SCUOLA DI INGEGNERIA
Dipartimento di Ingegneria dell’Energia, dei Sistemi,
del Territorio e delle Costruzioni
Corso di Laurea Magistrale in Ingegneria Elettrica
Power Consumption Analysis of an
Electromechanical Inertial Mass Actuator
Using a Custom Designed Measurement Board
Supervisors
Student
Prof. Paolo Bolognesi – University of Pisa
Francesco Romani
Ing. Giovanni Lapiccirella – Fraunhofer LBF
Ing. Christopher Ranisch – Fraunhofer LBF
ABSTRACT
This thesis is focused on the characterization of an electromechanical inertial mass actuator, which is a single-phase device used in active vibration control (AVC) systems: in order to compensate an unwanted vibrational signals, AVC systems employ the inertial actuator for providing an oscillating force of the same magnitude but opposite to the disturbance.
In the first part of the thesis, the electromechanical inertial mass actuator is introduced and analytical and numerical simulation models are derived, illustrating also a procedure that can be used to characterize the actuator.
In the second part of the thesis, the fundamentals of the analysis of power consumption are recalled mainly referring to periodic steady-state conditions, i.e. in the framework of frequency analysis. Algorithms for calculating active, reactive and apparent power components by directly processing the current and voltage waveforms are then presented.
The third part of the thesis presents the design and realisation of a compact electronic board devoted to the acquisition of voltage and current supplied to the actuator: such board is expected to carry out proper conditioning of the signals to permit an accurate measurement aimed to a complete analysis of the power consumption. The requirements for the measurement board are introduced and the design of the
measurement board is then carried out in two stages: (i) theoretical considerations and (ii) numerical (Simulink) analysis. In the first stage, the equations describing the measurement system are presented and the values of the design parameters are then adjusted in order to obtain the desired behaviour. In the second stage, the individual components of the board are modelled and their design parameters are also adjusted to match the desired behaviour. The design process of a prototype board is then described and the results of the tests carried out on a first breadboard prototype are presented and compared to the simulation results. Finally, the design of a refined Printed Circuit Board (PCB) version of the circuit is presented, illustrating the adjustments introduced to improve the layout.
The fourth part of the thesis presents the experimental activities carried out to characterize the inertial mass actuator and to analyse its power consumption under two different operating conditions. First, the actuator is connected to a structure that is rigid enough to prevent any displacement while subjected to the force provided by the actuator (infinite mechanical impedance). Then, the actuator is connected to a single degree of freedom system with adjustable resonance frequency (finite mechanical impedance). The results for the infinite impedance configuration show a capacitive behaviour around the mechanical resonance frequency of the actuator. This corresponds to a negative reactive power which means that the reactive power flows from the actuator to the power supplier: such behaviour is attributed to the spring elements in the device. At the resonance frequency, the larger displacement makes the actuator work as a reactive power generator. For the finite impedance configuration, the same capacitive behaviour appears around both of the mechanical resonance frequencies of the overall structure, which is composed of the two actuators connected together.
In conclusion, the target of this thesis, consisting in carrying out a complete analysis of the electric power drawn by an inertial mass electromechanical actuator, has been achieved by means of theoretical and numerical models and by experimental testing using a custom designed electronic board. Further developments could include developing more accurate analytical and simulation models and designing a more flexible signal conditioning board by permitting some gain adjustment.
