939 research outputs found

    Detection and Diagnosis of Motor Stator Faults using Electric Signals from Variable Speed Drives

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    Motor current signature analysis has been investigated widely for diagnosing faults of induction motors. However, most of these studies are based on open loop drives. This paper examines the performance of diagnosing motor stator faults under both open and closed loop operation modes. It examines the effectiveness of conventional diagnosis features in both motor current and voltage signals using spectrum analysis. Evaluation results show that the stator fault causes an increase in the sideband amplitude of motor current signature only when the motor is under the open loop control. However, the increase in sidebands can be observed in both the current and voltage signals under the sensorless control mode, showing that it is more promising in diagnosing the stator faults under the sensorless control operation

    Speed -Sensorless Estimation And Position Control Of Induction Motors For Motion Control Applications

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    Thesis (Ph.D.) University of Alaska Fairbanks, 2006High performance sensorless position control of induction motors (IMs) calls for estimation and control schemes which offer solutions to parameter uncertainties as well as to difficulties involved with accurate flux and velocity estimation at very low and zero speed. In this thesis, novel control and estimation methods have been developed to address these challenges. The proposed estimation algorithms are designed to minimize estimation error in both transient and steady-state over a wide velocity range, including very low and persistent zero speed operation. To this aim, initially single Extended Kalman Filter (EKF) algorithms are designed to estimate the flux, load torque, and velocity, as well as the rotor, Rr' or stator, Rs resistances. The temperature and frequency related variations of these parameters are well-known challenges in the estimation and control of IMs, and are subject to ongoing research. To further improve estimation and control performance in this thesis, a novel EKF approach is also developed which can achieve the simultaneous estimation of R r' and Rs for the first time in the sensorless IM control literature. The so-called Switching and Braided EKF algorithms are tested through experiments conducted under challenging parameter variations over a wide speed range, including under persistent operation at zero speed. Finally, in this thesis, a sensorless position control method is also designed using a new sliding mode controller (SMC) with reduced chattering. The results obtained with the proposed control and estimation schemes appear to be very compatible and many times superior to existing literature results for sensorless control of IMs in the very low and zero speed range. The developed estimation and control schemes could also be used with a variety of the sensorless speed and position control applications, which are challenged by a high number of parameter uncertainties

    A Sensorless Direct Torque Control Scheme Suitable for Electric Vehicles

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    International audienceIn this paper a sensorless control is proposed to increase the efficiency of a Direct Torque Control (DTC) of an induction motor propelling an Electric Vehicle (EV). The proposed scheme uses an adaptive flux and speed observer that is based on a full order model of the induction motor. Moreover, it is evaluated on an EV global model taking into account the vehicle dynamics. Simulations were first carried out on a test vehicle propelled by a 37-kW induction motor to evaluate the consistency and the performance of the proposed control approach. The commonly used European drive cycle ECE-15 is adopted for simulation. The obtained results seem to be very promising. Then, the proposed control approach was experimentally implemented, on a TMS320F240 DSP-based development board, and tested on 1-kW induction motor. Experimental results show that the proposed control scheme is effective in terms of speed and torque performances. Indeed, it allows speed and torque ripple minimization. Moreover, the obtained results show that the proposed sensorless DTC scheme for induction motors is a good candidate for EVs propulsion

    Model predictive MRAS estimator for sensorless induction motor drives

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    Ph. D. ThesisThe project presents a novel model predictive reference adaptive system (MRAS) speed observer for sensorless induction motor drives applications. The proposed observer is based on the finite control set-model predictive control principle. The rotor position is calculated using a search-based optimization algorithm which ensures a minimum speed tuning error signal at each sampling period. This eliminates the need for a proportional integral (PI) controller which is conventionally employed in the adaption mechanism of MRAS observers. Extensive simulation and experimental tests have been carried out to evaluate the performance of the proposed observer. Both the simulation and the experimental results show improved performance of the MRAS scheme in both open and closed-loop sensorless modes of operation at low speeds and with different loading conditions including regeneration. The proposed scheme also improves the system robustness against motor parameter variations and increases the maximum bandwidth of the speed loop controller. However, some of the experimental results show oscillations in the estimated rotor speed, especially at light loading conditions. Furthermore, due to the use of the voltage equation in the reference model, the scheme remains sensitive, to a certain extent, to the variations in the machine parameters. Therefore, to reduce rotor speed oscillations at light loading conditions, an adaptive filter is employed in the speed extraction mechanism, where an adaptation mechanism is proposed to adapt the filter time constant depending on the dynamic state of the system. Furthermore, a voltage compensating method is employed in the reference model of the MP-MRAS observer to address the problems associated with sensitivity to motor parameter variation. The performance of the proposed scheme is evaluated both experimentally and by simulation. Results confirm the effectiveness of the proposed scheme for sensorless speed control of IM drives

    Sensorless And Independent Speed Control Of Dual-PMSM Drives Using Five-Leg Inverter (FLI)

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    This research aims to develop and implement a combined sensorless and independent speed control for dual-PMSM (Permanent Magnet Synchronous Motor) drives fed by a single Five-Leg Inverter (FLI). Dual-motor drives are widely used in high traction power industry such as propulsion system, aircraft, locomotive, Hybrid Electric Vehicle (HEV) and others. In general, dual-motor drives are designed to reduce size and cost with respect to single motor drives. However, dual-motor drives using a single three-leg inverter has its limitation in the case of operation at different operating conditions and independent speed control requirement. Recent research has shown that, dual motor drives can be independently controlled by using Five-Leg inverter (FLI). By employing this FLI topology, the dual-motor drives can be used for four-quadrant control, variable speed operation and load disturbance rejection. In other words, it can be operated for different applications. In the case of conventional dual-PMSM drives, the drives system still requires current sensors and voltage transducers for speed and rotor position estimation. In PMSM drives, the information of the feedback speed and rotor angular position is compulsory. Therefore, this research is trying to implement a combined sensorless and independent speed control for dual PMSM drives system and at the same time eliminating the usage of voltage transducers. This thesis investigates the behavior of sensorless and independent speed control for Dual-Permanent Magnet Synchronous Motor (PMSM) drives. Initially, a single PMSM drives is designed and simulated, followed by the development of Dual-PMSM drives model. The speed and current controllers are implemented in d-q rotor reference frame using Simulink/MATLAB and the switching signals are generated by the built-in function and dSPACE. Then, the sensorless drive system is developed based on adaptive speed and position estimator. The overall performance of the drives is investigated and evaluated in terms of speed responses overshoot under variation of speed reference and speed drop under load torque disturbances. The simulation results have proved that the performance characteristics of sensorless dual-PMSM are almost similar with system using sensor except during the start-up condition. The motor performance is degraded in terms of speed overshoot for small and medium speed reference or when the motor operates far from the designed operating condition (rated value). The proposed independent dual-PMSM drives fed by FLI have better load rejection capability compared with conventional dual-PMSM drives fed by single three-phase inverter. The experimental results of the drives under investigation have shown acceptable correlation between the theoretical and simulation

    Sensorless speed control of a vector controlled three-phase induction motor drive by using MRAS

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    A method for rotor speed estimation using model reference adaptive system (MRAS) was proposed to improve the performance of a sensorless vector controller. State variables, such as rotor flux and reactive power were estimated in a reference model and then compared with state variables obtained by using space vector modulation (SVM) algorithm. In conventional MRAS methods, the difference between state variables and the speed estimation error is unclear. However, in this study, the stator current error was represented as functions of state variables and reference axis parameters. It was aimed that the applied model can control voltage and moment producing components of the stator separetely. The induction motor working at low speeds and zero speed was used at producing constant moments. It could be controlled in a wide range of speed due to the fact that the mathematical model provides attainable speeds to mechanical limits of the motor. Experimental verification was also provided. It was concluded that application of vector control for the sensorless speed control in induction motors results in better and rapid response and more simple structure comparing to the classical methods

    Sensorless control for limp-home mode of EV applications

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    PhD ThesisOver the past decade research into electric vehicles’ (EVs) safety, reliability and availability has become a hot topic and has attracted a lot of attention in the literature. Inevitably these key areas require further study and improvement. One of the challenges EVs face is speed/position sensor failure due to vibration and harsh environments. Wires connecting the sensor to the motor controller have a high likelihood of breakage. Loss of signals from the speed/position sensor will bring the EV to halt mode. Speed sensor failure at a busy roundabout or on a high speed motorway can have serious consequences and put the lives of drivers and passengers in great danger. This thesis aims to tackle the aforementioned issues by proposing several novel sensorless schemes based on Model Reference Adaptive Systems (MRAS) suitable for limp-home mode of EV applications. The estimated speed from these schemes is used for the rotor flux position estimation. The estimated rotor flux position is employed for sensorless torque-controlled drive (TCD) based on indirect rotor field oriented control (IRFOC). The capabilities of the proposed schemes have been evaluated and compared to the conventional back-Electromotive Force MRAS (back-EMF MRAS) scheme using simulation environment and a test bench setup. The new schemes have also been tested on electric golf buggies. The results presented for the proposed schemes show that utilising these schemes provide a reliable and smooth sensorless operation during vehicle test-drive starting from standstill and over a wide range of speeds, including the field weakening region. Employing these new schemes for sensorless TCD in limp-home mode of EV applications increases safety, reliability and availability of EVs
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