Model-based feedforward control in industrial robotics

Abstract

Simple linear joint controllers are still used in typical industrial robotic systems. The use of these controllers leads to non-negligible dynamic path deviations for applications that require high path accuracy. These deviations result from the strong influence of non-linearities, such as multi-body dynamics and gear friction. Sophisticated nonlinear control algorithms, known from the literature, are still not used because they usually require an expensive change of the control architecture. Therefore, different compensation methods are compared in this paper which reduce the path deviations by correction of the desired trajectory'. This means that no torque interface is required, only an interface for path corrections is necessary. Such an interface normnally exists so that the methods can simply be implemented within standard industrial controls. Using the industrial robot Siemens manutec-r15 the methods are experimentally compared with respect to their efficiency and practical applicability. Starting from this, one method is chosen for application to the state-of-the-art industrial robot KUKA KR15. The algorithm is based on a complete nonlinear dynamic model of the robot. It is integrated into the standard control KRC1. The experimental results prove the efficiency and the industrial applicability of the method.