The rotor test-rig PROTOR is used to investigate the behavior of rotors with active piezoelectric bearings. The focus of the investigations is on the use of different control approaches with different objectives, e.g. the elimination of bearing forces. The properties of the rotor are changed by a dynamic manipulation of the rotational axis of the rotor throughout the active bearings, which causes a reduction of vibrations.

The test-rig consists of a slim shaft, two active piezoelectric ball bearings and up to two discs. The disks and bearings can be moved freely on the shaft by using clamping sets. In this way, the behavior of various lightly damped elastic rotors can be reproduced and investigated. For example, a design can be chosen that resembles a Jeffcott-rotor or a jet engine with strong gyroscopic behavior. The shown set-up of the rotor has two resonances in the operating range. Furthermore, the test bench shows rotational damping due to the use of clamping sets. For investigation and control, the displacements of the two disks and the two bearing forces are measured in the 2D plane. The use of Simulink-Realtime XPC allows a simple and fast implementation of control approaches.

In the past, most common control approaches such as LQR/LQG, Integral Force Feedback, FxLMS, µ-Synthesis, and Gain-Scheduled H have been implemented. It was found that a combination of Integral Force Feedback and FxLMS yields the best results regarding vibration isolation, which is equal to the elimination of the bearing forces. It remains to be seen how the transient performance of the control, so for rotor run-ups and run-outs, can be improved. Another research topic is the investigation of the relevance and, if necessary, elimination of the so-called force-free resonances, which occur when the bearing forces are completely eliminated by the active control. The project AMOS aims at the consideration of the bending energy to eliminate these force-free resonances.

Using the bending energy as a controlled variable. Project: AMOS: Analytical Methods for Optimal Vibration Reduction on General Rotors

Motor EC45 BL D 250W KL 2WE A from Maxon Motor
Speed: 0-10.000 rpm
Actuators PSt 1000/10/60 VS18 from Piezosystem Jena
Capacity: 177 nF
Free displacement: 60µm
Blocking force: 4kN
Power amplifier TREK PZD700-MS-H-CE from Trek Inc.
Voltage: 0-1400V
Current: 100mA
Realtime software Simulink Realtime XPC from Matlab
Measuring card NI PCI-6259 M Series DAQ von National Instruments
NI PCI-6251 M Series DAQ von National Instruments
16 Bit, 48 A/D, 4 D/A, 72 DIO
Displacement sensors WSD S4/10 from Unidor TR systems Gmbh
Range: 0-4 mm
Resolution: <0,005 mm
Repeat accuracy: <0.01 mm
Linearity error: ±4%
Force sensors 9001A + 5073A411 from Kistler
Range: 0-7,5 kN
Linearity error: ±1%
Incremental encoder ENC HEDL 9140 500IMP 3K from Maxon Motor
2000 points
Evaluation units on actuators Strain gouges