Abstract
Stable motion of differential-drive mobile robots on uneven surfaces remains a challenging control problem because local variations in rolling resistance and wheel–terrain interaction generate asymmetric traction forces, trajectory deviation, and heading instability. This study investigates a dual-motor mobile robot in which the left and right driving wheels are actuated independently and coordinated through a coupled control structure that simultaneously regulates linear speed and suppresses yaw motion. A control-oriented nonlinear dynamic model is developed by combining the longitudinal and yaw dynamics of the platform with first-order actuator models and resistance terms that represent uneven-terrain effects through side-dependent rolling losses. Based on this model, a coordinated control law is formulated to redistribute the control effort between the two drives in response to both speed and angular-velocity errors. Numerical experiments are carried out for nominal motion, localized asymmetric resistance, prolonged uneven-surface excitation, robustness-boundary analysis, and actuator-dynamics sensitivity. The results show that the proposed strategy improves directional stability under uneven-surface disturbances, limits the degradation of forward motion, and enlarges the admissible operating region compared with decoupled drive action. The study demonstrates that coordinated inter-wheel control provides a physically interpretable and computationally efficient solution for enhancing the stability of wheeled mobile robots operating on irregular terrain.