|Tipo di tesi||Tesi di laurea magistrale|
|Titolo||CONTROLLO ATTIVO DI VIBRAZIONI DI UNA PIASTRA SANDWICH COMPOSITA CON UN MICROCONTROLLORE|
|Titolo in inglese||ACTIVE VIBRATION CONTROL OF A COMPOSITE SANDWICH PLATE USING A MICRO-CONTROLLER|
|Struttura||Dipartimento di Ingegneria "Enzo Ferrari"|
|Corso di studi||Advanced Automotive Engineering (D.M.270/04)|
|Data inizio appello||2021-10-21|
|Disponibilità||Embargo di 12 mesi|
|Data di rilascio||2022-10-21|
In questa tesi, il problema del controllo attivo delle vibrazioni (AVC) è stato efficaciemente affrontato come un problema di controllo, con l'impianto del sistema che è un pannello a nido d'ape con una pelle esterna in polimero rinforzato con fibra di carbonio (CFRP) e un nucleo di carta polimerica. È stata proposta, sviluppata e testata una soluzione economica e pratica ai problemi AVC. La piastra sandwich è stata testata sperimentalmente attraverso un'analisi modale utilizzando test di impatto per identificare le frequenze naturali e le forme modali della piastra CFRP. Il risultato dell'analisi modale è stato analizzato per identificare e selezionare le forme modali da controllare e per trovare la posizione dell'attuatore e del sensore da posizionare sulla piastra, per un controllo efficace.
In this thesis, Active Vibration Control (AVC) problem is effectively treated as a control problem, with the plant of the system being a honeycomb panel having a Carbon-Fiber Reinforced Polymer (CFRP) outer skins and a polymer-paper core. A cost effective and practical solution to AVC problems has been proposed, developed and tested. The sandwich plate has been experimentally tested through a modal analysis using impact testing to identify the natural frequencies and mode shapes of the CFRP plate. The result of the modal analysis was analysed to identify and select the mode shapes to be controlled and to find the position of the actuator and sensor to be placed on the plate, for effective control. The control problem is studied by subjecting the plate to out of plane disturbance using an electrodynamic shaker, exciting the identified modes. The sensor for the control problem is a laser vibrometer, measuring the velocity of the plate vibrations based on the Doppler effect. The core of the control is the microcontroller unit from TI which is the TI Delfino F28379D. Selection of MCU is crucial to this particular application since the effectiveness and speed of the control heavily depends on the processing speed of the CPU and sampling rate of the Analog to Digital Converter (ADC) used in the MCU. Multiple analog signal processing circuits were developed to adapt the output of the sensor to the input of MCU and also to amplify and shift the output of MCU to be compatible with the actuator input. The control algorithm proposed in this thesis is based on Positive Position Feedback (PPF) technique. The PPF controller is effectively modelled as a second-order filter, which is then studied for stability and spillover. The embedded coder support package was used to interface the MCU with MATLAB/Simulink environment. This interface provided real-time tuning of controller gain, which is tuned to place the controller in stable region. The actuator chosen for the stated AVC problem are the Macro Fiber Composites (MFC) patches. The patches consist of rectangular piezo ceramic rods, sandwiched between layers of adhesive, electrodes and polyamide film. The patch expands in length when voltage is applied across its terminals, making it a suitable actuator for the control problem. Owing to the size and mass properties of the MFC patches, the control system is very much suitable for automobile and aerospace applications. A series of tests were performed using pure sine excitations at frequencies of interest. The test data is post processed partly in LMS Testlab and in MATLAB. The result of the experiments revealed a velocity attenuation of 50% to 77% and Power Spectral Density (PSD) attenuation of 5.8 to 12.8 dB, depending on the mode under study. Hence a cost-effective control system for the AVC problem is developed to attenuate pure tone excitations up to 77% in time domain.