Feedback Controlled Deformable Membrane Micropumps for Fluidic Delivery Applications
thesisposted on 24.10.2013, 00:00 by Matthew L. Cantwell
In recent years, there has been a surge in studies conducted to explore a multitude of micropump technologies. Despite these efforts, gaps of knowledge still exist as to how one can accurately control pump dynamics to obtain sub-stroke volumetric deliveries. The difficulty of modeling such systems lies in the complex multiphysics interactions of these devices including electromechanical forces, solid mechanics, and fluid mechanics. To enhance the accuracy, precision, and minimum deliverable volume of a reciprocating micropump, a method of accurate armature position sensing was devised and incorporated into a prototype. The effects of implementing a closed-loop feedback system using position sensing elements such that the armature can be commanded to multiple discrete locations between the pump chamber walls was investigated. A lab prototype has been tested to demonstrate the system’s performance and its potential ability to accurately deliver sub-stroke volumes within a certain precision. A key component of any diaphragm based reciprocating pump is the design and material composition of the membrane. A thinner more elastic membrane reduces force overhead and power consumption, however, an overly elastic pump membrane results in excessive bowing reducing accuracy of the delivered fluid volume. These conflicting requirements were explored using a computer based FEM analysis and validation through laboratory testing. Reciprocating actuation solves a number of problems associated with the scaling and complexity of other actuation schemes; however, reciprocating actuation also introduces a pulsed output flow which can be detrimental to certain delivery applications. The effects of implementing a dual chamber design to mitigate pulsatile effects while eliminating the dependencies on operating frequency and backpressures was successfully explored. Magnetically actuated reciprocating micropumps suffer from lower armature forces due to a greater air gap in the magnetic circuit as compared to their rotary counterparts. FEM studies were conducted to alleviate these restrictions by introducing a twin opposed electromagnetic drive mechanism to boost armature force and increase stroke length while reducing the scale of the pump without sacrificing performance. The implemented feedback control system allows for the potential development of smaller more efficient pumps which needs to be further explored.