the result, we were able to estimate the lumbar joint torque from measured motion.

Verification of passive power-assist device using humanoid robot: Effect on bending and twisting motion

A passive power-assist supporter, called Smart Suit Lite, aims at reducing the lumbar load utilizing the tension of elastic belts. Its design method is based on a digital human model and motion measurements. This paper presents basic experiments using humanoid robot HRP-4 for verifying the design model of the suit. In the experiment, the joint torques of the robot and the elastic force of Smart Suit Lite were measured. We found that the decrease of the chest pitch torque during slow forward bending motion on the sagittal plane was consistent with simulation results. In addition, the effects for three-dimensional motion including chest pitching and yawing also indicated a similar tendency to the simulation. Because we performed quantitative evaluation of the effects by each part of the suit, these results are considered to provide useful information to the optimization of Smart Suit Lite.

Postural stabilization by trunk tightening force generated by passive power-assist device

We are developing a passive power-assist supporter called Smart Suit Lite, which is a compact and lightweight power-assist device that utilizes the restoring force of elastic belts. Smart Suit Lite is designed not only to support muscles but also to stabilize the torso similarly to a corset. However, because a corset is always tight around the waist, negative effects caused by long-term use has been pointed out. In contrast, the tightening force generated by Smart Suit Lite increases only when the wearer adopts a posture corresponding to higher load on the low back. In this research, we performed two basic experiments to evaluate the static balance ability of wearers. As a result, the standard deviation of the lumbar angle decreased by 32.1% on average in wearers with low stability.

Field Testing of the Influence of Assistive Wear on the Physical Fitness of Nursing-Care Workers

There are several problems involved with introducing assistive technologies, which amplify human physical strength or reduce fatigue, to actual environment. One of the problem is that there is the possibility that the muscular strength of the user decline due to the reduction of the physical burden associated with the work. Therefore, the changes in physical performance due to the use of the assistive devices need to be quantitatively evaluated. In this study, a four-week monitoring test (including a two-week trial period) was performed with a total of 30 nursing-care workers in a nursing home. The participants wore an assistive wear “Smart Suit Lite” for two weeks and their subjective fatigue and physical strength were evaluated over the course of the study. The results show that the feeling of fatigue was decreased in each of the subjects by an average of 16% as a result of using the assistive wear. However, there was no significant difference in the subjects’ physical fitness (back-muscle strength, grip strength, sitting–standing capability, standing long-jump ability, or one-legged standing ability), indicating that there was no decrease in physical strength due to the use of the Smart Suit Lite during normal work over two weeks.

Toward New Humanoid Applications: Wearable Device Evaluation Through Human Motion Reproduction

This chapter addresses a new application of humanoid robot for evaluation of wearable assistive devices. One of the issues for diffusion of assistive devices that have been developed recently is its objective and qualitative evaluation to validate its assistive effects. Human subject experiments that have frequently been used have several drawbacks such as heavy ethical procedures, repeatability and subjectivity coming from tests with questionnaires. A humanoid robot with human-like structure and shape has potential to be used as an “active mannequin.” By reproducing human motions based on a technique called retargeting, a humanoid robot can test wearable devices instead of a human. It has advantages as it can repeat the same motions to test the product under the same conditions, and it has no ethical risks. The largest advantage is its capacity of quantitative evaluation by measuring joint torques, which allows direct validation of supportive torque generated by the device. By taking an example of a supportive wear “Smart Suit Lite” supporting the user’s lower back by elastic bands, we will overview the evaluation framework of humanoid-based assistive device evaluation, including human motion retargeting, experimental device evaluation with humanoid HRP-4C, and validation of the accuracy of the results using an identification method.

Evaluation Framework for Passive Assistive Device Based on Humanoid Experiments

This study presents an enhanced framework for evaluating an assistive effect generated by a passive assistive device using a humanoid robot. The humanoid robotic experiments can evaluate wearable devices by measuring the joint torque, which cannot be measured directly from the human body. In this paper, we introduce an “assistive torque estimation map” as an efficient means for estimating the supportive torque within the range of motions by interpolating the measured joint torques and joint angles of the robot. This map aims to estimate the supportive torques for complex motions without conducting humanoid experiments or human-subject experiments with these motions. We generated an estimation map for an actual assistive suit that decreases the load on the lumbar region and we verified the validity of the proposed method by experimentation. In addition, the geometric simulation model of the assistive suit was validated based on the proposed experiments by using the humanoid robot HRP-4. The proposed framework is expected to lead to an efficient design of such assistive devices so that fewer human-subject experiments need to be conducted.