Andrew A. Berlin

AirJet paper mover: an example of mesoscale MEMS

The motion of human scale objects requires MEMS-like device arrays capable of providing reasonable forces (

Market-based control of active surfaces

GTR mN) over human scale distances (10-100 cm). In principle batch fabricated values controlling air jets can satisfy these actuation requirements. By extending printed circuit board technology to include electromechanical actuation, analogous to the extension of VLSI to MEMS, the requirement of low system cost can be achieved through batch fabrication and integration of the transduction elements with computational and communication elements. In this paper we show that modulated air jets arrayed with position sensors can support and accelerate flexible media without physical contact. Precise motion control with three degrees of freedom parallel to the array, using high flow, low pressure air jet arrays is enabled using electrostatic valves having opening and closing times of approximately equals 1 ms. We present results of an exemplary platform based on printed circuit board technologies, having an array of 576 electrostatic flap valvves (1152 for double-sided actuation) and associated oriented jets, and an integrated array of 32,000 optical sensors for high resolution detection of paper edge positions. Under closed loop control edge positioning has a standard deviation of approximately equals 25 microns. Fabrication and control of the system is described.

Active control of structural buckling instability: practical trade-offs and design considerations

This paper describes a market-based approach to controlling a smart matter-based object transport system, in which an array of distributed air jets applies forces to levitate and control the motion of a planar object. In the smart matter regime, the effects of spatial and temporal variation of operating parameters among a multiplicity of sensor, actuators, and controllers make it desirable for a control strategy to exhibit a minimal dependence on system models, and to be able to arbitrate among conflicting goals. A market-based strategy is introduced that aggregates the control requirements of multiple relatively simple local controllers, each of which seeks to optimize the performance of the system within a limited spatial and temporal range. These local controllers act as the markets consumers, and two sets of distributed air jets act as the producers. Experiments are performed comparing the performance of the market-based strategy to a near-optimal model-derived benchmark, as well as to a hand-tuned PD controller. Results indicate that even though the local controllers in the market are not based on a detailed model of the system dynamics, the market is able to effectively approximate the performance of the model-based benchmark. In certain specialized cases, such as tracking a step trajectory, the performance of the market surpasses the performance of the model-based benchmark by balancing the needs of conflicting control goals. A brief overview of the active surface smart matter prototype being developed at Xerox PARC that is the motivation behind this work is also presented.

Microdevice valve structures to fluid control

This paper reports on practical tradeoffs and design considerations associated with the use of active control to dynamically stabilize structural members against linear buckling. The relationship between active control and other limitations on structural stability, such as yield strength, is examined for the case of axially loaded columns. Graphical constructs compare active control of buckling to various passive alternatives, such as changing the cross- section of a member to increase the moment of inertia, and hence the buckling load. These constructs serve to delineate the design space, showing for which geometrical regimes active control of buckling is a viable option. This delineation of the design space suggests where to look (and where not to look) to find potential applications of active buckling control. This research exposes an open question in our understanding of the effects of material yield strength on systems undergoing active stabilization. This result highlights the need to revisit certain classic experiments that form the basis for our understanding of the delineation between elastic and plastic failure modes to address the active stabilization regime.