4,939 research outputs found
Current integration force and displacement self-sensing method for cantilevered piezoelectric actuators.
International audienceThis paper presents a new method of self-sensing both of the displacement and the external applied force at the tip of piezoelectric cantilevers. Integrated electric current across piezoelectric actuators is compensated against material nonlinearities creep, hysteresis to provide reliable information. We propose to compensate the hysteresis by using the PrandtlâIshlinskii static approach while an auto regressive and moving average exogenous ARMAX model is used to minimize the creep influence. The quasistatic estimation, electronic circuit, and aspects related to long-term charge preservations are described or referenced. As an experiment, we tested the actuator entering in contact with a fixed force sensor. An input signal of 20 V peak-to-peak 10% of maximum range led to force self-sensing errors inferior to 8%. A final discussion about method accuracy and its limitations is made. © 2009 American Institute of Physic
Continuous time controller based on SMC and disturbance observer for piezoelectric actuators
Abstract â In this work, analog application for the Sliding Mode Control (SMC) to piezoelectric actuators (PEA) is presented. DSP application of the algorithm suffers from ADC and DAC conversions and mainly faces limitations in sampling time interval. Moreover piezoelectric actuators are known to have very large bandwidth close to the DSP operation frequency. Therefore, with the direct analog application, improvement of the performance and high frequency operation are expected. Design of an appropriate SMC together with a disturbance observer is suggested to have continuous control output and related experimental results for position tracking are presented with comparison of DSP and analog control application
Strainrange partitioning behavior of an automotive turbine alloy
This report addresses Strainrange Partitioning, an advanced life prediction analysis procedure, as applied to CA-101 (cast IN 792 + Hf), an alloy proposed for turbine disks in automotive gas turbine engines. The methodology was successful in predicting specimen life under thermal-mechanical cycling, to within a factor of + or - 2
Interaction between current imbalance and magnetization in LHC cables
The quality of the magnetic field in superconducting accelerator magnets is associated with the properties of the superconducting cable. Current imbalances due to coupling currents ÂżI, as large as 100 A, are induced by spatial variations of the field sweep rate and contact resistances. During injection at a constant field all magnetic field components show a decay behavior. The decay is caused by a diffusion of coupling currents into the whole magnet. This results in a redistribution of the transport current among the strands and causes a demagnetization of the superconducting cable. As soon as the field is ramped up again after the end of injection, the magnetization rapidly recovers from the decay and follows the course of the original hysteresis curve. In order to clarify the interactions between the changes in current and magnetization during injection the authors performed a number of experiments. A magnetic field with a spatially periodic pattern was applied to a superconducting wire in order to simulate the coupling behavior in a magnet. This model system was placed into a stand for magnetization measurements and the influence of different powering conditions was analyze
Preliminary feasibility study of a speed estimator for piezoelectric actuators used in forging processes
In this paper the feasibility of a speed estimator for a piezoelectric actuator used in a forging process is studied. It is based on a simplified linear model and its robustness is tested using a more complex model that include the hysteresis effects. The preliminary results proves that the concept is feasible despite the non-linearities, provided that some parameters of the actuator are known
Parameters Identification for a Composite Piezoelectric Actuator Dynamics
This work presents an approach for identifying the model of a composite piezoelectric (PZT) bimorph actuator dynamics, with the objective of creating a robust model that can be used under various operating conditions. This actuator exhibits nonlinear behavior that can be described using backlash and hysteresis. A linear dynamic model with a damping matrix that incorporates the BoucâWen hysteresis model and the backlash operators is developed. This work proposes identifying the actuatorâs model parameters using the hybrid master-slave genetic algorithm neural network (HGANN). In this algorithm, the neural network exploits the ability of the genetic algorithm to search globally to optimize its structure, weights, biases and transfer functions to perform time series analysis efficiently. A total of nine datasets (cases) representing three different voltage amplitudes excited at three different frequencies are used to train and validate the model. Four cases are considered for training the NN architecture, connection weights, bias weights and learning rules. The remaining five cases are used to validate the model, which produced results that closely match the experimental ones. The analysis shows that damping parameters are inversely proportional to the excitation frequency. This indicates that the suggested hysteresis model is too general for the PZT model in this work. It also suggests that backlash appears only when dynamic forces become dominant
Electrodynamics of Superconductors Exposed to High Frequency Fields
The electric losses in a bulk or film superconductor exposed to a parallel
radio-frequency magnetic field may have three origins: In homogeneous
vortex-free superconductors losses proportional to the frequency squared
originate from the oscillating normal-conducting component of the charge
carriers which is always present at temperatures . With increasing field
amplitude the induced supercurrents approach the depairing current at which
superconductivity breaks down. And finally, if magnetic vortices can penetrate
the superconductor they typically cause large losses since they move driven by
the AC supercurrent.Comment: 12 pages, 18 figures, for conference proceeding
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