Study of the Bidirectional Efficiency of Linear and Nonlinear Physical Systems

In questo articolo, uno studio dell'efficienza bidirezionale dei sistemi lineari e non lineari è presentato. La metodologia per calcolare la mappa di efficienza bidirezionale del sistema è descritta, evidenziando l'orientamento del flusso di potenza che da la massima efficienza del sistema. Il progettista può quindi facilmente valutare se un determinato sistema fisico, quale ad esempio una macchina elettrica, è più adatto ad essere utilizzato in modalità diretta piuttosto che in modalità inversa come generatore, o viceversa. Tre diversi tipi di sistemi fisici sono modellati e simulati in Matlab/Simulink, e le diverse caratteristiche che esibiscono in termini di efficienza sono messe in evidenza. Infine, le proprietà che le mappe di efficienza esibiscono se il sistema lineare è affetto da non linearità simmetriche o non simmetriche sono studiate e commentate nel dettaglio.In this paper, a study of the bidirectional efficiency of linear and nonlinear physical systems is performed. The methodology to compute the bidirectional efficiency map of the system is described, highlighting which is the power flow orientation giving the maximum system efficiency. The designer can therefore easily evaluate whether a physical system, such as for instance an electric machine, is more suitable for being used in forward motor mode rather than in reverse generator mode or viceversa. Three different types of physical systems are modeled and simulated in Matlab/Simulink, and the different characteristics they exhibit in terms of efficiency are highlighted. Finally, the properties that the efficiency maps exhibit if the linear system is affected by symmetric or nonsymmetric nonlinearities are studied and commented in detail

A unified methodology for the power efficiency analysis of physical systems

In this paper, the problem of power efficiency evaluation for ports physical systems is investigated. The efficiency analysis that we perform highlights the necessary and sufficient conditions for the system to be passive, and outlines the guidelines for the efficiency maps computation. After addressing the problem from a formal point of view, the analysis is deepened for the case of two-ports linear and nonlinear physical systems, and for the cases of three and four-ports linear systems. The efficiency analysis and the computation of the efficiency maps are addressed as a function of the power variables characterizing all the energetic ports of the considered systems. Furthermore, the salient properties of the efficiency are highlighted and discussed. The theoretical analysis which is developed is then applied to some physical systems of interest for industries and engineers working in the electromechanical, hydraulic and automotive fields: a DC electric motor driving an hydraulic pump for the two-ports systems class, a single-stage planetary gear set for the three-ports systems class, and a Ravigneaux planetary gear set for the four-ports systems class