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Conventional proportional/proportional-integral (P/PI) speed controller for today's servo drives has to be manually tuned at the controller switching set point by trial and error, which may translate into drive system downtime and a subsequent loss of productivity. The adjustable drive performance is heavily dependent on the quality of expert knowledge. The performance becomes inadequate in applications where the operating conditions change in a wide range, i.e., tracking command, acceleration/deceleration time, and load disturbances. In this paper, we discuss the demands on simple controls/setups for industry servo drives. Analyzing the frequency content of the motor torque command, P/PI speed control mode switching is automatically performed with only a prior knowledge of the mechanical time constant. The dynamic performance of the proposed scheme assures a desired tracking response curve with minimal oscillation and settling time over the entire set of operating conditions. For a comprehensive comparison of conventional P/PI control scheme, we carried out extensive tests on an actual servo system. Index Terms--Frequency content of motor torque, industry servo drive, proportional/proportional-integral (P/PI) speed controller, simple controls/setups.

This paper describes our research on a force ripple compensation and closed-loop position control scheme using linear hybrid stepping motors (LHSMs) with significant thrust vibrations. In order to estimate unobservable force ripple components, we propose the Jacobian linearization observer that guarantees the convergence of state estimates into true states. For the precise control of velocity and position, an input--output feedback linearization controller is derived from a nonlinear positiondependent model of the LHSM based on elaborate reluctance network analysis. In addition, we discuss the separation principle used to separate the observer design from the controller design. Common problems associated with the force ripple, such as the positioning error, mechanical stress, and acoustic noise, are efficiently handled using the proposed active damping control scheme. Experimental results show that the positioning accuracy is significantly improved through a closed-loop control while restraining the thrust ripple. Index Terms--Feedback linearization controller, Jacobian linearization observer, linear hybrid stepping motors (LHSMs), separation principle, thrust vibrations.

This paper presents a frequency-spectrum-based conditional-integration antiwindup strategy for a general proportional-integral-type controller. The ON/OFF condition of integral action is determined by a frequency-domain analysis of the actuator-input command without prior knowledge of set-point changes. The dynamic performance of the proposed scheme assures a desired tracking-response curve with minimal oscillation and settling time even with a change of operating conditions. This algorithm is useful in many high-performance induction-machine applications, as it does not allow the oscillation and overshoot of speed/torque responses. The main idea can be extended to general applications such as those involving chemical processes and industrial robots. Index Terms--Antiwindup, frequency-domain analysis, frequency-spectrum-based conditional integration, induction machine, proportional-integral (PI)-type controller.

This paper presents a new velocity estimation strategy of a nonsalient permanent-magnet synchronous motor (PMSM) drive without a high-frequency signal injection or special pulsewidth-modulation (PWM) pattern. This approach is based on the d-axis current regulator output voltage of the drive system that has the information of rotor position error. Rotor velocity can be estimated through a rotor-position-tracking proportional-integral (PI) controller that controls the position error to zero. For zero and low-speed operation, the PI controller gains of rotor position tracking controller have a variable structure according to the estimated rotor velocity. In order to boost the bandwidth of the PI controller around zero speed, a loop recovery technique is applied to the control system. The proposed method only requires the flux linkage of the permanent magnet and is insensitive to parameter estimation error and variation. The designers can easily determine the possible operating range with a desired bandwidth and perform vector control even at low speeds. The experimental results show the satisfactory operation of the proposed sensorless algorithm under rated load conditions. Index Terms--d-axis current regulator output voltage, non-salient permanent-magnet synchronous motor (PMSM) drive, rotor-position-tracking proportional-integral (PI) controller, velocity estimation strategy.

In this paper, a novel control scheme compensating for source voltage unbalance and current harmonics in series-type active power filter systems combined with shunt passive filters is proposed, which focuses on reducing the delay time effect required to generate the reference voltage. Using digital all-pass filters, the positive voltage sequence component out of the unbalanced source voltage is derived. The all-pass filter can give a desired phase shift and no magnitude reduction, unlike conventional low- or high-pass filters. Based on this positive-sequence component, the source phase angle and the reference voltage for compensation are derived. This method is easier to implement and to tune controller gains. In order to reduce the delay time effect in the voltage control loop, the reference voltage is predicted a sampling period ahead. The validity of the proposed control scheme has been verified by experimental results. Index Terms--All-pass filter, current harmonics, reference prediction, series active filter, voltage unbalance.