{'fraction_non_alphanumeric': 0.015018773466833541, 'fraction_numerical': 0.0, 'mean_word_length': 5.833333333333333, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
IMPROVING THE POSITIONING ACCURACY OF POWERFUL MANIPULATORS WITH APPLICATION IN NUCLEAR MAINTENANCE

Powerful robotic manipulators are needed in nuclear maintenance, field, undersea and medical applications to perform high accuracy tasks requiring the manipulation of heavy payloads. The nozzle dam positioning task for maintenance of a nuclear power plant steam generator is an example of a task that requires a strong manipulator with very fine absolute positioning accuracy. Absolute accuracy, rather than simple repeatability, is required for autonomous operation or for teleoperation with advanced virtual aides, such as virtual viewing. However, high accuracy is generally unattainable in manipulators capable of producing high task forces due to such factors as high joint, actuator, and transmission friction and link geometric distortions. A method called Base Sensor Control (BSC) has been developed to compensate for nonlinear joint characteristics, such as high joint friction, to improve system repeatability. A method to identify and compensate for system geometric distortion positioning errors in large manipulators has also been proposed to improve absolute accuracy in systems with good repeatability. This technique is called Geometric and Elastic Error Compensation (GEC). Here, it is shown experimentally that the two techniques can be effectively combined to enable strong manipulators to achieve high absolute positioning accuracy while performing tasks requiring high forces. These developed control techniques are being implemented at the Korean and French power companies.