Limited-angle Torque Motor Research Articles

Dynamics analysis and verification for slotted limited-angle torque motor in electromagnetic valve applications

Abstract Limited-angle torque motor (LATM) as a key component of the exhaust gas recirculation (EGR) valve, which can precisely control the position of the EGR valve, thus achieving dynamic adjust the amount of exhaust gas recirculation. This paper introduces the dynamic analysis, modelling and experimental validation of a concentrated winding axial-flux slotted LTAM with 4-poles/4-slots. Aiming at the prominent issues such as cogging torque and nonlinear torque characteristics in the operating region of slotted LATMs, analytical equations are derived based on the magnetic circuit to predict the torque-angle characteristics of LATM, covering both constant torque and linear torque regions. These equations help establish the relationship between performance and key parameters, enabling rapid design of LATM. The test results indicate that the proposed model can accurately describe the electromagnetic torque and cogging torque of the LTAM, with an error range of 5%. Utilizing the effective angle range proposed in this paper, an approximate linear relationship between the electromagnetic torque and current can be achieved, with a linear error of 6%.

Position Servo Control of Electromotive Valve Driven by Centralized Winding LATM Using a Kalman Filter Based Load Observer

The exhaust gas recirculation (EGR) valve plays an important role in improving engine fuel economy and reducing emissions. In order to improve the positioning accuracy and robustness of the EGR valve under uncertain dynamics and external disturbances, this paper proposes a positioning servo system design for an electromotive (EM) EGR valve based on the Kalman filter. Taking a novel valve driven by a central winding limited angle torque motor (LATM) as the object, we have fully considered the influence of the motor rotor position and load current, as well as the magnetic field saturation and cogging effect, improved the existing LTAM model, and derived accurate torque expression. The parameter uncertainty of the above internal model and the external stochastic disturbance were unified as “total disturbance”, and a Kalman filter-based observer was designed for disturbance estimations and real-time feed-forward compensation. Furthermore, using non-contact magnetic angle measurements to obtain accurate valve position information, a position control model with real-time response and high accuracy was established. Numerous simulated and experimental data show that in the presence of ± 25% plant model parameter fluctuations and random shock-type disturbances, the servo system scheme proposed in this paper achieves a maximum position deviation of 0.3 mm, a repeatability of positioning accuracy after disturbances of 0.01 mm, and a disturbance recovery time of not more than 250 ms. In addition, the above performance is insensitive to the duration of the disturbance, which demonstrates the strong robustness, high accuracy, and excellent dynamic response capability of the proposed design.

ANALIZE NUMERICE DE CÂMP TERMIC ÎN MOTOARE ELECTRICE REDUNDANTE

In this paper, we propose to analyze the heat transfer of a torque motor with a limited angle under special space conditions. Three-dimensional models will be used, and two current values will be considered in numerical analysis. Variants in which the boundary conditions will consider different values of the emissivity of engine surfaces will also be considered. Inside the stator and rotor subassemblies of the motor, heat transfer will be carried out by conduction and radiation between the motor and the ambient environment. Using numerical analysis, it will be possible to determine the time during which the temperature in the winding reaches the maximum allowable value for the limited angle torque motor under the mentioned conditions.

Design and Implementation of a Linear Active Disturbance Rejection Control-Based Position Servo Control System of an Electromotive Valve for Exhaust Gas Recirculation.

An exhaust gas recirculation (EGR) valve is used to quickly and dynamically adjust the amount of recirculated exhaust gas, which is critical for improving engine fuel economy and reducing emissions. To address problems relating to the precise positioning of an electromotive (EM) valve under slowly varying plant dynamics and uncertain disturbances, we propose a servo control system design based on linear active disturbance rejection control (LADRC) for the EGR EM valve driven by a limited angle torque motor (LATM). By analyzing the structure of the LATM and the transmission, the dynamic model of the system is derived. In addition, to solve the problems caused by slowly varying plant dynamics and uncertain disturbances, we combine the effects of uncertain model parameters and external disturbances as the total disturbance, which is estimated in real time by an extended state observer (ESO) and then compensated. In addition, accurate angular information is obtained using a non-contact magnetic angle measurement method, and a high-speed digital communication channel is established to help implement a closed-loop position control system with improved responsiveness and accuracy. Simulation and experimental results show that the proposed servo system design can effectively ensure the precision and real-time performance of the EM valve under slowly changing plant dynamics and uncertain disturbances. The proposed servo system design achieves a full-stroke valve control accuracy of better than 0.05 mm and a full-stroke response time of less than 100 ms. The controlled valve also has good robustness under shock-type external disturbances and excellent airflow control capability. The repeatability of the airflow control is generally within 5%, and the standard deviation is less than 0.2 m3/h.

Intracycle Active Blade Pitch Control for Cross-Flow Tidal Turbines Using Embedded Electric Drive Systems

Cross-flow tidal turbines (CFTTs) have proven advantages over horizontal axis turbines in terms of high power density per unit area, simplicity of design, and operation independence from inflow direction. However, they suffer from an unsteady flow regime which can comprise dynamic blade stall and thus problems of material fatigue or even failure. Active pitch control mechanisms on blade level have been shown to provide a potential solution, when continuously adjusting the pitching angle of each individual blade during the whole rotational cycle of the turbine.
 As part of the research of the OPTIDE project, in this study, electric drive systems embedded in the blades of a CFTT flume model are proposed aiming to realize an active pitch control with high efficiency and fast response. The blade embedded actuation allows for reasonable flow conditions. For full scaled on-site applications this is required to reduce hydrodynamic losses and to protect the actuators and electronics from the harsh environmental and operation conditions. Based on the expected hydrodynamic loads from numerical flow simulations (CFD), several types of actuators are considered. The first type has brushless DC motors installed at both sides of each blade. Along with a gear box with proper reduction ratio, the actuators are able to provide required torque within expected cycle period. The second type of actuator drives the blade directly, which always results in faster pitching action, higher drive efficiency, more accurate positioning of blades, as well as simpler structure. Specifically, the shaft of each blade is designed as the primary of a limited angle torque motor, while the blades are used as the secondary with magnets inside. To mitigate the potential saturation effect on the iron of the primary­, the blade can also be used as the primary, where there always exists much larger space for windings. In this case, the magnets are now located at the shaft. By doing this, it is expected to output larger torque in a wider range of pitching angle as compared with the original one, while almost the same power is required. An experimental test bench for a single blade with both types of actuators is built to verify their ability of a fast and accurate pitching control. This also lays the foundation of identifying the optimal pitching angle for the control and inhibition of dynamic blade stall at various flow conditions and blade positions within the rotational cycle of the turbines. After successful optimization and testing of the model scaled mechatronical design, the actuators will be up scaled for realistic applications.

Analysis of an Axial-Flux Slotted Limited-Angle Torque Motor with Quasi-Halbach Array for Torque Performance Improvement

Better torque performance and higher reliability have long been the focus of research for slotted limited-angle torque motors (LATMs), which are primarily used to position first-stage valves in electrohydraulic servosystems. This paper presents a high reliability axial-flux slotted LATM with quasi-Halbach array for torque performance improvement including constant torque range (CTR) and output torque. Firstly, the structure with two sets of windings and the operation principle of the proposed slotted LATM is analyzed. Secondly, a brief design procedure is presented, the structure selections of open slot and double-stator single-rotor (DSSR) interior rotor with surface mounted quasi-Halbach permanent magnet (PM) array are illustrated, and the geometric parameters are optimized to obtain the optimal design of the proposed slotted LATM. Then, 3-D finite-element method (FEM) is employed to compare the proposed slotted LATM with the conventional surface mounted PM slotted LATM in terms of cogging torque, no-load back EMF, and output torque, and the results show that the proposed LATM with quasi-Halbach array has a 10% improvement in output torque and a 25% improvement in CTR. Meanwhile, the flux linkages and torque performance of the two sets of windings under various conditions verify good magnetic isolation. Finally, prototypes of two different rotor types are manufactured and a series of experiments are performed to validate the analysis.

ELECTROMAGNETIC AND THERMAL FIELD STUDIES IN REDUNDANT ELECTRIC MOTORS

This paper proposes the electromagnetic and thermal analysis for a two-channel limited-angle torque motor using three-dimensional numerical models. The two-channel limited-angle torque motor that we present in the paper, unlike the classic torque motor, provides the role of two limited-angle torque motors. It represents a solution for applications where high functional performance, overall dimensions, weight and operational safety are critical. Numerical analysis will be used in the design in order to establish an optimal constructive solution from the point of view of all the engine requirements established in the Technical Specification

Comparison of control strategies for hysteresis attenuation in electromechanical actuators subject to dispersion

This paper addresses the difficulties of designing highly efficient robust controllers for a class of systems exhibiting high hysteresis with parameters dispersion that limits control accuracy and performance homogeneity over the parametric uncertainties range. Two control strategies to solve the problem are assessed. First, a Reference Model Sliding Mode Control (RMSMC) feedback controller known to be robust to parametric uncertainty is designed to compensate hysteresis, regardless of the hysteresis quantity. Secondly, a strategy based on a feedforward controller with a Neural Network inverse model and a PID feedback controller is proposed. In this case, hysteresis dispersion is addressed through the integration of a backlash estimator for computing the Neural Network inverse model. The control strategies are implemented for position control of a Limited-Angle Torque Motor (LATM) exhibiting uncertain hysteresis. Experimental tests demonstrated the very good accuracy and robustness of the Neural Network inverse model and the PID controller for position tracking when the LATM is subject to dispersion and the benefits of the Reference Model Sliding Mode Control (RMSMC) feedback controller for the rejection of external disturbances.

Integrated Physical Modeling and Optimal Control Method of Limited-Angle Torque Motor in Fuel Metering Apparatus

Limited-angle torque motor (LATM) is a critical component to precisely drive the valve angle of an engine’s fuel metering apparatus and accurately measure the fuel flow, and research on it is of great significance. Thus, the LATM of a certain kind is regarded as the research object in this paper. Firstly, a Simscape-based LATM integrated physical modeling method is proposed, which can better demonstrate the real operational characteristics of a motor, compared with the current mathematical model. Secondly, a Proportional-Integral-Derivative (PID) parameter self-tuning method based on a constriction factor particle swarm optimization (CPSO) algorithm is broached since it is difficult to tune due to a large number of multi-loop cascade PID control parameters. Simulation and experimental results showed that the control performance increases by 40% in the triple closed-loop PID control system with a stronger disturbance rejection, simpler design, and quickly responds when compared with the previous empirical tuning method. The triple closed-loop PID control system comprises an angle loop + angle velocity loop + current loop and technically supports the engineering application design of motors.

토크 밀도 향상을 위한 제한된 각도 토크 모터의 하이브리드 구조

The limited angle torque motor (LATM) is an electromagnetic actuator that rotates within a limited angle of less than ±90°. In this study, the advantages of permanent magnet (PM) type and reluctance type LATM are combined to create a hybrid LATM with high torque density for the same volume. The proposed hybrid LATM structure combines structural advantages using a PM with a high magnetic flux density of a PM type LATM and voice coil winding with a high fill factor of reluctance type, as well as making a prototype and conducting a torque test.

Operational range extension method for limited‐angle torque motors with irregular slot numbers

A modified model of a limited-angle torque motor (LATM) with irregular slot numbers is proposed for developing an operational range extension method for LATMs. The modified model is derived by considering the effects of the asymmetrical winding structure and magnetic flux leakage, which are validated by finite element analysis and experimental measurements. Based on the modified model, accuracy and time consumption of the simulation can be improved. For the operational range extension method, extended angle range selection theory and constraint conditions are proposed, and the relationship between the sinusoidal tracking characteristic and leading parameters is established by theoretical analysis. A simulation and a prototype machine experiment on an LATM using the new method are carried out. The results show that the proposed operational range extension method can reduce the weight and volume of the LATM without changing sinusoidal tracking characteristics, which proves the feasibility of applying the new method in the oscillating scan system to realize lightness and miniaturisation of the system.

STUDII DE TRANSFER DE CĂLDURĂ ÎN MAȘINI ELECTRICE UTILIZATE ÎN CONDIȚII DE FUNCȚIONARE SPECIALE

"This paper aims to analyze the heat transfer of a DC limited angle torque motor, in special conditions, of space. Three-dimensional models will be used and two current values will be considered. As a working hypothesis, several variants will be numerically analyzed in which the boundary conditions will take into account different values of the emissivity of the motor surfaces varying in the range 0.2 ÷ 1. Inside the motor subassemblies the heat transfer will be done by conduction and between the motor and the environment by radiation. Using thermal modeling, it will be possible to determine the time in which the winding temperature reaches the maximum value allowed for the DC limited angle torque motor, in space conditions. The approached motor presents specific technical aspects (constructive and functional) and novelty in the field of torque motors with limited angle. These types of motors are recommended for applications where both volume and weight are critical requirements. The applications of DC-LATM are diverse: in the fields of aerospace, military technique, medical etc. For special applications (eg aerospace) a redundant motor solution is required [7]. The motor is designed for applications that require rotation over a certain angular range, (the working domain of this motor is 45 ÷ 135°). The space industry is a field of maximum interest from a scientific, economic and strategic point of view. Compared to other fields, its growth in recent years is extraordinary, as evidenced by the availability of telecommunications services. The requirements of the motor given by the application in which it is used including the environmental conditions in which the motor operates will determine the input data of the heat transfer problem. There are two categories of requirements that are equally important: general (mechanical, thermal, electrical) and environmental (stability to vacuum and radiation, resistance to AO - atomic oxygen) etc. Also, several aspects must be considered, such as: environmental effects (LEO - Low Earth Orbit or GEO - Geostationary Orbit), constraints applicable to materials (temperature, vacuum, thermal cycles, chemical - corrosion, galvanic compatibility, atomic oxygen , moisture absorption / desorption, fluid compatibility), if materials will degrade over time, the system in which the product will be integrated, interfaces [8]. The heat transfer analysis addressed in this paper establishes the DC-LATM behavior from a thermal point of view in space conditions."

Modeling and Analysis of Limited-Angle Torque Motor Considering Nonlinear Effects

Nonlinear mathematical model (NMM) of limited-angle torque motor (LATM) is rarely studied at present because its operating principle is different from conventional rotating electrical machines. In this article, inspired by the NMM of rotating electrical machines, a high-fidelity and computationally efficient model of LATM is proposed, which can completely consider the nonlinear effects, including the electromagnetic torque, flux linkage, and inductance variation with current and rotor position due to magnetic saturation in the stator core. Different from the field-circuit coupling approach (FCCA) considering nonlinear effects, the proposed model exhibits higher computational efficiency since a finite element analysis (FEA) is not involved in the time-stepping simulation. Based on the high-fidelity model, an LATM position-tracking system model is built to simulate the real operation of the LATM system, which provides an accurate means of assessing the position-tracking performance without the actual test platform. The high fidelity of the proposed LATM model is validated by both the FCCA and experimental results.

Nonlinear EMC Modeling and Analysis of Permanent-Magnet Slotted Limited-Angle Torque Motor

In this article, a high-precision equivalent magnetic circuit (EMC) model is first proposed for slotted permanent-magnet (PM) limited-angle torque motor (LATM) with nonuniform teeth, which leads to potential application in swing system substituting a lower torque density of the slotless structure. By the proposed relatively fine division method of magnetic reluctance in the stator tooth-tip segments, air-gap regions, and PM poles, the proposed EMC model can fully consider armature reaction and magnetic saturation problem. Subsequently, a multiobjective optimization method based on the EMC model is proposed to improve torque performance. Finite-element analysis is employed to validate the EMC model and optimization results. Following that, a curved nonwounded tooth shape is carried out and further optimized to decrease magnetic saturation of stator teeth and significantly improve symmetry of torque profile about stable equilibrium point, compared with the traditional straight tooth shape. Finally, the slotted LATM with curved teeth is prototyped, and its experimental results are presented and discussed. The simulation and experimental data show better accuracy of torque profile improvement.

Analytical Study, Design and Optimization of Radial-Flux PM Limited-Angle Torque Motors

This paper presents an analytical study of the radial-flux slotless limited-angle torque motors. The modelling is based on the magnetic equivalent circuit of the actuators and uses the electromagnetic equations to calculate the air-gap flux as well as the produced torque. This model is then used for designing the actuators both in outer-rotor and inner-rotor structures, considering the design constraints and desired characteristics. As the objectives in design stage usually conflict with each other, an intelligent multi-objective optimization algorithm is required to design the best fit actuators. Analytical and simulation results are presented and compared to show the accuracy of the model and verify the design equations as well as the design approach. As this type of actuators is a key element in industrial control, the contributions of this paper are focused on new analytical field solution based on magnetic equivalent circuit, design and optimization approach for radial-flux structure and introducing a general procedure that could be extended to similar structures and actuators.

Torque Performance Improvement for Slotted Limited-Angle Torque Motors by Combined SMA Application and GA Optimization

Due to stator magnetic saturation and inherent cogging torque, the slotted limited angle torque motor (LATM) performs large torque ripple within its operation range, resulting in vibration noise and complex control problem. The novelty of this article is to not only first to apply 1J22 soft magnetic alloy (SMA) in the LATM but also to propose a multiobjective optimization method to improve the torque performances including torque ripple, cogging torque, and output torque, based on genetic algorithm (GA). First, 1J22 SMA is applied to the LATM to reduce the torque ripple caused by magnetic field saturation. Then, through the sensitivity analysis, weight coefficients of the related parameters of stator tooth for the optimization process are obtained. Besides, in order to optimize torque performances, the multiobjective optimization process is carried out and the GA is used to obtain the desired objective. Finally, the finite-element analysis (FEA) is used to validate the optimization design.

Research on Torque Ripple Suppression of the Slotted Limited Angle Torque Motor

This article presents the theoretical analysis and numerical modeling of various cogging torque suppression methods of the slotted limited angle torque motor (LATM). The relationship between the cogging torque, the output characteristics, and the structure parameters of new methods is revealed by derived equations and finite-element analysis (FEA), which provides a theoretical basis for the optimization of the slotted LATM. The effectiveness of the best suppression method is verified by the prototype experiment. In addition, a method to predict torque distortion caused by armature reaction is proposed and it is verified by the finite-element simulation and prototype experiment.

Analysis, Modeling, and Verification of Limited Angle Torque Motors With Irregular Slot Numbers for Performance Improvement

This article presents the theoretical analysis, numerical modeling and experimental verification of a novel limited angle torque motor (LATM) with an irregular slot number. Based on the magnetic circuit, analytical equations are derived for predicting the torque-angle characteristic of the LATM, including both the constant torque region and linear region. By these equations, the relationship between the performance and leading parameters is established, providing a reference for the quick design of LATM. The idea of utilizing the linear region to expand the angular operation range of LATM is then proposed. It is shown that by active control of the winding current, the linear region can be reasonably used. Due to larger cogging torque in the integral-slot LATM, an irregular slot number topology is proposed to suppress the cogging torque. The results are validated by finite element analysis, and further verified by experimental measurements on a prototype machine.

Hysteresis Dispersion Compensation with Neural Network based Controller

Hysteresis is a commonly encountered physical phenomenon in many systems. It results in a dependence of the state of a system to its history. This non-linearity makes it particularly difficult to control accurately. There are many ways for compensating hysteresis, one of them consists of building an inverse model of the hysteresis and using it as a feedforward controller. Coupled to a feedback mechanism, the hysteresis impact can thus be minimized. However, the performance of these controllers decreases when exposed to dispersion in the hysteresis quantity or shape. The capacity of neural networks to model non-linear phenomena is not to be proven and will be put at use. In this paper, an artificial neural network model was trained to replace the conventional hysteresis inverse model. The controller performance was evaluated on a limited-angle torque motor, which exhibits hysteresis due to the magnetization saturation of the ferromagnetic materials. The experimental results pointed out the superior robustness to system dispersion of the Neural Network based controller for time and frequency response.

Development of a Radial-Flux Slotted Limited-Angle Torque Motor With Asymmetrical Teeth for Torque Performance Improvement

Although conventional slotted limited-angle torque motors (LATMs) have a high torque density, its fatal shortcoming of non-uniform torque profile makes it difficult to apply for precise positioning systems. This paper presents a novel radial-flux slotted LATM with asymmetrical teeth for the torque performance improvement including average output torque and angular operation range. A magnetic equivalent circuit (MEC) for radial-flux slotted LATMs is first derived and implemented in the design process. Then, the finite-element analysis is utilized to validate the related analytical equations and to make the comparison of the torque performance between the radial-flux conventional and proposed LATMs. Finally, a prototype machine of the proposed LATM is accomplished, and its torque characteristic experiment is carried out to confirm the torque performance improvement. The related experimental results are presented and discussed.