Papers by Author: Hubert Gattringer

Abstract: This paper deals with passivity based control of a cart , which can moves on a skew plain. On the cart a non actuated pendulum is assembled. Therefore, the mechanical system is non-linear, one degree under actuated and instable. The equation of motion is derived by the method of Lagrange. The goal of the control strategy is to stabilize the cart and the upper position of the pendulum. The applied control strategy is called Interconnection Damping Assignment Passivity Based Control (IDA-PBC). This method allows a physical approach with a simple proof of stability having appropriate Lyapunov function on hand. The simple proof of stability is an advantage of this theory. However, the proof of stability is fulfilled, challenging partial differential equation have to be solved to get the control law. Measurements results are presented.

Abstract: In this paper the effects of rotordynamics under the aspect of the choice of shape functions are discussed. For this purpose a rotor system which consists of a slim shaft and two rigid disks is modeled using the Projection Equation. The shaft is assumed as an elastic Euler-Bernoulli beam, supported by two bearings modeled as radial spring systems. The rotor is driven by a permanent-magnet synchronous motor whose torque is transmitted with a spur gear pair next to one of the bearings. A Ritz approach is used to separate the elastic displacements in position and time, thereby different shape functions are evaluated. Approximated eigenfunctions are computed and used as shape functions as well. For validation, the eigenfrequencies are compared with semi-analytical ones, calculated with the Transfer-Matrix-Method and experimental results. The insights obtained from this work should make it easier to choose the appropriate shape functions for such problems.

Abstract: This paper investigates the sensorless detection and evaluation of inner oscillations of unknown test objects mounted on a compliant test bench. The principle of the sensorless analysis is that test objects are not totally rigid in reality. This means one or more parts of the test objects are oscillating with different eigenfrequencies compared to their rigid equivalent. By comparing eigenfrequencies of both (rigid and fault test object) oscillating parts are detectable. The aim of this experiment is to demonstrate the use of a 6 DOF compliant Stewart platform (alternatively used in a simulation environment) to generate frequency sweeps in all degrees of freedom, to get a sensorless detection of vibrations in unknown objects. For this purpose only the preexisting sensors applied for the control of the hexapod should be used. The detection of loose parts by shaking objects can be done by a complex robotic manipulation task. Being designed for flexible use by small and medium-sized enterprises, the robotic Stewart platform (hexapod) will adapt autonomously to different test objects leading to a highly flexible robot.