Optimal networked control of a 2 degree-of-freedom direct drive robot manipulator

This paper proposes a suboptimal control solution for the L₂-gain disturbance rejection problem for networked control systems. The problem, usually referred as mixed H₂/H_∞, aims at designing a linear state feedback stabilizing controller minimizing a quadratic cost functional subject to a L₂-gain disturbance rejection constraint. The formulation deals with time-varying delays and dropouts in both, sensor-to-controller and controller-to-actuator paths, with the only assumption of known minimum and maximum bounds of the round trip delay, and the maximum number of consecutive dropouts. The solution is based on a Lyapunov-Krasovskii approach and is formulated as a Nonlinear Matrix Inequality (NLMI) problem. This problem is cast into more a treatable LMI-based minimization problem, for which a well-known optimization algorithm is provided. Experimental results on a networked controlled direct-drive 2 degree-of-freedom (dof) robot manipulator are provided to verify the performance of the methodology.