Detent Force Compensation for PMLSM Systems Based on Structural Design and Control Method Combination

Abstract

Abstract-As direct-drive actuators, permanent magnet linear synchronous motors (PMLSMs) are widely used in high velocity and high precision applications. The detent force, however, can deteriorate the performance, even excite the mechanical resonance. This paper focuses on a novel detent force compensation scheme for PMLSM systems through a combination of structural design and control method. First, due to the bandwidth constraint of the control system, eliminating high frequency ripples is unfeasible; skewed permanent magnets (PM) considering an optimal skewing length are designed to suppress high order harmonic components. Second, based on the model of PMLSM with skewed PMs, a linearization observer is derived and applied independently to the velocity controller for further diminishing low order harmonic components. To facilitate implementation in the digital control system, a discretization method taking account of estimated errors is designed. Through the online calculation, the estimated detent force is injected to the control system in a feedforward way. To tune the proposed scheme properly, the convergence of the algorithm is analyzed by utilizing Lyapunov stability theory. Simulation studies are performed to prove the effectiveness of the proposed method, and experiments are provided to confirm the theoretical analysis and simulation results.Index Terms-Permanent magnet linear synchronous motors (PMLSMs), detent force, skewed permanent magnet, discretetime linearization observer, stability analysis.

Analysis and Minimization of Detent End Force in Linear Permanent Magnet Synchronous Machines

“…However, the larger skewed length will increase the axial force and reduce the reciprocating range for the LPMSM with short stroke. Meanwhile, some Analysis and Minimization of Detent End Force in Linear Permanent Magnet Synchronous Machines L other methods have been investigated, such as shape optimization of the exterior teeth [18], current compensation [6], [19], and PM optimization [20], and each has both the advantages and disadvantages. For the LPMSM with short stroke, the secondary end effect is also non-negligible, while only limited literature has considered this problem [21].…”

Detent Force Reduction of an Arc-Linear Permanent-Magnet Synchronous Motor by Using Compensation Windings

“…However, few researches have considered to combine the control strategy and structure optimization together. [26] used skewed permanent magnets to suppress high order harmonic components and a linearization observer for further diminishing low-order harmonic components, but the motor structure itself is still in a conventional way. In addition, the PMLSM has both end effects from the primary and secondary sides.…”

No-Load Magnetic Field and Cogging Force Calculation in Linear Permanent-Magnet Synchronous Machines With Semiclosed Slots

“…INEAR permanent magnet (PM) synchronous machines (LPMSMs) can provide direct thrust force without the need of conversion from rotational torque to linear force, and thus are increasingly employed in various industrial and military applications, such as railway transportation, robotic systems and electromagnetic launchers [1][2][3][4][5]. Among various types of LPMSMs, the slotted topologies suffer from the slot and end effects which increase the thrust fluctuation and decrease the machine controllability.…”

“…The Schwarz-Christoffel (SC) conformal mapping can consider the slot and end effects by transforming a complex structure into a relatively simple one, in which the analytical field solution can be readily obtained [1], [18][19][20]. In [1] and [18], the magnetic field distribution of LPMSMs is predicted by the subdomain (SD) method, i.e.…”

“…In [1] and [18], the magnetic field distribution of LPMSMs is predicted by the subdomain (SD) method, i.e. the whole field domain is firstly divided into a few subdomains with adequate boundary and interface conditions, and then the field in each subdomain is solved analytically.…”