Fabio Cavalli

Dynamic Behavior of Torsional Eddy-Current Dampers: Sensitivity of the Design Parameters

Eddy-current devices are promising for the passive and semi-active control of vibrations. From the electromechanical point of view, their behavior is characterized by the torque-to-speed curve and the mechanical impedance. In this paper, we report an investigation of the electromechanical behavior of eddy-current dampers/couplers consisting of permanent magnets and a massive conductor. Our goal was to determine the influence of the main design parameters on the torque-to-speed characteristic and on the mechanical impedance. To this end, we studied the dependence of the electrical pole and static damping coefficient on the design parameters under a given current density distribution within the conductor. This approach is equivalent to the procedure used to characterize the inductance and the torque constant of a standard electrical machine and it allows us to show that the electrical pole is determined by the inductive and resistive nature of the conductive part. Even if the conductor is realized by a solid conductor, the approach allows us to determine its equivalent resistance and inductance as a function of the design parameters, such as the number of pole pairs and the thicknesses of the permanent magnets and the conductor. We validated the analytical expressions of the equivalent lumped parameters, of the electrical pole, and of the static damping coefficient by finite-element analysis. This analysis provides the guidelines to identify the project parameters that can be varied to optimize the performances of the device as a coupler, damper, or brake.

ELECTROMAGNETIC SHOCK ABSORBERS FOR AUTOMOTIVE SUSPENSIONS: ELECTROMECHANICAL DESIGN

This article illustrates the modeling and design of electromechanical shock absorbers for automotive applications. Relative to the commonly used hydraulic shock absorbers, electromechanical ones are based on the use of linear or rotative electric motors. If electric motor is of the DC-brushless type, the shock absorber can be devised by shunting its electric terminals with a resistive load. The damping force can be modified by acting on the added resistance. An integrated design procedure of the electrical and mechanical parameters is presented in the article. The dynamic performance that can be obtained by a vehicle with electromechanical dampers is verified on a quarter car model.© 2006 ASME

Design Procedure for Hysteresis Couplers

The present paper is devoted to the description of a procedure for the design of rotational hysteresis couplers for customer applications. The analysis has been oriented towards configurations characterized by high reliability and adaptability to the operating conditions. The tradeoff analysis leads to a claw pole configuration powered by an electromagnet in tandem with a permanent magnet to allow the regulation of the coupling torque and to assure a minimal amount of torque transmission when the power supply of the coupler fails. Moreover, the claw pole configuration seems to be the most promising for the automotive field due to its mechanical simplicity and magnetic efficiency. Unfortunately, the complexity of the magnetic circuit demands a three-dimensional numerical analysis that in the present paper is solved by the finite integrate technique. A design procedure based on this numerical analysis and on the hysteresis characteristics of the magnetic materials has been developed. Moreover, a parameter sensitivity analysis has been carried out to an optimized hysteresis coupler which satisfies the application requirements. In conclusion, the design procedure has been validated considering the experimental results obtained on a prototype of the claw pole hysteresis coupler.