This paper proposes a novel integrated multi-model optimization method to enhance the accuracy and practicality of motor structure optimization for free-piston Stirling generators (FPSGs). Previous studies have been limited by oversimplification of the coupling relationship between the Stirling engine and motor, leading to imprecise or impractical results. The proposed method addresses this issue by incorporating the thermodynamic, hydrodynamic, dynamic, and electromagnetic models of the Stirling engine and motor. This comprehensive approach facilitates the appropriate consideration of various motor factors, such as load force and mass, on the stability, stroke, and frequency characteristics of the FPSG system. Furthermore, the proposed method utilizes conformal transformation and Particle Swarm Optimization to enhance computational efficiency. Motor structure optimization is carried out using the proposed approach, achieving a power density of 115.67 W/kg. The efficacy of the devised method is corroborated through finite element analysis and towing test bench experiments.

This paper investigates the influences of end turn length on Consequent-pole Vernier permanent-magnet (CPVPM) machines. Four structures are compared to discuss the trade-off between the end turn length and the gear ratio, and nine structures are compared to discuss the trade-off between the end turn length and the winding factor. It is found that, when the end turn length is taken into account, the CPVPM machines with concentrated winding have the potential to produce larger torque than those with the distributed winding. Motivated by the above observations, an integral slot concentrated winding CPVPM machine is proposed to be a promising candidate in VPM machine family, which has high torque capability, small end turn length, good fault tolerance and desired power factor. The influences of key design parameters are investigated. The machine prototype is manufactured, and the electromagnetic performances are experimentally validated.

The consequent-pole (CP) Vernier permanent-magnet (VPM) machine has been developed over the last decade. In VPM machine, the CP structure can produce considerable torque with a half volumn of the PMs compared with the regular structure, so the cost is reduced and the mechanical strength is increased. In this paper, an improvement of chamfering structure on a CPVPM machine is proposed to alleviate the flux leakage and increase the torque density. The chamfered structure is easily machined and will not influence the robustness of the rotor. The comparison results show that under the same volume and copper loss constraint, the proposed structure has smaller cogging torque, smaller torque ripple, larger torque density and larger power factor.

The structure of a submersible permanent magnet tubular linear motor (SPPMTLM) can significantly influence its load spectrum. However, existing models have not yet accounted for this effect. This paper proposes an advanced SPPMTLM model that incorporates these considerations, offering enhanced accuracy and practicality. Firstly, a dynamic sub-model of the SPPMTLM is developed to elucidate the dynamic load spectrum during one working cycle. Subsequently, a one-dimensional analytical sub-model and a lumped-parameter thermal network sub-model of the SPPMTLM are established to calculate its electromagnetic and thermal performance. The proposed model utilizes the Newton-Raphson method to address the nonlinear equations derived from the integration of the three constituent sub-models. This approach enables the detailed analysis of the coupling relationships among stress, fluid, thermal, and electromagnetic fields. Based on the proposed model, the impacts of motor structural parameters, materials, and operating conditions on the electricity consumption per ton of fluid are analyzed. Furthermore, the particle swarm optimization algorithm is applied to the proposed model to optimize SPPMTLM’s performance under different well fluid supply capacities. Finally, prototype and field experimental validations are conducted to verify the accuracy and practicality of the proposed method.

Vernier permanent-magnet machines have been attracted more and more attention because of their high torque density. In this paper, the sensorless control strategy of the novel axially magnetized Vernier permanent-magnet (AMVPM) machine is presented. First, the inductance non-linearity is investigated under different load conditions. Second, the mathematical model is established in cooperation with the finite element method. After that, the back electromotive force based sensorless control strategy is developed according to the state equation of the motor. In the sensorless drive, the model reference adaptive system (MRAS) technique incorporated with the inductance non-linearity is used for the speed estimation. The modified control strategy not only increases the stability but also improves the dynamic response of the system. Finally, the simulation results show that the modified MRAS is of high estimation precision, and the AMVPM machine can be well controlled, and the experimental results validated the theoretical design process.

This manuscript presents an analytical model for the performance evaluation of permanent-magnet tubular linear motors (PMTLMs) for submersible pumps utilization, which are critical in oil extraction application. Based on 2-D analytical method, the proposed model additionally accounts for the yoke lamination factor, and is integrated with artificial neural network to reduce the error caused by saturation. In light of the present production capabilities of most submersible pump motor manufacturers in China, this manuscript investigates the design principle for low cogging thrust ripple in cascade-structured, laminated stator PMTLMs. The Parato optimal set is built by multi-objective particle swarm optimization method aiming for largest average thrust and minimal cogging thrust ripple. Several typical structures are compared and discussed. Finally, the prototype is manufactured and tested, which proved the accuracy of theoretical analysis of this manuscript.