Design and construction of a hydrostatic dynamometer for testing a hydraulic hybrid vehicle.

Abstract

A hydrostatic dynamometer has been constructed to test a hydraulic hybrid passenger vehicle. Hybrid vehicles reduce their fuel consumption by capturing energy normally lost during braking and reusing it during acceleration in addition to managing the engine to enable it to run at a higher efficiency operating point. The dynamometer is designed to test a particular hybrid vehicle which stores and transmits energy hydraulically. Measurement of fuel consumption while the vehicle completes standard drive cycles is necessary to refine and validate the performance and efficiency of the vehicle. The dynamometer provides repeatable, convenient, inexpensive, safe, and flexible indoor testing for the vehicle. The dynamometer connects directly to the output shaft of the vehicle's transmission. It is mounted on a bedplate installed behind the vehicle. The dynamometer's hydraulic pump loads or motors the vehicle to simulate driving. It can be controlled either manually or automatically. Automatic controls allow the dynamometer to calculate and apply the appropriate load based on vehicle speed. MATLAB and Simulink simulations aided the design of the dynamometer. A MATLAB simulation of the vehicle determined torque and speed requirements for standard drive cycles. Another MATLAB simulation calculated pressures, flow rates, and energy storage requirements on the dynamometer to size components. A Simulink simulation aided controls development. The dynamometer has demonstrated open and closed loop performance with and without load. It has demonstrated fast torque tracking. However, vehicle reliability issues have prevented drive cycle tests from being completed.