Over the past decade we have been able to vastly improve the control algorithms of our biped walking robot LOLA. Further enhancements, however, are limited by vibration problems caused by the dynamics of LOLA's mechanical structure. In this work, we present small examples how structural dynamics limit our control design for walking control as well as low level position control of the joints. We also provide a procedure to identify weaknesses in the structural design of our biped using Experimental Modal Analysis. Using this method, we could successfully identify the structural modes of the system. Furthermore, we were able to use a closed-loop identification method to show a connection between the control loop resonances and the structural resonances of our robot.

In order to fulfill conflicting requirements in the development of industrial robots, such as increased accuracy of a weightreduced manipulator with lower mechanical stiffness, the robot's dynamical behavior must be evaluated early in the development process. This leads to the need of accurate multibody models of the manipulator under development.This paper deals with multibody models that include flexible bodies, which are exported from the corresponding Finite Element model of the structural parts. It is shown that such a flexible link manipulator model, which is purely based on development and datasheet data, is suitable for an accurate description of an industrial robot's dynamic behavior. No stiffness parameters need to be identified by experimental methods, making this approach especially relevant during the development of new manipulators. This paper presents results of experiments in time and frequency domain for analyzing the modeling approach and for validating the model performance against real robot behavior.

Because of their large workspace, robot manipulators have the potential to be used for high precision non-contact manufacturing processes, such as laser cutting or welding, on large complex work pieces. However, most industrial manipulators are not able to provide the necessary accuracy requirements. Mainly because of their flexible structures, they are subject to point to point positioning errors and also vibration errors on a smaller scale. The vibration issues are especially hard to deal with. Many published solutions propose to modify the robot's own control system to deal with these problems. However, most modern control techniques require high fidelity models of the underlying system dynamics, which are quite difficult to obtain for robot manipulators. In this work, we propose an external stabilization unit with an additional set of actuators/sensors to stabilize the process tool, similar to Optical Image Stabilization systems. We show that, because of collocated control, a model of the robot's own dynamic behavior is not needed to achieve high tracking accuracy. We also provide testing results of a prototype stabilizing a dummy tool in two degrees of freedom on a UR10 robot, which reduced its tracking error by two orders of magnitude below 20 micrometers.