Radar-Based Human Motion Measurement for Clothing Motion Comfortability Evaluation 

Background

Clothing mobility and comfortability are important in daily life, sports, work, nursing care, and outdoor activities. Pants are particularly relevant because they can affect hip, knee, leg, and trunk movements during lower-limb motions such as ascending steps and squatting.

Conventional methods for evaluating clothing comfortability include subjective evaluations, clothing pressure sensors, motion capture, and electromyography. These methods are useful, but clothing pressure sensors may affect wearability and motion depending on sensor placement and wiring, while motion capture requires markers and controlled measurement environments. In addition, when markers are attached to the clothing surface, the measured motion does not always directly represent the motion of the body parts inside the clothing.

Microwave and millimeter-wave radar can exploit the penetration of radio waves through clothing and measure velocity components of body parts from outside the worn clothing. Therefore, it may be useful for evaluating motion differences caused by pants under natural conditions, without attaching sensors or markers to the clothing or the body.

Research Objectives

This research aims to evaluate how differences in pants type or design affect human motion using non-contact radar measurement.

Main topics include:

• Detection of motion differences during step-ascending caused by differences in pants

• Non-contact measurement of body-part velocity through clothing

• Classification of motion differences using Doppler radar spectrograms

• Extraction of velocity and acceleration parameters of body parts such as the legs and head

• Analysis of relationships between pants mobility and human motion features

• Analysis of relationships between motion differences and body dimensions such as knee and thigh circumference

• Objective evaluation indices complementing subjective comfortability assessment

• Functional evaluation of clothing under conditions close to daily activities

Related Work

Our previous work has investigated Doppler radar measurement of step-ascending motions while participants wore pants with different expected ease of movement, such as denim pants and trekking pants.

In the early study, Doppler radar spectrograms obtained during step-ascending motions were analyzed using deep learning to classify motion differences caused by different pants. The results showed the possibility of classifying motion differences between denim pants and trekking pants with high accuracy.

In our 2024 IEEE Sensors Letters paper, velocity and acceleration parameters extracted from Doppler radar measurements were used to evaluate the feasibility of sensing motion comfortability of pants. The study compared step-ascending motions while participants wore denim pants and trekking pants. The results showed a significant difference in peak leg velocity, and differences in leg velocity were related to knee and thigh circumference. This research aims to establish a new interdisciplinary field connecting apparel science and radar sensing.

Research Perspective

A key feature of this research is that clothing mobility is evaluated not only through subjective impressions but also through velocity information obtained from body parts while the participant is actually wearing the clothing.

Clothing pressure measurements are useful for evaluating local pressure and contact conditions between the clothing and the body. Motion capture can measure detailed movements of the body or clothing surface with high accuracy. In contrast, Doppler radar can obtain velocity information of body parts from outside the clothing by exploiting the ability of radio waves to penetrate clothing.

This enables evaluation of motion differences caused by pants without attaching sensors or markers and with less disturbance to natural movement. Another distinctive feature is the possibility of capturing motion changes of the lower limbs and trunk inside the clothing, rather than only the appearance or surface displacement of the clothing.

Selected Publications

• Kenshi Saho, Toshiyuki Hoshiga, Naoyuki Takashima, Masaaki Iwata, and Muneharu Inagaki, “Feasibility Study of Radar-Based Sensing of Motion Comfortability of Pants: Fundamental Experiments to Evaluate Motion Differences in Wearing Denim and Trekking Pants,” IEEE Sensors Letters, vol. 8, article no. 3504404, 2024.

• Toshiyuki Hoshiga, Kenshi Saho, Naoyuki Takashima, Masaaki Iwata, and Muneharu Inagaki, “Classification of Motions while Ascending a Step Caused by Differences of Pants Using Doppler Radars,” IEEE LifeTech 2022. 

Keywords

pants motion comfortability, pants mobility, clothing comfortability, clothing mobility, denim pants, trekking pants, step-ascending motion, stair ascent, Doppler radar, microwave radar, penetration through clothing, radio-wave penetration, non-contact measurement, velocity measurement, acceleration measurement, radar spectrogram, convolutional neural network, CNN, human motion measurement, clothing engineering, product evaluation, sportswear, outdoor wear