# State of the Art: Bipedal Robots for Lower Limb Rehabilitation
## 3 Rehabilitation Application
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Type** & **Advantages** & **Disadvantages** & **Example** \\ \hline \multirow{2}{*}{Wearable exoskeleton robot} & Wearable, the range & Uncomfortable, & \\  & of use is wide & Rigid structure & BLEEX, HAL, ReWalk \\ \hline \multirow{2}{*}{Rehabilitation equipment} & Functional, Rehabilitation & \multirow{2}{*}{Bulky} & \multirow{2}{*}{Welwalk-1000, LOKOMAT} \\  & effect is good & & \\ \hline \multirow{2}{*}{Soft exoskeleton robot} & \multirow{2}{*}{Light quality, Unconstrained} & Auxiliary force is & \multirow{2}{*}{Exosuit} \\  & & & \\ \hline \multirow{2}{*}{Unpowered exoskeleton robot} & \multirow{2}{*}{Unpowered} & Structural design & \multirow{2}{*}{Exoboot} \\  & & is difficult & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Comparison of various types of rehabilitation robots. Figure 7: Advanced exoskeleton robot. (**a**) Soft exoskeleton robot; (**b**) Unpowered exoskeleton robot Exoboot. ((**a**) was reproduced with permission from [78]; (**b**) was reproduced with permission from [77], Copyright Nature, 2015.) For bipedal robots, the gait planning based on bionic kinematics requires the collection of human motion data. Since the assistance of exoskeleton robots is based on the accurate acquisition of human motion intent, these signal acquisition techniques can be applied to the control of exoskeleton robots. The current exoskeleton robot control methods are: manipulator control, force feedback control, EMG signal control, pre-programmed control, master-slave control, ZMP control, and sensitivity amplification control. The hybrid auxiliary limb (HAL) [71] (Figure 5b), developed by Japanese robot manufacturer Cyberdyne, is controlled based on the EMG signal. HAL is also the world's first bipedal skeleton robot that can be controlled by human minds. In 2013, the HAL bipedal exoskeleton robot received global safety certification in Japan. Obtaining a Global Certification means that HAL will be delivered to the market worldwide, which is good news for people with disabilities. ReWalk [79] (Figure 5c), designed and manufactured by Israel ReWalk, is adaptive, unlike other common exoskeletons or prostheses. It self-learns and walks at the habitual pace of the user with an intelligent control method. In 2017, [PERSON] proposed using the person as a part of the control of the exoskeleton robot by measuring the body's metabolism of the gas to obtain the real-time state of the human body [80]. Based on this, the control of exoskeleton robots was optimized. Figure 8 shows the operating principle of the entire system. This theory has raised the I man-machine cooperation of exoskeleton robots to a new level. The number of elderly people suffering from hemiplegia or paraplegia for whom walking is an inconvenience or impossibility is huge, and this number continues to rise. With an aging society, the number of elderly people will increase sharply in the future, and the number of elderly people incapacitated will inevitably increase. With the increase of these social needs, rehabilitation will become one of the important applications of the bipedal robot.