Abstract
Observer-corrector feedback is a control strategy which reduces destabilizing effects of unmodeled higher-order dynamics (e.g., structural resonances of a robotic manipulator) found in many systems subject to control. The fundamental idea is to synthesize a substitute feedback signal in order to extract dominant dynamic components (e.g., rigid body motion of a robotic manipulator) from the output of the controlled system. A band-limited state observer complemented by a low-pass filter corrector are employed for this purpose. The synthetic signal is used as a controller input, effectively eliminating destabilizing effects of unmodeled dynamics of the controlled system. In the presented work, the observer-corrector feedback mechanism is implemented for motion control of a three-axis direct-drive robotic manipulator for automated pick-place operations in semiconductor manufacturing applications. A detailed technical description of the robotic manipulator is provided, a control system with the observer-corrector arrangement is designed, and selected results of laboratory tests are presented. The tests demonstrate that the observer-corrector feedback mechanism leads to improved control performance, increased stability margin, and added robustness against variations in system parameters in comparison to usual control methods.
