# Enhancing Robotic-Assisted Lower Limb Rehabilitation Using Augmented Reality and Serious Gaming
## 4 Proposed Methodology for the Lower Limb Rehabilitation Treatment
### Sensors Placement  
To monitor the three joints, three sensors were used: two twin-axis goniometers (each with two channels for simultaneously measuring angles in two planes) for the hip and ankle joints and one single-axis goniometer for the knee joint. The placement of the sensors is detailed in Table 2 and illustrated in Figure 12.  
The data corresponding to each type of movement are transmitted individually through separate channels of the device, allowing for independent analysis, processing, and transmission to the HoloLens. Therefore, for the hip, twin-axis goniometers measure angles in two planes simultaneously, with the data being transmitted on channels 1 and 2. The knee angle is transmitted on channel 3, and the ankle angles, measured by other twin-axis goniometers, are transmitted on channels 5 and 6. Figure 12: The placement of twin-axis goniometers at the hip and ankle and a single-axis goniometer at the knee. the angles of each lower limb joint during the rehabilitation process and record the evolution for each signal into a database for offline analysis. Due to its real-time amplitude measurement capabilities, the Biometrics measurement system is used to provide data regarding the position of the lower limb during the rehabilitation procedure and serious gaming application. The control system of the robot uses these data to double-check the actual position of the patient's lower limb in order to determine inaccuracies between the motor position and the patient's leg. At the same time, the data from the Biometrics sensors are used as input data for the HoloLens application and used to graphically represent the position of the patient's lower-limb and the game evolution. The rehabilitation system benefits from a graphical interface that provides real-time representation of the data from the goniometers (Figure 13). \begin{table}
\begin{tabular}{c c c} \hline \hline
**Joint** & **Movement** & **Placement of Sensors** \\ \hline Hip & \begin{tabular}{c} Flexion/Extension and \\ Abduction/Adduction \\ \end{tabular} & \begin{tabular}{c} The lower part (Figure 11) of the twin-axis goniometer should be attached to the lateral side of the thigh, just below the hip joint. The upper part should be attached to the pelvis, ensuring that the goniometer can capture both movements \\ \end{tabular} \\ Knee & \begin{tabular}{c} Flexion/Extension \\ Flexion/Extension and \\ Abduction/Adduction: \\ \end{tabular} & \begin{tabular}{c} Using a single-axis goniometer, the sensor should be attached as follows: the upper part to the thigh above the knee and the other part to the lower leg (shin) below the knee joint. \\ \end{tabular} \\ Ankle & \
\begin{tabular}{c} Flexion/Extension and \\ Abduction/Adduction: \\ \end{tabular} &
\begin{tabular}{c} The upper part of the twin-axis goniometer should be attached to the lower leg (shin) just above the ankle. The lower part should be attached to the foot, just below the ankle joint, ensuring it captures both flexion/extension and inversion/eversion. \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Sensor’s placement for each joint. Figure 13: The graphical output from the Biometrics device (8 input channels), where the angles measured at the hip are transmitted on channels 1 and 2, the knee on channel 3, and the ankle on channels 5 and 6. Channel 4 is not used, while channels 7 and 8 remain inactive. Determining the Number of Movements per Set and Establishing Optimal Rest Intervals During Treatment  
In order to address these aspects effectively, a comprehensive strategy was established to determine the appropriate number of movements per set and the optimal rest intervals between sets. This strategy was based on the medical protocol outlined in [37], which was developed in close collaboration with the physicians involved in the project.