Including Zero Speed Research Articles

Rotor Flux Estimator Design With Offset Extractor for Sensorless-Driven Induction Motors

In sensorless drive of induction motors (IMs), the design of a voltage model (VM) for flux estimation is challenging because of its inherent problems with dc saturation and drift. In the implementation of VM, various strategies have been studied in the flux estimator design. The closed-loop (CL) style flux estimator is a popular scheme owing to its good performance in a wide speed range. However, the CL style suffers from dc drift problems because of an offset at the back electromotive force. Based on the fact that dc drift always persists in the CL style flux estimator, this article proposes an offset extractor (OE) using a parallel structure of two CL style flux estimators. Moreover, a crossover strategy is applied to the comparative flux used in the CL scheme. This strategy guarantees low-speed operation including zero speed. When offset compensation using the proposed OE is applied to the flux estimator in a feedforward manner, the proposed flux estimator exhibits good performance in a wide speed range with robustness to the offset. Compared with the conventional methods, the proposed OE and flux estimator are verified in various situations by simulation and experiment in a sensorless-driven IM.

Stator Current-Based Model Reference Adaptive Control for Sensorless Speed Control of the Induction Motor

This paper described that the stator current-based model reference adaptive system (MRAS) speed estimator is used for the induction motor (IM) indirect vector speed control without a mechanical speed sensor. Due to high sensitivity of motor parameters variation at low speed including zero, stability analysis of MRAS design is performed to correct any mismatch parameters value in the MRAS performed to estimate the motor speed at these values. As a result, the IM sensorless control can operate over a wide range including zero speed. The performance of the stator current-based MRAS speed estimator was analyzed in terms of speed tracking capability, torque response quickness, low speed behavior, step response of drive with speed reversal, sensitivity to motor parameter uncertainty, and speed tracking ability in the regenerative mode. The system gives a good performance at no-load and loaded conditions with parameter variation. The stator current-based MRAS estimator sensorless speed control technique can make the hardware simple and improve the reliability of the motor without introducing a feedback sensor, and it becomes more important in the modern AC IM. The sensorless vector control operation has been verified by simulation on Matlab and experimentally using Texas Instruments HVMTRPFCKIT with TMS320 F28035 DSP card and 0.18 kw AC IM.

Research on Rotor Position Self-Sensing Control System of a PMSM for Electric Vehicles

There are many problems existing in the traditional rotor position self-Sensing control. To overcome these problems, a hybrid approach of rotor position self-sensing control based on a PMSM for Electric Vehicles is investigated in this paper. The proposed method has good robustness and position tracking performance at full speed including zero speed. Based on the proposed algorithm, a PMSM position self-Sensing control system is set up. Simulation and experiment are implemented on the platform. The results verify the feasibility and effectiveness of the proposed method.

Modeling and Simulation of Disc Brake Resistance Load in Low Speed Condition

In this paper, the load simulation of tracked vehicle disc brake in low speed is discussed. The simulation of the resistance load and the control of the disc brake is researched when the resistance load loading on the test bench The simulation results show that, by controlling the input voltage of the disc brake electrohydraulic control portion, the disc brake braking torque can be controlled, the driving resistance simulation of crawler vehicle is realized. At the same time, the simulation has high accuracy, fast response speed, and has better dynamic characteristic. When the tracked vehicle is at the process of start, acceleration, deceleration, braking, steering , the engine and the transmission system mainly are in an unstable vehicle system dynamic, the load is dynamic load must be given. In order to investigate the performance of tracked vehicle HMCVT, a dynamic load [1] in the test system to simulate the loading process of tracked vehicle. Eddy current dynamometer can simulate the load [2,3] during a vehicle running a higher speed , the driving load in low speed ( including zero speed ) is simulated by disc brakes .

A Composite Approach of Sensorless Rotor Position Sensing for Brushless DC Motor

The principles and characteristics of the sensorless brushless DC motor rotor position detection were analyzed by using inductive method and third harmonic back-EMF detection method. A composite rotor position detection method was proposed in full speed range (including zero speed). At zero speed (static state) inductive method was used to determine the initial rotor position, and it was bases of starting and controlling for the brushless DC motor; at low speed third harmonic back EMF detection method was used. Analysis shows that the composite test method can estimate the rotor position, and it is to achieve the position sensorless brushless DC motor to run a viable method.

Simulation studies on model reference adaptive controller based speed estimation technique for the vector controlled permanent magnet synchronous motor drive

This paper presents a speed estimation technique for the permanent magnet synchronous motor drive. A Model Reference Adaptive System (MRAS) has been formed using the instantaneous and steady-state reactive powers to estimate the speed. It has been shown that such unique MRAS offers several desirable features. The proposed technique is completely independent of stator resistance and is less parameter sensitive, as the estimation-algorithm is only dependent on q-axis stator inductance. Also, the method requires less computational effort as the simplified expressions are used in the MRAS. The stability of the proposed system is achieved through Popov’s Hyperstability criteria. Extensive simulation results are presented to validate the proposed technique. The system is tested at different speeds including zero speed and a very satisfactory performance has been achieved.

Modelling of friction in a ball joint in mixed lubrication

This article describes a model used to predict the friction in a ball joint of a hydraulic motor operating under unique conditions. The ball joint transfers very high loads and rotates at very low speeds (including zero speed twice per motor revolution), which means that it operates in the mixed and boundary lubrication regimes. The model includes the influence of a squeeze film. It also shows the dependence of friction on the various surface qualities and is used to predict overall motor performance. The model was validated using hydraulic motors with various surface finishes on the ball joints. Measurements show that the model is a good predictor of mechanical performance and that the key variables highlighted by the model do lead to improved mechanical efficiencies.

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.

A Differential-Algebraic Approach to Speed Estimation in an Induction Motor

This note considers a differential-algebraic approach to estimating the speed of an induction motor from the measured terminal voltages and currents. In particular, it is shown that the induction motor speed /spl omega/ satisfies both a second- and a third-order polynomial equation whose coefficients depend on the stator voltages, stator currents, and their derivatives. It is shown that as long as the stator electrical frequency is nonzero, the speed is uniquely determined by these polynomials. The speed so determined is then used to stabilize a dynamic (Luenberger type) observer to obtain a smoother speed estimate. With full knowledge of the machine parameters and filtering of the sensor noise, simulations indicate that this estimator has the potential to provide low speed (including zero speed) control of an induction motor under full rated load.

Sensorless double-inverter-fed wound-rotor induction-Machine drive

The basic operation of a wound-rotor induction-motor drive fed by inverters on the stator as well as the rotor side is discussed. Different modes of operations are defined and explained based on power flow on both the sides of the machine. The sensorless motor control scheme consists of V/f-type direct frequency control on one side, with either vector control or direct torque and flux control on the other side. The machine operates up to twice the rated speed in either direction, with full flux and torque, thereby producing up to twice the rated power. Novel frequency profiles are proposed, which ensure that the frequency on either side never drops below a minimum value (set at 12 Hz in this work). Therefore, the estimation of flux can be simply and reliably carried out by integration of voltage, resulting in simple sensorless control. The drive works reliably at all speeds including zero speed and at all loads. Results from a 50-hp prototype drive are presented.

SENSOR AND INVERTER FAULT TOLERANT CONTROL IN INDUCTION MOTORS

Induction motor has increased its importance in industry over the last two decades thanks to its robustness and control performance improvement. Direct Torque Control (DTC) has been the base for multiple developments or modifications in control algorithms and models obtaining great performances against torque variations at any motor speed (including zero speed). In this paper DTC scheme has been chosen as the starting point to design a fault tolerant control for induction motors. Also, a study of the possible faults and solutions in the inverter-motor set is presented. The control algorithms used for open-switch and open-phase faults are developed and their results are presented. The supervisor and fault diagnosis system has not been included in this work though they have been taken into account during the research process.

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.

Mechanical-sensorless permanent-magnet motor drive using relative phase information of harmonic currents caused by frequency-modulated three-phase pwm carriers

This paper proposes a novel control strategy of a permanent-magnet motor drive without a rotor position sensor. The strategy is based on use of relative phase information of harmonic currents caused by frequency-modulated three-phase pulsewidth-modulation (PWM) carriers. In this system, the PWM carrier source is placed on an estimated rotor reference frame, and coordinate transformation is applied to the carrier source to generate the frequency-modulated three-phase PWM carriers on a stator reference frame. By modulating voltage references with the transformed carriers, a locus of the corresponding harmonic currents on the estimated rotor reference frame is observed as a stationary ellipse because of a rotor saliency. Since a long-diameter direction of the harmonic-current ellipse indicates a true d-axis direction, orienting the estimated d axis to the long-diameter direction makes the sensorless operation possible. The paper describes a theoretical aspect of the proposed method and, then, presents experimental results as well as computer simulation results. Consequently, not only excellent controllability over a wide speed range including zero speed has been verified, but also robustness to the motor parameter variations has been confirmed.

Sensorless drive of surface-mounted permanent-magnet motor by high-frequency signal injection based on magnetic saliency

This paper presents a new sensorless control scheme of a surface-mounted permanent-magnet (SMPM) motor using high-frequency voltage signal injection method based on the high-frequency impedance difference. In the SMPM motor, due to the flux of the permanent magnet, the stator core around the q-axis winding is saturated. This makes the magnetic saliency in the motor. This magnetic saliency has the information about the rotor position. The high-frequency voltage signal is injected into the motor in order to detect the magnetic saliency and estimate the rotor position. In this paper, the relationship between the high-frequency voltages and high-frequency currents is developed using the voltage equations at the high frequency, and the high-frequency impedance characteristics are analyzed experimentally under various conditions. The proposed sensorless control scheme makes it possible to drive the SMPM motor in the low-speed region including zero speed, even under heavy load conditions. The experimental results verify the performance of the proposed sensorless algorithm.

Control of Inverter-Fed Asynchronous Motors via Decoupling Networks

A method is presented which enables flux control of asynchronous machines in the whole speed range including zero speed. It can be set up by little technical means, does not need flux measurement and can be applied to machine feeding with impressed voltage or impressed current. The flux and the rotor frequency are controlled via a decoupling network. If the flux set value is kept constant, a linear transfer function will be obtained between rotor frequency and torque. Therefore it is possible to design speed-regulated drives providing the same steady-state and dynamic behaviour as d. c. drives. Field weakening can be done in the range beyond the nominal speed. The static and dynamic sensitivity of the flux control is analyzed due to differences between network and machine parameters. Experimental results confirm the behaviour which is expected in theory.