Guy Robert Babbitt

Design and control of a two-stage electro-hydraulic valve actuation system

This paper discusses the design and control of a two-stage electro-hydraulic camless Variable Valve Actuation (VVA) system designed for gasoline engines that encompass a wide rpm range. The VVA portion of each engine valve assembly in the system consists of two miniature pilot valves, a proportional valve, a compound engine valve actuator and an engine valve return mechanism. The design and proper control of these devices allow for variable valve timing, lift, duration, seating velocity and flank velocity. This flexibility enables an array of combustion strategies. Many of these strategies (such as Miller cycle operation, cylinder and valve deactivation, etc.) have been tested on fired engines that have been redesigned to incorporate the VVA system. Test results for both bench and fired engines running in a dynamometer cell are presented. These results indicate the current level of controllability of the system and the power consumed by the system in a variety of test conditions.

Microalgae growth modeling and control for a vertical flat panel photobioreactor

Microalgae have the potential to produce enough biofuels to meet the current US fuel demands. In order to achieve this potential, photobioreactors (PBRs) need to be developed that are efficient, scalable, and affordable. Models are an analytical tool that can be used to evaluate various PBRs. In this article, a dynamic model is developed for growing microalgae in a vertical flat panel photobioreactor (PBR) that may be used to measure PBR efficiency for various architectures independent of scale. The growth model is used to estimate the microalgae growth and byproduct production and consumption as a function of incident light. A feed-forward controller is developed that uses the estimated amount of CO2 consumed to determine the amount of additional CO2 to add to the system during photosynthesis. An overall controller structure that uses both feed-forward and feedback control is presented for growing microalgae inside a PBR.