Implementation of a Hardware-in-the-Loop System Using Scale Model Hardware for Hybrid Electric Vehicle Development
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Hardware-in-a-loop (HIL) testing and simulation for components and control strategies can reduce both time and cost of development. HIL testing focuses on one component or control system rather than the entire vehicle. The rest of the system is simulated by computer systems which use real time data acquisition systems to read outputs and respond like the systems in the actual vehicle would respond. The hardware for the system is on a scaled-down level to save both time and money during testing. The system designed to simulate the REVLSE Equinox split parallel hybrid consists of five direct current (DC) permanent magnet motors. These motors are used in the system to test the controller software of the vehicle. Two of the motors act as power plants simulating the spark ignited Ethanol engine and the rear traction motor. These two motors are controlled by DC variable speed controllers. The other motors are used as generators to simulate the load from the belted alternator starter (BAS) and the road load on each axle. The motors on each axle are joined together mechanically using a belt and pulley system. The front and rear axle of the system are not connected to simulate the actual vehicle where the power plants are gear-reduced before they make contact with the road and therefore do not actually spin at the same speeds. The computer software and hardware used to run the HIL hybrid system is National Instruments LabView and CompactRIO. LabView provides an easy interface through which programs for the RIO can be written. The RIO gives the user the ability to measure the power into and out of different components in the system to measure the efficiency of the system. The ability to measure system efficiencies using different powertrain inputs and loading schemes is what makes the HIL system a valuable tool in control modeling for the Equinox. LabView and the RIO allow the user to optimize the control strategy with the two power plant inputs and the BAS to make sure the high voltage system stays charged and improve the overall efficiency of the vehicle without the actual vehicle. The HIL system allows other work to be done of the vehicle during the control development. During a constant axle speed test at 730 RPM with constant generator resistance, the front engine efficiency was 33.8%, the BAS efficiency was 53.0%, the rear load generator efficiency was 51.2% and the overall efficiency of the front axle was 24.0%. These results show that the system can simulate the powertrain of a hybrid vehicle and help create and validate a control scheme.
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