Zeyuan Liu

This article proposes a novel consequent-pole bearingless permanent magnet (PM) motor (CP-BPMM) with reduced PM usage, featuring additional air gaps, large axial force generation, and natural decoupling among torque, radial force, and axial force. Through the regulation of the current in axial force coil, the axial air-gap flux is adjusted to produce active axial force. With this design, the proposed CP-BPMM reduces bias PM volume while boosting active axial force and torque. The topology and operation principle of CP-BPMM are introduced first, and the radial and axial force equations are deduced. Based on the 3D finite element method, the decoupled characteristics are verified, and the influence of additional air gaps and bias PM dimensions on axial force is analyzed. To demonstrate the merits of the proposed CP-BPMM, comparative performance analyses of the electromagnetic and suspension performance are performed between two CP-BPMM designs, validating the superiority of the proposed motor.

In this paper, a sensorless finite-control set model predictive torque control (FCS-MPTC) strategy is proposed for switched reluctance motor (SRM) drives. To minimize the switching vector candidates and relieve the computing pressure in traditional MPTC methods, the flux linkage closed loop is adopted to assist candidate vector screening. In the controller, the flux linkage of each phase is calculated via the flux integral with the terminal voltage and phase currents. Through alpha belta transformation, the rotating flux angle and rotational speed can be estimated via phase locked loop (PLL). As the rotor position angle is synchronizing with the rotating flux angle, thus can be estimated directly by compensating the angle bias between them. The estimated position angle can be used for modeling the flux linkage and deriving the predicted torque, which is utilized in constructing the cost function in the MPTC method. Based on the aforementioned control process, the position sensorless control can be fully achieved. The experiments are performed under a 12/8 SRM test-bed, which verify the validity of the proposed method

In this paper, a current measurement and reconstruction control scheme for a four-phase switched reluctance motor (SRM) drive system with two current sensors is proposed. To implement the proposed scheme, following steps are included. Firstly, a compact power converter topology with modified current sensor measurement connection structure is developed, which utilized only 6 power switches and two current sensors. Secondly, in order to suppress the slow demagnetization and excessive negative torque caused by the shared reuse of power switches in the converter, two pulse injection schemes have been developed. Thirdly, based on the pulse injection scheme, a simplified four phase current reconstruction logic has been developed to ensure reliable estimation of phase currents from the measured currents of two current sensors. Detailed analysis and experiments are implemented with an 8/6 structure SRM prototype system, which fully verify the effectiveness of the proposed converter system topology and control schemes.

A traditional bearingless switched reluctance motor (BSRM) can only achieve two-degree-of-freedom (2DOF) radial levitation of its rotor shaft. In this article, an 18/16-pole three-DOF (3DOF) BSRM with biased permanent magnets (PMs) are proposed, which allows both axial and radial levitation, and its suspended windings are driven by a four-phase five-bridge-arm power inverter. First, the decoupled characteristics of this 3DOF BSRM are proved by the suspended force model and 3-D finite element analysis. Second, a control scheme consisting of three independent channels for radial force, axial force, and torque is designed for this motor. Then, based on the space vector pulse width modulation (SVPWM), a radial current algorithm for radial force control and an axial current algorithm for axial force control have been developed, respectively. Finally, a PM-biased 3DOF BSRM is prototyped and tested for experimental validation.

Due to insufficient current tracking capability, traditional control methods generate significant torque and levitation force ripples, which are detrimental to system stability. This article proposes a novel predictive current control (PCC) algorithm by integrating the structural characteristics of a 12/8 bearingless switched reluctance motor with wider rotor teeth (BSRMWR). Compared to conventional predictive current methods, the proposed algorithm eliminates the need for prestored magnetic flux or inductance tables, significantly simplifying implementation. Furthermore, to minimize copper loss, the reference current criteria are optimized using a Lagrange function. A novel force sharing function (FSF) is also designed to compensate for computational delays. Finally, simulation and experimental results validate the effectiveness and feasibility of the proposed method.

In this article, a cost-function extremum seeking-based model prediction torque control (CES-MPTC) method of permanent magnet synchronous motor with sensorless position estimation is proposed. First, as the predictive torque and flux linkage are the functions of the DQ-axis voltage components, once the partial derivative of the cost function with the DQ-axis voltage components are zero, the extreme point of the cost function can be located and the optimal voltage vector can be directly represented by the calculated DQ-axis voltage components. Using the calculated DQ-axis voltage components as the inputs of the space vector pulsewidth modulation module, the inverter can be controlled with fixed switching frequency as the traditional vector control. Then, an improved slide model observer-based sensorless position estimation scheme is proposed with hyperbolic sinusoidal function, frequency adaptive complex coefficient filter and quadrature phase-locked loop integrated. The sensorless position estimation scheme can be integrated with the proposed CES-MPTC, which can ensure enhanced rotor position measurement accuracy and reliable sensorless operation. Finally, detailed experimental results are provided to verify the validity of the proposed scheme.

In this paper, a compact single current sensor measurement based four-phase SRM integrated drive system is developed. Based on the current measurement characteristics of this drive system, the phase current reconstruction and demagnetization current suppression strategies are proposed. To ensure reliable operation of the SRM, two key issues are considered: 1) The four-phase current should be obtained from the only measured bus current signal; 2) As the non-conducting phases are unable to demagnetize normally with traditional control algorithms, serious negative torque effects exist. For the first issue, a four-phase current reconstruction method is proposed by decoupling the adjacent two-phase currents in the overlapping conduction regions. For the second issue, high-frequency pulses are injected in the shared upper power switch of the bridge arm where the conducting phase located, providing rapid demagnetization for the other phase in the same bridge arm. The two methods are fully decoupled and can be integrated freely to achieve current reconstruction and demagnetization current suppression. Based on these methods, a hybrid control algorithm that can satisfy the operation requirement in different speed range is developed for the SRM drive. Experiments have been implemented in an 8/6 structure SRM prototype based system, and detailed experimental results verify the effectiveness of the proposed methods.

The coupling between torque and radial force, and between the two radial forces is detrimental to the efficient control and performance improvement of the bearingless switched reluctance motor (BSRM). In the article, an 18/16-pole permanent magnet (PM) biased BSRM with radial force windings driven by a three-phase full-bridge inverter is presented. To solve the coupling between two radial forces in this proposed BSRM, three of its derived decoupled topologies have been developed, and the decoupled characteristics of these structures are proved by the radial force mathematical model and finite element analysis. Further, based on the space vector pulse width modulation (SVPWM) technique for three-phase full-bridge inverters, a one-cycle digital control scheme for the radial force control applicable to four types of BSRMs has been developed. Finally, a BSRM is prototyped and tested for experimental validation of radial levitation.