Methodology for Identifying Radiation Effects in Robotic Systems With Mechanical and Control Performance Variations

The complications of identifying radiation effects in electromechanical sensors in the presence of mechanical variation are discussed. A corresponding analysis method is developed to separate radiation degradation effects from expected sensing variation due to mechanical tolerances of test fixtures. This is achieved by statistically characterizing the fixture variation for each sensor before irradiation, and evaluating the statistical significance of any sensitivity changes after irradiation. The method is demonstrated using a contactless Hall-effect rotary encoder IC commonly used in robotic systems. Sensitivity changes in measurements relevant to robotic controller design are isolated and quantified as a maximum positioning error of 0.5° and an angular velocity error of 1.5%. These measurements can be used to improve a commercial off-the-shelf robotic system's tolerance to radiation by designing motion controllers robust to sensitivity changes prior to total device failure.