Error identification and compensation in large manipulators with application in cancer proton therapy

Abstract

Important robotic tasks could be effectively performed by powerful and accurate manipulators. However, high accuracy is generally difficult to obtain in large manipulators capable of producing high forces due to system elastic and geometric distortions. A method is presented to identify the sources of end-effector positioning errors in large manipulators using experimentally measured data. The method does not require explicit structural modeling of the system. Both geometric and elastic deformation positioning errors are identified. These error sources are used to predict, and compensate for, end-point errors as a function of configuration and measured forces, improving the system absolute accuracy. The method is applied to a large high-accuracy medical robot. Experimental results show that the method is able to effectively correct for the system errors.<br>Importantes tarefas robóticas poderiam ser eficientemente executadas por manipuladores potentes e precisos. No entanto, alta precisão absoluta é geralmente difícil de ser obtida em grandes manipuladores capazes de produzir forças de alta intensidade, devido às distorções elásticas e geométricas do sistema. Um método é apresentado para identificar, através de medições indiretas, as fontes de erro de posicionamento da extremidade de grandes manipuladores. O método não requer uma modelagem estrutural explícita do sistema. Ambos os erros geométricos e elásticos de posicionamento são identificados. Esses valores são usados para predizer e compensar os erros da extremidade do robô em função da configuração e de forças medidas, melhorando a precisão absoluta do sistema. O método é aplicado a um grande robô médico de alta precisão. Resultados experimentais demonstram que o método é capaz de corrigir eficientemente os erros de posicionamento do sistema

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A low-cost approach for self-calibration of climbing robots

“…r General error sources of industrial robotic arms (type A errors) High accuracy is generally difficult to obtain in large manipulators capable of producing high forces due to system elastic and geometric distortions 14 . Due to some sources of errors, namely tolerance on gears, coupling errors, deflection of the links, etc., the manipulator has positioning errors.…”

Fuzzy logic control of single-link flexible joint manipulator

“…Control engineers have been working on the development of a mathematical model and the control of flexible structures. Flexible mechanisms and flexible-joint manipulators were applied for reducing the vibration in the remote manipulator system in a space station-assembly shuttle flight [1], performing decontamination tasks in nuclear maintenance and positioning the nozzle dam in the maintenance of a nuclear power plant's steam generator [2], remediating a waste storage tank [3], cleaning a waste tank [4], operating in microsurgical applications [5], positioning a patient system for cancer patient treatment [6], deburring [7], surface polishing [8], and grinding, painting, and drawing applications and biped-walking and walking machines [9]. They are mostly used in the service, space, medical, and defense industries.…”