•  
  •  

UKnowledge > College of Engineering > Research for Technology Development > PSMIJ > Vol. 6 (2025) > Iss. 1

 

Abstract

Modeling of the human body is widely utilized in the field of human–robot interaction, warranting the development of a simple model to measure and recognize the human body movements. To this end, a two-dimensional (2D) human body link model in the sagittal plane has been used to represent the human body with rotating joints and links connecting these joints. The joint positions can be determined by using the coordinates of a limited number of points on the links and estimated using a few sensor outputs when the links are of constant length. However, models with constant link lengths may result in calculation errors. Therefore, a human body link model with only the length of the thigh link considered to be a variable has been previously proposed by capitalizing on the changes in the apparent link length in the 2D link model. However, the minor change in apparent thigh length induces significant errors in joint positions. Therefore, in this study, we propose a human body link model wherein only the length of the upper-arm link is considered a variable to reduce errors while maintaining model simplicity. Although the actual length of the upper arm remains unchanged, the apparent length of the upper-arm link changes significantly in the 2D human body link model in the sagittal plane owing to the changes in the shoulder position caused by the height of the degrees-of-freedom of the shoulder. Consequently, the joint position errors can be reduced by changing the length of the upper-arm link. A comparison of the errors with respect to the joint positions obtained using the proposed and existing models with actual joint positions confirms that the proposed model can determine the joint positions more accurately. It was confirmed that the joint positions obtained using the proposed model were sufficiently accurate to estimate the state of the robot user. Validation with multiple participants revealed that the length of the upper body and upper-arm links have a significant impact on the joint position error. The validation further confirmed that the joint positions could be calculated with the same degree of accuracy even when the link lengths of the various body parts differed.

Creative Commons License

Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.

DOI

https://doi.org/10.13023/psmij.2025.06-01-01

Download

Share

COinS