3
Systems Analysis

Systems analysis based on effective computer modeling tools is the most effective and efficient way to ensure the optimization of vehicle performance for selected vehicle configurations, as well as for studying trade-offs between candidate subsystems during the technology-selection process. Models facilitate the preparation of specifications for each candidate subsystem and support the establishment of engineering targets. The ongoing, timely verification of selected technologies and the trade-off process for defining demonstration vehicles will depend heavily on the results of systems analyses. Achieving the Goal 3 fuel-economy level of three times the current level and other critical attributes, like emissions and the cost of ownership, will require effective modeling. (See previous committee reports for further discussions of modeling vehicle systems [NRC, 1996, 1997, 1998a]).

The systems-analysis team is responsible for developing computer models of components, subsystems, and the integrated vehicle, including the environment and driver. Working with the other PNGV technical teams, the systems-analysis team's objective is to provide analytical support for defining requirements. Analytical support facilitates the evaluation of competing technologies and vehicle concepts, as well as the timely selection of overall vehicle concepts for meeting the Goal 3 objectives.

The technology-selection (the "downselect") process was completed in 1997 during the committee's fourth review. The systems-analysis team must now support the technical teams with models and analyses to ensure that performance is optimized to meet vehicle requirements. In the fourth report, the committee recommended that more rigorous cost and design-reliability models be created as



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--> 3 Systems Analysis Systems analysis based on effective computer modeling tools is the most effective and efficient way to ensure the optimization of vehicle performance for selected vehicle configurations, as well as for studying trade-offs between candidate subsystems during the technology-selection process. Models facilitate the preparation of specifications for each candidate subsystem and support the establishment of engineering targets. The ongoing, timely verification of selected technologies and the trade-off process for defining demonstration vehicles will depend heavily on the results of systems analyses. Achieving the Goal 3 fuel-economy level of three times the current level and other critical attributes, like emissions and the cost of ownership, will require effective modeling. (See previous committee reports for further discussions of modeling vehicle systems [NRC, 1996, 1997, 1998a]). The systems-analysis team is responsible for developing computer models of components, subsystems, and the integrated vehicle, including the environment and driver. Working with the other PNGV technical teams, the systems-analysis team's objective is to provide analytical support for defining requirements. Analytical support facilitates the evaluation of competing technologies and vehicle concepts, as well as the timely selection of overall vehicle concepts for meeting the Goal 3 objectives. The technology-selection (the "downselect") process was completed in 1997 during the committee's fourth review. The systems-analysis team must now support the technical teams with models and analyses to ensure that performance is optimized to meet vehicle requirements. In the fourth report, the committee recommended that more rigorous cost and design-reliability models be created as

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--> soon as possible to ensure that the concept vehicle is designed with these parameters in mind. Because vehicle cost is a major issue for the PNGV, early attention to this requirement will be critical. Program Status and Plans Analysis and Modeling In the past year, considerable effort, including a good deal of debugging and training, has been spent on the development of the PNGVSAT 2.0 vehicle model. A major seminar, attended by 55 people from the technical teams and other supporting groups, was held to familiarize and train individuals in the use of the systems model. Subsystem and component analysis and modeling support are now being provided to some technical teams, notably, as reported in the PNGV's presentations to the committee, the vehicle-engineering, fuel-cell, and EE teams. Not all of the technical teams are making use of this support, however, even though the selection of the concept-vehicle configuration and the optimization of subsystem interfaces are vital at this phase of the program. Subgroups of the committee met with the three USCAR partners individually to review the development of their proprietary concept vehicles. All three are using sophisticated, proprietary modeling and analysis to optimize vehicle performance. Government-supported technology development by suppliers, academic institutions, and government laboratories should also have access to validated PNGV models. Therefore, PNGV should find a means of validating its models in cooperation with the USCAR partners without compromising the proprietary considerations of the individual companies. Although the systems-analysis team has made provisions for incorporating cost modeling and reliability analysis into its simulation, cost modeling and reliability analyses are not being used effectively by the PNGV management or technical teams. Because vehicle affordability is a major issue, an early understanding of the key issues influencing cost is vital for overcoming cost problems and selecting alternative designs. For example, the achievable cost of the power-electronics subsystem of $15/kW (peak) must be reduced by 50 percent to meet the target. In the updated PNGV Technical Roadmap, the committee was pleased to see that Section IIIA, Vehicle Systems Overview, now includes a detailed list of vehicle requirements (PNGV, 1998). These requirements are extremely important for defining vehicle-performance targets, which should be used by all technical teams to guide their development efforts. The PNGV also provided the committee with a summary of fuel-economy projections for all candidate systems. Significant efforts are being made to develop overall control strategies (at Oakland University) and optimization software (at the University of Michigan). Both will be vital to making informed design choices and optimizing the performance of vehicle subsystems in harmony with total vehicle-performance requirements.

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--> The systems-analysis team is also evaluating several proposals for CRADAs that would provide support from five national laboratories in the areas of control strategy and verification, component/subsystem modeling, and specific technology requirements, such as thermal modeling. Plans An operating plan for fiscal year 1999 was reviewed by the committee. Key elements of the plan based on the evolution of the vehicle computer model, referred to as PNGVSAT with an associated version number (e.g., V.2.1), are summarized below: PNGVSAT V.2.1 upgrade the software to Matlab 51 upgrade the graphical user interface (GUI) (Matlab GUI) implement support contracts PNGVSAT V.2.2 develop more refined component models develop data to validate and populate models upgrade optimization and control PNGVSAT V.2.3 develop voltage bus-based software tools (equivalent circuit models, new control algorithms) conduct voltage-level studies and optimization guide program decisions and technical targets The committee believes that the systems-analysis team should concentrate on strengthening the capability of the component, subsystem, and vehicle models. Validation must be accomplished by the middle of 1999 to support the design and development of the concept vehicle. The PNGV management should encourage technical teams to make more effective use of the analysis and modeling capabilities of the system-analysis team, especially for subsystem and component development. The committee concluded that use of the systems-analysis resource varies. Some technical teams are not using it at all, while others have included specific actions in their development plans. The committee feels strongly that not enough emphasis has been placed on creating and validating a cost model. The overall vehicle cost estimates reviewed with the committee did not show the subsystems and component costs in detail. The vehicle affordability issue must be addressed now so that changes can be made, if necessary. The committee recognizes that the availability of detailed, 1   Matlab is a sophisticated, widely used engineering software package.

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--> nonproprietary cost data is a problem. Each USCAR partner has developed detailed cost data, which was apparent during proprietary reviews during the committee's fourth review in 1997 and again during the current review. As much as possible, these data should be shared with the PNGV in a form that does not compromise a company's proprietary interests. Areas of Concern The systems-analysis team is now qualified to provide analysis and modeling support to all of the technical teams. At this phase of development, all of the technical teams should be closely aligned with the systems-analysis team and using the model and associated analytical support services. The committee concluded that this is not the case. PNGV management should review the situation and encourage the effective utilization of systems analysis by all of the technical teams. Unless this is done, confidence in the optimization will be compromised. The second-generation vehicle model has already been created, but essential validation has not been done. The USCAR partners are progressing with the designs of their concept vehicles and are effectively using proprietary sophisticated vehicle, subsystem, and component models. The USCAR partners should find a means of supporting the validation of the PNGV models to guide government-sponsored R&D by national laboratories, suppliers, and academic institutions. Given the magnitude of the necessary cost reductions for affordable PNGV vehicles in keeping with the Goal 3 objectives, the committee is concerned about the lack of adequate cost models. The committee believes that cost models for use by all of the component and subsystem teams could be created without compromising individual proprietary considerations. All of the technical teams should have reliable cost models available to support their design decisions. The challenge facing the systems-analysis team is maintaining a balance between upgrading the vehicle model and providing the necessary support to the technical teams. The vehicle-engineering team and the PNGV management should review this situation regularly to ensure that a proper balance is being maintained. In the fourth report, the committee stressed that reliability models for the vehicle system would be necessary. In the past year, very little work has been done in this area. The technical teams should review their plans to ensure that reliability models are identified as line items and that responsibility for their development is assigned. Recommendations Recommendation. PNGV management should take steps to ensure the effective use of systems analysis by all technical teams and to expedite the validation of the PNGV models. The USCAR partners, which are effectively using individual

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--> proprietary models to guide the designs of their concept vehicles, should provide validation support to the PNGV models. Recommendation. Without compromising proprietary considerations, the PNGV should conduct in-depth cost analyses and use the results to guide subsystem and vehicle-affordability studies. Recommendation. The allocation of total vehicle cost among the various subsystems and components should be redone in light of development experience of the last five years to ensure that the cost targets, which have remained relatively static, are realistic.