This work proposes a unified back Active Electromotive Force (AEMF) observer for AC machines based on the SuperTwisting Algorithm (STA). This study aims to create a universal observer structure that could drive Synchronous Machines (SMs) and Induction Machines (IMs) without modifying the observer structure. It is shown that the proposed unified observer can be applied to SMs and IMs with minimum machine parameters, negating the need for machine-type knowledge, or at the very least, the rotor flux model. The active EMF, a generalized version of the original back EMF, is used to achieve this. The Lyapunov theory guarantees the convergence of the proposed observer. Finally, to confirm our theoretical results, the proposed observer was validated on a Permanent Magnet SM (PMSM) and IM using MATLAB/Simulink simulations and experimental tests conducted on a real test bench.

We show that the gradient observer proposed in Bernard & Praly, IFAC 2017 for PMSMs, can be used to estimate the stator flux of SynRMs, using only electrical measurements and the knowledge of the resistance. This sensorless observer ensures global convergence of the flux estimate provided the rotation speed and the current norm remains away from zero and the current and voltages are bounded, without requiring the knowledge of the magnetic model. Its robustness with respect to resistance errors is shown, with explicit expression of the resulting steady state error. This observer operates dynamically, in normal conditions, without any constraint on the load, and without any mechanical information. In a second step, we propose to exploit the knowledge of a magnetic inductance model (containing magnetic saturation) to estimate the rotor position from the flux estimate. The performance of this estimation in open-loop is illustrated on experimental data on a SynRM.

This paper proposes a new method to estimate the rotor flux of a Permanent-Magnet Synchronous Motor (PMSM) at standstill. This method works on motors that have enough magnetic saliency so that the reluctance torque can cancel the magnet-alignment torque. A nonlinear controller is designed to achieve standstill operation. The stability of this controller is studied using both the linearized model and nonlinear control theory. It is proven that the desired operating condition, where the rotor flux can be estimated, is locally asymptotically stable. Thanks to its bifurcation property, the proposed controller ensures zero speed for any type of PMSM, which is not the case for all existing methods. Furthermore, the estimation accuracy is made independent of the motor loading using a compensation procedure. The theoretical results are verified in simulation on an 11kW motor model.

Continuous-time Sigma-Delta (CT-ΔΣ) modulators are oversampling Analog-to-Digital converters that may provide higher sampling rates and lower power consumption than their discrete counterpart. Whereas approximation errors are established for high-order discrete time ΔΣ modulators, theoretical analysis of the error between the filtered output and the input remain scarce. This paper presents a general framework to study this error: under regularity assumptions on the input and the filtering kernel, we prove for a second-order CT-ΔΣ that the error estimate may be in o(1/N)2, where N is the oversampling ratio. The whole theory is validated by numerical experiments.

We demonstrate how the rotor position of a PWM-controlled PMSM can be recovered from the measured currents, by suitably using the excitation provided by the PWM itself. This provides the benefits of signal injection, in particular the ability to operate even at low velocity, without the drawbacks of an external probing signal. We illustrate the relevance of the approach by simulations and experimental results.

This paper introduces a set of estimators for a wide class of multiplexed signal. The signals of interest are decomposed on independent periodic signals with a shared frequency. This latter set of signals is as general as possible; that is, not necessarily orthogonal or sinusoidal. By an adequate linear combination of low-pass filters, we extract each of the components of the multiplexed signal with an arbitrary accuracy. Applications of this demodulation procedure include sensorless control of electrical machines using signal injection with the extraction of the ripple.

This paper proposes a method based on signal injection to obtain the saturated current-flux relations of a PMSM from locked-rotor experiments. With respect to the classical method based on time integration, it has the main advantage of being completely independent of the stator resistance; moreover, it is less sensitive to voltage biases due to the power inverter, as the injected signal may be fairly large.