Kinematic singularity avoidance for autonomous manipulation in underwater

In autonomous system, it is important to establish a control scheme that works with stability even near singularity configurations. In this report, an on-line trajectory control scheme that uses the manipulability measure as a distance criteria to avoid manipulator singularities is described for robotic manipulators with dynamic change of the task priority. First, given tasks are reconstructed using a geometric projection on the given index function. Then, the reconstructed tasks are analyzed in the framework of task priority based method. From this analysis, the proposed algorithm is shown to have the property that the task priority is assigned dynamically. Using this algorithm, we easily set the criteria of changing task priority and estimate the performance of the given index function. Considering the measure of manipulability as a index function, the approach is suitable for avoiding kinematic singularities for autonomous operation of, for example, underwater robot. Based on a real-time evaluation of the measure of manipulability, this method does not require a preliminary knowledge of the singular configurations. The result shows a good performance near the singular configurations, as shown by simulation results. And, the proposed algorithm is also validated by experimental results.