2. rOBOTic anKle–FOOT rehaBiliTaTiOn sYsTeM The PKU-RARS (shown in Figure 1) is a platform-based ankle– foot device for robotic rehabilitation performing PNF stretching on ankle plantar flexors spasticity (Zhou et al., 2015). The proposed device can be functionally divided into two parts: the graphical user interface and the hardware (shown in Figure 2). To ensure the safety while using the system, protection mechanisms on the control system and graphical user interface, mechanical stops, and emergency switches are redundantly designed in our system.