Active disturbance rejection control: Application to the temperature stabilization of ultra-stable cavities

摘要

The examples of controls in a high-precision scientific laboratory are countless and most scientific applicationsudrely on controls of the powerful proportional-integral-derivativeud(PID), first introduced by Minorsky in 1922. In recent yearsuda novel Active Disturbance Rejection Control (ADRC) has beenudproposed. The ADRC is a linear, simple, intuitive, and inherentlyudrobust form of control. It is based on a linear extended stateudobserver (LESO) that estimates and compensates the disturbanceudof the system in real time with a certain bandwidth. Theudbandwidths of the control and of the observer are the onlyudparameters needed for tuning. The design of the ADRC is modeludindependent and requires only some approximate knowledge ofudthe fast frequency response of the system. We applied the ADRCudto the stabilization of the temperature of optical ultra-stableudcavities. Such cavities are used for laser frequency stabilizationudfor high-resolution spectroscopy and in optical clocks. In our caseuda 578 nm yellow laser is locked to the cavities and it will be usedudfor the spectroscopy of ytterbium atoms. The temperature of theudcavities has to be stabilized to prevent drift in their length andudthus in the frequency of the laser. We will present the detailsudof the ADRC and show the performance of the temperatureudstabilization. The ADRC shows attractive features that motivatesudour choice: it is easy to design and to implement digitally,udinsensitive to environmental changes, and avoids typical problemsudencountered with PID like overshoots and integral windup.