Shiqiang Zheng

Adaptive Compensation Method for High-Speed Surface PMSM Sensorless Drives of EMF-Based Position Estimation Error

To improve the performance of the surface permanent magnet synchronous motor drives, a sensorless control scheme based on the sliding-mode observer with an orthogonal phase-locked loop (PLL) incorporating two synchronous frequency-extract filters (SFFs) is proposed. The rotor position estimation errors are analyzed. The analysis results show that the harmonic errors of the estimated signal are hard to eliminate completely. Therefore, an improved adaptive notch filter - The SFF is proposed to extract the fundamental wave of the rotor position estimation before applying to the PLL. This method of the PLL combined SFFs can compensate the estimated back electromotive force harmonic error efficiently and adaptively. An experimental driveline system used for testing the electrical performance of the developed magnetically suspended motor is built. The effectiveness and the feasibility of the proposed method are validated with the experimental results.

Sensorless Control for High-Speed Brushless DC Motor Based on the Line-to-Line Back EMF

A sensorless control method for a high-speed brushless DC motor based on the line-to-line back electromotive force (back EMF) is proposed in this paper. In order to obtain the commutation signals, the line-to-line voltages are obtained by the low-pass filters. However, due to the low-pass filters, wide speed range, and other factors, the actual commutation signals are significantly delayed by more than 90 electrical degrees which limits the acceleration of the motor. A novel sensorless commutation algorithm based on the hysteresis transition between “90-α” and “150-α” is introduced to handle the severe commutation retarding and guarantee the motor works in a large speed range. In order to compensate the remaining existing commutation errors, a novel closed-loop compensation algorithm based on the integration of the virtual neutral voltage is proposed. The integration difference between the adjacent 60 electrical degrees interval before and after the commutation point is utilized as the feedback of the PI regulator to compensate the errors automatically. Several experiment results confirm the feasibility and effectiveness of the proposed method.

Power Consumption Reduction for Magnetic Bearing Systems During Torque Output of Control Moment Gyros

The power consumption of actuators is an important concern for the spacecraft attitude control system. This paper presents a power consumption reduction method for permanent magnet biased active magnetic bearings (AMBs) during torque output of control moment gyros (CMGs). For simplicity of analysis, a simple single degree-of-freedom (DOF) AMB system undergoing an external load force is first presented. An operating point adaptive regulation based on current-integral feedforward method is proposed to realize the coil current reduction with a reference position offset. Then the proposed method is extended to the case of the 4-DOF AMB-rotor system. In order to improve the dynamic response of the current-integral output, a dynamic regulator is incorporated into the feedforward loop. The parameter range for stability and dynamic properties of the AMB-rotor system with and without using the dynamic regulator have also be compared and discussed. Finally, experimental results on a developed magnetically suspended double-gimbal CMG prototype validate the effectiveness of the proposed method.

Active Balancing Control of AMB-Rotor Systems Using a Phase-Shift Notch Filter Connected in Parallel Mode

The vibration controllability is an important feature in the applications of active magnetic bearings (AMBs). This paper addresses the two key challenges on the active balancing control of AMB-rotor systems: presenting a parallel-mode scheme to enhance the notch performance at high speeds, and proposing a phase-shift notch filter to ensure stable operations over the entire speed ranges. First, both the frequency characteristics of the simplified notch filter in series and in parallel mode are discussed. The analysis shows that the closed-loop system with a parallel-mode notch filter has a deeper notch depth and faster convergence. The capacities of the synchronous current elimination are also improved at high speeds. Then, an improved phase-shift notch filter connected in parallel with the controller is modeled and analyzed. In order to understand the sensibility of the proposed solution to phase-shift variations, the stability analysis of the closed-loop system in the entire operational speed range is performed using the frequency response method. Experimental results on a high-speed centrifugal air blower test rig show the effectiveness of the proposed solution.

Self-Correction of Commutation Point for High-Speed Sensorless BLDC Motor With Low Inductance and Nonideal Back EMF

This paper presents a novel self-correction method of commutation point for high-speed sensorless brushless dc motors with low inductance and nonideal back electromotive force (EMF) in order to achieve low steady-state loss of magnetically suspended control moment gyro. The commutation point before correction is obtained by detecting the phase of EMF zero-crossing point and then delaying 30 electrical degrees. Since the speed variation is small between adjacent commutation points, the difference of the nonenergized phases terminal voltage between the beginning and the end of commutation is mainly related to the commutation error. A novel control method based on model-free adaptive control is proposed, and the delay degree is corrected by the controller in real time. Both the simulation and experimental results show that the proposed correction method can achieve ideal commutation effect within the entire operating speed range.

Sensorless Low-Current Start-Up Strategy of 100-kW BLDC Motor With Small Inductance

This paper focuses on the start-up strategy of a high-speed 100-kW brushless dc motor with small inductance using a voltage comparator. This paper includes three key technique contributions: 1) determining zero-speed positioning, 2) removing high-frequency disturbances, and 3) optimizing the controller parameters. The sensorless low-current start-up strategy is based on an amplification circuit: a low-pass filter circuit and a signal modulate circuit. The amplification circuit is used to amplify the amplitude of back electromotive force for detecting the rotor position at low speed, the low-pass filter circuit is used to remove high-frequency disturbances, and the signal modulate circuit is used to obtain the rotor position signal. A hysteresis control strategy is proposed against the load disturbance in the start-up stage. Experimental results show that the proposed sensorless start-up strategy can realize a low-current start-up.

Precise Control for Gimbal System of Double Gimbal Control Moment Gyro Based on Cascade Extended State Observer

Coupling torque, nonlinear friction, and unmodeled dynamics are the main constraints that influence the angular speed precision of the gimbal systems in double gimbal control moment gyros (DGCMGs). This paper explores a novel angular speed tracking control method based on the cascade extended state observer (CESO). The coupling torque, nonlinear friction, and unmodeled dynamics are considered as the systems lumped disturbance, which is estimated by the designed CESO. By introducing a state feedback controller, the disturbances can be eliminated from the output channel of the system. Both simulation and experimental results confirmed the feasibility and effectiveness of the proposed method.

Design considerations of winding for low-voltage high-speed permanent magnet motor

The electrical frequency of high speed permanent magnet motor leads to pronounced parasitic effects, such as skin, proximity and circulating current effects. The parasitic effects result in uneven distribution of currents and the increase of the ac resistance of the winding. Ac resistance is proportional to the winding loss and the ratio of ac resistance of winding to dc resistance of winding is used to characterize the winding loss. The parameters of winding, as well as the parameters of slot dimensions of stator, will affect the degree of parasitic effects. The influences of some design parameters are analyzed in this paper.

Unbalanced Magnetic Pull Effect on Stiffness Models of Active Magnetic Bearing due to Rotor Eccentricity in Brushless DC Motor Using Finite Element Method

We firstly report on an investigation into the unbalanced magnetic pull (UMP) effect on the static stiffness models of radial active magnetic bearing (RAMB) in brushless DC motor (BDCM) in no-loaded and loaded conditions using the finite element method (FEM). The influences of the UMP on the force-control current, force-position, current stiffness, and position stiffness of RAMB are clarified in BDCM with 100 kW rated power. We found the position stiffness to be more susceptible to UMP. The primary source of UMP is the permanent magnets of BDCM. In addition, the performance of RAMB is affected by the UMP ripples during motor commutation and also periodically affected by the angular position of rotor. The characteristic curves of RAMB force versus control current (or rotor position) and angular position of rotor affected by the UMP are given. The method is useful in design and optimization of RAMB in magnetically suspended BDCMs.

High-Precision Sensorless Drive for High-Speed BLDC Motors Based on the Virtual Third Harmonic Back-EMF

In order to improve the performance of the high-speed brushless direct current motor drives, a novel high-precision sensorless drive has been developed. It is well known that the inevitable voltage pulses, which are generated during the commutation periods, will impact the rotor position detecting accuracy, and further impact the performance of the overall sensorless drive, especially in the higher speed range or under the heavier load conditions. For this reason, the active compensation method based on the virtual third harmonic back electromotive force incorporating the SFF-SOGI-PLL (synchronic-frequency filter incorporating the second-order generalized integrator based phase-locked loop) is proposed to precise detect the commutation points for sensorless drive. An experimental driveline system used for testing the electrical performance of the developed magnetically suspended motor is built. The mathematical analysis and the comparable experimental results have been shown to validate the effectiveness of the proposed sensorless drive algorithm.