Control of Start and Stop events in a HEV
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Publisher:The Ohio State University
Series/Report no.:The Ohio State University. Department of Electrical and Computer Engineering Honors Theses; 2007
Hybrid electric vehicles are a key-piece of the future of the automotive industry. It has been demonstrated that HEVs offer benefits to fuel consumption, durability, and drivability to the end-user. The most realized version of the HEV is the belted starter/alternator coupled to the internal combustion engine. Controlling the start and stop events of this engine are paramount to increasing drivability by decreased noise, harshness and vibrations and decreasing fuel consumption. Model-based control design methods were examined in this research with the goal of creating an optimized controller for implementation on the Challenge X vehicle. The two strategies chosen are apart of two different types of control. The linear quadratic regulator is a type of state-feedback or modern control, and the lead-lag controller is a type of classical control. These two controllers were developed under a linearized model of the engine and belt dynamics which compensated for highly non-linear torque terms by assuming they are negligible or canceling their contribution through a feed-forward term. Through the addition of higher order dynamics, these controllers were verified to be robust, able to handle uncertainties and disturbances during start and stop events. The controllers were optimized under two different methods, a “static” method which involved developing a cost surface by evaluating a cost function after simulation and calculating the minimum of this surface. The second was a “dynamic” method which involved the calculation of a global minimum via two algorithms, one designed to find the local minima, and the other to define a shrinking space of minima. At the end of the optimization process, the linear quadratic regulator proved to provide the best response.