This article presents a low detent force double-sided permanent-magnet synchronous linear motor (DS-PMSLM), which contains two flat-type stators and a mover. The mover is constituted of a fiberglass support plate and Halbach array permanent magnets attached on both surfaces of this plate, which provides a large thrust force and low mover mass for high dynamic response. For the sake of reducing the thrust ripple, a modulation method of the cogging and end forces is proposed based on the destructive interference. The even-order harmonics in cogging and end forces are reduced by adjusting the width of the side slots and the lengths of end teeth, respectively. In order to reduce the odd-order harmonics of the detent force, the cogging force and end force are modulated to reverse phases and identical amplitudes by changing the equivalent lengths of four end teeth. An integrated subdomain analytical model considering the cogging and end effects is built to optimize five structural parameters of the stators for low detent force. Finally, the prototype and testing platforms are set up and the experimental results validate that the proposed DS-PMSLM can achieve a low thrust ripple of less than 1.5 $ \%$ .

Free-piston linear generators (FPLGs) have attractive application prospects for hybrid electric vehicles (HEVs) owing to their high-efficiency, low-emissions and multi-fuel flexibility. In order to achieve long-term stable operation, the hybrid system design and full-cycle operation strategy are essential factors that should be considered. A 25 kW FPLG consisting of an internal combustion engine (ICE), a linear electric machine (LEM) and a gas spring (GS) is designed. To improve the power density and generating efficiency, the LEM is assembled with two modular flat-type double-sided PM LEM units, which sandwich a common moving-magnet plate supported by a middle keel beam and bilateral slide guide rails to enhance the stiffness of the moving plate. For the convenience of operation processes analysis, the coupling hybrid system is modeled mathematically and a full cycle simulation model is established. Top-level systemic control strategies including the starting, stable operating, fault recovering and stopping strategies are analyzed and discussed. The analysis results validate that the system can run stably and robustly with the proposed full cycle operation strategy. The effective electric output power can reach 26.36 kW with an overall system efficiency of 36.32%.

Linear motor system is normally a low-damping system to achieve high speed and high acceleration without mechanical transmission devices. Therefore, the vibration issue is serious especially in the high-speed start-stop motion process, which deteriorates the control precision and decreases work efficiency. This paper proposes a dual-sided hybrid excitation eddy current damper (ECD) to suppress the vibration of the linear motor during decelerating and stopping stages. This ECD is composed of a copper plate and two E-shape hybrid excited electromagnets. The plate is sandwiched between these dual-sided electromagnets to generate the eddy current damping force when it moves and the ECD current is excited simultaneously. The analytical model of the ECD considering leakage flux is established and verified by FEA with the deviation less than 7%. Experiments are conducted on the prototype to verify the effectiveness of its vibration restraint performance. With the active damping, the peak amplitude of the position error and the settling time are reduced by 68.88% and 33.33%, respectively.

This paper proposes a decoupling design approach for a free-piston linear generator (FPLG) constituted of three key components, including a combustion chamber, a linear generator and a gas spring serving as rebounding device. The approach is based on the distribution of the system power and efficiency, which provides a theoretical design method from the viewpoint of the overall power and efficiency demands. The energy flow and conversion processes of the FPLG are analyzed, and the power and efficiency demands of the thermal-mechanical and mechanical-electrical energy conversion are confirmed. The energy and efficiency distributions of the expansion and compression strokes within a single stable operation cycle are analyzed and determined. Detailed design methodologies of crucial geometric dimensions and operational parameters of each key component are described. The feasibility of the proposed decoupling design approach is validated through several design examples with different output power.

This article presents a new type of surface-mounted three-phase permanent magnet synchronous motor with the same number of poles and slots which has obvious advantages in cogging torque. Since the same-pole and same-slot three-phase permanent magnet motor has three or more slot types and the slots are not evenly distributed on the circumference, this article adopts an accurate subdomain model that considers the position and slot width of each slot separately to perform an analytical calculation of the magnetic field. The motor is divided into three subdomains and modeled by Maxwell’s equations, and the magnetic scalar vector equation satisfied by each subdomain is solved by the method of separation of variables. A 24-pole 24-slot three-phase permanent magnet motor consisting of 13-pole 12-slot and 11-pole 12-slot is used to verify the correctness of the proposed analytical computational model. Compared with the finite element analysis, the proposed analytical model shows high accuracy in the calculations of the magnetic flux density of the three subdomains.

Periodic short-term high overload operation of robot joint motors can significantly influence the temperature rise of the motors. To accurately analyze the temperature rise of the joint motor under periodic overload conditions, this paper develops a Lumped Parameter Thermal Network (LPTN) model that considers permanent magnet demagnetization, saturation, cross saturation, and temperature effects. First, the impact of temperature rise on permanent magnet demagnetization is considered, and its effect on the ultimate output torque of the motor is analyzed. Subsequently, an electromagnetic torque model accounting for thermal effects and magnetic circuit nonlinearity is established. Based on this model, an LPTN that considers temperature and permanent magnet demagnetization is developed. The accuracy of the thermal network model is validated through finite-element analysis. Finally, an experimental platform for motor temperature rise is constructed, and experiments are conducted. Experimental results indicate that the temperature estimation errors of both methods are within 5% under both single working conditions and periodic overload conditions, meeting practical engineering requirements. It provides a crucial reference for the temperature field analysis of motors under periodic short-term high overload conditions.