Digital control for embedded systems often requires low-power, hard real-time computation to satisfy high control-loop bandwidth, low latency, and low-power requirements. In particular, the emerging applications of Micro Electro-Mechanical Systems (MEMS) sensors, and their increasing integration, presents a challenging requirement to embed ultra-low power digital control architectures for these lithographically formed micro-structures. Controlling electromechanical structures of such a small scale, using naive digital controllers, can be prohibitively expensive (both in power and cost for portable or battery operated applications.) In particular, for MEMS devices, since low currents and small distances are measured, noise becomes an important factor. The main contributions can be Brownian motion noise, Johnson-Nyquist noise and shot noise, depending on the device under consideration. Conventional control design techniques can be applied to synthesize the desired controllers with the emphasis largely on filtering noise. This thesis presents control design and noise analysis of a lateral tunneling accelerometer, considering Brownian motion, Nyquist-Johnson and shot noise. It also shows the potential for control systems to be transformed into a set of co-operating parallel linear systems and demonstrate, for the first time, that this parallelization can reduce the total number of instructions executed, thereby reducing power, at the expense of modest loss in control fidelity. Since the error tolerance of linear feedback control systems is mathematically well-posed, this technique opens up a new, independent dimension for system optimization. A novel Computer-Aided Design (CAD) method is presented to evaluate control fidelity, with varying timescales on the controller, and to analyze the trade-off between performance and power dissipation. A CAD Metric for control fidelity is proposed and the potential for power savings is demonstrated using this decomposition on three different control problems.
|Advisor:||Brewer, Forrest D.|
|Commitee:||Astrom, Karl J., Butner, Steve, Hespanha, Joao P., Sherwood, Tim, Smith, Roy S.|
|School:||University of California, Santa Barbara|
|Department:||Electrical & Computer Engineering|
|School Location:||United States -- California|
|Source:||DAI-B 70/09, Dissertation Abstracts International|
|Subjects:||Electrical engineering, Computer science|
|Keywords:||Digital feedback control, Embedded systems, Low power, MEMS, Noise filtering, Power efficiency|
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