【作者】 朱俊杰；

【导师】 粟梅；

【作者基本信息】 中南大学 ， 控制科学与工程， 2014， 博士

【摘要】 无位置传感器无刷直流电机控制技术可以解决安装位置传感器给系统带来工艺复杂、受工作运行环境限制等诸多问题,同时可以提高系统可靠性和抗干扰性能。论文针对无位置传感器无刷直流电机转子位置信号检测、无位置传感启动策略、电机换相与非换相时转矩脉动等问题展开研究。具体研究内容包括以下几个方面：1.综述了无刷直流电机关键控制技术的研究现状与水平,建立了无刷直流电机的数学模型,并以数学模型为基础,在Matlab/Simulink环境下搭建了位置传感器无刷直流电机控制系统的仿真模型,对仿真结果进行了分析,验证了模型的正确性。搭建了位置传感器无刷直流电机控制系统实验平台,对实验结果进行分析,验证了设计方案的正确性,为无位置传感器无刷直流电机关键控制技术的研究奠定了理论基础和实验研究对比依据。2.针对无位置传感器无刷直流电机反电势过零检测在极端速段存在的问题(即无位置传感器无刷直流电机在高速段时反电势信号过大,容易造成检测电路无法正常工作甚至损坏,而在较低速段时,反电势信号又难以有效检测),提出了一种反电势过零检测新方法及对应的检测电路。首先,根据速度反馈控制信号占空比切换低速区与高速区反电势采样方式。在PWM_OFF期间进行低速段采样,可以有效改善在低速区反电势过零检测效果。在PWM_ON期间进行高速段采样,转换相应的硬件电路(三相电路上分别并联一组三极管控制的电阻分压开关电路),同时参考电机转速线性调节控制信号占空比,以此控制三极管通断从而调节电阻分压开关电路阻值,可以避免高速时反电势幅值高于检测电路供电电压的危险。实验结果表明：采用新的反电势过零检测新方法可以保证电机工作于更宽的转速范围内。3.针对无位置传感器无刷直流电机启动问题,提出了一种无位置传感器无刷直流电机准闭环启动方法,也即转子初始位置精准预定位与加速过程中优化定位相结合的准闭环三段式启动方法。在电机绕组中施加短时间脉冲电压矢量,通过检测直流母线电流可以将转子位置锁定在600电度角范围内,在此基础上通过向指定绕组通电与检测电流并比较电流阈值从而完成转子精准预定位。预定位后进入优化定位与加速阶段,此时电流比较阈值作为换相条件,保证转子在加速过程中准确换相,当转速达到一定值时(反电势过零信号产生时)系统切换到反电势运行状态。实验结果表明：电流阈值比较作为反馈量,保证了启动过程中电机在定位、加速、切换等各个环节中均形成闭环控制。通过设置电流比较阈值的大小不仅可以调节预定位精度还能调节加速过程中换相的灵敏度,可以保证系统适应各种不同场合需求与应用。4.针对无刷直流电机转矩脉动限制了其在高端领域的应用,提出了一种在非换相期间采用基于电压空间矢量的控制方法实现无刷直流电机的直接转矩控制,在换相期间,以转矩脉动为控制量,对逆变电源开关管进行独立PWM调制的方法抑制转矩脉动的产生。直接转矩控制中存在反电势获取困难的问题,目前主要采用滑模变结构反电动势状态重构的方法解决此类问题。但是,滑模变结构控制在本质上的不连续开关特性将会引起系统的抖振,提出了采用分段式滑模变结构状态重构的方法抑制系统抖振并重构反电势。首先,在Matlab/Simulink中完成了无刷直流电机控制系统中分段式滑模变结构状态观测器模块、磁链与转矩计算模块、磁链扇区选择模块、电压空间矢量选择等模块的建模与仿真,并在此基础上,构建了基于直接转矩控制的无刷直流电机控制系统的整体仿真模型,对仿真结果进行了分析,验证了所提方法的有效性。最后搭建了基于直接转矩控制的无刷直流电机实验平台。实验结果表明：无刷直流电机在换相期间和非换相期间转矩脉动得到了有效抑制,与传统控制方法相比较,本系统进一步提高了系统的快速性与鲁棒性。更多还原

【Abstract】 Sensorless control strategy for brushless DC motor (BLDCM) can not only solves the problems, such as complicated craftwork, restricting of running environment, which generated by installing position sensor, but also improves the reliability and anti-interference ability of the system. This paper aims at studying rotor position detection, sensorless start-up strategies, and torque pulsation in commutation and non-commutation period of brushless DC motor without position sensor. The specific research contents include the following aspects:1. The status and level of the sensorless control strategy research are summarized. The mathematical model of BLDCM is set up. And based on the mathematical model, the simulation of the BLDCM with position sensor is established. Simulation module is verified according to experimental results and theoretical analysis. Sensorless BLDCM control system platform is built up, and design scheme is verified after experiment, which lays foundations of the theoretical basis and provides contrasting basis of sensorless technology.2. Aiming at the back electromotive force (BEMF) zero-crossing detection problem in extreme speed region (Namely the BEMF signal is too larger at high speed period, thus causing detecting circuit to abnormally work and even to damage the circuit; However at the low speed, the signal is so low that can hardly be detected.), a novel BEMF zero-crossing detecting method and the correspondingly detecting circuit is proposed. Sampling method is switched between high speed region and low speed region, according to the duty ratio of speed feedback signal. Zero-crossing detection is effectively improved in low speed region by using low speed sampling method in the pulse width modulation_OFF(PWM_OFF) interval. While in high speed region, high speed sampling method is used in pulse width modulation_ON(PWM_ON) interval and corresponding hardware circuit (voltage division circuit being controlled by transistor paralleling with each phase circuit) is switched. In the meantime, duty ratio of control signal is adjusted linearly according to the rotor speed, by which the on-off of transistor is controlled and then mediates the resistance of resistance divider of switching circuit. Therefore, the dangerous state that the BEMF amplitude is greater than the power supply of the detecting circuit can be avoided. Experiment results indicate that the new proposed BEMF zero-crossing detecting method can ensure brushless DC motor operate steadily in a wider speed region.3. Aiming at the starting problem of sensorless BLDCM, a novel quasi-closed-loop start-up strategy is proposed, which integrates the precise pre-location of initial rotor-position and the location optimization in accelerating process. When short-width-time pulse voltage vectors are injected into3-phase stator windings, the initial rotor-position are locked in a60°electrical angle range through detecting the DC bus current. On this basis, the precise pre-location is achieved by detecting the current when constant voltage is applied to the assigned stator windings and comparing the threshold of the current. After pre-location, location optimization and acceleration process proceeds. In this process, the current comparing threshold is used as condition to ensure the correct commutation in accelerating period. The system can be switched to BEMF detection mode when the rotor is accelerated from standstill to certain speed (when BEMF zero-crossing signal produces). Experimental results show that, using current threshold as feedback insure that location, acceleration and switching steps are all under closed-loop control. Pre-location accuracy and commutation sensitivity can be adjusted by changing the threshold value, thus ensuring the system to cater to different needs and applications.4. Aiming at the adverse effect of torque ripple which restricts its application in senior field, a direct torque control method which bases on voltage space vector is applied in non-commutation period. In the commutation period, torque ripple is viewed as controlled variable and using PWM method to restrain the produce of torque ripple in the switching of inverter. Direct torque control has the difficulty to get BEMF, so nowadays BEMF reconfiguration with sliding mode variable is used to solve such problem. However, its discontinuous switching characteristics cause system shake. Therefore, sectional sliding mode variable structure is proposed to reconfigure BEMF and restrain system shake. Sliding mode variable structure observer module, flux linkage, torque calculate module, flux linkage section selection module and voltage space vectors selection module were firstly built and simulated in Matlab/Simulink. Then, direct torque control method system with sectional sliding mode variable structure for BLDCM was built and simulated. Simulation result verifies the effectiveness. In the end, direct torque control system platform is built up. Torque ripple is restrained effectively for both commutation period and non-commutation period. Timeliness and robustness are improved compared to traditional control systems.更多还原