A Disturbance Rejection Control Method for an Inverted Pendulum Mobile Robot on Slopes

When a two-wheeled inverted pendulum (TWIP) mobile robot moves, it can be confronted with diverse disturbances including such as abrupt change of ground friction and slope angle which deteriorates its mobility and postural stability. If the adverse effect from the environmental disturbances is not attenuated successfully, the mobile robot can go to unsafe situations finally leading to rollovers and turnovers. To keep the safety and improve the postural stability regardless of the terrain conditions, we propose a TWIP-compatible disturbance rejection control method combining the nonlinear disturbance observer (NDOB) for the wheel torque compensation and the pitch reference generator to get over the limit of underactuated system. Through the simulative and experimental results, the effectiveness of the proposed method is confirmed.