Robust Sensorless Research Articles

Induction Motor Performance Improvement using Super Twisting SMC and Twelve Sector DTC

Induction motor (IM) direct torque control (DTC) is prone to a number of weaknesses, including uncertainty, external disturbances, and non-linear dynamics. Hysteresis controllers are used in the inner loops of this control method, whereas traditional proportional-integral (PI) controllers are used in the outer loop. A high-performance torque and speed system is consequently needed to assure a stable and reliable command that can tolerate such unsettled effects. This paper treats the design of a robust sensorless twelve-sector DTC of a three-phase IM. The speed controller is conceived based on high-order super-twisting sliding mode control with integral action (iSTSMC). The goal is to decrease the flux, torque, the current ripples that constitute the major conventional DTC drawbacks. The phase current ripples have been effectively reduced from 76.92% to 45.30% with a difference of 31.62%. A robust adaptive flux and speed observer-based fuzzy logic mechanism are inserted to get rid of the mechanical sensor. Satisfactory results have been got through simulations in MATLAB/Simulink under load disturbance. In comparison to a conventional six-sector DTC, the suggested technique has a higher performance and lower distortion rate.

Robust Sensorless Control of Synchronous Reluctance Motor Based on PDSH-KF Considering Dynamic Magnetic Saturation Effect

Robust Sensorless Control of Synchronous Reluctance Motor Based on PDSH-KF Considering Dynamic Magnetic Saturation Effect

Adaptive Robust Sensorless Control for PMSM Based on Improved Back EMF Observer and Extended State Observer

Adaptive Robust Sensorless Control for PMSM Based on Improved Back EMF Observer and Extended State Observer

Modeling and Design of a Robust Sensorless PCM Controlled Flyback Converter

Modeling and Design of a Robust Sensorless PCM Controlled Flyback Converter

Optofluidic adaptive optics in multi-photon microscopy.

Adaptive optics, in combination with multi-photon techniques, is a powerful approach to image deep into a specimen. Remarkably, virtually all adaptive optics schemes today rely on wavefront modulators that are reflective, diffractive or both. This, however, can pose a severe limitation for applications. Here, we present a fast and robust sensorless adaptive optics scheme adapted for transmissive wavefront modulators. We study our scheme in numerical simulations and in experiments with a novel, optofluidic wavefront shaping device that is transmissive, refractive, polarisation-independent, and broadband. We demonstrate scatter correction of two-photon-excited fluorescence images of microbeads as well as brain cells and benchmark our device against a liquid-crystal spatial light modulator. Our method and technology could open new routes for adaptive optics in scenarios where previously, the restriction to reflective and diffractive devices may have staggered innovation and progress.

Advanced sliding mode speed observer with compensated stray‐load and iron losses for a stand‐alone wind turbine‐driven induction generator

AbstractModel‐based speed estimation schemes in sensorless field‐oriented control (FOC) of induction machines (IMs) are designed on the basis of a corresponding mathematical model. Thus, a reliable and robust sensorless controller requires using a more detailed IM model. The omission of nonlinear phenomena in real‐time application, such as magnetic saturation, iron losses, and stray‐load losses, certainly leads to inaccuracy in the estimated speed due to the existence of the mentioned phenomena in the IM. In this context, we address here the problem of neglecting the stray‐load and iron losses in a model‐based speed observer, synthesized by means of sliding mode theory, and we evaluate the impact of this omission on the execution of the utilized FOC and maximum power point tracking (MPPT) algorithm applied for a stand‐alone wind energy conversion system (WECS). The performance of the proposed sliding mode speed observer (SMSO), derived from the IM model including the above mentioned nonlinear phenomena, is experimentally evaluated over wide ranges of wind speed and IM magnetizing flux. It is also compared with the model reference adaptive system (MRAS) speed estimator, which is derived from the same IM model, as well as to the simplified SMSO, designed based on the IM model without stray‐load and iron losses. The obtained results show that the proposed SMSO has greater robustness with respect to abrupt variations of the rotor flux in comparison with the MRAS speed estimator, whereas it ensures significantly more stable operation and lower speed estimation error in comparison with the simplified SMSO.

A Novel Robust Sensorless Technique for Field-Oriented Control Drive of Permanent Magnet Synchronous Motor

This paper proposes a novel rotor position estimation technique based on stator flux linkage to implement robust sensorless field-oriented control for permanent magnet synchronous motor drives. The proposed method can accurately estimate rotor position by mitigating the dependence on quality of the magnitude and phase angle of the estimated stator flux linkage. A high-accuracy load angle calculation based on <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$d$ </tex-math></inline-formula> - <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$q$ </tex-math></inline-formula> -axis current estimation method is first developed for further rotor position determination. In the rotor position calculation, the reference flux linkage magnitude is used instead of the estimated one to avoid the influence of potential high noise levels during low speed operation. As a result, the rotor angle estimation depends only on the phase angle of stator flux linkage, without the effect of its magnitude. The estimation accuracy can thus be improved. Also, by employing a simple stator flux linkage phase lag compensator, the performance of the proposed sensorless method can be dramatically improved at low speed. Moreover, the problem of motor parameter variation (e.g., changes in winding resistance, stator inductances, and permanent magnetic flux linkage) has been analyzed and overcome. Finally, comparisons between conventional and proposed methods are presented with simulations and experiments to demonstrate the effectiveness and reliability of the proposed method.

Robust sensorless low‐speed trajectory tracking for a permanent magnet synchronous motor: An extended state observer based backstepping control approach

This article deals with the low‐speed sensorless trajectory tracking control of a permanent magnet synchronous motor (PMSM). The rotor position and angular speed are obtained through back electromotive forces (back‐EMF), using extended state observers (ESOs) in the alpha‐beta coordinates. Additionally, the estimation of the back‐EMF is used by an algebraic module to reconstruct online the position and speed using an off‐line estimation of the back‐EMF parameter . The control law is derived using a robust recursive controller design methodology, namely; the backstepping design approach in the d‐q coordinates. Estimation schemes allow the adaptation of the angular position, angular speed, and the load torque parameters in the control law. With this adaptation, the controller achieves the necessary robustness to reduce the effects of endogenous and exogenous perturbations present in the PMSM system. The trajectory tracking task is achieved at low angular speed, with the presence of a load torque applied to the motor shaft. Experimental results at low‐speed and rated load/no‐load conditions are presented to demonstrate the effectiveness and robustness of the proposed scheme.

Robust sensorless FCS-PCC control for inverter-based induction machine systems with high-order disturbance compensation

Due to its theoretically fast dynamic response with unlimited bandwidth for direct switch-driven-based induction machines, the finite control set predictive current control (FCS-PCC) method has been verified to be an effective solution in recent years. However, dynamic limitations of the outer speed PI controller exist, especially with high-order time-varying disturbances. In addition, hardware cost can be reduced. Using the universal proportional integral observer (UPIO) method, a robust deadbeat-like encoderless-based FCS-PCC control scheme is investigated for induction machine systems in this paper. The encoder is avoided using the proposed sensorless method. In addition, the system response and disturbance attenuation are enhanced in presence of time-varying unknown load torque and uncertainties. The squared norm is adopted for the cost function design to ensure system stability. Experimental results illustrate that it has good performance such as fast dynamics, good low-speed steady-state accuracy, and robustness.

Robust Sensorless Control Against Thermally Degraded Speed Performance in an IM Drive Based Electric Vehicle

This article investigates and proposes an efficient control design to address the degradation in the mechanical speed of a traction machine drive (TMD) in an electric vehicle (EV) caused by thermal effects during its operation. Variations in the operating as well as ambient temperature cause unexpected uncertainties in TMD parameters such as stator and rotor resistances, which results in significant degradation in EV's speed performance capability. To mitigate this problem, an output feedback robust linear parameter varying (LPV) controller-observer set is designed using H <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$_{\infty }$</tex-math></inline-formula> control theory that enhances the EV's speed performance in field-oriented control (FOC) frame. The internal stability of the closed-loop control and the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$L_{2}$</tex-math></inline-formula> gain bound are ensured by linear matrix inequalities. The performance of the proposed control technique is compared with that of conventional FOC, sliding mode control (SMC) and higher order sliding mode control (HOSMC) to validate its efficacy and advantages. The robustness of the proposed control technique is tested for an EV operation against the Worldwide Harmonised Light Vehicles Test Procedure (WLTP) Class 3 driving cycle. The nonlinear MATLAB simulation results guarantee the effectiveness of the proposed controller-observer set. These results are verified experimentally on an induction machine drive setup.

A new robust sensorless vector-control strategy for wound-rotor induction motors

ABSTRACT Aim of this study is to investigate a sensor-less speed-observer with the principles of vector control for the industrial applications of Wound-Rotor Induction Motors (WRIM). The proposed estimation method is based on a simple topology to efficiently predict the rotor-speed signal with the aid of the phase axes relations of the adopted motor and using the flux orientation scheme with the indirect type (IRFOC). To effectively verify the efficacy of the presented sensor-less control system, overall results are carried out. The realised analysis validates the proposed estimation method for the rotor-speed of WRIM, which ensures its capability for sensor-less vector control methodology of the adopted system.

Sensorless Predictive Direct Power Control PDPC_SVM For PWM Converter Under Different Input Voltage Conditions

In this paper, a new virtual flux (VF) based predictive direct power control (VF_PDPC) applied for three-phase pulse width modulation (PWM) rectifier is proposed. The virtual flux estimation is performed using a pure integrator in series with a new adaptive algorithm in order to cancel dc offset and harmonic distortions in the estimated VF. The introduced structure is able to produce two virtual flux positive sequence components orthogonal output signals under unbalanced and distorted voltage conditions. The main features of the proposed virtual flux estimator are, it's simple structure, accuracy, and fast VF estimation over the excited integrators. Therefore, the estimated VF is then used for robust sensorless VF-PDPC with a constant switching frequency using space vector modulation (SVM) and tested through numerical simulations. The instantaneous active and reactive powers provided by orthogonal (VF) positive sequence components are directly controlled. More importantly, this configuration gives quasi-sinusoidal and balanced current under different input voltage conditions without using the power compensation methods. The results of the simulation confirmed the validity of the proposed virtual flux algorithm and demonstrated excellent performance under different input voltage conditions, complete rejection of disturbances.

A Robust Sensorless Controller-Observer Strategy for PMSMs with Unknown Resistance and Mechanical Model

In this work, we present a mixed sensorless strategy for Permanent Magnet Synchronous Machines, combining a torque/current controller and an observer for position, speed, flux, and stator resistance. The proposed co-design is motivated by the need for an appropriate signal injection technique to guarantee full state observability. Neither the typical constant or slowly-varying speed assumptions, nor a priori mechanical model information are required. Instead, the rotor speed is modeled as an unknown input disturbance with constant (unknown) sign and uniformly non-zero magnitude. With the proposed architecture, we show that the torque tracking and signal injection tasks can be achieved and asymptotically decoupled. Because of these features, we refer to this strategy as a sensorless controller-observer with no mechanical model. Employing a gradient descent resistance/back-EMF estimation, combined with the unit circle formalism to describe the rotor position, we prove regional practical asymptotic stability of the overall scheme. In particular, the domain of attraction can be arbitrarily large, without including a lower-dimensional manifold. The effectiveness of this design is further validated with numerical simulations, related to a challenging application of UAV propellers control.

Robust sensorless speed tracking controller for surface-mount permanent magnet synchronous motors subjected to uncertain load variations

ABSTRACTWe address a solution of the sensorless high-speed tracking control problem for surface-mount permanent magnet synchronous motors under load torque variations. Since the only available measurements are the stator currents, the proposed scheme consists of a second-order sliding-mode observer interconnected with an controller. Thus, disregarding the use of additional sensors to measure the mechanical variables. The observer-controller interconnection is robust against uncertainties and unknown load torque variations. First, the observer estimates rotor angular position and speed variables, theoretically, in finite-time. Then, an controller attenuates the effects of uniformly bounded disturbances. Sufficient conditions are provided to ensure that the closed-loop system is stable. Moreover, it is internally asymptotically stable in the absence of uncertainties and external disturbances. The analysis shows that the observer-controller system possesses an -gain less than a priori given disturbance attenuation level. Emulation trials showed the feasibility of the method.

A Simple and Robust Sensorless Control Based on Stator Current Vector for PMSG Wind Power Systems

This paper proposes a novel sensorless control based on the stator current vector for permanent-magnet synchronous generators in variable-speed wind energy conversion systems. In the proposed method, the rotor angle and speed are estimated indirectly from the stator currents, where only the stator inductance is required regardless of the stator resistance. In addition, the proposed method uses one current control loop to regulate the stator current magnitude, rather than two current control loops. To eliminate the current measurement noise, the second-order generalized integrator (SOGI) with a frequency-locked loop (FLL) is utilized, which can improve the estimation performance. The proposed sensorless control method with the SOGI-FLL is simple and easy to implement while achieving a fast and accurate estimation performance of the rotor angle and speed. The feasibility of the proposed method has been verified by simulation and experimental results.

Control of Permanent Magnet Synchronous Machines for Subsea Applications

Permanent magnet synchronous motor (PMSM)-driven subsea pumps have the potential to lower the operating costs of subsea pumping modules by improving efficiency, enhancing reliability, and by reducing weight and size. The higher operating speed of PMSM compared with an induction motor of similar size allows for a wider operating envelope for the pump, including operation in high gas volume fractions scenarios. In applying rotor-oriented sensorless vector control to the adjustable speed drive (ASD), the influence of output filters, long motor cables, and transformer between the ASD and the motor needs to be considered. These additional components in the motor circuit make it difficult to estimate correct rotor position during starting. In addition, sensorless vector control is very sensitive to parameter variations. This paper presents simulations and experimental results of a robust sensorless vector control strategy, called voltage vector control for a PMSM driving a high-power subsea pump. The test inverter was a low-voltage insulated-gate bipolar transistor inverter with neutral point clamped topology. This inverter was used driving a PMSM for testing of the control strategy, with an aim of expanding this concept to medium-voltage ASDs.

Robust sensorless observer-based adaptive sliding modes control of synchronous motors

Using a nonlinear complete order model of a synchronous motor, a robust second order sliding mode observer based control scheme is proposed. For that, a generalized super-twisting 3rd order observer is proposed for nonlinear systems. Based on the proposed observer scheme, a robust rotor flux observer is designed, then, a stator current observer is proposed using a classical super-twisting algorithm for extracting information of the rotor speed by means of the equivalent control method. The control design for the output tracking of a desired reference signal for the rotor speed is carried out with a classical super-twisting sliding mode algorithm and adaptive backstepping techniques. Due to the number of inputs, the flux in the excitation winding, and the direct component of the stator currents are also regulated. Numeric simulations predict a good performance of the closed-loop synchronous motor with parameter variations.

Sensorless Control Strategy of a 315 kW High-Speed BLDC Motor Based on a Speed-Independent Flux Linkage Function

A sensorless control strategy of a high-speed 315 kW brushless dc (BLDC) motor based on a speed-independent flux linkage function is proposed in this paper. It addresses the two key challenges on the sensorless control of high-speed BLDC motor: proposing a speed-independent flux linkage function to ensure reliable operation in the low-speed range, and presenting correction strategy to provide accurate commutation points in the high-speed range. First, the sensorless detection circuit model of a 315 kW BLDC motor is discussed. The analysis shows that the speed-independent flux linkage function is really suitable for BLDC motor sensorless control strategy in the low-speed range. Then, an improved closed-loop system based on the change of current in the full speed range is proposed. The experimental results show that the proposed control strategy can provide a highly accurate and robust sensorless operation from near zero to 20 000 r/min.

A Robust Sensorless Control of PMSM Based on Sliding Mode Observer and Model Reference Adaptive System

&lt;p&gt;This paper is intended to study and compare the operation of two methods for estimating the position/ speed of the permanent magnet synchronous motor (PMSM) under sliding mode control. The first method is a model reference adaptive system (MRAS). The second method based on sliding mode observer (SMO). The stability condition of Sliding Mode Observer was verified using the Lyapunov method to make sure that the observer is stable in converging to the sliding mode plane. In this paper the performances of the proposed two algorithms are analyzed using SIMULINK/MATLAB. The simulations results are presented to verify the proposed sensorless control algorithms and can resolve the problem of load disturbance effects by simulations which verify that the two closed-loop control system is robust with respect to torque disturbance rejection.&lt;/p&gt;

Robust hybrid sensorless control of variable speed wind turbine with permanent magnet synchronous generator

Robust hybrid sensorless control of variable speed wind turbine with permanent magnet synchronous generator