Denkena, B., Fuchs, J.:
|Titel:||Magnetically guided multi-coordinate positioning system|
|Stichworte:||Direct drive, multi-coordinate drive, magnetic bearing, magnetic guide, SPMPM, Planar Motor, friction free, fine positioning|
Conventionally, single degree of freedom feed axes are used in machine tools. A serial coupling enables movements in several degrees of freedom. Due to this coupling, the underlying axis carries the axes arranged on it. The supporting axis also accelerates the overlying axes. Consequently, both the acceleration capacity and the dynamic behavior of the coupled axes differ. Compared to these serial kinematic chains, positioning systems with more than one degree of freedom offer numerous advantages. These are mainly the consequence of the lower masses to be moved. This results in higher acceleration and an increase in overall rigidity. In addition, the summation of positioning errors in the serial arrangement of feed axes can be avoided. In the first project phase of the basic project "Principles of a multi-coordinate positioning system for metal cutting machine tools" (DE447/126-1), therefore, IFW researched a method for the design and operation of a magnetically guided and directly driven planar positioning system. In the second project phase, which has now been applied for, the limits and benefits of the multi-coordinate positioning system will be researched. First, the control of the planar motor will be extended by compensation algorithms to reduce the parasitic detent forces and their effect will be validated. Furthermore, the potentials of model-based controllers for magnetic planar guidance are analyzed. The maximum dynamic stiffness that can be achieved by applying these various controllers will be focused. In the first project phase, it was shown that the position-dependent attraction forces of the planar motors negatively influence the guidance. Therefore, in this project phase, a method for compensating these disturbing forces is developed. The tilting moments generated by the translational acceleration are also taken into account. Based on the comparison of the dynamic properties of the multi-coordinate positioning system with those of other machine tools, the benefit of the multi-coordinate positioning system for cutting applications is evaluated. The control of the planar motors is then extended by the sixth degree of freedom. This means that the previously required mechanical torsion lock can be dispensed, so that a multi-coordinate positioning system, actively guided in all six degrees of freedom, is implemented.