Online trajectory planner with constraints on velocity, acceleration and torque

A filter for trajectories smoothing is presented. The filter provides an output reproducing the input trajectory if this is compliant with given constraints on the velocity, the acceleration and the torque required for tracking it. Otherwise, the filter approximates the input profile guaranteeing that the output trajectory satisfies all the kinematic and dynamic limits. The tracking of the input signal is optimal in the sense that at each time instant the limit value of one among velocity, acceleration and torque is reached. The filter, based on a variable structure controller, is designed in the continuous-time domain but can be implemented by discretization as a sampled system. It can therefore used in mechatronic and robotic applications driven by digital controllers in order to filter trajectories planned without considering the above mentioned constraints or to generate realtime smooth trajectories by simply providing basic inputs such as step or ramp functions

Power Flow Efficiency of Linear and Nonlinear Physical Systems

In this paper, an analytical procedure to derive the efficiency of linear and nonlinear physical systems is presented. This procedure allows to compute the efficiency map both on the plane of the input power variables and on the plane of the output power variables. Additionally, the paper highlights the parameters to be adjusted in order to enlarge the high-efficiency region of the system. The presented procedure can also be used in conjunction with a least square algorithm in order to estimate the unknown parameters of the considered physical system. The effectiveness of the procedure has been tested in Matlab/Simulink to estimate the parameters of an actual PMSM electric motor. The obtained results show a very good matching between the actual and the estimated efficiency maps

Modeling and Simulation of a Multiphase Diode Bridge Rectifier

In this paper, an analytical approach for modeling a multiphase diode bridge rectifier suitable for control purposes is presented. The model has been implemented in Matlab/Simulink by means of a function performing the AC/DC current conversion and takes into account the main non-idealities of semiconductor diodes, such as the turn-on voltage and the on/off resistances. The developed Matlab function makes the simulation of the multiphase diode bridge rectifier very straightforward and its effectiveness has been tested by comparing the simulation results with those obtained by using the rectifier model provided by the PLECS circuit simulator

Planetary Gear Modeling Using the Power-Oriented Graphs Technique

In this paper, the Power-Oriented Graphs (POG) technique is used to model Planetary Gear transmission systems. The full elastic dynamic model of the system is obtained using a fast and direct method which can be easily applied to any type of planetary gear. The rigid and reduced dynamic model of the system when the stiffness coefficients go to infinity is then obtained using a POG congruent state space transformation allowing the user to select which angular speeds are to be maintained in the reduced model. Another interesting aspect of the presented method is that the obtained reduced model is still able to provide the time behaviors of the tangential forces present between each couple of gears of the considered planetary gear system. The presented fast and direct method is then applied to two practical case studies, and simulative results in Matlab/Simulink showing the effectiveness of the method are finally reported and commented

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

Modeling and Control of a Power-Split Hybrid Propulsion System

In questo articolo, la tecnica modellistica Power-Oriented Graphs (POG) è utilizzata per modellare un sistema di propulsione ibrido per un attrezzo agricolo. Gli elementi principali presenti nel sistema sono: un ICE (Internal Combustion Engine), due PMSMs (Permanent Magnet Synchronous Electric Motors) equipaggiati con due inverters in modo da essere opportunamente controllati, una planetary gear, un sistema di accumulo energia ed un attrezzo agricolo. Sulla base del modello dinamico del sistema, una strategia di controllo dedicata è stata sviluppata, la quale consente di controllare in maniera efficace il sistema riducendo il consumo specifico dell'ICE il più possibile. Risultati di simulazione che mostrano il funzionamento della strategia di controllo sono infine presentati e commentati nel dettaglio.In this paper, the Power-Oriented Graphs (POG) technique is used to model a Hybrid Propulsion System for driving an agricultural tool. The main elements present in the system are: an ICE (Internal Combustion Engine), two PMSMs (Permanent Magnet Synchronous Electric Motors) equipped with two inverters in order to be properly driven, a planetary gear, an energy storage device and an agricultural tool. Based on the system dynamic model, a dedicated control strategy has been developed allowing to efficiently control the system by reducing the ICE specific consumption as much as possible. Simulation results showing the operation of the control strategy are finally reported and commented in detail

Modeling of Complex Planetary Gear Sets using Power-Oriented Graphs

In this paper, a systematic approach for the dynamic modeling of complex planetary gear sets is presented. The approach relies upon a set of rules for building the system matrices and vectors of the system full dynamic model for any planetary gear set. A congruent state-space transformation is applied to obtain a reduced-order rigid model of the system, which allows for faster simulations. The behavior of the tangential forces accounting for the gears interactions is proven to be obtained from the reduced-order model. Furthermore, the kinematic relations of the considered planetary gear set are automatically generated when developing the reduced-order rigid model. As an example, two systems of interest in the vehicle industry are then modeled with the proposed approach and simulated in Matlab/Simulink: a Ravigneaux planetary gear set and a double-stage planetary gear set

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

Qualitative graphical representation of Nyquist plots

In this paper, the procedure for manually drawing the Nyquist plot of a generic transfer function is revised and, in particular, two novel parameters (\u394\u3c4\u394\u3c4, \u394p\u394p), which allow to simplify this process, are presented. Thanks to these parameters, the analysis of the frequency response at low and high frequencies is considerably enhanced, with a very little effort. These parameters allow to predict initial and final directions of the polar curve in the vicinity of initial and final points and consequently the sectors of the complex plane where the plot starts/ends. In many cases it is possible to obtain a qualitative Nyquist plot, able to correctly predict the stability properties of the closed-loop system, by simply joining the initial and final tracts found with the proposed procedure. Moreover, the analysis based on these parameters can aid to correctly interpret the plots obtained with computer programs which often, in particular when poles at the origin are present, hide the behavior of the frequency response in the area close to the origin of the complex plane