Robust Flow Control of a Syringe Pump Based on Dual-Loop Disturbance Observers

Microfluidics, a field to deal with a small amount of fluid using a chip which had a lot of micro-scale channels, has applied in various fields including biology, chemistry, biomedical, and cell biology for recent few decades. One of the sub-categories of microfluidics is a droplet generation. A syringe pump is usually employed as an injection system. However, the injection system has some problems such as overshoot, steady-state error, and response delay. This paper grasped the problems of the conventional syringe pump, and then proposed a robust control method to control the flow rate precisely. Since the syringe pump includes parametric uncertainties in the system mainly due to the variation of the ball screw friction and the elasticity of the rubber, the robust control mechanism was designed with the cascade structure composed of the inner loop (i.e. disturbance observer and sliding mode control) and the outer loop (i.e. flow rate disturbance observer and 2-DOF control) against the undesired adverse effects. Finally, the proposed control scheme is evaluated through the experiment for its robustness and performance.