Michael C. Harke

Erratum to "Implementation Issues and Performance Evaluation of Sinusoidal, Surface-Mounted PM Machine Drives With Hall-Effect Position Sensors and a Vector-Tracking Observer"

This paper presents the implementation and evaluation of a high-resolution position estimation system for sinusoidal, surface phase modulation machines based on Hall-effect sensors and a vector-tracking observer. First, the tuning of the observer is presented and a speed-dependent gain scheduling strategy is proposed. Then various harmonic decoupling strategies are investigated to improve the performance of the observer, particularly at low speeds. Stability analysis is performed leading to the definition of local stability limits, within which the actual position is tracked with bounded estimation error. Both simulation and experimental testing illustrate the performance and limitations of the proposed observer topology and of the drive when this observer is used for state feedback.

Current Measurement Gain Tuning Using High Frequency Signal Injection

Accurate measurement of the phase currents in electric machines is a requirement for most high performance drives. Incorrect current measurement gain estimates, caused by device tolerances, temperature drifts, age and noise, reduce the accuracy of the current measurements and degrade the drives performance. This paper presents a method for compensating current measurement gain errors using a periodically injected, high frequency voltage. The positive and negative sequence components of the resulting high frequency current are measured and used for balancing and scaling the phase current measurement gains. The method can be used either as part of an initial commissioning, or start-up sequence, or periodically during the regular operation of the machine.

The Spatial Effect and Compensation ofCurrent Sensor Differential Gains for Three-Phase Three-Wire Systems

Current sensor errors affect torque control and saliency-tracking position estimation of AC machines. In this paper, a spatial model of current sensor gain deviation is developed and used to determine its effect on general current measurement, verified with experimental data. Three current sensors enable a three-phase three-wire system to compensate for current sensor differential gains independent of additional machine saliencies. Simulation and experimental results confirm the current sensor gain-deviation compensation algorithm.

Sinusoidal surface-mounted pm machine drive using a minimal resolution position encoder

This paper presents a high resolution position estimation system for sinusoidal surface PM machines based on a vector-tracking observer and a 90deg resolution encoder. It is shown here that this is the minimum amount of resolution needed for sinusoidal PM drives. The key implementation issues of this system are presented, and stability analysis is performed, leading to the definition of local stability limits, within which the actual position is tracked with bounded estimation error. The effect that non-uniform sector widths have on position estimation is also explored and a straightforward compensation method is proposed. Both simulation and experimental testing illustrate the performance and limitations of the proposed observer topology and of the drive when this observer is used for state feedback.

SPMSM Design Considerations for Initial Position and Magnet Polarity Estimation using Carrier Signal Injection

Initial position and magnet polarity estimation is required for smooth start-up of permanent magnet synchronous machines. The signal-to-noise ratio of the salient signals used for initial position and magnet polarity estimation depends on the machine design and affects the overall performance of the estimation technique. This paper investigates the design of a ring-magnet, surface permanent magnet synchronous machine to maximize the signal-to-noise ratio of the position and polarity signals without compromising the machine performance. Since the rotor geometry is fixed given the ring-magnet, the effect of the stator tooth tip geometry on the saliency signals is evaluated using finite element analysis. By adding a bridge between the stator teeth, the magnitude of the polarity-based signal can be increased significantly. A coupled simulation verifies the implementation of the improved initial position and magnet polarity estimation based on modified machine design.

The Spatial Effect and Compensation of Current Sensor Gain Deviation for Three-phase Three-wire Systems

Current sensor errors affect torque control and saliency-tracking position estimation of ac machines. A spatial model of current sensor gain deviation is developed and used to determine its affect on a general current measurement, verified with experimental data. Three current sensors enable a three-phase three-wire system to compensate for current sensor gain deviation independent of additional machine saliencies. Simulation and experimental results confirm the current sensor gain deviation compensation algorithm.

Load invariant sensorless control of a SRM drive using high frequency signal injection

This work presents a load invariant position estimation technique for switched reluctance machine (SRM) drives based on high frequency signal injection methods. A high frequency rotating voltage vector is superimposed on the main excitation. The spatial saliency information is extracted using synchronous reference frame filtering. A robust position estimate is achieved by using an observer to track the spatial saliency. The theoretical spatial saliencies for a three-phase SRM can be derived using the doubly salient model of the machine. The proposed method is capable of providing continuous dynamic position estimation from zero to mid-range speeds with negligible load dependency.