Disturbance Observer-Based PID Control System Using DNA Strand Displacement and Its Application in Exponential Gate

Synthetic control circuits have demonstrated their effectiveness in molecular process control. However, current synthetic control circuits counteract the impact of disturbances by error signals. A disturbance suppression strategy that combines a disturbance observer with a controller to achieve better disturbance suppression is presented in this paper. A disturbance observer-based PID control system (DOB-PID) is implemented for the first time using chemical reaction networks (CRNs). The controller parameters are obtained using the flow direction algorithm, which significantly reduces the parameter setting time. The DOB-PID based on CRNs achieves improved disturbance suppression without affecting the setpoint tracking characteristics. To overcome the limitation of the classic disturbance observer relying on the inverse nominal model, a modified disturbance observer-based control system (MDOB) is realized using CRNs. The MDOB-PID eliminates the need for the inverse nominal model in the modeling process. Furthermore, the MDOB-PID control system is combined with a feedforward controller, resulting in a modified disturbance observer-based feedforward control system (FDOB). This system effectively decouples the set value following and disturbance suppression characteristics, simplifying the parameter tuning process. Additionally, a FDOB-PID control system is established using DNA strand displacement. The FDOB-PID control system proposed in this paper exhibits lower overshoot and better disturbance suppression compared to existing control systems. Finally, a FDOB-PID exponential gate control system is developed to suppress leakage response in calculation process. This system ensures accurate calculation results even in the presence of a leaky response in the exponential gate.