Diagonally-Decoupled Direct Visual Servoing

This paper addresses the problem of vision-based robot control where a reference image defines the equilibrium. Specifically, we consider the class of intensity-based nonmetric solutions, which provide for high accuracy, versatility, and robustness. Existing techniques within that class present either a fully coupled control error dynamics or at best only achieve decoupling of the translational part, i.e., they can only obtain a lower triangular system. These couplings in the system dynamics increase analysis complexity and may degrade system performance. This work proposes a new nonlinear observer for also decoupling the rotational part, i.e., for diagonally decoupling the entire control error dynamics. Theoretical proofs of stability and of those decoupling properties are provided. Improved performances are also experimentally confirmed using synthetic and real data, planar and nonplanar objects, simulating and applying a camera-mounted 6-DoF robotic arm.