First-order Disturbance Observer Research Articles

Consensus control for multi-agent systems with input constraints based on disturbance observer

In this paper, a second-order-disturbance-observer-based distributed consensus control scheme is designed for a class of nonlinear multi-agent systems with input constraints. The second-order disturbance observer tracks the disturbance better than the common first-order disturbance observer. This paper provides the analysis of two kinds of disturbance observers and then compares the results from a simulation of the two types of observers. In the controller design process, a hyperbolic tangent function is used to limit output feedback in the control law. The overall closed-loop system reaches global stability with disturbance and the tracking errors exponentially converge without disturbance. The effectiveness of the proposed control law is illustrated by simulation results.

외란 관측기와 적분기 결합형 영구자석동기전동기 강인 속도추종 알고리즘

This study proposes a robust speed tracking algorithm for a PMSM (Permanent Magnet Synchronous Motor) through the combination of disturbance observers and integral actions, considering the parameter and load torque uncertainties into accounts. The contribution of the proposed method is twofold: First, the combination of first-order disturbance observers and integral actions is applied to both the current and speed loops so as to freely assign the closed-loop performance in a low-pass filter form. Second, it is rigorously proved that the proposed method guarantees the performance recovery property and d-p axis current convergence, exponentially. The efficacy of the proposed method is verified by performing the experiments using a 1-㎾ PMSM.

Disturbance-Observer-Based Control of DFIG in Island Mode for Microgrid Applications

This paper introduces a novel control approach for Doubly-Fed Induction Generator (DFIG) operating in island mode based on the cascaded control structure with disturbance estimation. The control of the DFIG is a challenging task due to its inherent nonlinearity, fast dynamics, and unpredictable disturbances acting on the system. The proposed control structure involves a nominal controller for plant and disturbance observer (DOB) in each of the inner and outer control loop. The first-order disturbance observers are designed to estimate the time-varying and unknown disturbances. With disturbance estimation, the nominal linear dynamics is obtained in both loops. This enables the same approach for designing controllers for the inner and outer loop which significantly simplifies implementation. The controllers are designed based on the demanded error dynamics and ensure stable operation of the system, while proposed DOBs estimate disturbances including external load. Finally, the effectiveness and quality of the proposed control structure were verified through numerical simulations in terms of external disturbances rejection and closed-loop tracking performance.

Velocity Observer-Based Nonlinear Self-Tuning Position Stabilizer for Ball-Beam System Applications

This brief exhibits a nonlinear self-tuning position stabilization algorithm for ball-beam system applications under the consideration of parameter uncertainties and actuator dynamics.; there are two major contributions. First, a first-order ball velocity estimator is proposed using only the ball position feedback without dependence on system parameters. Second, the resulting nonlinear controller incorporates the time-varying feedback gain driven by the proposed self-tuner. Third, a first-order disturbance observer (DOB) is introduced to remove the high-frequency disturbance attenuation performance. The various simulation results-based-on MATLAB/Simulink validate the practical merits of the proposed scheme.

Performance‐recovery proportional‐type output‐voltage tracking algorithm of three‐phase inverter for uninterruptible power supply applications

This study suggests a proportional-type output-voltage control algorithm of a three-phase inverter for uninterruptible power supply applications with performance-recovery and offset-free properties. It makes the two contributions. The first one is to introduce first-order disturbance observers (DOBs) so as to exponentially estimate disturbances originating from model-plant mismatches. The second one is to rigorously prove that the proposed proportional-type feedback-linearising controller equipped with DOBs guarantees performance-recovery and offset-free properties. The experimental results conducted in this study, which uses a 10 kW three-phase inverter with an output capacitor, confirm that the closed-loop performance is satisfactory in both transient and steady-state periods.

Disturbance Observer-based Proportional-type Position Tracking Controller for DC Motor

This article exhibits a nonlinear proportional-type position tracking controller for DC motors, taking the parameter and load variations into account. The proposed method makes two contributions. First, a first-order disturbance observer (DOB) is devised in order to exponentially estimate the disturbances caused by parameter and load uncertainties. Secondly, a proportional-type nonlinear position tracking controller is constructed by incorporating the resulting DOB in order to ensure two useful closed-loop properties; namely, performance recovery and offset-free properties without the tracking error integral actions. The experimental result confirms the efficacy of the proposed method where a 30-W DC motor is used with an half bridge inverter.

Robust output voltage tracking algorithm for three‐phase rectifier with variable sliding surface

In this article, a variable sliding surface-based output voltage tracking controller is proposed for three-phase rectifiers driven by the pulse-width modulation technique. A systematical multi-variable approach is used for deriving the control law, considering the not only non-linearity but also parametric uncertainties. The proposed method has two features. First, the non-linear first-order disturbance observers are introduced to enable for the control law to exponentially recover the desirable tracking performance without any offset-errors in the sliding mode. Second, the self-tuning algorithm is designed to update the sliding surface to enhance the output voltage tracking performance in transient periods. The performance of the proposed method is experimentally demonstrated by using a 3-kW three-phase rectifier.

Performance recovery output voltage control algorithm for AC/DC converter

ABSTRACTThis article proposes a proportional-type cascade output voltage control algorithm equipped with disturbance observers for a three-phase AC/DC converter considering a model-plant mismatch. The advantages of the proposed method are grouped into two. First, a simple first-order disturbance observer is devised for both inner and outer-loops, not only to recover the target closed-loop performance, but also to eliminate steady-state offset errors. Second, it is thoroughly verified that the entire closed-loop system driven by the proposed proportional-type cascade controller is stable. The efficacy of the proposed method is experimentally investigated using a 3 − kW AC/DC converter.

Proportional-Type Performance Recovery DC-Link Voltage Tracking Algorithm for Permanent Magnet Synchronous Generators

This study proposes a disturbance observer-based proportional-type DC-link voltage tracking algorithm for permanent magnet synchronous generators (PMSGs). The proposed technique feedbacks the only proportional term of the tracking errors, and it contains the nominal static and dynamic feed-forward compensators coming from the first-order disturbance observers. It is rigorously proved that the proposed method ensures the performance recovery and offset-free properties without the use of the integrators of the tracking errors. A wind power generation system has been simulated to verify the efficacy of the proposed method using the PSIM (PowerSIM) software with the DLL (Dynamic Link Library) block.

Attitude stabilization of flexible spacecrafts via extended disturbance observer based controller

To achieve the high-precision attitude stabilization for the flexible spacecraft in the presence of space environmental disturbances, unmodeled dynamics, and the disturbances caused by the elastic vibration of flexible appendages, an extended disturbance observer (EDO) based controller is proposed. The proposed controller is formulated by combining EDO and a backstepping feedback controller. EDO is used to estimate the disturbance, which is modeled as an unknown high-order differentiable equation and the rth-order derivative of the disturbance is assumed to be bounded. Compared to the conventional first-order disturbance observer, the higher order EDO offers improvement in estimate accuracy, if the absolute values of poles for EDO transfer function are chosen larger than the frequency content of the disturbance. Then, the output of EDO plus the backstepping feedback controller are applied to stabilize the attitude with high precision by rejecting disturbances for the flexible spacecraft. Finally, numerical simulations have been conducted to verify the effectiveness of the proposed controller.

Dynamic Influence and Partial Compensation of Coulomb Friction in a Position- and Speed-Controlled Elastic Two-Mass System

Abstract In controlled elastic systems, such as machine tools, robots, antennae, telescopes, pointing and tracking systems, Coulomb friction decreases the dynamic performance considerably. The influence of Coulomb friction with unequal coefficients of static and dynamic friction on a position- and speed-controlled elastic two-mass system is investigated. Stable stick-slip limit cycles at various frequencies can occur. A first-order disturbance observer avoids high-frequency stick-slip completely and reduces the amplitude of low-frequency stick-slip considerably. Moreover it extends the range of application of cascade control towards “soft” mechanical systems and improves its disturbance performance substantially.