## 5 Experiment
### Experimental Results  
Table 3 reports the averaged operational efficiency without a load for each condition and surface. The results of nonparametric two-way ANOVA for the operational efficiency show statistically significant differences between the surfaces (F = 128.61, \(p<0.01\)) and between the methods (F = 16.11, \(p<0.01\)), while interaction between these factors was also observed (F = 3.48, \(p<0.01\)). Due to the significant differences, multiple comparisons tests for the methods were performed. The averaged operational efficiencies for OAR and DOB were significantly different from the ones for the case without assistance and with the default method, while there was no evidential difference between OAR and DOB.  
The averaged operational efficiency with load of 10 kg for each condition and surface is reported in Table 4. The results of nonparametric two-way ANOVA for the operational efficiency indicate statistically significant differences between the surfaces (F = 202.15, \(p<0.01\)) and between the methods (F = 52.47, \(p<0.01\)), while interaction between these factors was also observed (F = 5.45, \(p<0.01\)). The results of multiple comparison tests for the methods illustrate a significant difference between DOB and the other methods.  
The results of nonparametric one-way ANOVA and multiple comparison tests for the dimensionless walking speed indicate that there were almost no significant differences in the dimensionless walking speed between the four methods for all of the surfaces, except that the dimensionless walking speed for DOB (\(V_{D}=0.26\)) was significantly different from the ones for the case without assistance (\(V_{D}=0.20\)) and with default assistance (\(V_{D}=0.20\)) while walking upon the slope (\(p=0.016\) without the load and \(p<0.01\) with the load).  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Environment** & **Method** & **No Assistance** & **Default** & **OAR** & **DOB** \\ \hline \multirow{3}{*}{Flat} & Indoor & 0.273 & 0.468 & 0.476 & 0.416 \\ \cline{2-6}  & Tile & 0.306 & 0.421 & 0.486 & 0.540 \\ \cline{2-6}  & Sand & 0.110 & 0.249 & 0.392 & 0.552 \\ \hline \multirow{3}{*}{Flat} & Indoor & 0.197 & 0.350 & 0.367 & 0.388 \\ \cline{2-6}  & Tile & 0.161 & 0.277 & 0.415 & 0.487 \\ \cline{2-6}  & Sand & 0.119 & 0.214 & 0.347 & 0.461 \\ \hline \multirow{3}{*}{Slope} & Upwards & 0.038 & 0.141 & 0.212 & 0.352 \\ \cline{2-6}  & Downwards & 0.065 & 0.178 & 0.288 & 0.451 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Averaged operational efficiency with a load of 10 kg.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Environment** & **Method** & **No Assistance** & **Default** & **OAR** & **DOB** \\ \hline \multirow{3}{*}{Flat} & Indoor & 0.319 & 0.505 & 0.539 & 0.504 \\ \cline{2-6}  & Tile & 0.327 & 0.461 & 0.544 & 0.552 \\ \cline{2-6}  & Sand & 0.166 & 0.321 & 0.450 & 0.591 \\ \hline \multirow{3}{*}{Flat} & Indoor & 0.272 & 0.520 & 0.609 & 0.557 \\ \cline{2-6}  & Tile & 0.287 & 0.439 & 0.619 & 0.516 \\ \cline{2-6}  & Sand & 0.179 & 0.350 & 0.455 & 0.538 \\ \hline \multirow{3}{*}{Slope} & Upwards & 0.052 & 0.361 & 0.461 & 0.555 \\ \cline{2-6}  & Downwards & 0.111 & 0.381 & 0.458 & 0.458 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Averaged operational efficiency without load.