Permanent magnet linear synchronous machines (PMLSMs)-driven motion stage for the semiconductor manufacturing equipment and machine tools has the basic requirement of high-dynamic response and high position accuracy. However, due to the direct-drive structure, the effect of parameter uncertainty including the electrical and the mechanical one and external disturbance will be directly exerted to the stage. In this paper, an integrated compensation scheme of the overall uncertainty and disturbance is proposed based on the second-order sliding mode observer (SOSMO). Firstly, an extended state model for considering the disturbance dynamics is established for both the electrical and the mechanical subsystem. To obtain high dynamic current performance, the predictive current control (PCC) is utilized to design the current controller and the SOSMO is integrated to compensate the main problem of parameter mismatch for the PCC. Furthermore, the SOSMO is also configured to estimate the force ripple, and then the observation term is applied in parallel to the velocity controller. With this integrated scheme, the disturbance of the motion stage can be simply and effectively compensated.

In this article, an augmented generalized proportional–integral observer (GPIO) is presented to estimate and then compensate for the disturbance/uncertainty both existing in the electrical and mechanical subsystems of the motion stage driven with an air-bearing permanent-magnet linear synchronous machine (PMLSM). First, a modeling method for the two subsystems, considering the disturbance/uncertainty and the integration of the measured outputs as extended states, is proposed. Second, to reduce the coupling effect of the observer gains and the measurement noises on the disturbance estimation dynamics, an augmented GPIO is designed and its convergence theorem is given. Furthermore, with the extended models, the augmented GPIO is developed for both the compensation of parameter mismatch in the predictive current control (PCC) and the force ripple estimation/suppression of the PMLSM. Finally, with the augmented GPIO, an improved PCC robustness test with time-varying parameter mismatch is conducted both in the single-current closed loop and the double-current closed loop with cascade position-current control. A simple and practical parameter-tuning procedure is also analyzed in detail for both the electrical and mechanical subsystems. The position trajectory tracking error is reduced largely with accurate and real-time force ripple compensation. Experimental setup and results are provided to validate the effectiveness of the proposed design method.

Modularization design has been widely used to reduce the detent force of permanent magnet linear synchronous motor (PMLSM). For modular PMLSM, ideally, unit motors are independent of each other and the detent force of the whole motor is the sum of that of unit motors, thus the whole motor detent force can be suppressed by adjusting the phase difference among the unit motor detent forces. But in fact, there is coupling effect between adjacent unit motors, which has adverse effect on the detent force suppression. The influence of the coupling effect is often neglected in current research. Hence, this paper carries out the research on the coupling effect for modular PMLSM: the influence of the coupling effect on the air magnetic field is clarified through magnetic field calculation; the coupling force is isolated by finite element analysis (FEA), and then the effects of key parameters are discussed; the detent force model considering the coupling effect is established, and an optimal design method adjusting the flux barrier length is presented to suppress the detent force.

To realize the precise thrust force control in permanent magnet linear synchronous motor (PMLSM) drives, this paper studies a novel design method of the high-performance current inner-loop. Firstly, to increase the control bandwidth, an improved predictive current (PCC) controller which takes account of one-step delay issue is presented on the basis of the discrete-time model of PMLSM. Secondly, as disturbance factors, the thrust ripple and parameter variation can deteriorate the controller performance inevitably. Therefore, an optimized sliding-mode algorithm with the variable exponential reaching law is introduced to suppress these two disturbances simultaneously, and the stability analysis is given to prove the convergence of the algorithm through the Lyapunov stability theory. At last, a precise experimental platform on account of the aerostatic guide is established, and experimental results are given to demonstrate the feasibility of the proposed control scheme.

The direct drive of the permanent magnet linear synchronous motor (PMLSM) requires excellent disturbance rejection capability to achieve precise position control. This article proposes an improved adaptive linear active disturbance rejection control (IALADRC) to improve trajectory tracking and disturbance rejection capability. First, we explain the difference between proportional–integral–derivative (PID) control and LADRC in terms of trajectory tracking and disturbance rejection. Unlike PID, which uses the integral controller to reject disturbances, LADRC uses the extended state observer (ESO) to decouple reference tracking and disturbance rejection. This simplifies the PMLSM control system to a second-order system, which in turn inspired the proposal of the improved LADRC (ILADRC). ILADRC reconstructs the disturbance from the position error using the inverse closed-loop model and injects it into the control output, resulting in better control performance. Due to the complex disturbance existing in the motion process of PMLSM, an improved adaptive ESO (AESO) is proposed to strike a balance between disturbance estimation and noise reduction. The ILADRC and the improved AESO are combined to form the IALADRC. Comparative experiments show that the IALADRC has excellent disturbance rejection capability and significantly improves the position control accuracy of the PMLSM system.