Feedback-linearization and fuzzy controllers for trajectory tracking of wheeled mobile robots

Purpose - The purpose of this paper is to focus on perfect trajectory tracking control of 2 DOF non-holonomic mobile robots in which the guidance and control commands are imposed through independent driver wheels. Model-based nonlinear controllers for these robots with unknown parameters require estimation of a specified set of the robot parameters. The effects of the proposed model dynamics in both local and global coordinate systems are fully examined on the parameter estimation and tracking performance. Design/methodology/approach - Design of suitable feedback linearization (FL) controllers for trajectory tracking control of wheeled mobile robots (WMRs) is first reviewed. A FL controller whose parameters are tuned using fuzzy computations (fuzzy if-then rules) is then developed. In the line of the other contributions of the paper, a pure fuzzy controller that is merely based on fuzzy if-then rules is proposed to trajectory tracking control of the mobile robots. Findings - Use of global dynamics for designing a suitable FL control system leads to a perfect compensation fa: initial off-tracks. Furthermore, the estimated parameters are unbiased because the corresponding regressor/signal matrix indicates a high rank of persistent excitation. Fuzzy tuning of the controller instead of keeping the gains fixed makes the overall system more robust against measurement noises while upper bounds and fluctuations of the input torques are both remarkably reduced. The pure fuzzy controller is naturally independent of the robot dynamics and therefore, the necessity of parameter estimation algorithm is removed. Originality/value - The paper provides some new nonlinear controllers for WMRs, in order to make perfect trajectory tracking, and initial off-tracks compensation.