CAREER: Advanced Control Algorithms for Active Materials Actuators Used in Nanoscale Positioning

North Carolina State University, Raleigh NC

Investigators

Abstract

For manipulations at the nanoscale, highly precise positioning capability is a very basic, yet indispensable requirement. Possible applications in this area range from the assembly of molecular structures to cell manipulations and highly precise machining tasks. Currently employed devices for nanomanipulation commonly rely on the use of actuators from active materials, mostly piezoelectrics and magnetostrictives. It is only through these materials and their inherent properties that the possibility of efficient actuation in an extremely small volume is offered at all. On the other hand, these materials exhibit a highly non-linear behavior characterized by the occurrence of hysteresis loops. This greatly afflicts their control performance and limits their applicability to low bandwidth and low stroke applications under conventional (PID) feedback loops. It is of great relevance for almost every nanomanufacturing task to improve speed and efficiency while at the same time maintaining high precision. A way to treat the problem is to incorporate a model of the material behavior into the control algorithm. A novel approach in the field of shape memory alloys developed by the PI has recently established the foundation for an extremely efficient type of algorithm. This approach not only extends the range of currently employed methods to account for optimality criteria like speed of adjustment or energy consumption; it is clearly real-time capable due to its high computational speed. Based on the observation that, on the icroscale, the physical mechanisms in shape memory alloys are closely related to the ones observed in piezoelectric and magnetostrictive materials, a unified model will be developed for all three materials. Based on such a unified model, the real-time optimal control approach will be extended to account for closed-loop feedback and parameter updating, and it will be validated in a real-time hardware environment. The educational plan involves four initiatives and will promote the development of new multi-disciplinary courses from undergraduate to Ph.D. level, as well as active undergraduate student research integration. The third effort will increase the exposure of students to international issues and increase their foreign language proficiency by offering possibilities to work with one of Germany's leading institutions in nanotechnology. The final initiative is the development of web based course materials, including "virtual lab experiments" through a simulation based on JAVA versions for active materials models.