To improve the model quality and thus also the control, detailed modeling, in particular of hysteresis phenomena, is required in comparison with measured data. Operator-based or differential (also fractional) approaches must be compared with respect to their structure, complexity and real-time capability. Furthermore, sensor quantizations, which have so far been simplistically regarded as disturbances, have to be included, since they become relevant for the targeted accuracies. So far, standard controllers can only bring the system dynamics to a stable limit cycle. Adapted designs  are able to reduce the extent of this limit set so that the accuracy is increased. For state estimation, quantization with hybrid observers or oversampling can be considered. For this purpose, the sampling time must be chosen as small as possible, which requires a near-hardware implementation. For a highly dynamic control of tip- and laser-based machining processes, not only the distance but also the current between cantilever and substrate (A1, A2) or the laser power has to be actively controlled in case of unknown surface properties. For this purpose, observer approaches from past measurement points must be used to make predictions about the (future) geometry still to be processed. If the unknown geometry is modeled as a perturbation, fractional approaches can help here to extend the possible perturbation class. Multidimensional approaches are required to account for directionality. Subsequently, the control of the cantilever current or the laser power should be operated coupled with the subordinate position control.
Project leader: Prof. Reger, Dr. Schäffel
For both tactile measurements, but especially for machining, force-guided control [TF9] and metrological traceability of the force vector measurement are crucial because knowledge of the infeed force and the position-dependent mechanical interaction between specimen and tool is important for precise machining. Therefore, the research task is to investigate the traceable calibration of suitable single- and multi-component force sensors. For this purpose, multicomponent force-torque sensors with a high measurement dynamic range, fast transmission properties and purely electrical in-situ calibration are to be investigated. Conceptual and substantive cooperation is planned in particular with the PhD fields A1, KR1, KR3 and TM1.
Project leader: Prof. Fröhlich, Prof. Reger
The goal of KR3 is the ever better understanding and implementation of highly dynamic nanopositioning systems in NPMM machines. The vertical actuator systems developed in the first generation must be intensively characterized in a test rig to be designed. This includes the design of a controller for the overactuated system as well as the implementation of a variable operating mode with respect to the required precision, dynamics and thermal boundary conditions. One focus of the investigation is the influence of the pneumatic valve with integral controller with regard to the effects on the achievable precision and dynamics. After subsequent integration of three vertical actuator systems into the planar drive system, new 6DoF control concepts have to be designed and evaluated, since the slider can now be moved in all degrees of freedom. This includes algorithms for safe start-up and shut-down as well as for collision avoidance.
Project leader: Dr. Schäffel, Prof. Reger, Prof. Hausotte