PMSM Torque Research Articles

Mechanism and Characteristics of Cogging Torque in Surface-Mounted PMSM: A General Airgap Field Modulation Theory Approach

Mechanism and Characteristics of Cogging Torque in Surface-Mounted PMSM: A General Airgap Field Modulation Theory Approach

Robustness-Oriented Design Optimization Approach for Cogging Torque of Batch Production PMSM

Robustness-Oriented Design Optimization Approach for Cogging Torque of Batch Production PMSM

PMSM Torque Ripple Suppression Method Based on SMA-Optimized ILC

Periodic torque ripple often occurs in permanent magnet synchronous motors due to cogging torque and flux harmonic distortion, leading to motor speed fluctuations and further causing mechanical vibration and noise, which seriously affects the performance of the motor vector control system. In response to the above problems, a PMSM torque ripple suppression method based on SMA-optimized ILC is proposed, which does not rely on prior knowledge of the system and motor parameters. That is, an SMA is used to determine the optimal values of the key parameters of the ILC in the target motor control system, and then the real-time torque deviation value calculated by iterative learning is compensated to the system control current set end. By reducing the influence of higher harmonics in the control current, the torque ripple is suppressed. Research results show that this method has high efficiency and accuracy in parameter optimization, further improving the ILC performance, effectively reducing the impact of higher harmonics, and suppressing the torque ripple amplitude.

PMSM Torque Ripple Minimization Based on Novel Low Carrier Ratio PWM Technique

Harmonic injection is commonly used in permanent magnet synchronous motor torque ripple minimization (TRM) of electric vehicle. Traditional inverter switching frequency limits TRM application at high speed due to harmonic modulation accuracy and inverter loss. To achieve TRM in the whole speed range and reduce inverter loss, a novel online calculated low carrier ratio pulsewidth modulation (LCRPWM) is proposed in this article. The carrier ratio determining regular according to the injected harmonics is established first. The relationship between injected harmonics and LCRPWM switching angle is revealed and a set of nonlinear equations is established. Thus, the problem is transformed from solving nonlinear equations into optimization by establishing a cost function. The analytical solutions of nonlinear equations are obtained, which avoids iterative operation and plunging into local minimum. Therefore, the switch angle solution method is suitable for online calculation. The LCRPWM is verified in simulation compared with the traditional regularly sampled space vector PWM, which achieves better results in voltage harmonic injection and flux tracking at a much lower switching frequency. At last, the LCRPWM is used in a test bench experiment that shows good TRM effects. The influence of sideband harmonics on torque ripple is analyzed.

A stator current vector orientation based multi-objective integrative suppressions of flexible load vibration and torque ripple for PMSM considering electrical loss

To store energy from the grid into spiral torsion spring (STS) smoothly and efficiently via PMSM, a multi-objective control problem of flexible load's vibration, PMSM's torque ripple, and electrical loss is raised, where the current studies on vibration and torque ripple are mostly addressed separately, not to mention electrical loss. This research attempts to propose a multi-objective integrative control scenario that can simultaneously solve these problems satisfactorily in a unitary nonlinear control framework. Firstly, a dynamic mathematical model of PMSM is built under stator current vector orientation, and then the model of PMSM is combined with the vibration model of STS to establish the overall system model of STS driven by PMSM with considering motor's electrical loss. Then, a backstepping control principle-based multi-objective integrative control approach is proposed to realize the suppression of flexible load's vibration and the reduction of PMSM's torque ripple and electrical loss concurrently. Meanwhile, this research also designs a wide range speed identification method based on the least square algorithm with a forgetting factor. Simulation and experimental results have verified that the proposed integrative control method enables the state variables to track their respective references quickly and accurately, both torque ripple and load vibration are effectively suppressed, and the operating efficiency of the whole system is improved.

Investigation on Maximum Electromagnetic Torque of Permanent-Magnet Synchronous Machines

Many application fields need motors that could output large torque in a short span of time such as missile and aircraft, but larger torque needs larger volume that could influence the system performance. Therefore, promoting the motor's maximum torque with small volume is the new challenge for motors. So, this paper presents a method for analyzing maximum electromechanical torque (with rate speed) of PMSM without the consideration of thermal effect produced by copper loss. This paper also discusses the factors that influence maximum torque of PMSM under the condition of i d = 0 control mode. A function between motor torque and the inner parameters is first obtained under the constraint of electrical and magnetic saturation. For verifying the accuracy of the function and its results, the characteristics of the series motors with different inner parameters that are obtained in the function are testified by finite element method (FEM) software. Finally, a prototype motor is selected to be manufactured to verify the analysis result. Based on the torque experiments result, it could verify the accuracy of the function that describes the rule of PMSM maximum torque. Based on FEM software and prototype test verifying, the method could supply the theoretical support for PMSM maximum torque design.

Dual Three-Phase PMSM Torque Modeling and Maximum Torque per Peak Current Control Through Optimized Harmonic Current Injection

Vector space decomposition (VSD) model is widely used for dual three-phase permanent magnet synchronous machine (dual-PMSM) control, in which two direct-quadrature (DQ) frames, DQ1 and DQ2, are introduced to facilitate the controller design. Existing studies show that harmonic current injection in DQ2 frame can increase the output torque for a given peak phase current, which is referred as maximum torque per peak current (MTPPC) control. However, the injected harmonic current will induce a small dc torque and the harmonic torque. This paper first proposes a comprehensive torque model considering the harmonics in PM flux linkages, inductances and stator currents to investigate the induced torque components, which are neglected in existing approaches. These torque components are then considered in the harmonic current design to improve the MTPPC control performance. The harmonic current design results in a multiobjective optimization problem, and genetic algorithm (GA) is employed to optimize the harmonic current to maximize the output torque with minimal torque harmonic. Compared with existing approaches, the proposed approach is applicable to both surface-mounted and interior dual-PMSMs. Experimental investigations on a laboratory interior dual-PMSM show that the output torque of the test motor can be increased by more than ten percent with a negligible increase in torque ripple.

Design of Electric Linear Load Simulator based on LabVIEW+PXI

In order to realize the hardware-in-the-loop (HIL) experiments of a certain type of electric linear actuator in the laboratory, an electric linear load simulator (ELLS) based on LabVIEW+PXI platform was developed to simulate the external force of the actuator under actual working conditions. In structural design, the ball screw is used to convert the PMSM torque into linear force. In hardware design, the system is built using the upper-lower computer system architecture based on PXI bus. In software design, the program is written in LabVIEW, which mainly includes the data processing and display program in the upper computer and the data acquisition program, the loading motor control program and the actuator control program in the lower computer (PXI), in order to ensure the loading accuracy of ELLS, control methods such as force closed-loop PID controller, position feedforward compensation and input feedforward compensation are also introduced in the loading motor program. Finally, the ELLS was built and the signal tracking tests were carried out. The experimental results shows that the loading accuracy can reach 93.5% and 90.3% when ELLS tracks 1000N-2 Hz and 1000N-5 Hz respectively, which proved that the accuracy of ELLS satisfies the “Double Ten Index”.

Optimization methodology for control parameter of PI based on chaos prediction of electric powertrain

The electric powertrain is a nonlinear dynamic system, when electric vehicles (EVs) drive under torque control mode, unexpected oscillation of direct-axis current id and quadrature-axis currents iq of PMSM may occur in case of an unreasonable control parameter of PI regulator is set. Thus it influences effective and stable output torque of electric powertrain. The objective of this paper is to optimize the control parameter of PI regulator to improve the precision and stability of output torque of electric powertrain under torque control mode. To achieve the goal, nonlinear dynamic model of electric powertrain under torque control mode was established. Then we predicted the instability domain of control parameter of PI to instruct the optimization. Finally experimental platform was set up to operate the optimization. The optimization results were given to improve the precision and stability of output torque of electric powertrain. The results show that the output torque of PMSM continues to oscillate under EV start-up working condition and limited local oscillation occurs under low speed cruise condition. The electric powertrain cannot perform precise and stable torque control. The control parameter of PI was optimized from kp = 0.1 to kp = 0.18. The electric powertrain perform more stable torque control with more effective output torque after optimization.

Design, Analysis of the Location and Materials of Neodymium Magnets on the Torque and Power of In-Wheel External Rotor PMSM for Electric Vehicles

The technology of mounting electric direct drive motors into vehicle wheels has become one of the trends in the field of electric vehicle drive systems. The article presents suggestions for answering the question: How should magnets be mounted on the External Rotor Permanent Magnet Synchronous Machine (ERPMSM) with three phase concentrated windings, to ensure optimal operation of the electric machine in all climatic and weather conditions? The ERPMSM design methodology is discussed. Step by step, a method related to the implementation of subsequent stages of design works and tools (calculation methods) used in this type of work are presented. By means of FEM 2D software, various ERPMSM designs were analyzed in terms of power, torque, rotational speed, cogging torque and torque ripple. The results of numerical calculations related to variations in geometric sizes and application of different base materials for each of ERPMSM machine components are presented. The final parameters of the motor designed for mounting inside the wheel of the vehicle are presented (Power = 53 kW, Torque = 347 Nm; Base speed = 1550 RPM), which correspond to the adopted initial assumptions.

Maximum Torque Per Ampere Control for IPMSM Using Gradient Descent Algorithm Based on Measured Speed Harmonics

This paper proposes a novel gradient descent based maximum torque per ampere (MTPA) control algorithm for interior permanent magnet synchronous machines (IPMSMs) by using the measured speed harmonics. The proposed approach does not require machine parameters and thus is not influenced by the machine and drive nonlinearities. Hence, the proposed approach can ensure a robust MTPA control under different loading conditions. Specifically, in the proposed approach, a small q -axis harmonic voltage is injected into the machine to induce a small harmonic component in the machine speed. Based on the PMSM torque equation, the mathematical relation between the induced speed harmonic and the output torque is derived, which shows that the magnitude of the induced speed harmonic is proportional to the output torque of an IPMSM. Therefore, the speed harmonic is explored to seek the MTPA angle, in which the MTPA angle is found when the speed harmonic magnitude is maximized. In particular, the gradient descent algorithm is employed to detect the MTPA angle, which is computationally efficient and converges quickly. The proposed approach is evaluated with both simulations and experiments based on a laboratory IPMSM drive system.

Analysis on Inductance and Torque of PMSM Considering Magnetic Saturation

This paper analyses the surface-mounted PMSM which controlled by Id=0 vector control based on Ansoft in which finite element simulation of 2D static magnetic field can be operated on, then calculating and analysing the data with MATLAB, and then operating on the analysis of the change law of torque and inductance under different load conditions, and then paying more attention on the impact of magnetic saturation to torque and inductance. With the analysis of magnetic saturation, this paper puts forward a scheme of control and design used by PMSM.

Influence of Manufacturing Tolerances on PMSM Torque Ripple

Influence of Manufacturing Tolerances on PMSM Torque Ripple

Torque Ripple Minimization of PMSM Using Parameter Optimization Based Iterative Learning Control

In this paper, a parameter optimization based iterative learning control strategy is presented for permanent magnet synchronous motor control. This paper analyzes the mechanism of iterative learning control suppressing PMSM torque ripple and discusses the impact of controller parameters on steady-state and dynamic performance of the system. Based on the analysis, an optimization problem is constructed, and the expression of the optimal controller parameter is obtained to adjust the controller parameter online. Experimental research is carried out on a 5.2kW PMSM. The results show that the parameter optimization based iterative learning control proposed in this paper achieves lower torque ripple during steady-state operation and short regulating time of dynamic response, thus satisfying the demands for both steady state and dynamic performance of the speed regulating system.

Optimal State Reference Computation With Constrained MTPA Criterion for PM Motor Drives

This research proposes a procedure that maps a PMSM torque request onto optimal state (current) references. Combining the procedure with a dynamic (current) controller yields a torque controller. The maximum torque per ampere (MTPA) criterion is used to minimize conduction and switching losses. This research extends the concept to field-weakening operation to obtain high efficiency at any machine speed. The resulting constrained MTPA criterion is formalized as an optimization problem. Since it is difficult to solve directly, the maximum and intersection torque subproblems are identified. An algorithm is obtained that maps a torque onto an optimal state reference, and it is sufficiently efficient for real-time implementation. This method is compatible with a variety of state (current) controllers with/without PWM, SPM and IPM machines with saliency and reverse saliency, and a variable dc-link voltage. The proposed procedure relies on a sufficiently accurate torque model that may not be provided using rated machine parameters. Thus, an approach to compute locally optimized machine parameters is proposed that takes magnetic saturation into account. The concept is developed on a software-in-the-loop platform and evaluated on an experimental test bench.

DC-link 전압변동을 고려한 PMSM 토크제어의 성능 향상 방법

This paper proposes a PMSM torque control method considering DC-link voltage variation and friction torque. In general EV/HEV application, two dimensions look-up table(2D-LUT) is used for reference current generation due to its stable and robust torque control performance. Conventionally, this 2D-LUT is established by flux-torque table to overcome the DC-link voltage variation. However, the flux table establishment is more complex than the speed table establishment. Moreover, one flux data reflects several speed conditions in variable DC-link voltage, friction torque cannot be considered by using the flux table. In this paper, speed-torque 2D-LUT is used for current reference generation. With this table, PMSM torque control is well achieved regardless of DC-link voltage variation by the proposed control method. Simulation and experimental results validate improvement of torque control error through friction torque compensation.

Effects of V-Skew on the Torque Characteristic in Permanent Magnet Synchronous Motor

In this paper, we proposed how the V-skew applied of the rotor to inprove the characteristics of cogging torque in large PMSM. Large PMSM is difficult to apply a pitch of the diagonal magnetic skew because of the motor's structure and making. In addition, the force in the direction of z-axis occurs when the diagonal skew is applied. So we are applying the optimal v-skew to reduce torque ripple and cogging torque because this reduces the noise and vivration on the motor. Throug FEM dD analysis, we studied to find the optimal v-skew angle for reducing torque ripple.

Robust Non-Linear Direct Torque and Flux Control of Adjustable Speed Sensorless PMSM Drive Based on SVM Using a PI Predictive Controller

This paper presents a new sensorless direct torque control method for voltage inverter – fed PMSM. The control method is used a modified Direct Torque Control scheme with constant inverter switching frequency using Space Vector Modulation (DTC-SVM). The variation of stator and rotor resistance due to changes in temperature or frequency deteriorates the performance of DTC-SVM controller by introducing errors in the estimated flux linkage and the electromagnetic torque. As a result, this approach will not be suitable for high power drives such as those used in tractions, as they require good torque control performance at considerably lower frequency. A novel stator resistance estimator is proposed. The estimation method is implemented using the Extended Kalman Filter. Finally extensive simulation results are presented to validate the proposed technique. The system is tested at different speeds and a very satisfactory performance has been achieved.