Visual performance maps for expanded human choice based on duty/demand cycles in hybrid vehicle’s Multi-speed hub Drive Wheels



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The Multi-speed hub Drive Wheel (MDW) for four-independent drive wheels of future electric vehicles has recently been designed by the Robotics Research Group at the University of Texas at Austin. The MDW is equipped with four distinct speeds (two electrical and two mechanical) with the aim of improving efficiency and enhancing the drivability features of the vehicle, such as acceleration and braking on the driver’s command. The MDW will have different unsprung weights in the wheels depending on a range of suggested rated power levels such as 16, 20, 24, 32, up to a maximum of 40 hp, which would then become basic choices for the customer. The overall objective of the research is to analytically develop a framework for maximizing human vehicle choice by means of visualizing human performance needs/requirements so that customer demands can be met at the time of purchase for an open architecture hybrid electric vehicle which would then be assembled on demand. In addition, based on the customer’s individual duty/demand cycle, a vehicle can then be tailored to meet the particular customer priorities such as cost and efficiency, or on the other end of the spectrum, one who is an aggressive driver. This leads to expanded human choice for future electric vehicles. To meet human needs, the appropriate MDW will be software customized to suit the customer’s demand cycle. Satisfying human needs implies responding directly to human commands / objectives over the life history of the vehicle. The decision framework developed in this study is based on detailed human needs structured by performance maps to visually guide the customer in terms of purchase / operation / maintenance / refreshment decisions. This framework augments the MDW design procedure to maximize operational efficiency and drivability for unique customer requirements. The customer-oriented duty cycle analysis based on an individual’s measured demand cycle is proposed to structure the MDW specification in terms of ten purchase criteria. Also, a comparison of two speed regimes in the MDW and Protean’s single speed in-wheel model is made and discussed in terms of efficiency. The analytical result shows that a remarkable efficiency improvement in terms of loss reduction of 1.9x for urban and 1.8x for highway duty cycles is feasible. In addition, another loss reduction of 1.2x is expected by using the reconfigurable power/electronic controllers. The present study looked at the effect of the unsprung mass on acceleration, braking, and cornering maneuvers under various road conditions (i.e., dry asphalt, wet asphalt, snowy or icy road) which was evaluated and compared based on the implementation of a nonlinear 14 DOF full-vehicle model based on ride (7 DOF), handling (3 DOF), tire (4 DOF), slip ratio, slip angle, and the tire magic formula. Based on the 14 DOF full-vehicle model, visual performance maps are generated in terms of ten operational criteria to assist the customer to visualize the vehicle’s expected performance.