Uncalibrated visual servoing for full motion dextrous robot systems with tracking cameras

Visual servoing methods are reviewed along with their limitations in low-cost uncalibrated situations. A description of the camera model is then given including an overview of visual Jacobian calculations. The problem of selecting suitable gains for implementation in real-time is developed. The model system used is of the anthropomorphic service robot HERMES. It is highly nonlinear and redundant with 6-DOF in the camera system and 6-DOF in each of its two arms. The selection of gains is difficult due to the nonlinearity of the Jacobian over the complete robot. A conservative controller for the camera is developed and a single measure for gripper orientation is outlined along with its limitations. Two solutions to the problems of alignment in visual servoing over a large workspace are given. The first approach weights the alignment heavily during the initial stages, and the second one uses a starting point grid derived by "visually voxellating" the workspace. Results of exhaustive and local motion tests are then given. The proposed alignment method improved the visual servoing alignment performance.