Open-phase fault is a common failure in PMSM, which would degrade motor performance and increase its loss due to the unbalanced phase currents. However, conventional fault-tolerant strategies suffer from the tracking problem of sinusoidal current references. In this paper, different from previous fault-tolerant strategies, a new fault-tolerant method for open-phase PMSM is proposed by designing a novel transformation matrix for current/voltage references. With the new transformation matrix, the voltage/current references in d-q frame can be transformed to the phase voltage/current references of the two remaining phases. With the proposed method, open-phase fault-tolerant implementation can be much easier (PI controller is enough) and its performance can be much higher. Besides, as the tolerant method is designed based on four-leg inverter, stronger fault-tolerance capability can be obtained compared with the three-phase inverter-based method. Finally, the experimental results confirm the validity of the proposed fault-tolerant method.

Sensorless control is an effective measure to improve reliability and reduce cost for the brushless dc motor (BLDCM). However, the performance is generally related to the cost and complexity of the system, making it difficult for engineering applications. Therefore, this article proposes a high-dynamic and low-cost sensorless control method for high-speed BLDCMs using the rich built-in resources of the digital signal processor. First, a variable relating to the commutation moment is constructed and detected, which is not affected by modulation noise. Then, a detailed commutation process is presented based on the relationship between the back electromotive force (back-EMF) integral and the commutation point. Moreover, an integral prediction method is proposed by linearizing the back-EMF to cope with the effect of discrete sampling on commutation accuracy. Finally, experimental tests are performed on a magnetically suspended control moment gyroscope, which verifies the effectiveness of the proposed high-dynamic and low-cost sensorless control method.

Open-phase fault may lead to motor efficiency and performance degradation. Various fault-tolerant methods have been proposed to reconfigure the controller and to track the sinusoidal current references. Unfortunately, the time-varying sinusoidal current commands are difficult to be tracked. In order to improve open-phase permanent magnet synchronous motor (PMSM) performance, a new open-phase PMSM fault-tolerant method is proposed in this paper, which is realized based on a novel reference frame transformation. With the new frame transformation, the position-dependent sinusoidal current commands are transformed to dc variables. Thus, the current controller design becomes very easy (PI controller is enough). The experimental results confirm that with the proposed method the PMSM fault-tolerant performance is enhanced distinctly compared with the conventional fault-tolerant methods.

As aerospace applications, high reliability and low power consumption operation of the brushless direct current (BLDC) motor for the magnetically suspended control moment gyro (MSCMG) is the primary consideration. To guarantee reliability, the sensorless control method without physical position sensors is adopted. Due to the phase lag caused by hardware and software, the commutation error is inevitable. In order to improve commutation accuracy for reducing losses, this paper proposes a fast commutation error compensation method. First, the control topology of the BLDC motor with a Buck converter and the commutation points detection circuit are presented. Then, the conducting back electromotive force (EMF) in a novel derived DC-link voltage expression is estimated through an extended state observer (ESO). Finally, the commutation error is extracted through the conducting back-EMF for compensation. Different from the conventional closed-loop correction method based on the back-EMF symmetry, the proposed commutation error compensation method can obtain the commutation error within only one commutation cycle by a continuous estimation with the ESO. The effectiveness of the proposed fast commutation error compensation method was evaluated with an MSCMG system.

Accurate commutation point is essential to ensure the ideal torque performance and low power consumption for brushless DC (BLDC) motor. In order to achieve the precise sensorless commutation at a constant or the rapidly varying speed, a fast commutation error correction method is proposed in this article. First, it is pointed out that the controlled variable variation, the high rate of commutation error relative to the low speed and the nonlinearity of the correction loop are the main origins of commutation error when the speed varies rapidly. Then, a novel commutation error correction method is proposed through the following three aspects: first, constructing a controlled variable first utilized for commutation correction, which keeps constant at the rapidly varying speed; second, incorporating feedforward compensation for the phase shift caused by low-pass filter; third, using feedback linearization to reduce the nonlinearity of the correction loop. The proposed commutation error correction method not only corrects the commutation error fast at a constant speed, but also achieves precise commutation when the rotor speed changes rapidly. Moreover, the proposed method is based on the principle of closed-loop control, thus, it also has the advantage of anti-interference. At last, the experimental results are shown to validate the effectiveness of the proposed method.

Imaging the heart magnetic field to diagnose is a cutting-edge development direction to overcome cardiovascular diseases. Since the heart's magnetic field is extremely weak, the magnetic field must be detected in a magnetic shielding device when imaging the heart magnetic field. To improve the antidisturbance ability of the magnetic shielding device, this article proposes a disturbance suppression based high-precision magnetic field compensation (MFC) method for a magnetic shielding cylinder (MSC). A set of experimental system based on a MSC is built up and experiments verify the effectiveness of the proposed method in suppressing the external disturbance magnetic field.