## 4 Results
### Track Tracking Experiments under Different Admittance Conditions  
\(\bullet\)No admittance:  
Figure 11a is the comparison result of track tracking experiment of subject H1 (male, 24 years old, weight/60 kg, height/1.70 m) under different control strategies. It can be seen that the position control accuracy of the ASMVA controller is better than that of GSMC controller. The RMSE (Root mean square error) and PE (Peak error) of track tracking of knee-joint with ASMVA are 0.11 degrees and 0.54 degrees respectively, while those with GSMC are 0.28 degrees and 0.56 degrees respectively. Therefore, the control accuracy of the proposed ASMVA is higher than that of the GSMC. Table 4 summarizes the statistical results of track tracking experiments conducted by three subjects, which shows that the proposed ASMVA control algorithm can ensure the track tracking accuracy of patients' passive training mode. Figure 10: The relationship between the angular displacement of the knee joint and standard interaction torque in the knee joint. \begin{table}
\begin{tabular}{c c c} \hline \hline \multirow{2}{*}{**Subject**} & \multicolumn{2}{c}{**Linear Equation**\(y\)**=_ax+\(b\)_} \\  & **a** & **b** \\ \hline H1 (male, 24 years old, weight/60 kg, height/1.70 m) & \(-\)0.21946 & 7.64923 \\ H2 (male, 23 years old weight/65 kg, height/1.75 m) & \(-\)0.22056 & 8.62145 \\ H3 (female, 25 years old, weight/51 kg, height/1.60 m) & \(-\)0.21864 & 6.21456 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Results of the human-exoskeleton interaction measurement experiment. Figure 9: Measured data. (**a**) Motion trajectory of the hip joint (black line) and knee joint (red line). (**b**) Measured interaction torque of the knee joint. * Fixed admittance: Figure 11b-d show the track tracking experimental results of subject H1 (male, 24 years old, weight/60 kg, height/1.70 m) under the admittance configurations of large admittance, medium admittance, and small admittance, respectively. Table 5 shows the track tracking error under different admittance configurations in condition of fixed admittance. In the small admittance configuration, RMSE is 2.54 degrees, PE is 3.97 degrees, while in the medium admittance configuration and large admittance configuration, RMSE is 1.27 degrees and 0.88 degrees, PE is 1.99 degrees and 1.31 degrees, respectively. It can be seen that with the increasing of admittance parameters, the deviation between the desired training trajectory and the actual training trajectory will be smaller. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Subject** & **Controller** & **RSME/degrees** & **PE/degrees** \\ \hline H1 (male, 24 years old, weight/60 kg, height/1.70 m) & ASMVA & 0.11 & 0.54 \\ GSMC & 0.28 & 0.56 \\ H2 (male, 23 years old weight/65 kg, height/1.75 m) & ASMVA & 0.11 & 0.65 \\ GSMC & 0.35 & 0.76 \\ H3 (female, 25 years old, weight/51 kg, height/1.60 m) & ASMVA & 0.10 & 0.57 \\ GSMC & 0.25 & 0.65 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Experimental results of track tracking experiment with no admittance. Figure 11: Experimental results of track tracking under different admittance configurations. (**a**) Infinite admittance parameters. (**b**) Small admittance. (**c**) Medium admittance. (**d**) Large admittance. * Variable admittance:  
Figure 12 shows the experimental results of H1 (male, 24 years old, weight/60 kg, height/1.70 m) under the condition of variable admittance. Figure 12a shows the comparison result between measured interaction torque of the knee joint and the estimated active torque of the knee joint. Movement intention of the subject can be obtained according to the estimated active torque of the knee joint, which is shown in Figure 12b. The changes in stiffness and damping of admittance controller during this experiment can be seen in Figure 12c, which indicates that the admittance parameters will change with change in the wearer's active joint torque, and when the active joint torque increases, the admittance parameters will also increase.