Bangcheng Han

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.

Optimization of Damping Compensation for a Flexible Rotor System With Active Magnetic Bearing Considering Gyroscopic Effect

Active magnetic bearing (AMB) levitated rotating machineries are always required to operate above the rotor first bending critical speed to achieve a high power density. It is important to ensure safe rotor run-down through critical speeds. This paper presents an optimization of damping compensation for a flexible rotor to make maximal use of the limited electromagnetic force to retain flexible deformation. The design, rotor modal properties, and bending model test for an AMB test rig which typifies a 10-kW centrifugal compressor are described in detail. The optimal compensation phase angle with and without considering the gyroscopic effect is first derived from a theoretical model. The flexible deformations with the different control radius and phase are also analyzed. Then, the phase angle from flexible deformation to electromagnetic force in the existing control system is experimentally identified. A phase-shift filter is designed to compensate the corresponding phase difference around the bending frequency. The damping compensation experiments validate the proposed optimization approach.

High-Precision Rotor Position Detection for High-Speed Surface PMSM Drive Based on Linear Hall-Effect Sensors

Accurate rotor position detection is essential for the surface permanent magnet synchronous motor (SPMSM) drive system to realize the stable and reliable operation. In this paper, two linear hall-effect sensors are utilized to detect the rotor position. However, the estimated errors in the measured signals, especially the harmonic components, impact on the accuracy of the rotor angle estimation significantly. For this reason, a high-precision rotor position detection method, which is based on the synchronous frequency extractors (SFEs) is presented. Two SFEs are used to filter out the high-order harmonics contained in the hall-effect signals. Further, the estimation of the rotor speed is used for the field-oriented control scheme of the PMSM. The proposed method is advantageous since it is simple, low cost, and high estimation accuracy. Finally, an experimental driveline system used for testing the electrical performance of developed high-speed magnetically suspended motor is built. The experimental results validate the feasibility and effectiveness of the proposed method in whole speed range.

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.

Field Balancing of Magnetically Levitated Rotors without Trial Weights

Unbalance in magnetically levitated rotor (MLR) can cause undesirable synchronous vibrations and lead to the saturation of the magnetic actuator. Dynamic balancing is an important way to solve these problems. However, the traditional balancing methods, using rotor displacement to estimate a rotors unbalance, requiring several trial-runs, are neither precise nor efficient. This paper presents a new balancing method for an MLR without trial weights. In this method, the rotor is forced to rotate around its geometric axis. The coil currents of magnetic bearing, rather than rotor displacement, are employed to calculate the correction masses. This method provides two benefits when the MLRs rotation axis coincides with the geometric axis: one is that unbalanced centrifugal force/torque equals the synchronous magnetic force/torque, and the other is that the magnetic force is proportional to the control current. These make calculation of the correction masses by measuring coil current with only a single start-up precise. An unbalance compensation control (UCC) method, using a general band-pass filter (GPF) to make the MLR spin around its geometric axis is also discussed. Experimental results show that the novel balancing method can remove more than 92.7% of the rotor unbalance and a balancing accuracy of 0.024 g mm kg−1 is achieved.

A Novel Integral 5-DOFs Hybrid Magnetic Bearing with One Permanent Magnet Ring Used for Turboexpander

We propose a novel combined five-degrees-of-freedom (5-DOFs) hybrid magnetic bearing (HMB) with only one permanent magnet ring (PMR) used for turboexpanders. It has two radial magnetic bearing (RMB) units; each has four poles and one thrust magnetic bearing (TMB) to control 5-DOFs. Based on one PMR, the bias flux of the two radial magnetic bearing units and the one thrust magnetic bearing unit is constructed. As a result, ultra-high-speed, lower power loss, small size, and low cost can be achieved. Furthermore, the equivalent magnetic circuit method and 3D finite element method (FEM) are used to model and analyze the combined 5-DOFs HMB. The force-current, force-position, torque-coil currents, the torque-angle position, and the stiffness models of the combined 5-DOFs HMB are given. Moreover, its coupling problems between the RMB units and the AMB unit are also proposed in this paper. An example is given to clarify the mathematical models and the coupling problems, and the linearized models are proposed for the follow-up controller design.

System Electromagnetic Loss Analysis and Temperature Field Estimate of a Magnetically Suspended Motor

A magnetically suspended permanent-magnet motor (MSPMM) system mainly consists of magnetic bearings (MBs), a motor and a rotor assembly. This paper focuses on the system analysis of an MSPMM used for a vacuum turbo-molecular pump (TMP). To ensure a normal levitation and rotation, characteristics of electromagnetic field of MBs and motor are studied. For MSPMM, loss is the main heat source. To ensure the safe and steady operation of MSPMM, loss of the MB and motor are calculated and analyzed by finite element method (FEM). For thermal aspects, temperature field is estimated. Based on these analyses, the system performance can be predictive. Considering the poor heat dissipation conditions in a vacuum environment, this system analysis including loss and temperature field is of great value for MSPMM design.

Asymmetric electromagnetic analysis and design of a permagnet biased axial magnetic bearings

In this paper, an asymmetric permagnet biased axial magnetic bearing has developed. The PM rings can not only produce bias flux, but also provide a large axial force to reduce the burden of axial bearing. As a result, the proposed PBAMB can lower the current, lower the power loss and make an easier control. Firstly, structure and operation principle are introduced. Then, the mathematical models are built based on traditional equivalent magnetic circuit. The analytical and design results are verified by finite element method (FEM). The loss is also analyzed by comparing with usual AMBs and symmetric PBAMB. The result shows the copper loss is reduced to 22% of usual AMBs and 56% of symmetric PBAMB. Finally, the design principle has been introduced in detail. The proposed PBAMB has an important reference value for magnetic bearings applied in the device when the load forces in two axial directions are different.

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.