Reliability evaluation of manipulators by means of probability of task achievement

This paper represents a new method for evaluating reliability of manipulators by means of probability of task achievement. Since, articulated manipulators have functional redundancies depending on assigned tasks, they may be able to achieve the task even with faulty joints. In the proposed method, reliability is evaluated taking this feature into account. First, the assigned task is resolved into task steps. Success conditions for achieving each step are obtained based on a manipulator model, which is represented in terms of DH parameters. Next, a success condition of whole task is computed from those of task steps. Finally, the probability of task achievement is evaluated by specifying failure rates of joints in the success condition of whole task. An illustrative example shows the evaluation of a seven DOF manipulator applied to an inspection task.