Advanced control methods for two-wheeled mobile robots

A complete overview in recent years, concerned with the classification, control methods, applications and future works for two-wheeled mobile robot (TWMR), is presented. There have been three main types of TWMRs: input coupling, without input coupling and reaction wheel. For the second model (TWMR without input coupling), a variety of control methods have been proposed from the classical method PID to advanced methods such as sliding mode control, adaptive control, robust control, back-stepping, and fuzzy inference system based control. There have been vital applications of TWMRs, for example, Segway, E-scooter and TWMR based cars. There have been some unsolved challenging control problems, such as controllability, moving on non-flat surface, inclined path, control of TWMRs with input-coupling, control of TWMRs with reaction wheel and safety.