In this paper, a two-degrees-of-freedom controller is proposed for robust speed regulation in permanent magnet synchronous motors (PMSM). Our proposal constitutes an extension of a control scheme previously introduced in the literature for permanent magnet brushed dc motors to the case of PMSM. We formally prove global exponential stability of the desired equilibrium point, and we take into account the nonlinear motor electric dynamics during the stability proof. Several experiments are presented, which verify that the closed-loop control system is robust with respect to parameter uncertainties and outstanding torque disturbance rejection is performed. These results are compared to those obtained with a standard proportional-integral speed control scheme. We conclude that good performance, simplicity, and easy controller commissioning in practice are significant advantages of our proposal, which render it suitable for the motor drive community.

Robust Speed Control of Permanent Magnet Synchronous Motors Using Two-Degrees-of-Freedom Control

This paper presents a speed controller using a fuzzy-logic controller (FLC) for indirect field-oriented control (IFOC) of induction motor (IM) drives fed by a four-switch three-phase (FSTP) inverter. In the proposed approach, the IM drive system is fed by an FSTP inverter instead of the traditional six-switch three-phase (SSTP) inverter for cost-effective low-power applications. The proposed FLC improves dynamic responses, and it is also designed with reduced computation burden. The complete IFOC scheme incorporating the FLC for IM drives fed by the proposed FSTP inverter is built in MATLAB/Simulink, and it is also experimentally implemented in real time using a DSP-DS1103 control board for a prototype 1.1-kW IM. The dynamic performance, robustness, and insensitivity of the proposed FLC with the FSTP inverter-fed IM drive is examined and compared to a traditional proportional-integral (PI) controller under speed tracking, load disturbances, and parameters variation, particularly at low speeds. It is found that the proposed FLC is more robust than the PI controller under load disturbances, and parameters variation. Moreover, the proposed FSTP IM drive is comparable with a traditional SSTP IM drive, considering its good dynamic performance, cost reduction, and low total harmonic distortion (THD).

A Performance Investigation of a Four-Switch Three-Phase Inverter-Fed IM Drives at Low Speeds Using Fuzzy Logic and PI Controllers

Speed loop is the key factor affecting the performance of induction machine (IM) drives. Conventionally, the proportional integral (PI) controller is applied for its simple implementation and static-errorless; however, its performance degrades apparently under sudden external load torque changes. To address this problem, this paper presents a nonlinear control strategy, combining the conventional PI control with a high-order fast terminal sliding-mode (HOFTSM) load torque observer. The external load torque is estimated online by the proposed HOFTSM observer, and then the estimated torque is used as feed-forward compensation for the PI controller. Moreover, the designed HOFTSM observer shows superiorities in fast convergence rate and chattering elimination. Comparison experiments show that the load torque rejection of the IM speed loop is significantly enhanced by using the proposed approach.

Antidisturbance Speed Control for Induction Machine Drives Using High-Order Fast Terminal Sliding-Mode Load Torque Observer

This paper aims to present a solution for torsional vibration suppression and shaft torque limitation simultaneously in servo system with backlash The existence of backlash, which would make conventional notch filter invalid, will aggravate the mechanical vibration and bring the risk of unsafety to the system In order to solve that problem, a novel shaft torque compensator is proposed, which would make the system similar to a rigid system with one inertia What is more, this compensator can limit shaft torque as expected, making the system relatively safe under any situation with different load inertias and torques The limiting control is based on the adaptive online identification of load inertia in order to improve robustness of the system and ensure not only the accuracy, but also the arbitrariness of shaft torque limit Simulation and experimental results are presented to illustrate the favorable behavior of the drive with the robust shaft torque compensator

Shaft Torque Limiting Control Using Shaft Torque Compensator for Two-Inertia Elastic System With Backlash

Effective identification of the load torque is one of the key aspects in improving the performance of servo drive systems against load disturbances. Sliding mode variable structure control has become a popular method in the development of a load torque identification (LTID) algorithm due to its parameter insensitivity and easy realization features. However, existing LTID sliding mode observers (SMO) with conventional structure have the disadvantages of high-frequency chattering and poor estimation accuracy, which limit its application in high-performance servo systems. In this paper, the mathematical model of the conventional LTID-SMO is deduced and analyzed. A new LTID-SMO is proposed by replacing the sign function with a saturation function and an additional feedback loop in the load torque observer. The effectiveness of the proposed observer is verified by various experiments. The results show that compared to conventional load torque observer, the proposed observer can identify the load torque with higher accuracy and faster response in different operational conditions.

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Corrections to “A New Load Torque Identification Sliding Mode Observer for Permanent Magnet Synchronous Machine Drive System”

This paper presents a novel on-line inertia identification method with a load torque observer to optimize the speed loop PID parameters of a servo system. The proposed inertia identification algorithm in this paper adopts the fixed-order recursive empirical frequency-domain optimal parameter estimation to improve the speed loop performance. A load torque observer is employed in order to obtain a more precise value of inertia. Then, the method of speed loop PI parameters optimization with the identified inertia and load torque is deduced in frequency domain. Compared with the recursive least square algorithm, the effectiveness of the proposed method is demonstrated by the simulation and experimental results.

On-line Inertia Identification Algorithm for PI Parameters Optimization in Speed Loop

The invention relates to a rotational inertia on-line identification method for an alternating current (AC) permanent magnet synchronous motor servo system and belongs to the technical field of rotational inertia identification for motors. The method aims to solve the problems that an on-line inertia identification method based on the traditional least square method is high in requirements for storage space and arithmetic speed of digital processing chips. The method adopts a load torque identification part to identify a constant load disturbance torque value TL; a system dynamic state judging part is adopted for judging whether rotation speed of a motor is at a dynamic change stage, and when the rotation speed of the motor is at the dynamic change stage and the rate of change of the rotation speed of the motor is higher than a critical change rate for identification of rotational inertia of the motor, a rotational inertia estimation value is obtained through calculation by utilization of a least square estimation method based on recursion; and when the rotational inertia on-line identification process meets requirements of a preset output rotational inertia estimation value and meets a requirement for precision, the rotational inertia estimation value is output and the rotational inertia on-line identification process is completed. The method is used for rotational inertia on-line identification for the motor servo system.

Liu Zijian

Papers

On-line Inertia Identification Algorithm for PI Parameters Optimization in Speed Loop

Rotational inertia on-line identification method for alternating current (AC) permanent magnet synchronous motor servo system