Position regulation of flexible-joint robots with input/output constant delays

In this paper, the problem of set-point control for flexible-joint robotic manipulators with input/output time delays is investigated. By utilizing scattering transformation with an input-output passive controller, it is demonstrated that the flexible-joint robotic control system can be stabilized when there are time delays in the communication channels. Although stabilization is achieved, the flexible-joint robot cannot be regulated to the desired configuration when utilizing the scattering variables. Hence, a new control framework without scattering transformation is subsequently studied in this paper to guarantee both stability and position regulation provided that the control gain is appropriately selected based on a bound on the time delays. The proposed control algorithms are validated via numerical examples on a two-link flexible-joint robotic manipulator.