Bruno Lequesne

Four-Quadrant Pulse Injection and Sliding-Mode-Observer-Based Sensorless Operation of a Switched Reluctance Machine Over Entire Speed Range Including Zero Speed

The objective of this paper is to present a sensorless position estimation technique for switched reluctance machines (SRM) operating in constant dynamic mode over a wide speed range including zero speed. The technique combines two different methods to deliver high resolution position information over the wide speed range. At zero and low speeds, a voltage pulse injection method is used to estimate the rotor position in all four quadrants. For higher speeds, a sliding mode observer (SMO) based algorithm is used and combined to work with the low speed algorithm. Experimental results demonstrate the effectiveness of this new combined technique that has four-quadrant operation capability.

Design and testing of a belt-driven induction starter-generator

The advent of higher voltages in automobiles constitutes an opportunity for new electrical features and systems. In that regard, a combined starter-generator would have several important benefits, most notably it would enable the turning off of the engine at idle and provide efficient, high power generation, both resulting in improved fuel economy. Several ongoing starter-generator projects have focused on locating the starter-generator around the engine flywheel. This paper describes the design of a belt-driven alternative with an induction machine drive. The proposed system would be easier to package than a flywheel-mounted system, since it would not affect the overall length of the powertrain. The paper presents various models as well as test results from a prototype system. Some specific implementation issues, such as induction generator stability at high speed, are also explored in some depth.

Four-quadrant and zero-speed sensorless control of a switched reluctance motor

A four-quadrant sensorless controller for switched reluctance motor (SRM) drives is presented in this paper. The drive system with appropriate turn-on and turn-off angles for each operating quadrant delivers excellent dynamic performance over a wide speed range including zero speed. The problems associated with practical implementation especially at low and zero speeds have been addressed and overcome with engineering solutions. Experimental results for a 1-kW SRM obtained on a dSPACE-based system are presented along with useful guidelines for practical implementation.

Integrated magnetic field sensor

A magnetic field sensor, such as a magnetoresistor, includes a strip of a layer of a high electron mobility semiconductor whose electrical characteristics vary when a magnetic field is applied thereto on the surface of a body (substrate) of an insulating layer. Conductive contacts are on the strip at the ends thereof and conductive shorting bars are on and spaced along the strip to divide the strip into active regions. The body is mounted on a permanent magnet assembly which includes a magnet and a layer of a ferromagnetic material with the ferromagnetic material extending over the strip. The ferromagnetic layer is in close proximity to only the strip and, more preferably, to only the active regions of the strip so as to confine the magnetic field to the strip.

Winding short circuits in the switched reluctance drive

The switched reluctance drive is known to be fault tolerant, but it is not fault free. This paper takes an in-depth look at winding short circuits in this particular machine. Modeling and testing complement a theoretical analysis. Two cases need to be distinguished, one where a complete pole is shorted, and one where a few turns are shorted. Pole short circuits lead to torque reduction that can be easily compensated for with increased current. With few turns shorted, the impact on overall torque may actually be negligible, however, significant currents may circulate through the shorted turns, the worst case being with a single turn shorted with a zero resistance. These results are discussed with a view toward possible remediation schemes aside from simply turning off the faulted phase.

Fast-acting, long-stroke solenoids with two springs

A device with two oscillating springs controlled electromagnetically is studied both theoretically and experimentally. The mathematical model, based on finite-element analysis, consists of a dynamic model of motion which includes all relevant physical phenomena with the exception of eddy currents, which are then evaluated separately. The tests verify the mathematical model, quantify the possible time-versus-energy-input characteristic for a given stroke and volume, and allow comparison of this concept with a previously studied approach where repulsion forces are exerted on a moving permanent magnet. The latter is superior when the actuator is required to provide mechanical work in addition to fast motion over a long stroke, while the two-spring actuator is faster and uses less energy when motion alone is desired.<<ETX>>

Finite-element analysis of a constant-force solenoid for fluid flow control

A model for constant-force solenoids based on the finite-element method is presented. The total force exerted by the solenoid is calculated and compared with test results. The force calculation algorithm is also used to determine the force distribution pattern around the plunger surface, and to provide a detailed analysis of the solenoid structure. The model was successfully implemented to improve a solenoid design. The finite-element package is shown to be a powerful design tool, capable of accurate performance prediction. The analysis process shows the importance of the truncated-cone shape of the plunger, of balancing the forces produced by the tapered and flat portions of the plunger surface, and of matching the respective positions of the plunger and of the facing pole. >

Nonlinear two-dimensional finite element modeling of permanent magnet eddy current couplings and brakes

A two-dimensional finite element model is developed to model the electromagnetic behavior of permanent magnet type eddy current couplers under constant speed operation. The model accounts for the nonlinearity of the steel flux paths and is verified using test measurements from a prototype eddy current coupler. The proposed solution differs from conventional magnetostatic finite element models in that an unknown current-density distribution must be determined through an iterative process. The model is used to study the influence of certain design parameters on the torque-speed characteristics of such devices. >

Current/Voltage-Based Detection of Faults in Gears Coupled to Electric Motors

Gears form a critical part of many electro-mechanical systems. Since gear faults cause vibrations, and vibration-based diagnostics is very reliable, this has traditionally been the most commonly used approach to detecting gear faults. However, it is expensive due to the use of high-priced accelerometers and sensor wiring. This paper proposes an alternative way of detecting faults in gears coupled to BLDC motors by monitoring either the motor current or voltage. It is shown that gear faults create unique spectral components in the voltage and current spectrums. The faults investigated in this paper include damage to gear teeth and loss of lubrication. Experimental and simulation results demonstrate that motor current/voltage signature analysis is a viable tool to detect these gear faults, and is a cheaper alternative than vibration based fault detection schemes

Dynamic model of solenoids under impact excitation, including motion and eddy currents

Modeling of solenoids activated from a DC source (impact excitation) is difficult because of the coupling of a nonlinear magnetic system, which indicates eddy currents, with a mechanical system that involves a time-varying gap. While the finite-element method in two dimensions has been successfully implemented to solve this complex problem, the large number of successive iterations involved makes it inconvenient when repeated design trials are made, for instance, during optimization. It is shown that the problem geometry, including eddy currents, can be satisfactorily approximated using only one dimension. The resulting set of equations is solved using the finite-difference method. Comparisons with test data and with two-dimensional finite-element calculations are conclusive. The proposed model can be used for the assessment of any solenoid, including fast-acting devices. The resulting algorithm converges rapidly, a desirable feature during a design process where many runs are necessary. >