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 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.