Interval Type-2 Fuzzy Logic Modeling and Control of a Mobile Two-Wheeled Inverted Pendulum

This paper presents an integrated interval type-2 fuzzy logic approach that simultaneously models and controls an underactuated mobile two-wheeled inverted pendulum (MTWIP), which suffers from modeling uncertainties and external disturbances. The control objective is to attain the desired position and direction while keeping the MTWIP balanced. It is achieved by integrating four interval type-2 fuzzy logic systems (IT2 FLSs): the first IT2 FLS describes the dynamics of the MTWIP using a Takagi-Sugeno model, the second IT2 FLS controls the balance of the MTWIP using also a Takagi-Sugeno model, and the third and fourth IT2 FLSs control its position and direction, respectively, using a Mamdani model. A linear matrix inequality based design approach is also proposed to guarantee the stability of the balance controller. The proposed approach is compared with a type-1 FLS in real-world experiments. All results demonstrate that the IT2 FLS outperforms the type-1 FLS, especially under modeling uncertainties and external disturbances.