Sensorless Control Method Research Articles

Determination of the inductance of a synchronous reactive machine for sensorless control

The problem of eliminating rotor-position sensors in ac drives has been the focus of intense research for over two decades. Among the expected benefits of the solution to this problem are reduction of drive cost and size, as well as increased reliability. The methods developed for this purpose are usually called “methods of sensorless control.” It has been shown that sensorless-control methods for ac machines provide high efficiency at medium and high speeds. However, these methods are less efficient at lower speeds and control of the position at low and near-zero speeds is not possible. To overcome this limitation, methods of sensorless control based on the tracking the position of rotor asymmetries have been proposed. These methods measure the response of a machine to the high-frequency component of the excitation signal. One of the most attractive aspects of this method is the absence of limitations when operating at very low or near-zero speeds, which allows one to control the rotor position. This paper presents the results of theoretical and experimental studies of the method for determining inductances Ld and Lq in a synchronous reluctance machine (SynRM) using the injection of a high-frequency component into the stator voltage. This paper discusses the principles of this method and its application to the mathematical model of the SynRM and the M3AL 90LDA 4 engine produced by ABB Co. Determination of these parameters is necessary for the implementation of sensorless-motor-control systems.

A Joint Feature Position Detection-Based Sensorless Position Estimation Scheme for Switched Reluctance Motors

For a switched reluctance motor, it is important to simplify the sensorless control method in medium and high speed operation. A key solution is to detect a single feature position in a single electric cycle. Normally, the aligned position is a typical feature position, which needs to be detected. However, it is difficult to locate the aligned position with the traditional phase inductance slope zero-crossing scheme, especially when the turn-on angle is advanced. In this paper, a transformer electromotive force and motional electromotive force crossing point estimation method is presented, which is combined with the phase inductance slope zero-crossing point estimation method to estimate the aligned position. This method is capable of avoiding the error position index pulses generated at the turn-on position and the regions nearby the unaligned position. Only one position index pulse that represents the aligned position in each electric cycle can be estimated. The experimental results verify the validity of the proposed method.

A practical sensorless commutation method based on virtual neutral voltage for brushless DC motor

This paper presents a low‐cost and highly practical sensorless control method for brushless DC (BLDC) motor drives. The developed methodology can generate an accurate commutation signal for the BLDC motor by sensing the back electromotive force zero‐crossing point through the virtual neutral voltage of the motor. Since commutation control is critical for the BLDC motor control, a voltage‐controlled phase shifter comprising a hysteresis comparator and voltage‐controlled resistor is proposed in order to perform phase compensation at different speeds and prevent rapid output oscillations due to noise or high‐frequency ripples in the virtual neutral voltage. Finally, several experiments have been performed on a prototype motor to verify the theoretical analysis and demonstrate the practicality and reliability of the proposed sensorless drive method. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Digital Current Sensorless Control for Dual-Boost Half-Bridge PFC Converter With Natural Capacitor Voltage Balancing

To improve the efficiency of the conventional boost-type power factor correction (PFC) converters with the diode bridge circuit, the PFC converters of bridgeless category are often used. Due to no series-connected switches and no short-through risks, the dual-boost half-bridge (DBHB) circuit is used as the PFC converter in this paper. In order to simplify the conventional two-loop control scheme and reduce the number of sensors, the behaviors of the DBHB PFC converter are studied and its equivalent single-switch model is developed. Then, the current sensorless control for the DBHB PFC converter is proposed to achieve voltage regulation and yield sinusoidal input current in phase with the input voltage without sensing any current. In addition, the proposed method is able to balance capacitor voltages naturally without adding any voltage balancing control loop. An 800-W DBHB PFC prototype is implemented to evaluate the control performance. Both simulation and experimental results are provided to demonstrate the proposed current sensorless control method.

Position Sensorless Control of Switched Reluctance Motor Drives Based on Numerical Method

In this paper, a new position sensorless control method for switched reluctance motor drives is proposed. Rotor position is initially calculated based on the flux linkage-position–phase current characteristics by numerical method. Then, a third-order-phase-locked loop considering the acceleration variation is designed to undermine the impact of current sampling noise and numerical residual error on the estimated rotor position. A new start-up sequence is proposed. Simulation and experimental results show that the proposed position sensorless control method has achieved sufficient accuracy in terms of position and speed estimation.

PMSM Sensorless Control Based on Position Estimation Correction Using All‐Pass Filters

SUMMARYThis paper proposes a novel flux estimation method for the position sensorless control of permanent magnet synchronous motors (PMSMs). In general, the stator flux linkage for position estimation in PMSMs is obtained using the pure integration of voltages. The infinite dc gain of the pure‐integrator, however, causes numerical drifts in the obtained stator flux linkage due to the dc offset in the input of this integrator. To address this problem, a quasi‐integrator is often substituted instead of the pure integrator to restrict the dc gain, leading to another problem in which the phase characteristics vary according to the operating frequency. As a result, the ideal phase characteristics (−90° constant) cannot be held, and the position estimation performance deteriorates. Therefore, this paper proposes a phase characteristic correction method for quasi‐integrators using all‐pass filters, which achieves extremely precise estimation under transient conditions as well as in steady state.

Experimental versus EPANET Simulation of Variable Speed Driven Pumps Operation

This study points on the operation of a pumping station test rig equipped with 3 vertical centrifugal pumps, with variable speed, coupled in parallel. We investigated the pumps operation by imposing reference levels for the pumping head, then attaining the requested duty points through rotational speed control. On this test rig, the pumped flow rate is controlled by a built-in software, where the pumping scheduling algorithm relies on a sensor-less control method, based on the pump performance curve and affinity laws. The setup allows the measurement of the pumps head (displayed on rig's control panel) and rotational speed of each motor. According to the pumping schedule, when a number of n pumps are operating (where n = 2 or n = 3), then (n – 1) pumps run at nominal speed, while the remaining pump runs at a speed lower than, or equal to the nominal speed. We built in EPANET the numerical model of this test rig and calibrate the model upon experimental data, using simple control statements for the discharge valve and speed patterns for pumps. Due to the calibration, a perfect match resulted between experimental readings and numerical duty points. Further, we built an alternative numerical model, which allowed analysing additional duty points, then we plot them on a chart, together with the experimental duty points: all points fit into the operation areas attached to the pumping schedule. The proposed approach proved to be useful to study further the pumps operation, with a minimal experimental effort.

Robust Clamping Force Control of an Electro-Mechanical Brake System for Application to Commercial City Buses

This paper proposes a sensor-less robust force control method for improving the control performance of an electro-mechanical brake (EMB) which is applicable to commercial city buses. The EMB generates the accurate clamping force commanded by a driver through an independent motor control at each wheel instead of using existing mechanical components. In general, an EMB undergoes parameter variation and a backdrivability problem. For this reason, the cascade control strategy (e.g., force-position cascade control structure) is proposed and the disturbance observer is employed to enhance control robustness against model variations. Additionally, this paper proposed the clamping force estimation method for a sensor-less control, i.e., the clamping force observer (CFO). Finally, in order to confirm the performance and effectiveness of a proposed robust control method, several experiments are performed and analyzed.

Steering torque control using variable impedance models for a steer-by-wire system

This paper presents a novel sensor-less steering torque control method for applications to the steer-by-wire system. A steer-by-wire system has not any mechanical link to connect a steering wheel and a rack and pinion gear module. Instead of mechanical devices, two electric motors are used on each side. A one motor is attached to the steering wheel and the other is set on rack and pinion. The motor on the steering wheel works as a deliverer between a steering torque and load torque from the road. In this paper, we focus on motion control related to the steering feel based on impedance control. Therefore, the model of rack and pinion is not considered in this work. In most power steering systems, a torque sensor is used to set impedance effect on driver’s steering feel. In this paper, we proposed a novel steering control method without using any torque sensors. The effectiveness of a proposed method is confirmed from experimental results.

Pedaling torque sensor-less power assist control of an electric bike via model-based impedance control

This paper proposes a method to assist human force acting on electric bike without using costly torque sensors via a model-based impedance control technique. In general, electric bikes are classified into two categories, i.e., pedelec electric bikes and throttle electric bikes. We focus on the system called a pedelec electric bike. It assists human pedaling force using the pedaling information, e.g., pedaling force or speed. To obtain the human’s pedaling information in real-time, it needs physical sensors such as a torque sensor and a velocity sensor. But, these sensors are expensive and weak against external loads. Also, since these sensors are fixed directly to the forced component in a bike system, there are the risks of damage. For these reasons, sensor-less control methods based on a disturbance observer have been studied so far. In this paper, we have proposed a pedaling torque sensor-less power assist method and have applied it to the experimental pedelec electric bike. A power assist control algorithm, designed by employing an impedance model, consists of a PI-type feedback controller, an inverse model-based feedforward controller, and a pedaling torque observer. Finally, we performed experiments and confirmed the effectiveness of a proposed power assist control method.

A Study on the Stable Sensorless Control of BLDC Motor Inside Auxiliary Air Compressor

Pantograph must be correctly attached to catenary to continuously supply stable power to railway vehicle, and the device used here is Auxiliary Air Compressor (ACM). The existing ACM used the DC motor that included commutator and brush. Since maintenance and repair by mechanical friction are essential for the DC motor, BLDC motor studies have been conducted to improve this. A three-phase BLDC motor does 120° two-phase commutation through hall sensors in general. However, since hall sensor is vulnerable to heat and can run only when all three sensors work normally, sensorless control method has been studied to solve this. Using back EMF Zero Crossing Point (ZCP) detection method, this paper will introduce a stable switching sensing method that has a noncommutation area in a low speed zone.

Novel Observer Scheme of Fuzzy-MRAS Sensorless Speed Control of Induction Motor Drive

This paper presents a novel approach Fuzzy-MRAS conception for robust accurate tracking of induction motor drive operating in a high-performance drives environment. Of the different methods for sensorless control of induction motor drive the model reference adaptive system (MRAS) finds lot of attention due to its good performance. The analysis of the sensorless vector control system using MRAS is presented and the resistance parameters variations and speed observer using new Fuzzy Self-Tuning adaptive IP Controller is proposed. In fact, fuzzy logic is reminiscent of human thinking processes and natural language enabling decisions to be made based on vague information. The present approach helps to achieve a good dynamic response, disturbance rejection and low to plant parameter variations of the induction motor. In order to verify the performances of the proposed observer and control algorithms and to test behaviour of the controlled system, numerical simulation is achieved. Simulation results are presented and discussed to shown the validity and the performance of the proposed observer.

Output Characteristic Comparison of BLDC Motor for Water Circulation System According to Sensorless Control Methods

Output Characteristic Comparison of BLDC Motor for Water Circulation System According to Sensorless Control Methods

An Optimal Method for Sensorless Control of DFIG based WECS using PSO

Objectives: A sensorless method is employed to control real and reactive power for DFIG in an optimal way under various load conditions. The main objective of this paper is to maintain constant voltage and constant frequency. Method/Analysis: In this paper, a sensorless control technique with the optimal Proportional-Integral (PI) controller parameters of a test system using Particle Swarm Optimization (PSO) is explained. The techniques for the development of sensorless drives are: reduction of hardware complexity and cost, decreased maintenance requirements, elimination of sensor cables. Optimal tuning of PI controller parameters gives high quality solution. Findings: The system performance with PI controller parameters and PSO tuned PI controller parameters are compared. MATLAB software is used to develop the simulation and the results are presented. Applications: Low Voltage Ride Through, Lvrt, OFFSHORE wind farms.

Sensorless Control of Interior Permanent Magnet Synchronous Motor in Low-Speed Region Using Novel Adaptive Filter

This paper presents a novel position and speed estimation method for low-speed sensorless control of interior permanent-magnet synchronous machines (IPMSMs). The parameter design of the position and speed estimator is based on the sampled current rather than the motor electrical parameters. The proposed method not only simplifies the parameter design, it enables the estimator to work normally even in the condition that the electrical parameters are uncertain or varied. The adaptive filters are adopted to extract the desired high frequency current. The structure and corresponding transfer function are analyzed. To address the shortage of insufficient stop-band attenuation, the structure of the adaptive filter is modified to provide suitable bandwidth and stop-band attenuation simultaneously. The effectiveness of the proposed sensorless control strategy has been verified by simulations and experiments.

Pseudo-Random High-Frequency Square-Wave Voltage Injection Based Sensorless Control of IPMSM Drives for Audible Noise Reduction

High frequency (HF) signal injection is an effective sensorless control scheme for interior permanent-magnet synchronous motor (IPMSM) drives to achieve low and zero speed operation. However, the audible noise produced by the injected HF signal is often very shrill and harsh to hear, which restricts the actual application. In order to reduce the audible noise, a novel pseudo-random HF square-wave voltage injection scheme is proposed in this paper. The HF voltages with two different frequencies are randomly injected into the estimated rotor reference frame cycle by cycle, and a corresponding signal demodulation method for extracting the rotor position information is presented. Based on the principle analysis of this random frequency injection scheme, the digital time-delay effect in HF signal is considered and a compensation method for signal demodulation is proposed, which is effective in reducing position estimation error. Then, the power spectra density (PSD) in fixed frequency and pseudo-random frequency injection schemes are compared both theoretically and experimentally. The distribution of HF voltage and current PSD is extended by using the proposed injection scheme. Finally, this sensorless control method is verified by simulation and experiment on a 2.2-kW IPMSM drive platform.

Single Inverter Fed Speed Sensorless Vector Control of Parallel Connected Two Motor Drive

This paper describes a speed sensorless vector control method of the torque for cost-effective parallel-connected dual induction motor fed by a single inverter. A natural observer with load torque adaptation is employed to estimate the speeds of the same rating induction motors connected in parallel and fed by a single inverter. The speed difference between the two induction motors for unbalanced load conditions is less in natural observer than the conventional adaptive rotor flux observer. Direct field oriented control is used to calculate the rotor angle from the estimated rotor fluxes and the mean rotor flux is kept constant by rotor flux feedback control. The simulation and experimental results of studies are demonstrated for various running conditions to prove the effectiveness of the proposed method. The closed loop speed control operation with inner current control was performed by TMS320F2812 processor.

Position Sensorless Control Method at Zero-Speed Region for Permanent Magnet Synchronous Motors Using the Neutral Point Voltage of Stator Windings

A new sensorless control method that uses the neutral point voltage from stator windings is proposed. Each inductance of the three phase coils of the permanent magnet synchronous motor (PMSM) is slightly affected by the rotor magnet flux. As a result, the neutral point voltage also changes depending on the rotor position. The rotor position can be estimated by detecting the neutral point voltage even in the zero-speed regions based on this principle. In addition to this, this method can be applied to nonsaliency PMSMs. This paper presents the principle and the experimental results when using a small-capacity PMSM without saliency.

Load disturbance observer‐based control method for sensorless PMSM drive

This study proposes a sensorless control method for the permanent magnet synchronous machine (PMSM) drive that is robust against load torque variations. The proposed method is based on the disturbance observer-based control (DOBC) method, and involves the use of a back electromotive force observer and a torque observer to estimate rotor position and compensate for load torque disturbance, respectively. This mechanism is simple to implement and requires no state vector derivation. The gains of the two observers are carefully selected to improve estimation accuracy and dynamic performance. The performance of the proposed load DOBC for sensorless PMSM drives was tested through a simulation, where the sensorless estimation error was considered to determine the adjustment laws for the proposed observer gains. Furthermore, results of evaluative experiments verified the effectiveness of the proposed method for high-performance sensorless control and torque disturbance rejection for the PMSM drive.

1-kW 2000–4500 r/min Ferrite PMSM Drive: Comprehensive Characterization and Two Sensorless Control Options

An optimal design of internal Ferrite permanent-magnet motor with embedded key finite-element method verification is presented with the scope to increase the efficiency of the small power motors without using expensive rare earth permanent magnets. Two internal flux concentration topologies are analyzed, and the geometric dimensions and performances are presented for three cases, all at 1-kW rated power at 4500 r/min rated speed. The 6/8 poles ferrite-spoke permanent-magnet synchronous motor prototype was built and test results prove an efficiency larger than 88% for a large load range. Two sensorless control methods based on active flux observer are presented, with the key simulation results including acceleration, speed reversal, loading, and unloading speed responses.