Prototyping HEV Components and Control Systems with PSAT-PRO

Argonne contributes to technical target setting and evaluates new technologies in a vehicle systems context for a joint U.S. Department of Energy/auto industry program in hybrid electric vehicle (HEV) technology.

In this initiative, Argonne researchers have developed PSAT-PRO, a control code based on the PSAT (Powertrain System Analysis Toolkit) model, to support component control in the Advanced Powertrain Test Facility and produce Hardware-in-the-Loop (HIL) testing. This is a technique for performing system-level tests in a quick and cost-effective manner. PSAT-PRO was designed to control any kind of hybrid powertrain systems or subsystems.

Approach

The PSAT-PRO software is integrally linked to the PSAT software, but it is still generic enough to go from modeling to prototyping for any kind of hybrid configuration. PSAT-PRO uses control strategies developed in PSAT to control prototypes in real time. PSAT-PRO can also calibrate component models.

The test methodology is based on analyzing differences between simulation results and test data. Because the toolkit is truly integrated, researchers can go back into the PSAT simulation and modify the model until the simulation results match test data.

PSAT-PRO is being applied to all HIL activities at Argonne. It uses a real-time computer to directly control the components of a powertrain. PSAT-PRO also has the ability to emulate parts of the components using computer models. For example, in a previous experiment, PSAT-PRO controlled a dynamometer to simulate vehicle behavior. In this way, researchers can test a single component of a hybrid powertrain under the same configuration and conditions as if it were in a vehicle.

PSAT-PRO can be used in the following ways:

• Real-Time Simulation. The vehicle system controller and the HEV model are downloaded on two different electronic boards that communicate together. In this way, the vehicle model reacts in real time, exactly like an actual system. This phase can be very useful in tuning the controller.
• Hardware in the Loop. Researchers can test a hybrid powertrain component-by-component in the vehicle configuration by simulating the rest of the vehicle with the dynamometer.
• Rapid Prototyping. Researchers can integrate the system control model into the vehicle control unit. Thus, they can perform a test, analyze the results, adjust the model, and perform the same test again. The control model can be fine-tuned by taking into account results that can be provided only by test data. For instance, researchers can optimize a HEV control strategy to reduce vehicle emissions.

Accomplishments

Previously, PSAT-PRO controlled a pre-transmission parallel HEV prototype powertrain with a continuously variable transmission and a compression-ignition, direct-injection engine. Using PSAT-PRO, researchers controlled this HEV powertrain on a test stand by emulating vehicle and battery behavior. The analysis identified hybridization emissions benefits and showed a trade-off between fuel economy and nitrogen oxide emissions. The results demonstrated and quantified the impact of control strategy on fuel consumption and emissions for diesel hybrid vehicles.

Argonne staff also used the PSAT-PRO control system to perform HIL testing with a series HEV using four motor-wheels. The goal was to control and optimize a variable-gap motor in an HEV application. PSAT-PRO allowed the staff to perform HIL control by interfacing the simulated vehicle and the motor/dynamometer test cell. The measured torque of the motor was used to propel the simulated vehicle model. The dynamometer speed was controlled to replicate realistic motor speed calculated with the simulated vehicle. The controlled powertrain system was actually made of both a real motor and a simulated vehicle. Therefore, the motor was being tested at a vehicle level but with the convenience of a test stand.

PSAT-PRO was also used for two DOE-funded technology validation projects. An INTegrated Electric Traction System (INTETS) and a lithium-ion battery were evaluated in a mule vehicle using PSAT-PRO to emulate a fuel cell.

Current Work

PSAT-PRO is now being used for HIL projects evaluating hydrogen as a fuel for use in internal combustion engine HEV applications. For this initiative, Argonne developed the Advanced Powertrain Research Platform, a powertrain “buck” with custom instrumentation and ”virtual inertia” scalable electric machine controlled by PSAT-PRO to provide the flexibility to vary the level of hybridization.

September 2004