Tuning and Implementation Variants of Discrete-Time ADRC

TL;DR

This paper develops and compares three discrete-time error-based ADRC implementations, bridging the gap with output-based methods and enabling practical, low-sampling-frequency control with windup protection.

Contribution

It derives three discrete-time error-based ADRC variants that closely match existing output-based controllers, facilitating easier adoption and enhanced features.

Findings

Three new discrete-time error-based ADRC implementations derived.

Reusability of transfer functions and coefficients demonstrated.

Error-based ADRC variants can now include windup protection.

Abstract

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.