Low-power motion control of microactuators with expensive voltage conversion and sensing

Microscale actuation technology can be an attractive component of engineered systems for a variety of reasons, including the availability of novel transduction mechanisms, small size and/or power consumption, or close integration of sensing, actuation, and processing. If a controller, whether open or closed-loop, is to be used to improve a microactuator’s performance, that controller’s design will depend on which potential advantages of the micro-scale device are to be emphasized. This often leads to considerations beyond controlling the behavior of the microactuator alone. For instance, in devices intended to minimize total power and size, both system and controller design should account for energy consumption in power electronics and sensing circuitry that might often be neglected in larger scale systems. In this talk, motion control of micro-scale actuators that behave as comparatively high-voltage, capacitive loads is studied. Under extremely strict power constraints, it may be desirable to limit control inputs to a finite number of switching opportunities within the systems electronic circuitry. Timing of these switches can be optimized to minimize energy losses, despite poor voltage conversion efficiency and fast mechanical dynamics at the micro-scale. Opportunities for minimizing total energy consumption through coordinated actuator and circuit control are explored, and methods for incorporating sensor feedback while limiting sensor power consumption are proposed. Implications for effective micro-system design to enhance closed-loop behavior are also discussed.
Kenn Oldham is an Assistant Professor of Mechanical Engineering at the University of Michigan. Dr. Oldham received a Ph.D. in Mechanical Engineering from the University of California at Berkeley in 2006 and a B.S. in Mechanical Engineering from Carnegie Mellon University in 2000. His research interests include microactuator design and fabrication, system design for controllability, ultra-low-power motion control, and robust control with nonlinear and/or uncertain dynamics. Resulting actuation, sensing, and control strategies have been applied to a variety of engineered systems, such as autonomous micro-robots, endoscopic imaging probes, and computer hard disk drives.