On Task Space Sliding Mode Tracking Control of Robot Manipulators Actuated by Brushless DC Motors with Experimental Validation ^*

The main objective of this study is to devise a control structure for robot manipulators actuated by brushless direct current (BLDC) motors while accounting for uncertainties in kinematic, dynamic, and electrical models. Robustness properties of sliding mode control techniques are employed to address uncertainties associated with dynamic and electrical models, whereas a gradient-based adaptive approach is utilized for handling kinematic model uncertainties. To keep the control efforts at reasonable limits, the known nominal values of the dynamical and electrical model parameters are also employed in the controller design. As part of the backstepping based methodology, a novel continuous virtual controller design strategy is tailored as well. The stability of the closed-loop system is analyzed rigorously utilizing Lyapunov-type arguments and global asymptotic stability is ensured. Experimental results obtained from a custom-built two degree-of-freedom planar robot manipulator actuated by BLDC motors demonstrated the efficacy of the proposed control framework where the task space tracking errors remained below 0.8 millimeters.