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This paper proposes microstepping via a proximate in-phase current estimator (PIpCE) to improve position control performance with reduced torque ripples in permanent-magnet (PM) stepping motors. In conventional microstepping control, low-pass filters (LPFs) are used to filter out measurement noise resulting from the implemented current feedback loops. However, the phase lag caused by LPFs can degrade position control performance. In this paper, we propose a current tracking controller with PIpCE. The globally uniformly ultimately bounded current tracking error is proved via the Lyapunov theory. The proposed PIpCE also enhances current tracking performance over that of the conventional method. The proposed controller not only reduces the torque ripple caused by the phase lag but also increases the operational range of microstepping by pushing the electromechanical resonance frequency to a high-frequency region. We experimentally validated the effectiveness of the proposed method and observed that this method provides uniform position tracking performance without step-out or speed reversal, even in high-speed operation. [ABSTRACT FROM PUBLISHER]

This paper presents a phase-compensated microstepping (PCMS) for permanent-magnet stepper motors in order to overcome the steady-state position error (SSPE) limitation of conventional microstepping without position feedback. An additional phase to compensate for the SSPE is injected into the desired currents for PCMS. Proportional–integral (PI) current feedback with feedforward is proposed in order to guarantee the desired currents for PCMS. Given a desired position error and a desired velocity, the additional phase is calculated in order to ensure the desired position error. In the proposed method, the structure of the PI current feedback with feedforward is not modified, and the additional phase can be obtained by a linear interpolation with an offline generated lookup table. Therefore, it can be easily applied to existing industrial applications without any costs for additional hardwares. The experimental results validate the effectiveness of the proposed method. [ABSTRACT FROM PUBLISHER]

The application of a disturbance observer (DOB) and a variable structure controller (VSC) to current control of microstepping for permanent-magnet stepper motors (PMSMs) is studied. This is a recent approach to the current regulation of PMSM that results in improvement of position tracking performance of microstepping using only current feedback. We designed the DOB to estimate back electromotive force (EMF) in the form of a high-pass filter. Since the PMSM is a two-input one-output minimum-phase nonlinear system, the asymptotic convergence of the currents to the desired currents guarantees the asymptotic convergence of the position to the desired position in microstepping. Therefore, in order to compensate for the estimation errors of back EMFs and to guarantee the desired currents required for microstepping, the VSC is designed with a state feedback controller. The current tracking error and the integral of the current tracking error are proven to asymptotically converge to zero. Since the proposed method does not require any transformations or the calculation of sinusoidal terms, its structure is simple. The least lower bound of the absolute steady-state position tracking error during a constant-velocity period is estimated in order to analyze the performance of the proposed method. Our experimental results validate the performance of the proposed method. [ABSTRACT FROM PUBLISHER]

Abstract: We present a new approach to position control based on microstepping for the current regulation of permanent magnet stepper motor (PMSM), which consists of a Lyapunov-based controller and a passive nonlinear observer for output feedback controller design. It is shown, theoretically and by the means of experiments, that the Lyapunov-based controller with a passive nonlinear observer results in better position tracking performance of the microstepping using only the output feedback. The principle and stability of microstepping are shown using the Lyapunov method. The Lyapunov-based controller is developed in order to guarantee the desired current of microstepping for the improvement of the position tracking. The passive nonlinear observer is designed to estimate the full state using only the position feedback. Passivity theory is a tool to tune the observer gain for the PMSM. The observer gain tuning is simple and intuitive using the passivity theorem. Using a passive nonlinear observer results in the separation principle. [Copyright &y& Elsevier]

This article proposes a robust nonlinear position control for permanent magnet stepper motors. We develop a new single-input single-output model that consists of position, velocity, and acceleration using a commutation scheme to lump a system function and an external disturbance into a disturbance. An augmented observer is designed to estimate the position, velocity, acceleration, and disturbance. Because the disturbance refers to external disturbance, acceleration dynamics, and parameter uncertainties, it is difficult to accurately estimate disturbance without the high observer gain. It may result in the degradation of the position tracking performance. The nonlinear controller is then developed using backstepping to suppress the position tracking error using the input-to-state stability property. The key innovation of the proposed method is the design of the nonlinear gain to suppress the position tracking error according to the disturbance estimation error. Thus, the use of the high observer gain to accurately estimate the disturbance can be avoided. The proposed control algorithm was experimentally verified using the PM stepper motor control system and can be easily implemented in real-time using position measurements only. [ABSTRACT FROM AUTHOR]