Algorithm 1 Active tracking control

Require:  ${\Gamma }_{EMG1,...,EMG8}$: EMG vector; $\dot{x_{ref}}$: velocity reference; $\overrightarrow{\theta }$: joint angles.

1:  Calculate $\left|\right|\overrightarrow{x_m}\left|\right|$ and $\left|\right|\overrightarrow{x_{ref}}\left|\right|$.

2:  Calculate $e\left(t\right)$ = $\left|\right|\overrightarrow{x_{ref}}\left|\right|$−$\left|\right|\overrightarrow{x_m}\left|\right|$.

3:  if $e\left(t\right)\ge 1$ then

4:  $\hspace{1em}U{\left(t\right)}_{ac}={\dot{x}}_{ref}\times sng$; go to 1.

5:  else

6:   $\hspace{1em}U{\left(t\right)}_{ac}=0$

7:  end if

8:  if Motion direction change then

9:   Update $\overrightarrow{x_{ref}}$ and $sng$. If the intention is motion 1, $sng=1$, otherwise, $sng=-1$.

10:  end if

11:  go to 1.