Tuning and Implementation Variants of Discrete-Time ADRC

Practical implementations of active disturbance rejection control (ADRC) will almost always take place in discretized form. Since applications may have quite different needs regarding their discrete-time controllers, this article summarizes and extends the available set of ADRC implementations to provide a suitable variant for as many as possible use cases. In doing so, the gap between quasi-continuous and discrete-time controller tuning is being closed for applications with low sampling frequencies. The main contribution of this article is the derivation of three different discrete-time implementations of error-based ADRC. It is shown that these are almost one-to-one counterparts of existing output-based implementations, to the point where transfer functions and coefficients can be reused in unaltered form. In this way, error-based implementations become firmly rooted in the established landscape of discrete-time ADRC. Furthermore, it becomes possible to equip error-based variants with windup protection abilities known from output-based ADRC

Active Disturbance Rejection Control (ADRC) Toolbox for MATLAB/Simulink

In this study, an active disturbance rejection control (ADRC) toolbox for MATLAB/Simulink is introduced. Although ADRC has already been established as a powerful robust control framework with successful industrial implementations and strong theoretical foundations, a comprehensive tool for computer-aided design of ADRC has not been developed until now. The proposed open-source ADRC Toolbox is a response to the growing need in the scientific community and the control industry for a straightforward software application of the ADRC methodology. Its main purpose is to fill the gap between the current theories and applications of ADRC and to provide an easy-to-use solution for users in various control fields who want to employ the ADRC scheme in their applications. The ADRC Toolbox contains a single, general-purpose, drag-and-drop function block that allows the synthesis of a predefined ADRC-based strategy with minimal design effort. Additionally, its open structure allows creation of custom control solutions. The efficacy of the ADRC Toolbox is validated through both simulations and hardware experiments, which were conducted using a variety of problems known in the motion, process, and power control areas.Comment: 43 pages, 16 figures, 3 table

Robust converter-fed motor control based on active rejection of multiple disturbances

In this work, an advanced motion controller is proposed for buck converter-fed DC motor systems. The design is based on an idea of active disturbance rejection control (ADRC) with its key component being a custom observer capable of reconstructing various types of disturbances (including complex, harmonic signals). A special formulation of the proposed design allows the control action to be expressed in a concise and practically appealing form reducing its implementation requirements. The obtained experimental results show increased performance of the introduced approach over conventionally used methods in tracking precision and disturbance rejection, while keeping similar level of energy consumption. A stability analysis using theory of singular perturbation further supports the validity of proposed control approach.Comment: 30 pages, 7 figures, 1 tabl

General Error-based Active Disturbance Rejection Control for Swift Industrial Implementations

In this article, a typical 2DOF active disturbance rejection control (ADRC) design is restructured into a 1DOF form, thus making it compatible with standard industrial control function blocks and enhancing its market competitiveness. This methodology integrates the previously separated components, such as the profile generator, state observer, feedback controller, feedforward terms, and disturbance rejection, into one unified structure. In doing so, certain ADRC components can be made simpler (or even obsolete) without sacrificing the nominal control performance, which further simplifies the control synthesis and tuning. A generalized version of the error-driven design is adopted and rigorously proved here using the singular perturbation theory. The experimental verification of the utilized approach is carried out using a disturbed DC–DC buck converter

Nonlinear Extended State Observer based Active Disturbance Rejection Control of a Laser Seeker System

In this paper, the laser seeker control problem is solved in the framework of active disturbance rejection control (ADRC). The considered problem, which consists of laser seeker stabilisation and target tracking, is expressed here as a regulation problem. A nonlinear extended state observer (NESO) with varying gains is used to improve the performance of linear ESO (LESO), and thus enable better control performance in both transient period and steady-state, with lower control effort. Based on a detailed analysis of system disturbances, a special ADRC tuning method is proposed. The stability of the overall control structure is analysed with a description function method. Through comparative simulations LESO-based and the introduced NESO-based ADRC for the laser seeker system, the advantages of the proposed scheme are shown

On Vibration Suppression and Trajectory Tracking in Largely Uncertain Torsional System: An Error-based ADRC Approach

In this work, a practically relevant control problem of compensating harmonic uncertainties is tackled. The problem is formulated and solved here using an active disturbance rejection control (ADRC) methodology. A novel, custom ADRC structure is proposed that utilizes an innovative resonant extended state observer (RESO), dedicated to systems subjected to harmonic interferences. In order to make the introduced solution more industry-friendly, the entire observer-centered control topology is additionally restructured into one degree-of-freedom, compact, feedback error-based form (similar to ubiquitous in practice PID controller). Such reorganization enables a straightforward implementation and commission of the proposed technique in wide range of industrial control platforms, thus potentially increasing its outreach. In order to verify the efficiency of the introduced method, a multi-criteria experimental case study using a torsional plant is conducted in a trajectory tracking task, showing satisfactory performance in vibration suppression, without the often problem of noise amplification due to high observer/controller gains. Finally, a frequency analysis and a rigorous stability proof of the proposed control structure are given

On a Novel Tracking Differentiator Design Based on Iterative Learning in a Moving Window

Differential signals are key in control engineering as they anticipate future behavior of process variables and therefore are critical in formulating control laws such as proportional-integral-derivative (PID). The practical challenge, however, is to extract such signals from noisy measurements and this difficulty is addressed first by J. Han in the form of linear and nonlinear tracking differentiator (TD). While improvements were made, TD did not completely resolve the conflict between the noise sensitivity and the accuracy and timeliness of the differentiation. The two approaches proposed in this paper start with the basic linear TD, but apply iterative learning mechanism to the historical data in a moving window (MW), to form two new iterative learning tracking differentiators (IL-TD): one is a parallel IL-TD using an iterative ladder network structure which is implementable in analog circuits; the other a serial IL-TD which is implementable digitally on any computer platform. Both algorithms are validated in simulations which show that the proposed two IL-TDs have better tracking differentiation and de-noise performance compared to the existing linear TD