Permanent magnet synchronous motors are extensively used in high-performance industrial applications. However, plenty of practical factors (cogging torques, load torques, friction torques, measurement error effects, dead-time effects, mechanical/electrical parameter perturbations, etc.) in the closed-loop servo system inevitably bring barriers to the high-performance speed regulation. All these factors can be regarded as generalized disturbances. Most approaches only focus on dealing with one single kind of disturbances. In practical cases, the servo system is affected by multiple sources of disturbances simultaneously, and these disturbances enter the system via different channels.To this end, this paper systematically analyzes several representative disturbances (particularly including their features and distribution in the practical servo system), and then, specifically puts forward a novel disturbance rejection framework based on the non-cascade structure. In this framework, a comprehensive disturbance observer is proposed to simultaneously and accurately estimate multiple disturbances so that the composite controller can have a corresponding part to compensate for multiple disturbances. Rigorous analysis of stability is established. Comparative experimental results demonstrate that the proposed method achieves a better speed dynamic response and a higher precision tracking performance in the presence of multiple disturbances.

The speed regulation problem of permanent magnet synchronous motor (PMSM) system is investigated under a non-cascade structure. Despite its superiority in straightforward control design, simple parameter adjustment and satisfying system dynamic performance, the structure brings two problems: the overcurrent protection and unmatched disturbance rejection. Under this structure, the current cannot any more be restricted by a reference value, and ought to be constrained within a certain range to ensure the circuit safety. Besides, unmatched distur- bances, mainly caused by external load torques, may result in undesired interference and even violate the constraint requirement due to their direct effects on the current. Toward that end, a novel overcurrent protection control algorithm is designed to tackle the current constraint and unmatched disturbances simultaneously. A disturbance observer (DOB) is utilized for unmatched disturbance estimation. A constraint coping mechanism is constructed to restrict the current. Then, a key nonlinear item is proposed by augmenting the disturbance estimation and the constrained current. Finally, a composite controller is proposed with concise structure and rigorous closed-loop stability analysis. Numerical and experimental tests further validate that the proposed control approach achieves promising speed tracking performance and guarantees the current constraint in the presence of unmatched disturbances.

The performance of active disturbance rejection control (ADRC) algorithms can be limited in practice by high-frequency measurement noise. In this article, this problem is addressed by transforming the high-gain extended state observer (ESO), which is the inherent element of ADRC, into a new cascade observer structure. Set of experiments, performed on a dc–dc buck power converter system, show that the new cascade ESO design, compared to the conventional approach, effectively suppresses the detrimental effect of sensor noise overamplification while increasing the estimation/control performance. The proposed design is also analyzed with a low-pass filter at the converter output, which is a common technique for reducing measurement noise in industrial applications.

The output voltage regulation problem of a PWM-based dc-dc buck converter under various sources of uncertainties and disturbances is investigated in this paper via an optimized active disturbance rejection control (ADRC) approach. Aiming to practical implementation, a new reduced-order generalized proportional integral (GPI) observer is first designed to estimate the lumped (possibly time-varying) disturbances within the dc-dc circuit. By integrating the disturbance estimation information raised by the reduced-order GPI observer into the output prediction, an optimized ADRC method is developed to achieve optimized tracking performance even in the presence of disturbances and uncertainties. It is shown that the proposed controller will guarantee the rigorous stability of the closed-loop system, for any bounded uncertainties of the circuit, by appropriately choosing the observer gains and the bandwidth factor. Experimental results illustrate that the proposed control solution is characterized by improved robustness performance against various disturbances and uncertainties compared with traditional ADRC and integral model predictive control (MPC) approaches.

This paper develops a methodology on sampled-data-based event-triggered active disturbance rejection control (ET-ADRC) for disturbed systems in networked environment when only using measurable outputs. By using disturbance/uncertainty estimation and attenuation technique, an event-based sampled-data composite controller is proposed together with a discrete-time extended state observer. Under the presented new framework, the newest state and disturbance estimates as well as the control signals are not transmitted via the common sensor-controller network, but instead communicated and calculated until a discrete-time event-triggering condition is violated. Compared with the periodic updates in the traditional time-triggered active disturbance rejection control, the proposed ET-ADRC scheme can remarkably reduce the communication frequency while maintaining a satisfactory closed-loop system performance. The proposed discrete-time control scheme provides the engineers with a manner of direct and easier implementation via networked digital computers. It is shown that the bounded stability of the closed-loop system can be guaranteed. Finally, an application design example of a dc-dc buck converter with experimental results is conducted to illustrate the efficiency of the proposed control scheme.