“…Several methods have been put forward to minimize the influence of arm position changes in past studies, such as the multi-position classifier (Geng et al, 2012 ), cascade classifier (Geng et al, 2017 ), dynamic training (Shahzad et al, 2019 ), position-invariant features (Asogbon et al, 2020 ), and other classification algorithms. Multi-modal signals are usually needed for many methods, such as the accelerometry (ACC) signal, the near-infrared spectroscopy (NIRS) (Guo et al, 2015 , 2017 ), electroencephalography (EEG) (Leeb et al, 2011 ), FMG (Ferigo et al, 2017 ; Prakash et al, 2020a , b ; Huang et al, 2021 ), and some industry sensors used for human-centered robotic systems (Huang et al, 2020 ; Yan et al, 2021 ). Among these signals, the ACC is the most commonly used signal for the complementary of EMG (Geng et al, 2012 ; Huang et al, 2015 ; Shahzad et al, 2019 ), since the tri-axis ACC signal could provide information about arm position.…”