# A Motion Control of Soft Gait Assistive Suit by Gait Phase Detection Using Pressure Information
## 5 Evaluation Experiments
### Electromyogram Measurement  
#### 5.3.1 Experimental Method  
We verified whether the gait assistive suit is effective for decreasing activity in the trainee's muscles. We measured and compared the muscular activities of the assisted walking and walking without the suit. Note that the measured data of the muscular activities is used for just evaluating and not for controlling the gait assistive suit.  
Figure 15: RCF PARM pressure trajectories of the 90 and 140 BPM walking. The horizontal axis is time (s), and the vertical axis is pressure (kPa). The solid and dashed lines are the measured pressure and the reference pressure. (**a**) 90 BPM walking using the conventional method. (**b**) 140 BPM walking using the conventional method. (**c**) 90 BPM walking using the proposed method. (**d**) 140 BPM walking using the proposed method.  
In this experiment, the gait assistance only uses the novel control method, and the conventional control method [18] for comparison is not used, since the difference between the novel and conventional control methods is the detection algorithm. These precisions were confirmed by the result in Section 5.2. Therefore, the purpose of this experiment is to confirm the effectiveness of the proposed gait assistive suit which achieves regular phase detection.  
Five healthy males in their 20 s and 30 s walked on the treadmill, and their parameters are shown in Table 4. EMG signals were recorded by EMG sensors (Delsys Inc., Bagnoli desktop EMG systems). We assumed that the walking of the trainee is bilateral symmetry. The electrodes are attached to the right leg, and these positions are on vastus lateralis (RTF), semitendinosu (RTB), gastrocnemius (RCB) and tibialis anterior (RCF). We recorded the EMG signals and calculated their RMS values \(J_{r}\) (V) in one cycle motion as:  
\[J_{r}=\sqrt{\frac{1}{T_{c}}\int_{0}^{T_{c}}EMG_{(t)}^{2}dt} \tag{11}\]  
where \(EMG\) (V) is a measured EMG signal. Frequency components of the EMG signal under 25 Hz are cut off by a high-pass filter to avoid a noise effect from cable swinging et al. The RMS value in maximum voluntary contraction (MVC) state is also measured in each muscle for normalization. The normalized RMS value is %\(MVC\) (%), and is calculated as:  
\[\%MVC=J_{r}/J_{r}^{MVC}\times 100 \tag{12}\]  
where \(J_{r}^{MVC}\) is the RMS value in MVC state, and %\(MVC\) is calculated in each electrode channel. The sensor positions and the clinical test method of measuring MVC state are determined based on the SENIAM project [38]. The metronome is used for equalizing the walking rate, and its tempo is adjusted in each trainee. The trainee walks on the treadmill 40 steps of 20 cycles with its speed of 5.0 km/h in each trial. The pressure in the CB PARMs is determined by using the procedure in Section 3.3. The experimental procedure is as follows;  
1. Measuring the RMS value in MVC state \(J_{r}^{MVC}\).
2. Resting 5 min.
3. EMG measurement of the walking without the suit.
4. Wearing the suit.
5. Practicing of the assisted walking.
6. Resting 10 min.
7. EMG measurement of the asssited walking.  
5 to 10 min resting time is set between the measuring steps to avoid muscle fatigue of the trainee. In the practicing step, the trainee is required to learn how to walk with the assist force provided from the suit. The targets of the practicing step are 100% success rate of the phase detection and learning of the relaxed walking using the assist force. Each EMG data is measured in one trial respectively in procedure 1, 3 and 7.  
\begin{table}
\begin{tabular}{l c c c} \hline \hline  & **Height (m)** & **Weight (kg)** & **Pressure in CB PARMs (kPa)** \\ \hline Trainee 1 & 1.71 & 72 & \(1.5\times 10^{2}\) \\ Trainee 2 & 1.76 & 73 & \(1.5\times 10^{2}\) \\ Trainee 3 & 1.75 & 74 & \(1.0\times 10^{2}\) \\ Trainee 4 & 1.70 & 54 & \(1.0\times 10^{2}\) \\ Trainee 5 & 1.61 & 68 & \(1.0\times 10^{2}\) \\ \hline \hline \end{tabular}
\end{table}
Table 4: Parameters of the trainees.