The control switching adapter: a practical way to ensure bumpless switching between controllers while AO loop is engaged

Linear Quadratic Gaussian (LQG) control has gained significant ground in astronomical AO. On-line re-tuning of LQG while keeping the AO loop engaged is crucial to match changes in disturbance conditions. However, switching between AO controllers generates control "bumps" which may compromise stability and performance. Control bumps can be eliminated by adjusting the new controllers internal space to ensure maximum continuity of the control trajectory. In this work, we show how to implement this procedure in the case of a tip and tilt control loop using an additional piece of RTC software, the "control switching adapter".