Permanent-magnet Motor Servo Research Articles

High-temperature magnetic performance and corrosion resistance of hot-deformed and sintered Nd-Fe-B magnets with similar room-temperature magnetic properties

Both hot-deformed (HD) and sintered Nd-Fe-B magnet have huge prospect in the application of permanent magnet servomotor, but its magnetic performance is often influenced by increased working temperature and corrosion environment. Hereby, the high-temperature magnetic performance and corrosion resistance of HD magnets and sintered magnets with similar room-temperature magnetic properties were investigated. The melt-spun Nd-Fe-B powders of MQU-F and MQU-G have been used to prepare the HD magnets without (HDF) and with (HDG) heavy rare earth of Dy element. The sintered magnets of 45H grade (S45H) and 35UH grade (S35UH) were used as reference magnets to evaluate the high-temperature magnetic performance and corrosion resistance of HDF and HDG, respectively. The results show that both HDF and HDG have superior temperature coefficient of coercivity (β), irreversible flux loss (hirr) and corrosion resistance to the same-grade sintered magnets. The analysis on microstructure and element composition reveals that the difference in β and hirr between HD and sintered magnets is mainly resulted from grain size and Pr content. The nanograins in HD magnets are much smaller than the micrograins in sintered magnets. Consequently, |β| and hirr reduces significantly with the decrease of grain size. Meanwhile, the Pr-contained sintered magnets of S45H and S35UH consist of both Pr2Fe14B and Nd2Fe14B phases. As the magneto-crystalline anisotropy of Pr2Fe14B decreases faster than that of Nd2Fe14B with the increased temperature. |β| and hirr of the HDF and HDG are better than those of the same-grade sintered magnets. In addition, the difference in corrosion resistance is primarily caused by the grain boundary (GB) width, the total rare earth (TRE) content and Co content. The corrosion on Nd-Fe-B magnet initiates from and propagates along GB and the boundary of flake particles at the surface of HD and sintered magnets. The narrower GB width, lower TRE content and higher Dy content all play important role in better corrosion resistance of HD magnets.

Design and Optimization of PMSM for Injection Molding Machine

With the implementation of the “dual carbon policy”, the traditional injection molding machine transmission system pays more and more attention to improving the energy efficiency for the drive motor, and the PM motor has obvious advantages in injection molding machine drive motor because of its high efficiency and high-power density. A permanent magnet servo motor (PMSM) for an injection molding machine with a rated power of 7 kW is designed based on the theory of PMSM in this paper. The 2D finite element analysis (FEA) model of the motor is set up. The electromagnetic performance parameters are obtained, including cogging torque, torque ripple, output torque, and no-load back EMF. The cogging torque of the motor is optimized and analyzed. The results show that the optimized motor has reduced the cogging torque and torque ripple without affecting the output capacity, which is more suitable for the application in the drive system of the injection molding machine.

Design of High-Dynamic PMSM Servo Drive Using Nonlinear Predictive Controller with Harmonic Disturbance Observer

The high-dynamic permanent magnet (PM) motor servo system with high-bandwidth is the core equipment for industrial production, and the control bandwidth is also an important indexes to evaluate the performance of the servo system. The non-cascaded direct predictive speed control is an appropriate scheme to optimize the dynamic performance of the PM motor servo system. However, the high bandwidth of the non-cascaded control structure results in poor anti-interference ability, and it cannot effectively deal with the coupling relationship between current and speed, leading to poor control performance in the current limit region. Regarding the above problems, a nonlinear predictive speed control strategy combined with harmonic disturbance observer is proposed. In the proposed strategy, the disturbances of the servo system are separated from the mathematical model according to the nonlinear modeling theory, and the traditional disturbance observer is modified to estimate the harmonics. A nonlinear control law with strong disturbance suppression ability was designed. Furthermore, a complete current and speed prediction mechanism was introduced into the algorithm, in which the proportional differential (PD) controller is employed as the connection medium between the reference current and speed to solve the coupling problem of the non-cascaded control structure.

Analysis and comparison of performance of permanent magnet servo motors after stator shifting combination

Analysis and comparison of performance of permanent magnet servo motors after stator shifting combination

Analysis of permanent magnet servo motor performance with different semi-ferromagnetic sleeve materials

Proposed is a study on the application of a semi-ferromagnetic sleeve in a permanent magnet servo motor (PMSM). First, taking the no-load electromotive force as the research object, the optimal sleeve permeability of the PMSM was determined using the finite element method, and the correctness was verified using an analytical algorithm. In the analytical calculation process, to solve the calculation problem of the no-load leakage flux coefficient caused by the complex distribution of the pole-to-pole leakage flux, an iterative calculation method is proposed. Second, based on the optimization sleeve permeability, the variation of the eddy current loss with different sleeve conductivity was analyzed, and the optimal conductivity value was determined. Finally, variations in current and power factor before and after optimization were compared and analyzed, and the effect of the sleeve electromagnetic characteristics on the motor performance was analyzed. Motor performance after optimization could be consistent with that of before optimization by reducing the thickness of the permanent magnet, which provides a theoretical basis for the optimization analysis of energy and material savings of the PMSM.

Self-Sensing via Flux Injection With Rapid Servo Dynamics Including a Smooth Transition to Back-EMF Tracking Self-Sensing

Self-sensing control at zero and low speed has been widely implemented and studied by many researchers. This technique is based on injecting a high-frequency voltage or current into the motor to estimate the motor position and speed from the measured motor quantities like current or voltage. Tracking the motor back-EMF or flux signal has been used to control motors during medium- and high-speed operations. This article proposes a high-frequency flux injection (HFFI) based self-sensing using deadbeat-direct torque and flux control to control permanent magnet servo motor at zero and low speed with ideally zero torque ripple, unlike the standard current or voltage injection techniques. The HFFI is combined with a back EMF self-sensing technique to control the motor during medium- and high-speed operations. This article also proposes a method for a smooth transition between these two methods. The proposed controller is used to control different types of slightly salient servo motors during dynamic servo operations.

Dynamic Loss Minimizing Control of a Permanent Magnet Servomotor Operating Even at the Voltage Limit When Using Deadbeat-Direct Torque and Flux Control

Energy consumption and efficiency of electrical drives is becoming an increasingly important issue. This encourages many researchers to develop new control techniques to reduce the energy consumption in electrical drives. Some of those techniques are more effective than others; some of them can save energy but will affect the response of the drive. Deadbeat-direct torque and flux control has the fastest possible response, allowing direct and independent control of the actual motor states. Using this controller, it is possible to select the optimum stator flux linkage in each switching period to minimize the motor losses dynamically. Many algorithms were derived for motors that are not operating at the voltage limit. This paper will present an algorithm that can be used to minimize motor losses without affecting electrical drive performance. The proposed algorithm works even at the voltage limit during flux weakening operation, it is also easy to implement, doesn't require any lookup tables that require significant effort to obtain, can be applied to any kind of permanent magnet motors, and is feasible in real time for different operating conditions.

Research on the Mechanism of Demagnetization Limitation in Permanent Magnet Servo Motors

Background: Demagnetization limitation of permanent magnets is the maximum demagnetization rate, and it is not only influenced by motor overload capacity, but also influenced by winding limit temperature and permanent magnet limit temperature. It has important significance to study the influence of demagnetization limitation on motor whole life cycle management. Methods: In this paper, the finite element method, the analytical algorithm and the equivalent thermal network method were adopted. Aiming at the mechanism research on the demagnetization limitation of permanent magnet servo motors (PMSM), the demagnetization factor is proposed, which can reflect the relationship between the demagnetization and electromagnetic performance of PMSMs, and it can also indicate the influence of overload capacity on demagnetization limitation. Based on the calculation of motor losses, the temperature variation of the motor was studied in depth. Considering the temperature rise caused by heat accumulation effect, the demagnetization limitation of permanent magnets was obtained. Combined with the constraint of the winding insulation grade and limit temperature of permanent magnets on demagnetization limitation, the optimal combination of armature windings and permanent magnets was determined. Results: The accuracy of calculation results was verified by experiment to prove the correctness of the research on demagnetization limitation. Conclusion: The research on motor demagnetization can provide some useful reference for motor design and maintenance. Keywords: Demagnetization limitation, finite element method, harmonic current, heat source, permanent magnet servo motor, temperature field.

Research on Magnetic Pole-Shifting Equivalent Model of Interior Permanent Magnet Synchronous Servo Motor

It is difficult to calculate the offset angle of the built-in magnetic pole in the high-speed servo motor. This paper presents a cogging torque equivalent model (CTEM) of the interior permanent magnet servo motor (IPMSM). Taking the 4-pole and 24-slot IPMSM as an example, the equivalent model implementation steps from the IPMSM to the CTEM has been introduced firstly, then the optimization method of the interior pole-shifting angle and the finite element analysis are executed to verify the equivalent model. The results show that the cogging torque of the IPMSM can be reduced by 90.1% according to the optimized equivalent angle of the CTEM, which verifies the rationality and validity of the CTEM.

Optimization and Calculation of Equivalent Thermal Network Method in the Temperature Field Research of Permanent Magnet Servo Motor

Optimization and Calculation of Equivalent Thermal Network Method in the Temperature Field Research of Permanent Magnet Servo Motor

Current Command Compensation for PM Servo Motor Considering Voltage Saturation Caused by Both Rapid Change in the Current Command and High‐Speed Rotation

SUMMARYThis paper proposes a new antiwindup method for PM (permanent magnet) servo motor control that compensates for the current commands based on both the amount of transient voltage saturation at high acceleration calculated from the proportional current control model and the amount of voltage saturation in the PI current controller at high speeds. Experimental results show that our proposed method can suppress the windup phenomenon and maintain stability under voltage saturation caused by high speed, high response, high acceleration, and severe voltage sag. Thus, the proposed method can improve the productivity of industrial machines, and is especially effective for PM servo motor control that has a large inductance, such as DDM (direct‐drive motors) and IPM (interior permanent magnet) motors.

Effective Torque Ripple Compensation in Feed Drive Systems Based on the Adaptive Sliding-Mode Controller

Rotary or linear permanent magnet servo motor systems are widely used in mechatronics applications. When used in direct-drive configuration without any mechanical transmission, one of the bottlenecks in achieving precision positioning is the rejection of torque ripples, which are in the form of high-frequency harmonic disturbances varying with the operating condition of the servos. When attached to mechanical transmission, ripple disturbances occur due to misalignments, repetitive contact, or the process forces itself. In this paper, a robust adaptive sliding-mode control is proposed to reject harmonic disturbances in servo systems and attain accurate positioning. The overall sliding-mode control law is derived from the Lyapunov function without the switching condition allowing convenient implementation in a PID-like form. Effectiveness of the controller is demonstrated experimentally, where the ripple forces that occur due to mechanical contact in spur and worm-gear feed drive servo systems are compensated successfully.

Model and Conditional PID Compensation Control on Flow of Hydraulic Source Driven by Permanent Magnet Servo Motor

In view of the existed defects of hydraulic source driven by variable frequency induction motor in practical applications, such as slow response, low control accuracy and difficult to master control parameters, a flow control strategy of permanent magnet servo motor driven constant pump hydraulic power unit is presented. This strategy mixes merits of permanent magnet servo motor, such as good dynamic characteristics, high control precision, and saving energy, and characteristics of constant pump, such as simple structure, good reliability and strong ability to fight pollution, etc. According to the relationship between speed, flow and pressure of constant pump, and oil temperature, viscosity, elastic modulus and other related parameters, model and conditional compensation proportion, integration, differentiation(PID) control on motor speed is proposed, through which the rapidity and accuracy of control on the output flow of constant pump are realized easily. The control system makes full use of the stability and timeliness of the open-loop model control to approaching target flow, overcoming the adverse effect that the measured flow signal delay brings serious hysteresis influence on system response in the traditional flow control system. In addition, the conditional PID compensation control, through the comparison with the conditional threshold value to open, can further eliminate flow deviation and improve the precision of the system. Simulation results show that the feasibility of the model control and the conditional PID compensation control. Experimental results show that the response of model control is close to motor speed open-loop control, which is better than indirect measurement flow feedback control, and significantly ahead of the turbine flowmeters measured flow feedback control. The control system has good resistance to load disturbance ability; the conditional PID compensation control can completely eliminate the steady-state error caused by the system parameter nonlinear change and simplified model, and can follow target flow at slope response without error.

Real-time thermal management of permanent magnet synchronous motors by resistance estimation

Real-time thermal management of electrical machines relies on sufficiently accurate indicators of internal temperature. One indicator of temperature in a permanent-magnet synchronous motor is the stator winding resistance. This study applies two current injection techniques to a commercially produced permanent-magnet servomotor, which are applicable under load and cause minimal disturbance to the shaft torque. The current injection techniques applied here enable the temporary boosting of resistive voltage and consequent application to low-resistance, high-voltage machines. The effectiveness of the approach is demonstrated by tracking the change in winding temperature during a 2 h load cycle.

Method for on‐line estimation of electrical motor parameter variation and current sensor offset for SPM motor

AbstractThe servo system of a permanent magnet (PM) motor should always maintain fine torque and speed responses. Accurate motor parameter identification is necessary for the PM motor servo system because the current control system is designed by considering the electrical parameters of the PM motor. However, the motor parameters vary with the age of the motor and the temperature. Moreover, the current sensors have offset values. When the current sensor has offset values, the PM motor servo system produces torque ripple. In order to overcome these problems, this paper proposes a new real‐time estimation method for both the current sensor offsets and the electrical parameters (resistance Ra , inductance La , and magnetic flux ϕfa) of the surface permanent magnet (SPM) motor. The proposed method involves the use of a real‐time algorithm and a current simulator, which is operated using a DSP software system. In order to accurately estimate the motor parameters, the proposed method uses estimated currents, the DC components of sensor currents, and the nominal motor parameter values. The experimental results confirm that the proposed method satisfactorily estimates the current sensor offset of the U phase and V phase, as well as the electrical motor parameters Ra,La , and ϕfa accurately. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 182(2): 30–41, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22331

Fuzzy Sliding Mode Control with Eigenvalue Assignment for Electrical Servo System

Fuzzy sliding mode control with robust eigenvalue assignment technique is proposed for electrical servo system. A smooth function is used for the switching device to alleviate the chattering problem caused by sliding mode control, and an auxiliary compensator is employed to find the sliding condition for an ideal system and specify the dynamic characteristics of the sliding variable directly. It makes the system can not only achieve very good tracking performance, but also obtain good robustness. Simulation studies with a permanent magnet servomotor further illustrate the feasibility and effectiveness of the proposed scheme.

Method for On-line Estimation of Electrical Motor Parameter Variation and Current Sensor Offset for SPM Motor

The servo system of a permanent magnet (PM) motor should always maintain fine torque and fine speed responses. Accurate motor parameter identification is necessary for the PM motor servo system because the current control system is designed by considering the electric parameters of the PM motor. However, the motor parameters vary with the age of the motor and temperature. Moreover, current sensors have offset values. When the current sensor has offset values, the PM motor servo system produces torque ripple. In order to overcome these problems, this paper proposes a new real-time estimation method for both current sensor offsets and electrical parameters (resistance Ra, inductance La, and magnetic flux φfa) of the surface permanent magnet (SPM) motor. The proposed method involves the use of a real-time algorithm and a current simulator, which is operated using a DSP software system. In order to accurately estimate the motor parametera, the proposed method is using estimate currents, DC terms of sensor currents, and nominal motor parameter value. The experimental results of this study confirm that the proposed method satisfactorily estimates the current sensor offset of the U phase and V phase, as well as the electrical motor parametersRa, La, and φfa accurately.

Staged modelling A methodology for developing real‐life electrical systems applied to the transient behaviour of a permanent magnet servo motor

This paper presents a methodology to achieve a global dynamic model of an electrical system that consists of a battery, an inverter, a permanent magnet servo motor and a turbine. The stress is placed on the fact that a classical finite element model would not be able to provide a satisfactory representation of the transient behaviour of the whole system. A staged modelling is proposed instead, which succeeds in providing a complete picture of the system and relies on numerous finite element computations.

Integrated micro- and miniscale electromechanical systems with permanent-magnet servo-motors and VLSI drivers–controllers

The current trends in development and deployment of advanced micro- and miniscale electromechanical systems (MEMS) have facilitated the unified fundamental, applied, and experimental research activities in the analysis and design of state-of-the-art motion devices (rotational and translational electromechanical motion devices), integrated circuits (ICs), and controllers. The objectives of this paper are to design, develop, and compare different control algorithms for high-performance MEMS with permanent-magnet rotational servo-motors controlled by ICs (VLSI driver–controller is fabricated using CMOS technology). The problems to be solved are very challenging because a number of long-standing issues in design, hardware integration, control, nonlinear analysis, and robustness have to be solved. The major emphases of this paper are the analysis and design of robust servo-systems, as well as the comparison of the dynamic performance of closed-loop MEMS with different control algorithms. We synthesize, verify, and test proportional–integral, integral with state feedback extension, relay, and sliding mode controllers. It is illustrated that the sliding mode control laws drive the states and tracking error to the switching surface and maintain (keep) the states and tracking error within this nonlinear switching surface in spite of different references, disturbances, parameter variations, and uncertainties. That is, robust tracking, desired accuracy, and disturbance attenuation are achieved. We report the experimental setup which was built to perform the advanced studies of high-performance MEMS. The testbed was built to integrate permanent-magnet microscale servo-motor and ICs (driver–controller).

ADAPTIVE TORQUE PULSATION COMPENSATION FOR A HIGH-TORQUE DC BRUSHLESS PERMANENT MAGNET MOTOR

Brushless permanent magnet (PM) servomotors are appealing candidates for many high-performance applications. A persistent problem with PM motors is the non-uniformity in the developed torque which gives rise to a torque pulsation that varies as a function of operating conditions. In this paper an adaptive torque pulsation compensation scheme is developed. The adaptive scheme is based on a simple lumped parameter model for the motor and on the prescribed and actual angular position measurements. The compensating signal is directly added to the motor's position control signal, so that no new hardware is necessary. The adaptive scheme is implemented on a PC computer and the effectiveness of the adaptive torque pulsation compensation is demonstrated by experiments.