In autonomous system, it is important to establish a control scheme that works with stability even near singularity con£gurations. 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 con£gurations. The result shows a good performance near the singular con£gurations, as shown by simulation results. And, the proposed algorithm is also validated by experimental results.


In the repeating tasks or simple tasks, the desired task trajectory can be planned avoiding the singular points. And, it can be also overcome by mechanical design. In the manageable area, even though the manipulator are fallen into the singular points, the damage and emergency situation can be restored manually after stopping the task. However, in the uncontrollable area-space, underwater, and etc.–, we can not desire the manual labor and the tele-operation is also limited. So, the stability over singularity is the most important in those cases. Comparing with the manipulability of each 1-DOF task, it sets the task priorities.

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