Due to an increasingly serious aging society and a large number of disabled civilians, the number of residents who need rehabilitation therapy is increasing rapidly in the past few years, but the rehabilitation therapists/treatments are in short supply in reality. In recent years, with the in-depth research and technology development of rehabilitation robots, this contradiction is expected to be overcome. In this paper, the modeling mechanisms of rehabilitation robots are firstly introduced based on the pneumatic artificial muscle drive, motor drive, and cable drive, respectively. Then some typical methodologies are presented to deal with various types of control constraints, namely the nonlinearity, the parameter uncertainty, the fatigue, and the time-delay, etc. Moreover, the advantages and disadvantages of some existing control approaches and driving modes are discussed in depth, including some notable experimental results. The key challenges and shortcomings of rehabilitation robots are analyzed and summarized, and the future development of rehabilitation robots has been prospected finally.
