Abstract
The modeling and design of a hybrid bicycle with hydraulic transmission conducted at the University of Minnesota are introduced in this paper. The work is under the scope of 2013-2014 Parker Chainless Challenge with the initiative of building a chainless drivetrain for a bicycle. A hydraulic transmission, either a hydrostatic transmission (HST) or a hydro-mechanical transmission (HMT), provides a powerful solution to this competition. A pump coupled to the pedal shaft provides flow to a hydraulic motor coupled to the drive wheel shaft, constituting the simplest hydrostatic drivetrain. A hydraulic accumulator is added to provide large acceleration when needed. This turns the bicycle into a hydraulic hybrid. A multi-functional hydraulic circuit was designed to achieve different bicycle functions including human-powered mode, hydraulic-powered mode, regenerative braking and charge mode. A mathematical model was developed to help the system parameters design. A dynamic simulation model was developed to evaluate the system performance.
