Simulation and Modeling of Multiple Timescale Effects from Cyclic Capacitive Loads on Thin-Film Batteries

Understanding dynamic phenomena in systems powered by thin-film batteries can be valuable for proper system modeling, design, and control. Some scenarios, such as repeated, fast dynamic loading, may create phenomena at multiple timescales. This could, for example, arise as a consequence of driving common microelectromechanical (MEMS) actuators such as piezoelectric or electrostatic actuators. One application area for these actuators is microrobotics, which is used as a motivating topic throughout this thesis. This thesis first looks experimentally at switched capacitive loads on thin-film batteries, reporting phenomena such as switching and leakage losses and parasitic capacitance. This data is used in development and implementation of calibration and validation of various modeling approaches. In this modeling, the fast nature of the switching dynamics and the slow nature of the full battery discharge creates a type of multiple timescales problem. To address this, a state projection approach is developed and presented. The initial approach uses a perturbing method to develop a transition matrix to approximate future system states based on past and current changes. This approach captures a full battery discharge with an approximate numerical cost of 6.3% compared to fully modeling all loading event. The next approach uses direct simulation information to reduce overhead in development of the transition matrix reducing numerical cost to 0.46% for the scenario presented. An error analysis was performed to understand errors in the projection process. This error analysis was used to develop an updating approach that increases projection fidelity, further reducing numerical expense to 0.14%. This reduction in numerical cost is part of allowing this approach to be used for design purposes. Finally, a set of case studies are presented highlighting two topics related to this modeling approach. First, existence of a tradeoff between depth of detail needed in modeling and the severity of the loading applied is presented. Second, example analysis is presented, demonstrating the potential of this modeling approach as a design tool. It is anticipated that through greater understanding of and an increased ability to model these types of battery loading situations, design of microsystems operating in this fashion can be aided.PHDMechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/138698/1/kbt_1.pd