*Article* **Human Joint Torque Estimation Based on Mechanomyography for Upper Extremity Exosuit**

**Yongjun Shi <sup>1</sup> , Wei Dong <sup>1</sup> , Weiqi Lin <sup>1</sup> , Long He <sup>2</sup> , Xinrui Wang <sup>2</sup> , Pengjie Li <sup>2</sup> and Yongzhuo Gao 1,\***


**\*** Correspondence: gaoyongzhuo@hit.edu.cn

**Abstract:** Human intention recognition belongs to the algorithm basis for exoskeleton robots to generate synergic movements and provide corresponding assistance. In this article, we acquire and analyze the mechanomyography (MMG) to estimate the current joint torque and apply this method to the rehabilitation training research of the upper extremity exosuit. In order to obtain relatively pure biological signals, a MMG processing method based on the Hilbert-Huang Transform (HHT) is proposed to eliminate the mixed noise and motion artifacts. After extracting features and forming the dataset, a random forest regression (RFR) model is designed to build the mapping relationship between MMG and human joint output through offline learning. In addition, an upper extremity exosuit is constructed for multi-joint assistance. Based on the above research, we develop a torque estimation-based control strategy and make it responsible for the intention understanding and motion servo of this customized system. Finally, an actual test verifies the accuracy and reliability of this recognition algorithm, and an efficiency evaluation experiment also proves the feasibility for power assistance.

**Keywords:** joint torque estimation; upper extremity exosuit; mechanomyography signal processing; rehabilitation training; MMG; human movement assistance
