Multiobjective multidisciplinary optimization supports the development of mechatronic systems. A suitable approach is required for a short calculation time and sufficient results. All aspects of the system model (mechatronic system, cost model and time optimal control problem) are incorporated into one nonlinear optimization model, following the all-at-once approach. The dynamic simulation is discretized in time and optimization variables are introduced for the state at each time step. Formulating the problem in an algebraic modeling language and solving it by the interior point method allows very fast solution times. This enables a fast turnaround time during the preliminary design phase in the product development. Sensitivities of the objective with respect to model parameters and design constraints are generated by the solver and used to guide the modeling and development process. Using these sensitivities, the model can be improved where necessary while keeping the model complexity low by simplifying less important parts. As example an electromechanical actuating system is considered, in which the rotary motion of a motor is converted to a translational movement with a gate-tape gear.

Piezoelectric actuators provide an active solution for vibration control in aircraft engines compared to the state-of-the-art squeeze film dampers. The property of piezoelectric materials enable them to be used as sensors and actuators simultaneously. This self-sensing property of the actuator is analyzed in this paper for its ability to detect unbalance faults, which are common in rotor systems. In this paper two different actuator configurations are studied for its ability to diagnose unbalance faults in an aircraft engine. Three parameters of unbalances such as its magnitude, its position in the circumferential and axial direction in a rotor are estimated through simulations. Finally a suitable position to achieve a better fault diagnosis is identified.

This paper deals with active vibration isolation of unbalance-induced oscillations in rotors using gain-scheduled H ∞ -controller via active bearings. Rotating machines are often exposed to gyroscopic effects, which occur due to bending deformations of rotors and the consequent tilting of rotor disks. The underlying gyroscopic moments are proportional to the rotational speed and couple the rotor’s radial degrees of freedom. Accordingly, linear time-varying models are well suited to describe the system dynamics in dependence on changing rotational speeds. In this paper, we design gain-scheduled H ∞ -controllers guaranteeing both robust stability and performance within a predefined range of operating speeds. The paper is based on a rotor test rig with two unbalance-induced resonances in its operating range. The rotor has two discs and is supported by one active and one passive bearing. The active support consists of two piezoelectric stack actuators and two collocated piezoelectric load washers. In addition, the rig is equipped with four inductive displacement sensors located at the discs. Closed-loop performance is assessed via isolation of unbalance-induced vibrations using both simulation and experimental data. This contribution is the next step on our path to achieving the long-term objective of combined vibration attenuation and isolation.

H ∞ -optimal controllers are designed for a rotor being subject to unbalance excitation and gyroscopic effect. The system possesses two unbalance-induced resonances within its operating range. The presence of gyroscopic effect is challenging for linear time invariant controller design because of the associated dependence of the system dynamics on the rotational frequency of the rotor. Controllers thus have to be robust against deviation of the actual system behavior from the controller design point model. For vibration control purposes, there are two piezoelectric actuators installed in one of the two supports of the rotor. The signals of four inductive sensors measuring the displacements of the two discs of the rotor are used for controller design. In this article, H ∞ -optimal controllers are designed on the basis of input and output weighting as well as weighting of modal degrees of freedom and modal excitations. It is shown that superior control performance is achieved using modal weighting since a more accurate problem description of rotors excited by unbalance is incorporated in controller design. Results in this article show furthermore that it is possible to design well performing H ∞ -optimal controllers for a gyroscopic rotor by means of iterative controller design without taking model uncertainty directly into account via weighting of certain FRFs of the system to be controlled.

Locations of sensors and actuators have major impact on the characteristics of control systems. In this paper a procedure for sensor and actuator placement for vibration control systems is presented. Two different performance criteria are used in order to find optimal positions for the system under consideration. One is considering observability and controllability only, the other one includes knowledge about a disturbance and the control objective. Both criteria are applied to a clamped plate resulting in different optimal sensor and actuator positions. The resulting configurations are investigated by comparison of optimal feed forward and H ∞ feedback control of the system with identical disturbances and control objectives but different sensor and actuator positions. The required control effort and achieved amplitude reduction are employed to rate the different performance criteria that were used to determine the sensor and actuator positions. It is shown that, by placing sensors and actuators on the basis of an adequate performance criterion, increased control performance in terms of amplitude reduction per control effort is achieved.

This paper discusses the suitability of a special discrete filter, called balancing filter, to improve the performance of model-based fault detection and fault diagnosis on a centrifugal pump in active magnetic bearings. The focus in this subject lies on the extraction of better symptoms for the fault diagnosis. The application of the balancing filter sets up on a multi-model approach which uses a model of the system for the reference state and every fault that is to be detected. These models are stimulated with the same test signals as the ones applied to the process while it is running. To compare the simulation results of the models with the process response the output error is calculated. After this the remaining residuals are used as symptoms for the fault detection. The balancing filter is used to remove the large differences within the amplitude responses of the models caused by the lowpass characteristics of the mechanical part of the system. Hence the influence of the smaller differences caused by the examined faults is weighted equally at all interesting frequencies. This leads to new residuals which are separated more clearly. This approach is used to detect common faults appearing on centrifugal pumps as dry run, incorrect installation and worn out balance pistons. The test rig used to examine the suitability of the proposed filter is a one-level centrifugal pump in magnetic bearings. The rotor of the pump is driven by an asynchronous motor at rotation speeds up to 3000 rpm . The first flexible mode of the rotor is located at 280 Hz . In the seal gap fluid-structure-interaction is appearing. The forces on the rotor are calculated based on the current applied to the bearings, while its displacement is measured by eddy current sensors integrated into the bearings. The first two natural frequencies of the system are located at about 200Hz and 500 Hz . These frequencies are shifted when a fault is occuring. In the models for the fault states this behaviour is represented. Hence the model matching the current state of the pump leads to the lowest residual. The advantage of the balancing filter is that the detection of faults becomes more reliable. Below the examined faults, the model-based concept and the design of the balancing filter are described in detail. Results from experiments on the test rig are given to show the advantages of the balancing filter.