Wide Speed Range Sensorless AC Motor Drives, including Operation at Zero-Frequency, without using Test Signals

无传感器电机驱动是指不使用轴上安装的速度或位置传感器的驱动。由于成本、简单性和系统完整性的原因，无传感器操作是非常可取的。然而，众所周知，无位置传感器电机驱动控制在零速和低速时存在着严重的问题，这是多年来该领域的主要研究课题之一。在商业产品中使用的无传感器控制的传统方法是使用电机的数学模型来估计机器的磁链和速度。然而，低于1%到2%的基本速度，使用这种模型的位置和速度估计会恶化，并且速度和扭矩控制会丢失。最近有一种动力推动零速度无传感器驱动，用于更电动的飞机和车辆应用。对于前者，需要对不允许机械传动锁定的关键执行器进行直接机电(EM)驱动。在车辆领域，主传动系统需要直接电磁驱动，动力转向、主动悬架和制动驱动也需要直接电磁驱动。解决零转速问题的一种方法是利用交流电机的自然不对称性或凸性，这种零速问题不需要机器模型。这些凸起是由磁通饱和和电机本身的几何结构引起的。然后，可以通过处理叠加在所提供的电机电压上的测试电压信号注入的电流响应来跟踪磁通或转子位置。这些信号注入方法现在已经很好地被理解了，但是确实增加了声学噪声，降低了效率，需要额外的传感器，以及机器绕组内轴承磨损和电应力的增加。当前的建议旨在通过开发以下方法来克服上述缺点：1)不需要信号注入，该方法与通过功率转换器施加到驱动器的基波电压相集成。这消除了额外的噪音、损耗、轴承磨损和电应力问题。2)大大降低了对传感器的要求(取决于应用)。对于定制应用(例如航空航天、汽车)，目标将是一种电流传感器和一种低成本di/dt传感器。对于工业标准驱动器，目标是仅使用现有的线路电流传感器。这些目标具有相当大的挑战性。诺丁汉大学已经证明了无信号注入方法在数学上的可行性，该技术目前正在该大学获得专利。由于低成本数字控制系统中可用的高精度定时和采样技术的进步，实际调查现已成为可能。

A sensorless electric motor drive is the popular term for drives which do not use shaft mounted speed or position sensors. Sensorless operation is highly desirable for reasons of cost, simplicity and system integrity. However, it is well known that there are serious problems with sensorless motor drive control at zero and low speeds and this has been one of the main research topics in this field for many years. The conventional method for sensorless control, used in commercial products, is to estimate the machine flux and speed using a mathematical model of the motor. Below 1 to 2% base speed however, position and speed estimation using such a model deteriorates and speed and torque control is lost. There has been a recent impetus for zero speed sensorless drives for more-electric aircraft and vehicular applications. For the former, there is a requirement for direct electromechanical (EM) actuation of critical actuators in which locking of the mechanical transmission is not permissible. In the vehicular field direct EM drives will be required for the main drive train, and for power steering, active suspension and braking actuation. One approach to the solution of the zero speed problem, which does not require a machine model, has been to exploit the natural asymmetries or saliencies in AC machines. These saliencies are cause by magnetic flux saturation and the geometry of the construction of the motor itself. Flux or rotor position can then be tracked by processing the current response to a test voltage signal injection overlaid on the supplied motor voltage. These signal injection methods are now quite well understood, but do contribute to increased accoustic noise, reduced efficiency, the requirement for additional sensors, and an increase in bearing wear and electrical stress within the machine windings.The current proposal aims to overcome the above disadvantages by developing methodologies by which:1) No signal injection is required, the method being integrated with the fundamental voltage applied to the drive via the power converter. This eliminates the problems of extra noise, losses, bearing wear and electrical stresses.2) The requirements for sensors is substantially reduced (depending on the application). For bespoke applications (e.g. aerospace, automotive), the aim will be for one current sensor and one low cost di/dt sensor. For industrial standard drives the target aim is to use only the existing line current sensors. These aims are quite challenging. Mathematical feasibility of a non-signal injection method has been shown at Nottingham and the technique is currently subject to patent at the University. Practical investigation is now possible owing to advances in high-accuracy timing and sampling available in low-cost digital control systems.