Ezio Bassi

Stator Current and Motor Efficiency as Indicators for Different Types of Bearing Faults in Induction Motors

This paper proposes a new approach to use stator current and efficiency of induction motors as indicators of rolling-bearing faults. After a presentation of the state of the art about condition monitoring of vibration and motor current for the diagnostics of bearings, this paper illustrates the experimental results on four different types of bearing defects: crack in the outer race, hole in the outer race, deformation of the seal, and corrosion. The first and third faults have not been previously considered in the literature, with the latter being analyzed in other research works, even if obtained in a different way. Another novelty introduced by this paper is the analysis of the decrease in efficiency of the motor with a double purpose: as alarm of incipient faults and as evaluation of the extent of energy waste resulting from the lasting of the fault condition before the breakdown of the machine.

Electricity Smart Meters Interfacing the Households

The recent worldwide measures for energy savings call for a larger awareness of the household energy consumption, given the relevant contribution of domestic load to the national energy balance. On the other hand, electricity smart meters together with gas, heat, and water meters can be interconnected in a large network offering a potential value to implement energy savings and other energy-related services, as long as an efficient interface with the final user is implemented. Unfortunately, so far, the interface of such devices is mostly designed and addressed at the utilities supervising the system, giving them relevant advantages, while the communication with the household is often underestimated. This paper addresses this topic by proposing the definition of a local interface for smart meters, by looking at the actual European Union and international regulations, at the technological solutions available on the market, and at those implemented in different countries, and, finally, by proposing specific architectures for a proper consumer-oriented implementation of a smart meter network.

Communication protocols for electrical drives

The paper presents a review of the main communication protocols relating to industrial applications of electrical drives. In the factory automation context, drives are increasingly considered as intelligent actuators which require to exchange amount of data both mutually and with a supervising unit in order to improve the process quality. The protocols here considered are relevant either because of their diffusion in specific market areas (Profibus, FIP), or due to their specific design tailored to the drives (CAN bus, SERCOS). After a classification of the different networks, according to serial point-to-point or multipoint connection, the single protocols are reviewed in detail, by considering the most significant features from the point of view of the drive producer and user and showing how they can affect the control performances of the drives. In conclusion a comprehensive comparison table is reported for quick reference.

Powerline communication in electric vehicles

In full electric (EV) or hybrid electric (HEV) vehicles the onboard communication is a crucial issue, that can take advantage from a reliable and robust interaction among the embedded units (ECUs) providing among others the power and batteries management, services, accessories and supervision; an updated global view of the system under control (the car) can improve the quality of control, reliability, safety and comfort. Power Line Communication technology (PLC), that take advantage of the DC power line as a physical medium to exchange messages, according to standard protocols, is a candidate at substituting the actual wired solutions, by substantially reducing the cabling burden. The present paper aims at i) reviewing PLC technology for DC bus in the automotive sector; ii) defining the requirements of a reliable communication systems within a car environment, with special attention given to the data exchange needed by the more critical systems in EV and HEV, and namely the control of electrical actuators for traction; iii) describing a benchmark for testing the data transfer characteristics and performance, including details on proposed protocols and architectures and presenting experimental results on data channel characterization and transmission.

A Supervisory Sliding Mode Control Approach for Cooperative Robotic System of Systems

This paper deals with the formulation of a supervisory sliding mode (SM) control approach oriented to deal with the interesting class of system of systems of robotic nature. This class of systems is characterized by the fact of being inherently distributed, cooperative, and, possibly, heterogeneous. In this paper, we propose a modular and composable approach relying on basic modules featuring a multilevel functional architecture, including a supervisor and a couple of hybrid position/force control schemes associated with a couple of cooperative robotic manipulators. In principle, the overall robotic system we are referring to can be viewed as a collection of basic modules of that type. In this paper, we focus on the design of the basic module. The hybrid position/force control schemes therein included are based on position and force controllers. The proposed position and force controllers are of SM type, to assure suitable robustness to perform a satisfactory trajectory tracking even in presence of unavoidable modeling uncertainties and external disturbances. The verification and the validation of our proposal have been performed by simulating the supervisor and the hybrid control scheme applied to one of the two robotic manipulators while experimentally testing the position control on the other arm. The experimental part of the tests has been carried out on a COMAU SMART3-S2 anthropomorphic industrial robotic manipulator.

Use of the stator current for condition monitoring of bearings in induction motors

The aim of this paper is to verify the effectiveness of the stator current analysis for the detection of bearing problems. The paper reports the experimental results on four different types of bearing faults.

A field orientation scheme for current-fed induction motor drives based on the torque angle closed-loop control

A field orientation scheme for current-fed induction motor drives that is based on the closed-loop control of the torque angle is presented. Merits of the scheme are insensitivity to the rotor resistance and simplicity of implementation. The limits of the conventional field orientation solutions are reviewed. The scheme is then formulated, and its application to the induction motor drives fed by both current source inverters (CSIs) and current-controlled pulse width modulation (PWM) inverters is illustrated. As an example, the design of a CSI induction motor drive built up around the proposed scheme is detailed. The performance of the drive, obtained by simulation, is also given.<<ETX>>

Hybrid position/force sliding mode control of a class of robotic manipulators

This paper deals with the hybrid position/force control of a class of robotic manipulators. To perform the control scheme design, it is necessary to characterize the dynamical model of the force sensor which is mounted at the end-effector of the robot. The objective is to perform reliable contact force measurements by estimating all the forces which are generated at the level of the tip which is directly connected to the sensor. A dynamical model of the sensor motion is formulated and identified, by considering also the kinematics of the robot. The proposed hybrid control scheme includes position and force controllers based on first and second order sliding modes. These kind of controllers guarantee suitable robustness properties to perform a satisfactory trajectory tracking, also allowing one to make the robot move in an environment with unknown obstacles by using the possibility of touching the obstacles as a way to pass them by. Experimental tests are performed on a COMAU SMART3-S2 anthropomorphic rigid robot manipulator with an ATI Gamma force sensor by comparing four different position/force control schemes.

Detection of stator short circuits in inverter-fed induction motors

In this paper, an experimental investigation about the use of non-invasive instruments, like stator current and external leakage flux analysis, to detect inter-turns short-circuits in stator windings of low voltage induction motors supplied by inverter is reported. The results are encouraging and the technique here proposed can be evaluated as a tool to detect these faults in their early stage in motors which are more stressed with respect to those supplied by the mains, due to the IGBT PWM feeding.

Characterization of the Dynamical Model of a Force Sensor for Robot Manipulators

Recent advances in robotics include the capability of planning a suitable trajectory in order to drive the robot from an initial configuration to a predetermined goal point, or to follow, when possible, a prespecified trajectory even in unknown environments [8]. Various methods can be adopted to accomplish this task. These methods are mainly classified in relation to the capability of the sensors which are employed to map the environment and the obstacles near the robot. When distance sensors and cameras are considered, the trajectory can be planned without colliding with the obstacles (i.e. no force measurements are required), see [3, 12, 13].