AUTHOR=Tang Biwei , Peng Yaling , Luo Jing , Zhou Yaqian , Pang Muye , Xiang Kui 

TITLE=Cost Function Determination for Human Lifting Motion via the Bilevel Optimization Technology

JOURNAL=Frontiers in Bioengineering and Biotechnology

VOLUME=Volume 10 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/bioengineering-and-biotechnology/articles/10.3389/fbioe.2022.883633

DOI=10.3389/fbioe.2022.883633

ISSN=2296-4185

ABSTRACT=Investigating the optimal control strategy involved in human lifting motion can provide meritorious insights on  designing and controlling wearable robotic devices to release human low-back pain and fatigue. However, determining the latent cost function regarding to this motion remains challenging due to  complexities of human central nervous system. Recently, it has been discovered that the underlying cost function of a biological motion can be identified from an inverse optimization control (IOC) issue which could be handled via the bilevel optimization technology. Inspired by this discovery, this paper dedicates to studying the underlying cost function of human lifting task through the bilevel optimization technology. To this end,  a nested bilevel optimization approach is developed red by integrating particle swarm optimization (PSO) with the direction collocation (DC) method.  The upper level optimizer leverages  PSO to optimize weighting parameters among different predefined  performance criteria in the cost function, while minimizing the kinematic error between the experimental data and the result predicted from the lower-level optimizer. The lower-level optimizer implements the DC method to predict human kinematic and dynamic information based on the human musculoskeletal model inserted into OpenSim. Followed after a benchmark study, the developed method is then evaluated by experimental tests over different subjects. The experimental results reveal that the proposed method is effective at finding the cost function of human lifting task. Thus, the proposed method could be regarded as a paramount alternative in the predictive simulation of human lifting motion.